WO2026000399A1 - Battery and electrical apparatus - Google Patents

Abstract

A battery (2) and an electrical apparatus. The battery (2) comprises a plurality of battery cells (10) and a first busbar component (30a). The plurality of battery cells (10) are arranged along the thickness direction of each battery cell (10), and the battery cells (10) each comprise a housing (12) and an electrode assembly (11) accommodated in the housing. The expansion pressure of each battery cell (10) in the thickness direction is 0.5 MPa to 2.4 MPa. The first busbar component (30a) is electrically connected to at least two battery cells (10) arranged in the thickness direction, and the first busbar component (30a) is of a multi-layer structure. The electrode assembly comprises a positive electrode plate (111), a negative electrode plate (112), and a separator (113) located between the positive electrode plate (111) and the negative electrode plate (112). The positive electrode plate (111) comprises a positive electrode current collector (1111) and a positive electrode film layer (1112) provided on at least one side of the positive electrode current collector (1111). The positive electrode film layer (1112) comprises a positive electrode active material. The positive electrode active material comprises a lithium-containing phosphate having an olivine structure. The negative electrode plate (112) comprises a negative electrode current collector (1121) and a negative electrode film layer (1122) provided on at least one side of the negative electrode current collector (1121). The negative electrode film layer (1122) comprises a negative electrode active material. The negative electrode active material comprises a carbon-based material.

Description

Batteries and electrical devices Technical Field

This application relates to the field of battery technology, and more specifically, to a battery and an electrical device.

Background Technology

Batteries are widely used in electronic devices such as mobile phones, laptops, electric vehicles, electric cars, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes, and power tools, etc.

In the development of battery technology, improving battery reliability is one of the research directions.

Summary of the Invention

This application provides a battery and an electrical device that can improve the reliability of the battery.

In a first aspect, embodiments of this application provide a battery comprising a plurality of battery cells and a first busbar. The plurality of battery cells are arranged along the thickness direction of the battery cells, and each battery cell includes a casing and an electrode assembly housed within the casing. The expansion pressure of the battery cells in the thickness direction is 0.5 MPa-2.4 MPa. The first busbar electrically connects at least two battery cells arranged along the thickness direction, and the first busbar has a multilayer structure. The electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a separator between the positive and negative electrode sheets. The positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector. The positive electrode film layer includes a positive active material, which includes a lithium phosphate with an olivine structure. The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector. The negative electrode film layer includes a negative active material, which includes a carbon-based material.

The expansion pressure of a single battery cell is related to the density of the electrode assembly. Embodiments of this application allow the battery cell to have an expansion pressure greater than or equal to 0.5 MPa in the thickness direction, thereby improving the density of the electrode assembly and increasing the energy density of the battery cell. An expansion pressure of less than or equal to 2.4 MPa in the thickness direction can limit the deformation of the electrode assembly during cycling, reducing the risk of wrinkling and deformation of the separator and the risk of increased local spacing between the positive and negative electrodes, thus reducing polarization and improving the cycle performance of the battery cell. The first busbar has a multi-layer structure, and each layer of the first busbar can transmit current. This allows the first busbar to have a high current-carrying area, thereby reducing heat generation in the first busbar and improving the battery's fast-charging capability and reliability.

Provided the flow area meets the requirements, setting the first busbar component as a multi-layer structure can reduce the thickness of each layer. During cycling, the battery cell expands, stretching the layer of the first busbar component connected to the battery cell. The first layer of the first busbar component has a small thickness, making it easily deformable to accommodate the expansion and deformation of the battery cell. This reduces the risk of the connection between the battery cell and the first busbar component cracking when the expansion pressure of the battery cell 10 is 0.5MPa-2.4MPa, thus improving battery reliability.

The first busbar component, with its multi-layer structure, can accommodate the expansion of individual battery cells while also providing a complete first busbar. The current carrying capacity and deformability of the components are improved, thereby enhancing the reliability and fast charging capability of the battery.

In some embodiments, the first busbar component includes a first busbar layer and a second busbar layer stacked and connected, wherein the first busbar layer connects at least two battery cells arranged along the thickness direction.

Both the first and second busbars can transmit current, allowing the first busbar component to have a larger current-carrying area. This reduces heat generation in the first busbar component and improves the battery's fast-charging capability and reliability. Provided the current-carrying area requirement is met, designing the first busbar component as a double-layer structure reduces the thickness requirement for the first busbar layer. During cycling, individual battery cells expand, stretching the first busbar layer. The first busbar layer, with its smaller thickness, is easily deformable to accommodate the deformation of the battery cells, reducing the risk of tearing at the connection between the battery cells and the first busbar layer, thus improving battery reliability.

In some embodiments, the battery cell includes electrode terminals disposed on the housing, the electrode terminals being electrically connected to an electrode assembly. A portion of the first busbar that does not overlap with the second busbar is connected to the electrode terminals. The second busbar can bypass the connection point between the first busbar and the electrode terminals, thereby reducing the impact of the second busbar on the connection point when the battery cell expands, lowering the risk of the connection point being torn, and improving battery reliability.

In some embodiments, the first busbar is welded to the electrode terminal, and the welding area between the first busbar and the electrode terminal is greater than or equal to 60 ^mm² . The large current-carrying area between the first busbar and the electrode terminal reduces heat generation at the welding point, lowers the temperature rise of the first busbar during fast charging, and improves the battery's fast charging capability.

In some embodiments, the first bus component includes at least one bend connecting a first bus layer and a second bus layer. The bend can connect the first bus layer and the second bus layer and transmit current between the first bus layer and the second bus layer, thereby improving the current carrying capacity of the first bus component.

In some embodiments, the first busbar includes a first busbar portion, a second busbar portion, and a first buffer portion. The first busbar portion and the second busbar portion are disposed along the thickness direction and connected to different battery cells. The first buffer portion connects the first busbar portion and the second busbar portion. At least one of the first busbar portion and the second busbar portion is connected to a bending portion. During the cycling process of the battery cells, the battery cells expand and exert tensile force on the first busbar layer; the first buffer portion can release stress through deformation, thereby reducing the stress at the connection between the first busbar portion and the battery cell, as well as the stress at the connection between the second busbar portion and the battery cell, reducing the risk of connection failure between the first busbar layer and the battery cell.

In some embodiments, the bent portion is disposed away from the first buffer portion. The bent portion is not directly connected to the first buffer portion, thereby reducing the impact of the bent portion on the deformation of the first buffer portion and reducing the difficulty of deforming the first buffer portion.

In some embodiments, the second bus layer includes a first stacked portion, a second stacked portion, and a second buffer portion. The first stacked portion is stacked with the first bus layer and connected by at least one bend. The second stacked portion is stacked with the second bus layer and connected by at least one bend. The second buffer portion connects the first stacked portion and the second stacked portion. In the stacking direction of the first bus layer and the second bus layer, the second buffer portion at least partially overlaps with the first buffer portion.

During the cycling process of a single battery cell, the cell expands and exerts tension on the first busbar layer. Both the first and second buffer sections can release stress through deformation, thereby reducing the risk of connection failure between the first busbar layer and the battery cell. The second buffer section at least partially overlaps with the first buffer section, which brings their deformation areas closer together, thereby reducing the risk of interference between the first and second buffer sections and other parts during deformation.

In some embodiments, the second buffer portion and the first buffer portion are fitted together, which can save space and improve overcurrent. ability.

In some embodiments, the battery further includes at least one second busbar component, which is a single-layer structure connecting at least two battery cells. The thickness of the second busbar component is greater than the thickness of the first busbar layer, and the thickness of the second busbar component is greater than the thickness of the second busbar layer. In the battery, the expansion amount of battery cells at different locations may vary. For battery cells with smaller expansion amounts, a second busbar component with a single-layer structure can be used; compared to the first busbar component, the second busbar component has a simpler structure, is easier to manufacture, and can save costs. The thickness of the second busbar component, being greater than the thickness of both the first and second busbar layers, ensures that its current-carrying capacity meets requirements.

In some embodiments, the sum of the thickness of the first bus layer and the thickness of the second bus layer is equal to the thickness of the second bus component, which can reduce the difference in overcurrent capacity between the first bus component and the second bus component and improve current consistency.

In some embodiments, among a plurality of battery cells, the outermost battery cell located along the thickness direction is connected to the first busbar. During charging, the expansion of the multiple battery cells may be superimposed in the thickness direction, which causes a larger displacement of the outermost battery cell in the thickness direction; using a first busbar with a multi-layer structure to connect the outermost battery cell can reduce the risk of connection failure between the first busbar and the battery cell.

In some embodiments, the thickness of the first busbar is 1mm-2.5mm, and can be selected as 1.2mm-1.8mm. The embodiments of this application select the thickness of the first busbar based on the expansion pressure of the battery cell, which can, to a certain extent, balance the current-carrying capacity and deformability of the first busbar, thereby improving the battery's fast-charging capability and reliability.

In some embodiments, the thickness of the second busbar is 1mm-2.5mm, optionally 1.2mm-1.8mm.

In some embodiments, the volumetric energy density of the battery cell is 390Wh/L-450Wh/L, and the thickness of the first busbar is less than or equal to 2.5mm; or, the volumetric energy density of the battery cell is 450Wh/L-480Wh/L, and the thickness of the first busbar is less than or equal to 2.2mm.

The expansion of a single battery cell is related to its volumetric energy density. This application designs the thickness of the first busbar layer based on the volumetric energy density of the battery cell, thereby balancing the current carrying capacity and deformability of the first busbar layer to a certain extent, thus improving the battery's fast charging capability and reliability.

In some embodiments, the negative electrode active material further includes a silicon-based material. The silicon content in the negative electrode active material is 1%-6% by mass; the thickness of the first busbar layer is 1.2mm-2.2mm, and the thickness of the second busbar layer is 1.2mm-2.2mm.

By introducing silicon-based materials, the capacity of the negative electrode can be increased, thereby improving the energy density of the battery cell. Introducing silicon-based materials also increases the expansion of the negative electrode during cycling. By designing the thickness of the first and second busbars in conjunction with the silicon content, the risk of connection failure between the first busbar and the battery cell due to the introduction of silicon-based materials can be reduced, while still meeting the current-carrying capacity requirements of the first busbar component.

In some embodiments, the first busbar layer includes a first busbar portion, a second busbar portion, and a first buffer portion connecting the first busbar portion and the second busbar portion. The first busbar portion and the second busbar portion are disposed along the thickness direction and connected to different battery cells. In the stacking direction of the first busbar layer and the second busbar layer, the first buffer portion protrudes from the first busbar portion and the second busbar portion. The first busbar layer has a recess at a position corresponding to the first buffer portion. By providing the recess, the strength of the first buffer portion can be reduced, facilitating the deformation of the first buffer portion when the battery cell expands.

In some embodiments, the volumetric energy density of the battery cell is 390Wh/L-450Wh/L, and the depth of the recess is 1.2mm-2.5mm; or, the volumetric energy density of the battery cell is 450Wh/L-480Wh/L, and the depth of the recess is... 1mm-2.2mm.

The expansion of a battery cell is related to its volumetric energy density. This application designs the depth of the recess based on the volumetric energy density of the battery cell, thereby taking into account the overcurrent capacity and deformability of the first buffer section to a certain extent, thereby improving the battery's fast charging capability and reliability.

In some embodiments, the electrode assembly includes two first surfaces and two second surfaces, the two first surfaces being disposed opposite each other along the thickness direction, and the two second surfaces being disposed opposite each other along a direction perpendicular to the thickness direction, the second surfaces connecting the two first surfaces. The area of the first surfaces is larger than the area of the second surfaces.

In some embodiments, the expansion pressure of the battery cell in the thickness direction is 1.5 MPa-2.0 MPa. Limiting the expansion pressure of the battery cell in the thickness direction within the above range can reduce the pulling force of the battery cell on the first busbar component during battery cell cycling, reduce the risk of connection failure between the battery cell and the first busbar component, and improve battery reliability.

In some embodiments, the single-sided coating weight of the negative electrode film is from 90 mg/1540 ^mm² to 170 mg/1540 ^mm² , and optionally from 110 mg/1540 ^mm² to 150 mg/1540 ^mm² . The single-sided coating weight of the negative electrode film is related to the expansion of the negative electrode film. Limiting the single-sided coating weight of the negative electrode film to the above range can, to a certain extent, balance the energy density and expansion pressure of the battery cell, reduce the deformation of the battery cell, and reduce the risk of connection failure between the battery cell and the first busbar component.

In some embodiments, the compaction density of the negative electrode film at 100% SOC of the battery cell is 1.15 g/ ^cm³ to 1.36 g/ ^cm³ , optionally 1.25 g/ ^cm³ to 1.36 g/ ^cm³ . The compaction density of the negative electrode film is related to the expansion of the battery cell at 100% SOC. Limiting the compaction density of the negative electrode film to 1.15 g/ ^cm³ to 1.36 g/ ^cm³ can, to a certain extent, balance the energy density and expansion pressure of the battery cell, reduce battery cell deformation, and lower the risk of connection failure between the battery cell and the first busbar component.

When the compaction density of the negative electrode film is within the above range, it is beneficial to improve the energy density of the battery cell; and because the negative electrode active material in the negative electrode film is packed more tightly, the contact resistance between particles is smaller, which can reduce the resistance of the negative electrode sheet, thereby reducing heat generation.

When the compaction density of the negative electrode film is within the above range, the fast charging capability of the battery cell can be improved. A lower compaction density of the negative electrode film can increase the porosity of the negative electrode sheet, slow down the expansion of the negative electrode sheet, and reduce the expansion pressure of the battery cell.

In some embodiments, the porosity of the negative electrode is 27%-40%. A porosity greater than or equal to 27% provides space for impurities generated by side reactions, slows down the expansion of the negative electrode, reduces the expansion pressure of the battery cell, decreases the deformation of the battery cell, improves the cycle performance of the battery cell, and reduces the risk of connection failure between the battery cell and the first busbar component. A porosity less than or equal to 40% can balance the energy density of the battery cell.

In some embodiments, the carbon-based material includes at least one of artificial graphite and natural graphite. Artificial and natural graphite have good electrical conductivity, which can reduce heat generation of the negative electrode during charging and improve the fast-charging performance of the battery cell.

In some embodiments, the negative electrode active material further includes a silicon-based material, wherein the silicon element in the silicon-based material has a mass content of 0.3% to 10%, optionally 1% to 6%.

Introducing silicon-based materials into the negative electrode can both increase capacity and increase the expansion of the negative electrode. Therefore, [the following is a possible interpretation:] Limiting the mass content of silicon in the negative electrode active material to the above range can, to a certain extent, balance the energy density and expansion of the battery cell, reduce the deformation of the battery cell, improve the cycle performance of the battery cell, and reduce the risk of failure of the connection between the battery cell and the first busbar component.

In some embodiments, the silicon-based material includes at least one of silicon oxides and silicon-carbon composites.

In some embodiments, the negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer, with the second negative electrode film layer disposed between the first negative electrode film layer and the negative electrode current collector. The negative electrode active material includes a first negative electrode active material disposed in the first negative electrode film layer and a second negative electrode active material disposed in the second negative electrode film layer. The first negative electrode active material includes artificial graphite, and the second negative electrode active material includes one or more of artificial graphite, natural graphite, and silicon-based materials. The first and second negative electrode film layers can be differentiated to balance the expansion and capacity of the negative electrode film layer to a certain extent. Double-layer coating can create porosity differences in the negative electrode film layer, reduce ion transport tortuosity, reduce side reactions, and improve the fast-charging performance of the battery cell.

In some embodiments, the thickness ratio of the first negative electrode film layer to the second negative electrode film layer is 3:7 to 7:3, and optionally 4:6 to 6:4. By adjusting the thickness ratio of the first negative electrode film layer to the second negative electrode film layer, the gradient porosity difference between the upper and lower layers can be further increased, the lithium-ion transport tortuosity can be reduced, and the fast charging capability of the battery cell can be improved.

In some embodiments, the thickness of the first negative electrode film is less than or equal to the thickness of the second negative electrode film, which can further improve the fast charging capability of the battery cell.

In some embodiments, the volume average particle size Dv50 of the first negative electrode active material is less than or equal to the volume average particle size Dv50 of the second negative electrode active material.

The difference in particle size between the first and second negative electrode active materials can improve the fast charging performance of the battery cell. During fast charging, the overpotential of the first negative electrode film is usually high, and the bottleneck of fast charging mainly lies in the first negative electrode film. However, in the embodiments of this application, the particle size of the first negative electrode active material is relatively small, which can shorten the solid-phase transport path of ions, improve fast charging performance, and improve the problem of ion deposition on the surface of the negative electrode sheet. The particle size of the second negative electrode active material is relatively large, which can form larger pores in the second negative electrode film. During charging, the pores can absorb expansion, reduce the expansion of the negative electrode film, reduce the force exerted by the battery cell on the first busbar component, and reduce the risk of connection failure between the battery cell and the first busbar component.

In some embodiments, the volume average particle size Dv50 of the first negative electrode active material is 7.8 μm-14.3 μm, and optionally 7.8 μm-11.3 μm.

The volume average particle size Dv50 of the first negative electrode active material is set within the above-mentioned range. On the one hand, this can shorten the solid-phase transport path of lithium ions and improve fast charging performance. On the other hand, the material is less prone to agglomeration during the preparation process, which can improve the stability of the material. Furthermore, the first negative electrode active material within the above-mentioned volume average particle size range can cooperate with the second negative electrode active material, which is conducive to constructing a gradient porosity difference between the first negative electrode film and the second negative electrode film, reducing the tortuosity of lithium ion transport, and improving the fast charging performance of the battery cell.

In some embodiments, the volume average particle size Dv50 of the second negative electrode active material is 9.5 μm-18.5 μm, optionally 9.5 μm-14.6 μm. Setting the volume average particle size Dv of the second negative electrode active material within the above range can enrich the porosity of the second negative electrode film, which is beneficial to improving the fast charging capability of the battery cell and reducing the expansion of the negative electrode film during charging.

In some embodiments, the specific surface area of the negative electrode active material is 0.5 ^m² /g to 3 ^m² /g, optionally 0.6 ^m² /g to ^{1.2 m²} /g. Limiting the specific surface area of the negative electrode active material to greater than or equal to 0.5 ^m² /g can improve the fast charging speed of individual battery cells. The ability to charge quickly; limiting the specific surface area of the negative electrode active material to less than or equal to 3 ^m² /g can reduce side reactions of battery cells during storage and reduce expansion pressure.

In some embodiments, the single-sided coating weight of the positive electrode film is 200 mg/1540 ^mm² - 370 mg/1540 ^mm² ; optionally, it is 240 mg/1540 ^mm² to 330 mg/1540 ^mm² . Setting the single-sided coating weight of the positive electrode film within the above range can limit the heat generation per unit area of the positive electrode sheet, while also improving the energy density and charging rate performance of the battery cell.

In some embodiments, the compaction density of the positive electrode film at 100% SOC of the battery cell is 2.50 g/ ^cm³ to 2.80 g/ ^cm³ ; optionally, it is 2.55 g/ ^cm³ to 2.70 g/ ^cm³ . A compaction density within this range is beneficial for increasing the energy density of the battery cell; and because the positive electrode active material in the positive electrode film is densely packed, the contact resistance between particles is low, which further reduces the resistance of the positive electrode sheet, thereby reducing heat generation during fast charging.

In some embodiments, the porosity of the positive electrode is 25%-32%. A porosity greater than or equal to 25% provides space for impurities generated by side reactions, reducing the expansion pressure of the battery cell, decreasing cell deformation, improving cycle performance, and lowering the risk of connection failure between the battery cell and the busbar. A porosity less than or equal to 32% can, to some extent, maintain the energy density of the battery cell.

In some embodiments, the thickness of the positive electrode sheet is 0.13 mm to 0.2 mm. Using a positive electrode sheet with a smaller thickness can shorten the ion migration path, increase the ion migration rate, reduce the heat generation of the battery cell, and improve the fast charging performance of the battery cell.

In some embodiments, the ratio of the thickness of the positive current collector to the thickness of the positive electrode film is 0.05-0.3. Limiting the ratio of the positive current collector thickness to the positive electrode film thickness to greater than or equal to 0.05 can improve the current-carrying capacity of the positive current collector, reduce the temperature rise of the positive electrode sheet, and improve the fast-charging performance of the battery cell. Limiting the ratio of the positive current collector thickness to the positive electrode film thickness to less than or equal to 0.3 can reduce the capacity loss of the positive electrode sheet. The embodiments of this application limit the ratio of the positive current collector thickness to the positive electrode film thickness within the above range, which can, to a certain extent, balance the fast-charging capability and energy density of the battery cell.

In some embodiments, the volume average particle size of the positive electrode active material satisfies 1 μm ≤ Dv50 ≤ 2 μm and 0.4 μm ≤ Dv10 ≤ 0.7 μm. The relatively small particle size of the positive electrode active material results in a shorter lithium ion insertion/extraction pathway and less heat generation. Furthermore, the particle size of the aforementioned positive electrode active material is not too small, which reduces agglomeration during processing and preparation, thus ensuring stable performance of the positive electrode active material.

In some embodiments, a battery cell includes an electrolyte contained within a housing.

In some embodiments, the electrolyte has a conductivity of 15 mS/cm to 20 mS/cm at room temperature. When the conductivity of the electrolyte is within this range, the ion migration rate in the electrolyte is high, thereby further reducing the internal resistance of the battery cell, reducing heat generation, and improving the fast charging performance of the battery cell.

In some embodiments, the electrolyte includes an organic solvent, which may include one or more of carbonate solvents and carboxylic acid ester solvents. The use of organic solvents can improve the electrolyte conductivity and reduce viscosity, thereby improving the battery's fast-charging performance.

In some embodiments, carbonate solvents include one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

In some embodiments, the carboxylic acid ester comprises _R1 -COO- _R2 , where _R1 and _R2 each independently comprise an alkyl group having 1-5 carbon atoms or a haloalkyl group having 1-5 carbon atoms. The above-mentioned chain-like carboxylic acid ester solvents have high conductivity, which is advantageous. Improve the fast charging capability of individual battery cells.

In some embodiments, the electrolyte comprises a lithium salt, including lithium bis(fluorosulfonyl)imide (LiFSI) and lithium hexafluorophosphate (LiPF6 ₎ , wherein the molar concentration of lithium bis(fluorosulfonyl)imide (LiFSI) is from 0.2 mol/L to 0.5 mol/L, and the molar concentration of lithium hexafluorophosphate (LiPF6 ₎ is from 0.5 mol/L to 1.0 mol/L.

In some embodiments, the electrolyte density ρ at room temperature satisfies: 1.05 g/mL ≤ ρ ≤ 1.35 g/mL. When the electrolyte density ρ is within the above range, the migration rate of lithium ions in the electrolyte is higher, which can further reduce the internal resistance of the battery cell, thereby reducing heat generation and improving the fast charging performance of the battery cell.

In some embodiments, the dimension of the electrode assembly along the thickness direction is T, the thickness of the single-layer negative electrode sheet is T1, and the number of layers of the negative electrode sheet stacked in the thickness direction is N.

T, T1, and N satisfy: 0.3≤(N×T1)/T≤0.5.

During the cycling process of a battery cell, the negative electrode sheet will increase in thickness due to irreversible side reactions, thus causing the battery cell to expand. Limiting (N×T1)/T within the above range can reduce the expansion of the battery cell and reduce the risk of failure of the connection between the battery cell and the busbar component.

In some embodiments, the charging time for a single battery cell from 10% SOC to 80% SOC is 5 to 10.5 minutes.

Secondly, embodiments of this application provide an electrical device that includes a battery provided in any of the embodiments of the first aspect, the battery being used to provide electrical energy.

Attached Figure Description

To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

Figure 1 is a schematic diagram of the vehicle structure provided in some embodiments of this application;

Figure 2 is a schematic diagram of a battery provided in some embodiments of this application;

Figure 3 is an exploded schematic diagram of a battery cell provided in some embodiments of this application;

Figure 4 is a schematic diagram of a battery provided in some embodiments of this application;

Figure 5 is an enlarged view of Figure 4 at the circular frame;

Figure 6 is a structural schematic diagram of the first busbar component shown in Figure 5;

Figure 7 is a schematic diagram showing the connection between a battery cell and a first busbar according to some embodiments of this application;

Figure 8 is a schematic diagram of the electrode assembly described in Figure 3;

Figure 9 is a cross-sectional schematic diagram of the electrode assembly shown in Figure 8;

Figure 10 is a cross-sectional schematic diagram of the negative electrode sheet of a battery cell provided in some embodiments of this application;

Figure 11 is a cross-sectional schematic diagram of the positive electrode sheet of a battery cell provided in some embodiments of this application;

Figure 12 is a cross-sectional schematic diagram of the negative electrode sheet of a battery cell provided in some other embodiments of this application;

Figure 13 is a top view of a battery provided in some other embodiments of this application;

Figure 14 is an enlarged view of Figure 13 at the boxed area;

Figure 15 is a schematic diagram of the structure of the second busbar component in Figure 14.

The reference numerals in the attached figures are explained as follows:

1. Vehicle; 2. Battery; 3. Controller; 4. Motor;

10. Battery cell; 100. Battery cell array; 10a. Large surface; 10b. Narrow surface;

11. Electrode assembly; 111. Positive electrode sheet; 1111. Positive current collector; 1112. Positive electrode film; 112. Negative electrode sheet; 1121. Negative current collector; 1122. Negative electrode film; 11221. First negative electrode film; 11222. Second negative electrode film; 112a. Flat layer; 113. Separator; 11a. Main body; 11b. Positive electrode tab; 11c. Negative electrode tab; 11d. First surface; 11e. Second surface; 11f. Third surface;

12. Outer shell; 121. Housing; 122. End cap; 13. Electrode terminal;

20. Box body; 21. Limiting beam; 22. Frame; 23. Support beam; 24. Load-bearing plate;

30. Busbar component; 30a. First busbar component; 30b. Second busbar component; 30c. Third busbar component; 31. First busbar layer; 311. First busbar section; 312. Second busbar section; 313. First buffer section; 314. Recess; 32. Second busbar layer; 321. First stacked section; 322. Second stacked section; 323. Second buffer section; 33. Bending section;

X: Thickness direction; Y: Width direction; Z: Height direction.

Detailed Implementation

To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in the description of this application is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms "comprising" and "having," and any variations thereof, in the description, claims, and accompanying drawings of this application are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the description, claims, or accompanying drawings of this application are used to distinguish different objects, not to describe a specific order or hierarchy.

In this application, the reference to "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments.

In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "attachment" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

In this application, the term "and/or" is merely a description of the relationship between related objects, indicating that three or more relationships can exist. Such a relationship, for example, A and/or B, can represent three cases: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character "/" in this application generally indicates that the preceding and following objects have an "or" relationship.

In the embodiments of this application, the same reference numerals denote the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width, and other dimensions of various components in the embodiments of this application shown in the accompanying drawings, as well as the overall thickness, length, width, and other dimensions of the integrated device, are merely illustrative and should not constitute any limitation on this application.

The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a specific parameter, it is also expected that ranges of 60 to 110 and 80 to 120 are also included. Furthermore, if minimum range values of 1 and 2 are listed, and if maximum range values of 3, 4, and 5 are listed, then the following ranges are all expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise stated, the numerical range "a to b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 and 5" have been listed in this article; "0 to 5" is just a shortened representation of these numerical combinations. In addition, when a parameter is stated as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

In this application, "multiple" means two or more (including two).

"Parallelism" includes not only absolutely parallel cases, but also roughly parallel cases as commonly understood in engineering. "Perpendicularity" includes not only absolutely perpendicular cases, but also roughly perpendicular cases as commonly understood in engineering.

Currently, judging from market trends, battery applications are becoming increasingly widespread. Batteries are not only used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, but also extensively in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in aerospace and other fields. With the continuous expansion of battery applications, market demand is also constantly increasing.

A battery typically refers to a single physical module comprising multiple individual cells to provide higher voltage and capacity. The individual cell is the smallest unit that makes up a battery, and multiple cells are usually electrically connected via a busbar. During cycling, electrochemical reactions occur inside the individual cells, causing them to expand. This expansion puts tension on the busbar, increasing the risk of connection failure between the individual cells and the busbar, thus affecting reliability. To reduce this risk, the thickness of the busbar can be reduced, allowing it to release stress through deformation when the individual cells expand, thus minimizing the risk of connection failure. However, reducing the thickness of the busbar reduces its current-carrying area, leading to increased temperature and resistance, which affects the battery's fast-charging capability.

In view of this, embodiments of this application provide a battery that, through rational design of the battery cells and the busbar components, reduces the risk of connection failure between the battery cells and the busbar components, increases the current-carrying area of the busbar components, and improves the battery's fast charging capability.

The battery described in this application is applicable to electrical devices that use batteries. The electrical device can be a device that uses a battery as a power source or various energy storage systems that use a battery as an energy storage element. The electrical device can be, but is not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Etc. Among them, electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

For ease of explanation, the following embodiments will use a vehicle as an example of an electrical device.

Figure 1 is a schematic diagram of the vehicle structure provided in some embodiments of this application.

As shown in Figure 1, a battery 2 is installed inside the vehicle 1. The battery 2 can be located at the bottom, front, or rear of the vehicle 1. The battery 2 can be used to power the vehicle 1; for example, the battery 2 can serve as the operating power source for the vehicle 1.

Vehicle 1 may also include controller 3 and motor 4. Controller 3 is used to control battery 2 to supply power to motor 4, for example, for the power needs of vehicle 1 during start-up, navigation and driving.

In some embodiments of this application, the battery 2 can not only serve as the operating power source for the vehicle 1, but also as the driving power source for the vehicle 1, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1.

Figure 2 is a schematic diagram of a battery provided in some embodiments of this application.

Referring to FIG2, in some embodiments, the battery 2 includes a housing 20 and a plurality of battery cells 10 housed within the housing 20.

The battery cell 10 can be a secondary battery. A secondary battery is a battery cell that can be recharged to activate the active materials and continue to be used after the battery cell has been discharged.

For example, the battery cell 10 can be a lithium-ion battery cell, a sodium-ion battery cell, a sodium-lithium-ion battery cell, a lithium metal battery cell, a sodium metal battery cell, a lithium-sulfur battery cell, a magnesium-ion battery cell, a nickel-metal hydride battery cell, a nickel-cadmium battery cell, a lead-acid battery cell, etc.

As an example, the battery cell 10 can be a cylindrical battery cell, a prismatic battery cell, a pouch battery cell, or a battery cell of other shapes. Prismatic battery cells include prismatic battery cells, blade-shaped battery cells, and multi-prismatic batteries, such as hexagonal prismatic batteries.

Multiple battery cells 10 can be connected in series, parallel, or in a mixed manner. A mixed connection means that multiple battery cells 10 are connected in both series and parallel. Multiple battery cells 10 can be directly connected in series, parallel, or in a mixed manner, and then the whole assembly of multiple battery cells 10 is housed in the housing 20. Alternatively, multiple battery cells 10 can first be connected in series, parallel, or in a mixed manner to form a battery module, and then multiple battery modules can be connected in series, parallel, or in a mixed manner to form a whole assembly, which is then housed in the housing 20.

In some embodiments, the battery 2 includes a plurality of busbars that electrically connect a plurality of battery cells 10.

In some embodiments, the housing 20 may be part of the vehicle's chassis structure. For example, a portion of the housing 20 may be at least a portion of the vehicle's floor, or a portion of the housing 20 may be at least a portion of the vehicle's crossbeams and longitudinal beams.

Figure 3 is an exploded schematic diagram of a battery cell provided in some embodiments of this application.

Referring to FIG3, in some embodiments, the battery cell 10 includes a housing 12 and an electrode assembly 11 housed within the housing 12.

The outer shell 12 is a hollow structure, forming an internal space for accommodating the electrode assembly 11 and the electrolyte. The shape of the outer shell 12 can be determined according to the specific shape of the electrode assembly 11. For example, if the electrode assembly 11 has a cuboid structure, a cuboid outer shell can be used.

As an example, the housing 12 includes a housing 121 and an end cap 122, the housing 121 having an opening and the end cap 122 for closing the opening.

The housing 121 is a component used to cooperate with the end cap 122 to form an internal cavity of the battery cell 10, which can be used to accommodate the electrode assembly 11, electrolyte and other components.

The housing 121 and the end cap 122 can be separate components. For example, an opening can be provided on the housing 121, and the end cap 122 can be used to close the opening to form an internal cavity for the battery cell 10.

The housing 121 can have various shapes and sizes, such as cuboid, cylindrical, hexagonal prism, etc. Specifically, the shape of the housing 121 can be determined according to the specific shape and size of the electrode assembly 11. The material of the housing 121 can be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, etc., and this application embodiment does not impose any special limitations on this.

The shape of the end cap 122 can be adapted to the shape of the housing 121 to fit the housing 121. The material of the end cap 122 can be the same as or different from the material of the housing 121. Optionally, the end cap 122 can be made of a material with a certain hardness and strength (such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc.), so that the end cap 122 is not easily deformed when subjected to compression and impact, so that the battery cell 10 can have higher structural strength and improve reliability.

The end cap 122 is connected to the housing 121 by welding, bonding, snap-fitting or other means.

The housing 121 may be open at one end or open at both ends. In some examples, the housing 121 may be a structure with an opening on one side, and an end cap 122 is provided and covers the housing 121. In other examples, the housing 121 may also be a structure with openings on both sides, and two end caps 122 are provided, with the two end caps 122 respectively covering the two openings of the housing 121.

Electrode assembly 11 is a component in the battery cell 10 where electrochemical reactions occur. The housing 121 may contain one or more electrode assemblies 11.

In some embodiments, the electrode assembly 11 includes a positive electrode and a negative electrode. During the charging and discharging process of the battery cell 10, active ions (e.g., lithium ions) are inserted and extracted back and forth between the positive and negative electrode.

As an example, the portions of the positive and negative electrodes containing active material constitute the main body 11a of the electrode assembly 11, the portion of the positive electrode without active material constitutes the positive tab 11b, and the portion of the negative electrode without active material constitutes the negative tab 11c. The positive tab 11b and the negative tab 11c may be located together at one end of the main body 11a or at both ends of the main body 11a respectively.

In some embodiments, the electrode assembly 11 further includes a separator membrane disposed between the positive electrode and the negative electrode, which can prevent short circuit between the positive and negative electrodes, while allowing active ions to pass through.

In some embodiments, the electrode assembly 11 is a wound structure. The positive and negative electrode sheets are wound into a wound structure.

In some embodiments, the electrode assembly 11 has a stacked structure.

As an example, multiple positive and negative electrodes can be set, and multiple positive and multiple negative electrodes can be stacked alternately.

As an example, multiple positive electrode plates can be provided, and negative electrode plates can be folded to form multiple stacked folded segments, with a positive electrode plate sandwiched between adjacent folded segments.

As an example, both the positive and negative electrode plates are folded to form multiple stacked folded segments.

As an example, multiple separators can be provided, each positioned between any adjacent positive or negative electrode plates.

As an example, the separator can be continuously installed, either by folding or rolling, between any two adjacent positive electrodes. Between the plate or the negative electrode plate.

In some embodiments, the battery cell 10 further includes an electrode terminal 13 disposed on the housing 12; the electrode terminal 13 can be electrically connected to the electrode assembly 11 to input or output electrical energy.

In some embodiments, electrode terminals 13 are electrically connected to tabs. Exemplarily, there are two electrode terminals 13, which are electrically connected to the positive tab 11b and the negative tab 11c, respectively.

Figure 4 is a schematic diagram of a battery provided in some embodiments of this application; Figure 5 is an enlarged schematic diagram of Figure 4 at the circular frame; Figure 6 is a structural schematic diagram of the first busbar shown in Figure 5; Figure 7 is a schematic diagram of the connection between a battery cell and the first busbar provided in some embodiments of this application; Figure 8 is a schematic diagram of the electrode assembly described in Figure 3; Figure 9 is a cross-sectional schematic diagram of the electrode assembly shown in Figure 8; Figure 10 is a cross-sectional schematic diagram of the negative electrode of a battery cell provided in some embodiments of this application; Figure 11 is a cross-sectional schematic diagram of the positive electrode of a battery cell provided in some embodiments of this application; Figure 12 is a cross-sectional schematic diagram of the negative electrode of a battery cell provided in other embodiments of this application.

Referring to Figures 4 to 12, an embodiment of this application provides a battery, which includes a plurality of battery cells 10 and a plurality of busbar components 30, wherein the plurality of busbar components 30 electrically connect the plurality of battery cells 10.

Multiple busbar components 30 can connect multiple battery cells 10 in series, parallel, or mixed connections.

Multiple busbar components 30 may adopt the same structure or different structures.

In some embodiments, a plurality of battery cells 10 are arranged along the thickness direction X of the battery cells 10. Each battery cell 10 includes a housing 12 and an electrode assembly 11 housed within the housing 12. The expansion pressure of the battery cells 10 in the thickness direction X is 0.5 MPa to 2.4 MPa.

In some embodiments, the battery includes a first busbar 30a, which electrically connects at least two battery cells 10 arranged along the thickness direction X. The first busbar 30a has a multilayer structure.

The electrode assembly 11 includes a positive electrode 111, a negative electrode 112, and a separator 113 located between the positive electrode 111 and the negative electrode 112. The positive electrode 111 includes a positive current collector 1111 and a positive electrode film 1112 disposed on at least one side of the positive current collector 1111. The positive electrode film 1112 includes a positive active material, which may include a lithium phosphate with an olivine structure. The negative electrode 112 includes a negative current collector 1121 and a negative electrode film 1122 disposed on at least one side of the negative current collector 1121. The negative electrode film 1122 includes a negative active material, which may include a carbon-based material.

The battery cells 10 can be arranged in one column or multiple columns. For example, a column of battery cells 10 can constitute a battery cell column 100, which includes at least two battery cells 10 arranged along the thickness direction X.

The battery cell 10 may include one or more electrode assemblies 11. Optionally, the electrode assemblies 11 are arranged along the thickness direction X.

Optionally, the expansion pressure of the battery cell 10 in the thickness direction X is 0.5MPa, 0.6MPa, 0.7MPa, 0.8MPa, 0.9MPa, 1.0MPa, 1.1MPa, 1.2MPa, 1.3MPa, 1.4MPa, 1.5MPa, 1.6MPa, 1.7MPa, 1.8MPa, 1.9MPa, 2.0MPa, 2.1MPa, 2.2MPa, 2.3MPa, or 2.4MPa.

As an example, the expansion pressure of the battery cell 10 can be measured in the following manner:

At an ambient temperature of 45℃, the battery cell 10 was discharged to 2.0V at a constant current discharge rate of 1C.

The battery cell 10 is clamped between two clamping plates, which are located on both sides of the battery cell 10 along the thickness direction X and cover the large surface 10a (the large surface 10a is the surface of the battery cell 10 on one side along the thickness direction X).

At an ambient temperature of 45°C, the battery cells were charged to 3.8V at a constant current charging rate of 0.8C, and the pressure exerted by the battery cells on the clamping plate was detected and recorded.

The battery cells were cyclically charged and discharged according to the above charging strategy until the battery cells reached 70% SOH (i.e., the capacity retention rate of the battery cell = the discharge capacity of the battery cell / the nominal capacity of the battery cell = 70%), and the maximum pressure exerted by the battery cell on the clamping plate was recorded.

The expansion pressure Q of a single battery cell in the thickness direction is calculated as: maximum pressure / large surface area.

In this embodiment, the negative electrode film layer 1122 may be provided only on one side of the negative electrode current collector 1121, or the negative electrode film layer 1122 may be provided on both sides of the negative electrode current collector 1121.

Optionally, a negative electrode film layer 1122 is provided on both opposite surfaces of the negative electrode current collector 1121 along its thickness direction. The negative electrode film layer 1122 on the two surfaces of the negative electrode current collector 1121 can be made of the same negative electrode active material or different negative electrode active materials; the thickness of the negative electrode film layer 1122 on the two surfaces of the negative electrode current collector 1121 can be the same or different.

Exemplarily, the negative electrode current collector 1121 may be a metal foil or a composite current collector. Examples of metal foils include at least one foil selected from copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. The composite current collector may include a polymeric material substrate and a metal material layer formed on at least one surface of the polymeric material substrate. As an example, the metal material layer may include at least one of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymeric material substrate may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

Negative electrode active materials include carbon-based materials. Carbon-based materials have high cycle stability and can improve the cycle performance of individual battery cells.

The positive current collector 1111 has two surfaces opposite each other in its thickness direction, and the positive electrode film layer 1112 is disposed on either or both of the two opposite surfaces of the positive current collector 1111.

Exemplarily, the positive current collector 1111 may be a metal foil or a composite current collector. Examples of metal foils include at least one foil selected from aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. The composite current collector may include a polymeric material substrate and a metal material layer formed on at least one surface of the polymeric material substrate. As an example, the metal material layer may include at least one selected from aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymeric material substrate may include at least one selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

Lithium-containing phosphates have high cycle stability. Using lithium-containing phosphates as positive electrode active materials can improve the cycle degradation caused by excessive temperature rise during fast charging of battery cell 10.

Multiple busbar components 30 may all be the first busbar component 30a, or some may be the first busbar component 30a.

The expansion pressure of the battery cell 10 is related to the density of the electrode assembly 11. In this embodiment, the battery cell 10 can have an expansion pressure greater than or equal to 0.5 MPa in the thickness direction X, thereby increasing the density of the electrode assembly 11 and improving the energy density of the battery cell 10. An expansion pressure of less than or equal to 2.4 MPa in the thickness direction X of the battery cell 10 can limit the deformation of the electrode assembly 11 during cycling, reducing the risk of wrinkling and deformation of the separator in the electrode assembly 11 and the risk of increased local spacing between the positive and negative electrode plates, thus reducing polarization and improving the cycle performance of the battery cell 10.

The first busbar 30a has a multi-layer structure, and each layer of the first busbar 30a can transmit current. This allows the first busbar 30a to have a higher current-carrying area, thereby reducing the heat generated by the first busbar 30a and improving the fast charging capability of the battery 2.

Provided the flow area meets the requirements, setting the first busbar component 30a as a multi-layer structure can reduce the thickness of each layer of the first busbar component 30a. During cycling, the battery cell 10 expands, stretching the layer of the first busbar component 30a connected to the battery cell 10. The first layer of the first busbar component 30a has a small thickness, making it easily deformable to accommodate the expansion deformation of the battery cell 10. This reduces the risk of the connection between the battery cell 10 and the first busbar component 30a cracking when the expansion pressure of the battery cell 10 is between 0.5 MPa and 2.4 MPa, thus improving the reliability of the battery 2.

The embodiments of this application employ a first busbar component with a multi-layer structure, which can adapt to the expansion of the battery cell and take into account the current carrying capacity and deformability of the first busbar component, thereby improving the reliability and fast charging capability of the battery.

In some embodiments, the first busbar component 30a includes a first busbar layer 31 and a second busbar layer 32 that are stacked and connected together, wherein the first busbar layer 31 connects at least two battery cells 10 arranged along the thickness direction X.

The first bus layer 31 and the second bus layer 32 can be integrally formed. Alternatively, the first bus layer 31 and the second bus layer 32 can also be formed independently and connected by welding or other means.

Both the first busbar 31 and the second busbar 32 can transmit current, which allows the first busbar component 30a to have a higher current-carrying area, thereby reducing heat generation in the first busbar component 30a and improving the battery's fast-charging capability and reliability. Provided the current-carrying area requirement is met, setting the first busbar component 30a as a double-layer structure can reduce the thickness requirement of the first busbar layer 31. During cycling, the battery cell 10 expands, stretching the first busbar layer 31. The first busbar layer 31 has a relatively small thickness and is easily deformable to accommodate the deformation of the battery cell 10, reducing the risk of tearing at the connection between the battery cell 10 and the first busbar layer 31, and improving the reliability of the battery 2.

In some embodiments, the battery cell 10 includes an electrode terminal 13 disposed on the housing 12, the electrode terminal 13 being electrically connected to the electrode assembly 11. A first bus layer 31 is connected to the electrode terminal 13 of the battery cell 10.

Optionally, the first bus layer 31 is welded to the electrode terminal 13.

In some embodiments, a portion of the first busbar 31 that does not overlap with the second busbar 32 is connected to the electrode terminal 13.

The second busbar 32 can avoid the connection point between the first busbar 31 and the electrode terminal 13, thereby reducing the impact of the second busbar 32 on the connection point when the battery cell expands, reducing the risk of the connection point between the electrode terminal 13 and the first busbar 31 being torn, and improving the reliability of the battery 2. In addition, when assembling the battery cell 10 and the first busbar component 30a, the second busbar 32 will not cover the area of the first busbar 31 used for connection with the electrode terminal 13, which can reduce the assembly difficulty.

In some embodiments, the first bus layer 31 is welded to the electrode terminal 13, and the welding area between the first bus layer 31 and the electrode terminal 13 is greater than or equal to 60 ^mm² .

For example, the first bus layer 31 is welded to the electrode terminal 13 to form a solder mark; the welding area can be the area of the solder mark projected along the thickness direction of the first bus layer. Optionally, the solder mark is annular, and the inner radius and outer radius of the solder mark are _R1 and _R2 respectively, then the welding area is π _× ( _R22 ^{-R12 )} .

For example, the welding area between the first bus layer 31 and the electrode terminal 13 is 60 ^mm² , 70 ^mm² , 80 ^mm² , 90 ^mm² , 100 ^mm² , 110 ^mm² or 120 ^mm² .

The embodiments of this application can provide a larger flow area between the first busbar 31 and the electrode terminal 13, thereby reducing heat generation at the welding point, lowering the temperature rise of the first busbar 31 during fast charging, and improving the fast charging capability of the battery.

In some embodiments, the second bus layer 32 is not covered with solder pads.

In some embodiments, in the stacking direction of the first bus layer 31 and the second bus layer 32, the second bus layer 32 partially overlaps with the electrode terminal 13, which can shorten the conductive path between the second bus layer 32 and the electrode terminal 13, thereby reducing resistance and heat generation.

In some embodiments, the first busbar 31 and the second busbar 32 are stacked along the height direction Z of the battery cell 10. In other words, the stacking direction of the first busbar 31 and the second busbar 32 is parallel to the height direction Z. Exemplarily, the height direction Z is perpendicular to the thickness direction X.

In some embodiments, the second busbar 32 may be disposed on the side of the first busbar 31 facing the battery cell 10, or it may be disposed on the side of the first busbar 31 away from the battery cell 10.

In some embodiments, the first busbar component 30a includes at least one bend 33, which connects the first busbar layer 31 and the second busbar layer 32.

There can be one or more bends 33.

The bend 33 can connect the first bus layer 31 and the second bus layer 32 and transmit current between the first bus layer 31 and the second bus layer 32, thereby improving the current carrying capacity of the first bus component 30a.

In some embodiments, the first busbar layer 31 includes a first busbar 311, a second busbar 312, and a first buffer 313. The first busbar 311 and the second busbar 312 are disposed along the thickness direction X and connected to different battery cells 10. The first buffer 313 connects the first busbar 311 and the second busbar 312. At least one of the first busbar 311 and the second busbar 312 is connected to the bending portion 33.

The first busbar 311 can be connected to the electrode terminal 13 of one battery cell 10, or it can be connected to the electrode terminals 13 of at least two battery cells 10 simultaneously. The second busbar 312 can be connected to the electrode terminal 13 of one battery cell 10, or it can be connected to the electrode terminals 13 of at least two battery cells 10 simultaneously.

During the cycling process of the battery cell 10, the battery cell 10 expands and applies tension to the first busbar 31; the first buffer 313 can release stress through deformation, thereby reducing the stress at the connection between the first busbar 311 and the battery cell 10 and the connection between the second busbar 312 and the battery cell 10, and reducing the risk of failure of the connection between the first busbar 31 and the battery cell 10.

In some embodiments, the bending portion 33 is disposed away from the first buffer portion 313. The bending portion 33 is not directly connected to the first buffer portion 313, thereby reducing the impact of the bending portion 33 on the deformation of the first buffer portion 313 and reducing the difficulty of deforming the first buffer portion 313.

In some embodiments, the first bus layer 31 and the second bus layer 32 are bonded together. Optionally, apart from the initial bend 33, there is no other fixed connection between the first bus layer 31 and the second bus layer 32. Alternatively, conductive adhesive may be provided between the first bus layer 31 and the second bus layer 32.

In some embodiments, the first busbar 311 is located above the electrode terminal 13 of the battery cell 10, and the second busbar 312 is located above the electrode terminal 13 of the battery cell 10.

In some embodiments, the first buffer portion 313 includes an arched structure.

In some embodiments, the first busbar 311 is connected to the second busbar layer 32 via at least one bend 33, and the second busbar 312 is connected to the second busbar layer 32 via at least one bend 33.

In some embodiments, the second bus layer 32 includes a first stacked portion 321, a second stacked portion 322, and a second buffer portion 323. The first stacked portion 321 is stacked with the first bus layer 311 and connected by at least one bend 33. The second stacked portion 322 is stacked with the second bus layer 312 and connected by at least one bend 33. The second buffer portion 323 connects the first stacked portion 321 and the second stacked portion 322. In the stacking direction of the first bus layer 31 and the second bus layer 32, the second buffer portion 323 at least partially overlaps with the first buffer portion 313.

During the cycling process of the battery cell 10, the battery cell 10 expands and applies tension to the first busbar 31; both the first buffer portion 313 and the second buffer portion 323 can release stress through deformation, thereby reducing the risk of connection failure between the first busbar 31 and the battery cell 10. The second buffer portion 323 at least partially overlaps with the first buffer portion 313, so that the deformation areas of the first buffer portion 313 and the second buffer portion 323 are close, thereby reducing the risk of interference between the first buffer portion 313 and the second buffer portion 323 and other parts during deformation.

In some embodiments, the second buffer portion 323 and the first buffer portion 313 are fitted together. This embodiment can save space and improve current carrying capacity.

In some embodiments, the outer surface of the battery cell 10 includes two large surfaces 10a and two narrow surfaces 10b. The two large surfaces 10a are arranged opposite each other along the thickness direction X, and the two narrow surfaces 10b are arranged opposite each other along the width direction Y of the battery cell. The two ends of the large surfaces 10a along the width direction Y are connected to the two narrow surfaces 10b. The area of the large surfaces 10a is larger than the area of the narrow surfaces 10b.

In some embodiments, the thickness direction X, the width direction Y, and the height direction Z are perpendicular to each other.

In some embodiments, multiple battery cell rows 100 are arranged along the width direction Y.

In some embodiments, the expansion pressure of the battery cell 10 in the thickness direction X is 1.5 MPa-2.0 MPa.

In this embodiment, the expansion pressure of the battery cell 10 in the thickness direction X is limited to 1.5MPa-2.0MPa, so as to reduce the pulling force of the battery cell on the first busbar component during the battery cell cycle, reduce the risk of connection failure between the battery cell and the first busbar component, and improve the reliability of the battery.

In some embodiments, the thickness of the first busbar 31 is 1mm-2.5mm, and optionally 1.2mm-1.8mm.

As an example, the thickness of the first busbar 31 is 1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm or 2.5 mm.

The thickness of the first busbar 31 is selected according to the expansion pressure of the battery cell 10 in this embodiment, which can balance the current carrying capacity and deformability of the first busbar 31 to a certain extent, thereby improving the fast charging capability and reliability of the battery 2.

In some embodiments, the thickness of the second bus layer 32 is 1mm-2.5mm, optionally 1.2mm-1.8mm. As an example, the thickness of the second bus layer 32 is 1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, 1.8mm, 1.9mm, 2mm, 2.1mm, 2.2mm, 2.3mm, 2.4mm, or 2.5mm.

The thickness of the second busbar 32 can be selected based on the thickness of the first busbar 31 and the current carrying capacity of the battery to the first busbar component. For example, when the thickness of the first busbar 31 is small, the second busbar 32 may have a greater thickness than the first busbar 31 to improve the current carrying capacity of the first busbar component.

In some embodiments, the volumetric energy density of the battery cell 10 is 390Wh/L-450Wh/L, and the thickness of the first busbar 31 is less than or equal to 2.5mm.

The volumetric energy density of the battery cell 10 has a meaning known in the art and can be tested using equipment and methods known in the art.

The expansion of the battery cell 10 is related to its volumetric energy density. This application designs the thickness of the first busbar 31 based on the volumetric energy density of the battery cell 10, thereby taking into account the current carrying capacity and deformability of the first busbar 31 to a certain extent, thereby improving the fast charging capability and reliability of the battery 2.

In some embodiments, the volumetric energy density of the battery cell 10 is 450Wh/L-480Wh/L, and the thickness of the first busbar 31 is less than or equal to 2.2mm.

The expansion of the battery cell 10 is related to its volumetric energy density. For the battery 2 using battery cells 10 with high volumetric energy density, the thickness of the first busbar 31 needs to be reduced. In this embodiment, the thickness of the first busbar 31 is designed according to the volumetric energy density of the battery cell 10, thereby balancing the current carrying capacity and deformability of the first busbar 31 to a certain extent, thus improving the fast charging capability and reliability of the battery 2.

In some embodiments, the negative electrode active material further includes a silicon-based material. The silicon content in the negative electrode active material is 1%-6% by mass; the thickness of the first busbar 31 is 1.2mm-2.2mm, and the thickness of the second busbar 32 is 1.2mm-2.2mm.

As an example, the mass content of silicon in the negative electrode active material of the silicon-based material is 1%, 2%, 3%, 4%, 5%, or 6%. As an example, the thickness of the first busbar 31 is 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2 mm, 2.1 mm, or 2.2 mm. As an example, the thickness of the second busbar 32 is 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2 mm, 2.1 mm, or 2.2 mm.

By introducing silicon-based materials, the capacity of the negative electrode 112 can be increased, thereby improving the energy density of the battery cell 10. Introducing silicon-based materials also increases the expansion of the negative electrode 112 during cycling. By designing the thickness of the first busbar 31 and the second busbar 32 in conjunction with the silicon content, the risk of connection failure between the first busbar 31 and the battery cell 10 due to the introduction of silicon-based materials can be reduced, while also meeting the overcurrent capacity requirements of the first busbar component 30a.

In some embodiments, the first busbar layer 31 includes a first busbar 311, a second busbar 312, and a first buffer portion 313 connecting the first busbar 311 and the second busbar 312. The first busbar 311 and the second busbar 312 are disposed along the thickness direction X and connected to different battery cells 10. In the stacking direction of the first busbar layer 31 and the second busbar layer 32, the first buffer portion 313 protrudes from the first busbar 311 and the second busbar 312. The first busbar layer 31 has a recess 314 at a position corresponding to the first buffer portion 313.

By providing the recess 314, the strength of the first buffer portion 313 can be reduced, which facilitates the deformation of the first buffer portion 313 when the battery cell 10 expands.

In some embodiments, the volumetric energy density of the battery cell 10 is 390Wh/L-450Wh/L, and the depth _H2 of the recess 314 is 1.2mm-2.5mm.

The expansion of the battery cell 10 is related to its volumetric energy density. This application designs the depth of the recess 314 based on the volumetric energy density of the battery cell 10, thereby taking into account the overcurrent capacity and deformability of the first buffer portion 313 to a certain extent, thereby improving the fast charging capability and reliability of the battery 2.

In some embodiments, the volumetric energy density of the battery cell 10 is 450Wh/L-480Wh/L, and the depth of the recess 314 is 1mm-2.2mm.

The expansion of the battery cell 10 is related to its volumetric energy density. For the battery 2 using battery cells 10 with high volumetric energy density, it is necessary to reduce the difficulty of deformation of the first buffer portion 313. In this embodiment, the depth of the recess 314 is designed according to the volumetric energy density of the battery cell 10, thereby taking into account the current carrying capacity of the first buffer portion 313 to a certain extent. The deformability of the first buffer section 313 enhances the fast charging capability and reliability of the battery 2.

In some embodiments, the battery 2 further includes a housing 20. The housing 20 is used to accommodate a plurality of battery cells 10. The housing 20 includes at least two limiting beams 21, with adjacent limiting beams 21 arranged along the thickness direction X, and the plurality of battery cells 10 arranged between adjacent limiting beams 21.

As an example, at least one battery cell row 100 is provided between any two adjacent limiting beams 21.

The limiting beam 21 can be used to limit the expansion and deformation of the battery cell 10 in the thickness direction X. The limiting beam 21 can directly abut against the battery cell 10 in the thickness direction X; alternatively, other components can also be provided between the limiting beam 21 and the battery cell 10, that is, the limiting beam 21 limits the expansion of the battery cell 10 through these components.

The limiting beam 21 can restrict the expansion of the battery cell 10 during battery cycling, thereby reducing the tensile force exerted by the battery cell 10 on the first busbar component 30a, reducing the risk of connection failure between the battery cell 10 and the first busbar component 30a, and improving the reliability of the battery.

In some embodiments, the electrode assembly 11 includes two first surfaces 11d and two second surfaces 11e. The two first surfaces 11d are disposed opposite each other along the thickness direction X, and the two second surfaces 11e are disposed opposite each other along a direction perpendicular to the thickness direction X. The second surfaces 11e connect the two first surfaces 11d. The area of the first surfaces 11d is larger than the area of the second surfaces 11e.

By positioning the larger first surface 11d opposite the limiting beam 21 along the thickness direction X, the force-bearing area of the limiting beam 21 can be increased and the deformation of the limiting beam 21 can be reduced when the electrode assembly 11 expands.

In some embodiments, the limiting beam 21 extends along the width direction Y.

In some embodiments, the two second surfaces 11e are arranged opposite each other along the width direction Y.

In some embodiments, the main body 11a includes two first surfaces 11d, two second surfaces 11e, and two third surfaces 11f; the two third surfaces 11f are located at both ends of the battery cell 10 along the height direction Z, and the third surfaces 11f are connected to the two first surfaces 11d and the two second surfaces 11e.

The positive electrode tab 11b and the negative electrode tab 11c extend from the same third surface 11f, or the positive electrode tab 11b and the negative electrode tab 11c extend from two different third surfaces 11f.

In some embodiments, at least a portion of the second surface 11e is arc-shaped. Optionally, the electrode assembly 11 is a wound structure, and the second surface 11e is an arc surface.

In some embodiments, the large surface 10a is parallel to the first surface 11d.

In some embodiments, the battery cell 10 is a prismatic battery cell. Optionally, the narrow face 10b is perpendicular to the large face 10a.

In some embodiments, a portion of the negative electrode current collector 1121 is not covered by the negative electrode film layer 1122; the portion of the negative electrode current collector 1121 not covered by the negative electrode film layer 1122 may be used to form a negative electrode tab 11c.

In some embodiments, the thickness of the negative electrode current collector 1121 is 4 μm to 6 μm. Exemplarily, the thickness of the negative electrode current collector 1121 is 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, or any range of two of the above values.

In some embodiments, the compaction density of the negative electrode film layer 1122 at 100% SOC of the battery cell is 1.15 g/ ^cm³ to 1.36 g/ ^cm³ . Exemplarily, the compaction density of the negative electrode film layer 1122 at 100% SOC of the battery cell 10 is 1.15 g/ ^cm³ , 1.18 g/ ^cm³ , 1.20 g/ ^cm³ , 1.22 g/ ^cm³ , 1.25 g/ ^cm³ , 1.28 g/ ^cm³ , 1.3 g/ ^cm³ , 1.32 g/ ^cm³ , 1.35 g/ ^cm³ , 1.36 g/ ^cm³ , or a range consisting of any two of the above values.

For example, 100% SOC (state of charge) and 0% SOC are defined as follows:

The battery cells are charged at a constant current rate of 0.33C to the upper limit of the battery charging voltage, and then charged at a constant voltage until... 0.05C corresponds to a 100% SOC state for a single battery cell; discharging a single battery cell at a constant current discharge rate of 0.33C to the cutoff voltage corresponds to a 0% SOC state for the single battery cell. For example, the upper limit voltage for battery charging can be 3.8V; the battery discharge cutoff voltage can be 2.0V.

For example, the compaction density of the negative electrode film layer of a battery cell at 100% SOC is a well-known concept in the art, meaning that the negative electrode sheet is disassembled from the battery cell at 100% SOC, and the compaction density of the negative electrode film layer is measured. For example, a single-sided coated negative electrode sheet (if it is a double-sided coated negative electrode sheet, the negative electrode film layer on one side can be wiped off first) is cut into a small circular piece with an area of S1, its weight is weighed and recorded as M1, and its thickness H1 is measured. Then, the negative electrode film layer of the weighed negative electrode sheet is wiped off, the weight of the negative electrode current collector is weighed and recorded as M0, and its thickness H0 is measured. The single-sided coating weight of the negative electrode film layer = (weight of the negative electrode sheet M1 - weight of the negative electrode current collector M0) / S1, the thickness of the negative electrode film layer = thickness of the negative electrode sheet H1 - thickness of the negative electrode current collector H0, and the compaction density of the negative electrode film layer = single-sided coating weight of the negative electrode film layer / thickness of the negative electrode film layer.

The compaction density of the negative electrode film layer 1122 is related to the expansion of the battery cell 10 at 100% charge. Limiting the compaction density of the negative electrode film layer 1122 to 1.15 g/ ^cm3 to 1.36 g/ ^cm3 can, to a certain extent, balance the energy density and expansion pressure of the battery cell 10, reduce the deformation of the battery cell 10, and reduce the risk of failure of the connection between the battery cell 10 and the busbar component.

When the compaction density of the negative electrode film layer 1122 is within the above range, it is beneficial to improve the energy density of the battery cell 10; and since the negative electrode active material in the negative electrode film layer 1122 is packed more tightly, the contact resistance between particles is smaller, which can reduce the resistance of the negative electrode sheet 112, thereby reducing heat generation.

When the compaction density of the negative electrode film layer 1122 is within the above range, the fast charging capability of the battery cell 10 can be improved. A lower compaction density of the negative electrode film layer 1122 can increase the porosity of the negative electrode sheet 112, slow down the expansion of the negative electrode sheet, and reduce the expansion pressure of the battery cell 10.

In some embodiments, the negative electrode film layer 1122 has a compaction density of 1.25 g/ ^cm³ to 1.36 g/ ^cm³ at 100% SOC of the battery cell, which can improve the energy density of the battery cell 10.

In some embodiments, the single-sided coating weight of the negative electrode film layer 1122 is 90 mg/1540 ^mm² to 170 mg/1540 ^mm² . For example, the single-sided coating weight of the negative electrode film layer 1122 is 90 mg/1540.25 ^mm² , 92 mg/1540.25 ^mm² , 95 mg/1540.25 ^mm² , 96 mg/1540.25 ^mm² , 100 mg/1540.25 ^mm² , 102 mg/1540.25 ^mm² , 104 mg/1540.25 ^mm² , 105 mg/1540.25 ^mm² , 108 mg/1540.25 ^mm² , 110 mg/1540.25 ^mm² , 112 mg/1540.25 ^mm² , 114 mg/1540.25 ^mm² , or 115 mg/1540.25 ^mm². , 116mg/1540.25mm ² , 118mg/1540.25mm ² , 120mg/1540.25mm ² , 122mg/1540.25mm ² , 125mg/1540.25mm ² , 128mg/1540.25mm ² , 130mg/1540.25mm ² , 132mg/1540.25mm ² , 135mg/1540.25mm ² , 137mg/1540.25mm ² , 140mg/1540.25mm ² , 142mg/1540.25mm ² , 145mg/1540.25mm ² ,148mg/1540.25mm ² 150mg/1540.25mm² ^, 152mg/1540.25mm² ^, 155mg/1540.25mm² ^, 160mg/1540.25mm² ^, 165mg/1540.25mm² ^, 167mg/1540.25mm², ^170mg /1540.25mm² ^, or a range consisting of any two of the above values.

The single-sided coating weight of the negative electrode film layer 1122 is related to the expansion of the negative electrode film layer. Limiting the single-sided coating weight of the negative electrode film layer ¹¹²² to 90mg/1540mm2 to 170mg/ ^1540mm2 can, to a certain extent, balance the energy density and expansion pressure of the battery cell 10, reduce the deformation of the battery cell 10, and reduce the risk of connection failure between the battery cell 10 and the busbar component.

In addition, limiting the single-sided coating weight of the negative electrode film 1122 to 90mg/ ^1540mm² to 170mg/ ^1540mm² can also limit the heat generation per unit area of the negative electrode sheet 112, reduce the temperature rise of the battery cell 10, especially during fast charging.

In some embodiments, the single-sided coating weight of the negative electrode film layer 1122 is 110 mg/1540 ^mm² to 150 mg/1540 ^mm² , in order to further balance the energy density and expansion pressure of the battery cell 10.

In some embodiments, the porosity of the negative electrode 112 is 27%-40%. As an example, the porosity of the negative electrode 112 may be 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, or 40%.

The porosity of the negative electrode sheet can be defined as the percentage of the pore volume within the negative electrode sheet to its total volume. For example, when the battery cell is at 0% state of charge, a negative electrode sheet with double-sided coating is taken; the porosity of the negative electrode sheet is measured using a true density meter AccuPycⅡ1340 according to national standard GB/T 24586-2009.

In this embodiment, the porosity of the negative electrode 112 is greater than or equal to 27%, which provides space for impurities generated by side reactions in the negative electrode 112, slows down the expansion of the negative electrode 112, reduces the expansion pressure of the battery cell 10, reduces the deformation of the battery cell 10, improves the cycle performance of the battery cell 10, and reduces the risk of connection failure between the battery cell and the busbar component. The porosity of the negative electrode 112 is less than or equal to 40%, which can balance the energy density of the battery cell 10.

In some embodiments, the carbon-based material includes graphite particles with a graphitization degree of 92.0% to 94.5%. Exemplarily, the graphitization degree of the graphite particles is 92.0%, 92.5%, 93%, 93.5%, 94%, 94.5%, or a range consisting of any two of the above values.

When the degree of graphitization of the graphite particles is within the above range, the graphite particles have excellent electrical conductivity, which can reduce the heat generation of the negative electrode 112 and the heat generation of the battery cell 10; and can improve the fast charging performance of the battery cell 10.

In some embodiments, the carbon-based material includes at least one of artificial graphite and natural graphite. Artificial and natural graphite have good electrical conductivity, which can reduce heat generation of the negative electrode 112 during charging and improve the fast-charging performance of the battery cell 10.

In some embodiments, the negative electrode active material further includes a silicon-based material. The introduction of a silicon-based material can improve the capacity of the negative electrode active material and increase the energy density of the battery cell 10.

In some embodiments, the mass content of silicon in the silicon-based material in the negative electrode active material is 0.3% to 10%, optionally 1% to 6%. Exemplarily, the mass content of silicon in the negative electrode active material is 0.3%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.2%, 4.5%, 4.8%, 5%, 5.2%, 5.5%, 5.8%, 6%, 6.2%, 6.5%, 6.8%, 7%, 7.2%, 7.5%, 7.8%, 8%, 8.2%, 8.5%, 8.8%, 9%, 9.2%, 9.5%, 9.8%, 10%, or a range consisting of any two of the above values.

Introducing silicon-based materials into the negative electrode 112 can increase capacity but also increase the expansion of the negative electrode 112. Therefore, limiting the mass content of silicon in the negative electrode active material to 0.3% to 10% can, to a certain extent, balance the energy density and expansion of the battery cell 10, reduce the deformation of the battery cell 10, reduce the risk of connection failure between the battery cell and the busbar component, and improve the cycle performance of the battery cell 10.

The qualitative and quantitative analysis of each substance or element in this application can be performed using suitable equipment and methods known to those skilled in the art. Relevant testing methods can be referenced from domestic and international testing standards, domestic and international enterprise standards, etc. Furthermore, those skilled in the art can adaptively modify certain testing steps/instrument parameters from the perspective of testing accuracy to obtain more accurate testing results. A single testing method can be used for qualitative or quantitative determination, or several testing methods can be used in combination for qualitative or quantitative determination.

For example, silicon-based materials can be subjected to X-ray powder diffraction tests and qualitative analysis on negative electrode sheets or negative electrode active materials in accordance with the general rules of X-ray diffraction analysis in JIS/K0131-1996.

In some embodiments, the silicon-based material may include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material.

In some embodiments, the silicon-based material includes at least one of silicon oxides and silicon-carbon composites.

In some embodiments, the negative electrode active material may include, in addition to carbon-based materials and optionally silicon-based materials, at least one of tin-based materials and lithium titanate. Tin-based materials may include at least one of elemental tin, tin oxide, and tin alloy materials.

In some embodiments, the negative electrode film layer 1122 in this application includes at least one film layer; in other words, the negative electrode film layer 1122 can be a single film layer or at least two film layers. Optionally, the negative electrode film layer 1122 includes at least two film layers.

When the negative electrode film layer 1122 is a single layer, the negative electrode active material in the negative electrode film layer 1122 includes a carbon-based material, and optionally also includes a silicon-based material. When a single layer is used, the volume average particle size Dv50 of the negative electrode active material is from 8.2 μm to 13.5 μm. Exemplarily, the volume average particle size Dv50 of the negative electrode active material is 8.2 μm, 8.5 μm, 8.8 μm, 9 μm, 9.2 μm, 9.5 μm, 9.8 μm, 10 μm, 10.2 μm, 10.5 μm, 10.8 μm, 11 μm, 11.2 μm, 11.5 μm, 11.8 μm, 12 μm, 12.2 μm, 12.5 μm, 12.8 μm, 13 μm, 13.2 μm, 13.5 μm, or a range consisting of any two of the above values.

When the negative electrode film layer 1122 employs at least two film layers, the negative electrode active material in the negative electrode film layer 1122 includes a carbon-based material, and optionally also includes a silicon-based material. The silicon-based material may be located in one of the at least two film layers, or in at least two of the at least two film layers. The negative electrode film layer 1122 may include two film layers, three film layers, four film layers, or even more film layers.

In some embodiments, the negative electrode film layer 1122 includes a first negative electrode film layer 11221 and a second negative electrode film layer 11222, wherein the second negative electrode film layer 11222 is disposed between the first negative electrode film layer 11221 and the negative electrode current collector 1121. The negative electrode active material includes a first negative electrode active material disposed in the first negative electrode film layer 11221 and a second negative electrode active material disposed in the second negative electrode film layer 11222. The first negative electrode active material includes artificial graphite, and the second negative electrode active material includes one or more of artificial graphite, natural graphite, and silicon-based materials.

The interface between the first negative electrode film layer 11221 and the second negative electrode film layer 11222 can be regular or irregular; optionally, it can be irregular.

The first negative electrode film layer 11221 and the second negative electrode film layer 11222 can be configured differently, thereby taking into account the expansion and capacity of the negative electrode film layer 1122 to a certain extent; the double coating can create the porosity difference of the negative electrode film layer 1122, reduce the tortuosity of ion transport, reduce side reactions, and improve the fast charging performance of the battery cell 10.

Artificial graphite can have a small volume average particle size Dv50, which can shorten the solid-phase transport path of lithium ions and improve fast charging performance. On the other hand, the material is less prone to agglomeration during the preparation process, which can improve the stability of the material.

In some embodiments, the ratio of the thickness of the first negative electrode film 11221 to the thickness of the second negative electrode film 11222 is: 3:7 to 7:3. As an example, the thickness ratio of the first negative electrode film layer 11221 to the thickness ratio of the second negative electrode film layer 11222 is 3:7, 4:6, 5:5, 6:4 or 7:3.

Optionally, the thickness ratio of the first negative electrode film layer 11221 to the thickness ratio of the second negative electrode film layer 11222 is 4:6 to 6:4.

By adjusting the thickness ratio of the first negative electrode film layer 11221 and the second negative electrode film layer 11222, the gradient porosity difference between the upper and lower layers can be further increased, the lithium-ion transport tortuosity can be reduced, and the fast charging capability of the battery cell 10 can be improved.

In some embodiments, the thickness of the first negative electrode film layer 11221 is less than or equal to the thickness of the second negative electrode film layer 11222, which can further improve the fast charging capability of the battery cell 10.

In some embodiments, the first negative electrode active material is in particulate form, and the second negative electrode active material is in particulate form.

In some embodiments, the volume average particle size Dv50 of the first negative electrode active material is less than or equal to the volume average particle size Dv50 of the second negative electrode active material. Further optionally, the volume average particle size Dv50 of the first negative electrode active material is less than the volume average particle size Dv50 of the second negative electrode active material.

The difference in particle size between the first and second negative electrode active materials improves the fast-charging performance of the battery cell 10. During fast charging, the overpotential of the first negative electrode film 11221 is typically high, and the bottleneck of fast charging mainly lies in the first negative electrode film 11221. However, in this embodiment, the particle size of the first negative electrode active material is relatively small, which can shorten the solid-phase transport path of ions, improve fast-charging performance, and alleviate the problem of ion deposition on the surface of the negative electrode sheet 112. The particle size of the second negative electrode active material is relatively large, which can form larger pores in the second negative electrode film 11222. During charging, the pores can absorb expansion, reducing the expansion of the negative electrode film 1122, reducing the force exerted by the battery cell 10 on the first busbar component 30a, and reducing the risk of connection failure between the battery cell 10 and the first busbar component 30a.

In some embodiments, the volume average particle size Dv50 of the first negative electrode active material is 7.8 μm-14.3 μm, and optionally 7.8 μm-11.3 μm. For example, the volume average particle size Dv50 of the first negative electrode active material is 7.8 μm, 8.0 μm, 8.2 μm, 8.5 μm, 8.8 μm, 9 μm, 9.2 μm, 9.5 μm, 9.8 μm, 10 μm, 10.2 μm, 10.5 μm, 10.8 μm, 11 μm, 11.3 μm, 11.2 μm, 11.5 μm, 11.8 μm, 12 μm, 12.2 μm, 12.5 μm, 12.8 μm, 13 μm, 13.2 μm, 13.5 μm, 13.8 μm, 14 μm, 14.1 μm, 14.3 μm, or a range of any two of the above values.

The volume average particle size Dv50 of the first negative electrode active material is set to 7.8μm-14.3μm. On the one hand, this can shorten the solid-phase transport path of lithium ions and improve fast charging performance. On the other hand, the material is less prone to agglomeration during preparation, which can improve the stability of the material. Furthermore, the first negative electrode active material in the above-mentioned volume average particle size range can cooperate with the second negative electrode active material, which is conducive to constructing the gradient porosity difference between the first negative electrode film layer 11221 and the second negative electrode film layer 11222, reducing the tortuosity of lithium ion transport, and improving the fast charging performance of the battery cell 10.

The volume average particle size Dv50 of a material refers to the particle size corresponding to 50% of the volume distribution, and the volume average particle size Dv10 of a material refers to the particle size corresponding to 10% of the volume distribution. They can be detected using equipment and methods known in the art. For example, using the negative electrode active material as a sample, the Dv50 and Dv10 of the particles can be tested using a Mastersizer2000E laser particle size analyzer according to the testing standard GB/T 19077-2016.

In some embodiments, the volume average particle size Dv50 of the second negative electrode active material is 9.5 μm-18.5 μm, and optionally 9.5-14.6 μm.

For example, the volume average particle size Dv50 of the second negative electrode active material is 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 14.6 μm, 15 μm, 15.5μm, 16μm, 16.5μm, 17μm, 17.5μm, 18μm, 18.5μm or any range of two of the above values.

The volume average particle size Dv50 of the second negative electrode active material is between 9.5 μm and 18.5 μm, which can make the pores of the second negative electrode film 11222 more abundant, which is beneficial to improving the fast charging capability of the battery cell 10 and reducing the expansion of the negative electrode film 1122 during the charging process.

In some embodiments, the first negative electrode active material comprises graphite particles, wherein the volume average particle size Dv50 of the graphite particles in the first negative electrode film layer 11221 is 7.8 μm to 14.3 μm, optionally 7.8 μm to 11.3 μm. Optionally, the first negative electrode active material comprises artificial graphite.

The second negative electrode active material includes graphite particles with a volume average particle size Dv50 of 9.5 μm to 18.5 μm, optionally from 9.5 μm to 14.6 μm. Optionally, the second negative electrode active material includes natural graphite.

In some embodiments, the specific surface area of the negative electrode active material is 0.5 ^m² /g to 3 ^m² /g, and optionally 0.6 ^m² /g to ^{1.2 m²} /g. For example, the specific surface area of the negative electrode active material is 0.5 ^m²/ g, ^{0.6 m²} /g, 0.7 m²/g, 0.8 ^m² /g, 0.9 ^m² /g, 1.0 ^m² /g, 1.1 ^m² /g, 1.2 ^m² /g, ^{1.3 m²} /g, ^{1.4 m²} /g, 1.5 m² ^/ g, 1.6 ^m² /g, 1.7 ^m² /g ^, 1.8 ^m² /g, 1.9 ^m² /g, ^2.0 m²/g, 2.1 ^m² /g, 2.2 ^m² /g, 2.3 m²/g, ^{2.4 m²} /g, ^2.5 m²/g, 2.6 m²/g, 2.7 ^m² /g ^, 2.8 ^m² /g, 2.9 m²/g, and 3.0 ^m² /g ^. /g or a range consisting of any two of the above values.

The specific surface area of a material is a well-known concept in the art and can be tested using equipment and methods known in the art. For example, it can be tested according to the testing standard GB/T 19587-2017, using the negative electrode active material as a sample and testing the specific surface area using a Tri-Star 3020 specific surface area and pore size analyzer from Micromeritics, Inc.

In this embodiment, the specific surface area of the negative electrode active material is limited to greater than or equal to 0.5 ^m² /g, which can improve the fast charging capability of the battery cell 10; the specific surface area of the negative electrode active material is limited to less than or equal to 3 ^m² /g, which can reduce the side reactions of the battery cell 10 during storage, slow down the expansion of the negative electrode sheet, and reduce the expansion pressure.

In some embodiments, the compaction density of the positive electrode film layer 1112 at 100% SOC of the battery cell is 2.50 g/ ^cm³ to 2.80 g/ ^cm³ ; optionally, it is 2.55 g/ ^cm³ to 2.70 g/ ^cm³ . For example, when the battery cell 10 is at 100% state of charge (SOC), the compaction density of the positive electrode film layer 1112 is 2.50 g/ ^cm³ , 2.52 g/ ^cm³ , 2.55 g/ ^cm³ , 2.56 g/ ^cm³ , ^2.57 g/ ^cm³ , 2.58 g/ ^cm³ , 2.60 g/ ^cm³ , 2.62 g/ ^cm³ , 2.65 g/ ^cm³ , 2.68 g/cm³, 2.30 g/ ^cm³ , 2.32 g/ ^cm³ , 2.75 g/ ^cm³ , 2.78 g/ ^cm³ , 2.80 g/ ^cm³ , or any two of the above values.

When the compaction density of the positive electrode film layer 1112 is within the above range, it is beneficial to improve the energy density of the battery cell 10; and since the positive electrode active material in the positive electrode film layer 1112 is packed more tightly and the contact resistance between particles is smaller, it can further reduce the resistance of the positive electrode sheet 111, thereby reducing the heat generation under fast charging.

In this embodiment, the compaction density of the positive electrode film 1112 at 100% SOC of the battery cell is a term known in the art, meaning that the positive electrode sheet 111 is separated from the battery cell 10 at 100% SOC, and the compaction density of the positive electrode film 1112 is measured. Exemplarily, the method for testing the compaction density of the positive electrode film 1112 can be the same as the method for testing the compaction density of the negative electrode film 1122.

In some embodiments, the coating weight of the positive electrode film 1112 on one side is 200mg/1540mm² ^- 370mg/ ^1540mm² ; optionally, ^it is 240mg/1540mm² to 330mg/ ^1540mm² . For example, the single-sided coating weight of the positive electrode film layer 1112 is 200mg/1540.25mm², ^210mg / ^1540.25mm² , ^220mg /1540.25mm², 230mg/1540.25mm² ^{, 240mg} /1540.25mm² ^, 250mg/1540.25mm², 260mg/1540.25mm², ^{270mg /} 1540.25mm², ^280mg /1540.25mm², 290mg/1540.25mm², ^{or 300mg} /1540.25mm². 310mg/1540.25mm², ^320mg /1540.25mm² ^, 330mg/1540.25mm² ^, 340mg/1540.25mm² ^, 350mg/1540.25mm² ^, 360mg/1540.25mm² ^, 370mg/1540.25mm² ^, or a range consisting of any two of the above values.

In the embodiments of this application, the single-sided coating weight of the positive electrode film layer 1112 has a meaning known in the art and can be detected using equipment and methods known in the art, such as the single-sided coating weight test method of the negative electrode film layer 1122 described above.

Setting the single-sided coating weight of the positive electrode film 1112 to 200mg/1540mm² ^- 370mg/ ^1540mm² can limit the heat generation per unit area of the positive electrode sheet 111, while also improving the energy density and charging rate performance of the battery cell 10.

In some embodiments, the porosity of the positive electrode 111 is 25%-32%. As an example, the porosity of the positive electrode 111 may be 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, or any combination of two of the above values.

In the embodiments of this application, the porosity of the positive electrode 111 has a meaning known in the art and can be detected using equipment and methods known in the art, such as the porosity testing method for the negative electrode 112.

The porosity of the positive electrode 111 is greater than or equal to 25%, which provides space for impurities generated by side reactions in the positive electrode 111, reduces the expansion pressure of the battery cell 10, reduces the deformation of the battery cell 10, improves the cycle performance of the battery cell 10, and reduces the risk of connection failure between the battery cell and the busbar component. The porosity of the positive electrode 111 is less than or equal to 32%, which can, to some extent, maintain the energy density of the battery cell 10.

In some embodiments, the thickness of the positive electrode 111 may be 0.13mm-0.2mm. As an example, the thickness of the positive electrode 111 may be 0.13mm, 0.14mm, 0.15mm, 0.16mm, 0.17mm, 0.18mm, 0.19mm, 0.2mm or any range of two of the above values.

In the embodiments of this application, the thickness of the positive electrode 111 has a meaning known in the art and can be detected using equipment and methods known in the art, such as measuring the thickness of the positive electrode 111 using a micrometer.

By using a positive electrode 111 with a smaller thickness, the ion migration path can be shortened, the ion migration rate can be increased, the heat generation of the battery cell 10 can be reduced, and the fast charging performance of the battery cell 10 can be improved.

In some embodiments, the ratio of the thickness of the positive current collector 1111 to the thickness of the positive electrode film 1112 is 0.05 to 0.3. Exemplarily, in an embodiment of this application, the thickness of the positive electrode film 1112 is the thickness of the positive electrode film 1112 located on one side of the positive current collector 1111.

For example, the ratio of the thickness of the positive current collector 1111 to the thickness of the positive electrode film layer 1112 is 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.12, 0.15, 0.18, 0.2, 0.22, 0.25, 0.28, 0.3 or any two of the above values.

Limiting the ratio of the thickness of the positive current collector 1111 to the thickness of the positive electrode film 1112 to greater than or equal to 0.05 can improve the current-carrying capacity of the positive current collector 1111, reduce the temperature rise of the positive electrode sheet 111, and improve the fast-charging performance of the battery cell 10. Limiting the ratio of the thickness of the positive current collector 1111 to the thickness of the positive electrode film 1112 to less than or equal to 0.3 can reduce the capacity loss of the positive electrode sheet 111. In this embodiment, the ratio of the thickness of the positive current collector 1111 to the thickness of the positive electrode film 1112 is limited to 0.05 to 0.3, which can, to a certain extent, balance the fast-charging capability and energy density of the battery cell 10.

The thickness of the positive electrode film and the thickness of the positive electrode current collector have meanings known in the art and can be adopted using methods known in the art. The equipment and methods are used for testing. For example, the thickness of the positive electrode sheet is measured with a micrometer, the film layer on the surface of the positive electrode current collector is removed, and the thickness of the positive electrode current collector is measured with a micrometer. When the positive electrode film layer is coated on one side, the thickness of the positive electrode film layer is the thickness of the positive electrode sheet minus the thickness of the positive electrode current collector. When the positive electrode film layer is coated on both sides, the thickness of the positive electrode film layer is: (thickness of the positive electrode sheet minus the thickness of the positive electrode current collector)/2.

In some embodiments, the thickness of the positive electrode current collector 1111 is 10 μm to 15 μm, optionally 12 μm to 15 μm. Exemplarily, the thickness of the positive electrode current collector 1111 is 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, or any combination of two of the above values. When the thickness of the positive electrode current collector 1111 is within the above range, the current-carrying capacity of the positive electrode current collector 1111 is superior, and the battery cell 10 can have a higher energy density.

In some embodiments, a portion of the positive current collector 1111 is not covered by the positive electrode film layer 1112; the portion of the positive current collector 1111 not covered by the positive electrode film layer 1112 can be used to form the positive electrode tab 11b.

In some embodiments, the positive electrode active material includes a lithium phosphate with an olivine structure or a modified version thereof.

The lithium-containing phosphate with an olivine structure or its modified material can be either an olivine-structured lithium-containing phosphate or a material obtained by coating and modifying it. For example, an olivine-structured lithium-containing phosphate includes phosphate particles and an ion-conducting layer, wherein the ion-conducting layer is coated on the surface of the phosphate particles and contains one or more elements selected from C, Fe, Ti, Zr, Hf, Ge, and Sn.

In some embodiments, the mass percentage of olivine-structured lithium phosphate or its modified material in the positive electrode active material may be greater than or equal to 80% and less than or equal to 100%, and the positive electrode active material of this application can be considered as an olivine-structured lithium phosphate or its modified material system. When the mass percentage of olivine-structured lithium phosphate or its modified material is less than 100%, the positive electrode active material may also include commonly used positive electrode active materials, such as, but not limited to, at least one of lithium transition metal oxides. Examples of lithium transition metal oxides may include, but are not limited to, at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds.

Optionally, the positive electrode active material comprises 100% by mass of lithium phosphate with an olivine structure or its modified material.

In some embodiments, the volume average particle size of the positive electrode active material satisfies 1μm≤Dv50≤2μm and 0.4μm≤Dv10≤0.7μm.

For example, the Dv50 of the positive electrode active material can be 1 μm, 1.1 μm, 1.15 μm, 1.2 μm, 1.25 μm, 1.3 μm, 1.35 μm, 1.4 μm, 1.45 μm, 1.5 μm, 1.55 μm, 1.6 μm, 1.65 μm, 1.7 μm, 1.75 μm, 1.8 μm, 1.85 μm, 1.9 μm, 1.95 μm, 2 μm, or any range of two of the above values.

For example, the Dv10 of the positive electrode active material can be 0.4 μm, 0.45 μm, 0.5 μm, 0.55 μm, 0.6 μm, 0.65 μm, 0.7 μm, or any combination of two of the above values.

The particle size of the positive electrode active material is relatively small, the lithium ion insertion and extraction path in the positive electrode active material is shorter, and the heat generation is less; moreover, the particle size of the above positive electrode active material is not too small, which can reduce agglomeration during the processing and preparation process, so as to make the performance of the positive electrode active material stable.

The volume average particle size (Dv50) of a material refers to the particle size corresponding to 50% of its volume distribution, and the volume average particle size (Dv10) refers to the particle size corresponding to 10% of its volume distribution. Both can be detected using equipment and methods known in the art. For example, using the positive electrode active material as a sample, and according to the testing standard GB/T 19077-2016, the particle size can be measured using a Mastersizer. The 2000E laser particle size analyzer tests particle Dv50 and Dv10, etc.

In some embodiments, the battery cell 10 includes an electrolyte contained within the housing 12. During the charging and discharging process of the battery cell 10, active ions are inserted and extracted back and forth between the positive electrode 111 and the negative electrode 112, and the electrolyte plays a role in conducting active ions between the positive electrode 111 and the negative electrode 112.

In some embodiments, the conductivity of the electrolyte at room temperature is from 13 mS/cm to 20 mS/cm, optionally from 15 mS/cm to 20 mS/cm. Exemplarily, the conductivity of the electrolyte at room temperature is 13 mS/cm, 13.5 mS/cm, 14 mS/cm, 14.5 mS/cm, 15 mS/cm, 15.5 mS/cm, 16 mS/cm, 16.5 mS/cm, 17 mS/cm, 17.5 mS/cm, 18 mS/cm, 18.5 mS/cm, 19 mS/cm, 19.5 mS/cm, 20 mS/cm, or any range of two of the above values.

As an example, the room temperature could be 25°C.

When the conductivity of the electrolyte is within the above range, the migration rate of ions in the electrolyte is relatively high, thereby further reducing the internal resistance of the battery cell 10, reducing heat generation, and improving the fast charging performance of the battery cell 10.

The conductivity of the electrolyte is the ionic conductivity, which can be detected using equipment and methods known in the art, such as by referring to industry standard HG-T 4067-2015.

In some embodiments, the density ρ of the electrolyte at room temperature satisfies: 1.05 g/mL ≤ ρ ≤ 1.35 g/mL.

For example, the density ρ of the electrolyte is 1.05 g/mL, 1.10 g/mL, 1.15 g/mL, 1.2 g/mL, 1.25 g/mL, 1.3 g/mL, 1.35 g/mL, or a range of any two of the above values.

When the electrolyte density ρ is within the above range, the migration rate of lithium ions in the electrolyte is relatively high, which can further reduce the internal resistance of the battery cell 10, thereby reducing heat generation and improving the fast charging performance of the battery cell 10.

In the embodiments of this application, the density of the electrolyte has a meaning known in the art and can be detected using equipment and methods known in the art, such as referring to GB/T 2013-2010 for testing.

In some embodiments, the electrolyte comprises an organic solvent, which includes one or more of carbonate solvents and carboxylic acid ester solvents.

In some embodiments, the carboxylic acid ester solvent includes a chain-like carboxylic acid ester solvent, wherein the chain-like carboxylic acid ester solvent comprises 5% to 75% by mass of the organic solvent. Exemplarily, the mass content of the chain-like carboxylic acid ester solvent is 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, or a range consisting of any two of the above values. When the mass content of the chain-like carboxylic acid ester solvent is within the above range, the viscosity of the electrolyte system is relatively low, which is beneficial for lithium ion migration.

In some embodiments, the chain carboxylic acid ester solvent has a mass content of 30% to 70% in the organic solvent.

In some embodiments, the carboxylic acid ester comprises _R1 -COO- _R2 , where _R1 and _R2 each independently comprise an alkyl group having 1-5 carbon atoms or a haloalkyl group having 1-5 carbon atoms. The aforementioned chain-like carboxylic acid ester solvents have high conductivity, which is beneficial for improving the fast-charging capability of the battery cell 10.

In some embodiments, carbonate solvents include one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

Further optionally, the carbonate solvent includes one or more of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate.

The combined use of the aforementioned carbonate solvents and chain carboxylic acid ester solvents improves the conductivity of the electrolyte, which is beneficial for lithium ion migration.

Further optionally, the carbonate solvent in the organic solvent has a mass content of 5% to 95%, optionally 25% to 60%, and optionally 30% to 45%. Exemplarily, the mass content of the carbonate solvent in the organic solvent is 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 40%, 45%, 48%, 50%, 55%, 60%, or any combination of two of the above values. The carbonate solvent at the above mass contents can further improve the conductivity of the electrolyte, which is beneficial for lithium ion migration.

For example, the carbonate solvent includes one or more of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, and the carbonate solvent content is 25% to 60% by mass.

The use of organic solvents can improve the conductivity of the electrolyte and reduce its viscosity, thereby improving the fast charging performance of the battery.

In some embodiments, the electrolyte comprises a lithium salt. The lithium salt includes one or more of fluorosulfonyl imide salts and lithium hexafluorophosphate (LiPF6). The above-mentioned lithium salts are readily dissociated, which is beneficial for the rapid migration of lithium ions; and the electrolyte system is relatively stable and not easily decomposed, which can improve the cycle performance of the battery cell 10.

Optionally, the fluorosulfonyl imide salt includes one or more of lithium bisfluorosulfonyl imide (LiFSI) and lithium bistrifluoromethanesulfonate (LiTFSI).

In some embodiments, the lithium salt comprises lithium bis(fluorosulfonyl)imide (LiFSI) and lithium hexafluorophosphate (LiPF6 ₎ , wherein the molar concentration of lithium bis(fluorosulfonyl)imide (LiFSI) is 0.2 mol/L to 0.5 mol/L, and the molar concentration of lithium hexafluorophosphate (LiPF6 ₎ is 0.5 mol/L to 1.0 mol/L. Exemplarily, the molar concentration of lithium bis(fluorosulfonyl)imide (LiFSI) is 0.4 mol/L to 0.5 mol/L, and the molar concentration of lithium hexafluorophosphate (LiPF6 ₎ is 0.7 mol/L. Exemplarily, the molar concentration of lithium bis(fluorosulfonyl)imide (LiFSI) is 0.5 mol/L, and the molar concentration of lithium hexafluorophosphate (LiPF6 ₎ is 0.5 mol/L. Exemplarily, the molar concentration of lithium bis(fluorosulfonyl)imide (LiFSI) is 0.2 mol/L, and the molar concentration of lithium hexafluorophosphate (LiPF6 ₎ is 0.8 mol/L.

Optionally, the molar concentration ratio of lithium bis(fluorosulfonyl)imide to lithium hexafluorophosphate ( _LiPF6 ) is (2 to 5):10. Exemplarily, the molar concentration ratio of lithium bis(fluorosulfonyl)imide to lithium hexafluorophosphate (LiPF6 ₎ is 2:10, 2.5:10, 3:10, 3.5:10, 4:10, 4.5:10, 5:10, or a range of any two of the above values.

In some embodiments, the electrode assembly 11 has a dimension of T along the thickness direction X, the thickness of the single-layer negative electrode 112 is T1, and the number of layers of the negative electrode 112 stacked in the thickness direction X is N. T, T1, and N satisfy: 0.3≤(N×T1)/T≤0.5.

The negative electrode 112 includes at least one flat layer 112a perpendicular to the thickness direction X. In the electrode assembly 11, the number of flat layers 112a is N.

For example, the battery cell 10 is disassembled at 0% charge and the electrode assembly 11 is removed; T and T1 are measured using a micrometer.

For example, the electrode assembly 11 is a wound structure, and the negative electrode 112 includes N flat layers 112a; alternatively, the electrode assembly 11 is a stacked structure, and the electrode assembly 11 includes N negative electrode 112, each negative electrode 112 including a flat layer 112a.

During the cycling process of the battery cell 10, the negative electrode 112 will increase in thickness due to irreversible side reactions, thereby causing the battery cell 10 to expand. Limiting (N×T1)/T to 0.3-0.5 can reduce the expansion of the battery cell 10 and reduce the risk of connection failure between the battery cell 10 and the busbar component 30.

In some embodiments, the limiting beam 21 is a one-piece molded structure, which can reduce the weak connection of the limiting beam 21. This design improves the structural strength and stiffness of the limiting beam 21. Alternatively, the limiting beam 21 can be assembled from multiple components, for example, by welding together multiple sheet metal parts.

In some embodiments, the limiting beam 21 is a profile beam.

The limiting beam 21 can be a hollow beam structure integrally formed from a plate or rod through processes such as stamping/extrusion or metal casting. The wall thickness of the limiting beam 21 can be 1mm-8mm depending on actual needs, with 3mm-5mm being the most common. At this wall thickness, the limiting beam 21 has a good cost-performance ratio, achieving both light weight and good structural strength, effectively suppressing the expansion and deformation of the battery cell 10 during cycling.

The limiting beam 21 may be made of materials such as steel, iron, aluminum and aluminum alloys, but is not limited to steel.

In some embodiments, the housing 20 includes a frame 22 and a support beam 23. The frame 22 defines an accommodating space, and a limiting beam 21 and a plurality of battery cells 10 are disposed in the accommodating space. The support beam 23 is disposed on the side of the limiting beam 21 opposite to the plurality of battery cells 10 and connects the frame 22 and the limiting beam 21.

Optionally, the frame 22 can be a rectangular frame.

There can be one or more support beams 23.

For two adjacent limiting beams 21, one limiting beam 21 can be connected to the support beam 23, or both limiting beams 21 can be connected to the support beam 23.

During the cycle of battery 2, the limiting beam 21 is used to resist the expansion force of battery cell 10 during the cycle. The frame 22 can support the limiting beam 21 through the support beam 23, thereby providing effective support for the limiting beam 21, reducing the deformation of the limiting beam 21, and thus providing constraint to battery cell 10, reducing the expansion of battery cell 10, and improving the cycle life of battery cell 10.

By setting the supporting force between the connecting frame 22 and the limiting beam 21, the overall structural strength and rigidity of the box 20 can be improved, and the risk of cracking of the box 20 can be reduced.

In some embodiments, the frame 22 includes a plurality of side beams, which are arranged and connected in sequence to form an annular frame 22.

In some embodiments, the support beam 23 extends along the thickness direction X. Optionally, the cross-section of the support beam 23 perpendicular to the thickness direction X may be rectangular, trapezoidal, elliptical, circular, L-shaped, or other shapes.

In some embodiments, the support beam 23 is a plate or hollow beam structure. The support beam 23 may be made of steel, aluminum, or aluminum alloy.

In some embodiments, the support beam 23 and the frame 22 can be fixedly connected by welding, bolting, or snap-fitting.

In some embodiments, the limiting beam 21 extends in a direction perpendicular to the thickness direction X. The housing 20 includes a plurality of support beams 23 spaced apart along the width direction Y of the limiting beam 21. The plurality of support beams 23 can increase the constraint force on the limiting beam 21, improve the uniformity of force on different areas of the limiting beam 21, reduce the deformation of the limiting beam 21 during the cycling process of the battery cell 10, and improve the cycle performance of the battery 2.

In some embodiments, the housing 20 further includes a support plate 24, with a plurality of battery cells 10 and a limiting beam 21 located on the same side of the support plate 24 and fixed to the support plate 24. Exemplarily, the support plate 24 and the plurality of battery cells 10 are arranged along the height direction Z of the battery cells 10.

In some embodiments, the housing 20 further includes a cover plate (not shown), which is disposed opposite to the support plate 24 along the height direction Z and fixed to the frame 22. The battery cell and the limiting beam are located between the cover plate and the support plate.

In some examples, the support plate 24 is located on top of the battery cell, which is inverted; alternatively, in other examples, the support plate 24 is located on the bottom of the battery cell, which is upright.

Figure 13 is a top view of a battery provided in some other embodiments of this application; Figure 14 is an enlarged view of Figure 13 at the box; Figure 15 is a structural schematic diagram of the second busbar in Figure 14.

Referring to Figures 6 and 13-15, in some embodiments, the battery 2 further includes at least one second busbar component 30b. The second busbar component 30b has a single-layer structure and is electrically connected to at least two battery cells 10. The thickness of the second busbar component 30b is greater than the thickness of the first busbar layer 31, and the thickness of the second busbar component 30b is greater than the thickness of the second busbar layer 32.

For example, among the plurality of bus components 30, a portion of the bus components 30 is a first bus component 30a, and another portion of the bus components 30 is a second bus component 30b.

In battery 2, the expansion amount of battery cells 10 at different locations may vary. For battery cells 10 with smaller expansion amounts, a second busbar component 30b with a single-layer structure can be used; compared to the first busbar component 30a, the second busbar component 30b has a simpler structure, is easier to manufacture, and can save costs. The thickness of the second busbar component 30b is greater than the thickness of the first busbar layer 31 and the thickness of the second busbar layer 32, and its current carrying capacity meets the requirements.

In some embodiments, the sum of the thickness of the first busbar 31 and the thickness of the second busbar 32 is equal to the thickness of the second busbar component 30b. Embodiments of this application can reduce the difference in current-carrying capacity between the first busbar component 30a and the second busbar component 30b, thereby improving current consistency.

In some embodiments, the second busbar 30b connects at least two battery cells 10 arranged along the thickness direction X.

In some embodiments, among a plurality of battery cells 10, the outermost battery cell 10 along the thickness direction X is connected to the first busbar 30a.

During charging, the expansion of multiple battery cells 10 may overlap in the thickness direction X, which causes a large displacement of the outermost battery cell 10 in the thickness direction X. Using a first busbar 30a with a double-layer structure to connect the outermost battery cell 10 can reduce the risk of connection failure between the first busbar 30a and the battery cell 10.

For example, the outermost battery cell 10 along the thickness direction X is connected to the first busbar layer 31.

In some embodiments, the battery cell 10 adjacent to the limiting beam 21 may be connected to the first busbar 30a.

In some embodiments, the plurality of busbar components 30 may further include a third busbar component 30c, which may connect two adjacent battery cells 10 along the width direction Y.

In some embodiments, in an external environment of 25°C to 35°C, the charging time for battery cell 10 from 10% SOC to 80% SOC is 5 minutes to 10.5 minutes. Optionally, in an external environment of 25°C to 35°C, the charging time for battery cell 10 from 10% SOC to 80% SOC may be 5 minutes to 10.5 minutes. Exemplarily, the charging time for battery cell 10 from 10% SOC to 80% SOC is 10.5 minutes, 10 minutes, 9.5 minutes, 9 minutes, 8.5 minutes, 8 minutes, 7.5 minutes, 7 minutes, 6.5 minutes, 6 minutes, 5.5 minutes, 5 minutes, or a range of any two of the above values.

The battery cell 10 in this embodiment has fast charging capability, which can save charging time.

In some embodiments, the charging steps of the battery 2 or any of the battery cells 10 comprising the battery 2 from 10% to 80% can be performed as follows:

Charge from 10% SOC to 15% SOC at a constant current of 5.0C;

Charge from 15% SOC to 20% SOC at a constant current of 5.0C;

Charge from 20% SOC to 25% SOC at a constant current of 5.0C;

Charge from 25% SOC to 30% SOC at a constant current of 5.0C;

Charge from 30% SOC to 35% SOC at a constant current of 5.0C;

Charge from 35% SOC to 40% SOC at a constant current of 5.0C;

Charge from 40% SOC to 45% SOC at a constant current of 4.6C;

Charge from 45% SOC to 50% SOC at a constant current of 4.3C;

Charge from 50% SOC to 55% SOC at a constant current of 4.0C;

Charge from 55% SOC to 60% SOC at a constant current of 3.7C;

Charge from 60% SOC to 65% SOC at a constant current of 3.4C;

Charge from 65% SOC to 70% SOC at a constant current of 3.1C;

Charge from 70% SOC to 75% SOC at a constant current of 2.9C;

Charge from 75% SOC to 80% SOC at a constant current of 2.7C.

As an example, the above charging strategy is carried out in an environment of 30°C.

In some embodiments, the charging step of the battery cell 10 from 0% SOC to 10% SOC can be performed as follows: charging from 0% SOC to 10% SOC at a constant current of 5.0C.

In some embodiments, the charging step of the battery cell 10 from 80% SOC to 98% SOC can be performed as follows:

Charge from 80% SOC to 85% SOC at a constant current of 1.8C;

Charge from 85% SOC to 90% SOC at a constant current of 1.3C;

Charge from 90% SOC to 95% SOC at a constant current of 0.7C;

Charge from 95% SOC to 98% SOC at a constant current of 0.33C.

In some embodiments, the charging step of the battery cell 10 from 98% SOC to 100% SOC can be performed as follows: charging from 98% SOC to 100% SOC at a constant current of 0.01C, 0.05C, 0.1C, or 0.3C. Optionally, the charging step of the battery cell 10 from 98% SOC to 100% SOC can be performed as follows: charging from 98% SOC to 100% SOC at a constant current of 0.01C, 0.05C, or 0.1C.

In some embodiments, during the charging process of battery cell 10 from 10% SOC to 80% SOC, the charging current can be 2C-6C, optionally 2.7C-5C. The charging current of battery cell 10 can vary according to the SOC of battery cell 10 during charging.

In some embodiments, the battery cell 10 is a lithium-ion battery cell. After cycling the battery cell 10 20 times according to the charging and discharging strategies, the negative electrode sheet of the battery cell 10 is disassembled, and the lithium plating area of the negative electrode sheet is observed and measured. The ratio of the area of the lithium plating region to the total area of the negative electrode sheet is less than 2%.

As an example, the discharge strategy employs a constant current discharge of 0.33C to 2.0V.

As an example, a charging strategy could be:

Charge from 0% SOC to 5% SOC at a constant current of 5.0C;

Charge from 5% SOC to 10% SOC at a constant current of 5.0C;

Charge from 10% SOC to 15% SOC at a constant current of 5.0C;

Charge from 15% SOC to 20% SOC at a constant current of 5.0C;

Charge from 20% SOC to 25% SOC at a constant current of 5.0C;

Charge from 25% SOC to 30% SOC at a constant current of 5.0C;

Charge from 30% SOC to 35% SOC at a constant current of 5.0C;

Charge from 35% SOC to 40% SOC at a constant current of 5.0C;

Charge from 40% SOC to 45% SOC at a constant current of 4.6C;

Charge from 45% SOC to 50% SOC at a constant current of 4.3C;

Charge from 50% SOC to 55% SOC at a constant current of 4.0C;

Charge from 55% SOC to 60% SOC at a constant current of 3.7C;

Charge from 60% SOC to 65% SOC at a constant current of 3.4C;

Charge from 65% SOC to 70% SOC at a constant current of 3.1C;

Charge from 70% SOC to 75% SOC at a constant current of 2.9C;

Charge from 75% SOC to 80% SOC at a constant current of 2.7C;

Charge from 80% SOC to 85% SOC at a constant current of 1.8C;

Charge from 85% SOC to 90% SOC at a constant current of 1.3C;

Charge from 90% SOC to 95% SOC at a constant current of 0.7C;

Charge from 95% SOC to 98% SOC at a constant current of 0.33C;

Charge from 98% SOC to 100% SOC at a constant current of 0.1C.

The battery cell 10 of this embodiment can be charged from 10% SOC to 80% SOC in 10.5 minutes without lithium plating or with only slight lithium plating, demonstrating good fast charging capability. For example, a ratio of the area of the lithium plating region to the total area of the negative electrode sheet of less than 0.05% can be considered as no lithium plating, and a ratio of the area of the lithium plating region to the total area of the negative electrode sheet of less than 2% and greater than or equal to 0.05% can be considered as slight lithium plating.

According to some embodiments of this application, this application also provides an electrical device, including a battery 2 from any of the above embodiments, wherein the battery 2 is used to provide electrical energy to the electrical device. The electrical device can be any of the aforementioned devices or systems that utilize the battery 2.

Referring to Figures 2 to 12, an embodiment of this application provides a battery 2, which includes a plurality of battery cells 10, a housing 20, and a plurality of busbar components 30. The plurality of battery cells 10 are housed within the housing 20.

The battery cell 10 includes a housing 12 and an electrode assembly 11 housed within the housing 12. The expansion pressure of the battery cell in the thickness direction X is 0.5 MPa-2.4 MPa.

The electrode assembly 11 includes a positive electrode 111, a negative electrode 112, and a separator 113, which separates the positive electrode 111 and the negative electrode 112. Optionally, the positive electrode 111, the negative electrode 112, and the separator 113 are wound together.

The negative electrode 112 includes a negative electrode current collector 1121 and a negative electrode film layer 1122 disposed on at least one side of the negative electrode current collector 1121, the negative electrode film layer 1122 including a negative electrode active material. The porosity of the negative electrode 112 is 27%-40%. The compaction density of the negative electrode film layer 1122 at 100% SOC of the battery cell is 1.15 g/ ^cm³ to 1.36 g/ ^cm³ .

The negative electrode film layer 1122 includes a first negative electrode film layer 11221 and a second negative electrode film layer 11222, wherein the second negative electrode film layer 11222 is disposed between the first negative electrode film layer 11221 and the negative electrode current collector 1121. The negative electrode active material includes a first negative electrode active material disposed in the first negative electrode film layer 11221 and a second negative electrode active material disposed in the second negative electrode film layer 11222. The first negative electrode active material includes artificial graphite, and the second negative electrode active material includes artificial graphite, natural graphite, and... One or more silicon-based materials. The volume average particle size Dv50 of the first negative electrode active material is less than or equal to the volume average particle size Dv50 of the second negative electrode active material.

The positive electrode 111 includes a positive current collector 1111 and a positive electrode film 1112 disposed on at least one side of the positive current collector 1111. The compaction density of the positive electrode film 1112 at 100% SOC of the battery cell is 2.50 g/ ^cm³ to 2.80 g/ ^cm³ . The porosity of the positive electrode 111 is 25%-32%. The ratio of the thickness of the positive current collector 1111 to the thickness of the positive electrode film 1112 is 0.05 to 0.3. The positive electrode active material includes a lithium phosphate with an olivine structure or a modified material thereof. The volume average particle size of the positive electrode active material satisfies 1 μm ≤ Dv50 ≤ 2 μm and 0.4 μm ≤ Dv10 ≤ 0.7 μm.

The housing 20 includes two limiting beams 21, which are spaced apart along the thickness direction X of the battery cells 10. Multiple battery cells 10 are arranged in an array to form multiple battery cell rows 100, which are arranged along the width direction Y of the limiting beams 21. Each battery cell row 100 includes at least two battery cells 10 arranged along the thickness direction X of the battery cells 10. The multiple battery cells 10 are arranged between the two limiting beams 21.

The housing 20 includes a frame 22 and a support beam 23. The frame 22 defines an accommodating space, and a limiting beam 21 and multiple battery cells 10 are disposed within the accommodating space. The support beam 23 is disposed on the side of the limiting beam 21 opposite to the multiple battery cells 10 and connects the frame 22 and the limiting beam 21. A constraint member 40 connects adjacent limiting beams 21 and is bonded to the battery cells 10.

Multiple busbars 30 electrically connect multiple battery cells 10. The multiple busbars 30 include at least one first busbar 30a, the first busbar 30a including a first busbar layer 31 and a second busbar layer 32 stacked and connected, the first busbar layer 31 connecting at least two battery cells 10 disposed along the thickness direction X.

Example

The following embodiments describe the contents disclosed in this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of the embodiments of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

Example 1

1. Preparation of positive electrode sheet

The positive electrode includes a positive current collector and a positive film layer disposed on both sides of the positive current collector. The positive current collector is an aluminum foil with a thickness of 15μm.

The positive electrode film layer comprises a film layer formed by uniformly coating a positive electrode slurry (solvent being N-methylpyrrolidone, NMP) onto the surface of a positive electrode conductive layer, followed by drying and cold pressing. The positive electrode film layer comprises positive electrode active material, binder polyvinylidene fluoride (PVDF), and conductive agent acetylene black in a weight ratio of 97:2:1.

The positive electrode active material includes lithium iron phosphate and an ion-conducting layer. The ion-conducting layer is coated on the surface of the _lithium iron phosphate and consists of lithium titanium iron phosphate (Li₂FeTi( _PO₄ ) _₃ ) and amorphous carbon. The Dv50 of the positive electrode active material is 1.6 μm, and the Dv10 is 0.64 μm.

The single-sided coating weight of the positive electrode film is 0.21g/ ^1540.25mm² , and the compaction density of the positive electrode film after cold pressing is 2.6g/ ^cm³ .

2. Preparation of negative electrode sheet

The negative electrode includes a negative current collector and a negative electrode film layer disposed on both sides of the negative current collector. The negative current collector is thick. Copper foil with a thickness of 6μm.

The negative electrode film layer comprises a film layer formed by uniformly coating a negative electrode slurry (with deionized water as the solvent) onto the surface of a negative electrode conductive layer, followed by drying and cold pressing.

The single-sided coating weight of the negative electrode film is 0.096g/ ^1540.25mm² , and the compaction density of the negative electrode film after cold pressing is 1.6g/ ^cm³ .

The negative electrode film layer includes a first negative electrode film layer and a second negative electrode film layer, with the second negative electrode film layer located between the first negative electrode film layer and the negative electrode current collector.

The second negative electrode film layer comprises graphite particles in a mass ratio of 96.5:0.5:0.5:1.5:1, conductive agent acetylene black, a second lithium-containing binder (lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, wherein the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and hydroxyethyl acrylate monomer is 35%:30%:15%:20%), negative electrode binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose. The lithium content in the second lithium-containing binder is 4.8% by mass. The Dv50 of the graphite particles is 11.3 μm. The graphite particles include artificial graphite and a carbon coating layer. The carbon coating layer coats the surface of the artificial graphite, and the carbon coating layer has a mass content of 3.5%.

The first negative electrode film layer comprises graphite particles in a mass ratio of 97.5:0.5:0.5:0.5:1, conductive agent acetylene black, a first lithium-containing binder (lithium acrylate-acrylonitrile-acrylamide-hydroxyethyl acrylate copolymer, wherein the molar ratio of lithium acrylate monomer, acrylonitrile monomer, acrylamide monomer and hydroxyethyl acrylate monomer is 35%:30%:15%:20%), negative electrode binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose. The lithium content in the first lithium-containing binder is 4.8% by mass. The Dv50 of the graphite particles is 11.3 μm. The graphite particles include artificial graphite and a carbon coating layer. The carbon coating layer coats the surface of the artificial graphite, and the carbon coating layer has a mass content of 3.5%.

3. Separating membrane

The separator includes a base membrane, which is a 7μm polyethylene film layer with a porosity of 42%.

4. Preparation of electrolyte

The electrolyte consists of organic solvents, lithium salts, and additives.

The organic solvents consist of 60% chain carboxylic acid ester solvents (ethyl acetate) and 40% carbonate solvents (30% ethylene carbonate EC, the remainder being dimethyl carbonate). The mass content of each component in the organic solvents is calculated based on the mass of the organic solvents.

Based on the mass of the electrolyte, the additive content is 6.5%, which includes vinylene carbonate (VC), fluoroethylene carbonate (FEC), vinyl sulfite (ES), and lithium difluorooxalate borate (LiDFOB) in a mass ratio of 5:0.5:0.5:0.5.

The lithium salts include 1 mol/L lithium hexafluorophosphate (LiPF6 ₎ .

The electrolyte has a conductivity of 16.4 mS/cm at room temperature.

5. Preparation of battery cells

The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation, thus obtaining an electrode assembly. The electrode assembly is placed in a housing, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a single battery cell is obtained.

6. Battery manufacturing

Multiple battery cells are installed into a housing, and then multiple busbars are welded to the electrode terminals of the battery cells. High and low voltage wiring harnesses are then installed to obtain the battery.

The busbar component can be the first busbar component shown in Figure 6, which has a double-layer structure. The thickness Th of the single-layer structure of the flow component is 1.5 mm, that is, the thickness of the first busbar layer is 1.5 mm and the thickness of the second busbar layer is 1.5 mm.

Example 2

Battery cells and batteries were prepared using a method similar to that in Example 1. The difference from Example 1 is that the single-sided coating weight of the positive electrode film, the compaction density of the positive electrode film after cold pressing, the single-sided coating weight of the negative electrode film, and the compaction density of the negative electrode film after cold pressing were adjusted.

Example 3

Battery cells and batteries were prepared using a method similar to that in Example 1. The difference from Example 1 is that the single-sided coating weight of the positive electrode film, the compaction density of the positive electrode film after cold pressing, the single-sided coating weight of the negative electrode film, and the compaction density of the negative electrode film after cold pressing were adjusted.

Example 4

Battery cells and batteries were prepared using a method similar to that in Example 1. The difference from Example 1 is that the single-sided coating weight of the positive electrode film, the compaction density of the positive electrode film after cold pressing, the single-sided coating weight of the negative electrode film, the compaction density of the negative electrode film after cold pressing, and the thickness Th of the single-layer structure of the first busbar were adjusted.

Example 5

Battery cells and batteries were prepared using a method similar to that in Example 1. The difference from Example 1 is that the single-sided coating weight of the positive electrode film, the compaction density of the positive electrode film after cold pressing, the single-sided coating weight of the negative electrode film, the compaction density of the negative electrode film after cold pressing, and the thickness Th of the single-layer structure of the first busbar were adjusted.

Example 6

Battery cells and batteries were prepared using a method similar to that in Example 1. The difference from Example 1 is that the single-sided coating weight of the positive electrode film, the compaction density of the positive electrode film after cold pressing, the single-sided coating weight of the negative electrode film, the compaction density of the negative electrode film after cold pressing, and the thickness Th of the single-layer structure of the first busbar were adjusted.

Example 7

Battery cells and batteries were prepared using a method similar to that in Example 1. The difference from Example 1 is that the single-sided coating weight of the positive electrode film, the compaction density of the positive electrode film after cold pressing, the single-sided coating weight of the negative electrode film, the compaction density of the negative electrode film after cold pressing, and the thickness Th of the single-layer structure of the first busbar were adjusted.

Comparative Example 1

Battery cells and batteries were prepared using a method similar to that in Example 1. The difference from Example 1 was that the single-sided coating weight of the positive electrode film, the single-sided coating weight of the negative electrode film, and the compaction density of the negative electrode film after cold pressing were adjusted.

Comparative Example 2

Battery cells and batteries were prepared using a method similar to that in Example 1. The differences from Example 1 are that the single-sided coating weight of the positive electrode film, the compaction density of the positive electrode film after cold pressing, the single-sided coating weight of the negative electrode film, the compaction density of the negative electrode film after cold pressing, and the thickness Th of the single-layer structure of the first busbar were adjusted.

Comparative Example 3

Battery cells and batteries were prepared using a method similar to that in Example 1. The differences from Example 1 are that the single-sided coating weight of the positive electrode film, the compaction density of the positive electrode film after cold pressing, the single-sided coating weight of the negative electrode film, the compaction density of the negative electrode film after cold pressing, and the thickness Th of the single-layer structure of the first busbar were adjusted.

Comparative Example 4

Battery cells and batteries were prepared using a method similar to that in Example 1. The differences from Example 1 are that the single-sided coating weight of the positive electrode film, the compaction density of the positive electrode film after cold pressing, the single-sided coating weight of the negative electrode film, the compaction density of the negative electrode film after cold pressing, and the thickness Th of the single-layer structure of the first busbar were adjusted.

Performance testing

1. Test the expansion pressure of a single battery cell:

The prepared battery cell was discharged to 2.0V at a constant current discharge rate of 1C at an ambient temperature of 45℃.

The battery cell is clamped between two clamping plates, which are located on both sides of the battery cell along its thickness direction and cover its large surface area.

At an ambient temperature of 45°C, the battery cells were charged to 3.8V at a constant current charging rate of 0.8C, and the pressure exerted by the battery cells on the clamping plate was detected and recorded.

The battery cells were cyclically charged and discharged according to the above charging strategy until the battery cells degraded to 70% SOH (the discharge capacity of the battery cells degraded to 70% of the nominal capacity of the battery cells), and the maximum pressure exerted by the battery cells on the clamping plate was recorded.

The expansion pressure Q of a single battery cell in the thickness direction is calculated as: maximum pressure / large surface area.

2. Volumetric energy density test:

The discharge energy in the first week was tested according to the following steps: At 25°C, the prepared battery cell was charged to 3.8V with a constant current of 0.33C, and then discharged to 2.0V with a constant current of 0.33C. The discharge energy A0 at this time was recorded, in Wh.

Volume of a single battery cell: Use calipers to measure the length, width, and height of the single battery cell (generally calculated based on the outer casing dimensions, excluding the height of the electrode terminals and the insulating film outside the casing), and calculate the volume of the single battery cell V0, in liters (L).

The volumetric energy density of a single battery cell is VED = A0/V0, in Wh/L.

3. Cyclic performance test one:

The battery prepared above was discharged at an ambient temperature of 45°C, and the battery cells were discharged to 2.0V at a constant current discharge rate of 1C.

The battery prepared above was charged at an ambient temperature of 45°C, and the battery cells were charged to 3.8V at a constant current charging rate of 0.8C.

The battery is cycled through charging and discharging according to the above charging strategy until the battery degrades to 70% SOH (battery discharge capacity / battery nominal capacity = 70%).

During the cycle, the highest temperature of the end cap of the battery cell casing is detected, and it is observed whether the weld between the first busbar and the electrode terminal is cracked.

4. Cyclic performance test two:

The battery prepared above was discharged at an ambient temperature of 30°C, with each battery cell discharged at 0.33C. Up to 2.0V;

At an ambient temperature of 30°C, the following charging strategy is used for charging:

Charge from 0% SOC to 5% SOC at a constant current of 5.0C;

Charge from 5% SOC to 10% SOC at a constant current of 5.0C;

Charge from 10% SOC to 15% SOC at a constant current of 5.0C;

Charge from 15% SOC to 20% SOC at a constant current of 5.0C;

Charge from 20% SOC to 25% SOC at a constant current of 5.0C;

Charge from 25% SOC to 30% SOC at a constant current of 5.0C;

Charge from 30% SOC to 35% SOC at a constant current of 5.0C;

Charge from 35% SOC to 40% SOC at a constant current of 5.0C;

Charge from 40% SOC to 45% SOC at a constant current of 4.6C;

Charge from 45% SOC to 50% SOC at a constant current of 4.3C;

Charge from 50% SOC to 55% SOC at a constant current of 4.0C;

Charge from 55% SOC to 60% SOC at a constant current of 3.7C;

Charge from 60% SOC to 65% SOC at a constant current of 3.4C;

Charge from 65% SOC to 70% SOC at a constant current of 3.1C;

Charge from 70% SOC to 75% SOC at a constant current of 2.9C;

Charge from 75% SOC to 80% SOC at a constant current of 2.7C;

Charge from 80% SOC to 85% SOC at a constant current of 1.8C;

Charge from 85% SOC to 90% SOC at a constant current of 1.3C;

Charge from 90% SOC to 95% SOC at a constant current of 0.7C;

Charge from 95% SOC to 98% SOC at a constant current of 0.33C;

Charge from 98% SOC to 100% SOC at a constant current of 0.1C.

The battery is cycled through charging and discharging according to the above charging strategy until the battery degrades to 70% SOH.

During the cycle, the highest temperature of the end cap of the battery cell casing is detected, and it is observed whether the weld between the first busbar and the electrode terminal is cracked.

It should be noted that cycle performance test one and cycle performance test two were conducted on two batteries prepared by the same preparation method.

The test results of Examples 1-7 and Comparative Examples 1-4 are shown in Table 1.

Referring to Comparative Example 1 in Table 1, the single-sided coating weight of the positive electrode film, the compaction density of the positive electrode film after cold pressing, the single-sided coating weight of the negative electrode film, and the compaction density of the negative electrode film after cold pressing are all relatively low. Although the battery cell has a small expansion pressure and the solder joint between the electrode terminal and the first busbar is not easy to crack during cycling, the volumetric energy density of the battery cell is relatively low.

Referring to Examples 1-7 and Comparative Example 1, the embodiments of this application can increase the single-sided coating weight of the positive electrode film, the compaction density of the positive electrode film after cold pressing, the single-sided coating weight of the negative electrode film, and the compaction density of the negative electrode film after cold pressing, so that the volumetric energy density of the battery cell is greater than or equal to 390Wh/L. Although the expansion pressure of the battery cell is not less than 0.5MPa, the combination of the first busbar component with a double-layer structure can reduce the risk of solder cracking caused by the increase in expansion pressure and improve the reliability of the battery. The first busbar component has a double-layer structure and strong current carrying capacity, thereby reducing the heat generation of the first busbar component during cycling, and further reducing the heat conducted to the end cap and electrode assembly, reducing the temperature rise of the battery cell, and improving the cycle performance of the battery.

Referring to Examples 1-7 and Comparative Examples 2-3, the embodiments of this application can limit the expansion pressure of a single cell to no more than 2.4 MPa and enable the volumetric energy density of the single cell to reach 415 Wh/L by adjusting parameters such as the single-sided coating weight of the positive electrode film, the compaction density of the positive electrode film after cold pressing, the single-sided coating weight of the negative electrode film, and the compaction density of the negative electrode film after cold pressing.

By adjusting the thickness of the single-layer structure of the first busbar component, its current-carrying capacity and deformability can be balanced. When the expansion pressure of the battery cell is 0.5MPa-2.4MPa, limiting the thickness of the single-layer structure of the first busbar component to no more than 2.5mm can reduce the risk of the solder joint between the electrode terminals and the first busbar component being torn, and reduce the heat generation of the first busbar component during cycling. This, in turn, reduces the heat conducted to the end cap and electrode assembly, lowers the temperature rise of the battery cell, and improves the cycle performance of the battery.

Referring to Examples 1-7 and Comparative Example 4, by adjusting the thickness of the single-layer structure of the first busbar component, the current-carrying capacity and deformability of the first busbar component can be balanced. In this embodiment, the thickness of the single-layer structure of the first busbar component is limited to not less than 1 mm. This improves the current-carrying capacity and reduces heat generation of the first busbar component during cycling when the expansion pressure of the battery cell is between 0.5 MPa and 2.4 MPa. This, in turn, reduces the heat conducted to the end caps and electrode assemblies, lowers the temperature rise of the battery cell, and improves the battery's cycle performance.

Referring to Examples 1-7 in Table 1, the embodiments of this application can reduce the heat generation of the first busbar component and reduce the expansion of the battery cells during the fast charging process, thereby reducing the risk of battery failure. The battery cells of this application have the ability to be fast charged, and the charging time for the battery cells from 10% SOC to 80% SOC can be 5 minutes to 10.5 minutes.

It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features. However, these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims (47)

A battery comprising: Multiple battery cells are arranged along their thickness direction. Each battery cell includes a casing and an electrode assembly housed within the casing. The expansion pressure of each battery cell in the thickness direction is 0.5 MPa to 2.4 MPa. The first busbar component electrically connects at least two of the battery cells arranged along the thickness direction. The first busbar component has a multi-layer structure. The electrode assembly includes a positive electrode, a negative electrode, and a separator between the positive and negative electrode. The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector. The positive electrode film layer includes a positive active material, which includes a lithium phosphate with an olivine structure. The negative electrode includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector. The negative electrode film layer includes a negative active material, which includes a carbon-based material. According to claim 1, the battery wherein the first busbar component comprises a first busbar layer and a second busbar layer stacked and connected, the first busbar layer connecting at least two battery cells arranged along the thickness direction. According to claim 2, the battery cell includes an electrode terminal disposed on the housing, the electrode terminal being electrically connected to the electrode assembly; The portion of the first bus layer that does not overlap with the second bus layer is connected to the electrode terminal. According to claim 3, the first busbar is welded to the electrode terminal, and the welding area between the first busbar and the electrode terminal is greater than or equal to 60 ^mm² . The battery according to any one of claims 2-4, wherein the first busbar component includes at least one bend, the bend connecting the first busbar layer and the second busbar layer. According to claim 5, the battery, wherein the first busbar layer includes a first busbar portion, a second busbar portion and a first buffer portion, the first busbar portion and the second busbar portion are disposed along the thickness direction and connected to different battery cells, and the first buffer portion connects the first busbar portion and the second busbar portion; At least one of the first busbar and the second busbar is connected to the bend. According to claim 6, the battery is provided in a manner that avoids the first buffer portion. According to claim 6 or 7, the battery wherein the second busbar layer includes a first stacked portion, a second stacked portion, and a second buffer portion, the first stacked portion being stacked with the first busbar portion and connected through at least one of the bending portions, and the second stacked portion being stacked with the second busbar portion and connected through at least one of the bending portions. The second buffer section connects the first stacked section and the second stacked section; In the stacking direction of the first busbar layer and the second busbar layer, the second buffer portion overlaps at least partially with the first buffer portion. According to claim 8, the second buffer portion and the first buffer portion are fitted together. The battery according to any one of claims 2-9, wherein the battery further comprises at least one second busbar component, the second busbar component being a single-layer structure and electrically connected to at least two battery cells, the thickness of the second busbar component being greater than the thickness of the first busbar layer, and the thickness of the second busbar component being greater than the thickness of the second battery cell. Thickness of the catchment layer. According to claim 10, the sum of the thickness of the first busbar layer and the thickness of the second busbar layer is equal to the thickness of the second busbar component. The battery according to any one of claims 2-11, wherein, The thickness of the first busbar layer is 1mm-2.5mm; and/or The thickness of the second busbar is 1mm-2.5mm. The battery according to any one of claims 2-12, wherein the volumetric energy density of the battery cell is 390Wh/L-450Wh/L, and the thickness of the first busbar layer is less than or equal to 2.5mm; or, The volumetric energy density of the battery cell is 450Wh/L-480Wh/L, and the thickness of the first busbar is less than or equal to 2.2mm. The battery according to any one of claims 2-13, wherein the negative electrode active material further comprises a silicon-based material; The silicon-based material contains 1%-6% silicon by mass in the negative electrode active material; the thickness of the first busbar layer is 1.2mm-2.2mm, and the thickness of the second busbar layer is 1.2mm-2.2mm. The battery according to any one of claims 2-14, wherein the first busbar layer includes a first busbar portion, a second busbar portion, and a first buffer portion connecting the first busbar portion and the second busbar portion, the first busbar portion and the second busbar portion being disposed along the thickness direction and connected to different battery cells; In the stacking direction of the first busbar layer and the second busbar layer, the first buffer portion protrudes from the first busbar portion and the second busbar portion; The first busbar layer has a recess at a position corresponding to the first buffer section. The battery according to claim 15, wherein, The volumetric energy density of the battery cell is 390Wh/L-450Wh/L, and the depth of the recess is 1.2mm-2.5mm; or, The volumetric energy density of the battery cell is 450Wh/L-480Wh/L, and the depth of the recess is 1mm-2.2mm. The battery according to any one of claims 1-16, wherein, among the plurality of battery cells, the outermost battery cell located along the thickness direction is connected to the first busbar. The battery according to any one of claims 1-17, wherein the electrode assembly includes two first surfaces and two second surfaces, the two first surfaces are disposed opposite to each other along the thickness direction, the two second surfaces are disposed opposite to each other along a direction perpendicular to the thickness direction, and the second surfaces are connected to the two first surfaces; The area of the first surface is greater than the area of the second surface. The battery according to any one of claims 1-18, wherein the expansion pressure of the battery cell in the thickness direction is 1.5 MPa-2.0 MPa. According to any one of claims 1-19, the single-sided coating weight of the negative electrode film layer is from 90 mg/1540 ^mm² to 170 mg/1540 ^mm² , and optionally from 110 mg/1540 ^mm² to 150 mg/1540 ^mm² . According to any one of claims 1-20, the negative electrode film layer has a compaction density of 1.15 g/ ^cm³ to 1.36 g/ ^cm³ at 100% SOC of the battery cell, and is optionally 1.25 g/ ^cm³ to 1.36 g/ ^cm³ . The battery according to any one of claims 1-21, wherein the porosity of the negative electrode is 27%-40%. The battery according to any one of claims 1-22, wherein the carbon-based material comprises at least one of artificial graphite and natural graphite. The battery according to any one of claims 1-23, wherein the negative electrode active material further comprises a silicon-based material, wherein the silicon element in the silicon-based material has a mass content of 0.3% to 10%, optionally 1% to 6%. The battery according to claim 24, wherein the silicon-based material comprises at least one of silicon oxide and silicon-carbon composite. The battery according to any one of claims 1-25, wherein the negative electrode film layer comprises a first negative electrode film layer and a second negative electrode film layer, and the second negative electrode film layer is disposed between the first negative electrode film layer and the negative electrode current collector; The negative electrode active material includes a first negative electrode active material disposed on the first negative electrode film layer and a second negative electrode active material disposed on the second negative electrode film layer. The first negative electrode active material includes artificial graphite, and the second negative electrode active material includes one or more of artificial graphite, natural graphite, and silicon-based materials. According to the battery of claim 26, the ratio of the thickness of the first negative electrode film to the thickness of the second negative electrode film is 3:7 to 7:3, and optionally 4:6 to 6:4. The battery according to claim 26 or 27, wherein the thickness of the first negative electrode film is less than or equal to the thickness of the second negative electrode film. The battery according to any one of claims 26-28, wherein the volume average particle size Dv50 of the first negative electrode active material is less than or equal to the volume average particle size Dv50 of the second negative electrode active material. According to any one of claims 26-29, the volume average particle size Dv50 of the first negative electrode active material is 7.8 μm-14.3 μm, and optionally 7.8 μm-11.3 μm; The volume average particle size Dv50 of the second negative electrode active material is 9.5μm-18.5μm, and can be selected as 9.5μm-14.6μm. According to any one of claims 1-30, the specific surface area of the negative electrode active material is 0.5 ^m² /g-3 ^m² /g, optionally 0.6 ^m² /g-1.2 ^m² /g. According to any one of claims 1-31, the single-sided coating weight of the positive electrode film is 200mg/1540mm² ^- 370mg/ ^1540mm² ; optionally, it is 240mg/ ^1540mm² to 330mg/ ^1540mm² . According to any one of claims 1-32, the positive electrode film layer has a compaction density of 2.50 g/ ^cm³ to 2.80 g/ ^cm³ at 100% SOC of the battery cell; optionally, it is 2.55 g/ ^cm³ to 2.70 g/ ^cm³ . The battery according to any one of claims 1-33, wherein the porosity of the positive electrode is 25%-32%. The battery according to any one of claims 1-34, wherein the thickness of the positive electrode sheet is 0.13mm-0.2mm. According to any one of claims 1-35, the ratio of the thickness of the positive current collector to the thickness of the positive electrode film is 0.05-0.3. According to any one of claims 1-36, the volume average particle size of the positive electrode active material satisfies 1μm≤Dv50≤2μm and 0.4μm≤Dv10≤0.7μm. The battery according to any one of claims 1-37, wherein the battery cell includes an electrolyte contained within the casing. According to claim 38, the electrolyte has a conductivity of 15 mS/cm at room temperature. Up to 20 mS/cm. The battery according to claim 38 or 39, wherein the electrolyte comprises an organic solvent, the organic solvent comprising one or more of carbonate solvents and carboxylic acid ester solvents. According to claim 40, the battery wherein the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. According to claim 40 or 41, the carboxylic acid ester comprises _R1- COO- _R2 , wherein _R1 and _R2 each independently comprise an alkyl group having 1-5 carbon atoms or a haloalkyl group having 1-5 carbon atoms. The battery according to any one of claims 38-42, wherein the electrolyte comprises a lithium salt, the lithium salt comprising lithium bis(fluorosulfonyl)imide (LiFSI) and lithium hexafluorophosphate ( _LiPF6) , the molar concentration of the lithium bis(fluorosulfonyl)imide (LiFSI) being from 0.2 mol/L to 0.5 mol/L, and the molar concentration of the lithium hexafluorophosphate (LiPF6 ₎ being from 0.5 mol/L to 1.0 mol/L. According to any one of claims 38-43, the electrolyte density ρ at room temperature satisfies: 1.05 g/mL ≤ ρ ≤ 1.35 g/mL. The battery according to any one of claims 1-44, wherein the dimension of the electrode assembly along the thickness direction is T, the thickness of a single layer of the negative electrode sheet is T1, and the number of layers of the negative electrode sheet stacked in the thickness direction is N; T, T1, and N satisfy: 0.3≤(N×T1)/T≤0.5. According to any one of claims 1-45, the charging time for a single battery cell to charge from 10% SOC to 80% SOC is 5 minutes to 10.5 minutes. An electrical device, characterized in that it comprises a battery according to any one of claims 1-46, the battery being used to provide electrical energy.