CN119812208A - Anode electrode, secondary battery and electrical equipment - Google Patents
Anode electrode, secondary battery and electrical equipment Download PDFInfo
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Abstract
The invention discloses an anode pole piece, a secondary battery and electric equipment, wherein the anode pole piece comprises a current collector and an anode material layer formed on the surface of the current collector, an anode coating is arranged on the anode material layer in the direction away from the current collector, and the anode coating comprises transition metal inorganic matters. According to the scheme, the anode coating containing the transition metal inorganic matters is arranged, after the functional coating is successfully converted in the initial cycle stage of the battery core, transition metal ions uniformly distributed in the coating can effectively homogenize the electric field distribution at the interface of the electrode and the electrolyte, so that the uniformity of lithium ion (Li +) flow is promoted, the problems of local polarization and lithium precipitation caused by slow local lithium ion transmission rate are solved, and the lithium precipitation risk is reduced.
Description
Technical Field
The invention relates to the technical field of new energy, in particular to an anode plate, a secondary battery and electric equipment.
Background
During battery charging, the cathode (positive electrode) material undergoes lithium ion intercalation and the anode (negative electrode) undergoes lithium ion intercalation. Taking a SiC composite graphite cathode as an example, during normal charging, the cathode mainly undergoes two processes, namely, a lithium intercalation reaction of graphite, namely, lithium ion intercalation graphite interlayer forming lithiated graphite, and an alloying reaction of Si, namely, silicon reacts with lithium ion to generate silicon-lithium alloy. However, as the number of charge and discharge cycles increases, the electrolyte is gradually consumed, and the microstructure of the anode material is also changed, which results in a gradual increase in the polarization degree of the anode lithium intercalation reaction during charging, and thus causes a gradual decrease in the anode potential. When the local potential of the negative electrode drops to near or below the precipitation potential of lithium metal, a lithium precipitation reaction occurs in this region, i.e., lithium ions are directly reduced to lithium metal.
As shown in fig. 1, the conventional negative electrode includes a current collector (Cu foil 1) and a SiC composite graphite material 2, on the surface of which lithium dendrites 3 are easily formed during a cycle. Because the lithium ion transmission rate inside the battery is different in different areas, the areas with lower lithium ion transmission rate face more polarization, so that the areas are more likely to be the first choice positions for lithium metal precipitation. The lithium precipitation reaction usually occurs on the surface of the electrode, and the precipitated lithium metal often exists in a dendrite form, and the dendrite has higher penetrability and is easy to pierce through a battery diaphragm, so that internal short circuit of the battery is caused, and a great potential safety hazard is formed on a battery core.
More importantly, the formation of lithium dendrites is irreversible. During subsequent discharge, these lithium dendrites cannot effectively delaminate into lithium ions (Li +) and re-intercalate into the cathode material, resulting in a continuous decrease in the available capacity of the cell. In addition, lithium dendrites have a larger specific surface area and react more strongly with the electrolyte, which accelerates consumption of the electrolyte and further aggravates performance degradation and failure risk of the battery.
Aiming at the problem of lithium precipitation, some technical means are adopted at present to relieve the problems, such as cathode corner punching, cathode embossing and other processes, and the aims of improving the uniformity of lithium ion transmission and reducing the polarization degree are fulfilled. However, these methods cannot fundamentally solve the problem of lithium precipitation. Once the lithium evolution reaction begins, lithium metal tends to precipitate directly at the anode surface, causing irreversible capacity loss. Therefore, more effective strategies are still to be explored in the future to inhibit the lithium precipitation reaction and ensure the safety and the cycling stability of the battery.
Disclosure of Invention
The present invention aims to solve at least one of the technical problems existing in the prior art. Therefore, the invention provides the anode plate which can reduce the lithium separation risk.
The invention also provides a secondary battery containing the anode plate.
The invention also provides electric equipment with the secondary battery.
An anode sheet according to an embodiment of the first aspect of the present invention comprises a current collector and an anode material layer formed on the surface of the current collector, wherein an anode coating layer is provided in a direction away from the current collector, and the anode coating layer comprises a transition metal inorganic substance.
According to the anode plate provided by the embodiment of the invention, the anode plate has the beneficial effects that by arranging the anode coating containing the transition metal inorganic matters, after the functional coating is successfully converted in the initial cycle stage of the battery cell, transition metal ions uniformly distributed in the coating can effectively homogenize the electric field distribution at the interface of the electrode and the electrolyte, so that the uniformity of lithium ion (Li+) flow is promoted, the problems of local polarization phenomenon and lithium precipitation caused by slow local lithium ion transmission rate are relieved, and the lithium precipitation risk is reduced. The transition metal ions uniformly distributed in the coating effectively homogenize the electric field distribution at the interface of the electrode and the electrolyte through the specific charge distribution and the electric field effect, thereby promoting the uniform deposition and stripping process of lithium ions. This feature is important for alleviating localized polarization, reducing uneven distribution of lithium ions, and reducing the risk of lithium precipitation.
According to some embodiments of the invention, the transition metal inorganic includes transition metal nitrides and transition metal fluorides.
The coating is skillfully combined with two key components, namely the transition metal fluoride and the transition metal nitride, through the mutual synergistic effect of the two key components, the uniform distribution of an electric field and the smooth conduction of lithium ion flow can be realized, and the precipitation of lithium metal on the surface of the anode material can be effectively inhibited. During the cyclic charge and discharge of the cell, these components undergo a gradual chemical reaction process, eventually converting to LiF (lithium fluoride), li 3 N (lithium nitride) and the corresponding transition metal ions. This chemical reaction not only promotes the deep integration of the coating ingredients, but also imparts unique physical and chemical properties to the coating. The resulting anode coating exhibits several significant advantageous properties over this conversion process, in that, first, it exhibits a highly uniform dense structure that ensures efficient transport paths for ions within the coating, while reducing unnecessary voids and defects, and improving the overall stability and durability of the coating. Second, the coating exhibits excellent lithium ion conductivity, which is mainly due to the highly conductive nature of Li 3 N, which significantly accelerates the rate of lithium ion transport at the electrode-electrolyte interface, thereby optimizing the reaction kinetics of the cell. In addition, the introduction of LiF brings a higher young's modulus to the coating, which means that the coating can maintain better shape stability and mechanical strength when subjected to external forces. This feature is critical to reducing the volume change and structural damage of the electrode during charge and discharge, while also helping to inhibit the growth of lithium dendrites, further reducing the risk of internal shorting and lithium evolution due to lithium dendrite penetration through the separator.
In summary, the anode coating on the pole piece of the scheme of the invention remarkably reduces the lithium dendrite precipitation risk of the battery cell in the cyclic charge and discharge process by virtue of the excellent lithium ion conductivity, the higher Young modulus and the transition metal ion distribution characteristic of the electric field which can be effectively and uniformly distributed, and the characteristics together lay a solid foundation for the stability of the overall performance of the battery cell and the extension of the cycle life.
In the initial cycle stage of the battery core, after the functional coating is successfully converted, the key effects that transition metal ions uniformly distributed in the ① coating can effectively homogenize the electric field distribution at the interface of the electrode and the electrolyte, further promote the uniformity of lithium ion (Li+) flow, relieve the problems of local polarization phenomenon and lithium precipitation caused by slow local lithium ion transmission rate, ②Li3 N can obviously accelerate the lithium ion transmission rate at the interface of the electrode and the electrolyte due to extremely high lithium ion conductivity, promote the reaction dynamics of the battery core, reduce the lithium precipitation risk caused by integral polarization, and ③ LiF can effectively reduce the structural damage caused by electrode thickness change in charge-discharge cycle and inhibit the growth of lithium dendrites due to high Young modulus, thereby providing important protection function for preventing lithium dendrites from penetrating through a diaphragm.
According to some embodiments of the invention, the transition metal nitride comprises at least one of MoN, tiN, or CuN, etc. The transition metal nitrides can all undergo oxidation-reduction reaction with Li + to generate corresponding transition metal simple substances and Li 3 N, while other transition metal nitrides which cannot undergo oxidation-reduction reaction with Li + are not in the range.
According to some embodiments of the invention, the transition metal fluoride comprises at least one of CuF 2、FeF3 or AgF, etc. The transition metal fluorides may all undergo redox reaction with Li + to form elemental transition metal and LiF corresponding thereto, while other transition metal fluorides that cannot undergo redox reaction with Li + are not within this range.
According to some embodiments of the invention, the anode coating further comprises a binder. The binder ensures that the inorganic matters of the transition metal are distributed more uniformly and compactly, the uniform and compact structure of the coating effectively isolates the direct contact between the anode material and the electrolyte, and the side reaction between the anode material and the electrolyte is obviously reduced, so that the cycle life of the battery cell is greatly prolonged under the condition of keeping the same electrolyte to be kept in quantity
According to some embodiments of the invention, the binder comprises at least one of PVDF (polyvinylidene fluoride), SBR (emulsion styrene butadiene rubber), CMC (carboxymethyl cellulose), PAA (polyarylyne), PAN (polyacrylonitrile) or PTFE (polytetrafluoroethylene). The adhesive is an oil-based or water-based adhesive commonly used in lithium ion batteries.
According to some embodiments of the present invention, the anode coating comprises a transition metal nitride, a transition metal fluoride, and a binder, wherein the total mass of the transition metal nitride, the transition metal fluoride, and the binder is m, the ratio of the weight of the transition metal nitride to m is W1, the ratio of the weight of the transition metal fluoride to m is W2, the ratio of the weight of the binder to m is W3, w1+w2+w3=100%, and 40% to W1/(w1+w2) to 70%. The proportion of the transition metal compound to the transition metal fluoride is precisely controlled so as to better improve the ionic conductivity and Young modulus of the composite layer at the same time, thereby improving the overall performance of the battery cell.
According to some embodiments of the invention, W1, W2 satisfy the relationship of 40% to W1/(W1+W2) to 70%. When W1 and W2 meet the above relation, the functional material is converted into a functional coating in which LiF, li 3 N and metal particles are uniformly mixed, and then the lithium ion transmission rate N and Young's modulus M are both at a high level. If the value of W1 is further increased, the young's modulus M is decreased, whereas if the value of W2 is further increased, the lithium ion conductivity N is decreased. Thus, the performance of the functional coating reaches an optimum state when W1 and W2 are selected to lie within this particular interval.
According to some embodiments of the invention, 3/7.ltoreq.W2/W1.ltoreq.6/4. Such as 4/6, 5/5, etc.
According to some embodiments of the invention, the range of W3 satisfies the condition that 0.1% W3 is less than or equal to 10%. Such as 0.2%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, or 9%, etc. By accurately regulating the content ratio of the binder, the induction of the transition metal nitride and the transition metal fluoride in the coating to uniform Li + flow can be effectively promoted, so that the Young modulus of the coating is remarkably improved, and the physical stability of the coating is enhanced. This regulatory strategy not only optimizes the ion transport path within the coating, but also ensures that the binder is able to firmly bind the coating material, forming a stable and reliable structural connection. Therefore, the battery cell can maintain better performance stability in the charge-discharge cycle process, and the performance attenuation risk caused by unstable coating structure is reduced, so that the overall performance and the service life of the battery cell are cooperatively improved.
According to some embodiments of the invention, the range of W3 satisfies the condition that 1% W3 10%.
According to some embodiments of the present invention, the ionic conductivity of the anode coating is N, the young's modulus of the functional coating is M, wherein M, N, W1 and W2 are required to satisfy the following relationships, m= (-55 x W1/(w1+w2) +65) x (w1+w2), n= (5.9997 x10 -3*W1/(W1+W2)+3*10-7) x (w1+w2), respectively. (in the absence of the effect of the binder, the approximate curves of M 0＝-55*W1/(W1+W2)+65,N0＝5.9997*10-3*W1/(W1+W2)+3*10-7 were first linear fitted based on the ionic conductivity (6X 10 -3Scm-1) and Young's modulus (10 MPa) of pure Li 3 N, and the ionic conductivity (3X 10 - 7Scm-1) and Young's modulus (65 MPa) of pure LiF; the effect of (W1+W2) on M and N was continued to be introduced considering that the higher W3, i.e., the lower W1+W2, the lower M and N.
According to some embodiments of the invention, N is ≡0.0023S/cm and M is ≡25.9Gpa. The coating provided by the scheme of the invention has excellent lithium ion conductivity and higher Young modulus, and the high-level lithium ion conductivity obviously accelerates the transmission rate of lithium ions at the interface of the electrode and the electrolyte, so that the reaction kinetics performance of the battery cell is optimized. The higher young's modulus means that the coating maintains better shape stability and mechanical strength when subjected to external forces. This feature is critical to reducing the volume change and structural damage of the electrode during charge and discharge, while also helping to inhibit the growth of lithium dendrites, further reducing the risk of internal shorting and lithium evolution due to lithium dendrite penetration through the separator.
According to some embodiments of the invention, the thickness of the coating is T μm, the thickness of the coating satisfying the relationship 0.045.ltoreq.T.ltoreq.1. The thickness of the coating is controlled in an appropriate range, so that the uniformity and efficiency of the coating in lithium ion transmission are effectively improved, and the initial efficiency (namely initial efficiency) and Energy Density (ED) of the battery cell are ensured not to be damaged.
According to some embodiments of the invention, 0.1.ltoreq.T.ltoreq.1.
According to some embodiments of the invention, 0.05 (W1+W2). Ltoreq.T.ltoreq.10W3.
According to some embodiments of the invention, the anode material layer comprises an anode active material comprising at least one of SiC composite graphite material, si/C composite material, siO/C composite material.
According to a second aspect of the present invention, a secondary battery according to an embodiment of the present invention includes the above-described anode tab.
According to some embodiments of the invention, the secondary battery further comprises a cathode sheet and a separator sheet, the cathode sheet and the anode sheet being wound or stacked, and the separator sheet being disposed between the cathode sheet and the anode sheet.
According to an embodiment of the third aspect of the present invention, the electric device includes the above secondary battery.
According to some embodiments of the invention, the powered device further comprises a load, and the secondary battery is electrically connected to the load.
The secondary battery and the electric equipment have the same technical characteristics as those of the anode pole piece, so that the same technical effects can be achieved, and the repeated description is omitted.
Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
Drawings
The invention is further described with reference to the accompanying drawings and examples, in which:
Fig. 1 is a schematic diagram of a lithium-silicon-carbon negative electrode structure in the prior art.
Fig. 2 is a schematic diagram of the operation of an anode sheet in an embodiment of the present invention.
FIG. 3 is a graph showing the variation of the ionic conductivity and Young's modulus with the W1 value in example 1 of the present invention.
The reference numerals are 1, cu foil, 2, siC composite graphite material, 3, lithium dendrite, 4, lithium ion flow, 5, anode coating and 6, electric field.
Detailed Description
The conception and the technical effects produced by the present invention will be clearly and completely described in conjunction with the embodiments below to fully understand the objects, features and effects of the present invention. It is apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments, and that other embodiments obtained by those skilled in the art without inventive effort are within the scope of the present invention based on the embodiments of the present invention. The test methods used in the examples are conventional methods unless otherwise specified, and the materials, reagents, etc. used, if otherwise specified, are commercially available. Unless otherwise indicated, the same parameter is the same in each embodiment. The following examples are illustrative only and are not to be construed as limiting the invention.
In the description of the present invention, reference to the term "some embodiments" or the like means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
In the description of the present invention, the description of first, second, etc. is for the purpose of distinguishing between technical features only and should not be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated or implicitly indicating the precedence of the technical features indicated.
Example 1
The example provides an anode pole piece which sequentially comprises a current collector (Cu foil 1), an anode material layer (SiC composite graphite material 2) and an anode coating 4.
The preparation method of the anode coating comprises the following steps:
S1, preparing a functional material into slurry, wherein the functional material specifically comprises a transition metal nitride with a weight ratio of W1, specifically MoN, a transition metal fluoride with a weight ratio of W2, specifically CuF 2, a binder with a weight ratio of W3, specifically PVDF, and a solvent of NMP. W1+w2=98%, w1:w2=6:4, i.e. W1 is 58.8%, W2 is 39.2%, W3 is 2%.
S2, uniformly coating the slurry prepared by the operation on the anode material layer. The thickness of the coating was T.mu.m, and T was 0.1.
The working principle of the anode plate is shown in figure 2. In the working process of the anode plate, the anode coating 4 has the functions of 1) homogenizing lithium ion current 5;2) homogenizing an electric field 6, 3) improving Young modulus, and 4) improving compactness.
The ionic conductivity of the anode coating is N, the Young' S modulus of the functional coating is M, and according to M= (-55×W1/(W1+W2) +65) (W1+W2), N= (5.9997×10 -3*W1/(W1+W2)+3*10-7) (W1+W2), the calculation shows that N is more than or equal to 0.0023S/cm, and M is more than or equal to 25.9GPa. The change curve of M, N values versus W1 is shown in FIG. 3 when W3 is fixed at 2%. When W1 is changed, W2 only needs to satisfy the relationship of w1+w2=98%, w3=2%, and 40% to less than or equal to W1/(w1+w2) toless than or equal to 70%, and may vary within this interval. As can be seen from fig. 3, as W1/(w1+w2) increases, the ion conductivity N increases and the young's modulus M decreases. When w1=0, W1/(w1+w2) =0, the ion conductivity N reaches a minimum value of 2.94×10 -7, the young's modulus M reaches a maximum value of 63.7MPa (the ion conductivity and young's modulus are values obtained by mixing pure LiF, a metal simple substance, and 2% binder), and similarly, when w2=0, W1/(w1+w2) =1, the N value reaches a maximum value of 5.88×10 -3, and M reaches a minimum value of 9.8MPa (the ion conductivity and young's modulus are values obtained by mixing pure Li 3 N, a metal simple substance, and 2% binder). The values of N and M need to be within this range because further reduction of N can seriously affect lithium ion transmission at the interface, affect cell reaction kinetics, and deteriorate electrochemical performance, while further reduction of M can greatly reduce physical properties of the protective layer, resulting in easier breakage of the protective layer, and likewise deteriorate cell cycle performance.
The secondary battery comprises the anode plate, the isolating film, the electrolyte and the cathode plate, wherein the isolating film is positioned between the anode plate and the cathode plate, and the electrolyte is filled in the anode plate and the cathode plate.
The embodiment also provides electric equipment, which comprises a load and the secondary battery, wherein the secondary battery is used for providing electric energy for the load.
Example 2
The present example provides an anode sheet, a secondary battery and electric equipment, which are different from the example 1 in that in the preparation raw materials of the anode coating, w1:w2=4:6, that is, W1 is 39.2%, and W2 is 58.8%.
Example 3
The present example provides an anode sheet, a secondary battery and electric equipment, which are different from the example 1 in that in the preparation raw materials of the anode coating, w1:w2=7:3, that is, W1 is 68.6%, and W2 is 29.4%.
Example 4
The present example provides an anode sheet, a secondary battery and electric equipment, which are different from the example 1 in that in the preparation raw materials of the anode coating, w1+w2=99%, i.e. W1 is 59.4%, W2 is 39.6%, and W3 is 1%.
Example 5
The anode plate, the secondary battery and the electric equipment are different from those in the embodiment 1 in that in the preparation raw materials of the anode coating, W1+W2=90%, namely, W1 is 54%, W2 is 36%, and W3 is 10%.
Example 6
The present example provides an anode sheet, a secondary battery and electric equipment, which are different from embodiment 1 in that T is 1.
Example 7
This example provides an anode sheet, a secondary battery and electric equipment, which are different from the example 1 in that T is 2.
Example 8
This example provides an anode sheet, a secondary battery and electric equipment, which are different from example 1 in that T is 0.02.
Example 9
The example provides an anode sheet, a secondary battery and electric equipment, which are different from the example 1 in that in the preparation raw materials of the anode coating, W1:W2=1:9, namely W1=9.8%, and W2 is 88.2%.
Example 10
The example provides an anode sheet, a secondary battery and electric equipment, which are different from the example 1 in that in the preparation raw materials of the anode coating, W1:W2=9:1, namely W1=88.2%, and W2 is 9.8%.
Example 11
The anode plate, the secondary battery and the electric equipment are different from those in the embodiment 1 in that in the preparation raw materials of the anode coating, W1+W2=99.8%, W1:W2=6:4, W1 is 59.88%, W2 is 39.92%, and W3 is 0.2%.
Example 12
The anode plate, the secondary battery and the electric equipment are different from those in the embodiment 1 in that in the preparation raw materials of the anode coating, W1+W2=60%, W1:W2=6:4, W1 is 36%, W2 is 24%, and W3 is 40%.
Comparative example 1
This example provides an anode sheet, a secondary battery, which differs from the anode sheet in example 1 in that the anode material layer material surface does not contain an anode coating layer.
For comparison, parameters such as T value, transition metal nitride, transition metal fluoride, PVDF content, etc. in examples and comparative examples are summarized in Table 1:
TABLE 1
And (3) performing performance test, namely controlling the cathode material, the electrolyte, the diaphragm and other components to be identical, respectively taking the anode plates in the examples and the comparative examples, assembling the anode plates into a soft-package battery, testing the Energy Density (ED) at 25 ℃, performing 3.6C (1C=6.5A) rate charge-discharge cycle test, and testing the capacity retention rate and the thickness change rate of the battery core after 800 weeks of cycle number.
The test results are shown in table 2 below.
TABLE 2
| Group of | ED(Wh/kg) | Capacity retention rate | Thickness change rate |
| Example 1 | 820 | 83.00% | 13.00% |
| Example 2 | 820 | 82.80% | 13.30% |
| Example 3 | 820 | 82.50% | 13.60% |
| Example 4 | 820 | 82.10% | 14.00% |
| Example 5 | 820 | 81.80% | 14.40% |
| Example 6 | 815 | 82.90% | 13.20% |
| Example 7 | 790 | 80% | 18% |
| Example 8 | 821 | 71% | 22% |
| Example 9 | 820 | 75% | 20% |
| Example 10 | 820 | 81% | 15% |
| Example 11 | 820 | 81.50% | 14.80% |
| Example 12 | 820 | 78% | 19% |
| Comparative example 1 | 822 | 68% | 25% |
The data in table 2 were analyzed as follows:
1) The transition metal nitride content was reduced in example 2 (W1: W2 ratio of 4:6) compared to example 1 (W1: W2 ratio of 6:4), and the transition metal fluoride content was correspondingly increased. This variation causes the Li 3 N content in the protective layer to decrease, while the LiF content increases. Therefore, the lithium ion conductivity of the protective layer is reduced, the reaction kinetics performance of the battery cell is also reduced, and the electrochemical performance is reduced, but the lithium ion conductivity of the protective layer is still at a better level compared with the prior art.
2) The Li 3 N content in example 3 (W1: W2 ratio of 7:3) was significantly increased compared to example 1, which promoted an increase in the lithium ion transport rate. However, this variation also causes a decrease in the mechanical strength of the protective layer. As the number of battery cycles increases, the protective layer structure may be partially destroyed, resulting in a decrease in the overall performance of the battery cell, but still at a superior level compared to the prior art.
3) Example 4 differs from example 1 in that the sum of W1 and W2 (i.e. w1+w2=99%) results in a reduction of the binder content. This variation reduces the overall structural stability of the protective layer. Therefore, as the number of battery cycles increases, the retention of capacity decreases and the degree of expansion of the cells increases, but is still at a superior level compared to the prior art.
4) Example 5 (w1+w2=90%) has significantly higher binder content than example 1, and will simultaneously reduce the ionic conductivity and young's modulus, so that the improvement effect is reduced, but still at a better level than the prior art.
5) In example 6, the coating thickness was increased compared to example 1, so that the thickness of the entire cell was also increased. This variation results in a decrease in the Energy Density (ED) of the cell, and a slight deterioration in the cycling stability, but is still at a superior level compared to the prior art.
6) Example 7 has a significant increase in the thickness of the functional anode coating compared to example 1, again resulting in an increase in the overall cell thickness and a decrease in energy density. In addition, the thicker functional anode coating increases the contact resistance, thereby slowing down the reaction kinetics inside the cell, resulting in a reduction in cycling performance, but still at a superior level compared to the prior art.
7) Example 8 significantly reduced the thickness of the functional anode coating compared to example 1, while the energy density was increased, the cell cycle stability was reduced due to incomplete modification of the functional anode coating, but still at a superior level compared to the prior art.
8) Example 9, compared to example 1, the transition metal fluoride content predominated, resulting in a decrease in the ionic conductivity of the functional anode coating. Although the mechanical strength is increased, the cyclic stability of the battery cells still shows a decreasing trend, but is still at a superior level compared to the prior art.
9) Example 10 is a dominant transition metal nitride compared to example 1, such that the ionic conductivity of the overall functional anode coating is significantly increased. However, the mechanical strength is relatively weak, the coating structure is easy to break after circulation, and the circulation stability is reduced, but the coating structure is still at a better level compared with the prior art.
10 Example 11 further increased the content of functional materials in the functional anode coating compared to example 1, while significantly reducing the binder content. This variation results in a decrease in the adhesion properties of the coating, adversely affecting the cycling performance of the cell, particularly in a decrease in cycling capacity retention and an increase in thickness expansion, but still at a superior level compared to the prior art.
11 Example 12 reduced the content of functional material compared to example 1, resulting in a reduced effect on uniform lithium ion flow, while also significantly reducing young's modulus. These variations also adversely affect the cycling performance of the cells, resulting in reduced cycling performance, but still at a superior level compared to the prior art.
12 Comparative example 1 was not coated with the functional anode coating, and lithium was more severely eluted, so that both the cycle capacity retention rate and the expansion were significantly deteriorated.
In summary, by arranging the functional anode coating according to the embodiment of the invention, the risk of lithium precipitation is remarkably reduced, and the cycle stability of the battery is remarkably improved. In addition, the composition ratio, the content adjustment and the thickness change of the coating can have certain influence on the composition of the protective layer, the lithium ion conductivity, the mechanical strength and the overall electrochemical performance (including energy density and cycling stability) of the battery cell.
The embodiments of the present invention have been described in detail, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the spirit of the present invention.
Claims (10)
1. The anode plate comprises a current collector and an anode material layer formed on the surface of the current collector, wherein an anode coating is arranged on the anode material layer in the direction away from the current collector, and the anode plate is characterized in that the anode coating comprises transition metal inorganic matters.
2. The anode electrode sheet according to claim 1, wherein the transition metal inorganic comprises a transition metal nitride and a transition metal fluoride, preferably the transition metal nitride comprises at least one of MoN, tiN, or CuN, and/or the transition metal fluoride comprises at least one of CuF 2、FeF3 or AgF.
3. The anode sheet of claim 2, wherein the anode coating further comprises a binder, preferably the binder comprises at least one of PVDF, SBR, CMC, PAA, PAN or PTFE.
4. The anode sheet according to claim 3, wherein the anode coating layer comprises a transition metal nitride, a transition metal fluoride and a binder, wherein the total mass of the transition metal nitride, the transition metal fluoride and the binder is m, the ratio of the weight of the transition metal nitride to m is W1, the ratio of the weight of the transition metal fluoride to m is W2, the ratio of the weight of the binder to m is W3, W1+W2+W3=100%, and 40% or less of W1/(W1+W2), preferably, W1, W2 satisfies the following relation of 40% or less of W1/(W1+W2) or less of 70%.
5. The anode sheet according to claim 4, wherein the ionic conductivity of the anode coating is N and the Young' S modulus of the functional coating is M, wherein M= (-55 x W1/(W1+W2) +65) x (W1+W2), N= (5.9997 x 10 -3*W1/(W1+W2)+3*10-7) x (W1+W2), preferably N.gtoreq.0.0023S/cm, M.gtoreq.25.9 Gpa.
6. The anode sheet according to claim 4, wherein W2/W1 is 3/7.ltoreq.6/4 and/or W3 is in a value range of 0.2.ltoreq.W3.ltoreq.10%.
7. The anode sheet according to any one of claims 1 to 6, wherein the positive coating has a thickness T μm, and the positive coating has a thickness satisfying the following relation of 0.05.ltoreq.T.ltoreq.1.5, preferably 0.1.ltoreq.T.ltoreq.1, more preferably 0.005 (W1+W2). Ltoreq.T.ltoreq.W3.
8. The anode sheet according to claim 1, wherein the anode material layer contains an anode active material including at least one of SiC composite graphite material, si/C composite material, siO/C composite material.
9. A secondary battery comprising the anode sheet according to any one of claims 1 to 8.
10. A powered device comprising the secondary battery of claim 9.
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