CN103746089B - A kind of solid lithium battery with gradient-structure and preparation method thereof - Google Patents

Abstract

The invention discloses an all-solid-state lithium battery with a gradient structure and a preparation method thereof. The all-solid-state lithium battery is composed of a positive electrode with a gradient structure layer, a solid electrolyte layer, and a metal negative electrode or a negative electrode with a gradient structure layer; the preparation method The positive electrode slurry is prepared first with different component concentrations or particle sizes or molecular weights, and the positive electrode slurry is coated on the collector according to the concentration gradient or particle size gradient or molecular weight gradient of the components to prepare an electrode layer, and then coated with a solid electrode layer on the electrode layer. Electrolyte layer, finally stick metal negative electrode, or configure negative electrode slurry with different component concentration or particle size or molecular weight, and apply negative electrode slurry on the electrolyte layer according to the opposite concentration gradient or particle size gradient or molecular weight gradient in the method of preparing positive electrode layer The negative electrode layer is prepared on top, and the collector is finally bonded to obtain an all-solid-state lithium battery with a gradient structure; the preparation method is simple, and the obtained all-solid-state lithium battery is stable in charging and discharging at a large rate, and can work normally under high current.

Description

A kind of all-solid-state lithium battery with gradient structure and its preparation method

technical field

The invention relates to an all-solid lithium battery with a gradient structure and a preparation method thereof, belonging to the field of solid batteries.

Background technique

Against the backdrop of the dual trends of energy crisis and environmental protection, the development of new energy vehicles, such as electric vehicles (EV), hybrid electric vehicles (HEV) and plug-in hybrid electric vehicles (PHEV), has become an urgent need. As the energy storage device of new energy vehicles, batteries have become one of the core key technologies of new energy vehicles.

Compared with liquid electrolyte batteries, all-solid-state batteries also have greater room for development in terms of improving battery energy density, widening the operating temperature range, and extending service life. Since the beginning of the 21st century, diversification has become an important development direction in the field of secondary batteries. While broadening the application fields of batteries, people also pay more and more attention to the personalized design of batteries to improve the performance and temperature adaptability of batteries.

Unlike liquid batteries, all-solid-state batteries have poor compatibility between electrolytes and electrodes, and the batteries have poor high-rate discharge performance. The wettability of the electrolyte to the electrode is the active site of the electrochemical reaction and an important guarantee for the smooth passage of electrons and ions, while the low impedance at the electrode interface is the key to determining the performance of the battery. For the solid/liquid electrode interface, there is not much problem, but for the solid/solid interface, since the solid electrolyte does not have the wettability of the liquid electrolyte, the interface impedance of a solid battery made of a solid electrolyte is generally larger than the bulk impedance. more than an order of magnitude. Therefore, it is extremely important to fully consider the contact between the electrode and the electrolyte from the structural design of the battery.

On the other hand, if the battery electrode layer is composed of uniform electrolyte and electrode material in three dimensions, then during battery discharge, the lithium ions in the electrolyte in the positive electrode active material layer are quickly absorbed into the electrode active material particles, and the electrode activity The reduction in the lithium ion concentration of the electrolyte in the material layer is supplemented by the diffusion of lithium ions from the electrolyte layer. At the same time, the electrons in the collector are conducted through the conductive material, thereby promoting the electrode reaction. The speed at which lithium ions diffuse from the electrolyte layer to the electrode material layer is slow relative to the conduction of electrons. Under high-speed charge and discharge, the lithium ions of the positive electrode material layer tend to be depleted, and this tendency increases toward the collector. The diffusion of lithium ions cannot keep up with the rate of electrode reaction, resulting in a large overvoltage, the battery cannot provide the theoretical charge and discharge capacity, and the rapid charge and discharge performance of the battery decreases.

Contents of the invention

For the battery electrode layer in the prior art, the concentration of the electrolyte and the electrode material is uniformly distributed, and there is a defect that Li ions are easily depleted during charging or discharging at a high current rate, resulting in a decrease in the battery performance of the charging or discharging capacity. For an all-solid-state lithium battery with an electrode layer, the contact between the electrode and the electrolyte is easy to deteriorate, the interface impedance is very large, and the battery cannot be charged and discharged at a high rate. An all-solid-state lithium battery with a gradient structure that can work normally.

Another object of the present invention is to provide a method for preparing the all-solid-state lithium battery with a gradient structure with a simple process and low cost.

The invention provides an all-solid-state lithium battery with a gradient structure, the all-solid-state lithium battery is composed of a positive electrode with a gradient structure layer, a solid electrolyte layer, and a metal negative electrode or a negative electrode with a gradient structure layer; the gradient structure The layer is an electrode layer in which the component concentration changes continuously in a gradient, an electrode layer in which the particle size of the component changes continuously in a gradient, or an electrode layer in which the molecular weight of the component changes continuously in a gradient.

The gradient refers to the continuous change of the value, which may be a continuous change of the value from small to large or from large to small.

The electrode layer in which the component concentration changes continuously in a gradient is preferably an electrode layer in which the mass percentage concentration of the electrode material in the electrode layer gradually decreases from the collector to the electrolyte layer.

The electrode layer in which the particle size of the components changes continuously in a gradient is preferably that the particle size of the electrode active material in the electrode layer gradually increases from the collector to the electrolyte layer.

The electrode layer in which the molecular weight of the components changes continuously in a gradient is preferably formed in an electrode layer in which the molecular weight of the polymer electrolyte gradually increases from the collector to the electrolyte layer.

The electrode layer whose component concentration changes continuously in a gradient comprises at least two film layers with different concentration components; preferably at least three film layers with different concentration components; most preferably at least five different concentration components film layer.

The electrode layer in which the particle size of the components changes continuously in a gradient comprises at least two film layers of different particle size components; preferably at least three film layers of different particle size components; most preferably at least five different particle size components film layer.

The electrode layer in which the molecular weight of the components changes continuously with a gradient comprises at least two film layers with different molecular weight components; preferably at least three film layers with different molecular weight components; most preferably at least five different molecular weight components film layer.

The thickness of the film layer is 1-100 μm.

The thickness of the electrolyte layer is 1-30 μm.

The positive active material in the electrode active material includes LiCoO ₂ Li-Co composite oxide group, LiNiO ₂ Li-Ni composite oxide group, LiMn ₂ O ₄ Li-Mn composite oxide group, and LiFePO ₄ Li-Fe composite oxide family, or Li-Ni-Mn-Co-O composite oxide such as Li(NiCoMn)O ₂ , LiMn _0.7 Fe _0.3 PO ₄ lithium manganese iron phosphate composite, etc.; negative electrode active materials include Li ₄ Ti ₅ O ₁₂ , graphite or metallic lithium, etc.

The solid electrolyte layer includes an inorganic electrolyte material layer or a polymer electrolyte material, and the inorganic electrolyte material includes perovskite type, LISICON type, NASICON type, layered Li ₃ N type, LiPON type, oxide glass state and sulfide glass Polymer electrolyte materials include polyoxyethylene-based electrolytes, polyoxyethylene derivative-based electrolytes, and polysiloxane-based electrolytes.

The all-solid-state lithium battery of the present invention can be assembled into batteries connected in series internally, in parallel internally, or both, and all-solid-state lithium battery cells of different shapes can be prepared by stacking, roll-to-roll, and the like.

The present invention also provides a method for preparing the all-solid-state lithium battery with a gradient structure, comprising the following steps:

a) Formulating electrode materials and electrolytes with different mass ratios into multiple groups of positive electrode slurries with different mass percentages of electrode materials; or formulating electrode active materials with different particle sizes and auxiliary materials into electrode materials, and then formulating electrode active materials with electrolytes Multiple sets of positive electrode slurries with different particle sizes; or prepare multiple sets of positive electrode materials with different molecular weight polymer electrolytes and electrode materials; prepare multiple sets of positive electrode slurries according to the concentration gradient of the electrode material mass percentage , or the gradient of the particle size of the electrode active material, or the gradient of the molecular weight of the polymer electrolyte is sequentially coated on the surface of the collector to obtain a positive electrode layer with a gradient structure;

b) configuring an electrolyte slurry, coating the electrolyte slurry on the surface of the positive electrode layer with a gradient structure obtained in a) to obtain an electrolyte layer;

c) directly adhering metal electrodes on the surface of the electrolyte layer in b); or prepare multiple sets of negative electrode slurry according to the method of preparing positive electrode slurry in a), and mix the multiple sets of negative electrode slurry with the mass percentage concentration of electrode material and a) The opposite concentration gradient or the opposite particle size gradient of the particle size of the electrode active material and a) or the opposite molecular weight gradient of the polymer electrolyte molecular weight and a) are sequentially coated on the electrolyte layer of b), and then the collector is adhered to obtain a gradient Structured all-solid-state lithium battery.

The auxiliary materials include conductive materials and adhesives.

The coating can be by methods such as inkjet, scrape coating, or screen printing.

The preparation of the positive electrode layer and the electrolyte layer in the method of the present invention can also be prepared by methods such as magnetron sputtering and vapor deposition.

Beneficial effects of the present invention: the present invention for the first time designs the electrode layer of the electrode in the solid lithium battery to have a gradient structure layer with a gradient continuous change in component concentration, a gradient change in component particle size, or a gradient change in component molecular weight, effectively Improve the diffusion rate of lithium ions in the electrode layer, and at the same time, the assembled battery has no obvious interface between the solid electrolyte and the electrode, which can realize the maximum contact between the electrode material and the solid electrolyte; the all-solid-state lithium battery with this gradient structure layer can operate at a large rate Charge and discharge can be realized, and it can work normally at a high current rate; in addition, a single-layer battery with such a gradient structure layer can be prepared into laminated or wound batteries of various shapes.

Description of drawings

[Fig. 1] is a schematic diagram of an all-solid-state lithium battery prepared in Example 1 of the present invention.

[Fig. 2] is the charge-discharge curve of the all-solid-state lithium battery prepared in Example 1 of the present invention and the all-solid-state lithium battery prepared in the comparative example at room temperature at 1C rate.

[Fig. 3] is a schematic diagram of an all-solid-state lithium battery prepared in Example 2 of the present invention.

[Fig. 4] is a schematic diagram of an all-solid-state lithium battery prepared in Example 3 of the present invention.

[Fig. 5] is a schematic diagram of an all-solid-state lithium battery prepared in Example 4 of the present invention.

[Figure 6] It is a schematic diagram of a cylindrical inner-tandem laminated all-solid-state lithium battery: 61 is the battery as a whole; 62 is the negative electrode lead-out; 63 is the negative electrode coating; 64 is the positive electrode coating; 65 is the solid electrolyte; 66 is the collector ; 67 is an insulating layer; 68 is a positive terminal; 69 is a battery casing.

[Figure 7] It is a schematic diagram of a square internal stacked chip type all-solid-state lithium battery: 71 is the positive terminal; 72 is the shell; 73 is the solid electrolyte; 74 is the collector interlayer insulation material; 75 is the collector and the terminal insulation material ; 76 is the negative electrode coating; 77 is the positive electrode coating; 78 is the negative electrode lead-out end.

detailed description

The present invention is further described by the following examples, but the present invention is not limited to the examples.

Example 1

(a) Change the amount of the electrode material and solid electrolyte to be added to form the electrode layer so that the mass fraction of the electrode material is 10%, 50%, and 100%, and prepare positive electrode slurry. The electrode material is a mixture of LiFePO ₄ , polyvinylidene fluoride and conductive carbon (mass ratio 8:1:1), and the electrolyte is a mixture of polysiloxane and lithium salt (mass ratio 8:2). has a viscosity of 3cP;

(b) coating the collector with the various positive electrode slurries, so that the concentration gradient of the positive electrode material decreases sequentially from the collector of the electrode active material layer to the surface of the positive electrode layer, thereby stacking a plurality of positive electrode thin film layers with different solid concentrations; The thickness of each positive film layer is about 50 μm;

(c) configure the electrolyte slurry, and coat it on the film layer that has been formed on the positive electrode, with a thickness of about 15 μm;

(d) Press the metal lithium-containing collector on the formed electrolyte film, and finally encapsulate it with a battery case.

Figure 1 shows an all-solid-state lithium battery with component concentration gradients.

Comparative Example 1

The experimental conditions are the same as those in Example 1, except that the electrode material and solid electrolyte are mixed and uniformly coated on the collector to form an electrode layer, and no concentration gradient of the electrode material is formed.

The all-solid-state lithium batteries prepared in Example 1 and Comparative Example 1 were placed in an incubator, the temperature was kept at 25°C, and a 1C rate discharge performance test was performed using a charge-discharge device.

The discharge rate of the all-solid-state lithium battery of Example 1 is 73%, while the discharge rate of the all-solid-state lithium battery of Comparative Example 1 is 66%, and the former has a higher discharge platform, so the former battery is more superior. The relationship between voltage and capacity is shown in Figure 2.

Example 2

(a) Mix a certain amount of spinel structure LiMn ₂ O ₄ as the positive electrode active material, a certain amount of acetylene black as the conductive material, and a certain amount of polyvinylidene fluoride as the binder, and the mass ratio of the three is 9: 5:5, a certain amount of polysiloxane and lithium salt, the ratio of the two is 8:2, so that the mass ratio of the electrolyte component to the electrode material is maintained at 7:3, and the particle size of LiMn ₂ O ₄ is changed (0.1 μm, 0.3μm, 0.6μm), so as to prepare a variety of cathode slurries with different particle sizes of active materials;

(b) Coating the current collector with the various positive electrode slurries, so that the particle size of the positive electrode active material increases sequentially from the collector of the electrode active material layer to the surface of the positive electrode layer, and the thickness of each positive electrode film layer is about 50 μm;

(c) Configure electrolyte slurry, siloxane and lithium salt, the ratio of the two is 8:2, and coat it on the film layer formed on the positive electrode, with a thickness of about 15 μm;

(d) mixing a certain amount of graphite as the negative electrode active material, a certain amount of acetylene black as the conductive material, and a certain amount of polyvinylidene fluoride as the binder, the mass ratio of the three is 9:5:5, and a certain amount of Polysiloxane and lithium salt, the ratio of the two is 8:2, so that the mass ratio of the electrolyte component to the electrode material is maintained at 7:3, and the particle size of the graphite (0.1μm, 0.3μm, 0.6μm) is changed, thereby Prepare a variety of negative electrode slurries with different particle sizes of active materials;

(e) Coating the collector with the various negative electrode slurries, so that the particle size of the negative electrode active material decreases from the surface of the electrolyte layer to the collector, thereby laminating a plurality of negative electrode film layers with different particle sizes of the active material.

Figure 3 shows an all-solid-state lithium battery with electrode active material particle size.

Example 3

(a) Mix a certain amount of LiCoO ₂ as the positive electrode active material, a certain amount of acetylene black as the conductive material, and a certain amount of polyvinylidene fluoride as the binder. The mass ratio of the three is 9:5:5, and a certain amount Polyoxyethylene and lithium salt, the ratio of the two is 8:2, so that the mass ratio of the electrolyte component to the electrode material is maintained at 7:3, and the molecular weight of the changed polyoxyethylene (8000, 400000, 4000000), thus Prepare a variety of positive electrode slurries with different molecular weights of electrolyte polymers;

(b) Coating the current collector with the various positive electrode slurries, so that the molecular weight of polyoxyethylene increases sequentially from the collector to the surface of the positive electrode layer, and the thickness of each positive electrode film layer is about 50 μm;

(c) Configure the electrolyte slurry, polyoxyethylene (molecular weight: 4,000,000) and lithium salt, the ratio of the two is 8:2, and coat it on the film layer formed on the positive electrode, with a thickness of about 15 μm.

(d) mixing a certain amount of graphite as the negative electrode active material, a certain amount of acetylene black as the conductive material, and a certain amount of polyvinylidene fluoride as the binder, the mass ratio of the three is 9:5:5, and a certain amount of Polyoxyethylene and lithium salt, the ratio of the two is 8:2, so that the mass ratio of the electrolyte component to the electrode material is maintained at 7:3, and the molecular weight of polyoxyethylene (8000, 400000, 4000000) is changed to prepare the electrolyte A variety of negative electrode slurries with different polymer molecular weights;

(e) Coating the current collector with the various negative electrode slurries, so that the molecular weight of the polyoxyethylene decreases from the surface of the electrolyte layer to the current collector, thereby stacking multiple negative electrode thin film layers with different active material particle sizes.

Figure 4 shows an all-solid-state lithium battery with a gradient change in the molecular weight of the electrolyte polymer.

Example 4

(a) Mix a certain amount of LiCoO ₂ as the positive electrode active material, a certain amount of acetylene black as the conductive material, and a certain amount of polyvinylidene fluoride as the binder. The mass ratio of the three is 9:5:5, and a certain amount Polysiloxane and lithium salt, so that the mass ratio of electrolyte components and electrode materials is maintained at 7:3, change the ratio of polysiloxane and lithium salt (8:2, 7:3, 6:4) , so as to prepare a variety of positive electrode slurries with different electrolyte lithium salt concentrations;

(b) Coating the current collector with the various positive electrode slurries, the content of lithium salt decreases sequentially from the collector to the surface of the positive electrode layer, and the thickness of each positive electrode film layer is about 50 μm;

(c) Configure electrolyte slurry, polysiloxane and lithium salt, the ratio of the two is 8:2, and coat it on the film layer formed on the positive electrode, with a thickness of about 15 μm;

(d) mixing a certain amount of graphite as the negative electrode active material, a certain amount of acetylene black as the conductive material, and a certain amount of polyvinylidene fluoride as the binder, the mass ratio of the three is 9:5:5, and a certain amount of Polysiloxane and lithium salt, so that the mass ratio of the electrolyte component to the electrode material is maintained at 7:3, and the ratio of polysiloxane to lithium salt (8:2, 7:3, 6:4) is changed, Thereby preparing a variety of negative electrode slurries with different electrolyte lithium salt concentrations;

(e) Coating the collecting electrode with the various negative electrode slurries, so that the lithium salt concentration increases from the surface of the electrolyte layer to the collecting electrode, thereby stacking a plurality of negative electrode film layers with different lithium salt concentrations.

Figure 5 shows an all-solid-state lithium battery with a gradient change in electrolyte concentration.

Example 5

From the perspective of internal electrical connection, the all-solid-state lithium batteries formed according to Examples 1-4 can be designed as internal series battery cells or internal parallel battery cells. Internal series cells have high voltage as simple cells and have excellent capacity and output characteristics. The all-solid-state lithium battery according to the embodiment is preferably fabricated as an internal series battery. Laminate the thin-layer batteries in Examples 1 to 4, and separate the positive and negative electrode thin film layers with electrolyte layers, then package the entire stack and seal it with the laminated material that constitutes the battery case, so that only the positive and negative lead wires are exposed to the outside , thereby providing an all-solid-state lithium battery unit.

Claims (6)

1. a solid lithium battery with gradient-structure, is characterized in that, by have gradient-structure layer positive pole,Solid electrolyte layer and metal negative pole or there is the negative pole composition of gradient-structure layer; Described gradient-structure layerFor the granularity of electrode active material forms the electricity progressively increasing to dielectric substrate direction from colelctor electrode in electrode layerThe molecular weight of utmost point layer or polyelectrolyte forms from colelctor electrode and progressively increases to dielectric substrate direction in electrode layerLarge electrode layer; The thickness of described solid electrolyte layer is 1～30 μ m.

2. the solid lithium battery with gradient-structure as claimed in claim 1, is characterized in that, described groupPoint granularity in gradient continually varying electrode layer at least comprises the rete of two different grain size components; Described componentMolecular weight in gradient continually varying electrode layer at least comprises the rete of two different molecular weight components.

3. the solid lithium battery with gradient-structure as claimed in claim 2, is characterized in that, described groupPoint granularity in gradient continually varying electrode layer at least comprises the rete of three different grain size components; Described componentMolecular weight in gradient continually varying electrode layer at least comprises the rete of three different molecular weight components.

4. the solid lithium battery with gradient-structure as claimed in claim 3, is characterized in that, described groupPoint granularity in gradient continually varying electrode layer at least comprises the rete of five different grain size components; Described componentMolecular weight in gradient continually varying electrode layer at least comprises the rete of five different molecular weight components.

5. the solid lithium battery with gradient-structure as claimed in claim 4, is characterized in that, described filmThe thickness of layer is 1～100 μ m.

6. prepare a method for the solid lithium battery with gradient-structure as described in claim 1～5 any one,It is characterized in that, comprise the following steps:

A) varigrained electrode active material is made into electrode material with auxiliary material respectively, then is mixed with electricity with electrolyteMany groups anode sizing agent that utmost point active material granularity is different; Or by the polyelectrolyte of different molecular weight and electrodeMaterial formulation becomes the different many groups positive electrode of polyelectrolyte molecular weight; By the many groups anode sizing agent preparingPress the gradient of electrode active material granularity, or the gradient of polyelectrolyte molecular weight is coated in colelctor electrode successivelySurface, obtains having the anodal layer of gradient-structure;

B) configuration electrolyte slurry, is coated in a) positive pole with gradient-structure of gained by described electrolyte slurryLayer surface, obtains dielectric substrate;

C) directly at described dielectric substrate surface adhesion metal electrode b); Must there is all solid state of gradient-structureLithium battery.