Composite electrode plate and preparation method and application thereof

Abstract

The invention provides a composite electrode pole piece and a preparation method and application thereof, and the preparation method comprises the following steps: coating the surface of at least one side of a current collector with electrode slurry to obtain an electrode slurry coating, and coating the surface of the electrode slurry coating with solid electrolyte slurry when the electrode slurry coating is not dry to obtain the composite electrode pole piece. And then drying and rolling to obtain the composite electrode plate. According to the preparation method, after the electrode slurry is coated, the solid electrolyte slurry is coated when the electrode slurry is not dry, and the solid electrolyte layer is obtained on the surface of the electrode coating, so that the problem of internal interface contact of the electrode plate is solved, the problem of external interface contact of the electrode plate is also solved, the impedance of the solid-state battery is reduced, and the service life of the solid-state battery is prolonged. And the rate and the cycle performance of the solid-state battery are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and relates to a composite electrode sheet, a preparation method thereof and an application thereof. Background Art

[0002] Lithium-ion batteries have developed rapidly due to advantages such as high energy density and long cycle life, and are widely used in consumer electronics, electric vehicles and large-scale energy storage power stations. Most commercially available lithium-ion battery products currently use liquid electrolytes, which have approached the energy density limit, and there are also problems such as electrolyte leakage and battery short circuit. Moreover, when there is an internal or external short circuit, an adverse exothermic reaction may cause the internal temperature to rise rapidly and thermal runaway, which will bring serious safety hazards. All-solid-state batteries avoid the use of organic liquid electrolytes and can improve the safety problems of lithium-ion batteries. However, problems such as difficult film formation of solid electrolytes, poor compatibility between solid electrolytes and positive and negative electrodes, and low ionic conductivity of electrolyte membranes are still bottlenecks restricting the development and application of all-solid-state batteries.

[0003] Currently, the research focus of the prior art mainly concentrates on improving the ionic conductivity of solid electrolytes. However, the interfacial problem of difficult compatibility between solid electrolytes and electrodes is the key to solving the practical application of all-solid-state batteries. The specific reasons are as follows: Most of the existing preparation processes of all-solid-state batteries use transfer printing. After coating an electrolyte layer on a substrate such as a film such as PET or aluminum foil, it is then transferred to the electrode, or a solid electrolyte membrane is directly prepared using a non-woven fabric separator. In order to make the electrode layer and the solid electrolyte layer contact tightly, an isostatic pressing method is usually used. However, in all-solid-state batteries, the contact between the solid electrolyte layer and the electrode layer is rigid, and there is a huge ion transport impedance between the two phases, and the interfacial problem still cannot be completely solved. At the same time, this interfacial impedance will continuously accumulate during the battery cycle, resulting in an increase in internal polarization of the battery until it fails.

[0004] Based on the above research, it is necessary to provide a composite electrode sheet, which can improve the cycle stability of the battery, reduce the impedance, and effectively improve the interfacial problem of all-solid-state batteries. Summary of the Invention

[0005] The purpose of the present invention is to provide a composite electrode sheet, a preparation method thereof and an application thereof. After coating the electrode paste, the solid electrolyte paste is coated when the electrode paste is not dry, and a solid electrolyte layer is obtained on the surface of the electrode coating, which solves both the internal interfacial contact problem of the electrode sheet and the external interfacial contact problem of the electrode sheet, reduces the impedance of the solid-state battery, and improves the rate and cycle performance of the solid-state battery.

[0006] To achieve the purpose of this invention, the following technical solutions are adopted by the present invention:

[0007] In a first aspect, the present invention provides a method for preparing a composite electrode sheet, and the preparation method includes the following steps:

[0008] Coat an electrode slurry on at least one surface of a current collector to obtain an electrode slurry coating. When the electrode slurry coating is not dry, coat a solid electrolyte slurry on the surface of the electrode slurry coating, and then perform drying and rolling to obtain the composite electrode sheet.

[0009] Preferably, the method of coating the solid electrolyte slurry includes electrostatic spraying.

[0010] Preferably, the electrostatic spraying is carried out at a dew point temperature of -60 to -40 °C.

[0011] Preferably, the voltage of the electrostatic spraying is 8 - 12 KV.

[0012] Preferably, the distance from the nozzle of the electrostatic spraying to the surface of the electrode slurry coating is 5 - 20 cm.

[0013] Preferably, the spray width of the electrostatic spraying < 30 cm.

[0014] Preferably, the coating thickness of the solid electrolyte slurry is 10 - 20 μm.

[0015] Preferably, the thickness of the electrode slurry coating is 50 - 150 μm.

[0016] Preferably, the type of solvent used in the solid electrolyte slurry is the same as the type of solvent used in the electrode slurry.

[0017] Preferably, the type of binder used in the solid electrolyte slurry is the same as the type of binder used in the electrode slurry.

[0018] Preferably, the solid electrolyte slurry includes a first solid electrolyte, a first binder, and a first solvent.

[0019] Preferably, the mass ratio of the first solid electrolyte to the first binder is (97 - 99):(1 - 3).

[0020] Preferably, the viscosity of the solid electrolyte slurry is 1000 - 3000 cp.

[0021] Preferably, the electrode slurry includes a positive electrode slurry or a negative electrode slurry.

[0022] Preferably, the positive electrode slurry includes a positive electrode active material, a second solid electrolyte, a conductive agent, a second binder, and a second solvent.

[0023] Preferably, in the positive electrode paste, the mass ratio of the positive electrode active material, the second solid electrolyte, the conductive agent, and the second binder is (60 - 90):(10 - 40):(1 - 2):(1 - 3).

[0024] Preferably, the negative electrode paste includes a negative electrode active material, a third solid electrolyte, a conductive agent, a third binder, and a third solvent.

[0025] Preferably, in the negative electrode paste, the mass ratio of the negative electrode active material, the third solid electrolyte, the conductive agent, and the third binder is (60 - 90):(10 - 40):(1 - 2):(1 - 3).

[0026] Preferably, the first solid electrolyte, the second solid electrolyte, and the third solid electrolyte each independently include any one or a combination of at least two of a sulfide solid electrolyte, a halide solid electrolyte, or an oxide solid electrolyte, wherein the sulfide solid electrolyte includes Li 10 GeP 2 S 12 、Li 7 P 3 S 11 、Li 6 PS 5 X (X includes Cl, Br), or Li 2 S - P 2 S 5 or any one or a combination of at least two thereof; the halide solid electrolyte includes Li 2 MnCl 4 and / or Li 2 ZnCl 4 ; the oxide solid electrolyte includes LLZO (Li 7 La 3 Zr 2 O 12 ), LAGP (Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 ), or LATP (Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 ) or any one or a combination of at least two thereof.

[0027] Preferably, the particle sizes D50 of the first solid electrolyte, the second solid electrolyte, and the third solid electrolyte are each independently 3 - 6 μm.

[0028] Preferably, the positive electrode active material includes any one or a combination of at least two of lithium cobaltate, ternary material, lithium iron phosphate, lithium-rich manganese-based material, or spinel-type lithium manganate.

[0029] Preferably, the negative electrode active material includes any one or a combination of at least two of graphite, amorphous carbon, lithium titanate, SiO x / C composite material or Sn-based composite material.

[0030] Preferably, the conductive agent includes any one or a combination of at least two of carbon black, conductive graphite, carbon fiber, carbon nanotube, or graphene.

[0031] Preferably, the second binder includes an oily binder, such as any one or a combination of at least two of polyvinylidene fluoride, polyimide, or polytetrafluoroethylene.

[0032] Preferably, the third binder includes an aqueous binder, such as any one or a combination of at least two of styrene-butadiene rubber, carboxymethyl cellulose, or polyvinyl alcohol.

[0033] Preferably, the first binder includes the oily binder or the aqueous binder, which is determined by whether it is coated on the surface of the positive electrode slurry coating or the surface of the negative electrode slurry coating.

[0034] Preferably, the drying temperature is 70 - 100 °C and the time is 9 - 15 h.

[0035] In a second aspect, the present invention provides a composite electrode sheet, and the composite electrode sheet is prepared by using the preparation method as described in the first aspect.

[0036] Preferably, the composite electrode sheet includes a current collector, an electrode coating on at least one surface of the current collector, and a solid electrolyte layer on the surface of the electrode coating.

[0037] Preferably, the electrode coating and the solid electrolyte layer penetrate each other at the contact point.

[0038] Preferably, the thickness of the solid electrolyte layer is 5 - 15 μm.

[0039] Preferably, the thickness of the electrode coating is 40 - 140 μm.

[0040] Preferably, the solid electrolyte layer includes a first solid electrolyte and a first binder with a mass ratio of (97 - 99):(1 - 3).

[0041] Preferably, the electrode coating includes a positive active material, a second solid electrolyte, a conductive agent, and a second binder with a mass ratio of (60-90):(10-40):(1-2):(1-3), or includes a negative active material, a third solid electrolyte, a conductive agent, and a third binder with a mass ratio of (60-90):(10-40):(1-2):(1-3).

[0042] In a third aspect, the present invention provides a all-solid-state battery, which includes the composite electrode sheet as described in the second aspect, and the composite electrode sheet includes a composite positive electrode sheet and a composite negative electrode sheet.

[0043] Preferably, the all-solid-state battery includes a composite negative electrode sheet, a composite positive electrode sheet, and a composite negative electrode sheet that are sequentially stacked. Among them, the composite positive electrode sheet includes a positive current collector, positive active coatings on both sides of the positive current collector, and a positive-side solid electrolyte layer on the surface of the positive active coatings. The composite negative electrode sheet includes a negative current collector, a negative active coating on one side of the negative current collector, and a negative-side solid electrolyte layer on the surface of the negative active coating. The negative-side solid electrolyte layer is attached to the positive-side solid electrolyte layer.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] On the one hand, by coating a layer of solid electrolyte layer on the surface of the electrode paste coating in the present invention, during the assembly process of the all-solid-state battery, the contact between the traditional electrode sheet and the solid electrolyte layer is transformed into the contact between the solid electrolyte layers, improving the interface problem of the all-solid-state battery. On the other hand, the present invention coats the solid electrolyte layer paste when the electrode paste coating is not dry, solves the internal contact problem of the composite electrode sheet, and reduces the interface effect between the electrode coating and the solid electrolyte layer. Therefore, the present invention can effectively improve the interface performance of the all-solid-state battery and enhance the performance such as rate and cycle of the all-solid-state battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 is a schematic structural diagram of the all-solid-state battery of the present invention;

[0047] Among them, 11-negative current collector, 12-negative active material layer, 21-positive current collector, 22-positive active material layer, 31-negative-side solid electrolyte layer, 32-positive-side solid electrolyte layer. DETAILED DESCRIPTION OF THE INVENTION

[0048] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0049] In a specific embodiment, the present invention provides a method for preparing a composite electrode sheet, and the preparation method includes the following steps:

[0050] Coat an electrode paste on at least one surface of a current collector to obtain an electrode paste coating. When the electrode paste coating is not dry, coat a solid electrolyte paste on the surface of the electrode paste coating, and then perform drying and rolling to obtain the composite electrode sheet.

[0051] When the present invention prepares the electrode sheet, a solid electrolyte paste is coated, and the solid electrolyte paste is coated when the electrode paste coating is not dry, that is, the electrode paste coating is a wet film, so that partial penetration can be achieved at the place where the electrode paste and the solid electrolyte paste contact. If the solid electrolyte paste is directly coated on the surface of the electrode sheet after drying and rolling, there is still an interface problem between the electrode coating and the solid electrolyte layer. Therefore, the present invention solves the contact problem between the electrode coating and the solid electrolyte layer inside the composite electrode sheet.

[0052] After the present invention coats the solid electrolyte paste, a solid electrolyte layer can be formed on the surface of the electrode coating. During the assembly process of the all-solid-state battery, the contact between the traditional electrode sheet and the solid electrolyte layer is converted into the contact between the solid electrolyte layers, which improves the interface problem of the all-solid-state battery. That is, the present invention also solves the problem of external interface contact of the electrode sheet. Therefore, the present invention solves both the internal interface contact problem and the external interface contact problem of the electrode sheet, effectively improves the interface performance of the all-solid-state battery, optimizes the interface stability, reduces the impedance of the all-solid-state battery, and improves the rate and cycle performance of the all-solid-state battery.

[0053] In some embodiments, the method of coating the solid electrolyte paste includes electrostatic spraying.

[0054] In the prior art, the methods for coating the solid electrolyte paste generally include a direct coating process and an atomic layer deposition technique. Among them, the direct coating process is to directly coat the solid electrolyte paste on the electrode sheet. This method has a simple preparation process, but it is difficult to precisely control the thickness of the solid electrolyte layer, the thickness is relatively thick, and the uniformity is poor. The atomic layer deposition technique can achieve uniform coating, but the speed is slow and the equipment cost is high. Therefore, the present invention adopts an electrostatic spraying technique. Through the electrostatic spraying technique, an ultra-thin solid electrolyte layer is sprayed, and the solid electrolyte material is uniformly coated on the surface of the electrode coating, which can make the solid electrolyte layers on the positive electrode side and the negative electrode side in close contact, increase the lithium ion conductivity, improve the cycle stability and capacity of the battery, and effectively improve the interface problem of the all-solid-state battery.

[0055] In some embodiments, the electrostatic spraying is carried out at a dew point temperature of -60 to -40 °C, for example, it can be -60 °C, -50 °C or -40 °C, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0056] In some embodiments, the voltage of the electrostatic spraying is 8 - 12 KV, for example, it can be 8 KV, 9 KV, 10 KV, 11 KV or 12 KV, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0057] In some embodiments, the distance from the nozzle of the electrostatic spraying to the surface of the electrode paste coating is 5 - 20 cm, for example, it can be 5 cm, 10 cm, 15 cm or 20 cm, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0058] In some embodiments, the spray width of the electrostatic spraying < 30 cm, for example, it can be 25 cm, 20 cm, 15 cm, 10 cm or 5 cm, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0059] The spray width of the electrostatic spraying described in the present invention refers to the width of the fan-shaped area formed by the atomized coating sprayed by the spray gun.

[0060] In some embodiments, the coating thickness of the solid electrolyte paste is 10 - 20 μm, for example, it can be 5 μm, 10 μm, 15 μm or 20 μm, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0061] The coating thickness of the solid electrolyte paste described in the present invention matches the coating method when the electrode paste coating is not dry, which not only ensures the internal contact problem of the solid electrolyte layer in the composite electrode pole piece, but also ensures the external contact problem of the solid electrolyte layer in the composite electrode pole piece. It is preferably coated within a specific range. If the coating thickness is too small, it is difficult to effectively prepare due to process limitations. If the coating thickness is too large, the energy density and power density of the battery will decrease.

[0062] In some embodiments, the thickness of the electrode paste coating is 50 - 150 μm, for example, it can be 50 μm, 100 μm or 150 μm, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0063] In some embodiments, the types of solvents used in the solid electrolyte paste are the same as those used in the electrode paste.

[0064] In some embodiments, the types of binders used in the solid electrolyte paste are the same as those used in the electrode paste.

[0065] The composite electrode sheet described in the present invention can be a composite positive electrode sheet or a composite negative electrode sheet. Different types of electrode slurries use different types of binders. Therefore, in order to match different types of electrode sheets, the type of binder in the solid electrolyte slurry varies with different types of electrode sheets.

[0066] In some embodiments, the solid electrolyte slurry includes a first solid electrolyte, a first binder, and a first solvent.

[0067] In some embodiments, the mass ratio of the first solid electrolyte to the first binder is (97 - 99):(1 - 3). For example, it can be 97:3, 98:2, or 99:1, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0068] In some embodiments, the viscosity of the solid electrolyte slurry is 1000 - 3000 cp. For example, it can be 1000 cp, 2000 cp, or 3000 cp, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0069] In some embodiments, the electrode slurry includes a positive electrode slurry or a negative electrode slurry.

[0070] In some embodiments, the positive electrode slurry includes a positive electrode active material, a second solid electrolyte, a conductive agent, a second binder, and a second solvent.

[0071] In some embodiments, in the positive electrode slurry, the mass ratio of the positive electrode active material, the second solid electrolyte, the conductive agent, and the second binder is (60 - 90):(10 - 40):(1 - 2):(1 - 3). For example, it can be 60:35:2:3, 70:20:1.5:2, 80:10:1:1, or 90:30:2:3, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0072] In some embodiments, the negative electrode slurry includes a negative electrode active material, a third solid electrolyte, a conductive agent, a third binder, and a third solvent.

[0073] In some embodiments, in the negative electrode slurry, the mass ratio of the negative electrode active material, the third solid electrolyte, the conductive agent, and the third binder is (60 - 90):(10 - 40):(1 - 2):(1 - 3). For example, it can be 60:35:2:3, 70:20:1.5:2, 80:10:1:1, or 90:30:2:3, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0074] In some embodiments, the first solid-state electrolyte, the second solid-state electrolyte, and the third solid-state electrolyte each independently comprise any one or a combination of at least two of a sulfide solid-state electrolyte, a halide solid-state electrolyte, or an oxide solid-state electrolyte, wherein the sulfide solid-state electrolyte comprises Li 10 GeP 2 S 12 、Li 7 P 3 S 11 、Li 6 PS 5 X (X includes Cl, Br), or Li 2 S-P 2 S 5 or any combination of at least two thereof; the halide solid-state electrolyte comprises Li 2 MnCl 4 and / or Li 2 ZnCl 4 ; the oxide solid-state electrolyte comprises LLZO (Li 7 La 3 Zr 2 O 12 ), LAGP (Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 ), or LATP (Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 ) or any combination of at least two thereof.

[0075] In some embodiments, the D50 particle sizes of the first solid-state electrolyte, the second solid-state electrolyte, and the third solid-state electrolyte are each independently 3 - 6 μm, for example, they can be 3 μm, 4 μm, 5 μm, or 6 μm, but are not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0076] In some embodiments, the positive electrode active material comprises any one or a combination of at least two of lithium cobaltate, ternary material, lithium iron phosphate, lithium-rich manganese-based material, or spinel-type lithium manganate.

[0077] In some embodiments, the negative electrode active material comprises any one or a combination of at least two of graphite, amorphous carbon, lithium titanate, SiO x / C composite material, or Sn-based composite material.

[0078] In some embodiments, the conductive agent includes any one or a combination of at least two of carbon black, conductive graphite, carbon fiber, carbon nanotubes, or graphene.

[0079] In some embodiments, the second binder includes an oily binder, such as any one or a combination of at least two of polyvinylidene fluoride, polyimide, or polytetrafluoroethylene.

[0080] In some embodiments, the third binder includes an aqueous binder, such as any one or a combination of at least two of styrene-butadiene rubber, carboxymethyl cellulose, or polyvinyl alcohol.

[0081] In some embodiments, the first binder includes the oily binder or the aqueous binder, which is determined by whether it is coated on the surface of the positive electrode paste coating or the surface of the negative electrode paste coating.

[0082] In some embodiments, the first solvent, the second solvent, and the third solvent include p-xylene.

[0083] In some embodiments, the drying temperature is 70 - 100 °C, for example, it can be 70 °C, 80 °C, 90 °C, or 100 °C, and the time is 9 - 15 h, for example, it can be 9 h, 11 h, 13 h, or 15 h, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0084] In a specific embodiment, the present invention further provides a composite electrode sheet, which includes a current collector, an electrode coating on at least one surface of the current collector, and a solid electrolyte layer on the surface of the electrode coating.

[0085] In some embodiments, the electrode coating and the solid electrolyte layer penetrate each other at the contact area.

[0086] Since the solid electrolyte paste of the present invention is coated when the electrode paste coating is not dried, in the finally obtained composite electrode sheet, the electrode coating and the solid electrolyte layer will penetrate each other at the contact area, thereby improving the interfacial contact between the electrode coating and the solid electrolyte layer.

[0087] In some embodiments, the thickness of the solid electrolyte layer is 5 - 15 μm, for example, it can be 5 μm, 8 μm, 10 μm, 12 μm, or 15 μm, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0088] The solid electrolyte layer of the present invention is preferably within a specific thickness range. If the coating thickness is too small, it is restricted by the preparation process, and it is difficult to prepare a thinner solid electrolyte layer. If the coating thickness is too large, the energy density and power density of the battery will decrease.

[0089] In some embodiments, the thickness of the electrode coating is 40 - 140 μm, for example, it can be 40 μm, 80 μm, 120 μm or 140 μm, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0090] In some embodiments, the solid electrolyte layer includes a first solid electrolyte and a first binder with a mass ratio of (97 - 99):(1 - 3), for example, it can be 97:3, 98:2 or 99:1, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0091] In some embodiments, the electrode coating includes a positive electrode active material, a second solid electrolyte, a conductive agent and a second binder with a mass ratio of (60 - 90):(10 - 40):(1 - 2):(1 - 3), for example, it can be 60:35:2:3, 70:20:1.5:2, 80:10:1:1 or 90:30:2:3, or includes a negative electrode active material, a third solid electrolyte, a conductive agent and a third binder with a mass ratio of (60 - 90):(10 - 40):(1 - 2):(1 - 3), for example, it can be 60:35:2:3, 70:20:1.5:2, 80:10:1:1 or 90:30:2:3, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0092] In order to match different types of electrode sheets, the type of binder in the solid electrolyte layer should vary with different types of electrode sheets. When the electrode coating in the present invention is a positive electrode coating, the binder used in the solid electrolyte layer is the same as that in the positive electrode coating, preferably an oily binder. When the electrode coating in the present invention is a negative electrode coating, the binder used in the solid electrolyte layer is the same as that in the negative electrode coating, preferably an aqueous binder.

[0093] In a specific embodiment, the present invention provides a all - solid - state battery, and the all - solid - state battery includes the composite electrode sheet as described above, and the composite electrode sheet includes a composite positive electrode sheet and a composite negative electrode sheet.

[0094] In some embodiments, the all - solid - state battery includes a composite negative electrode sheet, a composite positive electrode sheet and a composite negative electrode sheet stacked in sequence. Among them, the composite positive electrode sheet includes a positive electrode current collector, positive electrode active coatings on both sides of the positive electrode current collector, and a positive electrode side solid electrolyte layer on the surface of the positive electrode active coatings; the composite negative electrode sheet includes a negative electrode current collector, a negative electrode active coating on one side of the negative electrode current collector, and a negative electrode side solid electrolyte layer on the surface of the negative electrode active coating, and the negative electrode side solid electrolyte layer is attached to the positive electrode side solid electrolyte layer.

[0095] Example 1

[0096] This embodiment provides a all-solid-state battery, and the structural schematic diagram of the all-solid-state battery is as Figure 1 shown, including a composite positive electrode sheet, a composite negative electrode sheet and a composite positive electrode sheet which are stacked in sequence. The composite positive electrode sheet includes a positive current collector 21, positive active material layers 22 on both sides of the positive current collector 21, and a positive-side solid electrolyte layer 32 on the surface of the positive active material layer 22. The composite negative electrode sheet includes a negative current collector 11, a negative active material layer 12 on one side of the negative current collector 11, and a negative-side solid electrolyte layer 31 on the surface of the negative active material layer 12. Among them, the positive-side solid electrolyte layer 32 and the negative-side solid electrolyte layer 31 are adhered to each other.

[0097] The preparation methods of the composite positive electrode sheet and the composite negative electrode sheet include the following steps:

[0098] (1) Mix a solid electrolyte (specifically Li 6 PS 5 Cl), an oily binder (specifically PVDF) and p-xylene to obtain a positive-side solid electrolyte slurry. Among them, the mass ratio of the solid electrolyte to the oily binder is 98:2;

[0099] Mix NCM811, a solid electrolyte (specifically Li 6 PS 5 Cl), VGCF, an oily binder (specifically PVDF) and p-xylene to obtain a positive electrode slurry. Among them, the mass ratio of NCM811, the solid electrolyte, VGCF and the oily binder is 80:15:2:3;

[0100] Coat the positive electrode slurry on both sides of a positive current collector (specifically aluminum foil) to obtain a positive electrode slurry coating with a thickness of 100 μm. When the positive electrode slurry coating is not dry, electrostatically spray a positive-side solid electrolyte slurry with a thickness of 15 μm on the surface of the positive electrode slurry coating. Among them, the electrostatic spraying is carried out at a dew point temperature of -50 °C, the voltage of the electrostatic spraying is 10 KV, the distance from the nozzle to the surface of the electrode slurry coating is 15 cm, the spray width is 20 cm, and then it is dried at 80 °C for 12 h. After rolling, a composite positive electrode sheet is obtained. The composite positive electrode sheet includes a positive current collector, positive active coatings on both sides of the positive current collector, and a positive-side solid electrolyte layer on the surface of the positive active coatings;

[0101] (2) Mix a solid electrolyte (specifically Li 6 PS 5 Cl), an aqueous binder (specifically styrene-butadiene rubber) and p-xylene to obtain a negative-side solid electrolyte slurry. Among them, the mass ratio of the solid electrolyte to the aqueous binder is 98:2;

[0102] Mix silicon material, solid electrolyte (specifically Li 6 PS 5 Cl), VGCF, aqueous binder (specifically styrene-butadiene rubber), and p-xylene to obtain a negative electrode slurry. Among them, the mass ratio of silicon material, solid electrolyte, VGCF, and aqueous binder is 80:15:2:3;

[0103] Coat the negative electrode slurry on one side of a negative electrode current collector (specifically copper foil) to obtain a negative electrode slurry coating with a thickness of 80 μm. When the negative electrode slurry coating is not dry, electrostatically spray a negative electrode side solid electrolyte slurry with a thickness of 15 μm on the surface of the negative electrode slurry coating. Among them, the electrostatic spraying is carried out at a dew point temperature of -50°C, the voltage of electrostatic spraying is 10 KV, the distance from the nozzle to the surface of the electrode slurry coating is 15 cm, the spray width is 20 cm, and then dry at 100°C for 12 h. After rolling, a composite negative electrode sheet is obtained. The composite negative electrode sheet includes a negative electrode current collector, a negative electrode active material layer on one side of the negative electrode current collector, and a negative electrode side solid electrolyte layer on the surface of the negative electrode active material layer.

[0104] Example 2

[0105] This example provides a all-solid-state battery. The all-solid-state battery includes a composite positive electrode sheet, a composite negative electrode sheet, and a composite positive electrode sheet stacked in sequence. The composite positive electrode sheet includes a positive electrode current collector, positive electrode active material layers on both sides of the positive electrode current collector, and a positive electrode side solid electrolyte layer on the surface of the positive electrode active material layer. The composite negative electrode sheet includes a negative electrode current collector, a negative electrode active material layer on one side of the negative electrode current collector, and a negative electrode side solid electrolyte layer on the surface of the negative electrode active material layer. Among them, the positive electrode side solid electrolyte layer and the negative electrode side solid electrolyte layer are adhered to each other.

[0106] The preparation methods of the composite positive electrode sheet and the composite negative electrode sheet include the following steps:

[0107] (1) Mix solid electrolyte (specifically Li 6 PS 5 Cl), oily binder (specifically PVDF), and p-xylene to obtain a positive electrode side solid electrolyte slurry. Among them, the mass ratio of solid electrolyte and oily binder is 99:1;

[0108] Mix NCM811, solid electrolyte (specifically Li 6 PS 5 Cl), VGCF, oily binder (specifically PVDF), and p-xylene to obtain a positive electrode slurry. Among them, the mass ratio of NCM811, solid electrolyte, VGCF, and oily binder is 80:15:2:3;

[0109] The positive electrode paste is coated on both sides of the positive electrode current collector (specifically aluminum foil) to obtain a positive electrode paste coating with a thickness of 120 μm. When the positive electrode paste coating is not dry, a positive electrode side solid electrolyte paste with a thickness of 20 μm is electrostatically sprayed on the surface of the positive electrode paste coating. Among them, the electrostatic spraying is carried out at a dew point temperature of -60 °C, the voltage of the electrostatic spraying is 12 KV, the distance from the nozzle to the surface of the electrode paste coating is 20 cm, and the spray width is 25 cm. Then it is dried at 100 °C for 9 h. After rolling, a composite positive electrode sheet is obtained. The composite positive electrode sheet includes a positive electrode current collector, positive electrode active coatings on both sides of the positive electrode current collector, and a positive electrode side solid electrolyte layer on the surface of the positive electrode active coatings;

[0110] (2) The solid electrolyte (specifically Li 6 PS 5 Cl), an aqueous binder (specifically styrene-butadiene rubber), and p-xylene are mixed to obtain a negative electrode side solid electrolyte paste. Among them, the mass ratio of the solid electrolyte to the aqueous binder is 99:1;

[0111] Silicon material, solid electrolyte (specifically Li 6 PS 5 Cl), VGCF, an aqueous binder (specifically styrene-butadiene rubber), and p-xylene are mixed to obtain a negative electrode paste. Among them, the mass ratio of the silicon material, the solid electrolyte, VGCF, and the aqueous binder is 80:15:2:3;

[0112] The negative electrode paste is coated on one side of the negative electrode current collector (specifically copper foil) to obtain a negative electrode paste coating with a thickness of 100 μm. When the negative electrode paste coating is not dry, a negative electrode side solid electrolyte paste with a thickness of 20 μm is electrostatically sprayed on the surface of the negative electrode paste coating. Among them, the electrostatic spraying is carried out at a dew point temperature of -60 °C, the voltage of the electrostatic spraying is 12 KV, the distance from the nozzle to the surface of the electrode paste coating is 20 cm, and the spray width is 25 cm. Then it is dried at 70 °C for 15 h. After rolling, a composite negative electrode sheet is obtained. The composite negative electrode sheet includes a negative electrode current collector, a negative electrode active material layer on one side of the negative electrode current collector, and a negative electrode side solid electrolyte layer on the surface of the negative electrode active material layer.

[0113] Example 3

[0114] This embodiment provides an all-solid-state battery, which includes a composite positive electrode sheet, a composite negative electrode sheet, and a composite positive electrode sheet stacked in sequence. The composite positive electrode sheet includes a positive current collector, positive active material layers on both sides of the positive current collector, and a positive-side solid electrolyte layer on the surface of the positive active material layer. The composite negative electrode sheet includes a negative current collector, a negative active material layer on one side of the negative current collector, and a negative-side solid electrolyte layer on the surface of the negative active material layer. Among them, the positive-side solid electrolyte layer and the negative-side solid electrolyte layer are adhered to each other.

[0115] The preparation methods of the composite positive electrode sheet and the composite negative electrode sheet include the following steps:

[0116] (1) Mix a solid electrolyte (specifically Li 6 PS 5 Cl), an oily binder (specifically PVDF), and p-xylene to obtain a positive-side solid electrolyte slurry. Among them, the mass ratio of the solid electrolyte to the oily binder is 97:3;

[0117] Mix NCM811, a solid electrolyte (specifically Li 6 PS 5 Cl), VGCF, an oily binder (specifically PVDF), and p-xylene to obtain a positive electrode slurry. Among them, the mass ratio of NCM811, the solid electrolyte, VGCF, and the oily binder is 90:10:1:1;

[0118] Coat the positive electrode slurry on both sides of a positive current collector (specifically aluminum foil) to obtain a positive electrode slurry coating with a thickness of 100 μm. When the positive electrode slurry coating is not dry, electrostatically spray a positive-side solid electrolyte slurry with a thickness of 10 μm on the surface of the positive electrode slurry coating. Among them, the electrostatic spraying is carried out at a dew point temperature of -40°C, the voltage of the electrostatic spraying is 8 KV, the distance from the nozzle to the surface of the electrode slurry coating is 5 cm, the spray width is 15 cm, and then it is dried at 70°C for 15 h. After rolling, a composite positive electrode sheet is obtained, which includes a positive current collector, positive active coatings on both sides of the positive current collector, and a positive-side solid electrolyte layer on the surface of the positive active coatings;

[0119] (2) Mix a solid electrolyte (specifically Li 6 PS 5 Cl), an aqueous binder (specifically styrene-butadiene rubber), and p-xylene to obtain a negative-side solid electrolyte slurry. Among them, the mass ratio of the solid electrolyte to the aqueous binder is 97:3;

[0120] Mix silicon material, a solid electrolyte (specifically Li 6 PS 5(Cl), VGCF, an aqueous binder (specifically styrene-butadiene rubber), and p-xylene are mixed to obtain a negative electrode slurry. Among them, the mass ratio of the silicon material, solid electrolyte, VGCF, and aqueous binder is 90:10:1:1;

[0121] The negative electrode slurry is coated on one side of a negative electrode current collector (specifically copper foil) to obtain a negative electrode slurry coating with a thickness of 100 μm. When the negative electrode slurry coating is not dry, a negative electrode side solid electrolyte slurry with a thickness of 10 μm is electrostatically sprayed on the surface of the negative electrode slurry coating. Among them, the electrostatic spraying is carried out at a dew point temperature of -40°C, the voltage of the electrostatic spraying is 8 KV, the distance from the nozzle to the surface of the electrode slurry coating is 5 cm, the spray width is 15 cm, and then it is dried at 70°C for 15 h. After rolling, a composite negative electrode sheet is obtained. The composite negative electrode sheet includes a negative electrode current collector, a negative electrode active material layer on one side of the negative electrode current collector, and a negative electrode side solid electrolyte layer on the surface of the negative electrode active material layer.

[0122] Example 4

[0123] This example provides a all-solid-state battery. Except that in the preparation methods of the composite positive electrode sheet and the composite negative electrode sheet, the thickness of the electrostatic spraying in steps (1) and (2) is 30 μm, the rest are the same as those in Example 1.

[0124] Example 5

[0125] This example provides a all-solid-state battery. Except that in the preparation methods of the composite positive electrode sheet and the composite negative electrode sheet, in steps (1) and (2), the solid electrolyte slurry is coated by a direct coating method instead of electrostatic spraying, the rest are the same as those in Example 1.

[0126] Comparative Example 1

[0127] This comparative example provides a all-solid-state battery. Except that in the preparation methods of the composite positive electrode sheet and the composite negative electrode sheet, after the positive electrode slurry coating in step (1) and the negative electrode slurry coating in step (2) are dried and rolled, a positive electrode side solid electrolyte slurry and a negative electrode side solid electrolyte slurry are respectively electrostatically sprayed, the rest are the same as those in Example 1.

[0128] Comparative Example 2

[0129] This comparative example provides a all-solid-state battery. Except that the solid electrolyte membrane therein is obtained by spraying the positive electrode side solid electrolyte slurry described in Example 1 onto a glass substrate by the electrostatic spraying method described in Example 1 to obtain a solid electrolyte membrane with a thickness of 30 μm, and in the preparation methods of the composite positive electrode sheet and the composite negative electrode sheet, steps (1) and (2) are not sprayed with the solid electrolyte layer slurry, the rest are the same as in Example 1.

[0130] The all-solid-state batteries obtained from the above examples and comparative examples were tested for their electrochemical performance. The charge-discharge conditions were as follows: constant current and constant voltage charging at 1C until 4.2V, and the charging cut-off current was 0.05C; constant current discharge at 1C until 2.6V. The test results are shown in Table 1:

[0131] Table 1

[0132]

[0133] As can be seen from Table 1:

[0134] (1) From Example 1 and Comparative Example 1, it can be seen that when the present invention coats the solid electrolyte slurry when the electrode slurry coating is not dry, it can improve the interface problem between the electrode coating inside the composite electrode sheet and the solid electrolyte layer, thereby reducing the impedance of the all-solid-state battery and improving the rate and cycle performance of the all-solid-state battery; from Example 1 and Comparative Example 2, it can be seen that when the present invention converts the contact between the electrode sheet and the solid electrolyte membrane into the contact between the solid electrolyte layers, it can effectively solve the interface problem of the all-solid-state battery, thereby reducing the impedance of the all-solid-state battery and improving the cycle and rate performance of the all-solid-state battery.

[0135] (2) From Example 1 and Example 4, it can be seen that the thickness of the solid electrolyte layer of the present invention affects the performance of the all-solid-state battery, preferably within a specific range; from Example 1 and Example 5, it can be seen that when the present invention preferably uses the electrostatic spraying method to coat the solid electrolyte slurry, it can make the positive electrode side solid electrolyte layer and the negative electrode side solid electrolyte layer in close contact, reduce the impedance of the all-solid-state battery, and improve the rate and cycle performance of the all-solid-state battery.

[0136] In summary, the present invention provides a composite electrode sheet, its preparation method and application. After coating the electrode slurry, the solid electrolyte slurry is coated when the electrode slurry is not dry, and a solid electrolyte layer is obtained on the surface of the electrode coating, which solves both the internal interface contact problem of the electrode sheet and the external interface contact problem of the electrode sheet, reduces the impedance of the solid-state battery, and improves the rate and cycle performance of the solid-state battery.

[0137] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for preparing a composite electrode sheet, characterized in that: The preparation method comprises the following steps: The electrode slurry is coated on at least one side of the current collector to obtain an electrode slurry coating. When the electrode slurry coating is not dry, a solid electrolyte slurry is coated on the surface of the electrode slurry coating, and then dried and rolled to obtain the composite electrode plate.

2. The preparation method according to claim 1, characterized in that: The method of applying the solid electrolyte slurry includes electrostatic spraying; Preferably, the electrostatic spraying is carried out at a dew point temperature of -60 to -40°C; Preferably, the voltage of the electrostatic spraying is 8-12KV; Preferably, the distance from the electrostatic spraying nozzle to the electrode slurry coating surface is 5-20 cm; Preferably, the spray width of the electrostatic spraying is less than 30 cm.

3. The preparation method according to claim 1 or 2, characterized in that: The coating thickness of the solid electrolyte slurry is 10-20 μm; Preferably, the thickness of the electrode slurry coating is 50-150 μm; Preferably, the type of solvent used in the solid electrolyte slurry is the same as the type of solvent used in the electrode slurry; Preferably, the type of binder used in the solid electrolyte slurry is the same as the type of binder used in the electrode slurry.

4. The preparation method according to any one of claims 1 to 3, characterized in that The solid electrolyte slurry includes a first solid electrolyte, a first binder and a first solvent; Preferably, the mass ratio of the first solid electrolyte to the first binder is (97-99):(1-3); Preferably, the viscosity of the solid electrolyte slurry is 1000-3000cp.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The electrode slurry includes positive electrode slurry or negative electrode slurry; Preferably, the positive electrode slurry comprises a positive electrode active material, a second solid electrolyte, a conductive agent, a second binder and a second solvent; Preferably, in the positive electrode slurry, the mass ratio of the positive electrode active material, the second solid electrolyte, the conductive agent and the second binder is (60-90):(10-40):(1-2):(1-3).

6. The preparation method according to claim 5, characterized in that: The negative electrode slurry includes a negative electrode active material, a third solid electrolyte, a conductive agent, a third binder and a third solvent; Preferably, in the negative electrode slurry, the mass ratio of the negative electrode active material, the third solid electrolyte, the conductive agent and the third binder is (60-90):(10-40):(1-2):(1-3); Preferably, the drying temperature is 70-100° C. and the drying time is 9-15 h.

7. A composite electrode plate, characterized in that: The composite electrode plate is prepared by the preparation method according to any one of claims 1 to 6.

8. The composite electrode plate according to claim 7, characterized in that: The composite electrode plate comprises a current collector, an electrode coating on at least one side of the current collector, and a solid electrolyte layer on the surface of the electrode coating; Preferably, the electrode coating and the solid electrolyte layer interpenetrate each other at the contact point; Preferably, the thickness of the solid electrolyte layer is 5-15 μm; Preferably, the thickness of the electrode coating is 40-140 μm; Preferably, the solid electrolyte layer comprises a first solid electrolyte and a first binder in a mass ratio of (97-99):(1-3); Preferably, the electrode coating comprises a positive electrode active material, a second solid electrolyte, a conductive agent and a second binder in a mass ratio of (60-90):(10-40):(1-2):(1-3), or comprises a negative electrode active material, a third solid electrolyte, a conductive agent and a third binder in a mass ratio of (60-90):(10-40):(1-2):(1-3).

9. An all-solid-state battery, characterized in that: The all-solid-state battery comprises the composite electrode plate as claimed in claim 7 or 8, wherein the composite electrode plate comprises a composite positive electrode plate and a composite negative electrode plate.

10. The all-solid-state battery according to claim 9, characterized in that: The all-solid-state battery comprises a composite negative electrode sheet, a composite positive electrode sheet and a composite negative electrode sheet which are stacked in sequence, wherein the composite positive electrode sheet comprises a positive electrode current collector, a positive electrode active coating on both sides of the positive electrode current collector and a positive electrode side solid electrolyte layer on the surface of the positive electrode active coating; the composite negative electrode sheet comprises a negative electrode current collector, a negative electrode active coating on one side of the negative electrode current collector and a negative electrode side solid electrolyte layer on the surface of the negative electrode active coating, and the negative electrode side solid electrolyte layer is bonded to the positive electrode side solid electrolyte layer.

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