Negative electrode sheet, composite electrode sheet, solid-state battery, and manufacturing method

Abstract

The present application relates to the technical field of battery, in particular to a negative electrode sheet, a composite electrode sheet, a solid-state battery and a preparation method. The negative electrode sheet comprises a negative electrode current collector and a negative electrode coating arranged on the negative electrode current collector; the negative electrode coating comprises a negative electrode active layer arranged in the middle along the width direction of the negative electrode current collector and negative electrode insulation layers arranged on both sides of the negative electrode active layer. The present application solves the problems of electrode sheet deformation and powder falling through the synergistic scheme of "buffer type insulation coating + secondary coating process + optimized width design" from three dimensions.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a negative electrode, a composite electrode, a solid-state battery, and a method for preparing them. Background Technology

[0002] Solid-state lithium batteries, with their advantages of high safety and high energy density, have become the core development direction for next-generation power batteries. However, their commercialization is limited by the key issue of poor electrode structure stability, specifically manifested as electrode deformation and active material powder shedding. The root causes of this problem mainly include: 1) In the existing transfer composite process, the negative electrode electrolyte composite electrode sheet is subjected to external pressure during the subsequent isostatic pressing process, and the active material is easily squeezed and deformed, which leads to the destruction of the electrode sheet structure integrity. 2) When silicon anode material is used, it will produce significant volume expansion during the electrochemical reaction (the expansion rate can reach more than 300%). Repeated expansion and contraction will lead to a decrease in the binding force between the active material and the current collector and the active material particles, which will in turn cause the active material to fall off (powder shedding). 3) Electrode deformation and powder shedding can directly lead to the failure of contact between the electrode and the solid electrolyte membrane, resulting in a sharp increase in interfacial impedance and rapid capacity decay of the battery. At the same time, the detached active material particles may puncture the electrolyte membrane, causing an internal short circuit in the battery and seriously threatening battery safety.

[0003] 4) Sulfide electrolytes can oxidize copper foil current collectors: Sulfide electrolytes are extremely sensitive to humidity. Even in low-humidity environments, they can react with trace amounts of water to produce hydrogen sulfide. Hydrogen sulfide then reacts chemically with the copper foil current collector to form corrosion products such as copper sulfide. Furthermore, during charging and discharging, if the sulfide electrolyte comes into contact with the copper foil, the electrochemical potential difference at the interface between them can cause the copper to be oxidized into copper sulfide.

[0004] Existing technologies (such as transfer composite process and conventional roll forming integrated process) only focus on interface contact or overall structural integration, and do not propose a systematic solution to the core problem of electrode deformation and powder shedding. This results in poor long-term cycle stability and prominent safety hazards of solid-state batteries, making it difficult to meet the needs of commercial applications. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings and defects of the prior art and to provide a negative electrode, a composite electrode, a solid-state battery, and a preparation method thereof.

[0006] To achieve the above objectives, this application adopts the following solution: A negative electrode sheet includes a negative electrode current collector and a negative electrode coating disposed on the negative electrode current collector; the negative electrode coating includes a negative electrode active layer disposed in the middle along the width direction of the negative electrode current collector and negative electrode insulating layers disposed on both sides of the negative electrode active layer, the edge negative electrode insulating coating is in direct contact with the negative electrode active layer, which is beneficial for buffering the deformation of the active material of the negative electrode sheet after isostatic pressing, and also beneficial for mitigating the electrode sheet deformation caused by expansion during silicon reaction; the "double-sided wrapping" of the negative electrode active layer by the negative electrode insulating layer can suppress the expansion of silicon negative electrode from the edge direction and avoid lateral deformation of the active layer; The negative electrode current collector is a carbon-coated copper foil or a zinc-copper alloy foil, preferably a carbon-coated copper foil. The carbon-coated copper foil includes a copper foil body with a negative electrode carbon coating layer disposed on the copper foil body; the width of the negative electrode carbon coating layer is L2; ​​L4+L3≤L2. This ensures that the negative electrode carbon coating layer completely covers the negative electrode active layer, enhances adhesion, and prevents the foil from being oxidized after contacting the electrolyte; L2=290-310mm. The thickness of the negative electrode current collector is 4-12 μm; preferably, the thickness of the negative electrode carbon coating layer is 0.5-2 μm; the negative electrode carbon coating layer can enhance the adhesion to the negative electrode active layer, prevent the negative electrode active layer from falling off the negative electrode current collector, and reduce the risk of powder shedding.

[0007] The ratio of the thickness of the negative electrode insulating layer to the thickness of the negative electrode active layer is between 75% and 125%, preferably the two are the same, and preferably the thickness of the negative electrode insulating coating and the thickness of the negative electrode active coating are independently 15-60 μm.

[0008] The width of the negative electrode active layer is L4, preferably L4=280-290mm; the negative electrode active coating is the core reaction area of ​​the electrode sheet, and its width is smaller than that of the negative electrode carbon coating layer to avoid powder shedding caused by the lack of support at the edge of the negative electrode active layer. The width of the single-sided negative electrode insulating layer is L3. Preferably, L3 = 2-8 mm. L4 + 2L3 ≥ L5 (L5 is the width of the solid electrolyte membrane), ensuring that the negative electrode insulating layer extends beyond the solid electrolyte membrane (extension distance L = 0-5 mm), forming an "edge wrapping" of the negative electrode active layer; The present invention also includes a method for preparing the aforementioned negative electrode sheet, comprising the following steps: 1) applying a negative electrode active coating slurry and a negative electrode insulating layer slurry to the surface of the negative electrode current collector along the width direction of the negative electrode current collector; applying the negative electrode active layer onto the negative electrode current collector by extrusion coating, and forming a negative electrode insulating layer at its edge; 2) compacting the negative electrode sheet, with a rolling temperature of 60-100℃ and a pressure of 6 tons; preferably, a rolling temperature of 80℃ and a pressure of 6 tons; the porosity of the negative electrode sheet after rolling is 20%; reducing the porosity can enhance the structural density of the active layer and avoid the loosening of the active layer caused by excessive penetration of the slurry during subsequent electrolyte coating; Preferably, the negative electrode active coating slurry includes a negative electrode active material, a negative electrode electrolyte, a negative electrode conductive agent, and a negative electrode binder; the mass ratio of the negative electrode active material, negative electrode electrolyte, negative electrode conductive agent, and negative electrode binder is (30-98):(0-60):(0.5-10):(1-10), preferably 60:35:2:3; Preferably, the negative electrode active material is pure silicon, silicon oxide, graphite, silicon-carbon composite material, or lithium metal, with pure silicon being the preferred choice. More preferably, the negative electrode electrolyte is Li6PS5Cl. The presence of the negative electrode electrolyte helps mitigate the damage to the active material layer structure caused by volume changes during the silicon reaction process, thereby reducing powder shedding. Preferably, the negative electrode conductive agent is vapor-grown carbon fiber, and more preferably, the negative electrode binder is nitrile rubber. Preferably, the negative electrode insulating layer slurry comprises a metal oxide and an insulating layer binder; preferably, the mass ratio of the metal oxide to the insulating layer binder is 95:5; the metal oxide is magnesium oxide, and other binary oxides such as aluminum oxide and tin oxide; other multi-metal silicates such as magnesium aluminum spinel, boehmite, and kaolin; other composites of magnesium oxide and binary or multi-component compounds, etc.; the insulating layer binder is polyacrylic acid, polyvinylidene fluoride, polyisobutylene, nitrile rubber, hydrogenated nitrile rubber, fluororubber styrene-butadiene rubber, polyimide, polyacrylonitrile, etc., preferably polyisobutylene; As a preferred choice, magnesium oxide (average particle size 0.5-1μm) has low hardness (Mohs hardness 3.5), which allows it to undergo moderate deformation when the silicon anode expands, absorbing expansion stress (buffering deformation); at the same time, magnesium oxide has high insulation (breakdown voltage >10kV / mm), which can block short circuit channels; furthermore, magnesium oxide also has a certain adsorption capacity and can adsorb hydrogen sulfide. The insulating layer adhesive is polyacrylic acid, polyvinylidene fluoride, polyisobutylene, nitrile rubber, hydrogenated nitrile rubber, fluororubber styrene-butadiene rubber, polyimide, polyacrylonitrile, etc., with polyisobutylene being preferred.

[0009] The present invention also includes a composite electrode, comprising the aforementioned negative electrode and a solid electrolyte membrane disposed on the surface of the negative electrode.

[0010] The solid electrolyte membrane has a width of L5; L5 = 290-298 mm; and L4 + 2L3 ≥ L5; the solid electrolyte membrane is confined within the negative electrode insulating layer, and the expansion stress is dispersed through the negative electrode insulating coating, preventing the electrolyte layer from cracking. Preferably, the solid electrolyte membrane thickness is 20-100 μm.

[0011] The present invention also includes a method for preparing a composite electrode sheet, comprising the following steps: applying a solid electrolyte slurry to the surface of the negative electrode coating of the negative electrode sheet (which can be done by extrusion coating, gravure coating, transfer coating, or curtain coating, and the number of coatings can be 2, 3, 4, 5, 6, or 7 times, etc.), removing the solvent, and then performing roll pressing (preferably, the roll pressing temperature is 60°C and the pressure is 12 tons, which reduces the overall thickness of the composite electrode sheet and solidifies the solid electrolyte membrane), thereby solidifying the solid electrolyte membrane to obtain the composite electrode sheet; the solid electrolyte slurry is directly coated on the negative electrode active layer and the negative electrode insulating layer, and is tightly bonded to the negative electrode active layer, avoiding interface peeling caused by transfer printing. At the same time, the solid electrolyte membrane forms a top constraint on the negative electrode active layer, further suppressing expansion and deformation.

[0012] Preferably, the solid electrolyte slurry comprises a solid electrolyte and a binder, wherein the mass ratio of the solid electrolyte to the binder is (90-99.5):(0.5-10), preferably 98:2; Preferably, the solid electrolyte is Li6PS5Cl.

[0013] The present invention also includes a solid-state battery comprising the aforementioned composite electrode and a positive electrode; To further improve battery performance, the present invention also optimizes the design of the positive electrode sheet: the positive electrode sheet includes a positive current collector and a positive electrode coating; the positive electrode coating includes a positive active coating disposed in the middle along the width direction of the positive current collector and a positive insulating layer disposed on both sides of the positive active coating; The positive electrode insulating layer can form a "corresponding buffer" with the negative electrode insulating layer, avoiding pressure concentration on the negative electrode from the edge of the positive electrode after stacking, and preventing short circuits caused by active material shedding. This design ensures that the positive electrode material area corresponding to the negative electrode does not exceed the negative electrode material area, which is beneficial to long-term cycle stability; at the same time, it reduces the requirements for stacking alignment accuracy; in addition, the positive electrode insulating layer is easier to die-cut or even laser-cut relative to the material area, and is less prone to burrs, which is beneficial to improving cell safety.

[0014] Preferably, the positive current collector includes an aluminum foil and a positive electrode carbon coating layer disposed on the surface of the aluminum foil; the width of the positive electrode carbon coating layer is W7; the width of the positive electrode active layer is W9; and the width of the single-sided positive electrode insulating layer is W8. Preferably, W9 + W8 ≤ W7; Preferably, W9≤L4; ensuring that the positive electrode active layer completely covers the negative electrode active layer.

[0015] Preferably, W9 = 285-288mm; preferably, W8 = 3-5mm.

[0016] The positive electrode active coating slurry comprises a positive electrode active material, a positive electrode electrolyte, a positive electrode conductive agent, and a positive electrode binder; the mass ratio of the positive electrode active material, positive electrode electrolyte, positive electrode conductive agent, and positive electrode binder is (60-98):(0-30):(0.5-10):(1-10), preferably 88:8:2:2; the positive electrode active material is an 8-series ternary cathode; the positive electrode conductive agent is vapor-grown carbon fiber; the positive electrode binder is polyisobutylene; and the electrolyte is Li6PS5Cl. The inorganic ceramic is at least one of a binary oxide or a multi-metal silicate; preferably, the binary oxide includes at least one of magnesium oxide, aluminum oxide, or tin oxide; the multi-metal silicate includes at least one of magnesium aluminum spinel, boehmite, or kaolin; preferably boehmite; the insulating layer adhesive is polyacrylic acid, polyvinylidene fluoride, polyisobutylene, nitrile rubber, hydrogenated nitrile rubber, fluororubber styrene-butadiene rubber, polyimide, polyacrylonitrile, etc., preferably nitrile rubber.

[0017] The present invention also includes a method for preparing the solid-state battery, comprising the following steps: stacking the composite electrode and the positive electrode, encapsulating, and statically pressing to obtain the solid-state battery.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention addresses the problems of electrode deformation and powder shedding from three dimensions through a synergistic solution of "buffered insulating coating + secondary coating process + optimized width design": 1) Negative electrode structure: A buffer-type negative electrode insulating layer is set at the edge of the negative electrode active layer to provide expansion stress absorption and active material fixation function; the magnesium oxide in the negative electrode insulating layer has low hardness characteristics and can be used as a "flexible buffer layer". Under isostatic pressure or when the silicon negative electrode expands in volume, it undergoes moderate deformation to absorb external pressure and volume expansion stress, avoiding direct deformation of the electrode active layer. Experiments have verified that there is almost no powder shedding phenomenon in the electrode after isostatic pressing, and at the same time, there is almost no oxidation phenomenon in the copper foil current collector.

[0019] 2) Composite Electrode Structure: By optimizing the width relationship of each layer, the effective wrapping of the negative electrode active layer by the negative electrode insulating layer is ensured, while matching the positive electrode structure to avoid local stress concentration. The negative electrode insulating layer is in direct contact with the negative electrode active layer, forming an "edge wrapping" to prevent active material particles from falling off the electrode edge during expansion. After 20 cycles, the material loss rate is less than 1%, far superior to existing technologies (the material loss rate of conventional transfer printing processes exceeds 30%). The high voltage resistance of the negative electrode insulating layer can block local micro-short circuit channels. Combined with the design of the positive electrode edge insulating layer, the battery short circuit rate is reduced from "high" (over 15%) in existing technologies to "almost zero" (less than 0.5%).

[0020] 3) Composite Electrode Preparation Process: A two-stage coating process is adopted to avoid damage to the negative electrode caused by transfer printing. Simultaneously, pre-rolling of the negative electrode (rolling temperature 80℃, pressure 6 tons, reducing the porosity of the negative electrode active layer from 30% to 20% after rolling) controls porosity and enhances the structural stability of the electrode. The two-stage coating process avoids interface peeling problems during the transfer process, ensuring a direct and tight bond between the solid electrolyte membrane and the negative electrode active layer. Furthermore, the pre-rolling treatment controls porosity and prevents excessive miscibility between the electrolyte and the negative electrode. Improved Production Feasibility: No transfer printing process is required, increasing the production qualification rate from 50% with the existing transfer printing process to 90%. Attached Figure Description

[0021] Figure 1 This is an overall schematic diagram of the negative electrode sheet of the present invention; Figure 2 This is an overall schematic diagram of the composite electrode sheet of the present invention; Figure 3 This is an overall schematic diagram of the positive electrode sheet of the present invention; Figure 4 This is a schematic diagram of the solid-state battery of the present invention. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0023] Example 1: 1. Preparation of a negative electrode with an insulating coating: including the following steps: 11) Apply negative electrode active coating slurry and negative electrode insulating layer slurry to the surface of the negative electrode current collector along the width direction of the negative electrode current collector; apply negative electrode active layer to the negative electrode current collector by extrusion coating, and form negative electrode insulating layer at its edge; Negative electrode current collector: carbon-coated copper foil, 304 mm wide (L1=304 mm) Negative electrode active layer: The negative electrode active material is silicon, the negative electrode electrolyte is Li6PS5Cl, the negative electrode binder is nitrile rubber, and the negative electrode conductive agent is vapor-grown carbon fiber, with a mass ratio of 60:35:2:3. The width of the negative electrode active layer is 290 mm (L4=290 mm). Negative electrode insulating layer: Magnesium oxide slurry, applied by extrusion to both edges of the negative electrode active layer, with a width of 5mm on each side (L3=5mm): Magnesium oxide slurry preparation: Magnesium oxide powder (average particle size 0.5 μm) and binder polyisobutylene are dispersed in an alkane or ester solvent at a mass ratio of 95:5, with a solid content of 40%.

[0024] 12) Compact the negative electrode sheet; roll the prepared negative electrode sheet at a rolling temperature of 80℃ and a pressure of 6 tons. After rolling, the porosity of the negative electrode active layer decreased from 30% to 20%.

[0025] The resulting negative electrode sheet is as follows Figure 1 The diagram shows a negative current collector (including a copper foil body 1 and a negative electrode carbon coating layer 2 disposed on the copper foil body) and a negative electrode coating disposed on the negative current collector; the negative electrode coating includes a negative electrode active layer 4 disposed in the middle along the width direction of the negative current collector and negative electrode insulating layers 3 disposed on both sides of the negative electrode active layer. 2. Preparation of composite electrodes, 21) Apply a solid electrolyte slurry to the surface of the negative electrode coating of the negative electrode sheet; The solid electrolyte slurry was prepared by dispersing Li6PS5Cl sulfide electrolyte and nitrile rubber binder in heptane at a mass ratio of 98:2, with a solid content of 60%. The sulfide solid electrolyte slurry was then coated onto the negative electrode using extrusion coating.

[0026] The width of the solid electrolyte membrane is 298 mm (L5=298 mm), which satisfies L5≥L4 and L4+2L3≥L5.

[0027] 22) Composite electrode rolling: The prepared negative electrode and the composite electrode containing solid electrolyte are rolled together at a rolling temperature of 60°C and a pressure of 12 tons to make the composite electrode thinner and reduce the porosity.

[0028] The resulting composite electrode is as follows Figure 2 As shown, it includes a negative electrode sheet and a solid electrolyte membrane 5 disposed on the surface of the negative electrode sheet.

[0029] 3. Preparation of a positive electrode sheet with an insulating coating: including the following steps: 31) Apply a positive electrode active coating slurry and a positive electrode insulating layer slurry to the surface of the positive electrode current collector along the width direction of the positive electrode current collector; apply a positive electrode active layer to the positive electrode current collector by extrusion coating, and form a positive electrode insulating layer at its edge; the resulting positive electrode sheet Figure 3 The diagram shows a positive electrode current collector (including an aluminum foil body 6 and a positive electrode carbon coating layer 7 disposed on the aluminum foil body) and a positive electrode coating disposed on the positive electrode current collector; the positive electrode coating includes a positive electrode active layer 9 disposed in the middle along the width direction of the positive electrode current collector and positive electrode insulating layers 8 disposed on both sides of the positive electrode active layer.

[0030] Positive current collector: carbon-coated aluminum foil, with a carbon coating width of 302mm (W7=302mm). Positive electrode active layer: The main material of the positive electrode active material is 8-series ternary material, the positive electrode electrolyte is Li6PS5Cl, the positive electrode binder is polyisobutylene, and the positive electrode conductive agent is vapor-grown carbon fiber, with a ratio of 88:8:2:2. The width of the positive electrode active layer is 288 mm; W9 = 288 mm; Positive electrode insulating layer: Boehmite slurry, applied by extrusion to both sides of the positive electrode active layer, with a width of 5mm on each side (W8=5mm): Boehmite slurry preparation: Boehmite powder (average particle size 1μm) and binder polyisobutylene binder are dispersed in an alkane or ester solvent at a mass ratio of 95:5, with a solid content of 40%.

[0031] 4. Solid-state battery fabrication: The composite electrode sheet, obtained in step 3), is stacked (…). Figure 4 As shown, the stacked battery cell (including composite electrode 11 and positive electrode 10) is encapsulated and subjected to isostatic pressing (>400MPa) treatment, and then charged and discharged.

[0032] Comparative experiment To verify the advantages of this invention, a comparative experiment was conducted: Comparative Example 1: The composite electrode and corresponding battery cell were prepared using a traditional transfer composite process, including the following steps: 1. Preparation of a negative electrode sheet without insulating coating: including the following steps: 11) Applying a negative electrode active coating slurry to the surface of the negative electrode current collector along the width direction of the negative electrode current collector; applying a negative electrode active layer to the negative electrode current collector by extrusion coating; Negative current collector: carbon-coated copper foil, 304 mm wide (L1=304 mm). Negative electrode active layer: The negative electrode active material is silicon, the negative electrode electrolyte is Li6PS5Cl, the negative electrode binder is nitrile rubber, and the negative electrode conductive agent is vapor-grown carbon fiber, with a mass ratio of 60:35:2:3. The width of the negative electrode active layer is 290mm (L4=290mm).

[0033] 2. Preparation of solid electrolyte membrane: including the following steps: 11) Apply solid electrolyte coating slurry to the surface of aluminum foil current collector in the width direction of aluminum foil current collector; apply electrolyte slurry to aluminum foil current collector by extrusion coating; the solid electrolyte in the solid electrolyte coating is Li6PS5Cl, the binder is nitrile rubber, and the ratio is 98:2.

[0034] The coating width of the electrolyte slurry is 298 mm (L5=298 mm). 3. Preparation of composite electrode. The electrolyte electrode is transferred onto the negative electrode by roller transfer printing to prepare a composite electrode of negative electrode and electrolyte; 4. Preparation of a positive electrode sheet without insulating coating: including the following steps: 11) Applying a positive active coating slurry to the surface of the positive current collector along the width direction of the positive current collector; applying a positive active layer to the positive current collector by extrusion coating; Positive current collector: carbon-coated aluminum foil, 302mm wide (M6=302mm); Positive electrode active layer: The main material of the positive electrode is 8-series ternary material, the electrolyte is Li6PS5Cl, the binder is polyisobutylene, and the conductive agent is vapor-grown carbon fiber, with a ratio of 88:8:2:2. The width of the positive electrode active layer is 288 mm; W9 = 288 mm; 5. Solid-state battery fabrication: The composite electrode sheet and the positive electrode sheet obtained in step 4 are stacked together, the stacked cells are encapsulated and subjected to isostatic pressing (>400MPa), and the cells are charged and discharged.

[0035] Comparative Example 2: Based on Example 1, but with a secondary coated composite electrode sheet and corresponding battery cell without an insulating coating on the negative electrode; 1. Preparation of a negative electrode sheet without insulating coating: including the following steps: 11) Applying a negative electrode active coating slurry to the surface of the negative electrode current collector along the width direction of the negative electrode current collector; applying a negative electrode active layer to the negative electrode current collector by extrusion coating; Negative electrode current collector: carbon-coated copper foil, 304 mm wide (L1=304 mm) Negative electrode active layer: The active material is silicon, the negative electrode electrolyte is Li6PS5Cl, the negative electrode binder is nitrile rubber, and the negative electrode conductive agent is vapor-grown carbon fiber, with a mass ratio of 60:35:2:3. The width of the negative electrode active layer is 290mm (L4=290mm); 12) Compact the negative electrode sheet; roll the prepared negative electrode sheet at a rolling temperature of 80℃ and a pressure of 6 tons. After rolling, the porosity of the negative electrode active layer decreased from 30% to 20%.

[0036] 2. Preparation of composite electrodes, 21) A solid electrolyte slurry is coated on the surface of the negative electrode coating of the negative electrode sheet; wherein, the electrolyte slurry is prepared by dispersing Li6PS5Cl sulfide electrolyte and nitrile rubber binder in heptane at a mass ratio of 98:2, with a solid content of 60%. The sulfide solid electrolyte slurry is coated onto the negative electrode sheet by extrusion coating.

[0037] 22) Composite electrode rolling: The prepared negative electrode and electrolyte composite electrode is rolled at a rolling temperature of 60℃ and a pressure of 12 tons to make the composite electrode thinner and reduce the porosity.

[0038] 3. Preparation of a positive electrode sheet with an insulating coating: including the following steps: 31) Apply positive active coating slurry and positive insulating layer slurry to the surface of the positive current collector along the width direction of the positive current collector; apply positive active layer to the positive current collector by extrusion coating, and form positive insulating layer at its edge; Positive current collector: carbon-coated aluminum foil, 302mm wide (W7=302mm); Positive electrode active layer: The main active material is an 8-series ternary material, the positive electrode electrolyte is Li6PS5Cl, the positive electrode binder is polyisobutylene, and the positive electrode conductive agent is vapor-grown carbon fiber, in a ratio of 88:8:2:2. The width of the positive electrode active layer is 288 mm; W9 = 288 mm; Positive electrode insulating layer: Boehmite slurry, applied by extrusion to both edges of the positive electrode active layer, with a width of 5mm on each side (W8=5mm): Boehmite slurry preparation: Boehmite powder (average particle size 1μm) and binder polyisobutylene are dispersed in an alkane or ester solvent at a mass ratio of 95:5, with a solid content of 40%.

[0039] 4. Solid-state battery fabrication: The composite electrode sheet and the positive electrode sheet obtained in step 3) are stacked, the stacked cells are packaged and subjected to isostatic pressing (>400MPa), and the cells are charged and discharged.

[0040] Comparative Example 3: Based on Example 1, a composite electrode sheet and corresponding battery cell that were not rolled before electrolyte coating on the negative electrode; 1. Preparation of a negative electrode with an insulating coating: including the following steps: 11) Apply negative electrode active coating slurry and negative electrode insulating layer slurry to the surface of the negative electrode current collector along the width direction of the negative electrode current collector; apply negative electrode active layer to the negative electrode current collector by extrusion coating, and form negative electrode insulating layer at its edge; Negative electrode current collector: carbon-coated copper foil, 304 mm wide (L1=304 mm) The negative electrode active material is silicon, the negative electrode electrolyte is Li6PS5Cl, the negative electrode binder is nitrile rubber, and the negative electrode conductive agent is vapor-grown carbon fiber, with a mass ratio of 60:35:2:3. The width of the negative electrode active layer is 290 mm (L4=290 mm). Negative electrode insulating layer: magnesium oxide slurry, which is applied to both sides of the negative electrode active layer by extrusion coating, with a width of 5 mm on each side (L3=5 mm): Preparation of magnesium oxide slurry: magnesium oxide powder (average particle size 0.5 μm) and binder polyisobutylene are dispersed in an alkane or ester solvent at a mass ratio of 95:5, with a solid content of 40%.

[0041] 2. Preparation of composite electrodes, 21) A solid electrolyte slurry is coated on the surface of the negative electrode coating of the negative electrode sheet; wherein, the solid electrolyte slurry is prepared by dispersing Li6PS5Cl sulfide electrolyte and nitrile rubber binder in heptane at a mass ratio of 98:2, with a solid content of 60%. The sulfide solid electrolyte slurry is coated onto the negative electrode sheet by extrusion coating.

[0042] The width of the solid electrolyte membrane is 298 mm (L5=298 mm), which satisfies L5≥L4 and L4+2L3≥L5; 22) Composite electrode rolling: The prepared negative electrode and electrolyte composite electrode is rolled at a rolling temperature of 60℃ and a pressure of 12 tons to make the composite electrode thinner and reduce the porosity.

[0043] 3. Preparation of positive electrode sheet with insulating coating: including the following steps: 11) Apply positive active coating slurry and positive insulating layer slurry to the surface of positive current collector in the width direction of positive current collector; apply positive active layer to positive current collector by extrusion coating, and form positive insulating layer at its edge; Positive current collector: carbon-coated aluminum foil, 302mm wide (W7=302mm) Positive electrode active layer: The main material of the positive electrode active material is 8-series ternary material, the positive electrode electrolyte is Li6PS5Cl, the positive electrode binder is polyisobutylene, and the positive electrode conductive agent is vapor-grown carbon fiber, with a ratio of 88:8:2:2. The width of the positive electrode active layer is 288 mm; W9 = 288 mm; Boehmite slurry for positive electrode insulation layer is applied to both edges of the positive electrode active layer by extrusion coating, with a width of 5mm on each side (W8=5mm): Boehmite slurry preparation: Boehmite powder (average particle size 1μm) and binder polyisobutylene are dispersed in an alkane or ester solvent at a mass ratio of 95:5, with a solid content of 40%.

[0044] 4. Solid-state battery fabrication: The composite electrode sheet and the positive electrode sheet obtained in step 3) are stacked, the stacked cells are packaged and subjected to isostatic pressing (>400MPa), and the cells are charged and discharged.

[0045] Comparative Example 4: Based on Example 1, a composite electrode with a secondary coating matching the coating and the corresponding battery cell is designed with a positive electrode without an insulating coating. 1. Preparation of a negative electrode with an insulating coating: including the following steps: 11) Apply negative electrode active coating slurry and negative electrode insulating layer slurry to the surface of the negative electrode current collector along the width direction of the negative electrode current collector; apply negative electrode active layer to the negative electrode current collector by extrusion coating, and form negative electrode insulating layer at its edge; Negative electrode current collector: carbon-coated copper foil, 304 mm wide (L1=304 mm) Negative electrode active layer: The negative electrode active material is silicon, the negative electrode electrolyte is Li6PS5Cl, the negative electrode binder is nitrile rubber, and the negative electrode conductive agent is vapor-grown carbon fiber, with a mass ratio of 60:35:2:3. The width of the negative electrode active layer is 290 mm (L4=290 mm). Negative electrode insulating layer: Magnesium oxide slurry, applied by extrusion to both edges of the negative electrode active layer, with a width of 5mm on each side (L3=5mm): Magnesium oxide slurry preparation: Magnesium oxide powder (average particle size 0.5 μm) and binder polyisobutylene are dispersed in an alkane or ester solvent at a mass ratio of 95:5, with a solid content of 40%.

[0046] 12) Compact the negative electrode sheet; roll the prepared negative electrode sheet at a rolling temperature of 80℃ and a pressure of 6 tons. After rolling, the porosity of the negative electrode active layer decreased from 30% to 20%.

[0047] 2. Preparation of composite electrodes, 21) A solid electrolyte slurry is coated on the surface of the negative electrode coating of the negative electrode sheet; wherein, the electrolyte slurry is prepared by dispersing Li6PS5Cl sulfide electrolyte and nitrile rubber binder in heptane at a mass ratio of 98:2, with a solid content of 60%. The sulfide solid electrolyte slurry is coated onto the negative electrode sheet by extrusion coating, and the width of the electrolyte layer is 298mm (L5=298mm), satisfying the requirements that L5≥L4 and L4+2L3≥L5.

[0048] 22) Composite electrode rolling: The prepared negative electrode and electrolyte composite electrode is rolled at a rolling temperature of 60℃ and a pressure of 12 tons to make the composite electrode thinner and reduce the porosity.

[0049] 3. Preparation of a positive electrode without an insulating coating: including the following steps: 31) Apply a positive electrode active coating slurry to the surface of the positive electrode current collector along the width direction of the positive electrode current collector; apply a positive electrode active layer to the positive electrode current collector by extrusion coating. Positive current collector: carbon-coated aluminum foil, 302mm wide (W7=302mm); Positive electrode active layer: The main material of the positive electrode is 8-series ternary material, the electrolyte is Li6PS5Cl, the binder is polyisobutylene, and the conductive agent is vapor-grown carbon fiber, with a ratio of 88:8:2:2. 4. Solid-state battery fabrication: Composite electrode sheets are stacked with positive electrode sheets, the stacked cells are encapsulated and subjected to isostatic pressing (>400MPa), and the cells are charged and discharged.

[0050] Comparative Example 5: Based on Example 1, the negative electrode insulating material used is aluminum oxide.

[0051] 1. Preparation of a negative electrode with an insulating coating: including the following steps: 11) Apply negative electrode active coating slurry and negative electrode insulating layer slurry to the surface of the negative electrode current collector along the width direction of the negative electrode current collector; apply negative electrode active layer to the negative electrode current collector by extrusion coating, and form negative electrode insulating layer at its edge; Negative electrode active layer: The negative electrode active material is silicon, the negative electrode electrolyte is Li6PS5Cl, the negative electrode binder is nitrile rubber, and the negative electrode conductive agent is vapor-grown carbon fiber, with a mass ratio of 60:35:2:3. The width of the negative electrode active layer is 290 mm (L4=290 mm). Negative electrode insulating layer: alumina slurry, applied by extrusion coating on both sides of the negative electrode active layer, with a width of 5mm on each side (L3=5mm): Alumina slurry preparation: alumina powder (average particle size 1μm) and binder polyisobutylene are dispersed in an alkane or ester solvent at a mass ratio of 95:5, with a solid content of 40%.

[0052] 12) Compact the negative electrode sheet; roll the prepared negative electrode sheet at a rolling temperature of 80℃ and a pressure of 6 tons. After rolling, the porosity of the negative electrode active layer decreased from 30% to 20%.

[0053] 2. Preparation of composite electrodes; 21) A solid electrolyte slurry is coated on the surface of the negative electrode coating of the negative electrode sheet; wherein, the electrolyte slurry is prepared by dispersing Li6PS5Cl sulfide electrolyte and nitrile rubber binder in heptane at a mass ratio of 98:2, with a solid content of 60%. The sulfide solid electrolyte slurry is coated onto the negative electrode sheet by extrusion coating, and the width of the electrolyte layer is 298mm (L5=298mm), satisfying the requirements that L5≥L4 and L4+2L3≥L5.

[0054] 22) Composite electrode rolling: The prepared negative electrode and electrolyte composite electrode is rolled at a rolling temperature of 60℃ and a pressure of 12 tons to make the composite electrode thinner and reduce the porosity.

[0055] 3. Preparation of a positive electrode sheet with an insulating coating: including the following steps: 31) Apply positive active coating slurry and positive insulating layer slurry to the surface of the positive current collector along the width direction of the positive current collector; apply positive active layer to the positive current collector by extrusion coating, and form positive insulating layer at its edge; Positive current collector: carbon-coated aluminum foil, 302mm wide (W7=302mm) Positive electrode active layer: The main material of the positive electrode active material is 8-series ternary material, the positive electrode electrolyte is Li6PS5Cl, the positive electrode binder is polyisobutylene, and the positive electrode conductive agent is vapor-grown carbon fiber, with a ratio of 88:8:2:2. The width of the positive electrode active layer is 288 mm; W9 = 288 mm; Positive electrode insulating layer: Boehmite slurry, applied by extrusion to both edges of the positive electrode active layer, with a width of 5mm on each side (M8=5mm): Boehmite slurry preparation: Boehmite powder (average particle size 1μm) and binder polyisobutylene are dispersed in an alkane or ester solvent at a mass ratio of 95:5, with a solid content of 40%.

[0056] 4. Solid-state battery fabrication: Composite electrode sheets are stacked with positive electrode sheets, the stacked cells are encapsulated and subjected to isostatic pressing (>400MPa), and the cells are charged and discharged.

[0057] Table 2 shows a comparison of the performance of composite electrodes prepared by different methods. It should be noted that the embodiments and comparative examples of the present invention are only for convenient comparison, and the comparative examples are also part of the embodiments.

[0058] Table 2

[0059] Experimental results show that the composite electrode prepared by the method of the present invention is significantly superior to the comparative example in terms of interface performance, oxidation of copper foil current collector, powder shedding after isostatic pressing, short circuit rate, and material shedding after 20 cycles.

[0060] In summary, this invention solves the problems of electrode deformation and powder shedding from three dimensions through a synergistic solution of "buffered insulating coating + secondary coating process + optimized width design".

[0061] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, the embodiments should be regarded as exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of the equivalents of the claims be included within the invention.

[0062] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A negative electrode sheet, characterized in that, It includes a negative current collector and a negative electrode coating disposed on the negative current collector; the negative electrode coating includes a negative electrode active layer disposed in the middle along the width direction of the negative current collector and negative electrode insulating layers disposed on both sides of the negative electrode active layer, the width of the negative electrode active coating is L4, and the width of the single-sided negative electrode insulating layer is L3.

2. The negative electrode sheet according to claim 1, characterized in that, The negative electrode current collector is a carbon-coated copper foil or a zinc-copper alloy foil, preferably a carbon-coated copper foil; the carbon-coated copper foil includes a copper foil body with a negative electrode carbon coating layer disposed on the copper foil body; the width of the negative electrode carbon coating layer is L2; ​​preferably, L4+L3≤L2.

3. The negative electrode sheet according to claim 2, characterized in that, The thickness of the negative electrode current collector is 4-12 μm; preferably, the thickness of the negative electrode carbon coating layer is 0.5-2 μm; the ratio of the thickness of the negative electrode insulating layer to the thickness of the negative electrode active layer is between 75% and 125%, preferably the two are the same, and preferably, the thickness of the negative electrode insulating layer and the thickness of the negative electrode active layer are independently 15-60 μm.

4. The negative electrode sheet according to claim 2, characterized in that, The L2 is 290-310mm; preferably, L4 is 280-290mm; preferably, L3 is 2-8mm.

5. A method for preparing a negative electrode sheet according to any one of claims 1-4, characterized in that, The process includes the following steps: 1) Applying a negative electrode active coating slurry and a negative electrode insulating layer slurry to the surface of the negative electrode current collector along the width direction of the current collector; preferably, the negative electrode active layer is applied to the negative electrode current collector by extrusion coating, and a negative electrode insulating layer is formed at its edge; 2) Compacting the negative electrode sheet; the rolling temperature is 60-100℃, and the pressure is 6 tons; preferably, the rolling temperature is 80℃, and the pressure is 6 tons; the porosity of the negative electrode sheet after rolling is 20%; Preferably, the negative electrode active coating slurry includes a negative electrode active material, a negative electrode conductive agent, a negative electrode electrolyte, and a negative electrode binder; the mass ratio of the negative electrode active material, negative electrode electrolyte, negative electrode conductive agent, and negative electrode binder is (30-98):(0-60):(0.5-10):(1-10), preferably 60:35:2:

3. Preferably, the negative electrode active material is pure silicon, silicon oxide, graphite, silicon-carbon composite material or lithium metal, preferably pure silicon; preferably, the negative electrode conductive agent is vapor-grown carbon fiber; preferably, the negative electrode binder is nitrile rubber; preferably, the negative electrode electrolyte is Li6PS5Cl. Preferably, the negative electrode insulating layer slurry comprises inorganic ceramics and an insulating layer binder; preferably, the mass ratio of the metal oxide and the insulating layer binder is (1-98):(2-98), more preferably 95:5; the inorganic ceramic is at least one of a binary oxide or a multi-metal silicate; preferably, the binary oxide comprises at least one of magnesium oxide, aluminum oxide, or tin oxide; the multi-metal silicate comprises at least one of magnesium aluminum spinel, boehmite, or kaolin; the insulating layer binder is polyacrylic acid, polyvinylidene fluoride, polyisobutylene, nitrile rubber, hydrogenated nitrile rubber, fluororubber styrene-butadiene rubber, polyimide, polyacrylonitrile, preferably polyisobutylene.

6. A composite electrode, characterized in that, It includes the negative electrode sheet as described in any one of claims 1-4 and the solid electrolyte membrane disposed on the surface of the negative electrode sheet.

7. The composite electrode according to claim 6, characterized in that, The width of the solid electrolyte membrane is L5; L5 = 290-298 mm; and L4 + 2L3 ≥ L5; preferably, the thickness of the solid electrolyte membrane is 20-100 μm.

8. A method for preparing a composite electrode, characterized in that, The process includes the following steps: applying a solid electrolyte slurry to the surface of the negative electrode coating of the negative electrode sheet, removing the solvent, rolling and bonding, and curing the solid electrolyte membrane to obtain a composite electrode sheet. Preferably, the solid electrolyte slurry comprises a solid electrolyte and a binder, wherein the mass ratio of the solid electrolyte to the binder is (90-99.5):(0.5-10), preferably 98:2; Preferably, the solid electrolyte is Li6PS5Cl.

9. A solid-state battery, comprising the composite electrode and a positive electrode as described in claim 6 or 7; Preferably, the positive electrode sheet includes a positive current collector and a positive electrode coating; the positive electrode coating includes a positive active coating disposed in the middle along the width direction of the positive current collector and a positive insulating layer disposed on both sides of the positive active coating; Preferably, the positive current collector includes an aluminum foil and a positive electrode carbon coating layer disposed on the surface of the aluminum foil; the width of the positive electrode carbon coating layer is W7; the width of the positive electrode active coating layer is W9; and the width of the single-sided positive electrode insulating layer is W8. Preferably, W9 + W8 ≤ W7; Preferably, W9≤L4; Preferably, W9 = 285-288mm; preferably, W8 = 3-5mm. The positive electrode active coating slurry comprises a positive electrode active material, a positive electrode electrolyte, a positive electrode conductive agent, and a positive electrode binder; the mass ratio of the positive electrode active material, positive electrode electrolyte, positive electrode conductive agent, and positive electrode binder is (60-98):(0-30):(0.5-10):(1-10), preferably 88:8:2:2, the positive electrode active material is an 8-series ternary electrode, the positive electrode conductive agent is vapor-grown carbon fiber, the positive electrode binder is polyisobutylene, and the positive electrode electrolyte is Li6PS5Cl; Preferably, the positive electrode insulating layer slurry comprises inorganic ceramics and an insulating layer binder; preferably, the mass ratio of the inorganic ceramics to the insulating layer binder is (60-98):(4-40), more preferably 95:5; the inorganic ceramics are at least one of binary oxides or multi-metal silicates; preferably, the binary oxides include at least one of magnesium oxide, aluminum oxide, or tin oxide; the multi-metal silicates include at least one of magnesium aluminum spinel, boehmite, or kaolin; preferably boehmite; the insulating layer binder is polyacrylic acid, polyvinylidene fluoride, polyisobutylene, nitrile rubber, hydrogenated nitrile rubber, fluororubber styrene-butadiene rubber, polyimide, polyacrylonitrile, etc., preferably nitrile rubber.

10. A method for preparing a solid-state battery according to claim 9, characterized in that, The process includes the following steps: stacking the composite electrode and the positive electrode, encapsulating, and statically pressing to obtain a solid-state battery.

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