A method for preparing a high-load lithium ion battery anode sheet and application thereof

Abstract

The application provides a high-load lithium ion battery positive plate preparation method and application, a positive electrode material adopts a step-by-step coating process to construct a functional gradient double-layer positive electrode structure, first, a first slurry containing a large-particle-size hollow structure positive electrode material and a polyacrylic polymer is prepared, coated on the surface of an aluminum foil and dried to form an inner layer; then, a second slurry containing a small-particle-size dense structure positive electrode material is prepared, coated on the upper side of the inner layer and dried to form an outer layer. The thickness of the inner layer is less than that of the outer layer, and the overall surface load of the positive plate is controlled in a set range. The inner layer constructs electrolyte permeation and liquid retention channels, and the outer layer improves the active material load, the gradient structure still maintains good ion transmission capacity under high compaction density, improves the electrolyte wetting performance, cycle stability and capacity retention rate of the battery, and solves the problems of difficult electrolyte wetting, ion transmission obstruction and long liquid injection standing time of the traditional single uniform coating high-load positive plate.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery cathode material technology, and more specifically, it relates to a method for preparing and applying a high-load lithium-ion battery cathode sheet. Background Technology

[0002] As lithium-ion batteries advance towards higher energy densities, the loading and compaction of the positive electrode are continuously increasing. However, this leads to a decrease in the porosity of the electrode and a longer ion transport path, making it difficult for the electrolyte to quickly penetrate the electrode. This results in a prolonged settling time after electrolyte injection, affecting production efficiency, and even creating "dry zones" within the electrode, leading to a decrease in the utilization rate of active materials. Traditional single-coating processes produce a relatively uniform pore structure distribution, making it difficult to simultaneously achieve high compaction, high electrolyte retention, and rapid wetting performance.

[0003] Therefore, there is an urgent need to develop a positive electrode structure and its preparation method that can take into account high actual density, fast electrolyte wetting performance and excellent liquid retention performance under high load conditions. Summary of the Invention

[0004] This invention provides a method for preparing a high-load lithium-ion battery positive electrode and its application, aiming to solve the technical problem that traditional positive electrodes suffer from reduced porosity and prolonged ion transport paths, leading to difficulties in rapid electrolyte penetration into the electrode interior. This, in turn, results in increased post-filling settling time, reduced production efficiency, and even the formation of dry areas within the electrode interior. The high-load lithium-ion battery positive electrode preparation method and its application provided by this invention achieve its objectives and benefits through the following specific technical means: A method for preparing a high-load lithium-ion battery cathode includes the following steps: S1: Prepare two positive electrode slurries with different pore structure characteristics respectively; S11: The first slurry uses a hollow structure cathode material with a larger particle size, and polyacrylic acid polymers are added during the homogenization process; S12: The second slurry uses a dense structure cathode material with a smaller particle size; S2: The first slurry is coated on the surface of the aluminum foil current collector, dried, and then the second slurry is coated on top of the first slurry layer to form a double-layer positive electrode layer.

[0005] According to a preferred embodiment, in step S2, the coating thickness of the first slurry is 40-70% smaller than the coating thickness of the second slurry.

[0006] According to a preferred embodiment, in step S11, the particle size D50 of the positive electrode material in the first slurry is in the range of 10-15 μm, and the hollow pore size is 0.5-2 μm.

[0007] According to a preferred embodiment, the polyacrylic polymer is one or a mixture of two of polyacrylic acid emulsion or polyacrylate emulsion.

[0008] According to a preferred embodiment, in step S12, the particle size D50 of the positive electrode material in the second slurry is in the range of 4-6 μm.

[0009] According to a preferred embodiment, the cathode material is one or a mixture of two of the following: ternary materials or lithium-rich manganese-based materials.

[0010] According to a preferred embodiment, the overall areal loading of the prepared positive electrode sheet is 20-50 mg / cm².

[0011] The application of a high-load lithium-ion battery positive electrode sheet in lithium-ion batteries, whereby the lithium-ion battery positive electrode sheet is used as a positive electrode component in lithium-ion batteries.

[0012] Compared with the prior art, the present invention has the following beneficial effects: 1. The dual-layer structure design achieves functional synergy between the inner and outer layers. The inner layer uses a large-particle-size hollow cathode material, which reduces the tortuosity of ion transport and provides a continuous channel for electrolyte to penetrate into the electrode. At the same time, polyacrylic acid polymers are added during the homogenization process. The carboxyl structure on the molecular chain can enhance the electrode's affinity for electrolyte and improve its liquid retention performance. The synergistic effect of the two can improve the electrolyte penetration rate and liquid retention capacity of the electrode under high load conditions, reduce the formation of dry areas inside the electrode, and the structural design of the inner layer coating thickness being smaller than that of the outer layer can further promote the electrolyte to penetrate deeper into the electrode, solving the problems of difficult electrolyte wetting and long standing time after electrolyte injection in traditional high-load electrodes.

[0013] 2. By employing a dual-layer structure, the energy density and electrochemical performance of the electrode are simultaneously optimized. The upper layer utilizes a small-particle-size, dense cathode material, which increases the content of active material per unit thickness while maintaining good wetting properties, thereby enhancing the areal capacity of the electrode. Simultaneously, this gradient structure maintains suitable porosity and ion transport capabilities even under high compaction conditions, avoiding the ion transport obstruction problem caused by decreased porosity in traditional single-coating high-load electrodes. During charge-discharge cycles, stable ion transport channels and sufficient electrolyte supply improve battery cycle stability and enhance capacity retention. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the double-layer positive electrode layer in this invention; Figure 2 This is a flowchart of the steps involved in preparing a high-load lithium-ion battery cathode sheet according to the present invention. Detailed Implementation

[0015] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate the technical solutions of the present invention, but should not be used to limit the scope of protection of the present invention.

[0016] Example:

[0017] As attached Figures 1 to 2 As shown: This invention provides a method for preparing a high-load lithium-ion battery cathode, comprising the following steps: S1: Prepare two positive electrode slurries with different pore structure characteristics.

[0018] S11: The first slurry uses a hollow structure cathode material with a larger particle size, and polyacrylic acid polymers are added during the homogenization process.

[0019] In this embodiment, the first slurry is used to form the inner positive electrode layer near the aluminum foil current collector, undertaking the core functions of constructing electrolyte penetration channels and improving the electrolyte retention capacity of the electrode. The positive electrode material is one or a mixture of two of the following: ternary materials or lithium-rich manganese-based materials. Both ternary materials and lithium-rich manganese-based materials have high theoretical specific capacities to meet the requirements of high-energy-density lithium-ion batteries. The particle size D50 of the positive electrode material in the first slurry is in the range of 10-15 μm. After the positive electrode material particles in this particle size range are stacked, they can form larger interparticle pores, reducing the tortuosity of lithium ion transport inside the electrode and avoiding the obstruction of ion transport inside the electrode under high load. At the same time, it provides a continuous channel for electrolyte to penetrate into the deeper layers of the electrode. The hollow pore size is 0.5-2 μm. The hollow cavity inside the positive electrode material can store a certain amount of electrolyte, increasing the overall electrolyte retention of the electrode. At the same time, it provides a buffer space for the volume change of the positive electrode material during charging and discharging, reducing the probability of material structure damage. The polyacrylic polymer is one or a mixture of two of polyacrylic acid emulsions or polyacrylate emulsions. During homogenization, the polyacrylic polymer can be uniformly dispersed in the slurry system. The carboxyl functional groups on its molecular chains can interact with the polar components in the electrolyte, reducing the contact angle between the electrolyte and the electrode surface, increasing the electrode's affinity for the electrolyte, and accelerating the electrolyte wetting rate. Simultaneously, the polyacrylic polymer can help enhance the slurry's adhesion properties, improve the bonding force between the inner positive electrode material and the aluminum foil current collector, and prevent the material from detaching from the current collector surface during charge-discharge cycles. When the two polymers are used in combination, the content of carboxyl functional groups and the adhesion strength of the slurry can be adjusted by changing the mixing ratio.

[0020] S12: The second slurry uses a dense structure cathode material with a smaller particle size.

[0021] In this embodiment, the second slurry is used to form an outer positive electrode layer covering the inner positive electrode layer, creating a functionally complementary gradient structure with the inner positive electrode layer to jointly improve the electrochemical performance of the high-load electrode. The preparation process of the second slurry is consistent with the conventional positive electrode slurry preparation process. The positive electrode material, conductive agent, and binder are mixed according to a set ratio, and an organic solvent is added and stirred until a uniform and stable slurry system is formed, without the need for additional polyacrylic acid polymers. The dense structure of the positive electrode material in the second slurry has a particle size D50 range of 4-6 μm, which can increase the content of active material per unit thickness and improve the areal capacity of the electrode sheet while maintaining good wettability of the electrode sheet. The positive electrode material is one or a mixture of two of the following: ternary materials or lithium-rich manganese-based materials. Maintaining consistency with the type of inner positive electrode material ensures the electrochemical potential matching and reaction rate synchronization between the inner and outer electrode materials, avoiding excessive local polarization caused by material differences. The gradient structure, composed of an inner layer of large-particle hollow material and an outer layer of small-particle dense material, can maintain a suitable pore structure and continuous ion transport channels even under high compaction conditions. This avoids the problem of ion transport obstruction caused by the decrease in overall porosity and the increase in the tortuosity of the ion transport path in traditional single-coated high-load electrodes. During charge-discharge cycles, the outer dense small-particle layer can work in synergy with the electrolyte storage and transport channels of the inner layer to ensure that there are always stable ion transport channels and sufficient electrolyte supply inside the electrode. This reduces irreversible reactions of active materials caused by electrolyte shortage or insufficient ion transport, improves the cycle stability of the battery, and enhances capacity retention.

[0022] S2: The first slurry is coated on the surface of the aluminum foil current collector, dried, and then the second slurry is coated on top of the first slurry layer to form a double-layer positive electrode layer.

[0023] In this embodiment, a functionally graded bilayer cathode structure is constructed through a step-by-step coating process, achieving functional complementarity between the inner and outer layers. This solves the problems of electrolyte wetting difficulties and ion transport obstruction inherent in traditional single-coating high-load electrodes. The aluminum foil current collector possesses excellent conductivity and mechanical strength, serving as a carrier for electron collection and transport while providing physical support for the bilayer cathode layer. After coating the first slurry onto the surface of the aluminum foil current collector, it undergoes drying. The drying process removes the organic solvents from the first slurry, allowing the binder to solidify and bond the inner cathode material particles together firmly to the surface of the aluminum foil current collector, forming an inner cathode layer with a stable porous structure. This process also prevents the inner slurry from dissolving or detaching during the subsequent coating of the second slurry, ensuring the interfacial bonding strength of the bilayer structure. The second slurry is then uniformly coated on top of the first slurry layer and dried to form the outer cathode layer. The two layers are tightly bonded together, constituting a complete bilayer cathode structure. The coating thickness of the first slurry is 40-70% smaller than that of the second slurry. This thickness ratio ensures that the inner layer has sufficient thickness to construct continuous electrolyte penetration channels and a liquid-retaining structure, while allowing the outer layer to occupy the majority of the electrode thickness. This fully leverages the high tap density of the small-particle-size, dense cathode material in the outer layer, thereby increasing the overall active material loading and areal capacity of the electrode. The relatively smaller inner layer thickness shortens the path length for electrolyte penetration from the outer layer to the inner layer and the current collector, further accelerating the electrolyte wetting rate and reducing the settling time after battery injection. The resulting cathode has an overall areal loading of 20-50 mg / cm², which meets the requirements of high-energy-density lithium-ion batteries. Combined with the dual-layer gradient structure design, it is possible to achieve a high loading while maintaining a suitable pore structure and ion transport capacity within the electrode, avoiding the problems of excessively low porosity and excessively long ion transport paths that occur in traditional single-coating processes under high loading conditions. The coating process uses a continuous coating method to control the thickness uniformity of each area of ​​the electrode, and the drying process uses a segmented heating method to control the solvent evaporation rate, so as to avoid defects such as surface cracking and particle agglomeration caused by rapid solvent evaporation, and ensure the structural integrity and electrochemical performance consistency of the double positive electrode layer.

[0024] The application of a high-load lithium-ion battery positive electrode sheet in lithium-ion batteries, whereby the lithium-ion battery positive electrode sheet is used as a positive electrode component in lithium-ion batteries.

[0025] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A method for preparing a high-load lithium-ion battery cathode, characterized in that: It includes the following steps: S1: Prepare two positive electrode slurries with different pore structure characteristics respectively; S11: The first slurry uses a hollow structure cathode material with a larger particle size, and polyacrylic acid polymers are added during the homogenization process; S12: The second slurry uses a dense structure cathode material with a smaller particle size; S2: The first slurry is coated on the surface of the aluminum foil current collector, dried, and then the second slurry is coated on top of the first slurry layer to form a double-layer positive electrode layer.

2. The method for preparing a high-load lithium-ion battery cathode sheet according to claim 1, characterized in that: In step S2, the coating thickness of the first slurry is 40-70% smaller than that of the second slurry.

3. The method for preparing a high-load lithium-ion battery cathode sheet according to claim 1, characterized in that: In step S11, the particle size D50 of the positive electrode material in the first slurry is in the range of 10-15 μm, and the hollow pore size is 0.5-2 μm.

4. The method for preparing a high-load lithium-ion battery cathode sheet according to claim 3, characterized in that: The polyacrylic polymer is one or a mixture of two of polyacrylic acid emulsions or polyacrylate emulsions.

5. The method for preparing a high-load lithium-ion battery positive electrode sheet according to claim 1, characterized in that: In step S12, the particle size D50 of the positive electrode material in the second slurry ranges from 4 to 6 μm.

6. A method for preparing a high-load lithium-ion battery cathode sheet according to claim 3 or 5, characterized in that: The cathode material is one or a mixture of two of the following: ternary materials or lithium-rich manganese-based materials.

7. The method for preparing a high-load lithium-ion battery cathode sheet according to claim 1, characterized in that: The overall surface loading of the prepared positive electrode sheet is 20-50 mg / cm².

8. The application of the high-load lithium-ion battery positive electrode sheet according to claim 1 in lithium-ion batteries, characterized in that, Lithium-ion battery cathode sheets are used as cathode components in lithium-ion batteries.

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