Negative electrode coating of lithium ion battery and preparation method of negative electrode coating

Abstract

The present invention relates to the technical field of lithium ion batteries, and discloses a lithium ion battery negative electrode coating and a preparation method thereof, the lithium ion battery negative electrode coating comprises the following components: 35-45 wt% of inorganic ceramic particles, 5-10 wt% of an acrylate solution (the solid content is 25%), 1-3 wt% of calcium hydroxide powder, 1-3 wt% of carboxymethyl cellulose (CMC), and 45-55 wt% of deionized water. The preparation method comprises the following steps: (1) respectively preparing a proper amount of a water-based glue solution and a dispersant solution in advance; (2) adding weighed inorganic ceramic particles into deionized water, dispersing at a high speed, adding a water-based adhesive solution and a dispersing agent solution, and stirring until the materials are uniformly mixed to form ceramic slurry; and (3) coating the ceramic slurry on the surface of the negative active material by using coating equipment, and then drying. According to the invention, the internal short circuit rate of the high-energy-density lithium ion battery can be obviously reduced, and the safety is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a negative electrode coating of a lithium ion battery and a preparation method thereof. Background Art

[0002] As a new green and environmentally friendly energy source, lithium-ion batteries offer advantages such as small size, light weight, high energy density, long service life, and environmental friendliness. They are widely used in digital products, electric vehicles, large-scale power supplies, and energy storage systems. However, the requirements for lithium-ion battery life, cost, safety, and energy density are becoming increasingly stringent. Currently, lithium-ion batteries are developing towards longer life, higher energy density, higher safety, and lower cost.

[0003] As battery cell energy density continues to increase, lithium-ion battery safety issues are becoming increasingly severe. Known safety incidents include battery fires and explosions in electronic products, electric vehicles, and other applications. Currently, coating battery electrodes or separators with inorganic ceramics is a key research area for lithium-ion batteries. Inorganic ceramic materials offer advantages such as high melting points, excellent thermal stability, and excellent insulation properties. Furthermore, because hydroxyl groups are present on the surface of ceramic powders, they are highly absorbent. Ceramizing the electrode or separator surface significantly improves their lyophilicity and liquid retention. In recent years, ALD technology has been widely used for the preparation of ceramic coatings due to its excellent deposition uniformity and consistency, as well as its ability to precisely control thickness at the nanoscale. Experiments in lithium-ion batteries have demonstrated that ALD deposition of ceramic coatings on electrode surfaces can improve battery performance. However, due to the high cost of ALD equipment, immature technology, and poor compatibility with existing lithium-ion battery production processes, mass production has been difficult. Summary of the Invention

[0004] The purpose of the present invention is to provide a negative electrode coating for a lithium ion battery and a preparation method thereof, which can significantly reduce the internal short circuit rate of high energy density lithium ion batteries, improve safety, and improve the electrolyte wettability of the electrode, reduce polarization, and enhance battery cycle stability.

[0005] In order to achieve the above purpose, the present invention provides the following technical solutions: The ceramic coating components include: 35-45wt% inorganic ceramic particles, 5-10wt% acrylate solution (solid content 25%), 1-3wt% calcium hydroxide powder, 1-3wt% carboxymethyl cellulose (CMC), 45-55wt% deionized water.

[0006] And prepare it according to the following steps: S1: Prepare appropriate amounts of aqueous glue solution and dispersant solution in advance; S2: Add weighed inorganic ceramic particles to deionized water, disperse at high speed, then add aqueous glue solution and dispersant solution, stir until mixed evenly, to form ceramic slurry; S3: Using a coating device to coat the ceramic slurry on the surface of the negative electrode active material, and then drying it.

[0007] In the present invention, the inorganic ceramic particles are a mixture of one or more of boehmite and diaspore; the particle size of the inorganic ceramic particles ranges from 0.1 to 10 μm, preferably from 0.3 to 3 μm. Since boehmite or diaspore has a small particle size, reaching the nanometer level and having a narrow particle size distribution, it is easy to agglomerate during the redispersion process. Therefore, it needs to be dispersed at high speed before adding the binder to ensure uniform mixing with other powders. The ceramic slurry is applied to the negative electrode active material. The coating has a high porosity and will not affect the normal insertion and deinsertion of lithium ions, so it will not affect the electrical performance of the lithium-ion battery. In addition, the high-porosity ceramic coating can improve the liquid absorption and retention rate of the battery. As a further preferred method, the steps for preparing the ceramic coating are specifically as follows: Prepare water-based adhesive solution: add acrylate solution and calcium hydroxide powder to deionized water in proportion and stir for 20-24 hours to form a water-based adhesive solution; Prepare CMC solution: add carboxymethyl cellulose to deionized water in proportion and stir for 6-8 hours to form carboxymethyl cellulose solution, i.e. CMC solution; Add inorganic ceramic particles to deionized water in proportion, stir for 1-2 hours, then add aqueous glue solution, stir again for 2-4 hours, and finally add CMC solution and stir for 1-2 hours to form ceramic slurry; The evenly stirred ceramic slurry is evenly coated on the surface of the negative electrode active material. The ceramic slurry needs to completely cover the active material layer. The coated electrode is then placed in an oven for drying at a temperature of 80-120°C for 9-11 hours.

[0008] Compared with the existing technology, the beneficial effects of the present invention are: the method can match the existing lithium-ion battery production process and is suitable for mass production on the production line; it can also significantly reduce the internal short-circuit rate of high-energy-density lithium-ion batteries, improve safety, and improve the electrolyte wettability of the electrode, reduce polarization, and enhance battery cycle stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a flow chart of the preparation of an embodiment of a negative electrode coating for a lithium ion battery of the present invention; Figure 2 It is a performance test table of comparative examples and embodiments of the present invention. DETAILED DESCRIPTION

[0010] like Figure 1-Figure 2 As shown, the present invention will be further described below in conjunction with embodiments.

[0011] Example 1: Preparation of aqueous adhesive solution: Acrylate (solid content 25%), calcium hydroxide powder, and deionized water were mixed in a mass ratio of 83:1.4:15.6, and dispersed at high speed until uniformly mixed and set aside; Prepare CMC solution: mix carboxymethyl cellulose and deionized water in a mass ratio of 1.5:98.5, disperse and mix evenly at high speed for later use; Prepare ceramic slurry: weigh boehmite, aqueous glue solution, dispersant solution, and deionized water in a mass ratio of 38.5:8.5:1.4:51.6. Now add boehmite powder to deionized water and disperse it at high speed. After mixing evenly, add aqueous glue solution again and disperse it at high speed and mix evenly to form a ceramic slurry for later use; The prepared ceramic slurry is applied to the surface of the negative electrode active material using a coating machine. The ceramic coating completely covers the active material layer and is double-sided coated with a coating thickness of 2 μm on each side. The electrode is then placed in a vacuum oven and dried at 100°C for 10 hours.

[0012] Example 2: Preparation of aqueous adhesive solution: Acrylate (solid content 25%), calcium hydroxide powder, and deionized water were mixed in a mass ratio of 83:1.4:15.6, and dispersed at high speed until uniformly mixed and set aside; Prepare CMC solution: mix carboxymethyl cellulose and deionized water in a mass ratio of 1.5:98.5, disperse and mix evenly at high speed for later use; Prepare ceramic slurry: weigh boehmite, aqueous glue solution, dispersant solution, and deionized water in a mass ratio of 38.5:8.5:1.4:51.6. Now add boehmite powder to deionized water and disperse it at high speed. After mixing evenly, add aqueous glue solution again and disperse it at high speed and mix evenly to form a ceramic slurry for later use; The prepared ceramic slurry was applied to the surface of the negative electrode active material using a coating machine. The ceramic coating completely covered the active material layer and was double-sided coated with a coating thickness of 3.5 μm on each side. The electrode was then placed in a vacuum oven and dried at 105°C for 10.5 hours.

[0013] Example 3: Preparation of aqueous adhesive solution: Acrylate (solid content 25%), calcium hydroxide powder, and deionized water were mixed in a mass ratio of 83:1.4:15.6, and dispersed at high speed until uniformly mixed and set aside; Prepare CMC solution: mix carboxymethyl cellulose and deionized water in a mass ratio of 1.5:98.5, disperse and mix evenly at high speed for later use; Prepare ceramic slurry: boehmite, aqueous glue solution, dispersant solution, and deionized water in a mass ratio of 38.5:7.3:1.3:1.4:51.5. Weigh boehmite powder into deionized water and disperse it at high speed. After mixing evenly, add aqueous glue solution again and disperse it at high speed to form ceramic slurry for later use. The prepared ceramic slurry is applied to the surface of the negative electrode active material using a coating machine. The ceramic coating completely covers the active material layer and is double-sided coated with a coating thickness of 5 μm on each side. The electrode is then placed in a vacuum oven and dried at 110°C for 11 hours.

[0014] Comparative Example: No ceramic coating was applied to the electrode sheet coated with the negative electrode slurry, and the next process was directly carried out. The subsequent steps were the same as those in the embodiment. The performance of Example 1, Example 2, Example 3 and the comparative example are compared. The comparison results are as follows: Figure 2 .

[0015] from Figure 2 It can be seen from the figure that after coating the surface of the negative active material with ceramic, from the perspective of the battery's electrical performance, the battery's conductivity becomes worse and the DC internal resistance is higher; however, the battery's K value is significantly reduced and the battery's self-discharge rate is lower; from the perspective of the battery's safety performance, the battery coated with ceramic has significantly better safety performance than the battery without ceramic coating, especially the extrusion test has been greatly improved.

[0016] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural transformation made to the above embodiments based on the technical essence of the present invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A negative electrode coating for a lithium-ion battery, comprising the following components: 35-45 wt% inorganic ceramic particles, 5-10 wt% acrylate solution, 1-3 wt% calcium hydroxide powder, 1-3 wt% carboxymethyl cellulose (CMC), and 45-55 wt% deionized water.

2. The negative electrode coating of a lithium ion battery according to claim 1, wherein: The inorganic ceramic particles are a mixture of one or more of boehmite and diaspore.

3. The negative electrode coating of a lithium ion battery according to claim 2, wherein: The particle size of the inorganic ceramic particles is 0.1-10 μm.

4. The negative electrode coating of a lithium ion battery according to claim 3, wherein: The particle size of the inorganic ceramic particles is 0.3-3.0 μm.

5. The negative electrode coating of a lithium ion battery according to claim 1, wherein: The ceramic slurry is coated on one side or both sides of the negative electrode active material.

6. The negative electrode coating of a lithium ion battery according to claim 1, wherein: The ceramic slurry is coated on the surface of the negative electrode active material to a thickness of 0.1-10 μm.

7. A method for preparing a negative electrode coating of a lithium ion battery according to any one of claims 1 to 6, characterized in that The steps include: S1: Prepare water-based adhesive solution: add acrylate solution and calcium hydroxide powder in deionized water in proportion, and stir for 20-24 hours to form a water-based adhesive solution; S2: Prepare CMC solution: add carboxymethyl cellulose to deionized water in proportion and stir for 6-8 hours to form a carboxymethyl cellulose solution, i.e., CMC solution; S3: Add inorganic ceramic particles to deionized water in proportion, stir for 1-2 hours, then add aqueous glue solution, stir again for 2-4 hours, and finally add CMC solution and stir for 1-2 hours to form ceramic slurry; S4: The evenly stirred ceramic slurry is evenly coated on the surface of the negative electrode active material. The ceramic slurry needs to completely cover the active material layer. The coated electrode is then placed in an oven for drying. The oven temperature is 80-120°C and the drying time is 9-11 hours.

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