A method for optimizing stirring of negative electrode slurry

Abstract

The present invention discloses a method for optimizing the stirring of negative electrode slurry, wherein kneading and slurrying are performed by controlling the timing of adding CMC powder in the negative electrode slurrying process. It is necessary to ensure that the stretching of the CMC molecular chain in the negative electrode pole piece after baking has no significant effect on the thickness of the subsequent battery cell. At the same time, it is also necessary to improve the dispersion effect of the slurry, improve the adhesion of the pole piece, improve the consistency of the coating surface density, and ultimately improve the performance of the battery cell. Through the method of the present invention, the slurrying time is greatly shortened, the dispersion effect of the slurry is improved, the consistency of the coating surface density is improved, the adhesion of the pole piece is improved, and ultimately the consistency of the battery cell is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion batteries, relates to the preparation of negative electrode slurry, and in particular to an optimized stirring method for negative electrode slurry. Background Art

[0002] Currently, the industry's lithium-ion battery negative electrode slurrying methods include a semi-dry method that first prepares a CMC paste and then slurries, a wet method that prepares a conductive paste, and a dry method that directly adds CMC powder for slurrying. The slurries produced by the semi-dry and wet methods do not achieve ideal dispersion, and the slurrying time is long, increasing production costs. Dry slurrying, by directly adding CMC, utilizes the strong shear force of the stirring paddle and the inner wall of the mixing tank to fully mix the graphite and CMC, improving dispersion and slurry stability.

[0003] However, after using the dry method for pulping, the water-based glue or SBR will be wrapped on the CMC, resulting in the CMC not being completely dispersed. After the battery cell is baked, the CMC molecular chain will stretch, causing the battery cell to be too thick. Summary of the Invention

[0004] To address these issues, the present invention provides an optimized stirring method for negative electrode slurry. This method utilizes controlled timing for adding CMC powder during the negative electrode slurry preparation process to knead and form the slurry. This method ensures that the stretching of the CMC molecular chains in the negative electrode pole piece after baking has no significant impact on the thickness of the subsequent battery cell. Furthermore, it also aims to improve the slurry's dispersion, enhance the adhesion of the pole piece, and increase the consistency of the coating surface density, ultimately enhancing battery cell performance.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] An optimized stirring method for negative electrode slurry, the optimized stirring method comprising: adding graphite and a conductive agent into a container and stirring the mixture; adding 60% of the total amount of water-based glue for a first pre-kneading; scraping the mixture after the first pre-kneading and then adding CMC powder for a second pre-kneading; performing a normal kneading process after the second pre-kneading; adding the remaining water-based glue and deionized water for viscosity adjustment and dispersion after the kneading; adding an auxiliary reagent after the viscosity adjustment and dispersion to adjust the viscosity to 8000-15000 m·pas; and finally evacuating and maintaining the pressure to obtain a finished negative electrode slurry.

[0007] As a preferred embodiment of the present invention, the negative electrode slurry comprises, by weight, 250-260 parts of graphite, 1.1-1.5 parts of conductive agent, 1.1-1.5 parts of cmc, 70-73 parts of water-based glue, 6.5-6.8 parts of auxiliary reagents and 180-185 parts of deionized water.

[0008] As a preferred embodiment of the present invention, the auxiliary reagent is a mixture of EC and PBB, and the mass ratio of EC to PBB is 4.5-5:1.

[0009] As a preferred embodiment of the present invention, after adding graphite and the conductive agent, the stirring speed is 5-15 rpm, and the stirring time is 1-10 minutes.

[0010] As a preferred embodiment of the present invention, the first pre-kneading process is: first pre-kneading at a revolution speed of 5 rpm for 5 min, then pre-kneading at a revolution speed of 15 rpm for 5 min, and finally pre-kneading at a revolution speed of 25 rpm for 10 min.

[0011] As a preferred embodiment of the present invention, the second pre-kneading process is: first pre-kneading at a revolution speed of 5 rpm for 5 min, then pre-kneading at a revolution speed of 15 rpm for 5 min, and finally pre-kneading at a revolution speed of 25 rpm for 10 min.

[0012] As a preferred embodiment of the present invention, the normal kneading process is: pre-kneading for 120 minutes at a revolution speed of 25 rpm.

[0013] As a preferred embodiment of the present invention, the process of viscosity adjustment and dispersion is: after adding the remaining water-based glue, stirring at a rotation speed of 1200 rpm for 45 minutes, adding the remaining deionized water, and continuing to stir at a rotation speed of 1200 rpm for 45 minutes.

[0014] As a preferred embodiment of the present invention, after adding the auxiliary reagent, stirring is carried out at a rotation speed of 1200 rpm for 45 minutes.

[0015] As a preferred solution of the present invention, the conditions for vacuuming and pressure maintaining are: vacuuming ≤ -0.095 MPa, and pressure maintaining for 30 minutes.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1) In the negative electrode slurrying process, the present invention controls the timing of adding CMC powder to knead and slurry. This ensures that the stretching of the CMC molecular chains in the negative electrode sheet after baking does not significantly affect the thickness of the subsequent battery cell. This also improves the dispersion of the slurry, enhances the adhesion of the electrode sheet, and increases the consistency of the coating surface density, ultimately enhancing battery cell performance.

[0018] 2) Through the method of the present invention, the slurry preparation time is greatly shortened, the dispersion effect of the slurry is improved, the consistency of the coating surface density is improved (single-sided surface density CPK: increased from 1.19 to 1.21, double-sided surface density CPK: increased from 1.60 to 1.89), the adhesion of the electrode is improved (the average adhesion value increases from 0.23N to 0.29N), and ultimately the consistency of the battery cell is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the state after pre-kneading in Example 1.

[0020] Figure 2 It is a schematic diagram of the state after kneading of Example 1.

[0021] Figure 3 This is a schematic diagram of the state after kneading of Comparative Example 1. DETAILED DESCRIPTION

[0022] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0023] The conductive agent used in the present invention can be a conductive agent commonly used in existing lithium-ion battery negative electrode slurry, and the present invention is not limited thereto. SP is used in the embodiment, and the others such as CMC, water-based glue, EC, and PBB can be purchased from the market.

[0024] Example 1

[0025] This embodiment provides an optimized stirring method for negative electrode slurry, wherein all graphite and conductive agent are added and stirred slowly at a low speed, and then 60% of the total amount of water-based glue is added for pre-kneading. After the first pre-kneading, the material is scraped and CMC powder is added for a second pre-kneading. After the second pre-kneading, a normal kneading process is carried out. After a certain kneading solid content (60%-70%) and kneading time (greater than or equal to 90 minutes), the remaining water-based glue and deionized water are added to adjust the viscosity and disperse (linear speed: 15.7-25 m / s, dispersion time greater than or equal to 120 minutes), and relevant auxiliary reagents (a small amount) are added to adjust the viscosity to 8000-15000 m·pas, and finally a finished slurry is obtained.

[0026] The detailed process is shown in Table 1.

[0027] Table 1. Specific process of Example 1

[0028]

[0029] Comparative Example 1

[0030] The whole graphite, conductive agent, CMC powder, 75% water-based glue and part of deionized water are added for pre-kneading. After a certain kneading solid content (60%-70%) and kneading time (greater than or equal to 90 minutes), the material is scraped. Then, the remaining water-based glue and deionized water are added to adjust the viscosity and disperse (line speed: 15.7-25m / s, dispersion time greater than or equal to 120 minutes), and relevant auxiliary reagents (a small amount) are added to adjust the viscosity to 8000-15000m·pas, and finally the finished slurry is obtained.

[0031] The specific process is shown in Table 2.

[0032] Table 2. Specific process of comparative example 1

[0033]

[0034] Comparison of the slurry data between Comparative Example 1 and Example 1 (see Table 3) shows that the slurry dispersion effect is not ideal, the surface density consistency is not improved, the electrode adhesion is not improved, the manufactured battery cell rebounds after baking, and the battery cell is too thick.

[0035] Table 3 Slurry dispersion effect

[0036]

[0037]

[0038] See also Figure 1 , Figure 2 and Figure 3 Comparison between Example 1 and Comparative Example 1 shows that Example 1 ensures that the stretching of the CMC molecular chains in the negative electrode plate after baking has no significant impact on the thickness of the subsequent battery cell. It also improves the dispersion of the slurry, enhances the adhesion of the electrode plate, and increases the consistency of the coating surface density, ultimately improving battery cell performance.

[0039] It can be seen that the method of the present invention greatly shortens the pulping time, improves the dispersion effect of the slurry, improves the consistency of the coating surface density (single-sided surface density CPK: increased from 1.19 to 1.21, double-sided surface density CPK: increased from 1.60 to 1.89), improves the adhesion of the electrode (the average adhesion value increases from 0.23N to 0.29N), and ultimately improves the consistency of the battery cell.

[0040] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form or substance. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the method of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention. Any equivalent changes, modifications and evolutions made by technicians familiar with this profession without departing from the spirit and scope of the present invention by using the technical content disclosed above are all equivalent embodiments of the present invention; at the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for optimizing stirring of negative electrode slurry, characterized in that: The optimized stirring method is as follows: adding graphite and a conductive agent to a container and stirring, adding 60% of the total amount of water-based glue for the first pre-kneading, scraping the material after the first pre-kneading, and then adding CMC powder for the second pre-kneading, and performing a normal kneading process after the second pre-kneading, adding the remaining water-based glue and deionized water for viscosity adjustment and dispersion after the kneading, adding auxiliary agents to adjust the viscosity to 8000-15000 m·pas after the viscosity adjustment and dispersion, and finally vacuuming and maintaining the pressure to obtain a finished negative electrode slurry; the negative electrode slurry comprises, by weight, 250-260 parts of graphite, 1.1-1.5 parts of conductive agent, 1.1-1.5 parts of CMC, 70-73 parts of water-based glue, 6.5-6.8 parts of auxiliary agents and 180-185 parts of Deionized water; after adding graphite and conductive agent, the stirring speed is 5-15 rpm, and the stirring time is 1-10 minutes; the first pre-kneading process is: first pre-kneading at a revolution speed of 5 rpm for 5 minutes, then pre-kneading at a revolution speed of 15 rpm for 5 minutes, and finally pre-kneading at a revolution speed of 25 rpm for 10 minutes; the second pre-kneading process is: first pre-kneading at a revolution speed of 5 rpm for 5 minutes, then pre-kneading at a revolution speed of 15 rpm for 5 minutes, and finally pre-kneading at a revolution speed of 25 rpm for 10 minutes; the normal kneading process is: pre-kneading at a revolution speed of 25 rpm for 120 minutes; the vacuum and pressure holding conditions are: vacuum ≤-0.095 MPa, pressure holding for 30 minutes.

2. The method for optimizing stirring of negative electrode slurry according to claim 1, characterized in that: The auxiliary reagent is a mixture of EC and PBB, and the mass ratio of EC to PBB is 4.5-5:1.

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