High-fluidity sodium ion battery negative electrode slurry and preparation method thereof

Abstract

The invention discloses high-fluidity sodium ion battery negative electrode slurry and a preparation method thereof. The preparation process of the negative electrode slurry comprises the following steps: adding a binder 1 and a solvent into a homogenizer, and carrying out two-stage homogenization treatment to obtain a glue solution 1; adding a binder 2 into the obtained glue solution 1, and fully mixing to obtain a glue solution 2; adding a conductive agent into the obtained glue solution 2, and fully mixing to obtain a conductive glue solution; and adding a negative electrode active material into the obtained conductive adhesive solution, sequentially carrying out two-stage homogenization treatment and viscosity adjustment, and then adding a binder 3 for homogenization to obtain the lithium ion battery negative electrode material. The negative electrode slurry prepared by the preparation method has excellent fluidity and viscosity retentivity, and the problems of poor fluidity, fast viscosity change, uneven coating surface and the like of the negative electrode slurry in the prior art are effectively solved.

Description

Technical Field

[0001] The invention relates to a battery negative electrode slurry, in particular to a high-fluidity sodium ion battery negative electrode slurry and a preparation method thereof, belonging to the technical field of sodium ion batteries. Background Art

[0002] The manufacturing process of sodium-ion batteries usually includes four steps: pulping, coating, assembly, and formation. Among them, the pulping industry, as the initial step in the preparation of sodium-ion batteries, plays a decisive role in subsequent industries and the final finished batteries. However, in the existing technology, the negative electrode materials of sodium-ion batteries still have problems such as high surface defects and large specific surface area, which will lead to poor slurry fluidity, rapid viscosity changes, and uneven coating surface, which will affect the performance of the finished battery and restrict its development and application.

[0003] A Chinese invention patent (CN118588937A) discloses a hard carbon negative electrode slurry, which is prepared from raw materials including the following components: negative electrode active material, carbon nanotubes, carbon black, binder and dispersant; the dispersant is sodium carboxymethyl cellulose, and its degree of substitution is 1.2 to 2.0. However, the above technical solution is to change the fluidity of the slurry by changing the dispersant. Although the fluidity of the slurry is improved to a certain extent, it still has the problem of rapid viscosity change. Summary of the invention

[0004] In view of the problems existing in the prior art, the first object of the present invention is to provide a high-fluidity negative electrode slurry for sodium ion batteries. Based on the synergistic effect between the components, the negative electrode slurry greatly improves the viscosity retention of the slurry while ensuring the fluidity of the slurry. In particular, three different binders are used, and the synergistic effect between the binders is utilized to greatly improve the stability and anti-precipitation ability of the negative electrode slurry, control the fluidity and viscoelasticity of the slurry, and thus improve the rheological properties of the negative electrode slurry.

[0005] The second object of the present invention is to provide a method for preparing a negative electrode slurry for a high-fluidity sodium ion battery. The method should be carried out strictly in accordance with the above process steps and requirements, adopt a segmented stirring process, and select a specific stirring speed for different binders according to their microscopic characteristics, thereby promoting the cross-linking coupling of the three binders, and effectively ensuring the uniform dispersion of the binders, avoiding the problem of binder degradation due to agglomeration.

[0006] In order to achieve the above technical objectives, the present invention provides a method for preparing a high-fluidity sodium ion battery negative electrode slurry, comprising:

[0007] Step S1, adding the binder 1 and the solvent into a homogenizer, and subjecting the mixture to a two-stage homogenization treatment to obtain a glue solution 1;

[0008] Step S2, adding binder 2 to the glue solution 1 obtained in step S1, and mixing thoroughly to obtain glue solution 2;

[0009] Step S3, adding a conductive agent to the glue solution 2 obtained in step S2, and mixing them thoroughly to obtain a conductive glue solution;

[0010] Step S4, adding the negative electrode active material to the conductive adhesive obtained in step S3, subjecting the conductive adhesive to two-stage homogenization and viscosity adjustment, and then adding the binder 3 for homogenization to obtain the conductive adhesive.

[0011] As a preferred solution, the binder 1 is CMC; the binder 2 is PAA and / or PAN; and the binder 3 is SBR.

[0012] The present invention improves the coating performance of the negative electrode slurry through the synergistic effect of the above three binders; among them, CMC, as a water-soluble polymer, can increase the viscosity of the solution and increase the stability of the suspension; PAA has thickening and stabilizing effects on the one hand, and can also be cross-linked with CMC to improve the anti-precipitation ability of the slurry on the other hand; the addition of SBR can not only improve the mechanical properties of the slurry in combination with CMC and PAA, but also adjust the fluidity and viscoelasticity of the slurry, thereby ensuring that the negative electrode slurry has good viscosity stability while having excellent fluidity.

[0013] As a preferred solution, the solvent is deionized water; and the conductive agent is at least one of SP, KS-6, CNT and VGCF.

[0014] As a preferred solution, the negative electrode active material is at least one of hard carbon, phosphorus carbon, soft carbon and silicon carbon.

[0015] As a preferred solution, the mass ratio of the binder 1, the binder 2 and the binder 3 is 5-7:8-14:20-27.

[0016] As a preferred solution, the solid content of the negative electrode slurry is 40-60%.

[0017] As a preferred solution, the mass ratio of the sum of the masses of the binder 1, the binder 2 and the binder 3, the negative electrode active material and the conductive agent is 3-5:1-3:90-95.

[0018] As a preferred solution, the two-stage homogenization process is: firstly low-speed stirring treatment and then high-speed stirring treatment.

[0019] As a preferred solution, the conditions for the low-speed stirring treatment are: a rotation speed of 10 to 25 rpm and a time of 10 to 20 min.

[0020] As a preferred solution, the conditions for the high-speed stirring treatment are: revolution of 20 to 50 rpm, rotation of 1500 to 5000 rpm, and time of 150 to 180 min.

[0021] As a preferred solution, the viscosity adjustment process is: adding solvent to adjust the slurry viscosity to 4300-4600CP.

[0022] As a preferred solution, the conditions for the homogenization treatment are: orbital speed of 15-25 rpm, rotation speed of 500-1200 rpm, and time of 20-40 min.

[0023] The stirring methods provided by the present invention must be carried out strictly in accordance with the above requirements. If any stirring method or condition is not within the required range of the present invention, it is impossible to obtain a negative electrode slurry with high fluidity and high viscosity retention. Among them, SBR presents micellar structure in microstructure, and high-speed stirring will destroy the micellar structure, causing demulsification, resulting in slurry agglomeration, and then the adhesion of the negative electrode slurry deteriorates; while CMC and PAA are shear-thinning non-Newtonian fluids. High-speed stirring can promote the dispersion of CMC and PAA to be more uniform, thereby ensuring the fluidity of the negative electrode slurry.

[0024] The present invention also provides a high-fluidity sodium ion battery negative electrode slurry obtained by any of the above-mentioned preparation methods.

[0025] Compared with the prior art, the beneficial technical effects of the technical solution of the present invention are:

[0026] 1) The negative electrode slurry provided by the present invention is based on the synergistic effect between the components. Under the premise of ensuring the fluidity of the slurry, the viscosity retention of the slurry is greatly improved. Among them, in particular, three different binders are used, and the synergistic effect between the binders is utilized to greatly improve the stability and anti-precipitation ability of the negative electrode slurry, control the fluidity and viscoelasticity of the slurry, thereby improving the rheological properties of the negative electrode slurry.

[0027] 2) The preparation method provided by the present invention must be strictly carried out in accordance with the above-mentioned process steps and requirements, and a segmented stirring process is adopted. For different binders, a specific stirring speed is selected according to their microscopic characteristics, thereby promoting the cross-linking coupling of the three binders while effectively ensuring the uniform dispersion of the binders and avoiding the problem of binder deterioration due to agglomeration. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a process flow chart of the negative electrode slurry preparation process provided by the present invention;

[0029] Figure 2 A diagram showing the coating state of the negative electrode slurry provided in Example 1 of the present invention;

[0030] Figure 3 This is a diagram showing the coating state of the negative electrode slurry provided in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments 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 creative work are within the scope of protection of the present invention.

[0032] Example 1

[0033] This embodiment provides a high-fluidity sodium ion battery negative electrode slurry, including the following components in parts by weight: 94 parts of hard carbon, 2 parts of SP, 0.7 parts of CMC, 1.0 parts of PAA, and 2.3 parts of SBR.

[0034] The preparation process of the negative electrode slurry is as follows: CMC and deionized water are added to a homogenizer, and under vacuum conditions, they are first stirred at a low speed of 10 to 25 rpm for 10 to 20 minutes, and then stirred at a revolution of 20 to 50 rpm and a rotation of 1500 to 5000 rpm for 150 to 180 minutes to obtain glue solution 1; after mixing glue solution 1 and PAA, they are stirred at a revolution of 20 to 50 rpm and a rotation of 1500 to 5000 rpm for 30 to 90 minutes under vacuum conditions to obtain glue solution 2; after mixing glue solution 2 and SP, they are first stirred at a speed of 10 to 25 rpm, Stir at low speed for 10-20min, then stir at an orbital speed of 20-50rpm and an autorotation speed of 1500-5000rpm for 150-180min to obtain a conductive adhesive solution; mix the conductive adhesive solution and hard carbon, first stir at a low speed of 10-25rpm for 10-20min, then stir at an orbital speed of 20-50rpm and an autorotation speed of 1500-5000rpm for 150-180min, then add a solvent to adjust the viscosity, and finally add SBR, stir at an orbital speed of 15-25rpm and an autorotation speed of 500-1200rpm for 30min to obtain the conductive adhesive solution.

[0035] Example 2

[0036] The process of this embodiment is completely consistent with that of embodiment 1, except that the negative electrode slurry includes the following components in parts by mass: 94 parts of hard carbon, 2 parts of CNT, 0.7 parts of CMC, 1.3 parts of PAN, and 2.0 parts of SBR.

[0037] Example 3

[0038] The process of this embodiment is completely consistent with that of embodiment 1, except that the negative electrode slurry includes the following components in mass parts: 94 parts of soft carbon, 2 parts of SP, 0.6 parts of CMC, 0.8 parts of PAA, and 2.6 parts of SBR.

[0039] Comparative Example 1

[0040] The process of this comparative example is completely consistent with that of Example 1, except that the negative electrode slurry comprises the following components in parts by mass: 94 parts of hard carbon, 2 parts of SP, 1.5 parts of CMC, and 2.5 parts of SBR.

[0041] Comparative Example 2

[0042] The process of this comparative example is completely consistent with that of Example 1, except that: the negative electrode slurry comprises the following components in parts by mass: 94 parts of hard carbon, 2 parts of SP, 1.0 parts of CMC, and 3 parts of SBR.

[0043] In order to more intuitively illustrate the beneficial technical effects of the technical solution of the present invention, we also conducted a series of tests on the performance of the slurry for the above embodiments and comparative examples. The test results are shown in Table 1.

[0044] Table 1

[0045]

[0046] It can be seen from Table 1 that the various performance indexes of the negative electrode slurries provided by Examples 1 to 3 of the present invention are significantly better than those of the negative electrode slurries obtained in Comparative Examples 1 and 2, especially the viscosity retention rate of the slurry. After testing, the 24h viscosity is only increased by 0.2% compared with the initial viscosity, which is almost unchanged, while the 24h viscosity in the comparative example is increased by 45% compared with the initial viscosity. In addition, the sedimentation rate of the slurry obtained in the embodiment of the present invention is approximately equal to 1%, while the sedimentation rate of the slurry obtained in the comparative example is ≥1.2%. Therefore, when the slurry obtained in the embodiment of the present invention is used for coating, the obtained wet film has the advantages of being smooth and having good leveling properties, which effectively solves the problems of poor slurry fluidity, rapid viscosity change, and uneven coating surface in the prior art.

Claims

1. A method for preparing a high-fluidity sodium ion battery negative electrode slurry, characterized in that: include: Step S1, adding the binder 1 and the solvent into a homogenizer, and subjecting the mixture to a two-stage homogenization treatment to obtain a glue solution 1; Step S2, adding binder 2 to the glue solution 1 obtained in step S1, and mixing thoroughly to obtain glue solution 2; Step S3, adding a conductive agent to the glue solution 2 obtained in step S2, and mixing them thoroughly to obtain a conductive glue solution; Step S4, adding the negative electrode active material to the conductive adhesive obtained in step S3, subjecting the conductive adhesive to two-stage homogenization and viscosity adjustment, and then adding the binder 3 for homogenization to obtain the conductive adhesive.

2. The method for preparing a high-fluidity sodium ion battery negative electrode slurry according to claim 1, characterized in that: The binder 1 is CMC; the binder 2 is PAA and / or PAN; and the binder 3 is SBR.

3. The method for preparing a high-fluidity sodium ion battery negative electrode slurry according to claim 1, characterized in that: The solvent is deionized water; the conductive agent is at least one of SP, KS-6, CNT and VGCF; the negative electrode active material is at least one of hard carbon, phosphorus carbon, soft carbon and silicon carbon.

4. The method for preparing a high-fluidity sodium ion battery negative electrode slurry according to claim 1, characterized in that: The mass ratio of the binder 1, the binder 2 and the binder 3 is 5-7:8-14:20-27; and the solid content of the negative electrode slurry is 40-60%.

5. The method for preparing a high-fluidity sodium ion battery negative electrode slurry according to claim 1, characterized in that: The mass ratio of the sum of the masses of the binder 1, the binder 2 and the binder 3, the negative electrode active material and the conductive agent is 3-5:1-3:90-95.

6. The method for preparing a high-fluidity sodium ion battery negative electrode slurry according to claim 1, characterized in that: The process of the two-stage homogenization treatment is: firstly perform a low-speed stirring treatment, and then perform a high-speed stirring treatment.

7. The method for preparing a high-fluidity sodium ion battery negative electrode slurry according to claim 6, characterized in that: The conditions for the low-speed stirring treatment are: a rotation speed of 10 to 25 rpm and a time of 10 to 20 min; the conditions for the high-speed stirring treatment are: a revolution of 20 to 50 rpm, a rotation of 1500 to 5000 rpm and a time of 150 to 180 min.

8. The method for preparing a high-fluidity sodium ion battery negative electrode slurry according to claim 1, characterized in that: The viscosity adjustment process is: adding solvent to adjust the slurry viscosity to 4300-4600CP; the homogenization treatment conditions are: revolution of 15-25rpm, rotation of 500-1200rpm, and time of 20-40min.

9. A high-fluidity sodium ion battery negative electrode slurry, characterized in that: Obtained by the preparation method according to any one of claims 1 to 8.

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