Sodium-ion battery positive electrode slurry and anti-gel preparation method and application thereof

Abstract

The invention provides sodium ion battery positive electrode slurry and an anti-gel preparation method thereof.The preparation method comprises the following steps that S1, a conductive agent, a dispersing agent and deionized water are mixed and subjected to ultrasonic treatment in an inert atmosphere, and pre-dispersion liquid is formed; s2, adding a positive active material into the pre-dispersion liquid in batches, and alternately stirring at a low speed and a high speed; s3, dissolving a binder in deionized water, injecting the binder into the mixed system at a rate of 0.3-1 mL / min, and synchronously starting vacuum defoaming; and S4, filtering the material liquid obtained in the step S3, standing and curing, and controlling the viscosity to be 2500-3500 mPa.s. The invention also provides a sodium ion battery positive pole piece which is prepared by coating, drying and rolling the slurry. The positive electrode slurry prepared by the method can effectively solve the problem of compatibility between a high pH value sensitive material and a water-based binder, improves the stability of the slurry and the performance of a battery, and has the advantages of low cost, environmental protection and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion batteries, and in particular to a sodium ion battery positive electrode slurry and an anti-gel preparation method and application thereof. Background Art

[0002] Sodium-ion battery cathode slurry typically consists of an active material, a conductive agent, a binder, and a solvent. However, due to the strong surface alkalinity of active materials (such as Prussian blue and layered oxides, which are highly pH-sensitive materials), they easily react with aqueous binders to form a gel, causing a sharp increase in slurry viscosity and deterioration in dispersion, which in turn affects coating uniformity and battery performance.

[0003] In this regard, in the prior art, the gel reaction is usually alleviated by adding a pH regulator (such as citric acid) or replacing a non-aqueous solvent (such as NMP). However, there are the following problems: (1) pH regulator residues will reduce the cycle stability of the battery; (2) non-aqueous solvents are expensive and pollute the environment; (3) because traditional dispersion processes (such as single high-speed stirring) are still used, local agglomeration cannot be completely eliminated (the gel material forms a jelly-like state).

[0004] Therefore, it is urgent to develop a new anti-gel preparation method for sodium ion battery positive electrode slurry. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a sodium ion battery positive electrode slurry and its anti-gel preparation method and application. The positive electrode slurry prepared by this preparation method can effectively solve the compatibility problem between high pH sensitive materials and aqueous binders, improve the slurry stability and battery performance, and at the same time have the advantages of low cost and environmental protection.

[0006] The present invention adopts the following technical solutions to solve the above technical problems:

[0007] A method for preparing an anti-gelling sodium ion battery positive electrode slurry comprises the following steps:

[0008] S1. Pre-dispersion treatment: mixing the conductive agent, dispersant and deionized water, and performing ultrasonic treatment under an inert atmosphere to form a pre-dispersion liquid;

[0009] S2, gradient mixing: adding the positive electrode active material to the pre-dispersion solution in batches, using alternating low-speed and high-speed stirring;

[0010] S3. Sustained-release addition of binder: dissolve the binder in deionized water and inject it into the mixed system of step S2 at a rate of 0.3-1 mL / min, and simultaneously start vacuum degassing;

[0011] S4, post-processing: After filtering the liquid after step S3, let it stand for aging and control the viscosity to be 2500-3500 mPa·s.

[0012] As one of the preferred embodiments of the present invention, in step S1, the ultrasonic power is 280 to 320 W, and the ultrasonic time is 8 to 12 minutes.

[0013] As one of the preferred embodiments of the present invention, in step S2, the positive electrode active material is added to the pre-dispersion liquid in 3 to 5 batches, with an interval of 1 to 3 minutes between each batch.

[0014] As one of the preferred embodiments of the present invention, in step S2, a planetary mixer is used to perform low-speed-high-speed alternating stirring at an orbital speed of 600-1000 rpm and a rotational speed of 1800-2200 rpm.

[0015] As one of the preferred embodiments of the present invention, in step S3, after the binder is dissolved in deionized water, it is injected into the mixed system at a rate of 0.3 to 1 mL / min through a peristaltic pump, and vacuum degassing is simultaneously started, with a vacuum degree of -0.08 MPa.

[0016] As one of the preferred embodiments of the present invention, in step S4, the liquid feed is filtered through a sieve and then left to mature for 1 to 3 hours to control the final viscosity to be 2500 to 3500 mPa·s.

[0017] As one of the preferred embodiments of the present invention, the conductive agent is a Ketjen black / carbon nanotube compound system with a compounding mass ratio of (2-5): 1; the dispersant is a polyetheramine surfactant with a molecular weight of 500-2000; the positive electrode active material is Prussian blue NaFeFe(CN)6, layered oxide NaNi 0.3 Mn 0.5 Co 0.2 O2; the binder is a sodium carboxymethyl cellulose / styrene-butadiene rubber composite system, with a composite mass ratio of 1: (1 to 3).

[0018] A sodium ion battery positive electrode slurry is prepared by the above method.

[0019] As one of the preferred embodiments of the present invention, the positive electrode slurry includes the following raw materials in parts by weight: 1.5 to 3 parts of a conductive agent, 0.2 to 0.5 parts of a dispersant, 92 to 96 parts of a positive electrode active material, 2 to 4 parts of a binder, and 5 to 15 parts of deionized water.

[0020] A sodium ion battery positive electrode sheet is made by coating, drying and rolling the above-mentioned sodium ion battery positive electrode slurry.

[0021] The advantages of the present invention over the prior art are:

[0022] The present invention improves the positive electrode slurry preparation method through three aspects: multi-stage dispersion process, binder sustained-release technology and dispersant design.

[0023] Among them, the multi-stage dispersion process: through "ultrasonic pretreatment + gradient feeding + alternating stirring", the local reaction between the active substance and the binder is suppressed;

[0024] Binder sustained-release technology: avoids sudden changes in system pH caused by one-time addition and reduces the risk of gelation;

[0025] Dispersant design: Polyetheramine dispersants form hydrogen bonds with the surface hydroxyl groups of active substances and reduce the surface tension of the slurry.

[0026] Based on this, the method of the present invention can effectively solve the compatibility problem between high pH sensitive materials and aqueous binders, improve slurry stability and battery performance, and has the advantages of low cost and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a 12h state diagram of the slurry of Example 1 of the present invention (results under a microscope, scale 1000μm);

[0028] Figure 2 This is a graph showing the 2h gel curing phenomenon of the slurry of Comparative Example 1 (results under a microscope, scale 1000 μm);

[0029] Figure 3 1 is the performance test result of the battery corresponding to the slurry of Example 1 of the present invention (in the figure, the horizontal axis is the number of cycles, and the vertical axis is the capacity retention rate);

[0030] Figure 4 These are the performance test results of the battery corresponding to the slurry of Comparative Example 2 (in the figure, the horizontal axis is the number of cycles, and the vertical axis is the capacity retention rate). DETAILED DESCRIPTION

[0031] The following examples of the present invention are described in detail. These examples are implemented based on the technical solutions of the present invention, and detailed implementation methods and specific operating procedures are given. However, the scope of protection of the present invention is not limited to the following examples. The raw materials and reagents involved in the following examples and test examples, unless otherwise specified, are all conventional commercially available raw materials and reagents in the field; the equipment and methods used, unless otherwise specified, are all conventional equipment and methods in the field and are not described in detail.

[0032] Example 1

[0033] A sodium ion battery positive electrode slurry of this embodiment includes the following raw materials in parts by weight: 2 parts of a conductive agent, 0.3 parts of a dispersant, 93 parts of a positive electrode active material, 2.7 parts of a binder, and 6 parts of deionized water.

[0034] Among them, the conductive agent is a Ketjen black / carbon nanotube compound system, which is made of Ketjen black (Japanese Ketjen black EC-600JD) and carbon nanotubes (Foxconn, Zhengzhou) were mixed in a mass ratio of 3:1.

[0035] The dispersant is a polyetheramine surfactant (Akeli Technology MS-2203ED) with a molecular weight of 500 to 2000.

[0036] The positive electrode active material was Prussian blue NaFeFe(CN)6 (Zhejiang Longsheng).

[0037] The binder is a CMC / SBR composite system, which is obtained by mixing CMC (Xinxiang Jinbang Power Technology Co., Ltd.) and SBR (Xinxiang Jinbang Power Technology Co., Ltd.) in a mass ratio of 1:2.

[0038] The preparation method is as follows:

[0039] S1. Pre-dispersion treatment: The conductive agent, dispersant and part of deionized water were mixed, and ultrasonic treatment was performed under an inert atmosphere with an ultrasonic power of 300 W and an ultrasonic time of 10 min to form a pre-dispersion liquid.

[0040] S2. Gradient mixing: The positive electrode active material was added to the pre-dispersion liquid in 3 batches, with an interval of 2 minutes between each batch, and a planetary mixer was used to perform low-speed-high-speed alternating stirring at a revolution speed of 800 rpm and a rotation speed of 2000 rpm.

[0041] S3. Sustained-release addition of binder: dissolve the binder in the remaining deionized water and inject it into the mixed system of step S2 at a rate of 0.5 mL / min through a peristaltic pump. Simultaneously start vacuum degassing with a vacuum degree of -0.08 MPa.

[0042] S4, post-treatment: the liquid after step S3 was filtered through a 200-mesh sieve, and allowed to stand for 2 hours to control the viscosity at about 3000 mPa·s (Brookfield viscometer, rotor LV3, speed 60 rpm).

[0043] Example 2

[0044] The positive electrode slurry of a sodium ion battery in this embodiment is basically the same as that in Example 1, except that the positive electrode active material is a layered oxide NaNi 0.3 Mn 0.5 Co 0.2 O2 (Zhongke Hainao).

[0045] Example 3

[0046] A positive electrode slurry for a sodium ion battery of this embodiment includes the following raw materials in parts by weight: 1.5 parts of a conductive agent, 0.2 parts of a dispersant, 92 parts of a positive electrode active material, 2 parts of a binder, and 15 parts of deionized water.

[0047] Among them, the conductive agent is a Ketjen black / carbon nanotube compound system, which is made of Ketjen black (Japanese Ketjen black EC-600JD) and carbon nanotubes (Foxconn, Zhengzhou) were mixed in a mass ratio of 2:1.

[0048] The dispersant is a polyetheramine surfactant (Akeli Technology MS-2203ED) with a molecular weight of 500 to 2000.

[0049] The positive electrode active material was Prussian blue NaFeFe(CN)6 (Zhejiang Longsheng).

[0050] The binder is a CMC / SBR composite system, which is obtained by mixing CMC (Xinxiang Jinbang Power Technology Co., Ltd.) and SBR (Xinxiang Jinbang Power Technology Co., Ltd.) in a mass ratio of 1:1.

[0051] The preparation method is as follows:

[0052] S1. Pre-dispersion treatment: The conductive agent, dispersant and part of deionized water were mixed, and ultrasonic treatment was performed under an inert atmosphere with an ultrasonic power of 280 W and an ultrasonic time of 12 min to form a pre-dispersion liquid.

[0053] S2. Gradient mixing: The positive electrode active material was added to the pre-dispersion liquid in 4 batches, with an interval of 1 minute between each batch, and a planetary mixer was used to perform low-speed-high-speed alternating stirring at an orbital speed of 600 rpm and a rotation speed of 1800 rpm.

[0054] S3. Sustained-release addition of binder: dissolve the binder in the remaining deionized water and inject it into the mixed system of step S2 at a rate of 0.3 mL / min through a peristaltic pump. Simultaneously start vacuum degassing with a vacuum degree of -0.08 MPa.

[0055] S4, post-treatment: the liquid after step S3 was filtered through a 200-mesh sieve, and allowed to stand for 1 hour to control the viscosity at about 2500 mPa·s (Brookfield viscometer, rotor LV3, speed 60 rpm).

[0056] Example 4

[0057] A positive electrode slurry for a sodium ion battery of this embodiment includes the following raw materials in parts by weight: 3 parts of a conductive agent, 0.5 parts of a dispersant, 96 parts of a positive electrode active material, 4 parts of a binder, and 5 parts of deionized water.

[0058] Among them, the conductive agent is a Ketjen black / carbon nanotube compound system, which is made of Ketjen black (Japanese Ketjen black EC-600JD) and carbon nanotubes (Foxconn, Zhengzhou) were mixed in a mass ratio of 5:1.

[0059] The dispersant is a polyetheramine surfactant (Akeli Technology MS-2203ED) with a molecular weight of 500 to 2000.

[0060] The positive electrode active material was Prussian blue NaFeFe(CN)6 (Zhejiang Longsheng).

[0061] The binder is a CMC / SBR composite system, which is obtained by mixing CMC (Xinxiang Jinbang Power Technology Co., Ltd.) and SBR (Xinxiang Jinbang Power Technology Co., Ltd.) in a mass ratio of 1:3.

[0062] The preparation method is as follows:

[0063] S1. Pre-dispersion treatment: The conductive agent, dispersant and part of deionized water were mixed, and ultrasonic treatment was performed under an inert atmosphere with an ultrasonic power of 320 W and an ultrasonic time of 8 minutes to form a pre-dispersion liquid.

[0064] S2. Gradient mixing: The positive electrode active material was added to the pre-dispersion liquid in 5 batches, with an interval of 3 minutes between each batch, and a planetary mixer was used to perform low-speed-high-speed alternating stirring at a revolution speed of 1000 rpm and a rotation speed of 2200 rpm.

[0065] S3. Sustained-release addition of binder: dissolve the binder in the remaining deionized water and inject it into the mixed system of step S2 at a rate of 1 mL / min through a peristaltic pump. Simultaneously start vacuum degassing with a vacuum degree of -0.08 MPa.

[0066] S4, post-processing: the liquid after step S3 was filtered through a 200-mesh sieve, and allowed to stand for 3 hours to control the viscosity at about 3500 mPa·s (Brookfield viscometer, rotor LV3, speed 60 rpm).

[0067] Comparative Example 1

[0068] The sodium ion battery positive electrode slurry of this comparative example is basically the same as that of Example 1, with the main difference being that the gradient mixing and slow-release addition process are not used in the preparation of the slurry.

[0069] Comparative Example 2

[0070] The sodium ion battery positive electrode slurry of this comparative example is basically the same as that of Example 2, with the main difference being that the gradient mixing and slow-release addition process are not used in the preparation of the slurry.

[0071] Test Example 1

[0072] This test example is used to verify the stability of the sodium ion battery positive electrode slurry of the present invention and the performance of the assembled battery.

[0073] Test method: Prepare the corresponding slurry according to the methods of Examples 1 to 4 above, and observe the stability of the slurry within 12 hours; at the same time, take part of the slurry and coat, dry, and roll-press it to prepare the corresponding sodium ion battery positive electrode, and perform performance testing on the assembled battery.

[0074] Test results: as shown in Table 1 and Table 2.

[0075] Table 1 Stability results of slurries of Examples 1 to 4

[0076]

[0077]

[0078] Table 2 Performance test results of assembled batteries corresponding to slurries of Examples 1 to 4

[0079] slurry 1C cycle 500 times capacity retention Example 1 88％ Example 2 91％ Example 3 86％ Example 4 87％

[0080] The above results show that the sodium ion battery positive electrode slurry prepared by the methods of each embodiment of the present invention has excellent stability and assembled battery performance.

[0081] Test Example 2

[0082] This test case is used to verify the effect of “gradient mixing and slow-release addition process” on slurry stability.

[0083] Test method: Prepare corresponding slurries according to the methods of the present invention (taking Example 1 as an example) and the comparative example (taking Comparative Example 1 as an example), and observe the slurry stability within 12 hours.

[0084] Test results: The slurry of the present invention is stable within 12 hours without any coagulation or sedimentation ( Figure 1 ); while the comparative slurry solidified into gel within 2 hours ( Figure 2 ).

[0085] The above results show that the "gradient mixing and slow-release addition process" has a great influence on the stability of the slurry of the present invention. The slurry prepared by the method of the present invention can effectively improve the stability of the slurry.

[0086] Test Example 3

[0087] This test case is used to verify the impact of the “gradient mixing and sustained-release addition process” on the performance of assembled batteries.

[0088] Test method: The corresponding slurries were prepared according to the methods of the present invention (Example 2) and the comparative example (Comparative Example 2), and then the corresponding slurries were coated, dried, and rolled to prepare the positive electrode of the sodium ion battery. Finally, the performance of the assembled battery was tested.

[0089] Test results: After the slurry of the present invention is applied, the electrode sheet has no cracks, the surface density deviation is ≤±2.5%, and the corresponding battery has a capacity retention rate of 91% after 500 cycles at 1C ( Figure 3 ), while the battery corresponding to the control ratio is 82% ( Figure 4 ).

[0090] The above results show that the "gradient mixing and slow-release addition process" has a great influence on the performance of the final assembled battery. The use of the method of the present invention to prepare the slurry can effectively improve the battery performance.

[0091] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing an anti-gelling sodium ion battery positive electrode slurry, characterized in that: The steps include: S1. Pre-dispersion treatment: mixing the conductive agent, dispersant and deionized water, and performing ultrasonic treatment under an inert atmosphere to form a pre-dispersion liquid; S2, gradient mixing: adding the positive electrode active material to the pre-dispersion solution in batches, using alternating low-speed and high-speed stirring; S3. Sustained-release addition of binder: dissolve the binder in deionized water and inject it into the mixed system of step S2 at a rate of 0.3-1 mL / min, and simultaneously start vacuum degassing; S4, post-processing: After filtering the liquid after step S3, let it stand for aging and control the viscosity to be 2500-3500 mPa·s.

2. The anti-gel preparation method for sodium ion battery positive electrode slurry according to claim 1, characterized in that: In step S1, the ultrasonic power is 280-320 W, and the ultrasonic time is 8-12 minutes.

3. The anti-gel preparation method for sodium ion battery positive electrode slurry according to claim 1, characterized in that: In step S2, the positive electrode active material is added to the pre-dispersion liquid in 3 to 5 batches, with an interval of 1 to 3 minutes between each batch.

4. The anti-gel preparation method for sodium ion battery positive electrode slurry according to claim 1, characterized in that: In the step S2, a planetary mixer is used to perform low-speed-high-speed alternating stirring at a revolution speed of 600-1000 rpm and a rotation speed of 1800-2200 rpm.

5. The anti-gel preparation method of sodium ion battery positive electrode slurry according to claim 1, characterized in that: In step S3, after the binder is dissolved in deionized water, it is injected into the mixed system at a rate of 0.3 to 1 mL / min through a peristaltic pump, and vacuum degassing is simultaneously started, with a vacuum degree of -0.08 MPa.

6. The anti-gel preparation method for sodium ion battery positive electrode slurry according to claim 1, characterized in that: In the step S4, the liquid is filtered through a mesh and then left to mature for 1 to 3 hours to control the final viscosity to be 2500 to 3500 mPa·s.

7. The method for preparing an anti-gelling sodium ion battery positive electrode slurry according to any one of claims 1 to 6, characterized in that: The conductive agent is a Ketjen black / carbon nanotube compound system with a compounding mass ratio of (2-5):1; the dispersant is a polyetheramine surfactant with a molecular weight of 500-2000; the positive electrode active material is Prussian blue NaFeFe(CN)6, layered oxide NaNi 0.3 Mn 0.5 Co 0.2 O2; the binder is a sodium carboxymethyl cellulose / styrene-butadiene rubber composite system, with a composite mass ratio of 1: (1 to 3).

8. A sodium ion battery positive electrode slurry, characterized in that: The method is prepared by any one of claims 1 to 7.

9. The sodium ion battery positive electrode slurry according to claim 8, characterized in that The positive electrode slurry includes the following raw materials in parts by weight: 1.5 to 3 parts of a conductive agent, 0.2 to 0.5 parts of a dispersant, 92 to 96 parts of a positive electrode active material, 2 to 4 parts of a binder, and 5 to 15 parts of deionized water.

10. A sodium ion battery positive electrode plate, characterized in that: The sodium ion battery positive electrode slurry according to claim 8 or 9 is coated, dried and rolled.

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