Homogenizing method capable of improving sedimentation stability of negative electrode slurry

Abstract

The invention relates to the technical field of lithium ion battery testing, in particular to a homogenizing method capable of improving the sedimentation stability of negative electrode slurry, and the homogenizing method comprises the following steps: (1) uniformly stirring CMC (Carboxymethyl Cellulose) and deionized water to prepare a CMC glue solution; (2) adding a negative conductive agent into the CMC glue solution prepared in the step (1), and uniformly stirring to prepare a conductive glue solution; (3) uniformly stirring a negative electrode active material, deionized water and absolute ethyl alcohol to prepare slurry; (4) adding the CMC glue solution in the step (1) into the slurry in the step (3), and uniformly stirring to obtain slurry; and (5) adding SBR (Styrene Butadiene Rubber) into the slurry in the step (4), and uniformly stirring to prepare the negative electrode slurry. According to the homogenizing method provided by the invention, the stability of the negative electrode slurry is greatly improved, the homogenizing method is simple and convenient, the sedimentation phenomenon caused by agglomeration of the negative electrode slurry can be obviously delayed, and the storage time of the negative electrode slurry is prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of lithium ion battery testing, and in particular to a homogenization method capable of improving the sedimentation stability of negative electrode slurry. Background Art

[0002] Lithium battery negative electrode slurry is a key component in lithium battery manufacturing. Lithium-ion battery negative electrode slurry is composed of a variety of materials with different densities and particle sizes. It is a non-Newtonian fluid formed by a solid-liquid two-phase mixture and dispersion, and belongs to a suspension system. The performance of the negative electrode slurry has an important impact on the overall performance of the lithium battery. In addition to having good dispersibility, suitable viscosity and fluidity, high-quality negative electrode slurry must also ensure the sedimentation stability of the slurry, and be able to maintain the slurry performance unchanged during storage and processing. Unstable suspensions are prone to particle agglomeration in a static state and quickly stratify due to gravity. Therefore, the stability of the negative electrode slurry is crucial. Stability affects the consistency and reliability of the battery. A stable negative electrode The slurry can ensure that during the production process, the performance of each batch of batteries has small differences, thereby improving the overall consistency of the battery product and providing users with a stable and reliable user experience. Good and stable negative electrode slurry can reduce side reactions during the charging and discharging process, reduce the damage to the electrode structure and the loss of materials, thereby extending the cycle life of the battery. Unstable negative electrode slurry may cause local overheating, short circuit and other problems, increasing the risk of battery safety accidents. Unstable negative electrode slurry will affect the processing performance of the battery, while stable slurry is conducive to the smooth progress of processes such as coating, improving production efficiency and product quality. Stable negative electrode slurry helps to reduce scrap rate and waste of raw materials, and reduce production costs.

[0003] However, the current upper limit of storage time for negative electrode slurry is only about 12 hours. After more than 12 hours, stratification of the slurry can be clearly seen, resulting in poor slurry uniformity.

[0004] Based on this, a homogenization method is now provided that can improve the sedimentation stability of negative electrode slurry, which can eliminate the disadvantages of the existing device. Summary of the invention

[0005] In view of the above problems, a homogenization method capable of improving the sedimentation stability of negative electrode slurry is provided, which solves the problems of slurry stability and short storage time.

[0006] In order to solve the problems in the prior art, the present invention provides a homogenization method capable of improving the sedimentation stability of negative electrode slurry, comprising:

[0007] (1) Mix CMC and deionized water to obtain CMC glue solution;

[0008] (2) adding a negative electrode conductive agent to the CMC glue solution prepared in step (1), stirring evenly, to prepare a conductive glue solution;

[0009] (3) stirring the negative electrode active material, deionized water and anhydrous ethanol to obtain a slurry;

[0010] (4) adding the CMC glue in step 1 to the slurry in step 3 and stirring evenly to obtain a slurry;

[0011] (5) SBR is added to the slurry in step (4) and stirred evenly to obtain a negative electrode slurry.

[0012] Preferably, the CMC in step (1) is sodium carboxymethyl cellulose.

[0013] Preferably, the mass ratios of the negative electrode active material, the negative electrode conductive agent, CMC and SBR are 95:1.5:1.5:2 respectively.

[0014] Preferably, in step (3), the deionized water is a solvent, the anhydrous ethanol is a dispersant, the negative electrode active material is artificial graphite or natural graphite, and the negative electrode active material, deionized water and anhydrous ethanol are homogenized to prepare a negative electrode slurry with a solid content of 45%.

[0015] Preferably, the negative electrode conductive agent in step (2) is conductive carbon black, carbon nanotubes or Ketjen black.

[0016] Preferably, the SBR in step (5) is styrene-butadiene rubber, and the solid content of the SBR is 45%.

[0017] Preferably, the mass ratio of the dispersant to the slurry is 3% to 5%.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The homogenization method provided by the present invention greatly improves the stability of the negative electrode slurry, and the homogenization method is simple and convenient, and can significantly delay the agglomeration and sedimentation of the negative electrode slurry, thereby extending the storage time of the negative electrode slurry.

[0020] 2. The dispersant added in the method provided by the present invention will completely evaporate with the electrode during the drying process and will not remain inside the electrode, thus having no adverse effect on the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The present invention is a comparative example 1 of a homogenization method capable of improving the sedimentation stability of negative electrode slurry, and a viscosity change diagram after different storage times.

[0022] Figure 2The present invention is a graph showing the viscosity change after different storage times of Comparative Example 2 of a homogenization method capable of improving the sedimentation stability of negative electrode slurry.

[0023] Figure 3 The present invention is a graph showing the viscosity change after different storage times of Comparative Example 3 of a homogenization method capable of improving the sedimentation stability of negative electrode slurry.

[0024] Figure 4 The present invention is a graph showing the viscosity change after different storage times in Example 1 of a homogenization method capable of improving the sedimentation stability of negative electrode slurry.

[0025] Figure 5 The present invention is a graph showing the viscosity change after different storage times of Example 2 of a homogenization method capable of improving the sedimentation stability of negative electrode slurry.

[0026] Figure 6 The present invention is a graph showing the viscosity change after different storage times of Example 3 of a homogenization method capable of improving the sedimentation stability of negative electrode slurry.

[0027] Figure 7 The figure is a slurry stability analysis result diagram of a homogenization method that can improve the sedimentation stability of negative electrode slurry. DETAILED DESCRIPTION

[0028] In order to further understand the features, technical means, specific objectives and functions of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0029] Example 1

[0030] This embodiment provides a homogenization method capable of improving the sedimentation stability of negative electrode slurry, and the homogenization method comprises the following steps:

[0031] 1. Take 0.15kg of CMC and 7kg of deionized water and stir at 1000r / min for 1.5h to prepare CMC glue;

[0032] 2. Add 0.15 kg of conductive carbon black to the CMC glue prepared above, stir at 1000 r / min for 1.5 h, then draw a vacuum, and continue stirring for 1 h to obtain slurry A;

[0033] 3. 9.5 kg of artificial graphite, 0.7 kg (3.1% of the slurry) of anhydrous ethanol and 3 kg of deionized water were added to the slurry A, and then stirred at 1000 r / min for 1 hour to obtain slurry B;

[0034] 4. Add 0.44 kg of SBR to the above slurry B, then draw a vacuum, stir at 1000 r / min for 2 h, and prepare the negative electrode slurry;

[0035] 5. Use a 250ml glass beaker to take the upper and lower layers of the slurry to be tested respectively, and use a viscometer to calculate the viscosity of the slurry after 0h, 2h, 4h, 6h, 12h, 18h, 24h, and 30h. Use a No. 63 rotor for the test, set the speed to 60r / min, repeat the measurement three times and take the average value; at the same time, take the slurry to be tested and put it into the sample cup, use a stability analyzer to perform stability analysis on the slurry, and scan the sample for 30 hours.

[0036] Example 2

[0037] This embodiment provides a homogenization method capable of improving the sedimentation stability of negative electrode slurry, and the homogenization method comprises the following steps:

[0038] 1. Take 0.15kg of CMC and 7kg of deionized water and stir at 1000r / min for 1.5h to prepare CMC glue;

[0039] 2. Add 0.15 kg of conductive carbon black to the CMC glue prepared above, stir at 1000 r / min for 1.5 h, then draw a vacuum, and continue stirring for 1 h to obtain slurry A;

[0040] 3. 9.5 kg of artificial graphite, 1.1 kg of anhydrous ethanol (accounting for 4.95% of the slurry), anhydrous ethanol and 3 kg of deionized water were added to the above slurry A, and then stirred at 1000 r / min for 1 hour to obtain slurry B;

[0041] 4. Add 0.44 kg of SBR to the above slurry B, then draw a vacuum, stir at 1000 r / min for 2 h, and prepare the negative electrode slurry;

[0042] 5. Use a 250ml glass beaker to take the upper and lower layers of the slurry to be tested respectively, and use a viscometer to calculate the viscosity of the slurry after 0h, 2h, 4h, 6h, 12h, 18h, 24h, and 30h. Use a No. 63 rotor for the test, set the speed to 60r / min, repeat the measurement three times and take the average value; at the same time, take the slurry to be tested and put it into the sample cup, use a stability analyzer to perform stability analysis on the slurry, and scan the sample for 30 hours.

[0043] Example 3

[0044] This embodiment provides a homogenization method capable of improving the sedimentation stability of negative electrode slurry, and the homogenization method comprises the following steps:

[0045] 1. Take 0.15kg of CMC and 7kg of deionized water and stir at 1000r / min for 1.5h to prepare CMC glue;

[0046] 2. Add 0.15 kg of Ketjen black to the CMC glue prepared above, stir at 1000 r / min for 1.5 h, then draw the vacuum, and continue stirring for 1 h to prepare slurry A;

[0047] 3. 9.5 kg of artificial graphite, 1.1 kg of anhydrous ethanol (accounting for 4.95% of the slurry), anhydrous ethanol and 3 kg of deionized water were added to the above slurry A, and then stirred at 1000 r / min for 1 hour to obtain slurry B;

[0048] 4. Add 0.44 kg of SBR to the above slurry B, then draw a vacuum, stir at 1000 r / min for 2 h, and prepare the negative electrode slurry;

[0049] 5. Use a 250ml glass beaker to take the upper and lower layers of the slurry to be tested respectively, and use a viscometer to calculate the viscosity of the slurry after 0h, 2h, 4h, 6h, 12h, 18h, 24h, and 30h. Use a No. 63 rotor for the test, set the speed to 60r / min, repeat the measurement three times and take the average value; at the same time, take the slurry to be tested and put it into the sample cup, use a stability analyzer to perform stability analysis on the slurry, and scan the sample for 30 hours.

[0050] Slurry viscosity test analysis:

[0051] Comparative Example 1: The viscosity of the slurry without anhydrous ethanol after different shelf life is as follows: Figure 1 As shown, after 5 hours of storage, the viscosity of the upper layer of the slurry begins to decrease and the viscosity of the lower layer begins to increase. It can be clearly judged that the slurry begins to stratify and the uniformity of the slurry decreases.

[0052] Comparative Example 2: The viscosity of the slurry with 1.35% anhydrous ethanol added after different shelf life is as follows: Figure 2 As shown, after 5 hours of storage, the viscosity of the upper layer of the slurry begins to decrease and the viscosity of the lower layer begins to increase. It can be clearly judged that the slurry begins to stratify and the uniformity of the slurry decreases.

[0053] Comparative Example 3: The viscosity of the slurry with 6.74% anhydrous ethanol added after different shelf life is tested as follows: Figure 3 As shown, after 5 hours of storage, the viscosity of the upper layer of the slurry begins to decrease and the viscosity of the lower layer begins to increase. It can be clearly judged that the slurry begins to stratify and the uniformity of the slurry decreases.

[0054] Example 1: The viscosity of the slurry with 3.1% anhydrous ethanol added after different shelf life is tested as follows Figure 4 As shown, after 25 hours of storage, the difference between the viscosity of the upper layer and the viscosity of the lower layer of the slurry is still small, and the uniformity of the slurry is still maintained well.

[0055] Example 2: The viscosity of the slurry with 4.95% anhydrous ethanol added after different shelf life is tested as follows: Figure 5 As shown, after 25 hours of storage, the difference between the viscosity of the upper layer and the viscosity of the lower layer of the slurry is still small, and the uniformity of the slurry is still maintained well.

[0056] Example 3: The viscosity of the slurry with 4.95% anhydrous ethanol added after different shelf life is tested as follows: Figure 6 As shown, after 25 hours of storage, the difference between the viscosity of the upper layer and the viscosity of the lower layer of the slurry is still small, and the uniformity of the slurry is still maintained well.

[0057] Comparison of slurry stability coefficients of different homogenization methods:

[0058] Reference Figure 7 It can be obtained that the larger the stability index TSI is, the worse the stability of the system is. In the figure, the TSI indexes of Comparative Example 1, Comparative Example 2 and Comparative Example 3 are significantly greater than those of Example 1, Example 2 and Example 3, which is consistent with the viscosity test results.

[0059] Result analysis: Based on the above test results, it can be seen that the homogenization method provided in this patent can significantly delay the agglomeration and sedimentation of the negative electrode slurry and extend the storage time of the negative electrode slurry.

[0060] The above embodiments only express one or several implementation modes of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the attached claims.

Claims

1. A homogenization method capable of improving the sedimentation stability of negative electrode slurry, characterized in that: The homogenization method comprises the following steps: (1) Mix CMC and deionized water to obtain CMC glue solution; (2) adding a negative electrode conductive agent to the CMC glue solution prepared in step (1), stirring evenly, to prepare a conductive glue solution; (3) stirring the negative electrode active material, deionized water and anhydrous ethanol to obtain a slurry; (4) adding the CMC glue in step 1 to the slurry in step 3 and stirring evenly to obtain a slurry; (5) SBR is added to the slurry in step (4) and stirred evenly to obtain a negative electrode slurry.

2. A homogenization method capable of improving the sedimentation stability of negative electrode slurry according to claim 1, characterized in that: The CMC in step (1) is sodium carboxymethyl cellulose.

3. A homogenization method capable of improving the sedimentation stability of negative electrode slurry according to claim 1, characterized in that: The mass ratios of the negative electrode active material, the negative electrode conductive agent, CMC and SBR are 95:1.5:1.5:2 respectively.

4. A homogenization method capable of improving the sedimentation stability of negative electrode slurry according to claim 1, characterized in that: In step (3), the deionized water is used as a solvent, the anhydrous ethanol is used as a dispersant, the negative electrode active material is artificial graphite or natural graphite, and the negative electrode active material, deionized water and anhydrous ethanol are homogenized to prepare a negative electrode slurry with a solid content of 45%.

5. A homogenization method capable of improving the sedimentation stability of negative electrode slurry according to claim 1, characterized in that: The negative electrode conductive agent in step (2) is conductive carbon black, carbon nanotubes or Ketjen black.

6. A homogenization method capable of improving the sedimentation stability of negative electrode slurry according to claim 1, characterized in that: The SBR in step (5) is styrene-butadiene rubber, and the solid content of the SBR is 45%.

7. A homogenization method capable of improving the sedimentation stability of negative electrode slurry according to claim 4, characterized in that: The mass ratio of the dispersant to the slurry is 3% to 5%.

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