A dispersant for block polyether lithium battery positive electrode slurry

Abstract

The present invention claims protection for a block polyether dispersant for lithium battery positive electrode slurry, having the following structure: #imgabs0# wherein R represents a group #imgabs1# a and b each independently represent an integer of 0-100, c represents an integer of 0-50, and a cannot be 0, and b and c cannot be 0 at the same time. The dispersant of the present invention is particularly suitable for lithium battery positive electrode slurry. It can reduce the risk of secondary aggregation of solid particles in the positive electrode slurry while ensuring that the conductive performance of the lithium battery is not affected, improve the fluidity of the positive electrode slurry, thereby reducing the resistance of the electrode sheet, increasing the gram capacity of the battery, and reducing the battery AC internal resistance.

Description

Technical Field

[0001] The present invention relates to a dispersant for lithium ion battery positive electrode slurry, in particular to a block polyether dispersant, belonging to the technical field of lithium batteries. Background Art

[0002] Lithium-ion batteries are widely used in aerospace, national defense, automobiles, 3C and other fields due to their advantages such as high specific energy, long cycle life, low self-discharge rate, no memory effect and environmental friendliness.

[0003] Lithium-ion batteries are composed of a positive electrode, a negative electrode, a separator and an electrolyte. Taking lithium iron phosphate batteries as an example, the reaction that occurs during charging is: LiFePO4→Li-xFePO4+xLi+x e- , the reaction that occurs during discharge: Li-xFePO4+xLi++x e- →LiFePO4, in short, the working principle of lithium-ion batteries is the flow of electrons between the positive and negative electrodes.

[0004] When lithium-ion batteries are formed, the prepared slurry containing electrode active materials needs to be coated on aluminum foil to form the positive and negative electrodes respectively. Therefore, the viscosity of the slurry is directly related to the coating quality. Given the current increasingly high requirements for lithium battery capacity, the usual solution is to increase the proportion of electrode active materials in the slurry. However, this will result in an excessively high solid content in the slurry, resulting in viscosity and poor fluidity, which affects the electrode coating effect and further affects the efficiency of the lithium battery preparation process.

[0005] To address the above issues, the current solution in the industry is to add dispersants to the slurry to improve the dispersion effect of the slurry. Existing dispersants include polyvinyl pyrrolidone, phosphite, Triton-X, etc. These dispersants can solve the fluidity problem of the slurry to a certain extent, but they are still not powerful enough to solve the viscosity, gel and other problems of the slurry. In addition, the safety of these dispersants is not high. Summary of the Invention

[0006] The present invention aims to solve the problem that positive electrode slurry for lithium ion batteries has poor viscosity and fluidity, which affects the electrode coating effect and leads to increased electrode sheet resistance and reduced gram capacity. The present invention provides a block polyether dispersant for positive electrode slurry of lithium ion batteries.

[0007] The technical solution of the present invention to solve the above technical problems is as follows:

[0008] A block polyether dispersant for lithium battery positive electrode slurry has the following structural formula:

[0009]

[0010] Wherein, R represents a group a and b each independently represent an integer from 0 to 100, and c represents an integer from 0 to 50. A cannot be 0, and both b and c cannot be 0 at the same time.

[0011] Preferably, a and b each independently represent an integer of 0-80, and c represents an integer of 0-30, and a cannot be 0, and b and c cannot be 0 at the same time.

[0012] More preferably, a and b each independently represent an integer of 10-50, and c represents an integer of 0-20.

[0013] The dispersant of the present invention can be prepared by using Tetronic 90R4 purchased from Sigma as a raw material and reacting it with butylene oxide through a nucleophilic substitution reaction under base catalysis and reaction conditions of 140-150° C. The process is as follows:

[0014]

[0015] Wherein, EO represents ethoxy-C2H4O-, PO represents propoxy-C3H6O-, BO represents butoxy-C4H8O-, and the carbon chains in the propoxy and butoxy groups may be linear or branched.

[0016] The working principle of the dispersant for lithium-ion battery positive electrode slurry claimed in the present invention is as follows:

[0017] The block polyether structure contains three segments: ethoxy (EO), propoxy (PO), and butoxy (BO). The PO and BO segments exhibit hydrophobic properties in aqueous solution, while the EO segment is water-affinity, making the entire molecule amphiphilic. The long-chain structure of the block polyether can form an effective steric hindrance in the slurry, preventing solid particle sedimentation and effectively inhibiting gelation. From a microscopic interface perspective, the hydrophilic and lipophilic groups can effectively reduce the surface tension of the solid-liquid interface, improve wetting and penetration properties, increase the solid content of the electrode active material and ease of coating, and facilitate the uniform dispersion of particles such as the electrode active material and conductive carbon, thereby improving battery performance.

[0018] The beneficial effects of the dispersant provided by the present invention are:

[0019] (1) The dispersant of the present invention is particularly suitable for lithium battery positive electrode slurry. It can reduce the risk of secondary aggregation of solid particles in the positive electrode slurry while ensuring that the conductive performance of the lithium battery is not affected, improve the fluidity of the positive electrode slurry, and thus reduce the resistance of the electrode sheet, increase the gram capacity of the battery, and reduce the AC internal resistance of the battery;

[0020] (2) The dispersant of the present invention does not need to be matched with a special pulping process. The dispersant of the present invention can be added proportionally to the original pulping process to achieve the dispersion and viscosity reduction effect of the slurry without increasing the process cost.

[0021] The present invention also claims protection for a lithium-ion battery positive electrode slurry comprising the above-mentioned dispersant.

[0022] Preferably, the positive electrode slurry further comprises a positive electrode active material and a conductive agent.

[0023] Preferably, the positive electrode active material is one or more of lithium cobalt oxide, lithium iron phosphate, nickel cobalt manganese ternary material, and nickel cobalt aluminum oxide ternary material; the conductive agent is one of carbon black or carbon nanotubes or a combination of the two.

[0024] Preferably, the positive electrode slurry further comprises a binder and an organic solvent, the binder is polyvinylidene fluoride, and the organic solvent is N-methylpyrrolidone.

[0025] The present invention also claims protection for a positive electrode plate of a lithium ion battery, the surface of which is coated with the aforementioned positive electrode slurry for the lithium ion battery.

[0026] The present invention also claims protection for a lithium-ion battery comprising the aforementioned positive electrode sheet. DETAILED DESCRIPTION

[0027] The principles and features of the present invention are described below with reference to examples. The examples are only used to explain the present invention and are not used to limit the scope of the present invention.

[0028] The structural formulas of the dispersants used in the examples are shown in Table 1.

[0029]

[0030] R represents a group

[0031] Table 1 Structural formula of each dispersant

[0032]

[0033]

[0034] The dispersants in the present invention can be prepared by the preparation method described in the specification. Taking dispersant C as an example, the preparation method of dispersant C is as follows:

[0035] Sigma's Tetronic 90R4 product and butylene oxide were used as raw materials in a molar ratio of 1:100. Under the catalytic action of KOH, they were dissolved in tetrahydrofuran and stirred under N2 protection, 140-150°C, and 0.3 MPa to react to produce dispersant C.

[0036] Example 1: Effect of application in wet pulping process

[0037] The specific preparation steps of the lithium battery positive electrode slurry for experimental groups 1-5 and control group 1 are as follows:

[0038] 1) Mixing and stirring the binder and the organic solvent to obtain a glue solution A;

[0039] 2) adding the aforementioned dispersants A to the above-mentioned glue solution A respectively and stirring evenly to obtain glue solution B;

[0040] 3) Adding the conductive agent to the glue solution B to obtain a conductive agent slurry;

[0041] 4) Adding the positive electrode active material to the conductive agent slurry to obtain a positive electrode slurry.

[0042] The weight ratio of each raw material in the above method is, positive electrode active material: conductive agent: dispersant: binder = 93:3:3:1; wherein the positive electrode active material is lithium iron phosphate produced by Hunan Yuneng New Energy Battery Materials Co., Ltd., the conductive agent is a mixture of conductive carbon black and carbon nanotubes in a mass ratio of 1:1, the binder is polyvinylidene fluoride, the organic solvent is N-methylpyrrolidone, and the dispersants used in Examples 1-5 are dispersant A, dispersant B, dispersant C, dispersant D and dispersant E, respectively.

[0043] No dispersant was added to the control group 1, and the other components of the slurry were the same as those of the experimental groups 1-5.

[0044] Take the freshly prepared slurry for testing respectively. After standing for 24 hours, stir the slurry for 1 minute and then test it. Use Lichen ND-10 rotational viscometer with rotor 2 and insert the rotor into the slurry to be tested. The test speed is 100 rpm and the test time is 60 s. The viscosity value of the slurry is obtained by taking the average value of multiple points. The test results are shown in Table 1.

[0045] Table 1 Slurry viscosity and solid content of experimental groups 1-5 and control group 1

[0046]

[0047] It can be seen from the data in Table 1 that after the dispersant of the present invention was added to the experimental groups 1-5, the solid content of the freshly prepared slurry increased by 2-6% relative to the control group 1. After 24 hours, the slurry of the control group 1 gelled, while the slurries of the experimental groups 1-5 still had good fluidity, indicating that the dispersant of the present invention has a good dispersing effect on the positive electrode slurry obtained by the wet pulping process.

[0048] Example 2: Effect of application in dry pulping process

[0049] The specific preparation process of the lithium battery positive electrode slurry for experimental groups 6-10 and control group 2 is as follows:

[0050] 1) dry-mixing the binder, the conductive agent and the positive electrode active material to obtain a uniformly mixed powder;

[0051] 2) adding a portion of the organic solvent to the above powder and stirring uniformly to obtain an initial slurry A;

[0052] 3) adding the dispersant of the present invention to the initial slurry A and stirring evenly;

[0053] 4) On the basis of step 3), the remaining organic solvent is added and stirred evenly to obtain a positive electrode slurry.

[0054] Among them, the weight ratio of each raw material is, positive electrode active material: conductive agent: dispersant: binder = 95:3:1:1; the positive electrode active material is lithium cobalt oxide, the conductive agent is a mixture of conductive carbon black and carbon nanotubes in a mass ratio of 1:1, the binder is polyvinylidene fluoride, the organic solvent is N-methylpyrrolidone, and the dispersants used in Examples 6-10 are dispersant A, dispersant B, dispersant C, dispersant D and dispersant E, respectively.

[0055] Take the freshly prepared slurry for testing respectively. After standing for 24 hours, stir the slurry for 1 minute and then test it. Use Lichen ND-10 rotational viscometer with rotor 2 and insert the rotor into the slurry to be tested. The test speed is 100 rpm and the test time is 60 seconds. The viscosity value of the slurry is obtained by taking the average value of multiple points. The test results are shown in Table 2.

[0056] Table 2 Slurry viscosity and solid content of experimental groups 6-10 and control group 2

[0057]

[0058] It can be seen from the data in Table 2 that after adding the dispersing aid of the present invention to the positive electrode slurry of experimental groups 6-10, the solid content of the freshly prepared slurry increased by 3-7% compared with the control group 2, and the initial viscosity was slightly improved. After 24 hours, the slurry of the control group 2 gelled, while the slurry of the experimental groups 6-10 still had good fluidity, indicating that the dispersant of the present invention also has a good dispersing effect on the positive electrode slurry obtained by the dry method.

[0059] Example 3: Comparative experimental results with existing dispersants

[0060] The preparation method of the lithium battery positive electrode slurry for the experimental groups 11-12 and the control groups 3-5 is as follows:

[0061] 1) Mixing and stirring the binder and the organic solvent to obtain a glue solution A;

[0062] 2) adding a dispersant to the above-mentioned glue solution A and stirring uniformly to obtain glue solution B;

[0063] 3) Adding the conductive agent to the glue solution B to obtain a conductive agent slurry;

[0064] 4) Adding the positive electrode active material to the conductive agent slurry to obtain a positive electrode slurry.

[0065] Among them, the weight ratio of each raw material is, positive electrode active material: conductive agent: dispersant: binder = 93:3:3:1; the positive electrode active material is lithium iron phosphate produced by Hunan Yuneng New Energy Battery Materials Co., Ltd., the conductive agent is a mixture of conductive carbon black and carbon nanotubes in a mass ratio of 1:1, the binder is polyvinylidene fluoride, the organic solvent is N-methylpyrrolidone, the dispersant of experimental group 11 is dispersant C, the dispersant of control group 3 is polyvinylpyrrolidone, the dispersant of control group 4 is triethyl phosphite, and the dispersant of control group 5 is Triton X.

[0066] The slurry just prepared was tested. After standing for 24 hours, the slurry was stirred for 1 minute and then tested. The Lichen ND-10 rotational viscometer was used. The 2# rotor was inserted into the slurry to be tested. The test speed was 100 rpm and the test time was 60 s. The multi-point average method was used to obtain the viscosity value of the slurry. The test results are shown in Table 3.

[0067] Table 3 Slurry viscosity and solid content of experimental group 11 and control group 3-5

[0068]

[0069] It can be seen from the data in Table 3 that the dispersant of the present invention has a relatively higher solid content in the obtained positive electrode slurry than other existing dispersants, and the viscosity of the slurry obtained after being placed for 24 hours is significantly reduced, which has a significant effect of improving the fluidity of the slurry.

[0070] 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, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. Application of block polyether compounds as dispersants for lithium battery positive electrode slurries, characterized in that: It has the following structural formula: Wherein, R represents a group a and b each independently represent an integer from 0 to 100, and c represents an integer from 0 to 50, and a cannot be 0 and c cannot be 0.

2. The use according to claim 1, characterized in that a and b each independently represent an integer from 0 to 80, and c represents an integer from 0 to 30, and a cannot be 0 and c cannot be 0.

3. The use according to claim 2, characterized in that a and b each independently represent an integer of 10-50, and c represents an integer of 0-20.

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