CN-121975131-A - Dispersing agent and preparation method and application thereof

CN121975131ACN 121975131 ACN121975131 ACN 121975131ACN-121975131-A

Abstract

The invention relates to the technical field of batteries, in particular to a dispersing agent and a preparation method and application thereof. The dispersing agent is a copolymer and comprises a main chain formed by copolymerizing an oil-soluble ethylenically unsaturated monomer unit M 1 and an ethylenically unsaturated monomer unit M 2 containing anhydride and/or carboxyl, a polymer side chain R 1 containing ether bond and/or ester bond and grafted on the M 2 unit of the main chain, and a side chain R 2 containing amide group and grafted on the M 2 unit of the main chain. The polymer side chain R 1 ensures the long-term dispersion stability of particles through a steric hindrance effect, the side chain R 2 captures moisture and neutralizes acidic impurities through an amide group of the polymer side chain R 1 to realize chemical passivation of a lithium supplementing agent and inhibit gas production side reaction from the source, and the main chain further optimizes the overall stability of an electrode interface by enhancing the compatibility of each component, so that the cooperative improvement of slurry processability, storage stability and electrochemical cycle performance is realized.

Inventors

LIU SHUANG
YAO YI
WANG TONG
SHI CAIHONG
LIU CHAN
HOU MIN

Assignees

瑞浦兰钧能源股份有限公司
上海瑞浦青创新能源有限公司

Dates

Publication Date: 20260505
Application Date: 20260121

Claims (10)

1. A dispersant, wherein the dispersant is a copolymer comprising: a main chain formed by copolymerizing an oil-soluble ethylenically unsaturated monomer unit M 1 with an acid anhydride-and/or carboxyl-containing ethylenically unsaturated monomer unit M 2 ; An ether and/or ester bond-containing polymer side chain R 1 grafted onto the M 2 units of the backbone; an amide group-containing side chain R 2 grafted onto the M 2 units of the backbone.
2. The dispersant of claim 1 wherein the oil-soluble ethylenically unsaturated monomer unit M 1 has the formula Ar-CH=CH 2 , wherein Ar is unsubstituted phenyl or phenyl substituted with one or more substituents independently selected from C1-C4 alkyl, C1-C4 alkoxy, or halogen; And/or the anhydride and/or carboxyl group-containing ethylenically unsaturated monomer unit M 2 comprises at least one of an ethylenically unsaturated monocarboxylic acid, an ethylenically unsaturated dicarboxylic anhydride, and optionally the anhydride and/or carboxyl group-containing ethylenically unsaturated monomer unit M 2 comprises at least one of maleic anhydride, itaconic anhydride, methacrylic acid, acrylic acid.
3. The dispersant according to claim 1 or 2, wherein the side chain R 1 has a number average molecular weight of 500 to 5000g/mol and comprises at least one of a polyalkylene ether segment or a polyester segment, optionally the side chain R 1 has a number average molecular weight of 500 to 5000g/mol and comprises at least one of a polyethylene oxide chain, a polypropylene oxide chain, a polycaprolactone chain; Optionally, the side chain R 2 comprises at least one of a polyamide chain segment or an alkylamide chain segment, wherein the side chain R 2 comprises at least one of a polyacrylamide short chain segment with the polymerization degree of 2-10, a polyvinylpyrrolidone short chain segment with the polymerization degree of 2-10 and a C1-C12 alkyl chain with an-NH-C (O) -at the tail end; and/OR the tail end of the side chain R 1 and/OR the side chain R 2 contains at least one functional group of-C (O) OR, -C (O) -, and-COOH, wherein R is C1-C4 alkyl; and/or the number average molecular weight of the dispersing agent is 10000-100000 g/mol; and/or the molecular weight distribution of the dispersing agent is 1.1-1.5.
4. A method of preparing the dispersant of any one of claims 1 to 3, comprising the steps of: The main chain synthesis comprises the steps of carrying out copolymerization reaction on an oil-soluble ethylenically unsaturated monomer unit M 1 and an ethylenically unsaturated monomer unit M 2 containing anhydride and/or carboxyl in the presence of a first initiator and a first organic solvent, and carrying out first post-treatment to obtain a main chain copolymer; Grafting R 1 , namely carrying out a first esterification reaction or an ether formation reaction on the main chain copolymer and a hydroxyl-terminated compound R 1 -OH in the presence of a first catalyst and a second organic solvent, and carrying out second post treatment to obtain an intermediate of grafting R 1 ; R 2 is introduced, namely amidation reaction is carried out on the intermediate of the grafting R 1 and a compound R 2 -NH 2 containing terminal amino groups in a third organic solvent, and the dispersant is obtained through third post treatment.
5. The method according to claim 4, wherein in the step of synthesizing the main chain, the molar ratio of M 1 to M 2 is (1-3) 1; and/or the copolymerization is carried out for 4-8 hours at 60-80 ℃; And/or, in the R 1 grafting step, the molar ratio of the M 2 unit to R 1' -OH in the main chain copolymer is 1 (0.3-0.8); And/or the first esterification reaction or the ether formation reaction is carried out for 6-12 hours at the temperature of 40-70 ℃; And/or, in the step of introducing R 2 , calculating the amount of the residual M 2 units which do not react with R 1 -OH based on the initial feeding amount of the M 2 units in the main chain copolymer and the feeding amount of R 1 -OH in the step of grafting R 1 , wherein the feeding molar ratio of the residual M 2 units to R 2 -NH 2 is 1 (0.5-1).
6. The method according to claim 4 OR 5, further comprising a functional group modification step of introducing a-C (O) OR, -COOH OR-C (O) -functional group at the terminal of the side chain R 1 and/OR the side chain R 2 by a second esterification reaction, hydrolysis reaction OR oxidation reaction after the step of introducing R 2 ; and/or the first initiator comprises at least one of azodiisobutyronitrile and benzoyl peroxide; and/or the first organic solvent comprises at least one of toluene, tetrahydrofuran and ethyl acetate; and/or the first catalyst comprises at least one of tetrabutyl titanate and stannous octoate; and/or the second organic solvent comprises at least one of toluene, tetrahydrofuran and ethyl acetate; And/or the third organic solvent comprises at least one of N, N-dimethylformamide and dimethyl sulfoxide; And/or, the first post-treatment comprises precipitation in methanol and drying; And/or, the second post-treatment comprises precipitation in water and drying; And/or, the third post-treatment comprises dialysis or column chromatography purification and drying.
7. A positive electrode sheet comprising a positive electrode active material, a positive electrode lithium-supplementing agent, a conductive agent, a binder, and the dispersant according to any one of claims 1 to 3 or the dispersant produced by the method for producing a dispersant according to any one of claims 4 to 6.
8. The positive electrode sheet according to claim 7, wherein the mass ratio of the positive electrode active material is 94 to 96.5%, the mass ratio of the positive electrode lithium supplementing agent is 0.3 to 5%, and the total mass ratio of the conductive agent, the binder and the dispersing agent is 2.5 to 5.5%, based on 100% of the total mass of the solid materials in the positive electrode active material layer in the positive electrode sheet; And/or the mass ratio of the conductive agent, the binder and the dispersing agent is (0.5-2): 1.2-2.5): 0.05-0.5; And/or the positive electrode lithium supplementing agent comprises at least one of lithium ferrite and lithium nickelate; And/or the conductive agent comprises at least one of conductive carbon black, carbon nano tube, carbon fiber and graphene; and/or the binder comprises at least one of polyacrylate, polyimide, polyvinyl alcohol, polyamide imide, polyvinylidene fluoride, polystyrene butadiene copolymer, polytetrafluoroethylene, sodium carboxymethyl cellulose, potassium carboxymethyl cellulose and sodium hydroxymethyl cellulose; and/or the positive electrode active material includes at least one of lithium iron phosphate and lithium manganese iron phosphate.
9. A method for preparing the positive electrode sheet according to claim 7 or 8, comprising the steps of: Mixing a conductive agent, a binder, the dispersing agent and a fourth organic solvent to prepare a conductive glue solution; Adding an anode active material and an anode lithium supplementing agent into the conductive glue solution, and obtaining anode slurry through stirring dispersion and vacuum defoaming; and coating the positive electrode slurry on a current collector, and drying and rolling to obtain the positive electrode plate.
10. A secondary battery comprising the positive electrode sheet according to claim 7 or 8 or the positive electrode sheet produced by the production method according to claim 9.

Description

Dispersing agent and preparation method and application thereof Technical Field The invention relates to the technical field of batteries, in particular to a dispersing agent and a preparation method and application thereof. Background With the rapid development of clean energy, the energy density and cycle life requirements of secondary batteries are increasingly increasing. The positive electrode materials such as lithium iron phosphate (LiFePO 4, LFP) are widely applied in the fields of power batteries and energy storage due to the advantages of good thermal stability, long cycle life, low cost and the like. However, the theoretical capacity is limited, and irreversible capacity loss is caused by formation of a solid electrolyte interface film (SEI) during the first charge and discharge, which restricts further improvement of the energy density of the battery. In order to compensate the first coulombic efficiency loss, the introduction of lithium-supplementing agents becomes an effective technical means, wherein lithium ferrite (Li 5FeO4, LFO) and lithium nickelate (Li 2NiO2, LNO) are regarded as positive electrode lithium-supplementing materials with application prospect due to high theoretical lithium-supplementing capacity and proper lithium-removing potential. However, in the implementation process of the lithium iron phosphate prelithiation, two outstanding problems are that on one hand, nanoscale lithium iron phosphate particles are higher than surface energy, agglomeration is easy to occur in oil-based slurry due to the action of Van der Waals force, slurry viscosity is high, fluidity is poor, the real density of particles is high, coating uniformity is easy to settle, and the quality and production efficiency of pole pieces are affected, and on the other hand, high-capacity lithium supplementing agents such as lithium ferrite, lithium nickelate and the like are extremely sensitive to moisture and acidic substances, and are easy to react with water to release hydrogen in the preparation, battery formation and storage of the slurry, or gas such as carbon dioxide is generated by catalytic decomposition of electrolyte, so that the property fluctuation of the slurry and the gas expansion of the battery are caused. The conventional dispersing agent has insufficient anchoring capability on nano particles, is difficult to inhibit viscosity rebound and sedimentation, and cannot inhibit the gas production of the lithium supplementing agent, and the independent coating of the lithium supplementing agent can partially relieve the gas production, but has complex process and high cost, and is not helpful for improving the dispersibility of the slurry. The existing means are difficult to simultaneously process the control requirements of stable particle dispersion and interfacial reaction of lithium supplementing agents, so that the slurry processing performance is poor, the gas production of the battery is serious, and finally the electrochemical cycle performance of the battery is reduced. Disclosure of Invention The invention provides a dispersing agent and a preparation method and application thereof, and aims to solve the problems of poor slurry processing performance, serious gas production of a battery and reduced electrochemical cycle performance caused by poor dispersion stability of nano lithium iron phosphate particles and difficult cooperative control of chemical gas production of a lithium supplementing agent in the existing lithium iron phosphate prelithiation process. In a first aspect, the present invention provides a dispersant which is a copolymer comprising: a main chain formed by copolymerizing an oil-soluble ethylenically unsaturated monomer unit M 1 with an acid anhydride-and/or carboxyl-containing ethylenically unsaturated monomer unit M 2; An ether and/or ester bond-containing polymer side chain R 1 grafted onto the M 2 units of the backbone; an amide group-containing side chain R 2 grafted onto the M 2 units of the backbone. In one specific schematic structure, the dispersant has a random copolymer structure represented by the following formula (I): [(M1)α-(M2-R1)β-(M2-R1-R2)γ-(M2-R2)δ]n(I); Wherein, alpha, beta, gamma and delta respectively represent the mole fraction of the corresponding structural units, alpha is more than 0, beta is more than or equal to 0, gamma is more than or equal to 0, delta is more than or equal to 0, beta+gamma+delta is more than 0;n and represents the number of the repeated units of the copolymer. In an alternative embodiment, the oil-soluble ethylenically unsaturated monomer unit M 1 has the formula Ar-CH=CH 2, wherein Ar is unsubstituted phenyl or phenyl substituted with one or more substituents independently selected from C1-C4 alkyl, C1-C4 alkoxy or halogen, optionally, the oil-soluble ethylenically unsaturated monomer unit M 1 comprises at least one of styrene, alpha-methylstyrene (purity. Gtoreq.99%, polymerization inhibitor removed by reduced pressure