Binder composition for secondary battery
Provided is an aqueous binder composition for a secondary battery electrode, comprising a copolymer and a dispersion medium, wherein the copolymer comprises a structural unit (a) derived from a carboxylic acid group-containing monomer, a structural unit (b) derived from an amide group-containing monomer, a structural unit (c) derived from a nitrile group-containing monomer, and at least one anionic reactive emulsifier, with an improved binding capability. In addition, battery cells comprising the cathode prepared using the binder composition disclosed herein exhibits exceptional electrochemical performance.
1. A binder composition for a secondary battery electrode comprising a copolymer and a dispersion medium, wherein the copolymer comprises a structural unit (a) derived from a carboxylic acid group-containing monomer, a structural unit (b) derived from an amide group-containing monomer, a structural unit (c) derived from a nitrile group-containing monomer, and at least one anionic reactive emulsifier, wherein the binder composition is free of a structural unit derived from an ester group-containing monomer, wherein the structural unit (c) derived from a nitrile group-containing monomer has a proportion in the copolymer of from about 50% to about 70% by mole, based on the total number of moles of monomeric units in the copolymer in the binder composition, and wherein the anionic reactive emulsifier in the binder composition has a proportion of from about 0.1 to about 5 wt %, based on the total weight of monomers added in the preparation of the binder composition.
2. The binder composition according to claim 1 , wherein the carboxylic acid group-containing monomer is selected from the group consisting of acrylic acid, methacrylic acid, crotonic acid, 2-butyl crotonic acid, cinnamic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, itaconic anhydride, tetraconic acid, 2-ethylacrylic acid, isocrotonic acid, cis-2-pentenoic acid, trans-2-pentenoic acid, angelic acid, tiglic acid, 3,3-dimethyl acrylic acid, 3-propyl acrylic acid, trans-2-methyl-3-ethyl acrylic acid, cis-2-methyl-3-ethyl acrylic acid, 3-isopropyl acrylic acid, trans-3-methyl-3-ethyl acrylic acid, cis-3-methyl-3-ethyl acrylic acid, 2-isopropyl acrylic acid, trimethyl acrylic acid, 2-methyl-3,3-diethyl acrylic acid, 3-butyl acrylic acid, 2-butyl acrylic acid, 2-pentyl acrylic acid, 2-methyl-2-hexenoic acid, trans-3-methyl-2-hexenoic acid, 3-methyl-3-propyl acrylic acid, 2-ethyl-3-propyl acrylic acid, 2,3-diethyl acrylic acid, 3,3-diethyl acrylic acid, 3-methyl-3-hexyl acrylic acid, 3-methyl-3-tert-butyl acrylic acid, 2-methyl-3-pentyl acrylic acid, 3-methyl-3-pentyl acrylic acid, 4-methyl-2-hexenoic acid, 4-ethyl-2-hexenoic acid, 3-methyl-2-ethyl-2-hexenoic acid, 3-tert-butyl acrylic acid, 2,3-dimethyl-3-ethyl acrylic acid, 3,3-dimethyl-2-ethyl acrylic acid, 3-methyl-3-isopropyl acrylic acid, 2-methyl-3-isopropyl acrylic acid, trans-2-octenoic acid, cis-2-octenoic acid, trans-2-decenoic acid, α-acetoxyacrylic acid, β-trans-aryloxyacrylic acid, α-chloro-β-E-methoxyacrylic acid, methyl maleic acid, dimethyl maleic acid, phenyl maleic acid, bromo maleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid, difluoro maleic acid, nonyl hydrogen maleate, decyl hydrogen maleate, dodecyl hydrogen maleate, octadecyl hydrogen maleate, fluoroalkyl hydrogen maleate, maleic anhydride, methyl maleic anhydride, dimethyl maleic anhydride, acrylic anhydride, methacrylic anhydride, methacrolein, methacryloyl chloride, methacryloyl fluoride, methacryloyl bromide and combinations thereof.
3. The binder composition according to claim 1 , wherein the structural unit (a) derived from a carboxylic acid group-containing monomer has a proportion in the copolymer of from about 2% to about 15% by mole, based on the total number of moles of monomeric units in the copolymer in the binder composition.
4. The binder composition according to claim 1 , wherein the amide group-containing monomer is selected from the group consisting of methacrylamide, N-methyl methacrylamide, N-ethyl methacrylamide, N-n-propyl methacrylamide, N-isopropyl methacrylamide, N-n-butyl methacrylamide, N-isobutyl methacrylamide, N,N-dimethyl acrylamide, N,N-dimethyl methacrylamide, N,N-diethyl acrylamide, N,N-diethyl methacrylamide, N-methylol methacrylamide, N-(methoxymethyl)methacrylamide, N-(ethoxymethyl)methacrylamide, N-(propoxymethyl)methacrylamide, N-(butoxymethyl)methacrylamide, N,N-dimethyl methacrylamide, N,N-dimethylaminopropyl methacrylamide, N,N-dimethylaminoethyl methacrylamide, N,N-dimethylol methacrylamide, diacetone methacrylamide, methacryloyl morpholine and combinations thereof.
5. The binder composition according to claim 1 , wherein the structural unit (b) derived from an amide group-containing monomer has a proportion in the copolymer of from about 20% to about 40% by mole, based on the total number of moles of monomeric units in the copolymer in the binder composition.
6. The binder composition according to claim 1 , wherein the nitrile group-containing monomer is selected from the group consisting of acrylonitrile, α-halogenoacrylonitrile, α-alkylacrylonitrile, α-chloroacrylonitrile, α-bromoacrylonitrile, α-fluoroacrylonitrile, methacrylonitrile, α-ethylacrylonitrile, α-isopropylacrylonitrile, α-n-hexylacrylonitrile, α-methoxyacrylonitrile, 3-methoxyacrylonitrile, 3-ethoxyacrylonitrile, α-acetoxyacrylonitrile, α-phenylacrylonitrile, α-tolylacrylonitrile, α-(methoxyphenyl)acrylonitrile, α-(chlorophenyl)acrylonitrile, α-(cyanophenyl)acrylonitrile, vinylidene cyanide and combinations thereof.
7. The binder composition according to claim 1 , wherein the dispersion medium is water.
8. The binder composition according to claim 7 , wherein the dispersion medium further comprise a hydrophilic solvent selected from the group consisting of ethanol, isopropanol, n-propanol, tert-butanol, n-butanol, dimethylacetamide (DMAc), dimethylformamide (DMF), N-methylpyrrolidone (NMP), methyl ethyl ketone (MEK), ethyl acetate (EA), butyl acetate (BA) and combinations thereof.
9. The binder composition according to claim 1 , wherein the anionic reactive emulsifier is selected from the group consisting of sodium 2-acrylamido-2-methyl-1-propanesulfonate (AMPS-Na), sodium hydroxypropane sulfonate, sodium dodecyl allyl sulfosuccinate, sodium 1-allyloxy-2 hydroxypropyl sulfonate (COPs-1), sodium vinyl sulfonate (SVS), sodium vinyl alkyl sulfonate, sodium styrene sulfonate, allyloxy fatty alcohol polyoxyethylene ether ammonium sulfate, allyloxy alkyl phenol polyoxyethylene ether ammonium sulfate, polyoxyethylene allyloxy nonylphenoxypropyl ether ammonium sulfate, alkyl allyl sulfosuccinate, methacrylic acid polyoxyalkylene sulfate ester salt, ethylene glycol methacrylate sulfate ester salt, polyoxyethylene alkyl propenyl phenyl ether sulfate ammonium salt, α-sulfo-ω-(1-(nonylphenoxy) methyl-2-(2-propenyloxy) ethoxy)-poly (oxy-1,2-ethanediyl) ammonium salt, polyoxyethylene-1-(allyloxymethyl) alkyl ether sulfate ammonium salt, polyoxyalkylene alkenyl ether ammonium sulfate, sodium allyloxy hydroxypropyl sulfonates, sodium methallyl sulfonates, sulfopropyl acrylate, vinyl sulfonate, vinyl phosphate, monosodium ethylsulfonate monododecyl maleate, allylsulfosuccinate derivatives and combinations thereof.
10. The binder composition according to claim 1 , wherein the anionic reactive emulsifier in the binder composition has a proportion of from about 0.02% to about 3% by mole, based on the total number of moles of monomeric units in the copolymer in the binder composition.
11. The binder composition according to claim 1 , wherein the anionic reactive emulsifier has a molar ratio of from about 0.01% to about 4% relative to structural unit (c) in the copolymer.
12. The binder composition according to claim 1 , wherein the binder composition has a pH of from about 7 to about 9; wherein the binder composition has a viscosity of from about 3,000 mPa·s to about 5,000 mPa·s; and wherein the binder composition swells in electrolyte by from about 3% to about 5%.
13. The binder composition according to claim 1 , wherein the binder composition and a current collector has an adhesive strength of from about 4 N/cm to about 6 N/cm.
14. The binder composition according to claim 1 , wherein the anionic reactive emulsifier in the binder composition has a proportion of from about 0.5 to about 4 wt %, based on the total weight of monomers added in the preparation of the binder composition.
15. The binder composition according to claim 1 , wherein the binder composition is free of a structural unit derived from a conjugated diene group-containing monomer; and wherein the binder composition is free of a structural unit derived from an aromatic vinyl group-containing monomer.
16. The binder composition according to claim 1 , wherein the binder composition has a solid content of from about 10% to about 25% by weight, based on the total weight of the binder composition.
17. An electrode for a secondary battery, comprising an electrode active material, a conductive agent and the binder composition according to claim 1 .
18. The electrode according to claim 17 , wherein the peeling strength between the current collector and the electrode layer is in the range from about 1.0 N/cm to about 8.0 N/cm.
19. The binder composition according to claim 1 , wherein the secondary battery is a lithium ion secondary battery.