Aqueous Binder Composition for Secondary Battery Cathodes
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Solution Overview
Problem
Current lithium-ion battery binders, such as PVDF, are insoluble in water and require toxic organic solvents like NMP, leading to environmental and health risks, while aqueous binders like CMC and SBR offer poor adhesion and stability, especially at high voltages, limiting their application in cathodes.
Innovation Solution
A binder composition comprising a copolymer with structural units derived from carboxylic acid, amide, nitrile, and hydroxyl group-containing monomers, along with an anionic reactive emulsifier, which enhances adhesion and electrochemical performance in aqueous media, allowing for the preparation of cathodes without toxic solvents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PVDF binder is used, then electrochemical stability and binding capability are improved, but environmental safety and ease of manufacture deteriorate due to requirement of toxic organic solvents like NMP
Solution Approach 1:
The invention changes the chemical composition parameters of the binder by introducing a copolymer with specific functional groups (carboxylic acid, amide, nitrile, hydroxyl) that enable water solubility while maintaining electrochemical stability. This parameter change allows the binder to dissolve in water instead of toxic organic solvents like NMP, thus improving environmental safety while preserving binding capability
Solution Approach 2:
The invention uses a composite binder system comprising a copolymer made from multiple monomer units with different functional groups. The copolymer combines the electrochemical stability provided by nitrile and amide groups with the water solubility provided by carboxylic acid and hydroxyl groups, creating a material that exhibits both environmental safety and reliable binding performance
2Object-affected harmful factors
If aqueous binders like CMC or SBR are used, then environmental safety is improved, but adhesion capability and reliability deteriorate, especially at high voltages
Solution Approach 1:
The invention modifies the binder's chemical structure by incorporating multiple functional groups (carboxylic acid, amide, nitrile, hydroxyl) in specific proportions. The carboxylic acid and hydroxyl groups provide water solubility for environmental safety, while the amide and nitrile groups contribute to electrochemical stability and adhesion capability at high voltages, thus improving reliability without sacrificing environmental safety
Solution Approach 2:
Different segments of the copolymer chain provide different local properties: some segments with carboxylic acid and hydroxyl groups interact with water and electrode surfaces to provide adhesion, while other segments with amide and nitrile groups provide electrochemical stability. This local differentiation of functional properties enables the binder to simultaneously achieve environmental safety and high adhesion capability
3Strength
If PVDF binder is used, then binding capability is improved, but device complexity increases due to requirement of NMP recovery system
Solution Approach 1:
The invention extracts and eliminates the need for the NMP recovery system by using a water-based binder system. Water is non-toxic and does not require complex recovery equipment, thus removing the harmful factor and associated manufacturing complexity while maintaining binding capability through the specially designed copolymer structure
4Ease of manufacture
If SBR binder is used, then ease of manufacture is improved by using water-based slurry, but reliability deteriorates due to poor adhesion, high expandability, and decomposition at high voltage
Solution Approach 1:
The invention changes the chemical composition from simple SBR to a complex copolymer containing carboxylic acid, amide, nitrile, and hydroxyl groups. This parameter change maintains water-based slurry processing (ease of manufacture) while the specific functional groups provide electrochemical stability and prevent decomposition at high voltages (improving reliability)
Data Source
AI summary
An aqueous binder composition for a secondary battery electrode is provided, 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, a structural unit (d) derived from a hydroxyl 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 exhibit exceptional electrochemical performance.