Lithium Ion Battery Copolymer Binder Slurry Stability
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Solution Overview
Problem
Current electrode binders for lithium ion secondary batteries face issues such as low bonding properties between active materials and current collectors, aggregation in slurry, and cracking of the electrode active material layer, which affect the battery's performance and manufacturing costs.
Innovation Solution
A copolymer comprising specific structural units derived from monomers with controlled ethylenically unsaturated bonds and partition coefficients, used to form a slurry with improved dispersibility and bonding properties, reducing aggregation and cracking while enhancing peel strength to the current collector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If PVDF binder containing NMP solvent is used, then the binder provides bonding between active materials and current collector, but the bonding properties are insufficient and large amount of binder is required reducing battery capacity
Solution Approach 1:
The invention changes the chemical composition parameters of the binder by using a copolymer with specific structural units (acrylic acid, methacrylic acid, and their salts) in controlled proportions. This compositional parameter change enables achieving sufficient bonding properties with reduced binder quantity, directly addressing the contradiction between bonding strength and binder amount.
2Ease of manufacture
If NMP solvent is used as binder solvent, then the binder can be applied, but the manufacturing cost increases due to expensive solvent
Solution Approach 1:
The invention replaces the expensive NMP solvent with water as the binder solvent. Water is a cheap, readily available substance that eliminates the need for costly organic solvent recovery and handling processes, directly reducing manufacturing cost while maintaining binder application capability.
3Adaptability or versatility
If SBR-based binder with CMC thickener is used, then the binder is water-dispersible, but the slurry preparation process becomes complicated
Solution Approach 1:
The invention extracts and eliminates the CMC thickener component from the binder system. The copolymer binder itself provides adequate slurry preparation properties without requiring additional thickening agents, thereby simplifying the slurry preparation process while maintaining water dispersibility.
4Quantity of substance
If small amount of binder is used with SBR-based binder, then the binder quantity is reduced, but active material peeling occurs during current collector cutting
Solution Approach 1:
The invention changes the chemical composition parameters of the binder by incorporating specific ratios of acrylic acid, methacrylic acid, and their salts, which provide enhanced bonding characteristics. This compositional optimization enables achieving reliable bonding with reduced binder quantity, preventing active material peeling during cutting operations.
5Strength
If sodium acrylate-N-vinylacetamide copolymer is used, then the binder shows adhesive properties, but aggregates are easily generated in slurry
Solution Approach 1:
The invention changes the copolymer composition by replacing N-vinylacetamide units with salts of (meth)acrylic acid and controlling the ratio of acrylic acid to methacrylic acid units. This parameter change improves slurry stability and prevents aggregate formation while maintaining adequate adhesive properties.
Data Source
AI summary
To provide a copolymer for a binder for an electrode and a slurry for a lithium ion secondary battery using the copolymer for an electrode binder, in which the peel strength of an electrode active material layer to a collector is high while suppressing the generation of aggregates in a slurry containing the electrode active material and suppressing the generation of cracks in the electrode active material layer formed on the collector. The copolymer for an electrode binder comprises a structural unit derived from a monomer (A) represented by formula (1), a structural unit derived from a monomer (B) which is at least 1 kind selected from the group consisting of (meth)acrylic acid and its salts, a structural unit derived from a monomer (C) represented by formula (2), a structural unit derived from a hydrophilic monomer (D) having only 1 ethylenically unsaturated bond and an n-octanol/water partition coefficient LogP of < 2.0, and a structural unit derived from a hydrophobic monomer (E) having only 1 ethylenically unsaturated bond and an n-octanol/water partition coefficient LogP of ≥ 2.0.