Secondary Battery Electrode Binder for Low-Viscosity High-Solid Slurries
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Solution Overview
Problem
Existing secondary battery binders face challenges in achieving high binding strength while maintaining low electrode slurry viscosity, especially when the active material concentration is high, leading to issues with coating properties and durability.
Innovation Solution
A secondary battery electrode binder comprising a carboxyl group-containing polymer with specific structural units, including a monomer represented by general formula (1) and an ethylenically unsaturated carboxylic acid monomer, allows for improved binding ability and reduced slurry viscosity even at high active material concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the concentration of active material in the electrode mixture layer composition is increased to improve drying efficiency and productivity, then productivity is improved, but the viscosity of the electrode slurry increases making it difficult to ensure favorable coating properties
Solution Approach 1:
The invention changes the chemical composition parameters of the binder by incorporating specific structural units (acrylic acid polymer with 5-20 mass% carboxyl groups and 80-95 mass% hydroxyl groups) to achieve low viscosity even at high active material concentrations (90 mass% or more), thereby maintaining good coating properties while improving productivity
Solution Approach 2:
The invention uses a composite binder system combining acrylic acid polymer with specific functional groups (carboxyl and hydroxyl) to create a material that provides both low viscosity for good coating properties and high binding strength for high active material concentration formulations
2Strength
If fine crosslinking is performed in acrylic acid polymer binders to improve binding ability, then binding ability is improved, but expansion in water increases causing great increase in viscosity making it difficult to increase active material concentration
Solution Approach 1:
The invention optimizes the crosslinking degree parameter to maintain low expansion in water (4-10 times) while preserving adequate binding ability, and controls the carboxyl group content (5-20 mass%) to balance binding strength with low viscosity characteristics that enable high active material concentration formulations
3Strength
If fine crosslinking is performed in acrylic acid polymer binders to improve binding ability, then binding ability is improved, but viscosity increases greatly even with a small amount of binder
Solution Approach 1:
The invention carefully controls the crosslinking degree and carboxyl group content parameters to achieve a balance where binding ability is sufficient while viscosity remains low, enabling the formulation to maintain good processability even with high active material concentration and adequate binder content
Data Source
AI summary
A secondary battery electrode binder that exhibits superior binding capacity. The present invention also provides a secondary battery electrode mixture layer composition, a secondary battery electrode, and a secondary battery that are obtained using the binder. The present invention relates to a secondary battery electrode binder that contains a carboxyl-group-containing polymer or a salt of a carboxyl-group-containing polymer. The carboxyl-group-containing polymer or salt of a carboxyl-group-containing polymer includes structural units that are derived from monomers that are represented by general formula (1) and structural units that are derived from ethylenic unsaturated carboxylic acid monomers that are different from general formula (1). The structural units derived from monomers that are represented by general formula (1) are 0.1-20 mass % of the total structural units of the carboxyl-group-containing polymer or salt of a carboxyl-group-containing polymer.