Copolymer Binder for Nonaqueous Battery Electrodes
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Solution Overview
Problem
Nonaqueous batteries face challenges with high internal resistance and insufficient binding properties between active materials and current collectors, leading to reduced capacity and increased production complexity, particularly with existing binders like PVDF and SBR-based systems.
Innovation Solution
A copolymer binder system is developed, comprising a monomer mixture with a specific ratio of N-vinylformamide or N-vinylacetamide and a (meth)acrylate salt, along with an ethylenically unsaturated monomer, which is polymerized in an aqueous medium to achieve improved binding properties and reduced internal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PVDF-based binder using NMP is used, then binding properties between active materials and current collector are improved, but binder amount required increases and capacity decreases
Solution Approach 1:
The invention changes the chemical composition parameters of the binder by using a copolymer containing N-vinylformamide or N-vinylacetamide units combined with polyacrylic acid or polyacrylamide, replacing the conventional PVDF-NMP system. This parameter change in binder chemistry enables achieving adequate binding properties with reduced binder quantity, thereby increasing the active material content and battery capacity.
2Reliability
If PVDF-based binder using NMP is used, then binding properties between active materials and current collector are improved, but manufacturing cost and working environment maintenance become problematic
Solution Approach 1:
The invention replaces the expensive and environmentally problematic NMP solvent with water as the dispersion medium. The copolymer binder system is designed to be water-dispersible, eliminating the need for costly organic solvent recovery systems and reducing environmental maintenance requirements, while maintaining adequate binding properties.
3Ease of manufacture
If SBR type water dispersion binder is used, then manufacturing cost decreases and working environment maintenance is improved, but binding properties between active materials and current collector are insufficient
Solution Approach 1:
The invention creates a composite binder system combining N-vinylformamide or N-vinylacetamide copolymer with polyacrylic acid or polyacrylamide. This composite structure leverages the water dispersibility and cost advantages of acrylic polymers while the N-vinylformamide/N-vinylacetamide component provides enhanced binding properties, achieving both low cost and high reliability.
4Quantity of substance
If smaller amount of binder is used to increase capacity, then battery capacity and output are improved, but active material peeling from current collector occurs
Solution Approach 1:
The invention changes the functional parameters of the binder by incorporating N-vinylformamide or N-vinylacetamide units which provide enhanced adhesion properties. This allows reducing the binder quantity from typical high levels down to 1-10 wt% while maintaining sufficient binding strength to prevent active material peeling, thereby increasing battery capacity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The copolymer binder system effectively reduces internal resistance while maintaining sufficient binding properties, enabling higher capacity and output in nonaqueous batteries with improved manufacturing efficiency.
Implementation Method 1
The binder plays a role of bonding the active materials to each other and bonding the active material and the current collector in the positive electrode or the negative electrode to prevent peeling of the active material from the current collector
Implementation Method 2
The copolymer binder system effectively reduces internal resistance while maintaining sufficient binding properties, enabling higher capacity and output in nonaqueous batteries
Data Source
AI summary
A copolymer for binders, which is capable of reducing the internal resistance of a battery, while ensuring sufficient binding properties between active materials and between an active material and a collector in a nonaqueous battery electrode; a composition for binders; a slurry for nonaqueous battery electrodes; a nonaqueous battery electrode; and a nonaqueous battery. This copolymer for binders is a copolymer for binders (P) of a monomer mixture (M) that contains at least a monomer (A) represented by general formula (1) and a (meth)acrylate salt monomer (B); and an amount of structure derived from the monomer (A) based on the copolymer for binders (P) is set to 0.5 to 20.0% by mass. (In the formula, each of R1 and R2 independently represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms.)