Aqueous Binder for Lithium-Ion Battery Electrodes
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Solution Overview
Problem
Existing binders for lithium-ion secondary batteries face issues with oxidative degradation under positive electrode environments, high temperature conditions, and high voltage, leading to deteriorated battery properties and capacity after charge/discharge cycles, while also having high environmental and recovery costs.
Innovation Solution
A water-based binder comprising structural units derived from hydroxyl group-containing (meth)acrylate monomers, polyfunctional (meth)acrylate monomers, and reactive surface active agents, which enhances bondability, oxidation resistance, and dispersibility, and is suitable for high-temperature and high-voltage applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If SBR-based aqueous binder is used for negative electrode, then environmental load is reduced and cost is lowered, but oxidative degradation occurs under positive electrode environment
Solution Approach 1:
The invention changes the chemical composition parameters of the binder by using copolymers with specific functional groups (carboxylic acid, hydroxyl, amine) in controlled amounts. This allows the binder to maintain aqueous compatibility while gaining oxidation resistance through specific chemical interactions with the positive electrode environment.
Solution Approach 2:
The invention creates a composite binder system by combining multiple polymer components with different functions: one component provides aqueous dispersibility and bonding, while another component provides oxidation resistance. This composite approach allows simultaneous achievement of environmental friendliness and reliability.
2Reliability
If polyvinylidene fluoride or polytetrafluoroethylene binder is used for positive electrode, then oxidation resistance is improved, but environmental load increases and cost increases due to N-methylpyrrolidone solvent
Solution Approach 1:
The invention changes the solvent parameter from organic N-methylpyrrolidone to water, and adjusts the polymer composition to include hydrophilic groups. This allows the binder to maintain oxidation resistance while being compatible with aqueous processing, thereby reducing environmental load.
Solution Approach 2:
The invention introduces hydrophilic functional groups (carboxylic acid, hydroxyl, amine) as intermediaries that enable the fluorinated polymer to interact with water. These functional groups act as bridges between the hydrophobic fluorinated backbone and the aqueous environment, allowing water-based processing while maintaining the oxidation-resistant properties of the fluorinated structure.
3Strength
If existing copolymer binders are used, then bondability is improved, but capacity deteriorates under high temperature and high voltage conditions
Solution Approach 1:
The invention applies local quality by distributing different functional groups at specific locations within the binder structure. Hydrophobic segments provide strong bonding to active materials, while hydrophilic functional groups provide oxidation resistance and thermal stability. This spatial distribution of properties allows simultaneous achievement of bondability and high-temperature capacity retention.
Solution Approach 2:
The invention uses composite polymer structures combining segments with different functions: bonding segments for adhesion to active materials and electrode substrates, and protective segments with oxidation-resistant functional groups for stability under high voltage and temperature. This composite structure resolves the contradiction between bondability and capacity retention.
Data Source
AI summary
Provided is a binder for battery electrodes which includes a polymer including: structural units (1) derived from a (meth)acrylate monomer (A) having a hydroxyl group; structural units (2) derived from a polyfunctional (meth)acrylate monomer (B); and structural units (3) derived from a reactive surfactant (C). This binder is used to prepare electrodes, and produce batteries such as lithium ion secondary batteries. Provided are: an aqueous binder which has a low environmental impact, exhibits excellent binding properties, and, notably, does not cause oxidation degradation under an electrode environment; and an electrode and a battery which use said binder.