Crosslinked Polymer Binder for Li-Ion Battery Electrodes
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Solution Overview
Problem
Current aqueous binders for lithium-ion secondary battery electrodes lack sufficient binding ability and dispersion stability, particularly at high-rate charging and discharging conditions, which affects the durability and cycle characteristics required for vehicle-mounted applications.
Innovation Solution
A binder comprising a crosslinked polymer or salt with a carboxyl group, having a specific particle diameter and degree of neutralization, is used to enhance binding ability and dispersion stability, comprising a structure derived from ethylenically unsaturated carboxylic acid monomers and a crosslinkable monomer, with a viscosity range that ensures effective adhesion and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If aqueous binders (SBR or CMC) are used for negative electrodes, then environmental protection and cost reduction are achieved, but binding ability and dispersion stability are insufficient for high-rate charging and vehicle-mounted applications
Solution Approach 1:
The patent changes the chemical parameters of the binder by introducing carboxyl groups and controlling the degree of neutralization (50-100%). This chemical modification enables the binder to achieve both low cost and high binding ability, resolving the contradiction between ease of manufacture and reliability
Solution Approach 2:
The patent creates a composite binder system combining crosslinked polymer structures with carboxyl groups and controlled neutralization degrees. This composite approach integrates the advantages of different material properties to achieve both cost-effectiveness and superior binding performance for high-rate charging applications
2Ease of manufacture
If aqueous binders are used for negative electrodes, then environmental protection is achieved, but dispersion stability on carbon-based materials is poor
Solution Approach 1:
The patent modifies the chemical parameters of the aqueous binder by incorporating carboxyl groups and controlling neutralization degree, which enhances the interaction between the binder and carbon-based materials. This parameter change improves dispersion stability while maintaining environmental protection benefits
Solution Approach 2:
The carboxyl groups in the binder act as intermediaries that improve the wettability and adhesion between aqueous media and carbon-based materials. This intermediary function resolves the contradiction between environmental protection and dispersion stability
3Quantity of substance
If high energy density is achieved by increasing electrode mixture layer thickness or using high-capacity active material, then cruising distance per charge is improved, but cycle characteristics are reduced
Solution Approach 1:
The patent changes the binder properties through carboxyl group incorporation and controlled neutralization, which enhances binding strength and flexibility. This enables the electrode to maintain good cycle characteristics even with high energy density designs involving thick electrode layers or high-capacity active materials
4Reliability
If strong binding ability is required to prevent electrode mixture layer breakdown during high-rate charging, then durability is improved, but the binder must have specific structural requirements that complicate manufacturing
Solution Approach 1:
The patent achieves strong binding ability by controlling specific parameters of the binder (carboxyl group content and neutralization degree) rather than through complex structural designs. This parameter-based approach maintains durability while avoiding excessive manufacturing complexity
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 binder provides electrodes with improved flex resistance, reduced detachment during high-rate charging, and enhanced durability, achieving stable and uniform mixture layers with excellent ion conductivity.
Implementation Method 1
a binder with strong binding ability is required in order to prevent breakdown of the electrode mixture layer, peeling from the collector
Implementation Method 2
when the crosslinked polymer is neutralized to a degree of a neutralization of 80 to 100 mol%, subjected to water swelling in water
Data Source
AI summary
Provided is a binder for a nonaqueous electrolyte secondary battery electrode. The binder contains a crosslinked polymer having a carboxyl group, or salt thereof, a use therefor, and a method for manufacturing a carboxyl group-containing crosslinked polymer or salt thereof for use in the binder. The crosslinked polymer contains a structural unit derived from an ethylenically unsaturated carboxylic acid monomer in the amount of 50 to 100 mass% of total structural units, and after the crosslinked polymer neutralized to a degree of a neutralization of 80 to 100 mol% has been subjected to water swelling in water and then dispersed in a 1 mass% NaCl aqueous solution, the particle diameter thereof is 0.1 to 7.0 µm in a volume-based median diameter.