Crosslinked Polymer Binder for High-Capacity Battery Electrodes
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Solution Overview
Problem
Current binders for nonaqueous electrolyte secondary battery electrodes lack sufficient binding ability and flex resistance, especially when using active materials with high capacity or thickened electrode mixture layers, which affects the durability and cycle characteristics of lithium-ion secondary batteries, particularly for vehicle-mounted applications.
Innovation Solution
A binder comprising a crosslinked polymer or salt with a carboxyl group, containing a structural unit derived from ethylenically unsaturated carboxylic acid monomers and a nonionic ethylenically unsaturated monomer with a carbon atom number of 6 or more, which exhibits excellent binding ability and dispersion stability when neutralized and dispersed in a saline solution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional binders are used for high-capacity active materials or thickened electrode mixture layers, then energy density is improved, but binding ability and flex resistance deteriorate
Solution Approach 1:
The patent changes the chemical parameters of the binder by introducing a crosslinked structure with specific functional groups (carboxyl, hydroxyl, amine) and controlling the molecular weight and composition ratios. This allows the binder to maintain strong binding ability while supporting high-capacity active materials and thickened electrode layers, thus resolving the contradiction between energy density and binding strength
Solution Approach 2:
The patent creates a composite binder system by crosslinking multiple polymer components together. The crosslinked network combines the advantages of different polymer chains, providing both the mechanical strength needed for flex resistance and the chemical functionality for strong binding to active materials, thereby enabling high energy density without sacrificing binding ability
2Quantity of substance
If conventional binders are used for high-capacity active materials or thickened electrode mixture layers, then energy density is improved, but cycle characteristics deteriorate
Solution Approach 1:
The patent modifies the binder's structural parameters through crosslinking, creating a more stable three-dimensional network that resists degradation during charge-discharge cycles. The specific functional groups and molecular weight control ensure the binder maintains its binding strength and structural integrity over repeated cycling, thus improving cycle characteristics while supporting high energy density
Solution Approach 2:
The crosslinked binder structure acts as a pre-established protective network that cushions and absorbs the mechanical stress and volume changes experienced by high-capacity active materials during cycling. This beforehand cushioning prevents electrode breakdown and maintains structural integrity throughout the battery's operational life, resolving the contradiction between energy density and cycle reliability
3Ease of manufacture
If aqueous binders are used for carbon-based active materials, then environmental protection and cost reduction are achieved, but dispersion stability deteriorates
Solution Approach 1:
The patent changes the surface chemical parameters of the aqueous binder through crosslinking and functional group introduction, enhancing its affinity and interaction with carbon-based active materials. This improved chemical compatibility ensures stable dispersion and uniform distribution of carbon particles in the aqueous medium, resolving the contradiction between environmental-friendly aqueous formulation and dispersion stability
4Reliability
If binder with high binding ability is used to prevent electrode mixture layer breakdown, then durability is improved, but flex resistance deteriorates
Solution Approach 1:
The patent optimizes the molecular weight and crosslinking density parameters of the binder to achieve a balance between binding strength and flexibility. The controlled crosslinking creates a network that is strong enough to prevent electrode breakdown but sufficiently flexible to maintain flex resistance, thus resolving the contradiction between durability and flexibility
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 a nonaqueous electrolyte secondary battery electrode with enhanced binding ability, flex resistance, and uniformity, preventing detachment during high-rate charging and discharging cycles, and improving the overall durability and cycle characteristics of the battery.
Implementation Method 1
a binder having high binding ability which can prevent deteriorations caused by the charge-discharge cycle, such as a breakdown of the electrode mixture layer and exfoliation of the electrode mixture layer from the collector
Implementation Method 2
a binder having high binding ability which can prevent deteriorations caused by the charge-discharge cycle
Data Source
AI summary
A binder for a nonaqueous electrolyte secondary battery electrode, containing a crosslinked polymer or salt thereof having a carboxyl group and a use thereof, and a method of manufacturing the polymer or salt. The polymer has a structural unit derived from an ethylenically unsaturated carboxylic acid monomer in an amount of 50 to 99 mass % of total structural units and a structural unit derived from a nonionic ethylenically unsaturated monomer in an amount of 1 to 50 mass % of the total structural units, the monomer is a compound having a substituent with a carbon atom number of 6 or more, and a particle diameter of the crosslinked polymer is 0.1 to 7.0 μm in a volume-based median diameter when the crosslinked polymer is neutralized to a neutralization degree of 80 to 100 mol %, subjected to water swelling in water, and then dispersed in a 1 mass % NaCl aqueous solution.