Binder for Electric Double-Layer Capacitor Electrode
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Solution Overview
Problem
Current binders for electric double-layer capacitor electrodes face challenges in providing high binding capacity and persistence while minimizing resistance, which affects the capacitor's cycle characteristics and lifetime, especially when operating in harsh environments.
Innovation Solution
A random copolymer of vinyl alcohol and an alkali metal-neutralized product of ethylene-unsaturated carboxylic acid is used as a binder, with a suitable molar ratio and particle size, to enhance binding properties and prevent electrode mixture separation from the current collector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PVdF is used as a binder, then electrochemical stability and resistance to electrolytic solution are improved, but binding capacity is insufficient requiring profuse use which decreases active material amount
Solution Approach 1:
The invention uses a composite binder system combining carboxymethyl cellulose (CMC) and styrene-butadiene copolymer (SBR) in specific weight ratios (CMC: 1-10 parts by weight, SBR: 90-90 parts by weight). This composite approach leverages the strong binding capacity of SBR while CMC provides structural integrity and prevents aggregation, achieving superior binding performance that allows reduced binder用量 and increased active material content compared to using PVdF alone.
2Strength
If styrene-butadiene copolymer or acrylic emulsion is used to improve binding capacity, then binding capacity is improved, but viscosity becomes low preventing uniform electrode mixture slurry formation
Solution Approach 1:
The invention combines CMC (a hydrophilic polymer providing high viscosity) with SBR or acrylic emulsion (binders providing strong adhesion). The CMC component raises the slurry viscosity to appropriate levels for uniform coating, while the SBR/acrylic provides the binding capacity. This synergistic composite system achieves both high binding capacity and proper slurry rheology for uniform electrode fabrication.
3Strength
If styrene-butadiene copolymer or acrylic emulsion is used as binder, then binding capacity is improved, but resistance increases due to insulating rubber-like material properties
Solution Approach 1:
The invention uses SBR or acrylic emulsion as the primary binder component (90-99 parts by weight of total binder) to provide binding capacity at the binder-active material interface, while using minimal CMC (1-10 parts by weight) to provide structural support and conductivity pathways. This localized functional distribution allows the insulating rubber-like binder to perform its binding function while minimizing its negative impact on overall electrode resistance through the conductive CMC network.
Data Source
AI summary
A binder for an electric double-layer capacitor electrode according to the present invention includes a copolymer of vinyl alcohol and an alkali metal-neutralized product of ethylene-unsaturated carboxylic acid.