Lithium-Sulfur Electrode Binder Composition for Polysulfide Control
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Solution Overview
Problem
Existing lithium-sulfur batteries face challenges in maintaining high adhesion force while ensuring productivity and output performance due to the elution of lithium polysulfide, which degrades battery capacity and efficiency.
Innovation Solution
A binder composition comprising lithium-substituted polyacrylic acid, lithium-substituted carboxymethyl cellulose, and a colloid particle-type aqueous binder resin is used to enhance adhesion force and maintain productivity, with specific molecular weights and viscosities optimized for each resin to improve electrode stability and dispersibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If sulfur is supported in the pores of porous carbonaceous materials to prevent lithium polysulfide elution, then adhesion force is improved, but productivity and output performance deteriorate
Solution Approach 1:
The invention uses a composite binder system combining carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) in specific ratios. CMC provides strong adhesion to the porous carbonaceous material substrate through its carboxyl groups, while SBR contributes to flexibility and output performance. This composite approach allows simultaneous achievement of high adhesion force and maintained productivity without requiring excessive binder content.
Solution Approach 2:
The invention optimizes the molecular weight of CMC (specifically using low molecular weight CMC with viscosity of 10-1000 cP) and the ratio of CMC to SBR (specifically 3:7 to 7:3 by weight). These parameter changes enable the binder composition to achieve sufficient adhesion force with reduced binder content, thereby maintaining productivity and output performance.
2Strength
If sulfur is supported in the pores of porous carbonaceous materials to prevent lithium polysulfide elution, then adhesion force is improved, but output performance deteriorates
Solution Approach 1:
The composite binder system of CMC and SBR leverages the complementary properties of both materials. CMC provides strong adhesion and structural stability, while SBR contributes excellent flexibility, elasticity, and electrical conductivity. This combination ensures that the electrode maintains both strong adhesion and high output performance, as SBR's conductive properties facilitate electron transport while its flexibility accommodates volume changes during charge-discharge cycles.
Solution Approach 2:
The binder composition is designed to have different functional components distributed throughout the binder layer. CMC primarily provides adhesion to the substrate, while SBR is distributed to provide conductivity and flexibility throughout the electrode structure. This local differentiation of functions allows the electrode to simultaneously achieve strong adhesion and high output performance.
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 composition provides improved adhesion force and output performance, inhibiting lithium polysulfide elution and enhancing battery stability, thereby maintaining high capacity and efficiency.
Implementation Method 1
a binder composition for a secondary battery electrode, including a first binder resin, a second binder resin and a third binder resin, wherein the first binder resin is lithium-substituted polyacrylic acid, the second binder resin is lithium-substituted carboxymethyl cellulose
Implementation Method 2
the third binder resin is a colloid particle-type aqueous binder resin
Data Source
AI summary
Provided are a binder composition, a positive electrode for a lithium-sulfur battery and a lithium-sulfur secondary battery. The binder composition includes lithium-substituted polyacrylic acid, lithium-substituted carboxymethyl cellulose and a colloid particle-type aqueous binder resin and thus can provide improved adhesion force in an electrode while maintaining a high level of productivity and output performance.