Positive Electrode Binder Blend for Adhesion and Slurry Dispersibility
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Solution Overview
Problem
Lithium-sulfur batteries face issues with instability of lithium metal, low conductivity of positive electrodes, sulfur sublimation, and material loss during charge and discharge, limiting their application due to poor adhesion and cycle stability.
Innovation Solution
A binder comprising two or more types of lithium-substituted polyacrylic acids with different molecular weights is used to enhance the adhesion and processability of positive electrodes, improving the stability and cycle performance of lithium-sulfur batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If styrene butadiene rubber/carboxymethyl cellulose (SBR/CMC) is used as a binder, then adhesion is improved, but dispersibility is reduced when thickener is not present
Solution Approach 1:
The invention extracts and removes the thickener (carboxymethyl cellulose) from the traditional SBR/CMC binder system, replacing it with a polyacrylic acid-based binder that provides both adhesion and dispersibility without requiring a separate thickening agent. This eliminates the need for CMC while maintaining or improving both adhesion and dispersibility properties.
Solution Approach 2:
The invention uses a composite binder system comprising polyacrylic acid and its derivatives (including crosslinked polyacrylic acid) that combines the adhesive properties of polyacrylic acid with the binding characteristics of crosslinked structures, creating a multi-functional binder that replaces both SBR and CMC functionalities in a single material system.
2Ease of manufacture
If traditional binders are used, then initial electrode formation is achieved, but long-term stability decreases due to positive electrode deterioration during charge and discharge
Solution Approach 1:
The invention applies preliminary action by using polyacrylic acid that has been pre-crosslinked or modified before electrode fabrication. This pre-treatment creates a more stable binder structure that resists deterioration during subsequent charge and discharge cycles, improving long-term stability while maintaining ease of electrode formation.
Solution Approach 2:
The invention changes the chemical parameters of the binder by using polyacrylic acid with specific molecular weights, degrees of crosslinking, and substitution levels. These parameter changes create a binder with enhanced chemical stability and resistance to electrochemical degradation, thereby improving long-term battery stability without compromising electrode formation capability.
Data Source
AI summary
A binder for preparing a positive electrode of a lithium secondary battery, and a method for preparing a positive electrode using the same. The binder includes two or more different lithium-substituted polyacrylic acids with different molecular weights. The lithium-substituted polyacrylic acids include two different lithium-substituted polyacrylic acids differing in weight average molecular weight by 500,000 or more from each other.