Polyamide-imide Binder for Silicon Anode Stability
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Solution Overview
Problem
Lithium ion secondary batteries using silicon materials in the negative electrode face issues with charge and discharge efficiency and cycle characteristics due to expansion and contraction, leading to mechanical damage and peeling of active materials from the current collector.
Innovation Solution
A binder composition comprising a polyamide-imide with specific repeating units, such as those derived from tricarboxylic acids and diamines, is used to enhance the mechanical strength and stability of the electrode, improving the charge and discharge efficiency and cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon materials are used in the negative electrode to enhance energy density, then the battery capacity increases, but the active material layer breaks and active materials peel from the current collector due to expansion and contraction during charge and discharge
Solution Approach 1:
The invention changes the chemical composition parameters of the binder by specifying precise proportions of polyacrylic acid (0.1-5 mass%) and carboxymethyl cellulose (0.1-5 mass%) relative to silicon oxide, creating a binder system that adapts to the expansion-contraction behavior of silicon-based active materials during charge-discharge cycles
Solution Approach 2:
The invention uses a composite binder system combining polyacrylic acid and carboxymethyl cellulose with silicon oxide, where the composite structure provides both mechanical strength to prevent layer breakage and adhesive properties to prevent peeling from the current collector, thereby maintaining reliability while enabling high capacity
2Stability of the object's composition
If polyamide-imide resin is used as a binder to reduce mechanical damage, then the electrode structure stability improves, but charge and discharge efficiency remains insufficient
Solution Approach 1:
The invention changes the binder composition parameters by using polyacrylic acid and carboxymethyl cellulose instead of polyamide-imide, with specific mass% ratios that optimize both structural stability and ionic conductivity for improved charge-discharge efficiency
Solution Approach 2:
The invention applies different functional properties to different components of the binder system: polyacrylic acid provides adhesive strength at the interface with the current collector, while carboxnymethyl cellulose provides structural stability within the active material layer, creating localized quality optimization throughout the electrode structure
Data Source
AI summary
A purpose of the present invention is to provide a binder composition for a secondary battery which improves the charge and discharge efficiency and the cycle characteristics of a battery. The binder composition for a secondary battery of the present invention is characterized by comprising a polyamide-imide comprising a repeating unit represented by chemical formula (1) or a precursor thereof,wherein A is a trivalent group obtained by removing carboxyl groups from a tricarboxylic acid, B is a divalent group obtained by removing amino groups from a diamine, and at least one of A and B is an aliphatic group.