Lithium Battery Negative Electrode Binder Composition for Crack Prevention
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Solution Overview
Problem
Rechargeable lithium batteries face issues with weak adherence of the coating layer to the current collector, leading to cracks and impaired electrolyte impregnation, which deteriorate cycle-life and performance.
Innovation Solution
A negative electrode with a thick-film structure is developed, using a binder composition of carboxymethyl cellulose, polyvinyl alcohol, and styrene-butadiene rubber, with specific repeating units and weight ratios, to enhance flexibility, adherence, and impregnation, preventing cracks and improving cycle-life characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the binder amount is increased to improve adherence of the coating layer to the current collector, then adherence is improved, but electrolyte impregnation is impaired
Solution Approach 1:
The patent changes the chemical composition parameters of the binder by incorporating carboxymethyl cellulose with specific repeating units (n1≥600, n2≥0) and controlling the substitution degree (0.3-1.7), which modifies the binder's properties to achieve both strong adherence and good electrolyte impregnation without increasing binder amount
Solution Approach 2:
The patent uses a composite binder system combining carboxymethyl cellulose (with specific repeating units), styrene-butadiene rubber, and polyvinyl alcohol, where each component contributes different properties: CMC provides adherence and flexibility, SBR provides elasticity, and PVA enhances binding, achieving both strong adherence and good electrolyte impregnation
2Quantity of substance
If the coating layer is made thicker to increase capacity, then capacity is improved, but cracks form due to weak adherence
Solution Approach 1:
The patent changes the binder's chemical structure parameters by specifying carboxymethyl cellulose with n1≥600 and n2≥0, and substitution degree of 0.3-1.7, which enhances the coating layer's flexibility and crack resistance, allowing thicker coatings to be applied without forming cracks
Solution Approach 2:
The patent creates a flexible coating layer by using carboxymethyl cellulose with specific repeating units and substitution degree, which provides flexibility to the thick-film electrode, preventing crack formation while maintaining high capacity
3Strength
If the binder amount is increased to prevent cracks, then crack resistance is improved, but electrolyte impregnation is impaired
Solution Approach 1:
The patent changes the binder's chemical composition by incorporating carboxymethyl cellulose with specific repeating units (n1≥600, n2≥0) and controlling substitution degree (0.3-1.7), which provides crack resistance without requiring increased binder amount, thus maintaining good electrolyte impregnation
Solution Approach 2:
The patent uses a composite binder system where carboxymethyl cellulose provides crack resistance through its specific molecular structure, while the combination with SBR and PVA maintains porosity and electrolyte access, achieving both crack prevention and good impregnation without increasing total binder amount
Data Source
AI summary
Disclosed is a negative electrode for a rechargeable lithium battery that includes a negative active material and a binder, wherein the binder includes carboxymethyl cellulose, polyvinyl alcohol, and a styrene-butadiene rubber, and a rechargeable lithium battery including the same.