Negative Electrode Binder Composition for Capacity Retention
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Solution Overview
Problem
Existing energy storage devices face issues with negative active material layer falling off and decreased capacity retention ratio after charge-discharge cycles, particularly in lithium ion secondary batteries.
Innovation Solution
Incorporating negative active material particles with an average circularity of 0.60 or less and a cellulose derivative with a peak top molecular weight of 2,800,000 or more into the negative electrode, which enhances adhesion and conductivity, thereby suppressing layer falling and retention ratio decline.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional binders with glass-transition temperature of 20°C to 40°C are used and processing is performed at temperatures higher by 10°C or more, then productivity is improved, but the negative active material layer still falls off
Solution Approach 1:
The invention changes the chemical composition parameters of the binder from conventional polymers to a specific cellulose derivative with defined molecular weight (2,800,000 or more). This parameter change enables the binder to achieve both high adhesion strength preventing layer fall-off and compatibility with high-temperature processing for improved productivity.
Solution Approach 2:
The invention uses a composite system combining negative active material particles with specific cellulose derivative binder. The cellulose derivative forms a composite structure that provides both mechanical adhesion strength and electrochemical compatibility, resolving the contradiction between productivity and reliability.
2Ease of manufacture
If conventional binders are used in the negative electrode, then manufacturing is simplified, but capacity retention ratio decreases after charge-discharge cycles
Solution Approach 1:
The invention changes the molecular weight parameter of the binder to a specific high molecular weight cellulose derivative (2,800,000 or more). This parameter change provides exceptional adhesion strength that maintains capacity retention ratio after charge-discharge cycles while keeping the manufacturing process simple.
3Reliability
If the negative active material layer adhesion is improved using conventional methods, then layer falling off is suppressed, but the structure becomes more complex
Solution Approach 1:
The invention extracts and eliminates the need for complex multi-component binder systems by using a single cellulose derivative that inherently provides both adhesion and electrochemical stability. This simplifies the overall electrode structure while maintaining reliability.
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 solution effectively prevents negative active material layer detachment and maintains capacity retention, improving the performance of energy storage devices.
Implementation Method 1
the negative active material layer contains negative active material particles and a cellulose derivative... suppress falling off of the negative active material layer
Data Source
AI summary
An energy storage device according to one aspect of the present invention includes: a negative electrode including a negative active material layer; and a positive electrode, in which the negative active material layer contains negative active material particles and a cellulose derivative, an average circularity of the negative active material particles is 0.60 or less, and a peak top molecular weight of the cellulose derivative is 2,800,000 or more.