Dual-Binder Silicon-Graphite Negative Electrode for Cycle Retention
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Solution Overview
Problem
Existing electricity storage devices using silicon-containing graphite particles as negative electrode active material experience significant capacity decrease after charge-discharge cycles.
Innovation Solution
A negative electrode comprising silicon-containing graphite particles with voids and silicon-containing particles, combined with a first binder (styrene butadiene rubber with a glass-transition temperature of 1°C or higher) and a second binder (styrene butadiene rubber with a lower glass-transition temperature) to enhance adhesion and prevent binder penetration into voids, thereby stabilizing the electrode structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-containing graphite particles are used as negative electrode active material, then high capacity is achieved, but capacity decrease occurs after charge-discharge cycles
Solution Approach 1:
The negative electrode active material is segmented into a composite structure consisting of graphite particles containing voids, with silicon-containing particles disposed within those voids. This segmentation allows the graphite to provide structural stability while the silicon particles contribute high capacity, and the voids accommodate volume expansion during cycling, thereby resolving the contradiction between achieving high capacity and maintaining capacity retention.
Solution Approach 2:
The invention uses a composite material system combining graphite particles, silicon-containing particles, and a dual-binder system (first binder with glass-transition temperature of 1°C or higher, and second binder with glass-transition temperature of lower than 1°C). This composite structure leverages the complementary properties of each component: graphite provides stability, silicon provides high capacity, and the dual-binder system provides optimized adhesion and void filling, collectively resolving the capacity retention issue while maintaining high capacity.
2Strength
If binder is used to hold particles together, then electrode structure is maintained, but binder penetrates into voids of graphite particles
Solution Approach 1:
The invention applies local quality by using two different binders with distinct glass-transition temperatures in different locations and functions. The first binder (with glass-transition temperature of 1°C or higher) primarily adheres to the outer surfaces of graphite and silicon particles to provide strong adhesion. The second binder (with glass-transition temperature of lower than 1°C) specifically fills the voids within graphite particles, having lower penetration tendency. This spatial differentiation of binder properties resolves the contradiction between achieving strong adhesion and preventing void penetration.
Solution Approach 2:
The invention changes the parameter of glass-transition temperature to differentiate binder behavior. By selecting binders with significantly different glass-transition temperatures (first binder ≥1°C, second binder <1°C), the patent optimizes their respective properties: the higher glass-transition temperature binder provides stronger adhesion at operating temperatures, while the lower glass-transition temperature binder remains more flexible and less prone to penetrating into the voids, thus resolving the contradiction between adhesion strength and penetration resistance.
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 configuration effectively suppresses capacity decrease and maintains high energy density by improving adhesion and conductivity, reducing binder penetration, and enhancing the electrode's structural integrity during charge-discharge cycles.
Implementation Method 1
a first binder, and a second binder... improve adhesion... enhancing the electrode's structural integrity
Data Source
AI summary
Provided is a technology that can suppress the capacity decrease after charge-discharge cycles in an electricity storage device containing silicon-containing graphite particles as a negative electrode active material. A negative electrode disclosed herein includes a negative electrode active material composed of silicon-containing graphite particles, a first binder, and a second binder. The silicon-containing graphite particles include graphite particles with voids and silicon-containing particles disposed in the voids. The first binder is styrene butadiene rubber with a glass-transition temperature of 1° C. or higher. The second binder is styrene butadiene rubber with a glass-transition temperature of lower than 1° C.