Silicon Negative Electrode Material With Cationic Polymer Adhesion
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Solution Overview
Problem
Conventional negative electrode active materials containing silicon and fluorine-based polymers suffer from electrostatic repulsion due to similar surface charges, leading to poor adhesion and deterioration of cycle characteristics in solid-state batteries.
Innovation Solution
Incorporating a cationic polymer with the silicon material in the primary particles to suppress electrostatic repulsion and enhance adhesion, using materials like poly(diallyldimethylammonium chloride (PDADMAC) and fluorine-based polymers such as PVdF-HFP to improve the adhesion between the particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If granulated particles containing silicon material and fluorine-based polymer are used as negative electrode active material, then volumetric expansion/contraction during charging/discharging is suppressed, but electrostatic repulsion between negatively charged silicon and fluorine-based polymer causes poor adhesion and deteriorated cycle characteristics
Solution Approach 1:
A cationic polymer is introduced as an intermediary substance between the silicon material and fluorine-based polymer. The cationic polymer's positive charge neutralizes the negative surface charges of both silicon and fluorine-based polymer, eliminating electrostatic repulsion and enabling strong adhesion. This mediator resolves the contradiction by allowing the fluorine-based polymer to provide volumetric stability while the cationic polymer ensures good adhesion and cycle characteristics through charge neutralization.
Solution Approach 2:
The invention changes the charge parameter of the polymer component from negative (fluorine-based) to positive (cationic). By selecting a cationic polymer with positive charge, the electrostatic interaction between polymer and silicon surface is fundamentally altered from repulsive to attractive, resolving the adhesion problem while maintaining the volumetric stability provided by the fluorine-based polymer structure.
2Stability of the object's composition
If fluorine-based polymer is used as binder resin with silicon material, then volumetric expansion/contraction is suppressed, but similar negative surface charges cause electrostatic repulsion and low adhesion
Solution Approach 1:
The cationic polymer serves as a mediator that interacts with both the silicon material surface and the fluorine-based polymer. Its positive charge creates electrostatic attraction to the negatively charged silicon surface, forming a strong adhesive interface, while also being compatible with the fluorine-based polymer matrix, thus resolving the adhesion problem without compromising volumetric stability.
Solution Approach 2:
The invention creates a composite material system consisting of three components: silicon material, cationic polymer, and fluorine-based polymer. This composite structure combines the volumetric stability of fluorine-based polymer with the adhesion-promoting properties of cationic polymer, achieving both high adhesion strength and volumetric stability simultaneously.
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 use of cationic polymers improves the adhesion between silicon and fluorine-based polymers, thereby enhancing the cycle characteristics of solid-state batteries by maintaining discharge capacity over multiple cycles.
Implementation Method 1
the silicon and the fluorine-based polymer surface charges are respectively charged negatively, and therefore, it is easy for the primary particles and the fluorine-based polymer to electrostatically repel one another
Implementation Method 2
the adhesion between the primary particles and the fluorine-based polymer is low
Data Source
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AI summary
A negative electrode active material, including primary particles containing at least a silicon material and a cationic polymer, and a fluorine-based polymer.