Cross-linked Polyacrylic Acid Binder for Silicon Anodes
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Solution Overview
Problem
Lithium ion cells using silicon as an active material face issues with large volume changes during charge-discharge cycles, leading to electrode structure destruction and reduced cycle characteristics and self-discharge, which existing binders fail to adequately address.
Innovation Solution
A cross-linked polyacrylic acid binder is used, cross-linked by specific cross-linking agents, to maintain electrode structure integrity and enhance capacity retention in lithium cells with silicon-based active materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If silicon is used as an active material to increase electric capacity, then higher electric capacity is achieved, but large volume change occurs during charge-discharge leading to electrode structure destruction
Solution Approach 1:
The patent changes the physical and chemical parameters of the binder by using cross-linked polyacrylic acid instead of conventional binders. The cross-linking creates a three-dimensional network structure with enhanced mechanical strength and flexibility, allowing the binder to withstand the large volume changes of silicon during lithiation and delithiation while maintaining electrode structure integrity.
Solution Approach 2:
The patent creates a composite binder system by cross-linking polyacrylic acid with appropriate cross-linking agents. This composite structure combines the flexibility and adhesion properties of polyacrylic acid with the structural stability provided by the cross-linked network, enabling the binder to accommodate silicon's volume expansion and contraction without breaking.
2Ease of manufacture
If conventional binders are used with silicon active material, then electrode assembly is simplified, but capacity retention rate deteriorates due to electrode structure destruction
Solution Approach 1:
The patent modifies the binder's molecular structure through cross-linking, transforming polyacrylic acid into a three-dimensional network. This structural parameter change enhances the binder's ability to maintain electrode integrity during repeated charge-discharge cycles, significantly improving capacity retention while keeping the manufacturing process relatively simple.
3Use of energy by moving object
If silicon is used instead of carbon-based material, then higher electric capacity is achieved, but self-discharge increases
Solution Approach 1:
The cross-linked polyacrylic acid binder acts as an intermediary between the silicon active material and the electrolyte. It forms a stable interface that prevents direct harmful interactions between silicon and electrolyte components, reducing parasitic reactions and self-discharge while allowing efficient lithium ion transport.
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 cross-linked polyacrylic acid binder effectively retains capacity over long periods, exhibits high coulombic efficiency, and stabilizes the electrode structure, even during repeated charge-discharge cycles, improving the performance of silicon-based lithium cells.
Implementation Method 1
a cross-linked polymer, among them, a polymer cross-linked the polyacrylic acid by a specific cross-linking agent
Data Source
AI summary
It is an object of the present invention to provide an electrode capable of maintaining superior capacity retention without destruction of an electrode structure, even in the case of using an active material including silicon.The present invention relates to “a binder for a lithium cell, the binder comprising polyacrylic acid cross-liked by a cross-linking agent selected from the compounds described in the general formulae [1] to [13] and the polymer described in the general formula [14] (provided that the one which includes a functional group-containing vinylidene fluoride-based polymer is excluded)”; a “composition for producing an electrode of a lithium cell, the composition comprising 1) an active material containing silicon, 2) a conductive assistant and 3) a cross-linked-type polyacrylic acid (provided that the one containing a functional group-containing vinylidene fluoride-based polymer is excluded)”; and an “electrode for a lithium cell, the electrode comprising 1) an active material containing silicon, 2) a conductive assistant, 3) a cross-linked-type polyacrylic acid, and 4) a current collector (provided that the one containing a functional group-containing vinylidene fluoride-based polymer is excluded)”.