Silicon-Anode Binder Polymer for Cycle Stability and Fast Discharge
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Solution Overview
Problem
Conventional binder compositions for power storage devices with silicon-based negative electrode active materials fail to improve charge-discharge cycle characteristics and fast discharge capacity retention rates, particularly when subjected to high current charging and discharging.
Innovation Solution
A polymer composition containing a specific constitutional unit represented by formula (I), with a content of more than 95% by mass, enhances adhesion and reduces expansion of the negative electrode, improving charge-discharge cycle characteristics and fast discharge capacity retention rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional binder compositions are used with silicon-based negative electrode active materials, then the electrode structure is maintained, but charge-discharge cycle characteristics deteriorate due to significant volume change during charge and discharge
Solution Approach 1:
The patent introduces a polymer binder as an intermediary substance between the silicon-based active material particles and the current collector. This polymer binder mediates the mechanical stress and volume changes, maintaining adhesion and preventing electrode degradation during charge-discharge cycles.
Solution Approach 2:
The patent modifies the chemical composition parameters of the binder by incorporating specific functional groups (carboxylic acid groups, hydroxyl groups, or amine groups) with controlled content ratios. These parameter changes in the binder's chemical structure enable it to effectively accommodate silicon's volume expansion and contraction while maintaining electrode integrity.
2Productivity
If conventional binder compositions are used, then the electrode maintains basic structure, but fast discharge capacity retention rate deteriorates under high current charging and discharging
Solution Approach 1:
The patent optimizes the molecular weight parameters of the polymer binder within specific ranges (weight-average molecular weight: 10,000-1,000,000, number-average molecular weight: 1,000-100,000) and controls the functional group content ratios. These parameter changes enhance the binder's mechanical properties and adhesion strength, enabling the electrode to maintain structural integrity and electrical contact under high current conditions, thus improving fast discharge capacity retention.
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 polymer composition improves the adhesion between the negative electrode layer and the current collector, reduces cracking and crushing of the silicon-based negative electrode active material, and enhances the fast discharge capacity retention rate, enabling better performance in power storage devices.
Implementation Method 1
a binder is added to the composite layer... to prevent the composite layer from peeling off the metal foil
Data Source
AI summary
An aspect of the present disclosure relates to a polymer for a power storage device. The polymer contains a constitutional unit represented by the following formula (I). The content of the constitutional unit of the formula (I) is more than 95% by mass. In the formula (I), R1 represents a hydrogen atom or a methyl group, R2 represents a hydrogen atom, a hydrocarbon group having 1 to 4 carbon atoms, or a straight- or branched-chain hydrocarbon group having 1 to 4 carbon atoms and 1 to 3 hydroxyl groups, and R3 represents a straight- or branched-chain hydrocarbon group having 1 to 4 carbon atoms and 1 to 3 hydroxyl groups.