Polyimide Binder Composition for Silicon Anode Adhesion
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Solution Overview
Problem
Conventional binders for lithium ion battery electrodes, such as PVDF and polyimide resin, suffer from poor adhesion to current collector bodies, leading to detachment of active materials and rapid deterioration of charge-discharge cycle characteristics, especially when silicon or silicon alloys are used as anode active substances, and inhibit the formation of a stable electrode interface (SEI).
Innovation Solution
A binder composition comprising tetracarboxylic acid ester compounds, diamine compounds, and an organic solvent, which forms a polyimide network that enhances adhesion without fully coating the active substance, allowing for stable SEI formation and accommodating the volume expansion of silicon-based anode materials during charging and discharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polyimide resin is used as a binder, then adhesion is improved, but active substance becomes completely coated and SEI formation is inhibited
Solution Approach 1:
The invention creates different local binding characteristics within the binder system. PAN provides strong adhesion at the current collector body interface, while PVDF provides binding between carbon particles in the bulk. This local differentiation allows SEI formation to occur at the active substance surface without being completely coated by the binder, resolving the contradiction between adhesion and SEI formation.
2Strength
If conventional binders are used with silicon-based anode active substance, then initial adhesion is achieved, but volume expansion causes cracks and pulverization during charging/discharging
Solution Approach 1:
The invention changes the binder composition parameters by incorporating PAN with flexible molecular chains and specific functional groups that can accommodate volume changes. The flexible structure of PAN allows it to stretch and compress with the silicon-based active substance during lithiation and delithiation, maintaining adhesion and preventing crack formation even when the active substance expands by 3-4 times its original volume.
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 binder composition provides improved adhesion and cycle life by forming a stable electrode interface and relieving stress from the expansion and contraction of anode active substances, preventing detachment and maintaining battery performance.
Implementation Method 1
a binder composition for electrodes basically comprises at least one type of tetracarboxylic acid ester compound, at least one type of diamine compound, and an organic solvent
Data Source
AI summary
A binder composition for electrodes with greater binding strength that does not inhibit the formation of a stable electrode interface (SEI) on the surface of an active substance is provided. The binder composition for electrodes includes at least one type of tetracarboxylic acid ester compound, at least one type of diamine compound, and an organic solvent. Furthermore, the organic solvent preferably has a boiling point that is 250° C. or less. In addition, the organic solvent preferably has a highest occupied molecular orbital (HOMO) that is −10 eV or less.