Partially Crosslinked Anode Binder for Silicon Expansion Stability
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Solution Overview
Problem
Lithium secondary batteries using silicon-containing compounds as anode active materials face challenges due to significant volume expansion during charging and discharging, which can lead to a deterioration in battery performance and limit the commercialization of high-capacity anode batteries.
Innovation Solution
The development of an anode composition featuring a partially crosslinked anode binder polymer, comprising (meth)acrylamide group-containing compounds, unsaturated organic acids, α,β-unsaturated nitriles, and diacrylamide- or diacrylate-containing compounds, which helps to suppress volume expansion and maintain the conductive path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-containing compounds are used as anode active material to increase capacity, then discharge capacity is improved, but volume expansion during charging causes conductive path cutoff and performance deterioration
Solution Approach 1:
A binder polymer comprising polyacrylonitrile and polyacrylic acid in a weight ratio of 95:5 to 50:50 is introduced as an intermediary material between the silicon-containing anode active material particles and the conductive network. This binder polymer mediates the mechanical stress from volume expansion, preventing conductive path cutoff while maintaining electrical connectivity, thus resolving the contradiction between high capacity and conductive path stability.
2Stability of the object's composition
If binder polymers with strong stress are used to suppress volume expansion, then volume change is reduced, but electrode thickness increase and performance deterioration occur
Solution Approach 1:
The chemical composition parameters of the binder polymer are precisely controlled, specifically the weight ratio of polyacrylonitrile to polyacrylic acid within 95:5 to 50:50, and the carbonyl group content within 0.5 to 5.0 mmol/g. This parameter optimization enables the binder to provide adequate mechanical support for volume stability while maintaining flexibility that prevents excessive electrode thickness increase.
3Strength
If crosslinking agent is introduced into binder polymers to improve performance, then adhesion is enhanced, but viscosity change and phase stability problems occur during long-term storage
Solution Approach 1:
Instead of using permanent crosslinking agents that cause long-term stability issues, the invention employs a non-crosslinking binder polymer formulation that provides sufficient adhesion strength through optimized polymer composition and interfacial interactions. This approach sacrifices some long-term structural permanence in favor of maintaining slurry phase stability during storage, resolving the contradiction between adhesion enhancement and phase stability.
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
This solution effectively minimizes thickness changes in the anode during charging and discharging, thereby enhancing the capacity retention rate and overall lifespan performance of lithium secondary batteries.
Implementation Method 1
the binder polymer comprises: a (meth)acrylamide group-containing compound; an unsaturated organic acid or a salt of the unsaturated organic acid; monomer units including α,β-unsaturated nitriles; and a diacrylamide- or diacrylate-containing compound
Data Source
AI summary
An anode composition, a lithium secondary battery anode including the same, and a lithium secondary battery including the anode.