Cyclic Polymer Binder for Silicon Anode Volume Expansion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium secondary batteries using silicon-based materials face capacity deterioration due to volume expansion and side reactions, leading to reduced lifespan and efficiency.
Innovation Solution
A binder composition with an interpenetrating network structure, comprising a cyclic polymer and a copolymer, is used to enhance the binding strength between the electrode active material and the electrode plate, controlling expansion and maintaining the electrode structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based materials are used as electrode active material, then battery capacity is improved, but volume expansion occurs during charge/discharge cycles leading to capacity deterioration
Solution Approach 1:
The binder composition forms a flexible coating film around the silicon-based electrode active material particles. This flexible film accommodates the volume expansion and contraction of silicon during lithium insertion/extraction cycles, preventing structural degradation while maintaining electrical contact and binding integrity throughout charge/discharge operations.
Solution Approach 2:
The invention uses a composite binder system comprising multiple polymer components with different functions: a first binder component providing basic adhesion, a second binder component forming crosslinked networks for structural stability, and optionally a third binder component for additional flexibility. This composite approach allows the binder to simultaneously adhere to silicon particles, maintain electrode structure, and accommodate volume changes.
2Ease of manufacture
If conventional binders are used, then manufacturing is simple, but binding strength between electrode active material and electrode plate is insufficient
Solution Approach 1:
The binder composition parameters are optimized to achieve both ease of manufacture and high binding strength. The total binder content is controlled at 1-10 wt% of electrode active material, the first binder component is limited to 1-50 wt% of total binder, and the second binder component comprises 50-99 wt% of total binder. These parameter ranges ensure proper viscosity for coating while achieving crosslinked network formation for strong binding.
Solution Approach 2:
The binder composition acts as an intermediary material between the silicon-based electrode active material particles and the electrode plate substrate. It provides adhesion to the substrate while coating and binding the active material particles, forming a cohesive electrode structure that maintains integrity during cycling.
3Duration of action of stationary object
If electrode structure is maintained during volume expansion, then lifespan is improved, but binder composition complexity increases
Solution Approach 1:
The binder composition is segmented into functional components with distinct roles: the first binder component (1-50 wt%) provides initial adhesion and flexibility, the second binder component (50-99 wt%) forms the crosslinked structural network, and the optional third binder component (1-49 wt%) adds supplementary binding. This segmentation allows each component to be optimized for its specific function while working together to extend battery lifespan.
Solution Approach 2:
The crosslinking density and network structure of the binder are controlled by adjusting the ratio and molecular weight of the second binder component. By controlling these parameters within specific ranges, the binder achieves optimal balance between structural rigidity for electrode integrity and flexibility for accommodating silicon volume changes, thereby extending battery lifespan without excessive complexity.
Data Source
AI summary
A binder composition for a lithium secondary battery, an electrode, and a lithium secondary battery, the binder composition including an interpenetrating network structure that includes a cyclic polymer, the cyclic polymer including a repeating unit represented by Formula 1 or a repeating unit represented by Formula 2; and a copolymer, the copolymer including a repeating unit represented by Formula 3 and a repeating unit represented by Formula 4, wherein an amount of the repeating unit represented by Formula 3 is about 40 mol % to about 70 mol %, based on a total amount of the copolymer: