Silicon Electrode Binder Copolymer for Expansion Management
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Solution Overview
Problem
Silicon negative electrode active materials in secondary batteries face degradation due to repeated expansion and contraction during charging and discharging, leading to electrode structure damage and reduced performance.
Innovation Solution
A copolymer binder with a rigid unit and an elastic unit, incorporating specific monomer units with varying glass transition temperatures and aqueous solubility, is used to enhance binding force and adhesion to the current collector, effectively addressing the expansion and contraction issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon series active material is used to increase capacity, then theoretical capacity is improved, but electrode structure is destroyed due to repeated expansion and shrinkage
Solution Approach 1:
The patent changes the physical and chemical parameters of the binder by selecting specific polymers with different glass transition temperatures (Tg). The first polymer has Tg of 80°C or higher providing rigidity, while the second polymer has Tg of 70°C or lower providing elasticity. This parameter optimization allows the binder to maintain structural integrity during silicon expansion and contraction while preserving electrical conductivity.
Solution Approach 2:
The patent uses a composite binder system comprising two different polymers with complementary properties. The first polymer (rigid, high Tg) provides structural support and maintains electrode integrity, while the second polymer (elastic, low Tg) accommodates volume changes during charge-discharge cycles. This composite approach resolves the contradiction between maintaining structural stability and accommodating capacity expansion.
2Ease of manufacture
If conventional binder is used, then manufacturing is simple, but binding force between active materials and adhesive force to current collector are insufficient
Solution Approach 1:
The patent optimizes the molecular weight parameters of the polymers used in the binder. The first polymer has weight average molecular weight of 100,000 to 5,000,000 and the second polymer has 50,000 to 2,000,000. These parameter ranges provide optimal balance between binding strength and processability, maintaining ease of manufacture while significantly improving adhesion to current collector and binding force between active materials.
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 copolymer binder improves the cycle stability and storage performance of silicon negative electrodes by maintaining excellent binding force and adhesion, thereby enhancing the overall performance of secondary batteries.
Implementation Method 1
The copolymer may comprise a first monomer unit having a glass transition temperature of a homopolymer of 80° C. or higher and a second monomer unit having the glass transition temperature of a homopolymer of 70° C. or lower
Data Source
AI summary
The present application relates to a binder. The present application can provide a binder which can be applied to production of silicon series negative electrodes to cope well with shrinkage and expansion by repeated charge and discharge, and has excellent binding force between active materials and adhesive force to a current collector, and an active material composition, an electrode and a secondary battery, comprising the same.