Binder Composition for Rechargeable Battery Electrode Expansion Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium batteries face challenges with carbon-based materials having low capacity and poor lifetime characteristics due to volumetric changes during charge and discharge cycles, and existing binders struggle to balance flexibility and strength, especially when used with non-carbon based active materials like Si or Sn, leading to electrode deformation and capacity reduction.
Innovation Solution
A binder composition with a glass transition temperature of 20° C. or less and a storage modulus of 50-150 MPa, incorporating a styrene-butadiene rubber-based polymer and nano particles, is developed to control the shrinkage-expansion ratio of negative electrode active materials, enhancing adhesion and structural stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If metal alloyable with lithium (Si, Sn, Al) is used as negative electrode active material to achieve higher electric capacity than carbon-based material, then electric capacity is improved, but lifetime characteristics deteriorate due to aggregation and pulverization of metal particles during charge and discharge cycles
Solution Approach 1:
The patent uses a composite binder system comprising both carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) polymers. This composite binder combines the advantages of CMC (good adhesion, suppresses pulverization) and SBR (flexibility, absorbs volume expansion) to simultaneously improve capacity and lifetime characteristics of metal alloy-based negative electrodes
2Shape
If polyimide or polyamideimide is used as binder to suppress expansion of electrode, then electrode expansion is controlled, but electrode cracks occur during rolling and pressing processes, making commercialization difficult
Solution Approach 1:
The patent changes the physical and chemical parameters of the binder by using CMC and SBR polymers with specific glass transition temperatures and mechanical properties. This combination provides both expansion control and processing flexibility, avoiding electrode cracks during manufacturing while maintaining shape stability
3Ease of operation
If diene-based copolymer binder is used in negative electrode to provide high flexibility, then flexibility is improved, but strength decreases when immersed in electrolytic solution, making it difficult to suppress expansion of non-carbon based high capacity negative electrode active material
Solution Approach 1:
The patent employs a composite binder system where CMC provides strength and adhesion after electrolyte immersion, while SBR provides flexibility. Together they suppress electrode expansion effectively without the limitations of single-polymer binders
4Reliability
If binder with high storage modulus is used to control high shrinkage-expansion ratio of negative electrode active material, then lifetime characteristics are improved, but adhesion between negative electrode active material and current collector may deteriorate
Solution Approach 1:
The patent optimizes the glass transition temperatures and mechanical properties of the binder polymers. CMC provides strong adhesion through chemical bonding, while SBR's lower Tg provides flexibility and shock absorption, together achieving both high adhesion and improved lifetime characteristics
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 effectively suppresses electrode expansion, improves battery life retention, and maintains high capacity by adjusting the storage modulus and glass transition temperature, preventing capacity reduction and lifetime deterioration.
Implementation Method 1
a binder polymer having a glass transition temperature (Tg) of 20° C. or less, and having a storage modulus (60° C.) of 50-150 MPa
Implementation Method 2
a binder polymer having a glass transition temperature (Tg) of 20° C. or less
Data Source
AI summary
A binder composition for a rechargeable battery, including a binder polymer having a glass transition temperature (Tg) of 20° C. or less, and having a storage modulus (60° C.) of 50-150 MPa. The binder composition according to an embodiment can improve life characteristics of the rechargeable battery by efficiently controlling expansion of a negative electrode plate.