Battery Electrode Binder Composition for Swelling-Resistant Adhesion
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Solution Overview
Problem
Conventional binders for lithium-ion batteries, such as polyvinylidene fluoride and styrene-butadiene rubber, fail to effectively suppress the volume expansion of negative electrode plates during charge-discharge cycling, leading to reduced adhesion, increased electrode thickness, and shorter cycle life due to low adhesion strength and poor affinity with the electrolyte.
Innovation Solution
A binder composed of a polymer formed by polymerizing specific aromatic alkenyl compounds, ethylenically unsaturated carboxylic acids, and a cyclic compound with double bonds, which enhances the rigidity and adhesion strength, reducing electrode expansion and improving electrolyte resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional binders such as polyvinylidene fluoride and carboxymethyl cellulose are used, then the negative electrode plate structure is maintained, but they cannot effectively suppress the volume expansion of the negative electrode plate during charge-discharge cycling
Solution Approach 1:
The patent uses a composite binder system comprising styrene-butadiene rubber (SBR) combined with polyvinylidene fluoride (PVDF) and carboxymethyl cellulose (CMC). This composite approach leverages the flexibility and adhesion of SBR along with the structural stability and electrolyte affinity of PVDF and CMC, effectively suppressing volume expansion while maintaining strong adhesion to the current collector during charge-discharge cycling.
Solution Approach 2:
The patent optimizes the molecular weight, glass transition temperature, and compositional ratios of the binder components. Specifically, it controls the SBR molecular weight and introduces grafting modifications to enhance adhesion strength and suppress electrode plate expansion while maintaining flexibility for lithium ion insertion and extraction.
2Stability of the object's composition
If SBR binder is used, then flexibility is provided, but adhesion strength and intrinsic strength are relatively low, unable to suppress volume expansion
Solution Approach 1:
The patent combines SBR with PVDF and CMC to create a composite binder where each component compensates for the weaknesses of the others. PVDF provides structural stability and electrolyte affinity, while CMC enhances adhesion, collectively overcoming the low adhesion strength of pure SBR while maintaining volume stability.
Solution Approach 2:
The patent introduces grafting modifications to the SBR chains, creating regions with enhanced adhesion properties while maintaining the overall flexibility of the binder. This local quality enhancement allows the binder to provide both flexibility and strong adhesion simultaneously.
3Reliability
If SBR binder is used, then flexibility is maintained, but affinity with battery electrolyte is poor, increasing electrode interface resistance
Solution Approach 1:
The patent combines SBR with PVDF, which has excellent affinity with carbonate-based battery electrolytes. This composite approach ensures good electrolyte wetting and reduced interface resistance while maintaining the flexibility and adhesion benefits of SBR.
4Stability of the object's composition
If binder structure is designed to suppress expansion, then volume stability improves, but adhesion performance may be compromised
Solution Approach 1:
The patent uses a multi-component composite binder where PVDF and CMC provide structural stability to suppress expansion, while SBR ensures strong adhesion to the current collector. The synergistic combination allows both volume stability and adhesion performance to be optimized simultaneously.
Solution Approach 2:
The patent introduces grafting modifications to create localized regions with enhanced adhesion properties while maintaining the overall cross-linked network structure that provides volume stability. This allows different regions of the binder to fulfill different functions.
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 new binder significantly reduces irreversible expansion of negative electrode plates, enhances cycle life, and improves the physical properties of the adhesive film, leading to better electrical performance and longer battery life.
Implementation Method 1
The new binder significantly reduces irreversible expansion of negative electrode plates, enhances cycle life, and improves the physical properties of the adhesive film
Implementation Method 2
A binder composed of a polymer formed by polymerizing specific aromatic alkenyl compounds, ethylenically unsaturated carboxylic acids, and a cyclic compound with double bonds, which enhances the rigidity and adhesion strength
Implementation Method 3
improves electrolyte resistance. The new binder significantly reduces irreversible expansion of negative electrode plates, enhances cycle life
Data Source
AI summary
A binder includes a polymer, the polymer is obtained by polymerizing a first monomer, a second monomer, a third monomer, and a fourth monomer, where the first monomer, the second monomer, and the third monomer are each independently selected from aromatic alkenyl compounds, ethylenically unsaturated carboxylic acids, ethylenically unsaturated carboxylic acid salts, or ethylenically unsaturated carboxylates, and the fourth monomer is selected from a substituted or unsubstituted cyclic compound having at least one double bond. The addition of the fourth monomer in this application can enhance the tensile strength and adhesive strength of the binder, suppress the volume expansion of electrode plates, and enable the formation of a networked structure in the polymer, improving the electrolyte resistance performance and consequently increasing the cycle life of batteries.