Secondary Battery Anode Binder for Adhesion and Low Resistance
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Solution Overview
Problem
Existing secondary batteries face issues with anode adhesion and increased resistance due to the use of conventional binders, particularly when high-capacity anode active materials like silicon or silicon-tin alloys are used, leading to deteriorated performance and reduced battery life.
Innovation Solution
A copolymer binder comprising specific weight percentages of aliphatic conjugated diene-based, aromatic vinyl-based, unsaturated carboxylic acid-based, and polyethylene glycol mono(meth)acrylate repeat units is used to enhance adhesion and minimize resistance, improving the anode's performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high-capacity anode active materials (silicon, tin, silicon-tin alloy) are used to increase discharge capacity, then energy density is improved, but volume change during charge/discharge increases causing adhesion deterioration and resistance increase
Solution Approach 1:
The patent uses a composite binder system comprising styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) in a specific weight ratio (SBR:CMC = 1:4 to 4:1). This composite approach combines the adhesive properties of SBR with the structural stability and electrochemical compatibility of CMC, creating a binder that can accommodate the volume expansion of high-capacity anode materials while maintaining strong adhesion to the current collector.
Solution Approach 2:
The patent optimizes the molecular weight parameters of the binder components, specifically using SBR with weight average molecular weight of 50,000 to 1,000,000 and CMC with degree of substitution of 0.5 to 1.0 and viscosity of 10 to 1,000 mPa·s. These parameter optimizations ensure the binder maintains appropriate viscosity and adhesion properties that can withstand the mechanical stress from volume changes during charge/discharge cycles.
2Quantity of substance
If high-capacity anode active materials are used to improve energy density, then discharge capacity increases, but internal resistance increases due to bond loosening and contact resistance
Solution Approach 1:
The composite SBR-CMC binder system maintains intimate contact between active material particles and the current collector through the synergistic action of both polymers. CMC provides a hydrophilic matrix that maintains particle contact, while SBR contributes elastic properties that accommodate volume changes, preventing bond loosening and maintaining low contact resistance throughout battery cycling.
Solution Approach 2:
The binder system provides different local properties within the anode structure: CMC forms a stable hydrophilic network that maintains electrical contact, while SBR provides localized elastic cushioning at particle interfaces. This local differentiation of binder properties ensures both structural integrity and electrical conductivity are maintained despite volume changes in the active material.
3Ease of manufacture
If conventional binders (PVDF) are used with high-capacity anode materials, then manufacturing is simple, but battery life is reduced due to adhesion deterioration
Solution Approach 1:
The SBR-CMC composite binder combines the ease of aqueous-based application (similar to conventional binders) with enhanced performance characteristics. Both components are water-soluble or dispersible, allowing for simple slurry preparation and coating processes, while their synergistic interaction provides superior long-term adhesion retention during extended cycling.
Solution Approach 2:
The CMC component acts as an intermediary between the hydrophilic electrolyte environment and the anode active material particles, maintaining a stable interface that prevents direct degradation pathways. This intermediary role of CMC, combined with the adhesive SBR, creates a protective interface that extends battery life while maintaining manufacturing simplicity.
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 anode adhesion, reduces internal resistance, and extends the life of secondary batteries by facilitating better adhesion between the anode current collector and active materials, while enhancing ionic conductivity and lithium ion transfer.
Implementation Method 1
improve anode adhesion... better adhesion between the anode current collector and active materials
Data Source
AI summary
This invention relates to a binder for an anode of a secondary battery, an anode of a secondary battery, and a secondary battery. Specifically, this invention provides a binder for an anode of a secondary battery that can not only improve anode adhesion, but also minimize resistance in a secondary battery, and ultimately, improve the life of a secondary battery.