Copolymer Anode Binder for Silicon Expansion and Peeling
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Solution Overview
Problem
Existing binders for anode active materials in secondary batteries, such as carboxymethyl cellulose (CMC) and styrene butadiene rubber (SBR), fail to provide sufficient adhesive force, leading to deterioration of charge and discharge characteristics due to volume expansion of silicon-based active materials during charging and discharging, resulting in reduced battery lifespan and performance.
Innovation Solution
A copolymer binder with a specific composition and molecular weight range, comprising repeating units derived from vinyl acetate, vinyl alcohol, (meth)acrylate, and (meth)acrylic acid salts, is used to enhance the mechanical properties and adhesion force, suppressing anode expansion and peeling, and improving the binding force between the anode active material and current collector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If existing binders (CMC or SBR) are used for silicon-based anode active material, then volume expansion can be partially solved, but adhesive force is insufficient leading to binder deterioration during charging and discharging
Solution Approach 1:
The invention uses a composite binder system comprising both carboxymethyl cellulose (CMC) and styrene butadiene rubber (SBR) in a specific weight ratio range (SBR: 1-20 wt%, CMC: 80-79 wt%). This composite approach combines the volume expansion buffering capability of SBR with the structural stability and adhesive properties of CMC, resolving the contradiction between structure stability and adhesive force that plagues single-component binders.
2Quantity of substance
If silicon-based anode active material is used, then energy density can be improved, but volume expansion during charging and discharging deteriorates charge and discharge characteristics
Solution Approach 1:
The binder system is designed to provide beforehand cushioning against the volume expansion of silicon-based anode active material during lithium ion insertion. The CMC component forms a stable gel structure that cushions and constrains the silicon particles, while SBR provides flexible volume accommodation. This prior cushioning mechanism prevents structural degradation and maintains reliable charge and discharge characteristics throughout battery cycling.
3Strength
If binder adhesive force is increased to prevent peeling, then structural stability improves, but coatability and processing may be affected
Solution Approach 1:
The invention optimizes the weight ratio parameters of the binder components (SBR: 1-20 wt%, CMC: 80-79 wt%) to achieve the desired balance between adhesive force and coatability. By adjusting these compositional parameters, the binder system maintains high adhesive strength to prevent active material peeling while preserving adequate coatability for practical electrode manufacturing processes.
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 effectively stabilizes the anode structure, reduces resistance increase due to volume expansion, and enhances the charge and discharge life characteristics and performance of secondary batteries, maintaining a high capacity retention rate after multiple cycles.
Implementation Method 1
enhances the binding force between the anode active material and current collector
Data Source
AI summary
The present invention relates to a binder for an anode for a secondary battery, an anode including the binder, and a secondary battery including the anode. More particularly, the present invention relates to a binder for an anode for a secondary battery that has excellent heat resistance and mechanical properties and an improved binding force because a copolymer is used for the binder, and an anode for a secondary battery. In addition, expansion and shrinkage of the anode may be efficiently suppressed, such that charge and discharge life characteristics and performance of the secondary battery may be improved.