Secondary Battery Electrode Layering to Prevent Binder Migration
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Solution Overview
Problem
The issue of binder migration during high-temperature drying in the production of secondary battery electrodes leads to peeling of the current collector and active material layer, reducing battery performance and increasing ion resistance while compromising flexibility.
Innovation Solution
The electrode body features a two-layer structure with a first layer having a binder composed of surface-contact-shaped particles for strong binding and a second layer with point-contact-shaped particles to maintain flexibility and reduce ion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-temperature drying is used to shorten drying time and increase production efficiency, then productivity is improved, but binder migration occurs causing peeling between current collector and active material layer
Solution Approach 1:
The invention applies different binder characteristics to different layers of the active material layer. The lower layer uses a binder with high binding power to current collector, while the upper layer uses a binder with different properties optimized for its position. This local differentiation allows high-temperature drying without binder migration causing peeling, as each layer's binder is optimized for its specific function and position.
2Strength
If binder amount is increased to suppress peeling, then binding strength is improved, but ion resistance increases
Solution Approach 1:
The invention concentrates the binder with high binding power in the lower layer that contacts the current collector, while the upper layer uses a different binder composition. This localized placement ensures strong binding at the critical interface without excessive binder throughout the entire active material layer, thereby maintaining low ion resistance while achieving sufficient binding strength.
Solution Approach 2:
The invention uses a composite binder system with two different binders having distinct characteristics. One binder is optimized for binding to current collector, while the other is optimized for the upper layer's requirements. This composite approach allows optimization of both binding strength and ion conductivity by placing the appropriate binder in the appropriate location.
3Object-affected harmful factors
If binder amount is reduced to decrease ion resistance, then ion resistance is improved, but flexibility decreases
Solution Approach 1:
The invention places the binder optimized for flexibility in the upper layer, while the lower layer contains the binder optimized for binding strength. This spatial distribution allows the upper layer to maintain flexibility with appropriate binder content, while the lower layer provides strong binding without compromising overall ion resistance.
Data Source
AI summary
An electrode body having a current collector layer and an active material layer laminated on the current collector layer, wherein the active material layer has a first layer on the current collector layer and a second layer on the first layer, the first binder included in the first layer is composed of particles in a surface contact shape, and the second binder included in the second layer is composed of particles in a point contact shape.