Electrode Binder Gradient for Battery Mixture Layer Retention
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Solution Overview
Problem
Existing nonaqueous electrolyte secondary battery electrodes face issues with mixture layer loss and deteriorated cycle characteristics due to uneven binder distribution, particularly when the binder content is increased at the edges of the current collector.
Innovation Solution
The electrode design features a rectangular current collector with a mixture layer that covers at least one edge, with a maximum binder content 0.5 mm to 5.5 mm away from the edge, exceeding 100% to 240% of the central binder content, ensuring the mixture layer's integrity and electrolyte permeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the binder content is increased at the edge of the current collector to suppress mixture layer loss, then the mixture layer retention is improved, but the cycle characteristics of the battery deteriorate
Solution Approach 1:
The invention applies local quality by creating a binder content gradient where the binder concentration varies across different regions of the mixture layer. Specifically, the binder content is higher at positions 0.5-5.5 mm from the edge compared to the center, providing localized reinforcement at the vulnerable edge regions while maintaining lower binder content in the center to preserve active material density and electrochemical performance throughout the battery cycle life.
Solution Approach 2:
The invention changes the parameter of binder content distribution from uniform to non-uniform. By controlling the binder content to be 100-240% of the center value at specific positions from the edge, the invention optimizes both edge retention and cycle characteristics through precise parameter control, avoiding the deterioration caused by excessive binder content while ensuring sufficient edge strength.
2Reliability
If the binder content in the mixture layer is increased to prevent mixture layer loss, then the mixture layer integrity is improved, but the battery capacity decreases
Solution Approach 1:
The invention uses local quality by concentrating higher binder content (100-240% of center value) specifically at positions 0.5-5.5 mm from the edge where mixture layer loss is most likely to occur, while maintaining lower binder content in the central regions. This localized approach provides necessary structural integrity at critical areas without excessively reducing active material content in the bulk, thereby preserving battery capacity.
Solution Approach 2:
The invention applies partial action by increasing binder content only in specific regions (0.5-5.5 mm from edge) rather than uniformly throughout the entire mixture layer. This partial reinforcement provides sufficient protection against mixture layer loss at vulnerable edges while minimizing the displacement of active material, thus maintaining high battery capacity.
3Ease of manufacture
If the binder content is uniformly distributed in the mixture layer, then the manufacturing process is simplified, but the mixture layer is lost at the end of the current collector
Solution Approach 1:
The invention transitions from uniform to non-uniform binder distribution, creating a gradient where binder content is 100-240% of the center value at positions 0.5-5.5 mm from the edge. This local quality enhancement provides targeted reinforcement at the vulnerable edges where mixture layer loss occurs, while maintaining a relatively simple manufacturing process through controlled gradient formation.
Data Source
AI summary
An electrode for a nonaqueous electrolyte secondary battery that is less likely to cause loss of a mixture layer and that can ensure good cycle characteristics of the battery. An electrode for a nonaqueous electrolyte secondary battery of an exemplary embodiment includes a rectangular current collector and a mixture layer that contains an active material and a binder and that is formed on the current collector. The mixture layer covers at least one edge of four linear peripheral edges of the current collector, and the binder content in the mixture layer has a maximum value at a position 0.5 mm to 5.5 mm away from the one edge in a second direction that is perpendicular to a first direction along the one edge. The maximum value is more than 100% and 240% or less of the binder content at the center in the second direction of the mixture layer.