Non-aqueous Electrode Width Optimization for Battery Tab Integrity
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries face issues with capacity reduction due to minute internal short circuits and tab defects, such as bending, which affect their high-current characteristics and overall performance.
Innovation Solution
The battery design includes a positive electrode with a continuous tab and a negative electrode with a lithium titanate active material layer, where the width relationships between the active material layers and current collectors are optimized to prevent short circuits, and the manufacturing method involves forming active material layers on both surfaces of the current collector to enhance tab strength and reduce defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the resistance of the active material layer is reduced to improve high-current characteristics, then the battery can output higher power, but minute leakage current increases causing capacity reduction
Solution Approach 1:
A resin layer is introduced as an intermediary between the active material layer and the separator. This resin layer has lower conductivity than the active material layer, acting as a barrier to prevent leakage current from reaching the separator and causing short circuits, while still allowing the active material layer to maintain low resistance for high-current output
Solution Approach 2:
The resin layer is applied locally only in specific regions where leakage current paths are most likely to occur, such as near the tabs and edges of the active material layer. This localized treatment prevents leakage current without requiring the entire active material layer to have increased resistance, preserving high-current characteristics
2Power
If the number of tabs is increased to reduce resistance, then high-current characteristics improve, but strain occurs at the boundary between active material layer and tabs during rolling
Solution Approach 1:
The tabs are formed with extended width before the rolling process. This preliminary dimensioning ensures that during rolling, the tabs can accommodate the applied pressure without creating excessive strain concentration at the boundary between the active material layer and tabs, preventing gaps and maintaining electrode integrity
Solution Approach 2:
The width of the tabs is optimized as a geometric parameter to balance two requirements: sufficient width to reduce resistance by increasing current collection area, and controlled width to minimize strain concentration at the tab boundaries during the rolling process
3Power
If the active material layer is pressed to reduce resistance, then high-current characteristics improve, but strain is caused at the boundary with tabs
Solution Approach 1:
The resin layer acts as a counterbalancing element at the tab boundaries. During pressing, the resin layer absorbs and distributes the compressive forces, counteracting the strain that would otherwise concentrate at the boundary between the active material layer and tabs, thereby preventing damage while allowing resistance reduction through pressing
Data Source
Figure 1~2
Figure 3~4B
Figure 5~6
AI summary
A non-aqueous electrolyte secondary battery includes an electrode body including a positive electrode (18) and a negative electrode (20) superimposed upon each other with a separator (22) interposed therebetween. The negative electrode (20) is superimposed upon the positive electrode (18) in a state where a negative electrode active material layer (20b), except the part on a proximal end part of a negative electrode tab (20c), is positioned inside an outer edge of a positive electrode active material layer (18b) of the positive electrode. A width H1 of the negative electrode active material layer including the part on the proximal end part of the negative electrode tab, width H2 of the negative electrode active material layer or negative electrode current collector at a part other than the negative electrode tab, and width H3 of the positive electrode active material layer are formed to satisfy the relationships of H2<H3, and (H1-H2)≥(H3-H2)ö2.