Negative Electrode End Protrusions to Prevent Battery Internal Shorts
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Solution Overview
Problem
The issue of internal short circuits and increased self-discharge in secondary batteries due to the exposure of the end portion of the electrode mixture layer during punching, leading to defects and reduced performance.
Innovation Solution
Incorporating a negative electrode with a niobium-titanium composite oxide as the active material and protrusions on the current collector end surfaces to shield the exposed areas, preventing contact with the positive electrode and reducing the likelihood of internal short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the electrode mixture layer is punched into a desired shape, then the electrode can be formed with the correct geometry for battery assembly, but the end portion of the electrode mixture layer may become exposed and lead to internal short circuits
Solution Approach 1:
The current collector is designed with protruding end portions that extend beyond the electrode mixture layer before punching. This preliminary structural arrangement ensures that after punching, the current collector still covers and protects the electrode mixture layer ends, preventing exposure and internal short circuits while maintaining the desired electrode shape.
Solution Approach 2:
The current collector acts as an intermediary protective element between the electrode mixture layer and the potential short circuit path. By making the current collector protrude at the ends, it serves as a physical barrier that prevents the electrode mixture layer from contacting opposite electrodes, thus mediating the protection against internal shorts.
2Weight of moving object
If the current collector thickness is reduced to minimize battery weight, then the battery energy density improves, but the structural support and protection capability of the current collector decreases
Solution Approach 1:
Instead of uniformly increasing the current collector thickness throughout, the invention applies local reinforcement by making only the end portions of the current collector protrude. This localized structural modification provides enhanced protection and support where it is most needed (at the ends where exposure occurs) while maintaining thin gauge in the central areas, thus balancing weight reduction with structural strength.
Data Source
AI summary
According to one embodiment, a secondary battery including a negative electrode. The negative electrode includes a negative electrode current collector and a negative electrode mixture layer. A thickness of the negative electrode current collector is in a range of 8 μm to 18 μm. The negative electrode current collector includes a first current collector end surface extending along a stacking direction. The negative electrode mixture layer includes a niobium-titanium composite oxide, and a first protrusion protruding from the first current collector end surface along a first direction orthogonal to the stacking direction. A protrusion length A1 of the first protrusion satisfies 0 mm<A1≤1.0 mm.