Cylindrical Battery Tab Layout to Prevent Electrode Core Breakage
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Solution Overview
Problem
Cylindrical batteries face issues with positive electrode core breakage due to slit burrs from the positive electrode tab pressing against the core during charge and discharge, especially with higher capacity and density mixtures, leading to impaired charge and discharge functionality.
Innovation Solution
The positive electrode tab is welded halfway in the winding direction with slit burrs positioned on the opposite side of the core and outside the winding, preventing direct contact during expansion and contraction, and optionally covered with an insulating tape to prevent short-circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the positive electrode tab is welded at the center in the winding direction to increase current collecting efficiency, then current collecting efficiency is improved, but the positive electrode core is more likely to break due to repeated pressing by slit burrs during expansion and contraction
Solution Approach 1:
The harmful slit burrs are extracted or removed from the critical area by positioning them away from the positive electrode core. The tab is welded at an off-center position so that the slit burrs are located at a position not facing the core, effectively separating the current collection function from the harmful mechanical stress concentration.
Solution Approach 2:
Instead of welding the tab at the center to maximize current collection, the invention inverts the approach by welding at an off-center position. This reverses the conventional wisdom but prevents the slit burrs from pressing against the core during expansion and contraction cycles.
2Quantity of substance
If higher density mixtures are used to increase battery capacity, then battery capacity is improved, but slit burrs repeatedly press against the positive electrode core due to expansion and contraction, increasing breakage probability
Solution Approach 1:
The harmful effect of slit burrs is extracted or removed from the system by repositioning them away from the positive electrode core. This allows higher density mixtures to be used for increased capacity without the accompanying risk of core breakage from burr pressing.
3Strength
If H material subjected to work-hardening is used for the positive electrode tab to increase strength, then tab strength is improved, but the probability that the positive electrode core breaks increases due to harder slit burrs pressing against it
Solution Approach 1:
The harmful slit burrs are extracted or removed from the interaction zone with the positive electrode core by positioning them away from the core. This allows the use of strong H material for the tab without the burrs causing core breakage, as the burrs are located at a position not facing the core.
Data Source
AI summary
A cylindrical battery comprises an electrode body formed by winding a positive electrode and a negative electrode. The positive electrode includes: a positive electrode core on which a positive electrode tab is welded at a point along the winding direction; and a positive electrode mix layer which is formed on both surfaces of the positive electrode core. The positive electrode tab includes slit burrs which are formed at the ends in the width direction. In a state in which the positive electrode is wound, the positive electrode tab is welded so that the slit burrs are positioned outside the winding and on the side opposite the surface where the positive electrode tab is welded to the electrode core.