Cylindrical Battery Tab Layout to Prevent Core Foil-Cutting
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Solution Overview
Problem
The repeated expansion and contraction of electrode plates in cylindrical secondary batteries during charge-discharge cycles lead to increased surface pressure, which can cause core foil-cutting and deteriorate the battery's performance, especially due to the pressure exerted by the current collecting metal tabs.
Innovation Solution
The active material mixture layer is interposed between at least part of the width-directional end of the current collecting metal tab and the core, reducing the pressure exerted on the core and preventing foil-cutting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the electrode plates are packed in high density into the inside of the exterior can, then the battery capacity is improved, but the surface pressure exerted on the electrode plates rises
Solution Approach 1:
The active material mixture layer is introduced as an intermediary substance between the current collecting metal tab and the core. This intermediary layer distributes the pressure from the metal tab over a larger area of the core, preventing localized high pressure points while maintaining the high-density packaging configuration that improves battery capacity.
2Reliability
If the width and/or the thickness of the current collecting metal tab are increased, then the electric resistance is reduced, but the surface pressure locally exerted on the electrode assembly rises
Solution Approach 1:
The active material mixture layer serves as a pressure-distributing intermediary between the metal tab and core. This allows the metal tab to maintain sufficient width and thickness for low electric resistance while the intermediary layer ensures the pressure is distributed across a larger area of the core, preventing localized pressure concentration.
Solution Approach 2:
The invention changes the physical state and distribution parameters of the contact interface by introducing the active material mixture layer. This layer transforms the concentrated pressure contact into a distributed pressure field, allowing the metal tab dimensions to be optimized for electrical conductivity without proportionally increasing local pressure on the core.
3Force
If the surface pressure on the electrode plates rises, then the core receives increased pressure from the metal tab, but core foil-cutting occurs
Solution Approach 1:
The active material mixture layer acts as a protective intermediary between the metal tab and the core foil. This intermediary layer prevents direct concentrated contact between the rigid metal tab and the thin core foil, distributing the mechanical stress and preventing the foil-cutting phenomenon that would otherwise occur under repeated expansion and contraction cycles.
Solution Approach 2:
The active material mixture layer provides beforehand cushioning by being positioned in advance between the metal tab and core. This cushioning layer absorbs and distributes mechanical stresses before they can concentrate on the core foil, preventing foil-cutting from occurring during charge-discharge cycles.
Data Source
AI summary
A cylindrical secondary battery according to the present invention comprises a band-like core body and active material mixture layers that are formed on both surfaces of the core body, while having a wound body that is obtained by winding an electrode plate which is electrically connected to the core body by arranging a metal tab for current collection in an exposed part where the core body is exposed. The active material mixture layer is interposed between the core body and at least a part of an end of the metal tab for current collection in the width direction.