Film Covered Battery Sealing Zone Design
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Solution Overview
Problem
Thick cell elements in film-covered batteries are prone to micro-crack formation at the root of the thermally sealed area due to atmospheric pressure, leading to reduced sealing reliability and potential leakage, especially when the thermally sealed area is close to the cell element.
Innovation Solution
A film-covered electric device design where the casing films have a close contact zone between the thermally sealed area and the cell element, with the length of this zone being at least half the distance from one end to the other end of the thermally sealed area, to relax the peeling force and prevent micro-crack formation, and a method of manufacturing involving thermal sealing with a head positioned 2 mm or more from the cell element to form this zone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the thermally sealed area is positioned close to the cell element to improve volumetric efficiency, then the battery volume is reduced, but micro-cracks occur at the root of the thermally sealed area due to atmospheric pressure acting on thick cell elements
Solution Approach 1:
The invention introduces a close contact zone with specific length requirements (L2 ≥ 0.5L1) between the thermally sealed area and the cell element. This localized structural modification distributes the peeling force generated by atmospheric pressure, preventing micro-crack formation at the root of the thermally sealed area while maintaining overall compactness
Solution Approach 2:
The close contact zone is designed in advance with predetermined length relationships (L1 and L2) to preemptively counteract the peeling force that will occur during reduced pressure sealing and atmospheric pressure return. This preliminary structural arrangement prevents micro-crack formation before it can occur
2Quantity of substance
If the cell element thickness is increased to achieve larger capacity, then the battery capacity is improved, but the peeling force at the thermally sealed area root increases causing micro-crack formation
Solution Approach 1:
The close contact zone creates a localized stress distribution pattern that accommodates thick cell elements. By requiring L2 ≥ 0.5L1, the invention ensures that the peeling force is distributed over a sufficient length, preventing concentration of stress that would cause micro-cracks in high-capacity thick cell elements
3Shape
If the cup area depth is increased to accommodate thicker cell elements, then the cell element containment is improved, but the peeling force at the thermally sealed area root increases causing micro-crack formation
Solution Approach 1:
The close contact zone with length L2 ≥ 0.5L1 is specifically designed to handle the peeling force generated by deep cup areas. This localized structural feature distributes the stress concentration that occurs when atmospheric pressure acts on deeply drawn cup areas containing thick cell elements
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Prevents micro-crack occurrence at the root of the thermally sealed area, enhancing the sealing reliability of the cell element and preventing leakage, even in thick cell elements, by distributing the peeling force effectively and maintaining the structural integrity of the casing materials.
Implementation Method 1
the peripheral sides of the casing film are thermally sealed to seal the electric device element with the leads extended therefrom
Implementation Method 2
the root of the thermally sealed area is pressed against the cell element by the action of the atmospheric pressure on the casing materials
Data Source
AI summary
The occurrence of micro-crack is prevented at the root of a thermally sealed area of casing materials even if a thick electric device element is sealed. Film covered battery 10 has cell element 13 to which leads 12a, 12b are connected, and casing films 11 for sealing cell element 13 with leads 12a, 12b extended therefrom. Casing films 11 are thermally sealed along the periphery to seal cell element 13. Thermally sealed area 13 of casing films 11 is positioned between both surfaces of cell element 13 in the thickness direction of cell element 13. On a side of casing films 11 from which leads 12a, 12b are not extended, close contact zone 15, in which casing films 11 are not thermally sealed to each other but are in close contact with each other, is formed continuously to a space which receives cell element 13. Close contact zone 15 has a length of one-half or more of the distance from one end to the other end of an inner edge of thermally sealed area 14.