Battery Protective Film Segmentation for Safety Valve Peeling
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Solution Overview
Problem
Conventional batteries face challenges in achieving both fixing durability and peeling easiness of the protective film during normal use and safety valve operation, as the protective film's surface area and fixing strength affect its ability to release gas effectively.
Innovation Solution
A battery design with a protective film that includes a valve-corresponding unfixed portion, a first fixed portion, and a second fixed portion, where the first fixed portion peels off earlier than the second, increasing the pressure receiving area and facilitating easy peeling of the second portion, ensuring both durability and ease of gas release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the protective film is fixed in annular and solid manner to the battery case around the safety valve without contacting a portion of the battery case facing the safety valve, then the fixing strength is improved, but the peeling easiness deteriorates
Solution Approach 1:
The protective film is divided into multiple fixed portions (first fixed portion, second fixed portion) and unfixed portions (valve-corresponding unfixed portion, intermediate unfixed portion). This segmentation allows different regions to serve different functions: fixed portions provide attachment strength while unfixed portions enable peeling during safety valve operation.
Solution Approach 2:
Different portions of the protective film have different fixing characteristics. The first and second fixed portions are designed to be fixed to the battery case to provide durability, while the valve-corresponding unfixed portion and intermediate unfixed portion are designed to be unfixed to allow peeling. This local differentiation resolves the contradiction between overall fixing strength and localized peeling ease.
2Duration of action of stationary object
If the surface area of the solidly fixed portion of the protective film is large, then the fixing durability is improved, but the gas release capability deteriorates
Solution Approach 1:
The fixed portions are segmented and separated by unfixed portions. When the safety valve operates and internal pressure increases, gas can penetrate through the unfixed portions and exert pressure on the fixed portions, causing them to peel off sequentially. This segmentation ensures that even with large total fixed area, the film can still release gas effectively.
Solution Approach 2:
The unfixed portions act as intermediaries that allow gas to reach and act upon the fixed portions. Gas penetrates through the valve-corresponding unfixed portion first, then through the intermediate unfixed portion, exerting pressure on the fixed portions to facilitate their peeling. This intermediary mechanism enables gas release despite large fixed surface area.
Data Source
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AI summary
Provided is a battery capable of providing both fixing durability of a protective film during normal use and peeling easiness of the protective film during operation of a safety valve. A lithium ion secondary battery (100) includes a protective film (140) fixed to a battery case (110) while covering a safety valve part (125) including a breakable portion (126). This protective film (140) has a first fixed portion (145) located around a valve-corresponding unfixed portion (144) and fixed to the battery case (110) and a second fixed portion (147) located more outside than the first fixed portion and fixed to the battery case (110) through an intermediate unfixed portion (146). They are configured such that the first fixed portion (145) first peels off when the safety valve part (125) operates, prompting peeling of the second fixed portion (147), thus releasing gas to the outside.