Injection Port Tubular Sealing for Void-Free Battery Laminate Welding
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Solution Overview
Problem
Conventional power storage device manufacturing methods result in void formation in the tubular member surrounding injection ports due to increased internal pressure during welding, leading to poor sealability of spaces within the tubular member.
Innovation Solution
A manufacturing method involving the use of different resins with varying melting points and glass transition temperatures for the tubular member and laminate film, where the outer region contacts the laminate film and the inner region contacts the tubular member, with heat pressing at a temperature between the melting points of these resins to prevent excessive melting and void formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the tubular member is pushed-in the direction of pressure application during heat pressing, then the welding between laminate film and tubular member is improved, but the internal pressure of spaces within the tubular member rises causing air to break-through and form voids
Solution Approach 1:
The tubular member is divided into multiple regions with different resin types (first region with resin L, second region with resin H) having different melting points. This segmentation allows the outer region to melt and bond during welding while the inner region remains solid to maintain sealing pressure
Solution Approach 2:
Different regions of the tubular member are assigned different material properties: the first region (outer surface) uses resin L with lower melting point for welding, while the second region (inner portion) uses resin H with higher melting point for maintaining sealability. This local differentiation resolves the contradiction between welding quality and sealability
2Strength
If the resin at the surface contacting the laminate film is melted by heat pressing, then bonding between laminate film and tubular member is achieved, but the fluidity increases causing internal pressure buildup and void formation
Solution Approach 1:
The melting points of resins are carefully selected and differentiated: resin L (first region) and resin lam (laminate film) have lower melting points for bonding, while resin H (second region) has a higher melting point. The heat pressing temperature is set between these melting points to achieve bonding without excessive melting and void formation
Solution Approach 2:
The tubular member uses a composite structure with multiple resin types (resin L and resin H) with different thermal properties. This composite material approach allows simultaneous achievement of bonding strength (through resin L melting) and void prevention (through resin H remaining solid)
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
This approach ensures good sealability of spaces within the tubular member by preventing excessive resin melting and internal pressure buildup, thereby maintaining effective sealing of injection ports.
Implementation Method 1
a step of welding the tubular member and the laminate film by causing the laminate film to contact the tubular member and carrying out heat pressing from the laminate film side
Implementation Method 2
the resin that is in the vicinity of the surface thereof that contacts the laminate film is melted by the heat pressing
Data Source
AI summary
A method of manufacturing a power storage device, which has a battery, injection ports, a tubular member surrounding the injection ports, and a laminate film, includes a step of causing the laminate film to contact the tubular member and welding by heat pressing. At the tubular member, a first region including a surface that contacts the laminate film is structured by resin L, and a second region that is disposed further toward the injection ports side than the first region and that contacts the first region is structured by resin H. At the laminate film, a third region including a surface that contacts the tubular member is structured by resin lam. Melting points Tm or glass transition temperatures Tg of the resin L and the resin lam are lower than that of the resin H. A temperature of the heat pressing is greater than or equal to the melting point Tm or the glass transition temperature Tg of the resin L and the resin lam, and is less than the melting point Tm or the glass transition temperature Tg of the resin H.