Sheet-Type Cell Sealing Using a Peripheral Separator Weld
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Solution Overview
Problem
The existing sheet-type cells face challenges in productivity due to poor sealing properties at the thermally welded portions, which can lead to moisture intrusion, and require additional components like ionomer films. Additionally, the roll-to-roll method for manufacturing these cells is hindered by the need for precise positioning of the separator, reducing productivity.
Innovation Solution
A sheet-type cell design that includes an outer case with thermally fusible resin layers and a separator made of a porous resin sheet. The method involves thermally welding the outer case members with the separator interposed between them, and optionally using a water repellent membrane to enhance sealing and prevent moisture intrusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrode terminals are interposed in the thermally welded portion between outer case members, then electrical connection is achieved, but sealing properties deteriorate
Solution Approach 1:
The separator is divided into a battery electrode-facing portion and an outer case-facing portion, with the outer case-facing portion extending to the periphery to be interposed between outer case members. This segmentation allows the separator to provide both electrical isolation function and sealing function, eliminating the need for additional ionomer films while maintaining good sealing properties.
Solution Approach 2:
The separator is designed to perform multiple functions: it provides electrical isolation between electrodes, allows ion transport, and simultaneously provides sealing by having its outer case-facing portion extend to the periphery and be interposed between outer case members during thermal welding. This multi-functionality reduces device complexity by eliminating additional sealing components.
2Reliability
If separator positioning accuracy is improved, then sealing properties improve, but productivity decreases
Solution Approach 1:
The separator is pre-formed with an outer case-facing portion that has a specific size and shape matching the outer case members before assembly. This preliminary preparation ensures that when the separator is placed in the battery, its outer case-facing portion automatically extends to the correct periphery position, facilitating easy interposition between outer case members during thermal welding without requiring high positioning accuracy during assembly, thus improving productivity while maintaining sealing properties.
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 design improves the sealing properties of the sheet-type cell, reduces the need for additional components, and enhances the accuracy of separator positioning, thereby increasing the productivity of the manufacturing process.
Implementation Method 1
Each outer case member includes a thermally fusible resin layer. A periphery of the first outer case member and a periphery of the second outer case member are sealed by thermally welding, with a periphery of the separator interposed between the peripheries of the first and second outer case members.
Implementation Method 2
Each outer case member includes a thermally fusible resin layer
Data Source
AI summary
A sheet-type cell disclosed in this application includes an outer case and a power generation element contained in the outer case. The power generation element includes a positive electrode, a negative electrode, a separator, and an electrolyte solution. The separator is constituted by a porous resin sheet. The outer case includes a first outer case member and a second outer case member. Each outer case member includes a thermally fusible resin layer. The first outer case member and the second outer case member are disposed on respective opposite sides of the power generation element. A periphery of the first outer case member and a periphery of the second outer case member are sealed by thermally welding, with a periphery of the separator interposed between the peripheries of the first and second outer case members.