Flat Secondary Battery Extending Part Geometry for Uniform Pressure
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Solution Overview
Problem
Existing flat secondary batteries face issues with uniform pressure distribution due to electrode expansion during charge and discharge cycles, leading to ununiform cell reactions and poor durability.
Innovation Solution
A flat secondary battery design featuring a laminate-type power generation element sealed by a pair of exterior members with specific geometric relationships between the extending part, sealing part, and thickness, ensuring uniform pressure distribution and improved durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the battery uses a laminate exterior case to seal the power generation element, then the battery achieves compact structure and good sealing, but when electrodes expand during charge and discharge, ununiform pressure is applied to the power generation element leading to poor durability
Solution Approach 1:
The exterior case is designed with different structural zones: a first extending part that extends in the thickness direction to provide buffering space for electrode expansion, and a second extending part that extends in the radial direction to maintain sealing. This local differentiation allows different parts of the case to perform different functions, preventing ununiform pressure while maintaining overall structural integrity.
Solution Approach 2:
The exterior case is divided into multiple extending parts (first extending part and second extending part) with different orientations and functions. The first extending part handles thickness-direction expansion while the second extending part handles radial sealing, segmenting the pressure management function to avoid ununiform stress distribution.
2Stability of the object's composition
If the exterior case is made rigid to maintain structural stability, then sealing is improved, but the case cannot accommodate electrode expansion leading to ununiform pressure and reduced durability
Solution Approach 1:
The exterior case incorporates extending parts that can dynamically adjust to electrode expansion. The first extending part extends in the thickness direction to accommodate volume changes during charge-discharge cycles, while the second extending part maintains radial sealing. This dynamic structure adapts to electrode movement without compromising overall stability.
Solution Approach 2:
Different regions of the exterior case have different degrees of flexibility: the first extending part provides flexibility in the thickness direction to accommodate expansion, while the second extending part provides rigidity in the radial direction for sealing. This local quality differentiation resolves the contradiction between rigidity and adaptability.
3Device complexity
If the battery design does not account for interior space during electrode expansion, then the initial structure is simpler, but repeated charge and discharge cause case deformation and ununiform pressure
Solution Approach 1:
The exterior case is pre-designed with extending parts that create interior space before electrode expansion occurs. The first extending part extends in the thickness direction and the second extending part extends in the radial direction,预先 providing accommodation space for electrode volume changes during charge-discharge cycles, preventing case deformation.
Solution Approach 2:
The extending parts utilize both the thickness direction (first extending part) and radial direction (second extending part) to create three-dimensional interior space. This multi-dimensional space management accommodates electrode expansion more effectively than single-direction design, improving durability without excessive complexity.
Data Source
AI summary
A flat secondary battery has a laminate-type power generation element in which two or more plate-like electrodes are laminated via each of separators; and a pair of rectangular exterior members when viewed from a lamination direction of the two or more electrodes, the rectangular exterior members sealing the laminate-type power generation element and an electrolyte solution. At least one exterior member of the pair of the rectangular exterior members comprises: an abutting part including an abutting surface that abuts against an uppermost layer electrode of the two or more electrodes; a sealing part at which the rectangular exterior members overlap each other at an outer circumferential position of the rectangular exterior members; and an extending part that extends from the abutting part to the sealing part, and the flat secondary battery satisfies:1.03≤Lb2+d2≤1.22