EV Battery Cell Tabs for Wire Bonding and Sealing
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Solution Overview
Problem
The challenge in assembling lithium ion battery cells into a battery pack for electric vehicles lies in forming a suitable surface for wire bonding, as the crimped areas on the battery cell terminals often become curved or sloped due to crimping, making it difficult to achieve a secure bond while also ensuring a seal with the gasket, which can lead to material strain and weakened housing.
Innovation Solution
The battery cell design incorporates an uneven rim pattern with peak and valley regions to create tabs that are crimped to form flat areas for wire bonding, allowing for a secure seal with a gasket and reducing material strain, using a housing with an uneven rim pattern that is crimped to create flat crimped areas with a surface area between 1 and 5 square millimeters, facilitating both effective sealing and bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the housing is crimped to seal with the gasket, then the seal reliability is improved, but the crimped area becomes curved or sloped making wire bonding difficult
Solution Approach 1:
The rim of the housing is segmented into multiple tabs separated by valley regions, allowing each tab to be independently crimped. This segmentation enables the crimping force to be distributed across multiple discrete points rather than creating a continuous curved surface, thereby maintaining flat bonding surfaces while achieving effective sealing where the tabs contact the gasket.
Solution Approach 2:
Different portions of the housing rim are given different local qualities: the tab regions are designed to remain relatively flat for wire bonding, while the valley regions between tabs are designed to deform and engage with the gasket for sealing. This local differentiation allows simultaneous achievement of flat bonding surfaces and effective seals.
2Reliability
If the crimping force is increased to ensure sealing, then the seal quality is improved, but the material strain increases and the housing becomes weakened
Solution Approach 1:
By dividing the sealing interface into multiple discrete tabs rather than a continuous crimped surface, the total crimping force is distributed across multiple separate contact points. This reduces the strain concentration in any single region of the housing, preventing material weakening while still achieving adequate sealing at each tab-gasket interface.
Solution Approach 2:
The crimping action is applied partially - only to the extent needed to engage the tabs with the gasket for sealing, rather than continuously crimping the entire rim. The valley regions are designed to accommodate the necessary deformation for sealing without requiring excessive force that would weaken the housing structure.
3Reliability
If the crimped area is made larger to provide sufficient bonding surface, then the wire bonding reliability is improved, but the material strain and housing weakening increase
Solution Approach 1:
The bonding surface is segmented into multiple discrete flat areas on individual tabs rather than requiring a single large continuous bonding zone. Each tab provides a sufficient flat area for wire bonding (1-5 square millimeters), and the distributed arrangement of multiple tabs achieves reliable electrical connections without requiring large-scale material deformation that would weaken the housing.
Data Source
AI summary
A battery cell for an electric vehicle battery pack can include a housing and a gasket. The housing can define a sidewall of the battery cell that extends between an open end of the housing and a closed end of the housing. The open end of the housing can include an uneven rim pattern having a plurality of peak regions and a plurality of valley regions to define a plurality of tabs. The plurality of peak regions can engage the gasket to seal the housing with the gasket. Each of the plurality of tabs can define a respective flat crimped area. Each flat crimped area can have a surface area between one square millimeter and five square millimeters. At least one of the flat crimped areas can provide a surface for bonding with a wire.