Battery Pack Asymmetric Fusion Welding and Chamfered Corners
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Solution Overview
Problem
Lithium ion battery packs using laminate film casing materials face reliability issues due to corner portion breakage and electrolyte leakage when subjected to vibrations, leading to increased production costs from extensive chamfering required to mitigate this problem.
Innovation Solution
The battery pack design incorporates chamfered corner portions only on the second end portion with a shorter fusion-welding length, while maintaining longer fusion-welding lengths on the first end portion, and uses a holder member with specific tab configurations to connect unit batteries in series, ensuring mechanical and electrical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chamfering is applied to all corner portions of unit batteries, then reliability against vibration is improved, but production cost and process complexity increase
Solution Approach 1:
The patent applies chamfering only to specific corner portions (second end portion corners) rather than all corners of the unit battery. This localized approach addresses the vibration-induced breakage problem at critical locations while avoiding unnecessary processing at other corners, thereby maintaining reliability without increasing overall production complexity.
Solution Approach 2:
The patent divides the corner protection strategy into segments by identifying which specific corners (second end portion corners) require chamfering based on their susceptibility to vibration damage. This segmented approach allows selective application of the chamfering process only where needed, reducing total process complexity while maintaining effectiveness.
2Reliability
If chamfering is applied to all corner portions of unit batteries, then reliability against vibration is improved, but production time and cost increase
Solution Approach 1:
By applying chamfering only to the second end portion corners where vibration-induced breakage occurs most frequently, the patent reduces the total number of corners requiring processing. This localized treatment maintains vibration resistance reliability while decreasing production time and cost compared to universal chamfering of all corners.
Solution Approach 2:
The patent implements partial chamfering action by treating only the critical second end portion corners rather than all corners. This partial action is sufficient to prevent the majority of vibration-induced failures while significantly reducing the time and cost investment compared to complete chamfering of all corner portions.
3Strength
If longer fusion-welding length is used at first end portion, then mechanical strength is improved, but device complexity increases due to asymmetric design
Solution Approach 1:
The patent creates asymmetric fusion-welding lengths where the first end portion has a longer weld length for enhanced mechanical strength, while the second end portion has a shorter weld length. This local differentiation optimizes strength at the critical first end portion without requiring symmetric complexity throughout the entire casing structure.
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 enhances the reliability of the battery pack by preventing corner breakage and electrolyte leakage during vibrations without significantly increasing production processes, thus maintaining efficiency and reducing costs.
Implementation Method 1
chamfered portions, which are positioned at both corner portions of the second end portion
Implementation Method 2
a first fusion-bonding portion, which has a first fusion-welding length in a direction in which a tab is pulled out at a first end portion's side
Data Source
Figure 1~2
Figure 3
Figure 4(A)~4(D)
AI summary
In order to provide a highly-reliable battery back in which a laminate film of a unit battery does not break through a laminate film of an adjacent unit battery even under vibration, a battery pack of the present invention is characterized by including a plurality of unit batteries 100 connected in series, the unit batteries 100 including: a positive-electrode pulled-out tab 120 and a negative-electrode pulled-out tab 130; and a laminate casing member that is provided with a first end portion 111, from which the positive-electrode pulled-out tab 120 and the negative-electrode pulled-out tab 130 are pulled out, a second end portion 112, which faces the first end portion 111, a first fusion-bonding portion 117, which has a first fusion-welding length in a direction in which a tab is pulled out at a first end portion 111's side, a second fusion-bonding portion 118, which has a second fusion-welding length that is shorter than the first fusion-welding length in a direction in which a tab is pulled out at a second end portion 112's side, and chamfered portions 119, which are positioned at both corner portions of the second end portion 112.