Battery Negative Terminal Structure for Stable Dissimilar-Metal Welding
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Solution Overview
Problem
The challenge of achieving strong connections between bus bars and negative terminals in battery assemblies, particularly when the terminals are formed from dissimilar metals, is exacerbated by misalignment and manufacturing tolerances, leading to reduced thickness and potential formation of intermetallic compounds that weaken the joint.
Innovation Solution
A method involving the use of a welding assist member, made of the same metal as the second metal section, inserted into a recessed portion of the negative terminal, which is formed by dissimilar metal joining, to stabilize the connection during laser welding of the bus bar.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the negative terminal is formed from two dissimilar metals joined together to improve connection strength with the bus bar, then the joining strength between the bus bar and negative terminal is improved, but the thickness of the negative terminal in the welded portion is reduced and a recessed portion is formed
Solution Approach 1:
The recessed portion is formed in advance during the dissimilar metal joining process, before the laser welding of the bus bar. This preliminary formation of the recessed portion allows the laser beam to accurately strike the joint surface without being obstructed by thickness variations, preventing misalignment and ensuring proper welding position.
Solution Approach 2:
The recessed portion acts as an intermediary feature that mediates between the dissimilar metal joining process and the subsequent laser welding process. It provides a controlled geometry that guides the laser beam to the correct position on the joint surface, eliminating the harmful effect of thickness reduction.
2Ease of manufacture
If laser welding is performed on the negative terminal with the recessed portion, then the bus bar can be joined to the negative terminal, but misalignment may cause the laser to strike the recessed portion, resulting in heat reaching the joint surface between dissimilar metals and forming intermetallic compounds that reduce joining strength
Solution Approach 1:
The recessed portion is preliminarily formed to serve as a positioning feature that guides the laser beam. This preliminary geometric configuration ensures that even with normal manufacturing tolerances and misalignment, the laser will strike the recessed portion first and then correctly position on the joint surface, preventing direct overheating of the dissimilar metal interface.
Solution Approach 2:
The recessed portion provides a cushioning effect by absorbing excess laser energy and providing a transition zone. It acts as a buffer that prevents the laser from directly striking the joint surface between dissimilar metals, thereby preventing the formation of intermetallic compounds that would reduce joining strength.
3Strength
If the negative terminal is formed from dissimilar metals to achieve firm joining with aluminum bus bar, then the connection strength is improved, but the device complexity increases due to the need for dissimilar metal joining process
Solution Approach 1:
The negative terminal is designed with local quality differentiation: the lower part uses copper alloy for excellent electrical conductivity and corrosion resistance, while the upper part uses aluminum alloy for lightweight and cost-effectiveness. This localized material selection optimizes performance for each specific function while maintaining overall connection strength.
Solution Approach 2:
The negative terminal is constructed as a composite structure using dissimilar metals (copper alloy and aluminum alloy) joined together. This composite approach combines the advantages of different materials to achieve optimal electrical conductivity, mechanical strength, and cost-effectiveness, while the recessed portion design simplifies the subsequent laser welding process.
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
Enhances the joining strength and reduces the formation of intermetallic compounds, minimizing manufacturing failures and improving corrosion resistance while allowing for flexible manufacturing methods.
Implementation Method 1
joining the bus bar onto the joint surface of the negative terminal by laser welding
Implementation Method 2
When the laser strikes the recessed portion due to misalignment, heat can easily reach a joint surface between the dissimilar metals in the negative terminal
Data Source
AI summary
In a battery assembly including a first battery and a second battery, the first battery includes a negative terminal, and the negative terminal has a first metal section and a second metal section formed of a metal different from the first metal section. The second metal section is joined to the top of the first metal section with the dissimilar metal joining, and the second metal section is formed with a joint surface and a recessed portion. A method of manufacturing the battery assembly includes a process of inserting a welding assist member into the recessed portion, and a process of placing a bus bar on the joint surface of the negative terminal in which the welding assist member is inserted in the recessed portion, and joining the bus bar onto the joint surface of the negative terminal by laser welding.