Passivated Aluminum Busbar Assembly for Corrosion-Resistant Battery Modules
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Solution Overview
Problem
The aluminum/copper connections in battery modules are prone to electrochemical corrosion and resistance growth, leading to premature aging of battery cells, and existing solutions involving nickel-tin coatings are costly due to the need for surface processing before welding.
Innovation Solution
A battery module with a busbar featuring a purposely passivated surface, comprising a conversion coating such as zirconium, fluorine, and chromium, which allows for direct assembly without expensive surface processing steps, ensuring corrosion resistance and high surface conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Ni-Sn coating is applied to the busbar to prevent electrochemical corrosion, then corrosion resistance is improved, but the coating must be removed prior to welding which increases manufacturing complexity and cost
Solution Approach 1:
The patent changes the material parameter of the coating from Ni-Sn to a phosphate-based conversion coating. This chemical composition change allows the coating to remain on the busbar surface during welding without causing porosity or welding defects, eliminating the need for pre-welding surface removal steps while maintaining corrosion protection
Solution Approach 2:
The phosphate-based conversion coating is a thin, cost-effective layer that provides sufficient corrosion protection without requiring removal. It acts as a disposable protective barrier that can withstand the welding process, eliminating expensive surface preparation steps
2Reliability
If a Ni-Sn coating is applied to the busbar to ensure electrical conductivity, then electrical conductivity is improved, but the coating causes porosity in laser welding which degrades the electrical connection
Solution Approach 1:
The patent changes the coating material from Ni-Sn to a phosphate-based conversion coating with different chemical and physical properties. This new coating material is compatible with laser welding processes, allowing high-quality welds to be formed without porosity while maintaining electrical conductivity through the coating layer
3Manufacturing precision
If the busbar surface is left uncoated to enable direct welding, then welding quality is improved, but electrochemical corrosion occurs at the aluminum/copper connection
Solution Approach 1:
The phosphate-based conversion coating acts as an intermediary layer between the aluminum busbar surface and the welding process. It provides a surface that is both weldable and corrosion-resistant, mediating between the conflicting requirements of direct welding and corrosion protection
Solution Approach 2:
The patent creates a composite surface structure on the busbar by applying a phosphate-based conversion coating. This composite material combines the advantages of both coated and uncoated surfaces, providing both weldability and corrosion resistance in a single integrated solution
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
The passivated surface coating provides long-lasting high surface conductivity and corrosion resistance, improving the quality of welding and extending the lifespan of battery cells by preventing premature aging.
Implementation Method 1
Aluminum/copper connection is prone to electrochemical corrosion and resistance growth
Implementation Method 2
the busbar comprises a purposely passivated surface... provides electrically conductive but also a corrosion resistant coating
Implementation Method 3
said conversion coating improves the quality of welding, especially laser welding, where the busbar is welded to the terminal, since oxides and water on the surfaces are substantially avoided
Data Source
Figure 1~3
AI summary
A battery module (100) and a battery (200), comprising at least one battery module (100). The battery module comprises plurality of battery cells (1), the battery cell comprising a terminal (2) made of aluminium or aluminium alloy, and a busbar (3) made of aluminium or aluminium alloy, the busbar being arranged for interconnecting terminals (2) in a same electrical polarity of said plurality of battery cells (1) in an electrically conductive way. The busbar (3) is further arranged for connecting the plurality of battery cells to an electrical conductor element (4) made of copper or copper alloy. The busbar (3) comprises a purposely passivated surface (5).