Prismatic Battery Case Anodizing for Laser Welding
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Solution Overview
Problem
The manufacturing process of prismatic batteries is complex due to the use of insulative tapes with low mechanical strength, which can damage protection circuit modules and affect dimensional stability, and the surface treatment of battery cases complicates laser welding, while lithium secondary batteries face safety issues from combustible materials and require additional safety elements that complicate assembly.
Innovation Solution
Anodizing the entire surface of the battery case with an uncoated margin section allows easy laser welding of the cap plate and improves durability, and a connection opening section is formed at the bottom for stable charging, reducing the number of parts and simplifying assembly, while minimizing the height of safety elements to increase energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If surface treatment is carried out on the battery case, then durability and corrosion resistance are improved, but laser welding cannot be satisfactorily carried out
Solution Approach 1:
The battery case is divided into two functional zones: an upper portion with surface treatment for durability and a lower uncoated margin section for welding. This segmentation allows each zone to fulfill its specific function without interference from the other treatment type.
Solution Approach 2:
Different surface properties are applied to different locations of the battery case. The upper portion receives anodizing or other surface treatments for corrosion resistance, while the lower margin section remains uncoated to provide optimal laser welding characteristics. This local differentiation resolves the contradiction between durability and weldability.
2Reliability
If insulative tapes are used to seal the battery case, then sealing is achieved, but mechanical strength is low and dimensional stability is affected
Solution Approach 1:
The insulative tape sealing method is completely removed from the system. Instead, the battery case uses its own structurally reinforced sealed portion that provides both sealing and mechanical strength without requiring additional insulative tapes, thereby eliminating the weakness associated with tape-based sealing.
3Reliability
If the battery case is completely anodized, then durability is improved, but laser welding of the cap plate becomes difficult
Solution Approach 1:
The anodizing treatment is segmented to cover only the upper portion of the battery case, deliberately leaving the lower margin section uncoated. This allows the anodized portion to provide durability while the uncoated margin enables proper laser welding of the cap plate.
Solution Approach 2:
The surface treatment is applied locally rather than uniformly across the entire battery case. The anodizing is confined to areas where durability is needed, while welding areas maintain their original surface properties for optimal laser absorption and weld quality.
4Reliability
If safety elements are added to control abnormal states, then safety is improved, but assembly complexity increases
Solution Approach 1:
Multiple safety functions are merged into integrated safety elements that combine protection circuit modules, PTC elements, and sealing functions into unified components. This integration reduces the number of separate parts and simplifies assembly while maintaining comprehensive safety coverage for overcharge, overcurrent, and thermal protection.
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 method enhances durability and corrosion resistance of the battery case, simplifies the assembly process, and increases battery capacity by allowing easier laser welding and reducing the height of safety elements, thereby improving the safety and energy density of secondary battery packs.
Implementation Method 1
anodizing an entire surface of the battery case
Implementation Method 2
connecting a cap plate to an open upper end of the battery case by laser welding
Data Source
Figure 1
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Figure 4~5
AI summary
Disclosed herein is a method of manufacturing a battery cell having an electrode assembly of a cathode/separator/anode structure disposed in a battery case made of aluminum or an aluminum alloy together with an electrolyte in a sealed state, the method including (a) anodizing an entire surface of the battery case in a state in which an uncoated margin section having a predetermined length is provided downward from an outer circumference of an upper end of the battery case, (b) mounting the electrode assembly in the battery case and connecting a cap plate to an open upper end of the battery case by laser welding, (c) injecting an electrolyte through an electrolyte injection port of the cap plate and activating the battery cell, and (d) replenishing the electrolyte and sealing the electrolyte injection port.