Quadrangular Battery Lid Structure for Low-Stress Series Busbar Layout
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Solution Overview
Problem
Secondary batteries with shallow-drawn quadrangular battery cans face issues when connected in series, as the busbars may become larger or interfere with duct placement, and stress concentration occurs on welding beads under a restraining load.
Innovation Solution
The secondary battery design includes a flat quadrangular shallow-drawn battery can with a flange and a lid plate having a raised portion that extends outward beyond the outer edge, preventing adjacent lid plates from contacting and reducing stress on welding beads. The battery pack connects adjacent batteries in series with parallel busbars, avoiding interference with ducts and maintaining reduced stress on welding beads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If shallow-drawn quadrangular battery cans are used to make secondary batteries thinner and more adaptable to product applications, then the battery shape flexibility and thinness are improved, but stress concentration occurs on welding beads when batteries are connected in series under restraining load
Solution Approach 1:
The lid plate is segmented into two functional zones: a peripheral sealing region that contacts the battery can flange for welding, and a central raised portion that is elevated above the sealing surface. This segmentation allows the welding beads to form only on the flange surface while the raised portion remains stress-free, preventing stress concentration on the welding beads when restraining load is applied.
Solution Approach 2:
The lid plate transitions from a two-dimensional flat structure to a three-dimensional structure with a raised central portion. This dimensional change creates a vertical elevation that separates the central area from the sealing perimeter, allowing the welding beads to be confined to the flange level while the raised portion extends upward, thereby avoiding stress transmission to the welding beads.
2Ease of operation
If multiple secondary batteries are connected in series with crossed busbars to accommodate external terminals on side surfaces, then the battery pack configuration is achieved, but the busbars become larger and may interfere with duct placement
Solution Approach 1:
The external terminals are positioned asymmetrically on the battery can, with one terminal on the side surface and the other on the top surface near the flange. This asymmetric arrangement allows busbars to connect terminals of adjacent batteries in a linear sequence rather than requiring crossed configurations, reducing busbar dimensions and eliminating interference with duct placement.
Solution Approach 2:
Instead of placing both external terminals on the side surface of the battery can, the invention inverts the terminal placement strategy by positioning one terminal on the top surface near the flange. This alternative configuration enables simpler busbar routing that connects adjacent batteries linearly, avoiding the complexity and size issues of crossed busbar arrangements.
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 prevents busbar enlargement and interference with duct placement, while also reducing stress concentration on welding beads under a restraining load, enhancing the durability and performance of the battery pack.
Implementation Method 1
welding the press-fitted overlapping portion with a laser beam irradiated from above the lid plate
Data Source
Figure 1A~1B
Figure 2~3
Figure 4~5
AI summary
A quadrangular secondary battery includes a shallow-drawn battery can and a lid plate welded together for sealing. A battery pack includes such secondary batteries without causing a busbar to be larger or to interfere with duct placement and without causing stress concentration on welding beads under a restraining load. A secondary battery (1) includes an electricity generator, a metal battery can (3), a nonaqueous electrolyte, a metal lid plate (5), and a pair of external terminals (6, 7). The battery can (3) is quadrangular and shallow-drawn, accommodates the electricity generator placed laterally, and includes a flange (34) on a periphery of its opening. The nonaqueous electrolyte fills the battery can (3) accommodating the electricity generator. The lid plate (5) includes an outer edge (51a) welded to the flange (34) on the battery can (3) and covers the battery can (3). The lid plate (5) includes a raised portion (52) being flat and extending beyond the outer edge (51a) in an inner area of the outer edge (51a).