Rounded Pouch Battery Cup Geometry for Crack-Free Forming
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Solution Overview
Problem
During the molding process of pouch-type secondary batteries, stress concentration at the edges and corners of the pouch film leads to cracks and whitening, reducing the durability of the battery case.
Innovation Solution
The pouch-type battery case is designed with a cup part that includes rounded punch edges, thickness edges, and corners, with curvature radii that differ from each other, to disperse stress and prevent cracking and whitening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If drawing molding is performed by applying pressure to elongate the pouch film using a punch, then the cup part is formed, but stress concentration occurs at edges and corners causing cracks and whitening
Solution Approach 1:
The punch edges and corners are designed with rounded curvature instead of sharp angles. Specifically, the punch has rounded edges with a first curvature radius and rounded corners with a second curvature radius that is larger than the first. This curvature design distributes the stress during drawing molding more evenly across the pouch film, preventing stress concentration at edges and corners, thereby eliminating cracks and whitening while maintaining the ability to form the cup part.
2Shape
If the pouch film is elongated during press processing, then the cup part shape is achieved, but cracks and whitening occur due to stress concentration
Solution Approach 1:
The punch is designed with rounded edges and corners having different curvature radii. The rounded edges have a first curvature radius while the rounded corners have a second curvature radius larger than the first. This graduated curvature approach allows the pouch film to elongate and form the cup part geometry smoothly without creating stress concentration points, thus preventing cracks and whitening while achieving the desired shape.
Solution Approach 2:
Different parts of the punch have different curvature radii tailored to their specific functions. The edges have a smaller curvature radius suitable for forming straight edges, while the corners have a larger curvature radius to prevent stress concentration at the most vulnerable points. This localized differentiation of geometric properties optimizes both the forming quality and the integrity of the pouch film during elongation.
Data Source
AI summary
A pouch-type secondary battery according to an embodiment of the present invention for solving the above problems includes a cup part configured to accommodate an electrode assembly formed by stacking electrodes and separators, wherein the cup part includes: a bottom portion configured to form a bottom; an outer wall configured to form a side surface and meet the bottom portion; a punch edge configured to connect the bottom portion to the outer wall; a thickness edge configured to connect two adjacent outer walls to each other; and a corner formed by connecting the two adjacent punch edges to the thickness edge, wherein at least one of the punch edges is rounded, at least one of the thickness edge is rounded, at least one of the corner is rounded and has a curvature radius different from that of each of the punch edge and the thickness edge.