Rounded Pouch Battery Case Geometry to Prevent Molding Cracks

The punch edges and corners are designed with rounded geometries having specific curvature radii. The first punch edge has a first curvature radius, the second punch edge has a second curvature radius, and the punch corner has a third curvature radius that is larger than both the first and second curvature radii. This curvature design distributes stress during elongation, preventing stress concentration that causes cracks and whitening in the pouch film.

Different regions of the punch are given different curvature radii tailored to their specific stress conditions. The punch corner, which experiences the highest stress concentration during elongation, is given the largest curvature radius (third curvature radius). The punch edges have smaller curvature radii (first and second curvature radii) appropriate for their lower stress environments. This localized differentiation of geometric properties optimizes stress distribution across the entire pouch film surface.

By providing rounded punch edges and corners with appropriately sized curvature radii, the elongation process becomes more uniform and controlled. The pouch film stretches evenly across the cup part surface without developing localized stress concentrations that would cause cracks or whitening. This enables sufficient accommodation space to be achieved while maintaining surface quality.

The curvature radii of the punch features are specifically optimized to control the elongation behavior of the pouch film. By adjusting these geometric parameters (first, second, and third curvature radii), the process achieves the necessary volume expansion for adequate accommodation space while preventing the formation of defects through controlled stress distribution.

The rounded punch features with optimized curvature radii distribute applied stress more uniformly across the thin pouch film during elongation. This prevents stress concentration at sharp edges and corners, which would be particularly problematic for thin films. As a result, compact batteries using thin pouch films can be manufactured without suffering from cracking or whitening defects.

The punch design provides locally optimized curvature radii that account for the reduced thickness of the pouch film. The larger third curvature radius at the punch corner specifically addresses the heightened vulnerability of thin films to stress concentration at corner regions, enabling reliable manufacturing of compact batteries with minimal film thickness.