Power Storage Device Current Collector Stress Reduction
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Solution Overview
Problem
Increasing the capacity of stacked power storage cells by enlarging the active material layers leads to wrinkles and tears in the current collectors due to expansion and contraction during charging and discharging, as the non-adhesive portions of the current collectors are subjected to increased stress.
Innovation Solution
Incorporating a spacer between the current collectors to form a sealed space and chamfering the corners of the active material layers to reduce stress concentration, with a radius of curvature of 5 mm or more, which distributes the stress over a wider area and prevents wrinkles and tears.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the area of each active material layer is increased to increase the capacity of power storage cells, then the capacity is improved, but wrinkles and tears are easily formed in the current collectors due to increased stress during expansion and contraction
Solution Approach 1:
The corners of the active material layer are rounded with a radius of curvature of 5 mm or more, eliminating sharp corners that concentrate stress. This curvature distribution reduces the maximum stress concentration during expansion and contraction of the active material layer, preventing wrinkles and tears in the current collector while maintaining large active material area for high capacity
Solution Approach 2:
The non-adhesive portion of the current collector is designed with specific dimensions (L1/L2 ratio of 0.02 or less) to optimize its mechanical properties. By controlling the size and shape of the non-adhesive portion locally, the design allows sufficient deformation space to accommodate active material expansion while preventing stress concentration that would lead to structural failure
2Quantity of substance
If the area of each active material layer is increased to increase the capacity, then the capacity is improved, but the deformation amount of the non-adhesive portion increases leading to higher load and easier formation of wrinkles and tears
Solution Approach 1:
Rounded corners with radius of curvature of 5 mm or more distribute the expansion force over a wider area, reducing the peak load on the non-adhesive portion of the current collector while accommodating the necessary deformation for high-capacity active material layers
Data Source
AI summary
A power storage device includes a first electrode including a first active material layer formed on a first surface, a second electrode including a second active material layer formed on a first surface, a separator, and a spacer. The first active material layer has a longitudinal side of a first length. The second area has a second length between the spacer and the first active material layer. A ratio of the second length to the first length is 0.02 or less. At least one of corners of the first active material layer has a shape chamfered in an arc shape. A radius of curvature at a portion of the corner having a maximum curvature is 5 mm or more.