Battery Restricting Structure for Swelling-Induced Short Prevention
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Solution Overview
Problem
Lithium-ion secondary batteries face the risk of short circuits between positive and negative electrodes due to laminate swelling, which existing technologies fail to adequately prevent.
Innovation Solution
The battery design includes a laminate structure with alternately arranged first and second electrodes separated by separators, where first tabs protrude from the first electrodes and are connected at a specific distance, and exterior materials with spacers to manage swelling, ensuring the laminate thickness remains within a specific range to prevent contact between electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the laminate is allowed to swell freely, then the battery can accommodate volume changes during charge-discharge cycles, but the positive and negative electrodes may come into contact causing short circuits
Solution Approach 1:
A restricting structure is introduced as an intermediary element between the swelling laminate and the electrode tabs. This structure selectively restricts the swelling movement in the thickness direction while allowing the laminate to expand in other directions, thereby preventing tab-to-electrode contact without compromising the battery's charge-discharge functionality
Solution Approach 2:
The restricting structure is pre-installed in a position that anticipates and counteracts the swelling force before short circuit can occur. The structure is designed with specific geometric parameters (distance from separator end, protrusion distance) that create a physical barrier against the electrode tabs during swelling, preventing harmful contact before it happens
2Reliability
If pressure is applied between electrodes to suppress swelling, then laminate expansion is controlled, but the complexity of the battery structure increases
Solution Approach 1:
The restricting structure is segmented into multiple functional zones: a base portion positioned at a specific distance from the separator end, and a protruding portion that extends toward the electrode tabs. This segmentation allows each zone to perform its specific function - the base portion provides anchoring while the protruding portion provides the actual restriction - simplifying the overall design compared to a monolithic pressure-applying mechanism
Solution Approach 2:
Instead of applying pressure in the planar direction between electrodes, the restricting structure utilizes the thickness dimension by protruding from the laminate surface. This dimensional approach allows swelling restriction without requiring complex inter-electrode pressure mechanisms, thereby reducing structural complexity
Data Source
AI summary
In an initial state, a battery is in the following state. A laminate has a thickness T0 from a first electrode to a first electrode. A first position is spaced from the end portion of a separator on the first position side by a distance L0 in a direction perpendicular to a thickness direction of the laminate. The end portion of a separator on the first position side protrudes toward the first position from the end portion of the second electrode on the first position side, by a distance G in the direction perpendicular to the thickness direction of the laminate. The laminate is designed such that, even if the laminate swells in the thickness direction of the laminate, the thickness of the laminate from the first electrode to the first electrode is smaller than 4×{(T0/2)2+L02−(L0−G)2}1/2.