Secondary Battery Positive Electrode Turn-Up Prevention
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Solution Overview
Problem
The existing methods for manufacturing lithium ion batteries can result in an outwardly turned-up state of the positive electrode during the winding process, leading to potential internal short circuits when the turned-up portion breaks through the separator and contacts the negative electrode.
Innovation Solution
A secondary battery design that includes a positive electrode with a band shape and a negative electrode, both wound with a separator in a spiral shape, featuring a positive electrode active material uncovered part that protrudes and is bent towards the central axis, with a cutout at one end to prevent the turned-up portion from contacting the negative electrode, and joined to a current collector plate to suppress internal short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the positive electrode is wound in a spiral shape with the negative electrode and separator, then the battery structure is compact and efficient, but the positive electrode may turn up outwardly during winding or conveyance, causing it to break through the separator and contact the negative electrode
Solution Approach 1:
The protruding part of the positive electrode is formed in advance during the electrode manufacturing process, before winding. This preliminary formation ensures that when the electrode is wound and subjected to pressing forces during battery assembly or conveyance, the protruding part absorbs the stress and prevents the positive electrode from turning up outwardly and contacting the negative electrode through the separator.
Solution Approach 2:
The positive electrode is designed with non-uniform structure: a protruding part extends beyond the negative electrode at one end, while the rest of the electrode maintains normal winding structure. This local modification creates a stress-absorbing feature that prevents internal short circuits without affecting the overall compactness and efficiency of the battery structure.
2Reliability
If the turned-up portion of the positive electrode is prevented by adding structural features, then internal short circuits are suppressed, but the electrode structure becomes more complex
Solution Approach 1:
The protruding part is formed during the electrode manufacturing process using conventional techniques such as slitting or punching. By performing this action preliminarily, the electrode is pre-configured to accommodate winding stresses, eliminating the need for complex post-winding adjustments or additional structural features that would require higher manufacturing precision.
Data Source
AI summary
A battery is provided that suppresses the occurrence of an internal short circuit due to a turned-up portion generated in a positive electrode. A secondary battery includes an electrode wound body, a positive electrode current collector plate, and an outer package can. The electrode wound body includes a positive electrode having a band shape and a negative electrode having a band shape, the positive electrode and the negative electrode being in a stacked arrangement with a separator interposed therebetween, and being wound. The outer package can contains the electrode wound body and the positive electrode current collector plate. The positive electrode includes a positive electrode active material covered part in which a positive electrode foil is covered with a positive electrode active material layer, and a positive electrode active material uncovered part. The secondary battery includes a flat surface formed by the positive electrode active material uncovered part that protrudes from one end of the electrode wound body being bent toward a central axis of the electrode wound body and portions of the positive electrode active material uncovered part overlapping each other. The flat surface is joined to the positive electrode current collector plate. The positive electrode active material uncovered part has a cutout at one end on an outer periphery side of the electrode wound body.