Wound Secondary Battery Electrode End Structure for Short-Circuit Reliability
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Solution Overview
Problem
Secondary batteries face insufficient operational reliability due to issues with electrode alignment and stress distribution, leading to potential short circuits during charging and discharging.
Innovation Solution
A secondary battery design featuring a columnar shape with a wound electrode configuration where the negative electrode's leading end is bent towards the center, creating recessed parts to mitigate internal stress and prevent buckling, thereby enhancing operational reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the electrodes are wound tightly to increase energy density, then the battery size is reduced, but internal stress increases causing electrode buckling and potential short circuits
Solution Approach 1:
The patent applies adhesive tape to the back surface of the negative electrode plate at the start end part before winding occurs. This preliminary action prevents the negative electrode from buckling during the winding process and maintains proper electrode alignment, thereby preventing short circuits while allowing tight winding for compact battery size.
Solution Approach 2:
The adhesive tape serves as an intermediary element between the negative electrode plate and the winding structure. It provides mechanical support and constraint to the negative electrode during winding, preventing buckling and maintaining alignment without requiring the electrode itself to be structurally modified.
2Reliability
If the separator is bonded extensively to the positive electrode to prevent short circuits, then reliability improves, but device complexity increases
Solution Approach 1:
The patent bonds the separator only to a specific local region of the positive electrode - namely the region from the end of the positive electrode mixture layer to a length corresponding to at least one loop in the winding direction. This localized bonding approach prevents short circuits in the critical area while avoiding the complexity of extensive bonding across the entire electrode surface.
Data Source
AI summary
A secondary battery includes an outer package member and a battery device. The outer package member has a columnar shape. The battery device is contained inside the outer package member and includes a first electrode and a second electrode. The first electrode and the second electrode are opposed to each other and wound. The first electrode includes a leading end part located on a side close to a center of the battery device. The leading end part is wound once or more on a side closer to the center of the battery device than the second electrode, and includes one or more bent parts. In the one or more bent parts, the leading end part is bent to be partly recessed toward the center of the battery device.