Wound Secondary Battery Groove Structure for Short-Circuit Prevention
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Solution Overview
Problem
Lithium ion batteries face issues with internal short circuits due to stress on the electrode winding body during high rate discharge, causing deformation and peeling of active materials, which can lead to internal short circuits.
Innovation Solution
A secondary battery design where strip-shaped positive and negative electrodes with active material covered and non-covered portions are stacked and wound with a separator, and the non-covered portions are joined to current collector plates, forming a flat surface with a groove to prevent stress and peeling, thereby avoiding internal short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the active material non-covered portion is densely disposed at an inner peripheral portion of the electrode winding body and pressed to form a flat surface, then the current collector plate can be welded, but stress increases causing electrode deformation and active material peeling leading to internal short circuit
Solution Approach 1:
The patent applies local quality by creating a groove at the inner peripheral portion of the electrode winding body where stress concentrates. This groove locally modifies the structure to reduce stress concentration, preventing electrode deformation and active material peeling at the critical inner peripheral region while maintaining the overall flat surface for current collector plate welding
Solution Approach 2:
The patent segments the inner peripheral portion of the electrode winding body by forming a groove that divides the continuous structure. This segmentation releases stress concentration at the inner peripheral portion, preventing the propagation of stress that would otherwise cause electrode deformation and active material peeling
2Power
If high rate discharge is implemented to achieve high output, then power delivery is improved, but stress on electrode winding body increases causing deformation and peeling
Solution Approach 1:
The patent applies beforehand cushioning by pre-forming a groove at the inner peripheral portion of the electrode winding body before high rate discharge operations. This groove structure anticipates and cushions against the stress concentration that occurs during high rate discharge, preventing electrode deformation and active material peeling even under high power output conditions
Data Source
AI summary
Disclosed is a secondary battery in which a positive electrode active material non-covered portion is joined to a positive electrode current collector plate at one end portion of an electrode winding body, a negative electrode active material non-covered portion is joined to a negative electrode current collector plate at the other end portion of the electrode winding body, the electrode winding body has a flat surface formed by bending any one or both of the positive electrode active material non-covered portion and the negative electrode active material non-covered portion toward central axis of wound structure and overlapping the positive electrode active material non-covered portion and the negative electrode active material non-covered portion, and a groove formed in the flat surface, the positive electrode has a positive electrode cut-out portion at one end in a transverse direction of the positive electrode on a winding start side of the electrode winding body.