Cylindrical Battery Electrode Layout for Swelling Stress Control
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Solution Overview
Problem
Conventional cylindrical batteries face issues with electrode symmetry and circularity degradation due to swelling, leading to core collapse and internal short circuits, especially when used in electric vehicles, due to uneven stress distribution and rotation of positive and negative electrodes.
Innovation Solution
The design optimizes the relative positions of positive and negative electrode ends within the electrode assembly, defining stress vulnerable and amplification regions to maintain symmetry and circularity, using a winding structure that spaces the outer circumference side end of the first electrode apart from the stress vulnerable region and fixes the outer circumference side end to the battery housing, with current collectors welded to bending surfaces to stabilize the electrodes during charging and discharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the electrode assembly is wound tightly to improve energy density, then the charging and discharging cycle increases, but the swelling phenomenon causes rotation of positive and negative electrodes, leading to core collapse and internal short circuits
Solution Approach 1:
The patent applies preliminary action by pre-positioning the outer circumference side ends of the positive and negative electrodes at specific locations before swelling occurs. The ends are positioned such that the negative electrode's outer circumference side end is located at a region that will accommodate expansion, while the positive electrode's outer circumference side end is positioned to prevent rotation. This preliminary positioning prevents core collapse and maintains electrode symmetry throughout the charging and discharging cycles, resolving the contradiction between high energy density and cycle stability.
2Productivity
If the outer circumference side ends of positive and negative electrodes are positioned close together to maximize space utilization, then manufacturing efficiency improves, but stress concentration occurs during swelling, causing electrode rotation and core collapse
Solution Approach 1:
The patent applies local quality by creating different spatial arrangements for the outer circumference side ends of the positive and negative electrodes. Specifically, the negative electrode's outer circumference side end is positioned at a location that accommodates swelling, while the positive electrode's outer circumference side end is positioned to prevent rotation. This differentiated local positioning prevents stress concentration and electrode rotation, maintaining structural integrity while allowing efficient manufacturing.
3Use of energy by moving object
If the electrode assembly allows natural swelling during charging and discharging, then electrochemical performance improves, but the positive and negative electrodes rotate relative to each other, causing loss of symmetry and circularity
Solution Approach 1:
The patent applies preliminary anti-action by pre-positioning the outer circumference side ends of the electrodes to counteract the rotational effect of swelling. The negative electrode's outer circumference side end is positioned to accommodate expansion, while the positive electrode's outer circumference side end is positioned to prevent rotation. This preliminary positioning creates a counter-balancing effect that maintains electrode symmetry and circularity even as the electrode assembly swells during charging and discharging, resolving the contradiction between electrochemical performance and shape maintenance.
Data Source
AI summary
A cylindrical battery includes an electrode assembly and a cylindrical battery housing. The electrode assembly includes a core and an outer circumference. The cylindrical battery includes a first fan-shaped region and a second fan-shaped region. The first fan-shaped region is surrounded by a first straight line and a second straight line passing from a center of the core through a core side end of the first and second electrodes, respectively, and the outer circumference is defined as a stress vulnerable region. The second fan-shaped region is surrounded by a third straight line and a fourth straight line passing from the center of the core through an outer circumference side end of the first and second electrodes, respectively, and the outer circumference is defined as a stress amplification region. A battery pack and vehicle including the same are also provided.