Cylindrical Secondary Battery Spring Structure for Swelling Control
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Solution Overview
Problem
Lithium secondary batteries experience significant volume expansion during charging and discharging, particularly with lithium metal negative electrodes, leading to performance deterioration and structural instability.
Innovation Solution
Incorporating a flat spiral spring between the electrode assembly and the cylindrical case of the battery, which applies uniform pressure to stabilize the electrode assembly and suppress volume expansion, using multiple spiral springs with varying spring constants to manage shape distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a lithium metal negative electrode is used to achieve high energy density, then the energy storage capacity is improved, but the volume expansion during charging and discharging increases significantly
Solution Approach 1:
The patent applies preliminary anti-action by pre-installing a spiral spring around the electrode assembly before it undergoes volume expansion. The spring is positioned and tensioned in advance to exert a counteracting force that will resist the swelling phenomenon when lithium metal deposits and expands during charging, thereby preventing structural damage and maintaining battery integrity.
Solution Approach 2:
The spiral spring serves as a beforehand cushioning mechanism that absorbs and mitigates the impact of volume expansion. By placing the spring in advance around the electrode assembly, the system creates a cushioning effect that gradually absorbs the expansion stress during charging and discharging cycles, protecting the battery structure from sudden or excessive volume changes.
2Reliability
If the electrode assembly is allowed to expand freely during charging, then the lithium metal deposition is maintained, but the structural stability of the battery deteriorates
Solution Approach 1:
The patent applies parameter changes by modifying the mechanical constraints on the electrode assembly through the spiral spring. The spring changes the physical parameters of the system by introducing a controlled restraining force that limits the maximum expansion volume while still allowing the necessary lithium metal deposition to occur, thereby maintaining both charging reliability and structural stability.
3Stability of the object's composition
If a flat spiral spring is added to suppress volume expansion, then the structural stability is improved, but the device complexity increases
Solution Approach 1:
The patent employs a flexible spiral spring as a thin-walled elastic component that provides structural support and volume control. This flexible element maintains structural stability through its elastic properties while occupying minimal space and adding relatively simple geometry to the battery design, thus improving stability without significantly increasing device complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The flat spiral spring effectively stabilizes the electrode assembly, allowing for reversible charging and discharging while minimizing shape distortion and improving space utilization.
Implementation Method 1
a flat spiral spring which surrounds the electrode assembly and is positioned between the outer peripheral surface of the electrode assembly and the inner wall of the cylindrical case
Data Source
AI summary
A secondary includes an electrode assembly having a jelly roll structure including a positive electrode sheet, a negative electrode sheet, and a separator; a cylindrical case in which the electrode assembly is received; and a flat spiral spring positioned between an outer peripheral surface of the electrode assembly and an inner surface of the cylindrical case.