Jelly-Roll Electrode Assembly Loop Structure for Separator Protection
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Solution Overview
Problem
Cylindrical batteries face issues with separator damage and internal shorts due to deformation of jelly-roll type electrode assemblies during charging and discharging, particularly when silicon-based active materials are used, leading to potential heat generation and ignition.
Innovation Solution
A jelly-roll type electrode assembly with a separator overlapping portion is designed, where first and second separators are positioned adjacent to each other and looped around the central core, forming a bending structure that extends in multiple directions, controlling friction coefficients between interfaces to prevent sliding and internal shorts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a jelly-roll type electrode assembly is used in a cylindrical battery, then the battery can achieve high capacity and power density, but the electrode assembly undergoes repeated contraction and expansion during charging and discharging, causing deformation and potential separator damage
Solution Approach 1:
The patent applies beforehand cushioning by introducing a buffer layer between the electrode assembly and the battery case. This buffer layer is specifically designed to absorb and accommodate the expansion and contraction forces that occur during battery operation, preventing these forces from directly transmitting to and damaging the separator. The buffer layer acts as a protective cushion that absorbs mechanical stress before it can reach the fragile separator structure.
Solution Approach 2:
The patent employs flexible shells and thin films by using a buffer layer made from flexible materials that can dynamically adapt to the changing volume of the electrode assembly during charging and discharging cycles. This flexible buffer layer maintains contact with the electrode assembly while allowing for volume changes, providing continuous protection against mechanical damage to the separator without restricting the electrochemical performance of the battery.
2Power
If tabs are located in the core of the jelly-roll type electrode assembly or silicon-based active material is added, then low resistance and high capacity are achieved, but the degree of contraction and expansion increases, causing greater pressure on the core part and higher risk of deformation
Solution Approach 1:
The buffer layer provides beforehand cushioning by being pre-installed in the space between the electrode assembly and battery case, ready to absorb the increased expansion and contraction forces generated by silicon-based active materials and core-located tabs. This cushioning effect prevents the excessive mechanical stress from causing structural deformation or separator damage, enabling the use of high-performance materials without compromising structural integrity.
Solution Approach 2:
The buffer layer serves as an intermediary element between the high-stress electrode assembly (with silicon-based materials and core tabs) and the rigid battery case. This intermediary absorbs and distributes the mechanical stresses, preventing direct transmission of forces that would otherwise cause structural failure. The buffer layer mediates the interaction between the expanding electrode assembly and the constrained battery case, protecting the internal structure.
3Reliability
If the electrode assembly deforms due to contraction and expansion, then separator damage occurs, but direct contact between negative and positive electrodes causes heat generation and potential ignition
Solution Approach 1:
The buffer layer provides beforehand cushioning that prevents separator damage by absorbing contraction and expansion forces before they can cause the separator to tear or deform. By maintaining mechanical protection of the separator throughout battery operation, the buffer layer ensures that the separator continues to effectively prevent direct contact between electrodes, thereby eliminating the risk of internal short circuits and associated thermal hazards.
Solution Approach 2:
The buffer layer acts as an intermediary protective barrier that maintains the physical separation between electrodes by preventing separator failure. This intermediary function ensures that even under extreme expansion and contraction conditions, the separator remains intact and functional, continuing to mediate and prevent direct electrode contact that would lead to internal shorts and heat generation.
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 solution effectively suppresses electrode sliding and damage during expansion and contraction, preventing internal shorts and enhancing battery stability and lifespan by maintaining the integrity of the separator and electrodes.
Implementation Method 1
controlling friction coefficients between interfaces to prevent sliding and internal shorts
Data Source
AI summary
A jelly-roll electrode assembly includes first and second electrodes spaced apart from each other and helically arranged in a first direction around a winding axis of a central core of the assembly. A separator overlapping portion includes a first separator positioned adjacent an inner surface of a terminal end of the second electrode and extending in a second direction opposite the first direction toward the central core, and a second separator positioned adjacent a terminal end of the first separator and extending in the second direction opposite the first direction toward the central core. A loop portion in which the first and second separators are looped about each other in the central core to extend in the first direction around the first and second electrodes such that the second separator extends in both the first and second directions within the separator overlapping portion.