Jelly-Roll Electrode Assembly with Ceramic Separator
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Solution Overview
Problem
Lithium ion secondary batteries face limitations in ion conductance and electrode separation due to thickening and increased resistance when using conventional ceramic separators, leading to reduced capacity and risk of short circuits, especially at high temperatures.
Innovation Solution
A jelly-roll wound electrode assembly with a ceramic separator and interposed porous polymer separation films at specific curvature points and terminal portions to prevent exfoliation and maintain electrode separation, ensuring efficient lithium ion movement and preventing short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ceramic separator is used to prevent short circuits and improve heat resistance, then safety and heat resistance are improved, but the electrode assembly thickness increases and resistance increases
Solution Approach 1:
The separator system is segmented into multiple functional layers: a ceramic-containing heat-resistant layer for safety and a porous polymer layer for ion transport. This segmentation allows each layer to specialize in its function without requiring excessive thickness in any single layer, resolving the contradiction between safety and thickness.
Solution Approach 2:
The separator uses composite materials combining ceramic particles (for heat resistance) with porous polymer matrices (for ion conductance). This composite structure achieves both safety requirements and low resistance without increasing overall thickness, as the ceramic provides thermal stability while the porous polymer maintains ion transport pathways.
2Reliability
If the area of active material on electrodes is expanded to overcome low ion conductance, then ion conductance is improved, but the electrode assembly becomes more complex and harder to manufacture
Solution Approach 1:
The separator employs porous polymer materials with optimized pore structures that enhance ion transport efficiency. This allows adequate ion conductance without requiring excessive expansion of active material areas, simplifying electrode manufacturing while maintaining performance.
3Reliability
If a polyolefin based separator is used to provide safety through aperture closure at high temperature, then safety function is improved, but the separator is damaged at temperatures over 200°C causing short circuits
Solution Approach 1:
The separator combines polyolefin-based porous polymer materials with ceramic particles. The ceramic component maintains structural integrity at temperatures exceeding 200°C, preventing the separator damage and short circuits that occur with pure polyolefin separators, while the polyolefin matrix still provides the aperture closure safety function at lower temperatures.
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 maintains electrode assembly thickness and prevents increased resistance, enhancing lithium ion mobility and safety by reducing the risk of short circuits, even at high temperatures, while maintaining battery capacity.
Implementation Method 1
porous polymer separation films interposed between the two opposing electrodes at portions of the electrodes which have relatively small radii of curvature
Implementation Method 2
a ceramic separator formed on at least one surface among the four surfaces of the two electrodes and disposed between the two opposing electrodes
Implementation Method 3
a separator aperture, (a cavity area per unit volume or a porosity in a certain section of the separator)
Data Source
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AI summary
A lithium ion secondary battery and a jelly-roll type electrode assembly in a lithium ion secondary battery including a can and a cap assembly together with the electrode assembly. The electrode assembly is made up of two electrodes; a ceramic separator coating on at least one surface among the four surfaces of the two electrode plates and located between the two opposing electrodes; and porous polymer resin separation films placed between the electrode plates at certain locations where the plates are bent to relatively small radii of curvature and outward from an innermost portion of a core, and/or at terminal ends of the electrode plates, respectively.