Folded Separator Electrode Assembly for Thermal Shrinkage Safety
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Solution Overview
Problem
Lithium secondary batteries face safety issues due to thermal contraction of separators in high-temperature environments, leading to electrical short circuits, ignition, and explosion, especially with cathode active materials containing high nickel content.
Innovation Solution
An electrode assembly design where first and second separators are adhered and folded to wrap the cathode and anode plates, with an insulating tape covering the folded parts to minimize thermal contraction and prevent electrical short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high-nickel cathode active material is used to increase capacity and voltage, then energy density is improved, but thermal stability deteriorates leading to safety issues
Solution Approach 1:
The separator is divided into multiple segments (first separator and second separator) that are adhered together. This segmentation allows each separator segment to independently manage thermal contraction, preventing complete collapse and maintaining safety even when using high-nickel cathode materials with low thermal stability.
Solution Approach 2:
The first and second separators are nested together through adhesion, creating a multi-layered separator structure. This nested configuration provides redundant protection against thermal contraction, ensuring that even if one separator layer contracts, the other layers maintain separation between electrodes.
2Use of energy by moving object
If separator is exposed to high-temperature environment, then battery capacity is improved, but thermal contraction occurs causing electrical short circuit
Solution Approach 1:
The adhesion structure of the first and second separators is established beforehand to cushion against future thermal contraction. This pre-configured adhesive bonding creates a buffer that absorbs the dimensional changes during high-temperature operation, preventing the separators from collapsing onto the electrodes.
Solution Approach 2:
The separator system combines multiple separator materials (first separator and second separator) with different thermal properties. This composite separator structure leverages the advantages of each material to resist thermal contraction while maintaining ion conductivity required for battery capacity.
3Device complexity
If single separator is used to simplify structure, then device complexity is reduced, but safety under high-temperature conditions deteriorates
Solution Approach 1:
Multiple separator functions are merged into a single integrated separator assembly through adhesion. The first and second separators are combined to work together as one unit, providing enhanced thermal resistance while maintaining a relatively simple overall structure that can be manufactured and assembled efficiently.
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
This design enhances the safety of lithium secondary batteries by reducing thermal contraction and electrical short circuits, even with high-nickel cathode active materials, while allowing smoother insertion into battery cases and improving the battery's high capacity and energy density.
Implementation Method 1
the issues related to the safety of the above-mentioned secondary battery, particularly, the high-temperature safety, are becoming more prominent... separators included in the electrode assembly are thermally contracted under exposure to a high-temperature environment
Data Source
AI summary
An electrode assembly and a secondary battery including the electrode assembly improve the safety of secondary batteries even under a high-temperature and heat-shrinkage environment of the separator. The electrode assembly includes a cathode plate, an anode plate corresponding to the cathode plate, and first and second separators that are disposed adjacent to each other with the cathode plate or the anode plate interposed therebetween. At least one end of the first separator is adhered to at least one end of the second separator along the longitudinal direction of the cathode plate and the anode plate. At least one end of the first and second separators is folded so as to form a folded part of the first and second separators and wrap the cathode plate or the anode plate. The electrode assembly further includes an insulating tape covering the folded part of the first and second separators.