Composite Battery Separator for Rapid Thermal Shutdown
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Solution Overview
Problem
Existing non-aqueous electrolytic solution secondary batteries face challenges in rapidly and reliably shutting down ion migration between positive and negative electrodes during temperature increases, particularly when the amount of thermally expandable capsules is minimized to avoid performance degradation, and maintaining this shutdown state at high temperatures.
Innovation Solution
A composite separator is used, comprising a thermally expandable capsule sandwiched between two separator sheets, where the capsule expands two-dimensionally along the interface between the sheets, controlling its expansion direction to rapidly shut down ion migration and maintain the shutdown state even at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the amount of thermally expandable capsule is suppressed to avoid performance degradation, then battery performance in normal situation is improved, but the shutdown function speed and efficiency deteriorates
Solution Approach 1:
The patent transitions the capsule expansion from three-dimensional volumetric growth to two-dimensional planar expansion by sandwiching the capsule between separator sheets. This dimensional change allows the capsule to rapidly spread along the interface between separators, effectively blocking ion migration paths with smaller capsule quantities while maintaining shutdown efficiency.
Solution Approach 2:
The patent creates different functional zones by sandwiching the thermally expandable capsule between separator sheets, concentrating the shutdown function at the interface region where ion migration occurs. This localized quality enhancement allows efficient shutdown with minimal capsule material.
2Reliability
If thermally expandable capsule is used to shut down ion migration, then thermal runaway is suppressed, but the capsule expands in uncontrolled direction limiting shutdown efficiency
Solution Approach 1:
The patent constrains capsule expansion to two dimensions by sandwiching it between separator sheets, forcing the expansion to occur along the interface plane rather than in three-dimensional space. This dimensional control achieves precise expansion direction control for optimal shutdown efficiency while maintaining thermal runaway suppression.
Solution Approach 2:
The separator sheets act as intermediary structures that guide and control the expansion direction of the thermally expandable capsule. By positioning the capsule between the sheets, the separators mediate the expansion process, ensuring it proceeds in the desired planar direction for effective ion migration blocking.
3Reliability
If gas-forming agent is used to block ion migration path, then internal resistance increases and temperature increase is suppressed, but a large amount of gas is required and shutdown speed is limited
Solution Approach 1:
The patent utilizes the phase transition of the thermally expandable capsule (from condensed to expanded state) to block ion migration paths. This phase change mechanism generates the blocking effect directly without requiring large amounts of gas, achieving temperature increase suppression with minimal substance quantity while maintaining rapid shutdown speed.
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 composite separator effectively and reliably shuts down ion migration between electrodes at elevated temperatures, maintaining the shutdown state despite thermal fusion of the separators, even with reduced capsule usage, enhancing battery safety.
Implementation Method 1
the thermally expandable capsule expands during an increase in battery temperature, a space having no electrolytic solution is formed in the separator disposed between the electrodes, the migration of lithium ions is physically shut out
Implementation Method 2
a laminate formed of at least two separator sheets, in which a thermally expandable capsule is sandwiched in an interlayer of the laminate
Data Source
AI summary
Provided are a non-aqueous electrolytic solution secondary battery, a separator formed of the non-aqueous electrolytic solution secondary battery, and a method of manufacturing the non-aqueous electrolytic solution secondary battery. The non-aqueous electrolytic solution secondary battery includes a positive electrode, a negative electrode, and a composite separator that is disposed between the positive electrode and the negative electrode, in which in the composite separator, a thermally expandable capsule is sandwiched in an interlayer of a laminate formed of at least two separator sheets.