Tubular Cellulose Separator for Ionic Liquid Power Storage
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Solution Overview
Problem
Lithium-ion secondary batteries using organic solvents are prone to volatility and flammability, leading to potential explosions and corrosion due to hydrofluoric acid production, and side reactions with separators can degrade the battery's cycle performance.
Innovation Solution
A power storage device design where the separator is not in contact with the current collector, allowing it to be impregnated with an ionic liquid, reducing the likelihood of side reactions and maintaining the non-volatility and non-flammability of the ionic liquid, thus preventing degradation and enhancing safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the separator is made thin to reduce device thickness, then the power storage device becomes easier to bend and lighter, but the separator may come into contact with the current collector surface, causing side reactions and degradation
Solution Approach 1:
The separator is designed with a tubular structure that extends in the radial direction rather than only the thickness direction. This dimensional change allows the separator to effectively surround the electrode while maintaining adequate spacing from the current collector surface, preventing contact-induced degradation even in thin-profile devices.
Solution Approach 2:
The tubular separator is positioned concentrically around the electrode, creating a nested configuration where the separator fits within the overall device structure without contacting the current collector. This nesting approach maximizes space utilization while maintaining protective separation.
2Object-affected harmful factors
If an ionic liquid is used as electrolyte to achieve non-volatility and non-flammability, then safety is improved, but side reactions between the separator and ionic liquid or current collector may occur, degrading the power storage device
Solution Approach 1:
The tubular separator acts as an intermediary barrier between the ionic liquid electrolyte and the current collector electrode. This intermediate structure prevents direct contact and potential side reactions between the ionic liquid and current collector surface, thereby maintaining cycle performance while preserving the safety benefits of ionic liquids.
Solution Approach 2:
The invention extracts the problematic interaction interface between the separator and current collector by designing a tubular separator configuration that eliminates surface contact. This separation removes the source of side reactions while maintaining the essential functions of both components.
3Device complexity
If the separator is in contact with the current collector surface, then the device structure is simplified, but side reactions occur causing color change and degradation of the separator
Solution Approach 1:
The separator transitions from a flat planar structure to a tubular three-dimensional structure. This dimensional change allows the separator to effectively surround the electrode while maintaining spatial separation from the current collector surface, preventing contact-induced degradation without significantly increasing overall 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 solution results in a safer, more reliable power storage device with improved cycle performance and reduced risk of short-circuits, maintaining the non-volatile and non-flammable properties of the ionic liquid, while preventing reaction products that could degrade the battery.
Implementation Method 1
an ionic liquid, unlike a polymer solid electrolyte and the like, is a substance with which a separator can be impregnated. Impregnation reduces the thickness of a power storage device.
Data Source
AI summary
When cellulose is used as a separator, the cellulose is impregnated with an ionic liquid. Charge and discharge are repeated with this separator touching a surface of a current collector; then, the separator is changed in color. Thus, it is an object to provide a power storage device with a structure in which a side reaction other than a battery reaction, e.g., a change in color of separator, is unlikely to occur. In the power storage device, a separator impregnated with an ionic liquid is not in contact with a surface of a current collector. The separator has a tubular shape, a bag-like shape, or a sheet-like shape. The separator includes cellulose. The power storage device including the ionic liquid is non-volatile and non-flammable. The power storage device can be bent.