Supercapacitor Electrode Pre-Treatment for Outgassing Reduction
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Solution Overview
Problem
Supercapacitors employing ionic liquid electrolytes tend to outgas during charging and discharging cycles, leading to safety concerns, especially when used in lightweight, flexible forms, as they can expand and potentially burst due to the release of gases like hydrogen, carbon monoxide, and carbon dioxide, which arise from the decomposition of residual water and organic components.
Innovation Solution
Pre-treating the carbon-containing electrodes with a tetrafluoroborate salt, an ionic liquid quaternary salt, at temperatures between 0°C to 100°C, while applying varying potential differences across the electrodes during charge and discharge cycles, repeated multiple times to reduce outgassing, ensuring the maximum voltage does not exceed the electrolyte's electrochemical window.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If ionic liquid electrolytes are used in supercapacitors, then charge-holding capacity and charging voltage are improved, but outgassing occurs during charging and discharging cycles
Solution Approach 1:
The electrodes are pre-treated with a tetrafluoroborate salt before the supercapacitor is used for significant charge-storing duty. This preliminary action modifies the electrode surface to prevent outgassing during subsequent charging and discharging cycles, while maintaining the charge-holding capacity provided by the ionic liquid electrolyte.
Solution Approach 2:
The method involves applying varying potential differences across the electrodes during charge and discharge cycles at controlled temperatures (0°C to 100°C). By cycling the voltage and temperature parameters, the electrode surface is conditioned to reduce outgassing while preserving the electrochemical performance of the ionic liquid electrolyte.
2Weight of moving object
If lightweight, flexible pouch construction is used, then device portability is improved, but safety risk increases due to pouch expansion from outgassing
Solution Approach 1:
The electrodes undergo pre-treatment with tetrafluoroborate salt and multiple charge-discharge cycling before the supercapacitor is sealed in the flexible pouch. This preliminary conditioning eliminates the source of outgassing (decomposition of residual water and organic components), thereby preventing pouch expansion and maintaining safety while allowing the use of lightweight flexible construction.
3Object-generated harmful factors
If multiple charge-discharge cycling is performed during pre-treatment, then outgassing is reduced, but manufacturing time increases
Solution Approach 1:
The pre-treatment process uses varying potential differences and temperature conditions (0°C to 100°C) during charge-discharge cycling. By optimizing these parameters, the method achieves effective outgassing reduction in 10-60 cycles, balancing the trade-off between thorough treatment and manufacturing efficiency.
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
Substantially reduces outgassing from the supercapacitor system, allowing for the use of lightweight, flexible materials without the risk of pouch expansion, as the water content is minimized, thereby enhancing safety and performance in consumer electronics.
Implementation Method 1
contacting the carbon-containing electrodes with a tetrafluoroborate salt that is an ionic liquid
Implementation Method 2
applying a varying potential difference across the carbon-containing electrodes whilst in the presence of the salt in a cycle during which electrical charge is stored on and discharged from the electrodes
Implementation Method 3
the maximum voltage applied during each cycle does not exceed the upper limit of the electrochemical window of the electrolyte
Data Source
AI summary
A method of reducing outgassing in a supercapacitor comprised of carbon-containing electrodes and at least one ionic liquid is characterised by the steps of (a) contacting the carbon-containing electrodes with a tetrafluoroborate salt; (b) applying a potential difference across the carbon- containing electrodes whilst in contact with the salt in a cycle during which electrical charge is stored on and discharged from the electrodes; and (c) continuing further cycles of step (b) until such time as substantially no further outgassing from the system occurs.