Journal
ACS SUSTAINABLE CHEMISTRY & ENGINEERING
Volume 6, Issue 1, Pages 1208-1214Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acssuschemeng.7b03492
Keywords
Activated carbon; Supercapacitors; Functional groups; Leakage current; Gas evolution; Aging
Categories
Funding
- Ministry of Science and Technology (MOST) of Taiwan
- China Steel Corporation of Taiwan
- NSF [ECCS-1610806]
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The concentrations of surface functional groups on activated carbon (AC) are manipulated via heat treatment at various temperatures. The carboxyl (O-C = 0) population clearly decreases at 600 degrees C, whereas the lactone (RO-C = 0) and phenol (C-OH) populations decrease if the temperature exceeds 750 degrees C. Their effects on electrode capacitance, leakage current, and gas evolution are systematically investigated in 1 M tetraethylammonium tetrafluoroborate/propylene carbonate electrolyte. The assembled symmetric supercapacitors are also subjected to an aging test, where the cells are held at 2.5 V and 70 degrees C. The decreased functional group populations significantly reduce gassing and improve the cell durability; the mechanisms are explored using electrochemical impedance spectroscopy and post-mortem SEM. Nevertheless, the AC surface area drops dramatically at 850 degrees C, resulting in a considerable reduction in capacitance. A rational control of heat-treatment temperature is critical for obtaining AC with balanced supercapacitor performance.
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