Boosting the volumetric energy of supercapacitors using polytetrafluoroethylene pyrolysis gas

摘要

Increasing the volumetric energy of carbon-based supercapacitors is of practical importance for the advancement of high-powered energy storage. Herein, we use the gases evolved from polytetrafluoroethylene pyrolysis at 800 degrees C to fluorine-dope an activated carbon, and directly synthesize a fluorine-doped highly porous graphite in the same environment. As supercapacitor materials in organic electrolyte, both resultant fluorine-doped carbons outperform their non-doped counterparts, delivering up to 40% gain in cell volumetric energy at high power cycling. F-doping increases volumetric capacitance (F cm(-3)) via increase in "real" areal capacity (uF cm(-2)) and/or increase in "real" volumetric surface area (m(2) cm(-3)), and increases electron conductivity. Considering current collector and separator volume fractions, cells containing the fluorine-doped activated carbon electrode films of 100 and 50 pm deliver an impressive 12.9 Wh L-1 at 0.1 kW L-1 and 6.7 Wh L-1 at 2.15 kW L-1 respectively. We conclude that the gas-based F-doping method affords an effective and less hazardous route to produce fluorine-doped carbons for increased volumetric energy storage.