Flexible and anti-freezing quasi-solid-state zinc ion hybrid supercapacitors based on pencil shavings derived porous carbon

Abstract

Aqueous zinc-ion batteries have been widely reported as promising candidates for energy storage, but the research on zinc-ion based supercapacitors or hybrid supercapacitors has received little attention and the energy storage mechanism is still controversial. Here, a high-performance zinc-ion hybrid supercapacitor is successfully demonstrated with biowaste-derived porous carbon and cheap zinc foil. Thanks to the bivalent characteristic of zinc and electric double layer capacitive nature of porous carbon, as-assembed hybrid supercapacitors can achieve high energy density of 147.0 ​Wh kg−1 at 136.1 ​W ​kg−1 and a maximum power density of 15.7 ​kW ​kg−1 at 65.4 ​Wh kg−1 together with outstanding cycling stability (92.2% capacity retention after 10000 cycles at a high current density of 10 ​A ​g−1). Most importantly, 61.6% of the initial capacity at 1 ​A ​g−1 can be remained even under a mass loading as high as 17 ​mg ​cm−2. Significantly, the phase composition of byproducts formed in Zn(CF3SO3)2 electrolyte have been confirmed by ex-situ experimental results and theoretical calculations. Besides, when appling optimized carbon cathode into quasi-solid-state hybrid supercapacitors with a unique anti-freezing hydrogel electrolyte, this device can well service at various bending states and relatively low temperature of −15 ​°C.