Wide potential window TiO2@carbon cloth and high capacitance MnO2@carbon cloth for the construction of a 2.6 V high-performance aqueous asymmetric supercapacitor

Abstract

Flexible supercapacitors with aqueous electrolytes are attractive safe power sources; yet low specific capacitance and narrow operating voltage hinder their practical applications. Herein, we deposit arrays of TiO2 nanowires (TiO2@CC) and MnO2 nanosheets (MnO2@CC) on carbon cloth via a solution-based technique at 80 °C and in an open atmosphere. The TiO2 nanowires possess intrinsic low hydrogen evolution reaction activities and in turn a wide working window (−1.6–0 V vs. Hg/HgO). The high specific surface area and favorable pore texture endow the TiO2@CC and the MnO2@CC with high areal specific capacitances of 1204.8 mF cm−2 and 1427.2 mF cm−2, respectively. A 2.6 V wide potential window aqueous asymmetric supercapacitor is then constructed, which exhibits an exceptional high specific capacitance of 1010.8 mF cm−2, high volumetric energy density of 4.75 mW h cm−3 and volumetric power density of 325 mW cm−3. The areal energy density and areal power density are 0.949 mW h cm−2 and 65 mW cm−2, respectively. The excellent cyclic stability of 100% capacity retention after 50,000 cycles at a high current density of 5 mA cm−2 is recorded and the supercapacitor also exhibits good flexibility.