Efficient coupling of MnO₂/TiN on carbon cloth positive electrode and Fe₂O₃/TiN on carbon cloth negative electrode for flexible ultra-fast hybrid supercapacitors

Recent research and development of energy storage devices has focused on new electrode materials because of the critical effects on the electrochemical properties of supercapacitors. In particular, MnO₂ and Fe₂O₃ have drawn extensive attention because of their low cost, high theoretical specific capacity, environmental friendliness, and natural abundance. In this study, MnO₂ ultrathin nanosheet arrays and Fe₂O₃ nanoparticles are fabricated on TiN nanowires to produce binder-free core-shell positive and negative electrodes for a flexible and ultra-fast hybrid supercapacitor. The MnO₂/TiN/CC electrode shows larger pseudocapacitance contributions than MnO₂/CC. For example, at a scanning rate of 2 mV s^-1, the pseudocapacitance contribution of MnO₂/TiN/CC is 87.81% which is nearly 25% bigger than that of MnO₂/CC (71.26%). The supercapacitor can withstand a high scanning rate of 5000 mV s^-1 in the 2 V window and exhibits a maximum energy density of 71.19 W h kg^-1 at a power density of 499.79 W kg^-1. Even at 5999.99 W kg^-1, it still shows an energy density of 31.3 W h kg^-1 and after 10 000 cycles, the device retains 81.16% of the initial specific capacitance. The activation mechanism is explored and explained.