Novel synthesis of polyaniline, manganese oxide and nickel sulfide lavandula-like composites as efficient active material of supercapacitor

Transition metal sulfides (TMS) are considered as the efficient battery-type material due to high theoretical capacity, redox reversibility, and electrical conductivities. The Ni₃S₂ with a high theoretical capacity and abundant sources is one of the efficient energy storage materials, but high contact resistances and poor cyclic stability of Ni₃S₂ restrict its electrochemical performance. The binder-free design, morphology regulation, composite development, and conductive polymer incorporation are useful strategies for solving the problems of Ni₃S₂. In this study, a novel lavandula-like manganese oxide, Ni₃S₂ and polyaniline composite (PANI/MnO_x/Ni₃S₂) is synthesized on Ni foam as the binder-free battery-type electrode of battery supercapacitor hybrid (BSH) as clean energy sources at the first time. The Mn amounts and aniline electropolymerization durations play important roles on active sites and electrical conductivity. The functions of MnO_x and PANI are analyzed by comparing physical and electrochemical properties of Ni₃S₂, MnO_x/Ni₃S₂, PANI, PANI/Ni₃S₂ and PANI/MnO_x/Ni₃S₂ electrodes. The largest specific capacitance (C_F) of 9.5 F/cm² at 30 mA/cm² is achieved for the optimized PANI/MnO_x/Ni₃S₂ electrode. A BSH assembled using activated carbon and PANI/MnO_x/Ni₃S₂ electrodes presents the maximum energy density of 2.31 Wh/m² at 65 W/m², and the C_F retention of 78.5 % and Coulombic efficiency of 95.8 % after 10,000 times repeatedly charging and discharging process.