Efficient battery supercapacitor hybrid devices with quaternary metal oxide electrodes based on nickel and cobalt

Enhancing redox reactions and electrical conductivities is indispensible to design efficient electrocapacitive materials for battery supercapacitor hybrid devices (BSH). Nickel cobalt molybdenum quaternary metal oxides based on Al, Cu, Fe, and Zn are synthesized on Ni foam via a facile hydrothermal reaction and applied as the electrocapacitive material for battery-type electrodes. Structure and electrocapacitive performance for quaternary metal oxides are highly dependent on metal species. The best electrocapacitive performance is attained for the nickel cobalt molybdenum copper oxide electrode due to the preferable nanosheet structure with high surface area and compatibility between Ni, Co, Mo and Cu. An areal capacity of 0.78 mAh/cm² is obtained at 10 mV/s for the optimized nickel cobalt molybdenum copper oxide electrode prepared using the Cu ratio of 1.0. A BSH composed of the nickel cobalt molybdenum copper oxide positive electrode and an activated carbon negative electrode presents an areal capacity of 1.57 mAh/cm² at 10 mA/cm² with a potential window of 1.4 V and the capacitance retention of 70% after 4000 times repeatedly charge/discharge process. The successful synthesis of novel quaternary metal oxides with highly efficient electrochemical performance provides new blueprints for improving the electrocapacitive ability of BSH by applying multiple metal oxides with careful-designed compositions.