Design of high-performance binary carbonate/hydroxide Ni-based supercapacitors for photo-storage systems

Silicon solar cells were used to convert solar energy into electrical energy, and a supercapacitor was designed to store this energy. To maximize the surface area of the electrodes, a three-dimensional Ni foam substrate was employed, onto which Ni-based compounds were deposited to enhance the electrochemical performance of the electrodes. Specifically, to address the conductivity reduction problem that arises when using only Ni ions, we introduced transition metal ions such as Mn, Co, Cu, Fe, and Zn to create binary compounds as electrode material. These binary metal compounds provided high electronic conductivity, structural stability, and reversible capacity, thereby optimizing the performance of the supercapacitor. As a result, the optimized NiCo(CO₃)(OH)₂ electrode demonstrated high capacity and excellent cycle stability, exhibiting an energy density of 35.5 Wh kg⁻¹ and a power density of 2555.6 W kg⁻¹ as an asymmetric supercapacitor device. Furthermore, when this device was combined directly with silicon solar cells, it achieved a storage efficiency of 63 % and an overall efficiency of 5.17 % under an illumination intensity of 10 mW cm⁻². These findings suggest the potential for commercializing high-performance self-charging energy storage devices and contribute significantly to the advancement of energy storage technology.