Structural characterization and electrochemical performance of Ni-doped Co9S8 for Li-ion battery and asymmetric supercapacitor dual applications

Development of nano-sized electrode materials with unique structural and electrical properties is urgently needed due to their vital roles in advanced energy storage systems. Adhering to that. Ni-doped Co9S8 nanoparticles were directly prepared by a facile solvothermal method for implementation as active anodes in rechargeable Li-ion batteries and supercapacitors. X-ray diffraction analysis using Rietveld method revealed a single Co9S8 phase with cubic structure (Fm (3) over barm), confirming the incorporation of Ni ions into the Co9S8 lattice replacing Co ions mainly at octahedral sites. The particle size and morphology were examined by HRTEM images taken at different magnifications. The XPS measurements verified the presence of Ni ions in the Co9S8 matrix and determined the cations oxidation states. The as-prepared nano-Ni@Co9S8 anode material delivered high discharge and charge capacities similar to 764 and 520 mAhg(-1), respectively in the initial cycle of Li-ion battery. The fabricated Ni@Co9S8 supercapacitor demonstrated good specific capacitance similar to 312 F g(-1) with high capacitance retention similar to 96% after 700 cycles which decreased to 206 F g(-1) after 1600 cycles. Meanwhile, a sharp loss in its capacitance by 36% was happened in the subsequent 900 cycles achieving about 206 F g(-1) after 1600 cycles.