The binder-free mesoporous CoNi2S4 electrode for high-performance symmetric and asymmetric supercapacitor devices

Mixed metal sulphides have attracted the attention of researchers working in the development of electroactive materials for high-energy supercapacitors. Mesoporous CoNi 2 S 4 nanostructures have been grown on Ni-foam via an efficient single-step hydrothermal process. The performance of CoNi 2 S 4 nanostructures was compared with pristine Ni 3 S 4 and Co 3 S 4 -CoS nanostructures which has been prepared using the same approach. The CoNi 2 S 4 nanostructures with diverse morphology reveal a high surface area (87.8 m 2 g −1 ), large specific capacity (1117 C g −1 ) and low charge transfer resistance (0.3 Ω). The admirable features enable shortening of electrolyte ion diffusion pathway and quick electron transport and increase effective electroactive sites facilitating improved energy storage. The CoNi 2 S 4 electrode-based asymmetric supercapacitor yields a large energy density of 87.4 W h kg −1 with a power density of 1250 W kg −1 and retains 80% of capacity at the end of 5000 cycles. Graphical Abstract