Bimetallic chalcogenides have attracted much research interest as potential electrode materials for supercapacitor applications. This is because of their multiple oxidation states, higher electronic conductivity, better electroactivity, and structural stability. Recent studies point to the prospects of Ni-Co-based materials for supercapacitor applications.
In this work, bimetallic Ni-Co materials are chosen as the ‘base material’. Bimetallic chalcogenides: NiCo2X4, where X = O, S, Se, Te, were used as electrodes in supercapacitor devices. Asymmetric devices (Battery-supercapacitor hybrid energy storage systems) were fabricated for each chalcogenide material. NiCo2O4 proved the best electrode material, delivering a maximum energy density of 34 Wh kg-1 and power density of 6000 W kg-1. This was followed by NiCo2Te4, delivering a maximum power density of 11250 W kg-1 and energy density of 22 Wh kg-1[1].
Going further, nickel cobalt oxide and nickel cobalt telluride phases were doped to improve their electrochemical energy storage properties. In particular, NiCoOxNy (bimetallic oxynitride) and Cr-doped Ni-Co telluride nanostructures, unexplored as supercapacitor electrodes, were prepared and used as positive electrodes to fabricate the hybrid supercapacitor devices, respectively.
Interestingly our findings show that NiCoOxNy nanostructures as supercapacitor electrode materials exceed the supercapacitive performance of all oxynitrides reported thus far. An asymmetric device fabricated using NiCoOxNy nanostructures can deliver an energy density of 53 Wh kg-1 and a maximum power density of 24 kW kg-1.[2]
Cr-doped Ni-Co telluride nanostructures-based asymmetric supercapacitor device can deliver a maximum energy density of 32 Wh kg-1 and a maximum power density of 18 kW kg-1 with cyclic stability of 81% after 10000 cycles.
The activated carbon used in the above cases for asymmetric device fabrication is derived from biosource precursors. Symmetric supercapacitor device fabricated thus delivers a maximum power density of 5000 W kg-1 with 98% capacitance retention after 5000 cycles.[3]
This combination of results, i.e., new Ni-Co nanostructures and pericarp-derived activated carbons for making hybrid devices, means that the area has been nudged forward rather substantially through this work.

References
[1] M.L. Aparna, T. Thomas, G.Ranga. Rao, Battery-like supercapacitive behavior of urchin-shaped NiCo2O4 and comparison with NiCo2X4 (X = S, Se, Te), J. Electrochem. Soc. 169 (2022) 020515. https://doi.org/10.1149/1945-7111/ac4d6c.
[2] M.L. Aparna, G.Ranga. Rao, T. Thomas, Chimie douce derived Nickel Cobalt Oxynitride as Electrode Material for High Energy Density Supercapacitors, Electrochim. Acta. 418 (2022) 140341. https://doi.org/10.1016/j.electacta.2022.140341.
[3] M.L. Aparna, G.Ranga. Rao, T. Thomas, Momordica Charantia pericarp derived activated carbon with dual redox additive electrolyte for high energy density supercapacitor devices, J. Energy Storage. 48 (2022) 104048. https://doi.org/10.1016/j.est.2022.104048.