One-Step Solid Phase Synthesis of NiCo₂Se₄/Carbon Nanotube Nanocomposites for Hybrid Supercapacitors and Sodium-Ion Batteries

To overcome the inherent drawbacks of traditional solid-phase synthesis methods, this paper reported an in situ solid-phase synthesis method for preparing NiCo 2 Se 4 /carbon nanotube (NiCo 2 Se 4 /CNT) nanocomposite. By this method, NiCo 2 Se 4 nanospheres are loaded onto the surface and inside the 3D conductive framework constructed by CNTs. This unique morphology provides conductivity and structural stability to the synthesized nanocomposite, resulting in good rate capability and cycling performance in both hybrid supercapacitor and sodium-ion battery applications. The hybrid supercapacitor device based on the synthesized nanocomposite can deliver an energy density of 33.32 Wh kg –1 at a power density of 0.844 kW kg –1 while retaining 67.5% of energy density at a high power density of 11.73 kW kg –1 . After 20 000 cycles, the energy density still reaches 91.6% of that in the initial cycle. When employed as an anode material for SIBs, the synthesized nanocomposite exhibits a high reversible specific capacity of 367.1 mAh g –1 with a Coulombic efficiency of 99.27% after 300 cycles at 0.1 A g –1, while 91.3% of the specific capacity is retained as the current density rises from 0.1 to 3 A g –1 . After 500 cycles at a current density of 2.0 A g –1, the reversible specific capacity of the synthesized nanocomposite reaches 319 mAh g –1 with a very low specific capacity attenuation of 0.021% per cycle. The developed method contributes to reducing the cost of preparing TMSe-based electrode materials while achieving high performance, thus boosting its application in electrochemical energy storage systems.