Hollow Bimetallic Phosphosulfide NiCo–P/S Nanoparticles in a CNT/rGO Framework with Interface Charge Redistribution for Battery-Type Supercapacitors

As remarkable pseudocapacitive materials with rich faradic redox reactions, Ni–Co bimetallic compounds have gained much research interest as high-performance battery-type supercapacitor electrodes. Herein, we report a strategy that can enhance the energy storage capability of supercapacitors by constructing bimetallic phosphosulfides via simultaneous phosphorization and sulfuration processes. Compared to a single phosphide, the bimetallic phosphosulfide of NiCo–P/S presented a highly porous and hollow nanoparticle structure, which renders more active electrochemical reactions. It is demonstrated that the coexistence of phosphide and sulfide phases can regulate charge distribution to improve electronic transportation capability. Besides, it is also proved that the precalcination of the NiCo-LDH precusor into NiCo oxides is necessary to achieve adequate phosphorization or sulfuration. By anchoring NiCo–P/S hollow nanoparticles into a CNT/rGO hybrid network, superior capacitive performances were demonstrated, presenting remarkable capacity (698.6 C g–1 at 1 A g–1) as well as promising rate performance (a capacity retention ratio of 61.5% at 20 A g–1) as an electrode material for supercapacitors. An asymmetric supercapacitor device employing a NiCo–P/S@C@G composite was also fabricated. The device presented favorable energy density at high power density and was able to power a light-emitting diode (LED) for several minutes, proving outstanding practical properties of the composite.