A 3D nanocomposite of NiCo2S4/CuCo2S4 heterostructure synthesized by chemical precipitation for asymmetric supercapacitors

In recent years, transition metal sulfides have been regarded as a promising energy storage material for supercapacitors, due to their high theoretical specific capacity and conductivity compared with other similar metal oxides and hydroxides. However, the sluggish diffusion dynamics and low capacitance impede its practical implement application. Herein, an advanced 3D nanocomposite of NiCo2S4/CuCo2S4 heterostructure was designed via a time-saving, safe and efficient approach. The mass transfer kinetics of NiCo2S4/CuCo2S4 nanocomposite has been significantly promoted owing to this novel heterostructure. Therefore, the NiCo2S4/CuCo2S4 electrode materials reveal a superior specific capacitance (180.8 mAh g−1 at 2 A g−1) and excellent rate properties (84.7% capacitance retention from 2 to 20 A g−1). The asymmetric supercapacitor device assembled with NiCo2S4/CuCo2S4 and activated carbon has an energy density of 37.0 Wh kg−1 at 400 W kg−1 and outstanding cyclic stability (93.3% remained after 10,000 cycles at 10 A g−1). Density functional theory (DFT) calculation further proves the electronic structure and the charge transfer can be tuned by the heterostructure of NiCo2S4 and CuCo2S4. This work offers a new perspective to design a high-performance electrode material in the field of supercapacitors.