Nanosphere-like NiSe2/SnSe2 composite electrode materials with excellent performance for asymmetric supercapacitor

Tin metal was widely used in energy storage and photovoltaic devices due to its high stability and high conductivity. However, due to its low electrochemical performance, the application of tin compounds in supercapacitors was rarely reported. In this paper, it was first used a simple two-step hydrothermal method to design a nanospherical NiSe2/SnSe2 composite as supercapacitor electrode materials. The composite exhibited excellent electrochemical properties, it not only increased conductivity and provided more active sites, but also shortened electron and ion transport paths. The (Ni, Sn)Se2-2.5 exhibited an appealing specific capacity (116 mA h g−1 at 1 A g−1) and better cycle stability (80% capacity retention after 4000 cycles). Moreover, asymmetric supercapacitors which were assembled with (Ni, Sn)Se2-2.5 and activated carbon had superior electrochemical performance. When the specific power was 855 W kg−1, the specific energy can reached 34.2 Wh Kg−1 and accompanied by an efficient stability (82.3% of capacity retention after 10000 cycles). Therefore, the synthesized spherical (Ni, Sn)Se2-2.5 possessed excellent prospects as electrode materials for supercapacitors.