Unique hollow-concave CoMoSx boxes with abundant mesoporous structure for high-performance hybrid supercapacitors

Abstract Unique hollow-concave CoMoSx boxes with abundant mesoporous structure are designed and constructed via a low-temperature calcination treatment followed by a hydrothermal process. Morphological observations show that the highly uniform and monodisperse hollow-concave CoMoSx boxes have an average size of approximately 410 nm. It is found that the hollow-concave structure of CoMoSx boxes can provide a large surface area and more active sites for the electrochemical reactions at the electrode/electrolyte interface, while reduce the volume of the inert inner cavities as well, achieving a maximum capacity of CoMoSx (784C g−1 at a current density of 1 A g−1). Moreover, the distinctive hollow-concave structure can offer a buffer to accommodate the volume expansion/contraction of CoMoSx, thus leading to an excellent cycling stability. The CoMoSx//AC asymmetric supercapacitor device is assembled and delivers a maximum energy density of 36.9 Wh kg−1 at a power density of 0.8 kW kg−1.