LAUSR

Transition metal selenides (TMSs) with significant electrochemical activity and high intrinsic electrical conductivity have lately attracted considerable attention due to their potential for energy storage devices. However, the low energy densities of the reported TMSs, originating from the small active surface area and poor electrolyte ion mobility, substantively restrict their application potential. In this work, porous ultrathin nickel selenide nanosheet networks (NiSe NNs) on nickel foam have been fabricated using a novel, facile method, i.e. selenylation/pickling the pre-formed manganese (Mn)-doped α-Ni(OH) 2 . Removal of Mn results in a highly porous structure to the NNs. The three-dimensional framework of the NNs and the inherent nature of NiSe afford high ion mobility, abundant accessible activated sites, vigorous electrochemical activity, and low resistance. Using the NNs as electrodes achieves one of the highest specific capacity of TMSs ever reported, i.e. 443 mA h g -1 (807 μAh cm -2 ) at 3.0 A g -1 . The assembled NiSe NNs//porous carbon hybrid supercapacitor delivers a high energy density of 66.6 Wh kg -1 at a power density of 425 W kg -1 , with excellent cycling stability. This work provides a new production strategy for novel electrode materials applied in high-performance hybrid supercapacitors, and a fresh path towards commercial applications of hybrid supercapacitors based on TMS electrodes.