Zn-doped NiSe2@Ni(OH)2 nanocomposites as binder-free electrodes for asymmetric supercapacitors with impressive performance

The low stability and poor activities of transition metal selenides (TMSs) in alkaline electrolyte limit their application in supercapacitors. Metal doping and hybridization of various electroactive materials with different properties are utilized to enhance the electrochemical performance of TMSs by optimizing their electronic structure and providing rich electrochemical active sites. Herein, we report a simple two-step hydrothermal method for the growth of Zn-doped NiSe2 and Ni(OH)2 nanocomposites on Ni foam [Zn-NiSe2/Ni(OH)2]. The resulting material delivers high specific capacity (1525.8 C g-1/564.7 mA h g-1 at 6 A g-1 and 1220 C g-1 at 10 A g-1) in a three-electrode system. A Zn-NiSe2/Ni(OH)2//porous carbon (PC) aqueous asymmetric supercapacitor (ASC) was built by utilizing Zn-NiSe2/Ni(OH)2 as the positive electrode and PC as the negative electrode. This Zn-NiSe2/Ni(OH)2//PC ASC shows an energy density of 75.8 W h kg-1 at a power density of 916.1 W kg-1 and achieves a specific capacity retention of 100% after 25 000 cycles at 10 A g-1. These results reveal that the Zn doping and the hybridization of NiSe2 with Ni(OH)2 can obtain impressive electrochemical properties in ASCs.