Preparation of nanosheets of Ni5P2@Ni9S8/CoS1.097 heterostructure for aqueous asymmetric supercapacitors with high electrochemical performance

In recent years, transition metal sulfides, especially nickel-cobalt sulfide materials play a crucial role for supercapacitor applications. In this work, the Ni5P2@Ni9S8/CoS1.097 ([email protected]) core-shell material has been synthesized by simply phosphating the nickel mesh and subsequent electrodeposition of NCS to obtain a nanosheet heterostructure on nickel foam. The [email protected] composite material has a higher gravimetric capacitance of 2445.7 F g−1 than pure Ni-P of 1116.6 F g−1 and NCS materials of 1104.3 F g−1 at 1 A g−1. At the same time, [email protected] electrode yields excellent cycling stability (91.4% capacitance retention after 5000 charge–discharge cycles). An asymmetric supercapacitor (ASC) device assembled from [email protected] and activated carbon electrodes can deliver a highest energy/power density of 42.8 Wh kg−1/799.8 W kg−1, with 94.3% capacitance retention after 10,000 cycles at 5 A g−1. The improvement of electrochemical performance makes it possible to use it as an electrode material.