Mn(OH)2-coated Ni3S2 nanosheets on Ni foam as a cathode for high-performance aqueous asymmetric supercapacitors

In this work, we report a high-performance self-standing electrode of Mn(OH) 2 -coated Ni 3 S 2 (Ni 3 S 2 @Mn(OH) 2 ) nanosheets on Ni foam by hydrothermally growing the Ni 3 S 2 nanosheets and electrodepositing Mn(OH) 2 around Ni 3 S 2 . The structure of the Ni 3 S 2 nanosheets grown by the hydrothermal method is more stable, and the electrodeposition method is easier to synthesize Mn(OH) 2 without using any binder. The electrochemical characterization demonstrates that combining the Ni 3 S 2 nanosheet with the Mn(OH) 2 coating is an effective way to improving the charge storage performance because of the synergetic effects of both materials/structures. The electrode possesses a high area-specific capacitance of 6430.2 mF cm −2 at 1 mA cm −2 and good cycle stability with ~80.9% capacitance retention after 9000 cycles at 8 mA cm −2 . The aqueous asymmetric supercapacitors assembled with the Ni 3 S 2 @Mn(OH) 2 cathode, the activated carbon anode and 1 M KOH electrolyte delivers an energy density of 0.371 mWh cm −2 at 0.799 mW cm −2 , as well as good cycle stability with ~86.3% capacity retention after 10,000 cycles at 20 mA cm −2 . Given the high performance and relatively simple preparation, this work provides a valuable exploration of developing high-performance cathodes for aqueous supercapacitors. A high specific capacitance of 6430.2 mF cm −2 at 1 mA cm −2 and good rate performance are delivered. • A self-standing electrode of Ni 3 S 2 @Mn(OH) 2 was facilely prepared by the hydrothermal growth and subsequent electrodeposition. • A high capacitance of 6430.2 mF cm −2 at 1 mA cm −2 is obtained. • An energy density of up to 0.371 mWh cm −2 is delivered by the aqueous asymmetric supercapacitor.