Ultrahigh-performance pseudocapacitor based on phase-controlled synthesis of MoS2 nanosheets decorated Ni3S2 hybrid structure through annealing treatment

In this work, a hierarchical Ni 3 S 2 @MoS 2 hybrid structure was synthesized by an effective strategy with a combined hydrothermal route and subsequent annealing treatment. When tested as supercapacitor electrodes, the Ni 3 S 2 @MoS 2 composites exhibited high specific capacitance of 1418.5   F   g −1 at 0.5   A   g −1 , which also showed a good capacitance retention of 75.8% at 5   A   g −1 after 1250 cycles. The Ni 3 S 2 @MoS 2 composites demonstrated 1.9 fold higher specific capacitance compared to the amorphous shell counterpart (Ni x S y @MoS 2 ). Furthermore, the assembled asymmetric supercapacitor (Ni 3 S 2 @MoS 2 //rGO) also demonstrated a capacitance of 61   F   g −1 at 0.5   A   g −1 , with energy and power densities of 21.7   Wh   kg −1 at 400   W   kg −1 and 12   Wh   kg −1 at 2400   W   kg −1 under an operating window of 1.6   V. The asymmetric supercapacitor also showed a favorable cycle stability with 72% capacity retention over 4000 cycles at 10   A   g −1 . The improved electrochemical performance is attributed to the synergetic effect of the large accessible surface area and optimal contacts between the MoS 2 and the electrolyte, as well as high capacitance of the metallic Ni 3 S 2 core.