Ni3S2 thin-layer nanosheets coupled with Co9S8 nanoparticles anchored on 3D cross-linking composite structure CNT@MXene for high-performance asymmetric supercapacitor

Supercapacitors attract tremendous research attention due to the cost-effectiveness, high power capacity and environment-friendly in the field of energy storage. In this work, Ni 3 S 2 thin-layer nanosheets coupled with Co 9 S 8 nanoparticles anchored on 3D cross-linking composite structure 5 mLCNT@MXene matrix (Ni/Co@C 5 M) was successfully synthesized via two-step hydrothermal and subsequent annealing treatment, possessing excellent electrochemical performance in terms of high rate capability, superior reversible capacity and outstanding durability. The electrode materials have distinct 3D cross-linking composite structure characteristics, which can significantly boost capacitive storage performance due to the introduction of CNT cross-linking conductive bridges and sulfides. Meanwhile, CNT can also prevent re-stacking of MXene layers and improve the electrical conductivity. As expected, the specific capacitance of Ni/Co@C 5 M electrode is 1827.5 F g −1 at 1 A g −1 , which retains 88.57% after 10,000 cycles at a high current density of 30 A g −1 in cycling stability. Notably, an asymmetric supercapacitor (Ni/Co@C 5 M as the negative electrode and AC as the positive electrode, Ni/Co@C 5 M // AC) has exceptionally high energy density up to 78.4 Wh kg −1 at a power density of 699.3 W kg −1 and long capacitance retention of 86.67% at 20 A g −1 for 10,000 cycles. The designed Ni/Co@C 5 M // AC asymmetric supercapacitor in this work holds a promising future for the upgrading new high-performance energy storage device.