Ni9S8/Ni17S18@C nanocrystals derived by Ni-MOF precursor for high-performance hybrid supercapacitor applications

Compared with batteries and conventional capacitors, supercapacitors have become a hot research topic in the electrochemically energy-storing domain benefiting from their preponderances. The selection of electrode materials determines the electrochemical performance of supercapacitors. TMSs derived from MOFs show promising potential for the supercapacitors. We have designed a complex of Ni9S8 and Ni17S18 with carbon layers coating by using Ni-MOF as a precursor (Ni9S8/Ni17S18@C). Ni9S8/Ni17S18@C derived from Ni-MOF is obtained by high temperature vulcanization. The presence of the peculiar heterostructure of two-phase metal sulfides in the Ni9S8/Ni17S18@C can expose ample active sites, which can accelerate the ion diffusion process. The mass specific capacity of Ni9S8/Ni17S18@C can reach 998.5C·g−1 at 1 A·g−1, and still retains 80.02 % of its original permittance after 5000 charging-discharging cycles. The synergistic effect between metal sulfides and carbon allows more ions to be transported quickly, contributing to improved capacity and excellent magnification performance. Moreover, the asymmetric supercapacitor (ASC) assembled with Ni9S8/Ni17S18@C as the positive pole and porous carbons (PCs) as the negative electrode can achieve an energy density of 58.88 Wh·kg−1 at the power density of 799.63 W·kg−1 and exhibits excellent cycling stability.