One‐Step Solvothermal Synthesis of 3D Hierarchical Ni_xCo_9‐xS₈ Structures for High‐Performance Supercapacitors

Abstract

Abstract Three‐dimensional flowerlike Ni x Co 9‐ x S 8 nanosheets with polyvinyl pyrrolidone as the agent dictating the material morphology have been synthesized by means of a one‐step solvothermal synthesis procedure. The synthetically facile 3D Ni x Co 9‐ x S 8 nanosheets (P‐Ni x Co 9‐ x S 8 ) achieve high specific surface area and outstanding electrochemical performance. When applied as an electrode material, it demonstrates excellent specific capacitance of 1319.76 F g −1 at 1 A g −1 , and good rate performance of 1040.4 F g −1 at 20 A g −1 . Also, the material achieves remarkable cycling stability that still retains 93.7 % of max capacity after 1500 cycles at the high current density of 10 A g −1 . Even after 4000 cycles, a maximum capacity of 71.2 % is retained. Additionally, the P‐Ni x Co 9‐x S 8 //AC asymmetric supercapacitor (ASC) prepared exhibits excellent capacitive performance with a high specific capacitance (119.9 F g −1 ), high energy density (43.80 Wh kg −1 at 821.25 W kg −1 ) and high power density (30.30 Wh kg −1 at 15.58 kW kg −1 ).