Hierarchically Structured CoNi-LDH@Co(OH)2@CNFs Nanocomposite for High-Performance Supercapacitors

Nickel/cobalt hydroxides have attracted widespread attention in the field of supercapacitors owing to high theoretical capacitances. However, their practical applications are constrained by low conductivity and structural instability. Herein, cobalt hydroxide (Co(OH)2) nanosheets and cobalt−nickel-layered double hydroxide (CoNi-LDH) nanoflowers have been assembled on the surface of carbon nanofibers (CNFs) by two-step solvothermal reactions, and the synthesized CoNi-LDH@Co(OH)2@CNFs nanocomposite can serve as an excellent electrode material for constructing high-performance supercapacitors. Obviously, the electrochemical performances of CoNi-LDH@Co(OH)2@CNFs can be effectively enhanced after the stepwise modification of Co(OH)2 nanosheets and CoNi-LDH nanoflowers owing to their high theoretical specific capacitances and the formed hierarchical structure, which exhibits a high specific capacitance of 1179.4 F g−1 at 1 A g−1, as well as a desirable rate capability of 80.6% retention at 20 A g−1. Furthermore, the CoNi-LDH@Co(OH)2@CNFs//AC-based hybrid supercapacitor achieves an energy density of 41.4 Wh kg−1 at 788.4 W kg−1 and maintains 90.4% capacitance retention after 5000 cycles. This work also provides an effective strategy to exploit the advanced composites with the hierarchically layered architectures in energy storage.