Engineering core-shell NiC₂O₄@C/N-direct-doped NiCoZn-LDH for supercapacitors

Layered double hydroxides (LDHs) are promising cathode materials for supercapacitors due to high theoretical specific capacitance and unique layered structure. Constructing hierarchical core-shell structure for the multicomponent LDHs is an effective strategy to further utilize them. Herein, a novel hierarchical core-shell structure (NCO@C/N-LDH) was fabricated by direct-doping of C and N species into NiCoZn-LDH nanosheets (C/N-LDH) coved on NiC2O4 (NCO) arranged on the nickel foam via two-step hydrothermal method. The NCO as a backbone prevented C/N-LDH nanosheets from collapsing in charge/discharge process, while the C/N-LDH shell provided abundant active sites and exclusive access to electron/ion transport for accelerating the Faradaic reaction kinetics. The optimal NCO@C/N-LDH(2.0) displayed a remarkable electrochemical performance with a high specific charge of 1841.0C/g at 1 A/g and good rate capability. Furthermore, the as-fabricated NCO@C/N-LDH//AC device delivered a high energy density of 56.9 Wh kg-1 at power density of 800 W kg-1.