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.