In situ construction of sea urchin-like structural NiCo-LDH coated cobalt‑nitrogen co-doped carbon as high-performance electrode for supercapacitor

Nickel‑cobalt layered double hydroxide (NiCo-LDH) has received much attention in the field of supercapacitor electrodes due to its multiple oxidation states and good electrochemical activity. However, NiCo-LDH often suffers from structural instability and low conductivity in practical applications. In this study, sea urchin-like structural NiCo-LDH coated cobalt‑nitrogen co-doped carbon (NiCo-LDH@Co-NC-x) electrode materials were prepared by in situ growth of NiCo-LDH on the surface of cobalt‑nitrogen co-doped carbon nanosheets (Co-NC) using a one-step hydrothermal method. The results show that the NiCo-LDH@Co-NC-2 electrode material exhibits excellent electrochemical performance, its specific capacitance is up to 1909 F g −1 at a current density of 1 A g −1 , and capacitance retention of 69.5 % (only 26.2 % for NiCo-LDH) can be achieved after 10,000 cycles at a current density of 10 A g −1 . This is because the abundant and uniformly distributed Co nanoparticles on Co-NC provide nucleation sites for the in-situ growth of NiCo-LDH, effectively improving the interface binding between Co-NC and NiCo-LDH, enhancing the structural stability of NiCo-LDH, and ensuring highly efficient electron transport throughout the NiCo-LDH@Co-NC-2 electrode. An asymmetric supercapacitor (NiCo-LDH@Co-NC-2//AC) was further assembled with NiCo-LDH@Co-NC-2 and activated carbon (AC) as positive and negative electrodes, respectively, achieving an energy density as high as 36.8 Wh kg −1 at a power density of 750 W kg −1 . These findings suggest that the NiCo-LDH@Co-NC-2 composite can be a promising candidate for high-performance supercapacitor electrode.