In-situ growth of core-shell NiCo2O4@Ni-Co layered double hydroxides for all-solid-state flexible hybrid supercapacitor

In recent years, the core-shell heterostructure has been considered as one of the most promising candidates for the next generation of electrode materials, which can not only shorten the ion diffusion distance, but also increase the contact area between the electrode and the electrolyte. Herein, two different morphologies of NiCo2O4 nanomaterials were prepared by hydrothermal-calcination method, and then the hybrid structure consisting of needle-like NiCo2O4 core and Ni-Co layered double hydroxide (Ni-Co LDH) shell is composited on carbon fiber cloth (CFC) by constant current electrodeposition as electrode materials. The resultant NiCo2O4@Ni-Co LDH core-shell hybrid arrays exhibits the specific capacitance of 4901.8 m F cm−2 at the current density of 2 mA cm−2, which is much higher than that of needle NiCo2O4 and flake Ni-Co LDH. At the same time, the obtained NiCo2O4@Ni-Co LDH as the positive electrode while the activated (AC) serves as the negative electrode, which is used to assemble the all-solid flexible asymmetric supercapacitor. It delivers an energy density of 0.859 mW h cm-3 at the power density of 2 mA cm−2, as well as an excellent cycling performance with capacitance retention of 92.3 % after 5000 cycles at 16 mA cm−2. These results suggest that this core-shell structured material could be a promising electrode for supercapacitors.