Synthesis of Hollow NiCo-Layered Double Hydroxide Nanostructures from Metal–Organic Frameworks on Biomass-Derived Carbon for Asymmetric Supercapacitor Electrodes

Layered hydroxides are considered ideal materials used in supercapacitors owing to their unique layered structure and superior theoretical specific capacitance. However, issues such as easy agglomeration and poor conductivity limit their further applications. In this paper, an in situ synthesis strategy based on pine-derived porous carbon (ZHPC) is designed, successfully leading to the preparation of a layered double hydroxide/porous carbon composite material (NiCo-LDH/ZHPC). Pine sawdust is used as a biomass precursor, and ZHPC with a high surface area is prepared through ZnCl2-assisted hydrothermal carbonization followed by high-temperature activation. Zeolitic imidazolate framework-67 (ZIF-67) is loaded onto the ZHPC as a sacrificial template, and hollow NiCo-LDH nanostructures are generated through a solvothermal etching method. The material exhibits a capacitance of 1162.5 F·g–1 at 1 A·g–1 and 87.8% retention at 10 A·g–1, indicating its favorable capacitance performance. An asymmetric supercapacitor (ASC) is assembled and operated at a voltage of 1.6 V. It achieves an energy density of 32.6 Wh·kg–1 at a corresponding power density of 800.0 W·kg–1 and maintains 75.8% capacity retention after 3000 cycles. Furthermore, the series-connected device can continuously power a small light bulb for 120 min. This study significantly enhances the conductivity and structural stability of LDH materials through carbon-based composites and sacrificial template strategies, providing an innovative approach for the fabrication of supercapacitors.