Nitrogen-Doping-Driven 3D Interwoven Nickel–Cobalt Layered Double Hydroxides on Wood Tracheid Inner Walls for Ultrahigh Areal Capacitance Supercapacitors

A two-step electrochemical deposition strategy is proposed to construct a ternary heterostructure of nickel–cobalt layered double hydroxides (NiCo-LDH) on nitrogen-doped MnO2-coated nitrogen-doped wood carbon (NDC). The nitrogen doping induces a morphological evolution of NiCo-LDH from 2D nanosheets to a 3D interwoven architecture on wood tracheid inner walls, significantly enhancing the specific surface area and ion diffusion kinetics. Benefiting from the synergistic effects between the 3D NiCo-LDH network, conductive MnO2, and hierarchical porous NDC substrate, the composite electrode achieves an exceptional areal capacitance of 21.56 F cm–2 at 10 mA cm–2 with 80.9% retention at 40 mA cm–2. The assembled asymmetric supercapacitor delivers a high energy density of 0.52 mWh cm–2 and a power density of 5.79 mW cm–2, alongside outstanding cycling stability (94.24% retention after 8,000 cycles). This work provides an approach for designing biomass-derived carbon-based electrodes with 3D structural engineering, demonstrating significant potential for advanced energy storage applications.