Enhancing asymmetric supercapacitor performance through synergistic coupling of V-doped NiMnLDH nanosheets and few-layer Ti₃C₂T_x-MXene

This work synthesized a 3D V-NiMnLDH@Ti₃C₂T_x−MXene nanocomposite by adsorbing V³⁺, Ni²⁺, and Mn³⁺ metal cations onto the few-layer surface using a one-step hydrothermal technique. This in-situ growing approach increased capacitance performance by improving electron transport without binders or conductive additives. Initial coupling between MXene layers and nickel foam skeleton allowed excellent charge storage. Hydrothermally produced V-doped NiMnLDH nanosheets on Ti₃C₂T_x−MXene enabled rapid, reversible Faradaic reactions and a narrow ion diffusion channel. With few-layer Ti₃C₂T_x−MXene, V-doped NiMnLDH nanosheets preserved shape throughout charge-discharge cycles, improving material stability. The V-NiMnLDH@Ti₃C₂T_x−MXene composite cathode had a specific capacitance of 1920 F g^-1 at 1 A g^-1 in 1 M KOH and showed excellent stability (92.1% retention after 5000 cycles). Asymmetric supercapacitors with NiMnLDH@Ti₃C₂T_x−MXene/NFs composite positive electrodes and activated carbon negative electrodes had a wide potential window (0–1.5 V), 58.4 Wh kg^-1 at 1500 W kg^-1 energy density, and 90.1% capacity retention after 10,000 cycles. DFT simulations showed that NiMnLDH@Ti₃C₂T_x−MXene has better charge transfer, increasing specific capacitance.