Self-assembled Cobalt-doped NiMn-layered double hydroxide (LDH)/V2CT MXene hybrids for advanced aqueous electrochemical energy storage properties

High-performance aqueous electrochemical energy storage technology has attracted extensive research interest due to its high safety and potential for commercialization. Herein, following the simultaneous doping-electrostatic synergistic assembly strategy, we synthesized the 2D/2D Co-doped NiMn-Layered double hydroxide (LDH)/V2CTx MXene (CNMV) composite materials that serve as advanced electrodes for aqueous energy storage devices, such as supercapacitors and zinc ion batteries (ZIBs). For supercapacitors, benefiting from the hetero ion doping effect, the as-assembled CNMV electrode exhibits a higher specific capacitance of 1005 F g−1 at a current density of 1 A g−1. For the assembled asymmetric supercapacitor (ASC) devices, a high energy density of 30.16 Wh kg−1 at 0.7 kW kg−1 was achieved. Acting as the cathode for ZIBs, CNMV exhibits a high reversible capacity of 322.7 mA h g−1 at 0.2 A g−1 after 100 cycles, and a considerable energy density of 368.7 W h kg−1 at a power density of 246 W kg−1. The battery-type transformation to the pseudocapacitance-type CNMV electrode for the supercapacitor was demonstrated by quantitative kinetic analysis, while phase transformation and Zn2+ insertion/extraction for zinc ion storage mechanism were demonstrated by ex-situ XRD and XPS. This study provides a facile and effective approach for the design of high-performance MXene-based electrodes for aqueous electrochemical energy storage devices.