A surface defect strategy of NiCo-layered double hydroxide decorated MXene layers for durable solid-state supercapacitors†

The aggregation and self-stacking of MXenes and layered double hydroxides (LDHs) in the electrode preparation process are considered the primary obstacles to their practical applications. Herein, a metal–organic framework (MOF) derived NiCo-LDH is grown on MXene to design hierarchical electrodes. The scanning electron microscopy and X-ray diffraction results show that the combination of NiCo-LDH and MXene can simultaneously reduce self-aggregation and expand the MXene layer spacing. The higher electronegativity of the surface groups of MXene leads to an increased tendency of the hydroxyl group to attract metal ions, thereby facilitating the creation of oxygen vacancies. Density functional theory (DFT) simulations simultaneously reveal that oxygen vacancies enhance the mobilization of additional charge carriers during the conduction process. Specifically, the MXene@NiCo-LDH electrode demonstrates an outstanding specific capacity of 163.25 mA h g⁻¹ at 1 A g⁻¹. The constructed supercapacitor delivers a superior energy density of 46.10 W h kg⁻¹ at a power density of 1170.38 W kg⁻¹. Meanwhile, the puncture, pressure, and folding tests for the durability of the supercapacitor confirm that the design of LDHs and MXene composites shows a promising application prospect in supercapacitors.