High-entropy
MXenes as an emerging subfamily of MXenes have attracted
great interest recently in the energy storage field, but the species
are modest and related reports are scarce. Herein, the structural,
electronic, and adsorption properties of a Ti0.75V0.75Cr0.75Mo0.75C2 high-entropy
MXene nanosheet are investigated by density functional theory. The
predicted dynamic and thermal stabilities indicate experimental feasibility.
The Ti0.75V0.75Cr0.75Mo0.75C2 nanosheet exhibits strong conductivity before and after
zinc-ion adsorption. Bilayer Ti0.75V0.75Cr0.75Mo0.75C2 possesses a large interlayer
spacing so that it can accommodate a larger amount of zinc ions than
bilayer Ti3C2. The effective interactions between
zinc ions and bilayer Ti0.75V0.75Cr0.75Mo0.75C2 lead to high adsorption energies and
realize the largest and average open circuit voltages (OCVs) of 1.18
and 0.63 V, respectively. With saturated zinc ions, the specific storage
capacity of bilayer Ti0.75V0.75Cr0.75Mo0.75C2 reached 769.2 mAh/g. The calculated
OCV and storage capacity are superior to those of Ti3C2. The calculated diffusion barriers between 0.18 and 0.29
eV besides the low mean square displacements and small diffusion coefficients
indicate the fast kinetics processes of zinc-ion adsorption/desorption.
The expansion ratio is merely 5.8%, suggesting a potential long lifetime,
and it may realize large numbers of charge/discharge cycles without
structural collapse. This work sheds light on the excellent electrochemical
properties of the Ti0.75V0.75Cr0.75Mo0.75C2 nanosheet, which are universal for
2D high-entropy MXene family. These results will stimulate further
theoretical and experimental studies on the electrochemical performance
of 2D high-entropy MXenes.