2D-VN₂ MXene as a novel anode material for Li, Na and K ion batteries: Insights from the first-principles...

Developing two-dimensional (2D) materials as anode materials have been proved a promising approach to significantly improve the charge storage performances of alkali metal ion. Herein, we investigate mono-layered VN₂ as an anode material in Li, Na and K ion batteries. Firstly, the high stability of 2D-VN₂ has been demonstrated via calculating the phonon spectra. 2D-VN₂ is capable of delivering high capacities of 678.8, 339.4 and 1357.6 mAh g^-1 in Li⁺, K⁺ and Na⁺ storage, respectively. In addition, the metallic properties and corresponding high electrical conductivity and low diffusion barriers of 201.1 meV for Li atoms, 34.7 meV for K atoms and 84.1 meV for Na atoms on VN₂ surface, indicating good capacity and the superior rate performances of alkali metal atoms migration on VN₂. The calculated average voltage of Li, Na and K are respectively 0.81 V, 0.29 V and 0.77 V, suggesting a promising voltage behavior compared with other 2D materials.