Exploring the potentials of TiN and TiNX (X = O, F, OH) monolayers as anodes for Li or non-Li ion batteries from first-principles calculations.

The electronic properties and different metal ion (Li, Na, Mg) storage capabilities of the two-dimensional (2D) TiN monolayer and its TiNX derivatives (X = O, F, and OH) as anode materials in rechargeable batteries have been systematically investigated by density functional theory (DFT) computations. Results show that the bare TiN and terminated monolayers in their most stable configurations are all metallic before and after metal ion adsorption. The relatively low diffusion barriers on the bare TiN monolayer were also confirmed, which implies faster charge and discharge rates. With respect to storage capacity, a high theoretical capacity of 1874 mA h g can be provided by the TiN monolayer for Mg due to its multilayer adsorption and two-electron reaction. The existence of functional groups is proven to be unfavorable to metal ion migration and will decrease the corresponding storage capacities, which should be avoided in experiments as much as possible. These excellent performances suggest that the bare TiN is a promising anode material for Li-ion or non-Li-ion batteries.