Theoretical prediction of MoN2 monolayer as a high capacity electrode material for metal ion batteries

Benefited from the advantages on environmental benign, easy purification, and high thermal stability, the recently synthesized two-dimensional (2D) material MoN2 shows great potential for clean and renewable energy applications. Here, through first-principles calculations, we show that the monolayered MoN2 is promising to be a high capacity electrode material for metal ion batteries. Firstly, identified by phonon dispersion and exfoliation energy calculations, MoN2 monolayer is proved to be structurally stable and could be exfoliated from its bulk counterpart in experiments. Secondly, all the studied metal atoms (Li, Na and K) can be adsorbed on MoN2 monolayer, with both pristine and doped MoN2 being metallic. Thirdly, the metal atoms possess moderate/low migration barriers on MoN2, which ensures excellent cycling performance as a battery electrode. In addition, the calculated average voltages suggest that MoN2 monolayer is suitable to be a cathode for Li-ion battery and anodes for Na-ion and K-ion batteries. Most importantly, as a cathode for Li-ion battery, MoN2 possesses a comparable average voltage but a 1-2 times larger capacity (432 mA h g-1) than usual commercial cathode materials; as an anode for Na-ion battery, the theoretical capacity (864 mA h g-1) of MoN2 is 2-5 times larger than typical 2D anode materials such as MoS2 and most MXenes. Finally we also provide an estimation of capacities for other transition-metal dinitrides materials. Our work suggests that the transition-metal dinitrides MoN2 is an appealing 2D electrode materials with high storage capacities.