Computational insight into bilayer NC7 anode material for Li/Na/Mg-ion batteries

Two-dimensional (2D) materials are recognized as promising candidates for the novel materials of metal-ion batteries for their unique physical and chemical properties. Here, we explore the possibility of a 2D NC7 as an anode material for the Li/Na/Mg-ion battery using first-principles calculations. To elucidate the role of a swelling effect we considered the bilayer form of NC7 intercalated by Li, Na and Mg atoms. Our results show that pristine bilayer NC7 is dynamically and thermally stable. The intercalating atoms prefer to stay in the hollow site but the drastic volume expansion after Na-, and Mg-intercalation eliminates NC7 from the group of potential candidates for anode material for Na-and Mg-ion batteries. Against, the Li-intercalated NC7 bilayer possesses a small swelling effect, thermal stability and a high theoretical capacity of 683.14 mAh/g. In addition, the open circuit voltage and diffusion barriers of the Li ions between two NC7 layers are also quite low. These make NC7 a highly promising alternative material for Li-ion battery anode with great structural sturdiness.