Graphene-like carbon-nitrogen materials as anode materials for Li-ion and mg-ion batteries

Two-dimensional materials have been considered to be promising potential electrodes of metal-ion batteries. Here we explored the application of three graphene-like carbon-nitrogen structures as anode materials in lithium (Li)–ion and magnesium (Mg)-ion Batteries. We first studied the intrinsic characteristic of C₂N, C₃N, and g-C₃N₄, explored possible adsorption positions in each structure, studied the diffusion path, energy barrier, voltage profile, and theoretical capacity. Our results show that the theoretical capacities of C₂N anode is 671.7 mAhg⁻¹ for Li-ions and 588.4 mAhg⁻¹ for Mg-ions, which makes it a promising anode material. C₃N is not suitable as anode material. Because of the few absorptions sites, the capacity of g-C₃N₄ sheet is only 199.5 mAhg⁻¹ for Li-ions and 319.2 mAhg⁻¹for Mg-ions, which makes it unsuitable as anode material but its performance can be much improved when curled into nanotubes. Using Mg-ions instead of Li-ions can reduce the deformation of the material (for C₂N) at the maximum concentration or improve the theoretical capacity (for C₃N₄), lowing the maximum open circuit voltage while improving the diffusion energy barrier.