A density functional theory study on the assessment of alpha-CN and alpha-CP monolayers as anode material in Li-ion batteries

Density functional theory (DFT) calculations were employed to probe the feasibility of 2D alpha-CM (M = N, P) as an anode material for Li-ion batteries (LIBs). Our findings demonstrate the dynamical, mechanical and thermal stability of 2D alpha-CM. In particular, for the 2D alpha-CP adsorbed with Li atom, binding energy (E-B) of -2.00 eV ensures favourable adsorption. In contrast to 2D alpha-CP, the E-B of adsorbed Li atom over alpha-CN is lower than the cohesive energy of lithium metal, this eliminates the accessibility of 2D alpha-CN as an anode in LIBs. The Li atom adsorption changes the nature of the 2D alpha-CP from semiconducting to metallic, ensuring high electronic conductivity. Both partial density of states and Lowdin charge analysis indicate substantial charge transfer from Li atom to 2D alpha-CP after adsorption. The multilayer adsorption on both sides of 2D alpha-CP yields Li5.0CP monolayer with remarkably high specific storage capacity (1108.91 mAhg(-1)). The obtained average open circuit voltage is suitable for extensive battery application. Diffusion barrier of 0.11 eV shows ultrahigh ionic mobility over the 2D alpha-CP and thus facilitates charging/discharging process. As a result, high specific storage capacity, lower diffusion barrier, negligible volume change and excellent electronic conductivity imply the promising utility of 2D alpha-CP as anodic material in LIBs.