Assessing electrochemical properties and diffusion dynamics of metal ions (Na, K, Ca, Mg, Al and Zn) on C2N monolayer as anode material for non-lithium ion batteries
We perform the first principles molecular dynamics simulations (FPMD) together with CI-NEB method to explore the structure, electrochemical properties and diffusion dynamics of C2N monolayer saturated with various univalent, bivalent and trivalent metal ions.A characteristic irregular adsorption structure consisting of inner coplanar layer at the large atomic pore and loosely bound outer layer is discovered for all six types of ions. The predicted specific capacities and mean open circuit voltages (OCVs) for them are: 600 mAh/g, 0.26 V (Na); 425 mAh/g, 1.56 V (K); 715 mAh/g, 0.96 V (Mg); 713 mAh/g, 1.31 V (Ca); 462 mAh/g, 1.40 V (Zn); 1237 mAh/g, 0.78 V (Al). For the energy favorable migration pathway, the diffusion energy barrier height for each ion species is found to be 0.24 eV (Na+), 0.10 eV (K+), 0.25 eV (Mg2+) and 0.10 eV (Ca2+). The values are larger than 1.0 eV for both Zn2+ and Al3+. FPMD simulations at 400 K further predict that the diffusion coefficients of Na and K atoms absorbed on C2N monolayer are 5.33×10-9 m2/s and 8.52×10-9 m2/s, and which are one order of magnitude higher than other remaining ions discussed in our work. The C2N monolayer shows the promising electrochemical properties and ion diffusion dynamics for the use as the anode material in alkaline metal ion batteries.