Germagraphene as a promising anode material for lithium-ion batteries predicted from first-principles calculations.

Finding electrode materials with high capacity is a key challenge for developing lithium-ion batteries (LIBs). Graphene was once expected to be a promising candidate, but it turns out to be too inert to interact with Li. Here, by using first-principles calculations, we predict that germanium doped graphene, termed as Germagraphene, which has been achieved in a recent experiment, is a promising LIB anode material. We find that at the optimal Ge concentration, which corresponds to the chemical formula C17Ge, the specific capacity for Germagraphene can be as high as 1734 mA h g-1, over four times larger than that of graphite. We show that the material has good electrical conduction before and after Li adsorption. We also investigate the diffusion process of Li on Germagraphene, and find that the diffusion barrier is low (∼0.151 eV), implying fast Li diffusion. The calculated average intercalation potential is very low (∼0.03 V), which is beneficial for increasing the working voltage for full-cells. In addition, during the process of Li intercalation, the lattice change for the material is quite small (∼0.48%), implying a good cycling performance. These results suggest that Germagraphene could be a promising high-capacity anode material for LIBs.