Adsorption of K Ions on Single-Layer GeC for Potential Anode of K Ion Batteries.

Potassium ion batteries (KIBs) are considered as promising alternatives to lithium ion batteries (LIBs), following the rapid increase of demand for portable devices, and the development of electric vehicles and smart grids. Though there has been a promising breakthrough in KIB tech niques, exploring the promising anode materials for KIBs is still a challenge. Rational design with first-principle methods can help to speed up the discovery of potential anodes for KIBs. With density functional calculations, GeC with graphene-like 2D structure (g-GeC) is shown to be a desired anode material for applications in KIBs. The results show that the 2D g-GeC with a high concentration of K ions is thermodynamically stable, due to the strong interaction between C and Ge in GeC layer with the proper interaction between K and GeC. The storage capacity can be about 320 mAh/g, higher than that (279 mAh/g) in graphite. The low energy barrier (0.13 eV) of K ions diffusion on the honeycomb structure with proper voltage profile indicates the fast charge transfer. These theoretical finds are expected to stimulate the future experimental works in KIBs.