MXenes as High Capacity Electrode Materials for Metal (Li, Na, K, Ca)-ion batteries
arXiv:1312.3615
Abstract
Two-dimensional (2D) materials can have an excellent capability to handle high rates of charge in ion batteries since metal ions need not diffuse in a 3D lattice structure. However graphene, which is the most important 2D material, is known to have no Li capacity. Herein, adsorption of Li, as well as Na, K, and Ca on TiC, one representative MXene, is predicted by first-principles density functional calculations. In our study, we observed that these alkali ions exhibit different adsorption energy depending on the coverage. The adsorption energies of Na, K and Ca decrease as coverage increases, while Li shows little sensitivity to variance in coverage. This observed relationship between adsorption energies and coverage of alkali ions on TiC can be explained by their effective ionic radii. A larger effective ionic radius increases interaction between alkali atoms, thus lower capacity and coverage are obtained. Our calculated capacity values for Li, Na, K and Ca on TiC are 639.5, 319.8, 191.8 and 159.9 mAh g, respectively. Compared to materials currently used in Li ion battery anodes, MXene shows great promise in increasing overall battery performance.
arXiv commentThis paper has been withdrawn by the author due to some mistakes in the figures