Ab initio studies on Li4+xTi5O12 compounds as anode materials for lithium-ion batteries

The structural and electronic properties of Li4+xTi5O12 compounds (with 0 <= x <= 6)-to be used as anode materials for lithium-ion batteries-are studied by means of first principles calculations. The results suggest that Li(4)Ti5O(12) can be lithiated to the state Li8.5Ti5O12, which provides a theoretical capacity that is about 1.5 times higher than that of the compound lithiated to Li7Ti5O12, Further insertion of lithium species into the Li8.5Ti5O12 lattice results in a clear structural distortion. The small lattice expansion observed upon Lithium insertion (about 0.4% for the lithiated material Li8.5Ti5O12) and the retained [Li1Ti5]O-16d(12) framework indicate that the insertion/extraction process is reversible. Furthermore, the predicted intercalation potentials are 1.48 and 0.05 V (vs Li/Li+) for the Li4Ti5O12/Li7Ti5O12 and Li7Ti5O12/Li8.5Ti5O12 composition ranges, respectively. Electronic-structure analysis shows that the lithiated states Li4+xTi5O12 are metallic, which is indicative of good electronic-conduction properties.