Stabilities and electronic properties of lithium titanium oxide anode material for lithium ion battery

A theoretical study of the structural, elastic and electronic properties of spinel LiTi2O4 anode has been performed by density functional theory (DFT) plane-wave pseudopotential method. The independent elastic constants, shear modulus (G), bulk modulus (B), and Young's modulus (E) are evaluated, respectively. The results suggest that cubic LiTi2O4 is mechanically stable. The G/B ratio of 0.584 indicates the ductility of LiTi2O4 is good. The electron density difference of LiTi2O4 shows that the O2p orbits overlap effectively with Ti3d ones, confirming the formations of strong covalent bonds between them, while Li is fully ionized in the lattice. The formation enthalpy for LiTi2O4 is calculated to be −2070.723 ± 1.6 kJ mol−1. The strong covalent bonds between O and Ti atoms are not only responsible for the excellent mechanical stabilities but also very crucial for the thermodynamic stability of LiTi2O4 compound. Furthermore, in Li2Ti2O4 compound, the full occupation of 16(c) sites by Li+ not only leads to a smaller C12 value but also leads to a much larger C44 one. Therefore, the plasticity and ductility of the Li2Ti2O4 become poor in comparison to LiTi2O4, while the thermodynamic stability of Li2Ti2O4 can be further improved after the Li+ intercalation of LiTi2O4.

► The formation enthalpy for LiTi2O4 is calculated for the first time. ► LiTi2O4 is mechanically stable. ► The G/B ratio of 0.584 indicates the ductility of LiTi2O4 is excellent.