Structural stabilities, surface morphologies and electronic properties of spinel LiTi2O4 as anode materials for lithium-ion battery: A first-principles investigation

• The thermodynamic stability of LixTi2O4 and origin for the stability were revealed.
• Evolution of the morphologies as functions of chemical environments was clarified.
• Surface effects on the electrochemical performance of LiTi2O4 were discussed.

The thermodynamic stabilities, surface morphologies, and electronic structures of the LiTi2O4 compound were investigated by the first-principles methods. The formation enthalpies and lattice constants of LixTi2O4 decrease at first and then increase again. This phenomenon is related to the balance between LiO attractions and LiLi repulsions. Population analysis revealed that pure ionic and strong covalent bonds are formed respectively between lithium and oxygen and between titanium and oxygen in LiTi2O4 material. These interactions are very crucial for the thermodynamic stability of the compounds. The surface stability was considered as functions of the chemical potentials, and five terminations, (100)-Ti2O4, (110)-Ti2O4, (210)-Ti2O4, (111)-LiTiO4, and (310)-Ti2O8ones, are dominant in the stability diagram. Our calculation showed that a particle morphology with mono (110) facet can be obtained at Ti- and/or O-moderate conditions, and this morphology will be very helpful for improving the rate performance of the material via reduction of the lithium diffusion distance. Furthermore, partially filled electronic states at the Fermi energy were confirmed for bulk LiTi2O4 and some of the surfaces, and they are responsible for the excellent electronic conductivity of the material. Further calculations showed that the work functions are sensitive to the stoichiometry of the surfaces.

Figure optionsDownload as PowerPoint slide