Theoretical study of TiO2(B) and its interaction with Li as a prospective electrode for batteries

J. JUAN; L. FERNÁNDEZ-WERNER; P. V. JASEN; P. BECHTHOLD; R. FACCIO; E. A. GONZALEZ

México

Conferencia; 2020 Express Conference on the Physics of Materials and its Applications in Energy and Environment ? e-CPM2020; 2020

Today, fossil fuels represent the majority of the energy consumption of the world, but cause damage to the environment. In this context, an increasing interest in alternative energies appear, such as Li-ion batteries. Materials such as TiO2 (B) can possibly be used for the anode of Li-ion batteries [1]. We modelled this material with DFT as implemented in the VASP code [2], and studied the intercalation of Li in the (100) and (001) surfaces of TiO2 (B), as is reported by previous works [3]. DFT+U correction was included to consider the strong correlation of the ?d? electron states of the transition metal [4]. Intercalation voltages in the different sites in the dilute limit concentration (see Fig. 1) in the surfaces (-1.46 to -2.08 eV and -1.84 to -2.03 eV for (100) and (001) surfaces, respectively) were found to be higher than those from bulk. Li intercalation in the (100) and the (001) surfaces is found to be a favorable process. Li is the charge carrier and the charges are located close, at the nearest Ti and O atoms, according to charge density difference analysis in the most stable sites of the surfaces. A small spin polarization is present in the lithiated systems according to the DOS analysis of the surfaces. NEB method was implemented to study the diffusion of Li atoms in the surfaces [5]. The activation energy barriers of the most stable diffusion pathways are 0.64 eV and 0.26 eV for the (100) and (001) surfaces, respectively.In conclusion, our results show that Li atoms in the surfaces present more stability than in the bulk; that there is a transfer of charge from Li to the nearest Ti and O atoms; that intercalation of Li induces a small spin polarization; that Li atoms can move and diffuse throughout the widest channels of these surfaces. Therefore, more realistic models such as the one presented in this work are needed to be considered in order to obtain a better description of electronic and structural properties of materials for Li-electrodes.