Li intercalation, electronic and thermodynamic properties in H₂Ti₃O₇ bulk: A theoretical study

We performed Density Functional Theory calculations with Hubbard methodology (DFT + U) in order to study Li intercalation in H2Ti3O7 and the electronic and thermodynamic properties of this doped system. The calculated voltages for the three doped systems considered were found to be stable and with promising values. Their electronic structure presented a small magnetic moment induced due to the asymmetry present in the spin up and spin down contribution to the densities of states. Also, the systems present a type-n semiconductor behaviour. A charge transfer of 0.7e- from Li to titanate was observed. Phonon densities of states show the presence of H and O peaks at high frequencies in these systems. A novel theoretical thermodynamic study on Li intercalation in this titanate was performed, finding that the doped systems have stable and promising properties. The calculated bulk's Gibbs free energy difference was of 252 kJ center dot mol(-1). The Nudged Elastic Band (NEB) methodology and on-the-fly force field machine learning (MLFF) from ab initio molecular dynamics (AIMD) were applied to determine the stability sites for Li. From selected diffusion paths for Li, we found that there is one in the structure with an energy barrier of 0.33 eV. Consequently, this study presents innovative and significant results as a guide for future theoretical and experimental works on this potentially Li-ion battery anode material.