First-Principles Investigation of Lithium Titanate Oxide as an Anode Material in Li-, Na-, Mg-, Ca-, and K-Ion Batteries

The development of electrode material is a top priority to meet the requirements of high storage capacity, longer cyclic stability, and rapid transportation of ions in rechargeable metal-ion batteries. In this research, first-principles investigations are carried out to examine the suitability of lithium titanate oxide as an anode material in a series of metal-ion batteries, including Li-ion batteries (LIBs) and various multivalent-ion batteries such as Al-ion batteries (AIBs), Mg-ion batteries (MIBs), Ca-ion batteries (CIBs), and potassium-ion batteries (KIBs). The proposed material is comprehensively investigated to study the structural properties, thermal stability, metal atom storage capacity, and adsorption energy. The ab initio molecular dynamics (AIMD) simulation is used to ensure the thermal stability of the host material. The ideal anodic properties of the material are examined by modeling the adsorption of Li, Mg, Ca, K, and Al on the host material, thereby monitoring the exothermic reaction to explore its suitability for the relevant batteries. The calculated values of the storage capacity for LIBs, AIBs, MIBs, CIBs, and KIBs are 240 mAhg^-1, 1131 mAhg^-1, 1302 mAhg^-1, 411 mAhg^-1, 171 mAhg^-1, respectively. The structural integrity of the material under full loading ensures its longer cyclic life as an anode. The respective values of open circuit voltage (OCV) are calculated as 3.31, 4.12, 1.09, 1.24, and 1.43 V for LIBs, KIBs, MIBs, CIBs, and AIBs, indicating the performance of LTO as an electrode in these batteries. Additionally, the migration paths of Li ions and vacancies were studied using the Cl-NEB , indicating low energy barriers and revealing the stability of the host. The minimum energy barriers faced by diffusing metal atoms are calculated as 0.52 eV (LIBs), 0.28 eV (KIBs), 0.43 eV (MIBs), 0.01 eV (AIBs), and 1.51 eV (CIBs). The vacancy migration pathways of the metal ions in the host material are also determined. Furthermore, the MD simulations at 300K to 900 K are studied to determine the diffusion coefficient and rate performance of LTO as an electrode, which appeared as 1.04 × 10^-12 m²/s (LIBs), 0.83 × 10^-5 m²/s (MIBs), 0.66 × 10^-9 m²/s (AIBs), 0.07 × 10^-11 m²/s (CIBs), and 7.65 × 10^-9 m²/s (KIBs), respectively. The ionic conductivity of LIBs, MIBs, CIBs, KIBs, and AIBs appeared as 2.32 × 10^-3 Sm^-1, 1.19 × 10^-2 Sm^-1, 8.32 × 10^-2 Sm^-1, 6.33 × 10^-3 Sm^-1, and 0.21 × 10^-2 Sm^-1, respectively. The calculated properties point to the suitability of LTO as a promising electrode material in these batteries. Furthermore, to model the formation of the solid electrolyte interphase, the nonequilibrium Green's function technique was used to study the transportation of electrons and current-voltage characteristics. The findings of the study suggest that LTO is a potential candidate for use as an anode in multivalent metal-ion batteries.