Solid electrolyte interphase formation between the Li0.29La0.57TiO3 solid-state electrolyte and a Li-metal anode: an ab initio molecular dynamics study

Abstract

An ab initio molecular dynamics study of an electrochemical interface between a solid-state-electrolyte Li_0.29La_0.57TiO₃ and Li-metal is performed to analyze interphase formation and evolution when external electric fields of 0, 0.5, 1.0 and 2.0 V Å⁻¹ are applied. From this electrochemical stability analysis, it was concluded that lithium-oxide (Li₂O) and lanthanum-oxide (La₂O₃) phases were formed at the electrolyte/anode interphase. As the electric field increased, oxygen from the electrolyte diffused through the Li-metal anode, increasing the amount of O from deeper crystallographic planes of the electrolyte that reacted with Li and La. A strong reduction of Ti was expected from their Bader charge variation from +3.5 in the bulk to +2.5 at the interface. Due to the loss of Li atoms from the anode to form Li-oxide at the interphase, vacancies were created on the Li-metal, causing anode structure amorphization near the Li-oxide phase and keeping the rest of the anode structure as BCC. Therefore, the interface was unstable because of the continuous Li-oxide and La-oxide formation and growth, which were more pronounced when increasing the external electric field.