Insight into the interface chemical stability of the solid electrolyte Li1/2La1/2TiO3 and the Li/Li–In alloy anode†

All-solid-state lithium–sulfur batteries (ASSLSBs) have gained significant attention due to their high energy density and excellent safety characteristics. However, the practical application of these batteries is hindered by interfacial issues between the solid electrolyte and electrode. The instability of this interface during charge–discharge cycles arises from side effects of the electrolyte and anode, as well as poor solid–solid contact. In this study, we employ first principles calculations to analyze the chemical stability at the interface between the Li_1/2La_1/2TiO₃ (LLTO) electrolyte and the Li anode, with a focus on strategies to address this issue and stabilize the cathode–electrolyte interface. We systematically investigate various physicochemical properties at the LLTO|Li and LLTO|LiIn₂ interfaces, including electron conductivity, work function, chemical stability, and Li⁺ diffusion across the interface. Our findings demonstrate that LLTO|LiIn₂ exhibits enhanced long-term storage capabilities for ASSLSBs while reducing overall costs. Alloying lithium anodes with In atoms weakens electron injection into the electrolyte within the anode, thereby reducing chances of electrolyte reduction and improving charge–discharge performance. Additionally, a lower Li⁺ diffusion barrier is observed at the LLTO|LiIn₂ interface which promotes efficient Li⁺ transport. This work provides valuable theoretical insights for developing effective interface engineering strategies between electrolytes and anodes.