First-Principles Prediction of Reaction-Induced Structural Evolution at the Interface between Lithium Metal and Sulfide Electrolytes

The utilization of sulfide-based electrolytes, such as Li3PS4 (LPS), for lithium metal batteries is known to be hindered by their interfacial instability with Li metal. However, there is still a lack of understanding regarding the mechanisms that govern impedance spikes at the anode/electrolyte interface. Herein, based on first-principles simulations, we present chemical reaction-induced evolution of the interface between Li metal and LPS. Our results suggest the persistent growth of voids in the interphase layer, as the interfacial reaction progresses. This intriguing behavior is found to originate from the higher density of lithiated LPS compared to that of the separated Li/LPS state. Moreover, while applying stack pressure improves the interfacial contact, it tends to enhance further electrolyte decomposition by increasing the electrical conductivity at the interface. Furthermore, our work highlights that the unique chemo-mechanical character of LPS may enable interfacial voids to form, persist, and enlarge during repeated compression and elongation imposed over the course of battery cycling. These findings provide new insights into the potential physical origin and evolution of degradation at the Li/LPS interface.