Insight into the Li/LiPON Interface at the Molecular Level: Interfacial Decomposition and Reconfiguration

The interface between lithium metal and solid electrolytes (SEs) has a significant impact on the performance of lithium-metal batteries, especially when the electrolyte is unstable and decomposes into different components, leading to structural and morphological changes. However, current knowledge of the interface upon decomposition, such as the Li/LiPON interface, is limited, particularly at the atomic level. Here, we use first-principles calculations to elucidate the interfacial stability and structural properties of possible interfaces formed between the lithium-metal electrode and the decomposition products of LiPON. Through a systematic study and comparison of these interfaces, we have identified an interfacial stability sequence of Li/Li2O > Li/Li3N > Li/Li3P > Li/Li3PO4, suggesting that the lithium-metal anode will predominantly form an interface with Li2O after the decomposition of LiPON. Moreover, the low interfacial energy and high work of adhesion of Li/Li2O suggest that the formation of a Li/Li2O interface in LiPON may promote interfacial stability and potentially inhibit the defect and dendrite formation at the interface. This provides an explanation for the known compatibility of LiPON with lithium-metal anodes. Our findings reveal the critical role of the Li/Li2O interface formation after the decomposition of LiPON at the Li/LiPON interface, which encourages further investigation and design of the lithium-metal anode/SE interface in all solid-state batteries.