Formation of a Stable Solid-Electrolyte Interphase at Metallic Lithium Anodes Induced by LiNbO3 Protective Layers

The stability of solid-electrolyte interphase (SEI) surface films at Li-metal anodes is crucial for the safe and durable operation of lithium-metal batteries (LMBs). By combining Li-metal anodes with high-performance Ni-rich transition-metal oxide cathodes, LMBs can meet the goal of a high specific energy density of more than 500 Wh kg–1. However, Li-metal anodes suffer from serious problems, especially the nonuniform lithium deposition and uncontrollable SEI formation. In this work, Li-metal anodes were protected by thin-film LiNbO3 coatings. Full cells composed of protected Li-metal anodes and LiNi0.6Co0.2Mn0.2O2 cathodes were examined electrochemically and by physical characterization methods. Postmortem analyses of pristine and prolonged cycled Li-metal anodes were performed. The results revealed the formation of more stable SEI films at the protected Li-metal anodes in comparison to unprotected electrodes. Consequently, the LiNbO3 layers improved the cycle-life performance of Li-metal anodes in LMBs. Furthermore, X-ray photoelectron spectroscopy (XPS) analyses showed that the reduction of metallic ions stemming from the Ni-rich cathodes was also inhibited by the protective LiNbO3 layers, thereby further controlling the degradation of Li-metal anodes.