The chemical evolution of solid electrolyte interface in sodium metal batteries

作者：Lina Gao, Juner Chen, Qinlong Chen, Xueqian Kong · 发表于：Science Advances · 年份：2022 · DOI：10.1126/sciadv.abm4606 · 被引用次数：171 · 研究领域：Advanced Battery Materials and Technologies、Advancements in Battery Materials、Inorganic Chemistry and Materials

The solid electrolyte interface (SEI) formed on the anode is one of the key factors that determine the life span of sodium metal batteries (SMBs). However, the continuous evolution of SEI during charging/discharging processes complicates the fundamental understanding of its chemistry and structure. In this work, we studied the underlying mechanisms of the protection effect offered by the SEI derived from sodium difluoro(oxalato)borate (NaDFOB). In situ nuclear magnetic resonance (NMR) shows that the prior reduction of DFOB anion contributes to the SEI formation, and it suppresses the decomposition of carbonate solvents. Depth-profiling x-ray photoelectron spectroscopy and high-resolution solid-state NMR reveal that the DFOB anion is gradually turned into borate and fluoride-rich SEI with cycling. The protection effect of SEI reaches the optimum at 50 cycles, which triples the life span of SMB. The detailed investigations provide valuable guidelines for the SEI engineering.