High-Stability Lithium Metal Batteries Enabled by a Tetrahydrofuran-Based Electrolyte Mixture

There has been significant interest from academic and industrial sectors to use lithium metal anodes in energy storage devices due to their much higher energy density (3860 mAh/g) compared with their conventional, graphite-based counterparts. However, the safety and inefficiency concerns arising from lithium dendrite formation on these anodes during operation have prohibited their widespread adoption. This study focuses on reducing the dendritic tendencies of lithium anodes by forming a LiF-rich surface layer in situ on the lithium metal, designed specifically to facilitate uniform lithium diffusion and nucleation. The LiF-rich solid electrolyte interphase (SEI) results from the employment of a tetrahydrofuran-based electrolyte mixture (1.0 M LiFSI-THFMix). Li||Li symmetric cells with this type of electrolyte show remarkable performance, cycling stably for over 1700+ h at a current density of 0.5 mA cm–2. To elucidate the influence of the electrolyte on the resulting chemical composition of the SEI, a combination of time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS) was applied. Through the systematic analysis of the electrolyte’s ionic properties, the resulting SEIs’ chemical properties, and their combinative electrochemical properties, this study aims to demonstrate the merit of tetrahydrofuran-based electrolytes for lithium metal batteries.