Stable lithium metal batteries enabled by localized high-concentration electrolytes with sevoflurane as a diluent

Abstract

High-voltage lithium metal batteries with routine carbonate-based electrolytes cannot present satisfactory performances due to severe lithium-dendrite growth and side reactions at electrode–electrolyte interfaces. Herein, a localized high concentration electrolyte (LHCE) is designed using fluoromethyl 1,1,1,3,3,3-hexafluoroisopropyl ether (SFE) as an inert diluent in concentrated carbonate electrolyte. The SFE diluent is demonstrated to improve the wettability and conductivity of the electrolyte. The optimized LHCE promotes dense, smooth and elongated electrodeposition of Li metal with a stable LiF-rich solid-electrolyte interphase (SEI) layer. Furthermore, it also leads to a robust and transition metal-free SEI layer at the LiNi_0.8Mn_0.1Co_0.1O₂ (NMC811) cathode side, leading to suppressed cathode particle corrosion and cracking at high voltage. Consequently, the Li‖NMC811 cell achieves a capacity retention of 84% and an average coulombic efficiency over 99% for 300 cycles in the voltage range of 2.7–4.3 V. Our work highlights the benefits of LHCE and provides insights for further electrolyte development of high-voltage lithium batteries.