Anti-corrosive electrolyte design for extending the calendar life of lithium metal batteries

Abstract

Localized high-concentration electrolytes (LHCEs) have been proposed for lithium metal batteries (LMBs) to control the solvation structure of the lithium ions and consequently the solid-electrolyte-interphase (SEI) composition. Although this approach extends the cycle life effectively, the fluorinated diluents in LHCEs severely corrode metallic Li via spontaneous chemical decomposition, which shortens the calendar life. Here, we introduce an LHCE containing hexafluoroisopropyl methyl ether (HFME) as the diluent to which n-hexane has been added. n-Hexane serves as a kinetic barrier in the "swollen" SEI to suppress the Li corrosion by HFME. A galvanostatically cycled full-cell that includes n-hexane, with an 8-hour rest period inserted at the end of each charge, has a markedly improved calendar life compared to its hexane-free counterpart (80.8% retention after 160 cycles vs. 6.0% retention after 46 cycles). This study reveals the usefulness of introducing an inert hydrocarbon to enhance both the cycle life and calendar life of LHCE-based LMBs. This study introduces a cutting-edge electrolyte formulation that mitigates Li metal corrosion, significantly extending the calendar life of LMBs. Based on the SEI swelling model, hydrocarbons kinetically block the highly corrosive F-diluent entry.