Tailoring Electrolyte Solvation Chemistry toward an Inorganic-Rich Solid-Electrolyte Interphase at a Li Metal Anode

The solid-electrolyte interphase (SEI) is known to dictate the performance of a Li metal anode, where its inorganic compositions are primarily responsible for Li+ conduction, electron insulation, and thus a compact Li deposition. In this work, we formulate a nonflammable and highly fluorinated electrolyte recipe for a highly reversible Li metal anode. By concurrently incorporating the F-donating anions and solvent molecules into the primary Li+ solvation sheath, an inorganic-rich SEI with high F content is produced. The low solvation energy of the tailored solvation sheath further reduces the barrier for Li+ desolvation, contributing to accelerated kinetics under fast charging and subzero conditions. Consequently, dramatic improvements in the Li deposition morphology, Coulombic efficiency (98% over 650 cycles), and Li+ desolvation/transfer kinetics are obtained. Full cells pairing with the commercial LiFePO4 (LFP) and LiNi0.5Co0.2Mn0.3O2 (NCM523) cathodes show stable cyclability at both room-temperature and subzero conditions. Further electrolyte prototypes are showcased to demonstrate the universality of the design principle provided herein.