Highly salt-concentrated electrolyte comprising lithium bis(fluorosulfonyl)imide and 1,3-dioxolane-based ether solvents for 4-V-class rechargeable lithium metal cell

Electrolytes compatible with lithium metal (Li) anode and cathode materials are regarded as one of the most crucial components toward the practical deployment of rechargeable lithium metal batteries (RLMBs). Herein, we report a highly salt-concentrated electrolyte (SCE) comprising lithium bis(fluorosulfonyl)imide (LiFSI) and 1,3-dioxolane (DOL)-based ether solvents for stable cycling of 4-V-class rechargeable Li cells. The selective addition of 1,8-diazabicyclo(5.4.0)undec‑7-ene (DBU) is capable of suppressing the ring-opening polymerization of DOL. The resulting LiFSI-DOL-based SCE shows excellent chemical stability (150 days), good anodic stability (ca. 5.0 V vs. Li/Li+), and decent ionic conductivity (1.3 mS cm−1) at room temperature. Using the LiFSI-DOL-based SCE, the Li || Cu cells exhibit dendrite-free Li deposition/dissolution processes with high Coulombic efficiencies (> 99%), and the Li || LiNi1/3Mn1/3Co1/3O2 cell shows good capacity retention (81% after 400 cycles). These results strongly suggest the feasibility of the LiFSI-DOL-based SCE as electrolyte for 4-V-class RLMBs.