Long-life graphite-lithium sulfide full cells enabled through a solvent Co-intercalation-free electrolyte design.

Abstract

Graphite (Gr) is the predominant anode material for current lithium-ion technologies. The Gr anode could offer a practical pathway for the development of lithium-sulfur (Li-S) batteries due to its superior stability and safety compared to Li-metal. However, Gr anodes are not compatible with the conventional dilute ether-based electrolytes typically used in Li-S systems. Here, an optimized ether electrolyte is presented, utilizing 1 M lithium bis(trifluoromethanesulfonyl)-imide (LiTFSI) in 1,3-dioxolane (DOL)/1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropylether (TTE). Without altering the salt concentration, this electrolyte regulates the solvation structure and promotes the formation of a robust solid-electrolyte interphase (SEI) layer, leading to a significant improvement in the cyclability of Gr anodes. Meanwhile, the DOL/TTE electrolyte maintains adequate kinetics for the sulfur cathode, enabling its pairing with Gr anodes without any cathode modification. The cell with a Gr anode delivers a reversible discharge capacity of 515 mA h g^-1 after 400 cycles at C/10 rate, in contrast to only 143 mA h g^-1 for the Li-metal anode cell. Moreover, a Gr || Li₂S full cell with a negative-to-positive capacity (N/P) ratio of 1.05 and a Li₂S loading of 3 mg cm^-2 shows a stable 58% capacity retention after 400 cycles.