Solvent–Solvent Interaction Mediated Lithium-Ion (De)intercalation Chemistry in Propylene Carbonate Based Electrolytes for Lithium–Sulfur Batteries

Reversible lithium-ion (de)intercalation in the carbon-based anodes using ethylene carbonate (EC) based electrolytes has enabled the commercialization of lithium-ion batteries, allowing them to dominate the energy storage markets for hand-held electronic devices and electric vehicles. However, this issue always fails in propylene carbonate (PC) based electrolytes due to the cointercalation of Li⁺-PC. Herein, we report that a reversible Li⁺ (de)intercalation could be achieved by tuning the solvent-solvent interaction in a PC-based electrolyte containing a fluoroether. We study the existence of such previously unknown interactions mainly by nuclear magnetic resonance (NMR) spectroscopy, while the analysis reveals positive effects on the solvation structure and desolvation process. We have found that the fluoroether solvents interact with PC via their δ^-F and δ⁺H atoms, respectively, leading to a reduced Li⁺-PC solvent interaction and effective Li⁺ desolvation followed by a successful Li⁺ intercalation at the graphite anodes. We also propose an interfacial model to interpret the varied electrolyte stability by the differences in the kinetic and thermodynamic properties of the Li⁺-solvent and Li⁺-solvent-anion complexes. Compared to the conventional strategies of tuning electrolyte concentration and/or adding additives, our discovery provides an opportunity to enhance the compatibility of PC-based electrolytes with the graphite anodes, which will enable the design of high-energy density batteries (e.g., Li-S battery) with better environmental adaptabilities.