A sulfolane-based high-voltage electrolyte with dispersed aggregates for 5 V batteries

High concentrated electrolytes (HCEs) and local high concentrated electrolytes (LHCEs) energize the development of high-energy density lithium batteries, which are attributed to the cation-anion aggregates (AGGs) formed at a high salt concentration that are favorable to form a robust inorganic-derived solid electrolyte interface (SEI) on the lithium surface. However, how to obtain more AGGs at a low salt concentration still faces great challenges. Herein, we report a dispersed AGG electrolyte (DAE) to enhance the content of AGGs at a common salt concentration via two steps: (1) LiPF6, which has a relatively weak dissociation in sulfolane, is chosen to form a large three-dimensional network structure (AGG clusters). (2) the dispersion of AGG clusters into smaller AGGs is achieved by adding hydrofloroether (HFE). By comparing a series of HFEs, we find that HFEs with long chains and high fluorination have a preferable ability to disperse AGGs. As a result, the electrolyte achieves 99.5% Coulomb efficiency and dendrite-free Li anode in LNMO||Li cells with 500 cycles at a high cutoff voltage of 4.95 V. This strategy provides a new way to develop electrolytes for next-generation high-performance batteries.