Sulfone electrolyte based quasi-solid-state high-voltage lithium metal batteries enabled by component design and interfacial engineering

Abstract

Sulfone-based electrolyte (SL) as a novel type electrolyte for lithium-ion batteries (LIBs) has attracted increasing attention due to its exceptional high-voltage stability and flame retardancy. However, the polar thionyl groups in sulfone lead to continuous reaction with lithium (Li) metal, and high viscosity of sulfone could decrease its Li⁺ ionic conductivity, which obstructs further application of SL in Li metal batteries (LMBs). Herein, the methylenebisacrylamide (MBA) crosslinked SL, fluorinated ethylene carbonate (FEC) based quasi-solid-state electrolyte (MSFE) was designed to address above problems. By introducing FEC to passivate metallic Li and 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether (OTE) as diluent to decrease viscosity of electrolyte, MSFE exhibits a high ionic conductivity of 1.77 × 10⁻³ S cm⁻¹ and wide electrochemical stability window up to 5.6 V. Therefore, LiCoO₂/MSFE/Li (LCO/MSFE/Li) batteries show a high capacity retention of 95.7 % after 100 cycles under 0.2C. Moreover, formation mechanism and kinetic evolution of the hybrid EEI is revealed via density functional theory (DFT) calculations and in-situ galvanostatic electrochemical impendence spectra (IS-GEIS) coupled with distribution relax time (DRT) technology. Well-formed hybrid EEI prevents the structural degradation of LCO materials and induces uniform deposition of Li-ion to inhibit formation of Li dendrites. This work provides a new insight towards high energy density in-situ polymerized solid LMBs.