Composite Hybrid Quasi-Solid Electrolyte for High-Energy Lithium Metal Batteries

Exploring quasi-solid electrolytes with superior ionic conductivities, wide electrochemical stability window, desirable compatibility toward lithium metal, and facile processability for high-energy lithium metal batteries remains a challenge. In this work, all of these issues are fully addressed via a composite hybrid design, of which poly(ethylene oxide) (PEO) is used as a polymeric host and guarantees the interfacial compatibility toward lithium metal, highly conductive and thermally stable ionogel aims at suppressing PEO crystallization and enhancing conductivity, and garnet conductor enhances mechanical and electrochemical stabilities. Such a composite hybrid design yields the required quasi-solid electrolyte, which not only shows a high ionic conductivity of 7.4 × 10-4 S cm-1 at 25 °C but also extends the electrochemical stability window to 5.5 V vs Li/Li+, demonstrated with the interacted and monolithic structure of the composite hybrid quasi-solid electrolyte by XPS. Moreover, the composite hybrid quasi-solid electrolyte suppresses dendrite growth with a current density up to 0.7 mA cm-2. The quasi-solid Li∥LiNi0.5Co0.2Mn0.3O2 and Li∥LiFePO4 cells using this composite hybrid quasi-solid electrolyte are demonstrated. This study suggests that engineering integration of ionogel, polymer, and inorganic conductor offers an alternative to explore new electrolytes for lithium metal batteries.