“Rigid Exterior, Soft Interior” Design Enables High-Voltage Polyether Electrolytes for Quasi-Solid-State Batteries

Abstract

Polyether electrolytes with high Li+ conductivity and excellent interfacial contact have garnered significant attention. Yet further applications of such electrolytes in high-voltage lithium metal batteries are severely hindered by the instability of the electrolyte and electrolyte/electrodes interphases. Here, we report a novel high-voltage polyether electrolyte with a “rigid exterior, soft interior” design, which involves a 3D F-contained network as rigid exterior framework, and a unique solvation structure with intensified Li+-anion coordination as soft interior within the framework. The achieved electrolyte demonstrates an ionic conductivity of 1.13 mS/cm at 25 °C, a Li+ transference number of 0.85, and an extending electrochemical stability window of over 5 V. Besides, such designed polyether electrolyte further induces salt-philic, solvent-phobic interfacial films for stabilizing electrolyte/electrode interphases. An exceptional cyclability in a Li||Li cell for over 4000 hours, and a preferable capacity and cyclability in even 4.6 V Li||LiNi0.8Co0.1Mn0.1O2 (NCM811) quasi-solid-state batteries (QSSBs) are demonstrated. Meanwhile, the resulting 4.3 V Li||LiNi0.5Co0.2Mn0.3O2 QSSB shows a Coulombic efficiency of ~100% and an extremely high capacity retention of 95.4% after 600 cycles at 3C. A capacity retention of over 96.3% after 400 cycles at 1C are further realized in 4.5 V Li||NCM811 QSSB.