Nonflammable and High-Voltage-Tolerated Polymer Electrolyte Achieving High Stability and Safety in 4.9 V-Class Lithium Metal Battery.

High-voltage polymer electrolytes play important roles in achieving high-energy-density polymer electrolyte-based batteries, but the pace of progress moves slowly, since oxidation-resistant polymer electrolytes at high voltages are rarely obtained. Herein, we reported a nonflammable and high-voltage-tolerated polymer electrolyte (HVTPE) with extended voltage of 5.5 V. The obtained HVTPE has lower HOMO energy indicating a higher antioxidation ability, which avoids the decomposition and depletion of electrolyte near the cathode. Significantly, the HVTPE-based 4.45 V-class LiCoO2 battery delivered a high capacity of 173.2 mA h g-1 at 0.05 C. Using 4.9 V-class LiNi0.5Mn1.5O4 as a cathode, the battery exhibited stable cycling performance. Moreover, HVTPE showed a high modulus of 2.3 GPa, which can efficiently restrain the penetration of Li dendrites, and desirable nonflammable feature, leading to the enhanced safety based on polymer electrolytes. The current work opens new avenues to realize high-voltage polymer electrolyte-based batteries with high safety.