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

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 LiNi_0.5Mn_1.5O₄ 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.