Highly safe and wide-temperature operating high-voltage LiCoO2/Li metal batteries is of far-reaching significance for portable electronics. However, 4.45V-class LiCoO2/Limetal batteries based on liquid electrolytes typically suffer from severe electrochemical decomposition, lithium dendrites growth and electrolyte leakage in harsh temperature conditions, which can result in fast capacity decay, poor life-span and potential safety risk. Herein, we demonstrated highly safe and wide-temperature operating 4.45 V-class LiCoO2/Li metal batteries by employing poly (butyl vinyl ether-alt-maleic anhydride) based polymer electrolyte (PBM-GPE). Such polymer electrolyte significantly improved long-term cycling stability of 4.45 V-class LiCoO2/Li metal batteries at wide-temperature (96% capacity retention after 150 cycles at 25 degrees C, 85.2% capacity retention after 100 cycles at 80 degrees C, 80% capacity retention after 10 cycles at -20 degrees C, respectively). Further studies indicated that this polymer electrolyte could inhibit the growth of lithium dendrites on Li anode and suppress the dissolution of cobalt ion from LiCoO2 cathode, which enabled the batteries with excellent cycle performance in a wide range of temperature. More importantly, a red LED could be powered by PBM-GPE based 4.45 V-class LiCoO2/Li pouch battery even after corner being cut off, which could be ascibed to the superior anti-leakage and gum-like characteristics of PBM-GPE. (c) 2019 The Electrochemical Society.