The rechargeable Li–CO2 battery has attracted much attention for energy storage because of the high energy density and efficient utilization of greenhouse gas. However, it’s still suffered by low safety issue of liquid electrolyte. Herein, a composite cathode consisting of CNTs and polymer electrolytes was fabricated by the in-situ polymerization process for the polymer electrolyte-based solid-state Li–CO2 batteries. With the good disper-sion of CNTs and polymer electrolyte, the composite cathode is covered by film-like discharge products Li2CO3. Furthermore, the Li–CO2 battery shows high reversible capacity (～11,000 mAh·g-1), excellent cycle stability (1000 mAh·g-1 for 100 cycles) under low charge potential (<4.5 V), and outstanding rate performances at room temperature, which are much better than those of liquid electrolyte-based battery. Therefore, the polymer electrolyte-based Li–CO2 battery prepared by this strategy can be a promising candidate to meet the demands of high safety and high-performance energy storage devices.