Li−CO2 batteries are explored as promising power systems to alleviate environmental issues and to implement space applications. However, sluggish cathode kinetics of CO2 reduction/evolution result in low round-trip efficiency and poor cycling stability of the fabricated energy-storage devices.Herein, we design a double-layer solid electrolyte to decrease interfacial resistance. Li-CO2 battery with high stability and energy density was developed using Li1.3Al0.3Ti1.7(PO4)3 (LATP) as the solid-state electrolyte and a polyethylene oxide (PEO) polymer electrolyte film together. The oxide solid electrolyte LATP has temperature stability and physical solidity, but it has a metal substitution reaction with lithium metal and a low interfacial stability with the electrode. However, this drawback can be solved by using the polymer electrolyte PEO to avoid direct contact between the lithium metal electrode and LATP. The mechanism of the Li-CO2 battery, a carbon capture technology, is used, and the characteristics of the oxide solid electrolyte and polymer electrolyte are combined to suggest a new solution for improving the stability and performance of the battery.