Safety-reinforced rechargeable Li-CO₂ battery based on a composite solid state electrolyte

The rechargeable Li-CO₂ battery has been receiving significant attention owing to its merits of high energy density and the efficient utilization of CO₂. However, the widely application is plagued by severe security risks, such as leakage, flammability and lithium dendrites growth due to the use of liquid organic electrolytes. Here, a composite solid state electrolyte consisting of polyethylene oxide (PEO) and 20 wt.% Li₇La₃Zr_1.4Ta_0.6O₁₂ (LLZTO) was prepared and first introduced into Li-CO₂ battery to solve the problems. The composite solid state electrolyte exhibited high ionic conductivity (1.03 × 10^-3 S·cm^-1 at 70 ℃), wide electrochemical window (5 V vs. Li⁺/Li), good mechanical properties and excellent flexibility. Ultimately, the Li symmetric cell with PEO/LLZTO composite solid state electrolyte can operate 1, 500 h at a current density of 0.1 mA·cm^-2. The assembled all-solid-state Li-CO₂ battery behaved a long cycle life of 70 cycles at a current density of 100 mA·g^-1 with fixed capacity of 1, 000 mAh·g^-1. Our work provides new perspective to develop rechargeable all-solid-state Li-CO₂ batteries.