Achieving a high-specific-energy lithium-carbon dioxide battery by implementing a bi-side-diffusion structure

Li-CO2 batteries are one of the most promising electrochemical systems owing to the high theoretical specific energy and the CO2 capture ability. However, performance is usually reported in terms of the material level. Herein, the performance evaluation from the cell level is conducted. A pouch battery with size of 2 × 1.5 × 0.029 cm3 is developed with a bi-side-diffusion structure to maximize the area of CO2 transport and a buckypaper electrode to ensure CO2 reduction reaction efficiently. By regulating the wetting states of the gas-diffusion layer, the practical specific energy is experimented to be in the range of 313.76 ∼ 614.65 Wh kg−1, and the specific power corresponds to be 2.15 ∼ 3.08 W kg−1. Further, a two-dimensional model is established to predict the cell-level performance considering the battery components, package designs, and working conditions. The results demonstrate that through moderating the electrode loading of 1.8 mg cm−2 and the gas-diffusion layer thickness of 140 μm, designing the package with a high open ratio of 0.7 and three windows, and optimizing the operating conditions with a low current density of 0.1 mA cm−2 under high CO2 pressure of 1 atm, the specific energy can reach 487.26 ∼ 795.88 Wh kg−1, and the specific power consequently increases to be 12.34 ∼ 17.90 W kg−1. This work is favorable for not only constructing high-specific-energy Li-CO2 batteries but also guiding the pack and module designs.