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

• Bi-side diffusion structure maximizes transport areas of CO 2 by a folded layer. • The specific energy of Li-CO 2 battery is the range of 313.76 ∼ 614.65 Wh kg −1 . • A two-dimensional model is developed to predict the cell-level performance. • The predication band is proposed depicting the wetting state in reality. • The specific energy and power improve by 30%-56% and 500%, respectively. Li-CO 2 batteries are one of the most promising electrochemical systems owing to the high theoretical specific energy and the CO 2 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 cm 3 is developed with a bi-side-diffusion structure to maximize the area of CO 2 transport and a buckypaper electrode to ensure CO 2 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 CO 2 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-CO 2 batteries but also guiding the pack and module designs.