Fabrication of long-life quasi-solid-state Na-CO2 battery by formation of Na2C2O4 discharge product

Rechargeable Na-CO 2 batteries are promising energy-storage devices due to their high energy density, environmental friendliness, and cost effectiveness. However, the insulating nature and irreversibility of the Na 2 CO 3 discharge product cause large polarization and poor cyclicity. Here, we report a reversible quasi-solid-state Na-CO 2 battery that is constructed by the synergistic action of a Co-encapsulated N-doped carbon framework catalyst and gel electrolyte to ensure the formation of a highly reversible Na 2 C 2 O 4 discharge product. Experiments and density functional theory calculations indicate that the electron-agglomeration effect of Co nanoparticles enhances CO 2 adsorption and lowers energy barrier, as well as promotes Na 2 C 2 O 4 generation. A gel electrolyte containing an imidazole organic cation is used to inhibit the decomposition of the thermodynamically unstable Na 2 C 2 O 4 . The fabricated Na-CO 2 battery exhibits a high discharge capacity of 3,094 mAh g −1 , a high-rate performance of 1,777 mAh g −1 at a current density of 0.5 mA cm −2 , and excellent cycling performance of 366 cycles (2,200 h).