Preparation of three-dimensional hierarchical porous carbon microspheres for use as a cathode material in lithium-air batteries

Urea-formaldehyde resin microspheres were prepared by a polymerization method using urea and formaldehyde as the raw materials and hydrochloric acid as the catalyst. The microspheres were pre-oxidized and carbonized to obtain carbon microspheres, then activated with KOH. The morphology and pore structure of products were characterized by SEM, TEM and N₂ adsorption. Results indicate that the microstructure of the microspheres is highly dependent on the mass ratio of urea to formaldehyde and the concentration of hydrochloric acid. The specific surface area of the carbon microspheres is 498 m²·g^-1, which is increased to 827 m²·g^-1 after KOH activation. When used as the electrode materials of lithium-air batteries, the initial charge and discharge capacities are 2 017 and 2 075 mAh·g^-1, respectively, at a current density of 100 mA·g^-1.