Li-air cells based on Li foil as an anode electrode, freestanding carbon nanotube/nanofiber mixed buckypaper as an air (cathode) electrode, and organic electrolyte were assembled. The air electrode was made with single-wall carbon nanotube (SWNT) and carbon nanofiber (CNF) without any binder. The discharge capacity was strongly dependent on both the discharge current density and the thickness of the air electrode. A discharge capacity as high as 2500 mAh/g was obtained for an air electrode at a thickness of 20 mu m with a discharge current density of 0.1 mA/cm(2); however, it was reduced to 400 mAh/g when the thickness of the air electrode was increased to 220 mu m. For a 66 mu m thick air electrode, the discharge capacity decreased from 1600 to 340 mAh/g when the discharge current density increased from 0.1 to 0.5 mA/cm(2). The scanning electron microscope images on surfaces of the air electrode from a fully discharged cell showed that the voids at the air side were almost fully filled by the solid deposition; however, the voids at the membrane side were still wide open. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3446852] All rights reserved.