Lithium–Air Batteries Using SWNT/CNF Buckypapers as Air Electrodes

Abstract

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 20μm20μm with a discharge current density of 0.1mA/cm20.1mA/cm2 ; however, it was reduced to 400 mAh/g when the thickness of the air electrode was increased to 220μm220μm . For a 66μm66μm thick air electrode, the discharge capacity decreased from 1600 to 340 mAh/g when the discharge current density increased from 0.1 to 0.5mA/cm20.5mA/cm2 . 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.