Abstract: The Li-air battery has attracted considerable attention owing to its high energy density, which is approximately 10 times larger than that of a conventional Li-ion battery. Carbon is frequently used as the cathode material because of its stable structure and excellent conductivity. The surface properties and microstructure of carbon nanotubes (CNTs) were modified by KOH activation and its effects on the electrochemical behaviorof CNTs as a cathode material for Li-air batterieswere investigated. Results indicate that the graphitic layer of the CNT outer surface is etched and more edge carbon atoms are exposed after the modification, which generates a CNT-graphene hybrid nanostructure. This hybrid structure provides a large number of active sites that are beneficial for the generation/decomposition of discharge products, leading to a decrease of the charging overpotential and an improvement in cycling stability.