The invention relates to an improved lithium-air battery. The battery includes a negative electrode and a positive electrode separated by an electrolyte, wherein the negative electrode consists of a film of metal material selected from among lithium and lithium alloys, the positive electrode includes a film of a porous carbon material on a current collector, and the electrolyte is a solution of lithium salts in a solvent. The battery is characterized in that the surface of the negative electrode opposite the electrolyte has a passivation layer containing Li
2 S, Li
2 S
2 O
4 , Li
2 O, and Li
2 CO
3 , the passivation layer being richer in sulfur compound on the surface thereof that is in contact with the electrolyte. The battery is obtained by means of a method consisting of producing the positive electrode, the electrolyte, and a film of the metal material for forming the negative electrode, and assembling the positive electrode, the electrolyte, and the film of metal material. The method is characterized in that it includes a step of subjecting the film of metal material to a gaseous atmosphere containing SO
2 , before or after the assembly thereof with the positive electrode and the electrolyte.