A plateau with a median voltage of similar to 5 V, possibly due to Li+ ions occupying octahedral sites in the spinel structure, has been observed on charging crystalline spinel LiMn2O4 thin-film cathodes to 5.3 V. The total charge extracted from the 4 and 5 V plateaus corresponds to 1 Li/Mn2O4, but the distribution of capacity between the two plateaus varies from film to film. After charging to 5.3 V, the cathodes were irreversibly changed : the capacity of the 4 V plateau increased by as much as 50%, but the cell resistance also increased significantly due to degradation of the cathode.