5 VOLT PLATEAU IN LIMN2O4 THIN-FILMS

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 obs erved 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 plate aus varies from film to film. After charging to 5.3 V, the cathodes we re irreversibly changed: the capacity of the 4 V plateau increased by as much as 50%, but the cell resistance also increased significantly d ue to degradation of the cathode.