LiCuJvtn2_O4 Spinels (0.1 x 0.5): A New Class of Cathode Materials for Li Batteries II. In Situ Measurements

Electrochemical data obtained from lithium cycling in LiCuMn2..O4 spinels (0.1 x 0.5) show a remarkable, high-ly reversible, electrochemical cycling behavior at 4.9 V. In situ X-ray absorption near edge structure spectroscopy revealed that this ultrahigh voltage is due to the existence of the Cu2t/Cu2 redox couple. The origin of the high stability at the 5 V region was studied with the in situ X-ray diffraction technique. It was found that the unit cell dimension undergoes min-imal change during charge-discharge cycles at the 5 V plateau. Infroduction In our earlier communications12 we reported on novel electroactive materials, LiCu4VIn,O4 (0.1 x 0.5). The electrochemical data obtained from lithium cells containing these materials as cathodes (positive electrodes) showed that lithium ions can be extracted from the spinel structure in two main potential regions: the first, at the sloping region of 3.9 to 4.3 V, was attributed to the oxidation of Mn2t to Mn", whereas the second potential plateau, observed at 4.