LICUXMN2-XO4 SPINELS LESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-0.5) - A NEW CLASS OF CATHODE MATERIALS FOR LI BATTERIES - II - IN-SITU MEASUREMENTS

Electrochemical data obtained from lithium cycling in LiCuxMn2-xO4 spi nels (0.1 less than or equal to x less than or equal to 0.5) show a re markable, 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 Cu2+/Cu3+ r edox couple. The origin of the high stability at the 5 V region was st udied with the in situ X-ray diffraction technique. It was found that the unit cell dimension undergoes minimal change during charge-dischar ge cycles at the 5 V plateau.