In situ synchrotron x-ray diffraction investigations of LiCuxMn2-xO4 surface coated LiMn2O4 spinel cathode material during charge with various rates

The precursor of LiMn2O4 was calcined at 600 degrees C for 10 h to form the semicrystallite LiMn2O4 and mixed with Cu(CH3COO)(2) in deionized water. The mixture powders were then calcined at 870 degrees C for 10 h to synthesize LiCuxMn2-xO4-coated LiMn2O4 composite. The phase transformation of both base LiMn2O4 and LiCuxMn(2-x)O(4)-coated LiMn2O4 during charging at 0.1, 0.5, and 1 C rate from 3 to 4.5 V was confirmed by the in situ synchrotron X-ray diffractometer. The plateau potential difference between the base LiMn2O4 and LiCuxMn2-xO4-coated LiMn2O4 composite was 50 mV. The decrease of the plateau can be related to the fact that the kinetics of the LiCuxMn2-xO4-coated LiMn2O4 composite cathode material was faster than that of the uncoated material. The cyclic voltammograms of two cells using the LiCuxMn2-xO4-coated LiMn2O4 composite and the base composite as the working electrodes and lithium metal as the counter electrode was applied to measure the oxidation and reduction reaction of the 2016 coin cell during charge and discharge with a rate of 0.1 mV/s from 3 to 4.5 V. Both uncoated LiMn2O4 and LiCuxMn2-xO4-coated LiMn2O4 composite displayed two pairs of well-separated redox peaks, corresponding to two voltage plateaus. (c) 2006 The Electrochemical Society.