New findings:: structural changes in LiAlxMn2-xO4

LiAl0.1Mn1.9O4 was synthesized using LiOH, Al(NO3)(3) and two different Mn sources (gamma -MnOOH and Mn3O4). The X-ray diffraction (XRD) analyses of the prepared materials revealed identical crystalline phases (cubic, Fd (3) over bar m). The two LiAl0.1Mn1.9O4 materials presented very good cycling performance in the 4 V region, but the LiAl0.1Mn1.9O4 prepared using Mn3O4 showed a severe capacity fading in the 3 V region. It showed a mixed cubic and tetragonal phase which was detected from the XRD spectrum of the material discharged down to 2.2 V after 50 cycles. Meanwhile, it was observed that LiAl0.1Mn1.9O4 synthesized using gamma -MnOOH has only a tetragonal phase after the electrochemical test under the same conditions and had a higher capacity retention rate in the 3 V region. We now report the extraordinary electrochemical performances from the two LiAl0.1Mn1.9O4 materials prepared using different manganese sources. (C) 2001 Elsevier Science B.V. All rights reserved.