Dependence of Li content on crystal structure during the charge-discharge process of LiMn1.5Ni0.5O4 as a cathode material for 5 V class lithium secondary battery

We investigated the crystal structure change during the charge-discharge process of LiMn1.5Ni0.5O4 as a 5 V class cathode active material, which was prepared by the sol-gel method. The lithium content of Li1-xMn1.5Ni0.5O4 (x = 0.5, 0.7, 1.0) was controlled by electrochemical lithium extraction. The crystal structure was determined by Rietveld analysis using powder neutron diffraction. As a result, all samples consisted of three phases (space group: P4(3)32) of different lattice constant and Ni valences. The each phase showed a different distortion of the Mn,Ni (12d)-O octahedral site and the Madelung energy.