LiMn2O4 core surrounded by LiCoxMn2-xO4 shell material for rechargeable lithium batteries -: Synthesis and characterization

We demonstrate a novel method for the synthesis of LiMn2O4 core surrounded by LiCoxMn2-xO4 shell material for rechargeable lithium batteries. Surface and composition analysis by electron spectroscopy for chemical analysis and inductively coupled plasma method, indicated that cobalt mostly distributed on the surface of the LiMn2O4 particles. X-ray diffraction studies revealed that cobalt was doped into the lattice of the LiMn2O4 particles. X-ray absorption fine structure analysis further demonstrated that cobalt was doped mainly on the surface of the LiMn2O4 particles. LiCoxMn2-xO4 solid solution thus formed on the surface of the LiMn2O4 particles greatly enhanced the initial capacity, capacity retention, and rate capability of the spinel LiMn2O4. The enhanced initial capacity of the LiMn2O4 core/LiCoxMn2-xO4 shell material may be due to the involvement of Co in the charging/discharging behavior and the improved capacity retention and the rate capability were most probably due to less cation disordering during charge/discharge cycling experiments at low as well as at high C-rates. (C) 2002 The Electrochemical Society.