LiMn₂ O ₄ Core Surrounded by LiCo _x Mn_2 − x  O ₄ Shell Material for Rechargeable Lithium Batteries: Synthesis and Characterization

We demonstrate a novel method for the synthesis of LiMn 2 O 4 core surrounded by LiCo x Mn 2 − x O 4 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 LiMn 2 O 4 particles. X-ray diffraction studies revealed that cobalt was doped into the lattice of the LiMn 2 O 4 particles. X-ray absorption fine structure analysis further demonstrated that cobalt was doped mainly on the surface of the LiMn 2 O 4 particles. LiCo x Mn 2 − x O 4 solid solution thus formed on the surface of the LiMn 2 O 4 particles greatly enhanced the initial capacity, capacity retention, and rate capability of the spinel LiMn 2 O 4 . The enhanced initial capacity of the LiMn 2 O 4 core / LiCo x Mn 2 − x O 4 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. © 2002 The Electrochemical Society. All rights reserved.