Structure and electrochemical performance of CaF2 coated LiMn1/3Ni1/3Co1/3O2 cathode material for Li-ion batteries

CaF2-coated LiMn1/3Ni1/3Co1/3O2 cathode material is prepared via a wet chemical process followed by a solid state reaction. High-resolution transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) show that the well coated CaF2 layer has a thickness of 4-8 nm, and no interaction of chemical bonding is observed. The CaF2-coated LiMn1/3Ni1/3Co1/3O2 02 exhibits discharge capacity retention of 98.1% at 0.1C after 50 cycles and high initial discharge capacity of 146.3 mAh g(-1) at 5 C. Furthermore, even at an elevated charge-discharge rate of 5 C, capacity retention maintains above 85%. Electrochemical impedance spectroscopy (EIS) shows that the CaF2 coating can stabilize the surface structure and reduce the charge transfer resistance. The CaF2 modification has a promising application in improving the performance of layered oxide cathode materials for Li-ion batteries. (C) 2012 Elsevier Ltd. All rights reserved.