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 exhibits discharge capacity retention of 98.1% at 0.1 C 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.

► CaF2 is well coated on LiNi1/3Co1/3Mn1/3O2 by a wet chemical method.
► The well coated CaF2 layer has a thickness of 4–8 nm.
► Improved discharge capacity of 146.3 mAh g−1 can be obtained at 5 C (1400 mA g−1).
► 98.1% of capacity is retained after 50 cycles at 0.1 C and 86.5% at 5 C.