Synthesis and electrochemical performance of YF3-coated LiMn2O4 cathode materials for Li-ion batteries

Spinel LiMn2O4 cathodes were coated with 1 mol% YF3. X-ray diffraction (XRD) analyses showed that Y and/or F did not enter the lattice of the LiMn2O4 crystal. Transmission electron microscopy (TEM) showed that a compact YF3 layer of 5–20 nm in thickness was coated onto the surface of LiMn2O4 particles. Scanning electron microscopy (SEM) observation showed that the YF3 coating caused the agglomeration of LiMn2O4 particles. The cycling test demonstrated that the YF3 coating can improve the electrochemical performance of LiMn2O4 at both 20 and 55°C. Moreover, YF3-coated LiMn2O4 exhibited an improved rate capability compared with the uncoated one at high rates over 5C. The immersion test in electrolytes showed that YF3-coated LiMn2O4 is more erosion resistant than the uncoated one.