The electrochemical properties of BiOF-coated 5 V spinel Li[Ni0.5Mn1.5]O-4 were investigated at elevated temperatures (55 degrees C). As observed by scanning and transmission electron microscopy, BiOF nanolayers with similar to 10 nm thickness were coated on the surface of Li[Ni0.5Mn1.5]O-4. The BiOF coating layer protected the surface of the active materials from HF generated by the decomposition of LiPFG in the electrolyte during electrochemical cycling. The dissolution of transition metal elements was also suppressed upon cycling. Therefore, the capacity retention of the BiOF-coated Li[Ni0.5Mn1.5]O-4 was obviously improved compared to the pristine Li[Ni0.5Mn1.5]O-4 at 55 degrees C. (C) 2009 Elsevier B.V. All rights reserved.