Improved electrochemical properties of BiOF-coated 5V spinel Li[Ni_(0.5)Mn_(1.5)]O_4 for rechargeable lithium batteries

摘要

The electrochemical properties of BiOF-coated 5 V spinel Li[Ni_(0.5)Mn_(1.5)]O_4 were investigated at elevated temperatures (55℃). As observed by scanning and transmission electron microscopy, BiOF nanolayers with ～10nm thickness were coated on the surface of Li[Ni_(0.5)Mn_(1.5)]O_4. The BiOF coating layer protected the surface of the active materials from HF generated by the decomposition of LiPF_6 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[N_(0.5)Mn_(1.5)]O_4 was obviously improved compared to the pristine Li[Ni_(0.5)Mn_(1.5)]O_4 at 55℃.