Abstract
This study is aimed to explore the effect of fluoride doping and the associated structural transformation on lithium-rich layered cathode materials. The polymeric fluoride source is first adopted for synthesizing lithium intercalated oxide through a newly developed organic precipitation process. A heterostructured spinel/layered composite cathode material is obtained after appreciable fluorination and a superior rate capability is successfully achieved. The fluoride dopant amount and the surface spinel phase are evidenced and systematically examined by various structural spectroscopy and electrochemical analysis. It appears the reversible Ni 2+/4+ redox couple at high voltage regime around 4.8 V because of the formation of spinel LiNi 1/2 Mn 3/2 O 4 phase. The mechanism of "layer to spinel" phase transformation is discussed in detail.