In Situ Structural Study of 4V-Range Lithium Extraction/Insertion in Fluorine-Substituted LiMn2O4

The structural features accompanying the lithium extraction/insertion process in a fluorine-substituted spinel oxide with formula LiMn2(O3.74F0.26) were studiedin situusing Bellcore-type plastic batteries directly placed in a synchrotron X-ray beam. The initial material contains two phases, a cubic spinel and a slightly orthorhombically distorted one (major phase). It becomes entirely cubic on extraction of 0.17 Li atoms per formula unit. The lithium extraction reaction around 4 V vs Li/Li+can be divided into three regions as a function of lithium contentx: (1) a single-phase range for 0.59