Metal fluoride materials, through the use nanocomposites, recently appear as potential candidates as next generation high energy density positive electrodes for Li-ion batteries. The reversible conversion reaction of MFx enables the utilization of all the redox states of the metal in a reversible manner in the positive electrode. The theoretical (3 e- transfer) capacity of FeF3 to LiF + Fe, is 718 mAh/g, which is considerably greater than that of LiCoO2, 274 mAh/g. The role that parameters such as the ionic conductivities and the unidentified new, intermediate, and reconverted nano-structures, play in controlling the performance is far from clear. This proposal seeks to study the conversion reaction mechanism for C-FeF3 nanocomposites by PDF and RMC calculations on total scattering neutron data. This study will be supported by PDF on synchrotron X-ray and solid state MAS NMR data.