Evaluation of the electrochemical capacity of spinel Li1.0348Mn1.9152Fe0.0494O4 compound from combined X-ray diffraction and particle size distribution measurements

A cathode material of the form Li_1.0348Mn_1.9152Fe_0.0494O₄ was prepared by a sol-gel method for lithium ion batteries. The synthesized material was found to have a pure cubic spinel structure of \( Fd\overline{3}m \) space group. The compound electrochemical capacity was estimated with high accuracy from a combined particle size distribution and X-ray diffraction (XRD) measurements based on considerations of particles sizes, crystal structure, and Li contribution from well-defined unit cells in the compound particles. It was possible to estimate the thickness of the most delithiated region near the particle surfaces at any delithiation depth using a direct and nondestructive procedure. Results showed that most of the attainable capacity in the conventional voltage range originates from the surface region rather than the core of the compound particles. The present analysis is believed to be of some value for estimation of the failure mechanism in cathode compounds, thus assisting the development of Li ion batteries.