High-energy ball milling is performed on Li1.1Mn1.95Fe0.05O4 spinel material, synthesized by sol-gel method for lithium rechargeable battery, at different durations to obtain nanopowders of finite size distributions. The powders are investigated by means of scanning electron microscopy, particle size distribution, and X-ray diffraction (XRD) measurements. The structural analysis of the powders is performed to investigate the effect of milling on the particle size, crystallite size, and lattice strain. The scanning electron micrographs and size distribution measurements show that the particle size decreases with the increase in milling duration. The XRD results show that the widths of the diffraction peaks increase with the decrease of particle size (increase of milling duration). This broadening is analyzed according to Scherrer, Williamson-Hall, and Halder-Wagner methods. Peak broadening is attributed to contributions of crystallite size and lattice strain. While reducing the particle and crystallite sizes is desirable to achieve higher specific capacity and energy density of the battery active material, lattice strain leads to material degradation and a reduced capacity retention. Thus, when performing mechanical milling, lattice strain should be taken seriously into consideration to optimize the milling parameters and to enhance the materials electrochemical performance.