With an objective of understanding the differences in the capacity retention behavior of LiMn2O4 and the cation-substituted LiMn2-yMyO4 (M = Li, Co, and Ni) spinel oxides, the peak broadening in the X-ray diffraction patterns on extracting lithium has been analyzed. An analysis of the LiMn2O4 and LiMn2-yMyO4 samples before and after treating at room temperature with acid or an oxidizing agent (NO2BF4) or at 55degreesC with electrolyte reveals that the LiMn2O4 system experiences a larger amount of microstrain during these treatments (lithium extraction) compared to the LiMn2-yMyO4 systems. Additionally, the two cubic phases formed at lower lithium contents have a larger difference in lattice parameters in Li1-xMn2O4 compared to Li1-xMn2-yMyO4. The observation of nearly the same amount of manganese dissolution in LiMn2O4 and LiMn2-xMyO4 Suggests that the faster capacity fade in the former is due to the development of microstrain and the larger difference in lattice parameters between the two cubic phases. (C) 2002 The Electrochemical Society.