With an objective to develop a better understanding of the origin of high voltage (>4.5 V) capacities, the electrochemical behaviors of a number of spinel lithium manganese oxides with and without other transition metal ions have been studied and compared. The oxides investigated are LiMn2−y M y O4 (M=Co, Ni, and Cu), LiMn2−y−z M y Li z O4, LiMn2−y Li y O4, Li2Mn4O9−δ , and Li4Mn5O12. The LiMn2−y Li y O4 (0.05≤y≤0.12) oxides are found to exhibit capacity above 4.5 V although they do not contain other transition metal ions. In the case of Li2Mn4O9−δ and Li4Mn5O12, charging above 4.5 V is found to increase the discharge capacity below 4.5 V. While both LiMn2−y Co y O4 and LiMn2−y−z Co y Li z O4 show a similar behavior at >4.5 V, LiMn2−y Ni y O4 and LiMn2−y−z Ni y Li z O4 differ significantly. Also, while LiMn1.9Li0.1O4 and LiMn1.8Co0.2O4 show a rapid decrease in their discharge capacity above 4.5 V with rest time allowed in the fully charged state (self-discharge), LiMn2−y Ni y O4 does not suffer from such a difficulty. Additionally, long-range periodicity with good crystallinity is found to be essential to observe discharge capacity above 4.5 V. The results are explained on the basis of the participation of the O2−:2p band in the redox process and the relative positions of the other transition metal ion redox energies with respect to the top of the O2−:2p band.