Layered lithium metal oxide cathodes typically exhibit irreversibility during the first cycle in lithium cells when cycled in conventional voltage ranges (e.g., 3-4.3 V vs. Li+/Li). In this work, we have studied the first-cycle irreversibility of lithium cells containing various layered cathode materials using galvanostatic cycling and in situ synchrotron X-ray diffraction. When cycled between 3.0 and 4.3 V vs. Li+/Li, the cells containing LiCoO2, LiNi0.8Co0.15Al0.05O2, and Li-1.048(Ni1/3Co1/3Mn1/3)(0.952)O-2 as cathodes showed initial coulombic efficiencies of 98.0, 87.0, and 88.6%, respectively, at relatively slow current (8 mA/g). However, the "lost capacity" could be completely recovered by discharging the cells to low voltages (< 2 V vs. Li+/Li). During this deep discharge, the same cells exhibited voltage plateaus at 1.17, 1.81, and 1.47 V, respectively, which is believed to be associated with formation of a Li2MO2-like phase (M = Ni, Co, Mn) on the oxide particle surface due to very sluggish lithium diffusion in Li epsilon MO2 with epsilon -> 1 (i.e., near the end of discharge). The voltage relaxation curve and in situ X-ray diffraction patterns, obtained from a Li/Li-1.048(Ni1/3Co1/3Mn1/3)(0.952)O-2 cell, showed that the oxide cathode reversibly returned to its original state [i.e., Li-1.048(Ni1/3Co1/3Mn1/3)(0.952)O-2] during relaxation following the deep discharge to achieve 100% cycle efficiency.