The properties of graphite/Li[(Ni0.5Mn0.5) x Co y (Li1/3Mn2/3)1/3]O2 (x + y =2/3, y =1/12 and 1/6) Li-ion cells are reported. There is an extended plateau near 4.5V during the first charging of the cells that corresponds to the simultaneous removal of Li and oxygen from the Li[(Ni0.5Mn0.5) x Co y (Li1/3Mn2/3)1/3]O2 (x + y =2/3, y =1/12 and 1/6) electrodes. The release of this oxygen directly within a Li-ion cell has been a cause for concern. However, it was found that subsequent to O2 release, Li-ion cells delivered a high reversible positive electrode specific capacity near 250mAh/g at C/30 between 2.5 and 4.8V, the cells did not display increased irreversible capacity relative to counterparts having Li metal negative electrodes and the cells retained 85% of their initial capacity after 70 cycles at C/6 between 2.5 and 4.6V. Therefore, the O2 released during the first charge does not significantly impact the electrochemical properties of graphite/Li[(Ni0.5Mn0.5) x Co y (Li1/3Mn2/3)1/3]O2 (x + y =2/3) lithium-ion cells.