At that redox potential, the sodium content is about 0.5 in the NaMNO structure, the conversion of Mn 3+ to Mn 4+ is completed and Ni 2+ starts to be oxidized to Ni 3+ . This observed behavior is reproducible over several cycles and is found for different cells (see comparison Figure SI-7 in theSupporting Information). It seems plausible that the overlap is not a coincidence and reflects the properties of the electrode at this specific potential. For example, a certain catalytically active site is only present at potentials lower than 3.3 V during charging. This could be Mn 3+ , which is known to be a good oxidizing catalyst in other fields due to its Jahn Teller distortion , as well as the dissolution of Mn 2+ from the disproportion of Mn . These processes might be the cause of the gas evolution at these potentials. On the other hand, one would also expect