P2-Na2/3[Fe1/2Mn1/2]O2 is a promising high energy density cathode material for rechargeable sodium-ion batteries, but its poor long-term stability in the operating voltage window of 1.5–4.25 V vs Na+/Na hinders its commercial application. Here, the authors use a combination of electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy, and DFT calculations to investigate the origin of the capacity fading, which is attributed to an increase in bulk electronic resistance at high voltage that, among other factors, is nested in a structural phase transition.
- Maider Zarrabeitia
- Francesco Nobili
- Miguel Ángel Muñoz-Márquez
