Deactivation of Partially (dis)Charged LNMO in Contact with Water by Electrochemical Protonation of Li_{(1 − x)}Ni_0.5Mn_1.5O₄

Abstract The development of water‐based composite cathode slurries for Li‐ion batteries is hindered by adverse interactions between the battery active material and water. Insights into interactions between H₂O and LiNi_0.5Mn_1.5O₄ (LNMO) are studied using a thin‐film model system. The reactivity of this active material with H₂O is evaluated at different lithiation states, showing that protonation of the active material in aqueous environments is electrochemically driven, rather than a chemical Li⁺/H⁺ ion exchange reaction. The electrochemically driven mechanism describing the protonation of LNMO is only present when the material is in its partially delithiated form. These findings suggest it is possible to cast this material from an aqueous precursor when lithiated, as long as there are no traces of it when the electrochemical delithiation (cell charging) is carried out.