The self-discharge mechanism of LiNi0.4Mn1.6O4, investigated by electrochemical methods, is mostly attributed to oxidative electrolyte decomposition due to the high lithium (de-)insertion potentials, since the material insertion capacity appears to be fully reversible upon subsequent galvanostatic cycling. A series of 40 different compounds, such as for instance fluorinated ethylene carbonate, 1,3-propane sultone, lithium bis(oxalato)borate (LiBOB), or a variety of ionic liquids, was investigated as suitable electrolyte additives to form a stable LNMO/electrolyte interphase in order to prevent the self-discharge by the continuous oxidative electrolyte decomposition. Among these, only one compound, namely succinic anhydride, revealed to have a beneficial effect on the self-discharge of LNMO based cathodes, while showing an enhanced coulombic efficiency and a decreased capacity loss per cycle. Additionally, the modification of the LNMO particles surface by adding succinic anhydride to the electrolyte was confirmed by performing ex situ SEM and XPS analysis of galvanostatically cycled electrodes.