The following proposal is aimed to provide new insights into surface passivation mechanism of Si electrodes in Si-O2 batteries and to validate the already published proof of concept where Si stays active as long as the potential remains cathodic to passivation peak potential. The neutron reflectometry is a powerful technique to provide the kinetic behavior of the passivation layer during operando investigations. The thickness and the composition of the surface layer can be measured with non-destructive neutron reflectometry while the Si electrode is being electrochemically studied by cyclic voltammetry and potentiostatic experiments. This novel operando approach will provide important insights into the passivation mechanism of Si which could lead to further developments..