The battolyser concept is based on an old fashioned nickel iron battery, consisting of a positive nickel(oxy) hydroxide electrode and negative iron (hydroxide) electrode. Research has been performed on the structural changes of the nickel and iron electrode upon charge and discharge. A lot of research can be found for the nickel electrode, but crystal structure studies are few. Much less research is performed on the iron electrode. Therefore the structural changes of the nickel(oxy) hydroxide and iron (hydroxide) electrodes during operation are further researched. Ni(OH)2 exists in the form of an α- or β-modification and NiOOH in a β- or γ-modification. The structure of the nickel(oxy)hydroxide phases has layers of edge-sharing NiO2 octahedra, where in between guest atoms can situate. Conventional nickel electrodes operate mainly between β-Ni(OH)2 and β-NiOOH, so most research focussed on this area. Upon overcharge the γ-NiOOH is formed and when discharging a direct reduction of β-NiOOH and γ-NiOOH into β-Ni(OH)2 occurs. The research on the nickel electrode published in this thesis is compared with a previous discharge study performed by Morishita et al. In their Rietveld refinement of the β-phases an ideal and fault phase model are assumed and the weight fraction of all phases present in the samples at 0, 50, 100 and 150% of state of charge (SOC) are determined. For the iron electrode four phases can be distinguished. The pure Fe in the electrode upon discharge becomes Fe(OH)2, under deep discharge this transforms even further towards FeOOH. For the deactivation process the reaction moves towards magnetite (Fe3O4). First the battery electrodes from the shelf are analysed by SEM-edx , X-ray diffraction and neutron diffraction. Then neutron powder and X-ray diffraction analysis have been performed to study the structural changes of the electrodes during charge and discharge. The nickel electrodes are measured at various states of charge from 0 to 100% and iron electrodes 0 to 90%. Preliminary experiments for the in-situ neutron diffraction test setup are performed. Different thicknesses of quartz glass, several sizes of nickel foam current collectors are tested for the amount of their background noise. In the nickel electrode are next to the carbon, 3 phases present. In the comparison with Morishita et al. significant differences are found. The transition towards β-NiOOH and subsequently γ-NiOOH occurs faster. Already at 50% of SOC the weight fraction of β-NiOOH is 58 wt% and at 100% of SOC the γ-NiOOH is 57 wt%. The c-parameter of γ-NiOOH is in agreement with Morishita et al. with a lattice distance of 20.8 Å. Morishita et al. did not specify how they determined the state of charge, so maybe they calculated the SOC in a different way. In the iron electrode three phases are identified, namely iron (Fe), goethite (FeOOH) and magnetite (Fe3O4). This is a strange result, because where Fe(OH)2 is expected, FeOOH is found. Probably discharged too far, moving the reaction into the second discharge plateau. The weight fraction of Fe increases and FeOOH decreases with increasing state of charge. The hydrogen content is decreasing with increasing SOC proportional to the background function for both the nickel and iron electrode.