To test the electrochemical performance of La2Ni0.75Co0.25O4.08 as a cathode within FIBs, galvanostatic charging and discharging curves were recorded in an all-solid-state battery comprising of La2Ni0.75Co0.25O4.08 II La0.9Ba0.1F2.9 II Pb-PbF2 within the modified stainless-steel Swagelok-type cell at 170 °C as shown in Figure . First, the structural changes induced upon F -intercalation were determined. For this, separate cells were galvanostatically charged to different capacities up to 600 mAh g -1 (which is far beyond the theoretical capacity of the active cathode material, and can thus help to indicate potential and capacity ranges in which side reactions of the carbon-based additive can occur) and analyzed by ex-situ X-ray diffraction measurements of the cathode side of the pellet (see Figure ). Overall, the charging curve can be divided into three different zones as indicated in Figure a. 1) A sharp increase in the voltage from 0.2 V to 0.45 V vs. Pb/PbF2 is observed. Such a sharp increase corresponds well with the initiation of the electrochemical reaction involving different processes like F -ion transport from the anode towards the cathode, i.e., the mass transport along with the accumulation of the charge at the electrolyte/cathode interface. In this region, the capacity contribution taken up is very low (~2 mAh g -1 ).