Utilizing oxygen gas storage in rechargeable oxygen ion batteries

The potentiality of mixed conducting oxides as electrodes in rechargeable oxygen ion batteries is exemplified by impedance measurements and galvanostatic cycling. Porous La0.6Sr0.4CoO3−δ (LSC) thin film electrodes were prepared on yttria-stabilized zirconia electrolytes with a dense ZrO2 blocking layer on top to prevent oxygen exchange with the measurement atmosphere. Half cell measurements performed between 350 and 460°C revealed electrode capacities up to 135mAh/cm3. Measured charge/voltage curves are compared with those reconstructed from chemical capacitance values and with model calculations. Two different storage mechanisms were identified: At low potentials (<0.05V vs. 1bar O2), mainly oxygen vacancies become filled during charging. At higher potentials, however, O2 gas formation (>500bar at potentials >0.1V) in closed pores dominates charge/voltage characteristics, which can be described by calculations based on a real gas model. Moreover, full oxygen ion batteries were investigated, where such a porous LSC electrode served as cathode and a dense La0.9Sr0.1CrO3−δ (LSCr) film was used as anode. Owing to the much lower reducibility of LSCr, a cell voltage of 1.2V was obtained at 460°C with electrode related capacities and energy densities up to 100mAh/cm3 and 53mWh/cm3, respectively.