Multiple charging/discharging cycles of a rechargeable oxide battery – Electrochemistry and post-test analysis

A two-layer rechargeable oxide battery using a stack initially developed for solid oxide cells was operated for 2100 h with more than 1000 charging/discharging cycles. The operation temperature was 800 °C and the applied current density (on the solid oxide cell) was 150 mA cm⁻². During operation, no electrochemical indications for degradation were measured. The voltages achieved during redox cycling were in good agreement with the equilibrium voltages of the envisaged corresponding phases. For the first time, a storage material based on the calcium–iron oxide with the richest iron content was used. Storage utilization was 86%, thereby reaching a capacity of 20.6 Ah per layer. Post-test analysis of the storage revealed mostly expected storage phases and sufficient remaining storage porosity.