The increasing penetration of intermittent energy sources into electricity grids worldwide necessitates deployment of large-scale energy storage facilities to ensure that the balance between energy supply and demand can be managed over a range of time scales. Reversible, high-temperature solid oxide electrochemical reactors with oxide ion-conducting electrolyte, such as yttria-stabilized zirconia (YSZ), can convert electrical energy to chemical energy, and vice versa, with roundtrip efficiencies of ca. 70 %,[1] depending on current densities, for splitting of CO2 and H2O to CO and H2, respectively, and oxygen. Electrolysis at high current densities over long times necessary for inter-seasonal energy storage results in severe microstructural degradation at the oxygen electrode, lanthanum strontium manganite (LSM)| YSZ | pore interface, the so called triple phase boundary (TPB). This is due to delamination, as a result of pressures associated with O2 accumulation in non-percolating voids.[2] Therefore, greater control over microstructure could eliminate these non-percolating voids, decreasing degradation rates. We are investigating inkjet printing to fabricate oxygen-electrode architectures with exquisitely controlled microstructures, in order to minimise the probability of non-percolating pores. The first step was formulation of a printable YSZ ink that was printed to form the sintered scaffold structures, shown in Figure 1. A printable LSM ink was formulated, printed into the pillar-scaffold structure and subsequently heat-treated to form the composite electrode, comprised of a close-packed cylinder array (Figure 2a). Electrochemical performance data of the resulting cell in electrolyser mode will be presented, and compared with model predictions (Figure 2b).