Addressing the Timing Imbalance between Renewable Energy Generation and Use: Reversible Solid Oxide Cells Based on Rare-Earth Nickelate Oxygen Electrodes

Abstract

Incorporating more renewable energy into our economy will require us to address the timing imbalance between renewable energy generation and its use. Reversible solid oxide cells which have the ability to be dynamically load cycled between electrolysis mode when renewable energy availability is plentiful, and fuel cell mode when stored energy needs to be used, offer a potential solution. In this work, we have fabricated solid oxide cells featuring a neodymium nickelate based oxygen electrode, nickel – yttria stabilized zirconia (YSZ) fuel electrodes, and YSZ solid electrolyte. The cells have been electrochemically characterized in electrolysis and fuel cells mode, as well as in dynamic load cycling mode for a period of five hundred hours. The cells were characterized by both DC polarization and AC impedance spectroscopy methods. Distribution of relaxation times (DRT) analysis of the impedance data reveal significant details about the mechanisms underlying degradation in electrolysis and dynamic cycling modes, and are strongly linked to microstructural changes in the fuel electrode. Further, the dynamic cycling experiments clearly reveal that operating the cells in the dynamic cycling mode mitigates against degradation that occurs when the cells are operated in electrolysis mode. These results strongly suggest that storage systems featuring stacks of such reversible solid oxide cells may offer a path forward to solving the timing imbalance of renewable energy generation and use.