Preparation and interfacial engineering of sputtered electrolytes for thin film oxygen ion batteries†

This study investigates the structural, chemical, and electrochemical properties of yttria-stabilized zirconia (YSZ) thin film electrolytes for thin film oxygen ion batteries (OIB), prepared by reactive DC magnetron sputtering. The films were deposited on various electrode materials, including platinum and mixed ionic electronic conducting (MIEC) perovskite oxides, with and without gadolinia-doped ceria (GDC) buffer layers. Characterization techniques such as scanning electron microscopy, laser ablation inductively coupled plasma mass spectrometry, X-ray fluorescence spectroscopy and X-ray diffractometry were employed to analyze the microstructural and chemical properties of the films. Electrochemical impedance spectroscopy and galvanostatic charge–discharge cycling were used to evaluate the ionic conductivity and interfacial resistance of the YSZ films. The results demonstrate that the YSZ films exhibit a dense, polycrystalline structure with a highly columnar grain morphology and a chemical composition close to the desired stoichiometry. The ionic conductivity of the films is slightly lower than that of single crystal YSZ, with an activation energy of approximately 1.09 eV. The introduction of GDC buffer layers significantly reduces the interfacial resistance of YSZ grown on MIEC perovskite films, thereby lowering the effective electrolyte resistance by up to 75%. Thin film electrolyte OIBs were prepared and operated at 250 °C, and substantiated the performance increase by interfacial engineering, i.e. the introduction of GDC buffer layers.