Aerosol Deposition of Thin-Film Single- and Bi-layered Solid Electrolytes for Intermediate Temperature Planar Solid Oxide Fuel Cells

Abstract

One of the main limiting factors determining an increase in the specific power and efficiency of solid oxide fuel cells (SOFCs) is the development of deposition technique for thin-film gas-tight electrolytes. Hence, the development of inexpensive and scalable technologies to form thin-film electrolytes is the key direction of SOFC improvement. Despite existence of well-developed techniques, such as chemical vapor/solution deposition (CVD/CSD), electrochemical deposition (ED), thermal spray (TS), physical vapor deposition (PVD), all of them have a trend in rising deposition temperatures or establishing high vacuum that causes an increase in cost. The aerosol deposition (AD) also known as vacuum kinetic spraying (VKS) is a technique for deposition of thin and thick, gas-tight and porous layers. The deposition occurs due to the impact of high-energy particles to substrate and their consequent fragmentation and consolidation, this phenomenon is called room temperature impact consolidation (RTIC). The AD method is distinguished by the ability to lower the formation temperatures of a gas-tight electrolyte layer down to room temperatures by using a high-energy aerosol jet under conditions of low vacuum (1 – 1000 Pa) and room temperature. In addition, the method is characterized by low equipment cost and easy scaling. The possibility to deposit gas-tight films and films with controlled porosity in a wild range of thickness makes it possible to create all functional SOFCs layers without intermediate sintering steps. In the present work, the aerosol deposition technique was used to deposit thin-film electrolytes for anode-supported SOFCs. Two types of anode-supported SOFCs were manufactured. Type-1: thin-film electrolyte with the composition 8 mol.% yttria-stabilized zirconia (8YSZ) deposited on a bilayered anode substrate (current-collecting and functional sublayers) using the AD method followed by the screen-printing of a composite cathode with the composition of (La0.8Sr0.2)0.95MnO3-δ (LSM) and zirconia co-stabilized with 10 mol.% of scandia and 1 mol.% of yttria (10Sc1YSZ). Type-2: bilayered thin electrolyte made of 8YSZ and 10 mol% gadolinia doped ceria (GDC) protective layer deposited on a bilayered anode substrate using the AD method, followed by the screen printing of an active cathode with the composition of (La0.80Sr0.20)0.95CoO3–δ (LSC). The high quality of electrolyte layers of both types of SOFCs was confirmed by scanning electron microscopy, as well as electrochemical measurements, including the measurements of current-voltage characteristics and impedance spectroscopy. At 800 °C the anode-supported cells with humidified hydrogen as a fuel, and air as an oxidant demonstrated the open-circuit voltage of more than 1.04 V for both types of SOFCs, as well as specific power of more than 420 mW/cm2 and 780 mW/cm2 for type-1 and type-2 of SOFCs, respectively. Based on the studies carried out, further steps were determined to improve the electrochemical parameters of the cells, as well as to scale up to deposition on substrates with an area of 100x100 mm2.This work was carried out with financial support from the Russian Scientific Foundation, grant no. 17-79-30071. Figure 1