Silvère PANISSET – Nanostructured Thin Film Oxygen Electrodes for Solid Oxide Electrochemical Devices: Deposition Optimisation, Characterisation, and Modelling

Jury

Prof. Albert Tarancón, IREC, Barcelone (ESP) - Rapporteur
Dr. Jean-Marc Bassat, ICMBM, CNRS, Bordeaux - Rapporteur
Prof. Alejandro Franco, LRCS, Université de Picardie Jules Verne - Examinateur
Prof. Eirini Sarigiannidou, LMGP, Université Grenoble Alpes - Examinatrice
Dr. Ozden Celikbilek, CEA, Grenoble - Examinatrice
Dr. Mónica Burriel, LMGP, Université Grenoble Alpes - Directrice de thèse
Dr. Alexander Stangl, LMGP, Université Grenoble Alpes - Invité
Dr. Alexander Schmid, TUW, Vienne (AUS) - Invité
 

Abstract

Background. Solid oxide cells (SOCs) are electrochemical devices that efficiently convert fuel gases, such as hydrogen, into electricity and can also operate in reverse mode as electrolysers. These ceramic-based devices consist of a dense electrolyte sandwiched between two porous electrodes. The oxygen electrode, also known as the air electrode, poses a significant challenge due to its sensitivity to operating temperature. Its electrochemical performance increases with temperature but high operating temperatures can lead to electrode degradation, hindering the cell’s efficiency. This thesis explores the potential for miniaturizing SOCs to a thickness of less than 1 µm using all thin film components (oxygen electrode, electrolyte and fuel electrode). This miniaturization has the advantage of enabling operation at lower temperatures (< 500 °C) while reducing the use of a significant amount of critical raw materials. The focus of this work is on developing high-performance oxygen electrodes by optimizing both the nanostructure and the intrinsic properties of the constituent material.
This thesis investigates the optimization of thin film oxygen electrodes (≤ 1000 nm) deposited by Pulsed Injection-Metal Organic Chemical Vapor Deposition (PI-MOCVD) and their subsequent electrochemical characterization. The study focuses on nano-columnar porous thin films of La2NiO4+δ (L2NO4), a mixed ionic-electronic conducting (MIEC) material and promising oxygen electrode for intermediate- to low-temperature Solid Oxide Cells (SOC). A 3D Finite Element Method electrochemical model was developed at the scale of the nano-columnar morphology, to predict the optimal film thickness and microstructure. These numerical insights guided the optimization of L2NO4 thin film deposition. To further enhance the electrode performance, the possibility of partially substituting La with Pr was explored to increase the intrinsic activity of the material. Lanthanum-praseodymium nickelate (LaPrNiO4+δ) thin films were successfully deposited using PI-MOCVD for the first time. Kinetic studies, including Electrical Conductivity Relaxation (ECR) and Electrochemical Impedance Spectroscopy (EIS), were conducted, along with short-term stability tests. Additionally, a novel setup was developed for in situ EIS measurements during PI-MOCVD deposition, providing valuable insights into the optimal thickness (number of pulses deposited) and the electrochemical-morphology relationship during growth. Finally, the potential of L2NO4 as a cathode material for oxygen ion batteries (OIB), a new class of solid-state batteries, was explored. Both half-cell and full-cell configurations were successfully fabricated and tested, demonstrating the feasibility of combining under- and over-stoichiometric MIEC materials as OIB electrodes.