Ionic transport properties of nanocrystalline high entropy oxides

• Applicant: Professor Dr.-Ing. Horst Hahn, since 2/2022
• Subject Area: Thermodynamics and Kinetics as well as Properties of Phases and Microstructure of Materials ; Synthesis and Properties of Functional Materials
• Term: from 2019 to 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 424789449

• Final Report Year: 2025

Final Report Abstract

Inorganic ionic conductors are integral in electrochemical devices for energy storge and conversion. A new class of materials, called high entropy materials, has emerged showing unprecedented properties. The configurational entropy of such materials is increased by mixing five or more elements on one lattice site of a single-phase structure. In the case of a positive mixing enthalpy such materials can even exhibit an entropy stabilization of a crystal structure not necessarily accessible for the single element compounds. During the course of this project several high entropy oxides (HEOs) were synthesized to determine the influence of increased configurational entropy and the accompanying high entropy effects (e.g. lattice distortion and cocktail effect) on the ionic conductivity for both cationic, Li+, and anionic, O2-, species. The first material system within this collaborative project between Karlsruhe Institute of Technology (KIT) and Indian Institute of Technology (IIT) Madras was Li-ion conducting transition metal-based R-HEO with a phase-pure rock salt structure. As for oxygen-ion transport along the anionic sublattice the rare earth-based F-HEOs fluorite-type structure was examined. Additionally, new material systems were developed to overcome further challenges, like the garnet-type Li-ion conductors as well as perovskite-type structures for Li- as well as oxygen-ion conductors. Hereby, a large range of materials was thoroughly characterized using state-of-the-art techniques and processing methods to gain in depth understanding of the correlation between composition, structure, defect chemistry and ionic transport in high entropy oxides. The material systems were, finally, integrated in full electrochemical devices as electrolytes as well as electrodes and coating materials. This work initiated several pathways for further developing high entropy materials for fundamental research as well as for industrial application.

Publications

• Embracing disorder in solid-state batteries. Science, 378(6626), 1273-1274.
  Botros, Miriam & Janek, Jürgen
  
• High-entropy spinel-structure oxides as oxygen evolution reaction electrocatalyst. Frontiers in Energy Research, 10.
  Stenzel, David; Zhou, Bei; Okafor, Chukwudalu; Kante, Mohana Veeraju; Lin, Ling; Melinte, Georgian; Bergfeldt, Thomas; Botros, Miriam; Hahn, Horst; Breitung, Ben & Schweidler, Simon
  
• Study of conductivity in Ca-doped high-entropy aluminates (Gd,La,Nd,Pr,Sm)1- xCaxAlO3; KIT Materials day, Karlsruhe, Germany, June 21, 2022, Poster
  M. V. Kante
  
• Synthesis of perovskite-type high-entropy oxides as potential candidates for oxygen evolution. Frontiers in Energy Research, 10.
  Schweidler, Simon; Tang, Yushu; Lin, Ling; Karkera, Guruprakash; Alsawaf, Alaa; Bernadet, Lucile; Breitung, Ben; Hahn, Horst; Fichtner, Maximilian; Tarancón, Albert & Botros, Miriam
  
• A High-Entropy Oxide as High-Activity Electrocatalyst for Water Oxidation. ACS Nano, 17(6), 5329-5339.
  Kante, Mohana V.; Weber, Moritz L.; Ni, Shu; van den Bosch, Iris C. G.; van der Minne, Emma; Heymann, Lisa; Falling, Lorenz J.; Gauquelin, Nicolas; Tsvetanova, Martina; Cunha, Daniel M.; Koster, Gertjan; Gunkel, Felix; Nemšák, Slavomír; Hahn, Horst; Velasco Estrada, Leonardo & Baeumer, Christoph
  
• Effect of citric acid to ethylene glycol (CA:EG) ratio on the particle size and OER catalytic activity of perovskite-type high entropy oxides; CHEAC summer school, Copenhagen, Denmark, 15 – 18 August 2023, Poster
  M. V. Kante
  
• High entropy oxides as electrolyte for solids oxide fuel cells; Microstructural functionality at the nanoscale III, Venice, Italy, June 8-9, 2023, Oral presentation
  M. V. Kante
  
• Influence of doping on the electrochemical performance of compositionally complex garnet-type solid electrolytes, Venice, Italy, June 8-9, 2023, Oral presentation
  A. Alsawaf
  
• Study of oxygen ion conductivity in high entropy oxides; European materials research society, Strasbourg, France, May 29 – June 2, 2023, Oral presentation
  M. V. Kante
  
• Synthesis and characterization of dense, rare-earth based high entropy fluorite thin films. Journal of Alloys and Compounds, 947, 169430.
  Kante, Mohana V.; Hahn, Horst; Bhattacharya, Subramshu S. & Velasco, Leonardo
  
• Synthesis and Processing of High Entropy Materials and their Integration into Lithium Batteries, PhD Thesis Technical University Darmstadt
  Cui, Yanyan
  
• Elucidation of the Transport Properties of Calcium‐Doped High Entropy Rare Earth Aluminates for Solid Oxide Fuel Cell Applications. Small, 20(34).
  Kante, Mohana V.; Nilayam, Ajai R. Lakshmi; Hahn, Horst; Bhattacharya, Subramshu S.; Elm, Matthias T.; Velasco, Leonardo & Botros, Miriam
  
• High-entropy materials for energy and electronic applications. Nature Reviews Materials, 9(4), 266–281.
  Schweidler, Simon; Botros, Miriam; Strauss, Florian; Wang, Qingsong; Ma, Yanjiao; Velasco, Leonardo; Cadilha Marques, Gabriel; Sarkar, Abhishek; Kübel, Christian; Hahn, Horst; Aghassi-Hagmann, Jasmin; Brezesinski, Torsten & Breitung, Ben
  
• Influence of Zr-doping on the structure and transport properties of rare earth high-entropy oxides. Journal of Physics: Energy, 6(3), 035001.
  Kante, Mohana V; Lakshmi Nilayam, Ajai R; Kreka, Kosova; Hahn, Horst; Bhattacharya, Subramshu S; Velasco, Leonardo; Tarancón, Albert; Kübel, Christian; Schweidler, Simon & Botros, Miriam
  
• Photonic Synthesis and Coating of High‐Entropy Oxide on Layered Ni‐Rich Cathode Particles. Small Structures, 5(11).
  Cui, Yanyan; Tang, Yushu; Lin, Jing; Wang, Junbo; Hahn, Horst; Breitung, Ben; Schweidler, Simon; Brezesinski, Torsten & Botros, Miriam
  
• Influence of In‐Doping on the Structure and Electrochemical Performance of Compositionally Complex Garnet‐Type Solid Electrolytes. Small Structures, 6(7).
  Alsawaf, Alaa; Karkera, Guruprakash; Diemant, Thomas; Kante, Monaha Veerraju; Schneider, Yannik; Velasco, Leonardo; Bhattacharya, Subramshu S.; Stainer, Florian; Wilkening, Martin; Clemens, Oliver; Janek, Jürgen; Hahn, Horst & Botros, Miriam
  
• Reducing Critical Raw Material Use in Commercial Solid Oxide Fuel Cells Using Vertically Aligned Thin‐Film Cathodes with Enhanced Long‐Term Stability. ENERGY & ENVIRONMENTAL MATERIALS, 8(4).
  Wells, Matthew P.; Kreka, Kosova; Kante, Mohana V.; Botros, Miriam; Celikbilek, Ozden; Ouweltjes, Jan Pieter; Baiutti, Federico; Fairclough, Simon M.; Ducati, Caterina; Tarancón, Albert & MacManus‐Driscoll, Judith L.