1. Catalonia Institute for Energy Research (IREC), Jardins de Les Dones de Negre 1, 08930 Sant Adrià del Besòs, Barcelona, Spain
2. Department of Energy Conversion and Storage, Functional Oxides Group, Technical University of Denmark, Fysikvej, 310, 233 2800 Kgs. Lyngby, Denmark
3. Department of Materials Chemistry, National Institute of Chemistry, Hajdrihova 19, Ljubljana SI-1000, Slovenia
4. Department of Metallurgical and Materials Engineering, Colorado School of Mines, Golden, CO 80401, USA
5. Department of Materials, Imperial College London, Prince Consort Road, London SW7 2BP, UK
6. Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC), Sor Juana Inés De la Cruz, 3, 28049, Madrid, Spain
7. ICREA, 23 Passeig Lluís Companys, Barcelona 08010, Spain