1. School of Science and Technology - Chemistry Division University of Camerino Via Madonna delle Carceri, ChIP 62032 Camerino Italy
2. Centre for Cooperative Research on Alternative Energies (CIC energiGUNE) Basque Research and Technology Alliance (BRTA) Alava Technology Park Albert Einstein 48 01510 Vitoria-Gasteiz Spain
3. Departamento de Física de la Materia Condensada Facultad de Ciencia y Tecnología Universidad del País Vasco UPV/EHU, P.O. Box 644 48080 Bilbao Spain
4. TECNALIA Basque Research and Technology Alliance (BRTA) Parque Científico y Tecnológico de Gipuzkoa Mikeletegi Pasealekua 2 20009 Donostia-San Sebastián Spain
5. Present address Helmholtz Institute Ulm (HIU) Helmholtzstrasse 11 89081 Ulm Germany
6. Present address Karlsruhe Institute of Technology (KIT) P.O. Box 3640 76021 Karlsruhe Germany
7. School of Science and Technology - Physics Division University of Camerino Via Madonna delle Carceri 9B 62032 Camerino Italy
8. GISEL-Centro di Riferimento Nazionale per i Sistemi di Accumulo Elettrochimico di Energia, INSTM via G. Giusti 9 50121 Firenze Italy