1. Department of Materials Science, University of Milano-Bicocca, via Cozzi 55, 20125 Milano, Italy
2. National Reference Center for Electrochemical Energy Storage (GISEL), Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali (INSTM), 50121 Firenze, Italy
3. Department of Physics, Chalmers University of Technology, SE-41296 Göteborg, Sweden