The research focuses on transport and reactions in mixed-conducting solids and solid electrolytes—but above all on interfaces and their kinetics. In addition to cell concepts based on metal-oxygen reactions (Li/O₂, Na/O₂) and metal-sulfur reactions (Li/S₈, Na/S₈), solid-state batteries are currently the focus of research at Giessen. Analytical studies on the formation of interphases at anodes and cathodes complement this work.

Since 2011, Prof. Janek has also headed the BASF-KIT joint laboratory BELLA at the Institute of Nanotechnology at KIT (Karlsruhe Institute of Technology), where systematic research is conducted on the cell reactions of lithium-ion batteries (LIBs) and material development for improved LIBs.