Battery and/or supercapacitor?—On the merger of two electrochemical storage system families

Similarities and analogies between materials, structures, operating and construction principles of secondary batteries and supercapacitors and their electrodes are presented, named and reviewed in context. On the material level several materials used both in batteries and supercapacitors are addressed, implications from observations made in one application for the other one are highlighted. On the electrode level a continuous change of architectural details is observed when going from an electrode with high charge storage capability to an electrode supporting high currents is detected, again this overlap provides instructive ideas for both fields. On the cell level combinations of electrodes from both fields yielding hybrid devices are an obvious outcome again with implications for both fields. Ideas and suggestions for further research and development based on a deeper exchange between both families are developed.