New electrolytes. Relatively few electrolytes are used in conventional Li-ion batteries and supercapacitors, yet once we have created open and accessible electrode structures, electrolytes that contain bulkier ions, such as ionic liquids, can be used effectively. At the same time, the introduction of new energy-storing materials and their designed surface chemistries may require the development of new, compatible electrolytes that operate over a wide voltage window. Efforts should also be directed towards developing new multi-electron redox electrolytes.