Metal‐Free Flow Batteries Based on TEMPO

Nitroxide radicals, in particular 2,2,6,6-tetramethylpiperidine- N -oxyl (TEMPO) derivatives, are versatile redox-active compounds that can be used in organic metal-free flow batteries. This chapter introduces TEMPO-based cell chemistries, their features and benefits, as well as the scaling up of the technology toward an industrial product. Besides hybrid systems combining a solid electrode (e.g. zinc, lithium) with a TEMPO solution, full-flow-battery-type cells (e.g. TEMPO and methyl viologen) and an all-TEMPO cell are discussed. In addition, physicochemical properties and synthetic procedures of selected derivatives are presented, and the raw material pipeline of organic compounds is evaluated.