Stability of TMA-TEMPO-based aqueous electrolytes for redox-flow batteries

Structural alterations on the TEMPO scaffold and their impact on the performance as active materials for redox flow batteries

“…1 Thus, we developed a new a Laboratory of Organic and Macromolecular Chemistry (IOMC), battery cycling protocol to investigate the influence of temperature and dwell time at high SOCs on the lifetime of the active material. 27 In this work, we study six TEMPO derivatives with five of them being synthesised for the first time. The molecules are then compared with N,N,N-2,2,6,6-heptamethylpiperidinyloxy-4-ammonium chloride (TMA-TEMPO), the current forerunner, regarding their suitability as new catholyte materials for ORFBs and to elucidate a structure-stability relationship.…”

Oxidation of N,N,N,2,2,6,6‐Heptamethyl‐piperidine‐4‐ammonium Chloride to Water‐Soluble N‐Oxyl Radicals: A Comparative Study

“…[1,2] Mainly in the field of energy storage, TEMPO was in the research focus as redox-active group in crosslinked polymeric active materials for solid-state batteries or as soluble organic and polymeric energy storage materials in aqueous redox flow batteries. [2][3][4][5][6] One of the best known representatives for water-soluble TEMPO molecules is the N,N,N-2,2,6,6-heptamethylpiperidinyl oxy-4ammonium chloride (TMA-TEMPO). [3] This molecule has been known since the 1970s, where it was presented by Rauckmann et al.…”

“…2,2,6,6‐Tetramethylpiperidinyl‐4‐oxyl (TEMPO) radicals have been known for more than 60 years and gained high interest of researchers in a variety of different fields, such as polymer chemistry, medicine, energy storage and catalysis [1,2] . Mainly in the field of energy storage, TEMPO was in the research focus as redox‐active group in crosslinked polymeric active materials for solid‐state batteries or as soluble organic and polymeric energy storage materials in aqueous redox flow batteries [2–6] . One of the best known representatives for water‐soluble TEMPO molecules is the N,N,N ‐2,2,6,6‐heptamethylpiperidinyl oxy‐4‐ammonium chloride (TMA‐TEMPO) [3] .…”

“…[3] Since then, TMA-TEMPO has been utilized as a standard molecule for RFB-related investigations of novel materials and advanced battery characterization techniques as well as for spin labeling. [5,6,10] Many TEMPO derivatives are commercially available; however, the water-soluble TMA-TEMPO cannot be purchased readily but can be synthesized conveniently over three steps as depicted in Scheme 1. The most straightforward reaction pathway starts with the commercially available triacetonamine (1), which is transformed into the dimethylamine (2) carrying a piperidine ring via reductive amination.…”

“…firstly showed its capability as catholyte material in combination with dimethyl viologen as anolyte in an aqueous redox flow battery (RFB) in 2016 [3] . Since then, TMA‐TEMPO has been utilized as a standard molecule for RFB‐related investigations of novel materials and advanced battery characterization techniques as well as for spin labeling [5,6,10] . Many TEMPO derivatives are commercially available; however, the water‐soluble TMA‐TEMPO cannot be purchased readily but can be synthesized conveniently over three steps as depicted in Scheme 1.…”