Aqueous 2,2,6,6-Tetramethyl­piperidine‑<i>N</i>‑oxyl Catholytes for a High-Capacity and High Current Density Oxygen-Insensitive Hybrid-Flow Battery

Hybrid-flow batteries are a suitable storage technology for “green” electricity generated by renewable sources such as wind power and solar energy. Redox-active organic compounds have recently been investigated to improve the traditional metal- and halogen-based technologies. Here we report the utilization of a 2,2,6,6-tetramethylpiperidine-<i>N</i>-oxyl (TEMPO) derivative that is in particular designed for application in semiorganic zinc hybrid-flow batteries. The TEMPO derivative is synthesized and electrochemically characterized via cyclic voltammetry and rotating disc electrode measurements. This derivative features a high solubility in aqueous electrolytes; thus, volumetric capacities above 20 Ah L^–1 are achieved. The fabricated hybrid-flow batteries feature over 1100 consecutive charge–discharge cycles at constant capacity retention, and current densities up to 80 mA cm^–2 are applied

TEMPO/Phenazine Combi-Molecule: A Redox-Active Material for Symmetric Aqueous Redox-Flow Batteries

The combination of 2,2,6,6-tetramethylpiperidinyl-<i>N</i>-oxyl and phenazine yields an organic redox-active material for redox-flow battery applications. This combined molecule (combi-molecule) features a redox voltage of 1.2 V and facilitates the utilization of aqueous electrolytes. It was synthesized from cost-efficient starting materials, electrochemically characterized and applied as charge-storage material in a symmetric aqueous redox-flow battery

Investigation of Ice-Templated Porous Electrodes for Application in Organic Batteries

Application and investigation of porous composite electrodes for organic batteries fabricated by an ice-templating method are reported for the first time. The possibility to produce polymer composite electrodes with highly aligned, parallel pores is demonstrated and electrochemical investigations are presented to examine their suitability for application in organic batteries. The performance of such ice-templated porous electrodes is experimentally compared with planar electrodes of similar composition against zinc and lithium counter electrodes, respectively. Fundamental properties limiting the performance of ice-templated porous electrodes are discussed and further means to overcome those limitations are proposed