Multi-electron redox reaction of an organic radical cathode induced by a mesopore carbon network with nitroxide polymers

Abstract

An organic radical based composite cathode comprised of poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate) (PTMA)-Ketjenblack was developed by a simple solvent-less electrode fabrication method. The composite cathode demonstrated a two-electron redox reaction of PTMA that is from an aminoxy anion (n-type) via a radical to an oxoammonium cation (p-type) with the corresponding redox potential at 2.8-3.1 V and 3.5-3.7 V vs. Li/Li(+) when evaluated in lithium half cells. Moreover, the PTMA-Ketjenblack composite electrode exhibits fast electrode reaction kinetics and an enhanced solid electrolyte interface by cyclic voltammetry and electrochemical impedance spectroscopy measurements. These improved electrochemical properties contribute to increased capacity (300 mA h g(-1)), a high rate (50% capacity retention after 100 C rate excursions) and a long cycle life in the cell performance evaluations. Morphological and compositional characterization indicates a unique mesopore network of Ketjenblack with the PTMA matrix, which highly facilitates the interaction between the conductive media and the radical species, resulting in the performance enhancement of the PTMA-Ketjenblack composite cathode.

TEMPO‐Based Catholyte for High‐Energy Density Nonaqueous Redox Flow Batteries

“…The branch‐type polymers of TEMPO, especially poly(2,2,6,6‐tetramethylpiperidinyloxy‐4‐yl methacrylate) (PTMA) in which the methacrylate main chain bears the TEMPO unit in the side chains as the redox active sites, have been studied extensively in lithium batteries and organic radical batteries . The TEMPO‐based polymeric cathode materials show desirable redox potential, high rate capability and good long‐term cycling stability because of the fast, stable and reversible electrochemical redox reactions in nonaqueous electrolytes . In this work, TEMPO demonstrates a high solubility of 5.2 M in the EC/PC/EMC solvent, possibly related to the similarity in polarity with the solvent.…”

Recent developments in organic redox flow batteries: A critical review

“…PTIO is a nitronyl nitroxide molecule that has a solubilility of up to 2.6 mol dm -3 in acetonitrile. It has been used in several applications, including batteries, memory devices and molecular magnets [208][209][210][211]. During the charging process, the PTIO molecule is reduced and oxidized by one electron to form PTIOand PTIO + species in the negative and positive half-cells, respectively.…”

In situ electrochemical-electron spin resonance investigations of multi-electron redox reaction for organic radical cathodes

“…In the reported organic radical batteries, however, the nitroxide polymer based cathode has mostly shown one redox couple on the anodic side (p-type doping) at 3.6 V vs. Li/Li + , which results in a low specific capacity of 100 mAh g -1 [9]. Recently an organic radical composite cathode comprised of PTMA-Ketjenblack (KB), with a two-electron redox reaction, has been developed -4 -in our group [13,14]. It was found that the performance of an organic radical electrode is strongly dependent on the conductive carbon material that plays a significant role in the electron transfer through the radical electrode during the charge-discharge process [1418].…”