Reversible Redox Chemistry in Pyrrolidinium‐Based TEMPO Radical and Extended Viologen for High‐Voltage and Long‐Life Aqueous Redox Flow Batteries. Issue 13 (11th February 2022)

• Record Type: Journal Article
• Authors: Pan, Mingguang; Gao, Liuzhou; Liang, Junchuan; Zhang, Pengbo; Lu, Shuyu; Lu, Yan; Ma, Jing; Jin, Zhong
• Is Part Of: Advanced energy materials. Volume 12:Issue 13(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-02-11
• Subjects: AORFBs -- high‐voltage -- organic radicals -- pH‐neutral -- pyrrolidinium, redox‐active materials; Energy harvesting -- Materials -- Periodicals; Energy conversion -- Materials -- Periodicals; Energy storage -- Materials -- Periodicals; Photovoltaics -- Periodicals; Fuel cells -- Periodicals; Thermoelectric materials -- Periodicals; 621.31
• DOI: 10.1002/aenm.202103478
• Languages: English
• ISSNs: 1614-6832

Abstract

Abstract: Aqueous organic redox flow batteries (AORFBs) are regarded as a promising candidate for grid‐scale, low‐cost and sustainable energy storage. However, their performance is restricted by low aqueous solubility and the narrow potential gap of the organic redox‐active species. Herein, a highly‐soluble organic redox pair based on pyrrolidinium cation functionalized TEMPO and extended viologen, namely Pyr‐TEMPO and [PyrPV]Cl4, which exhibits high cell voltage (1.57 V) and long cycling life (over 1000 cycles) in AORFBs is reported. The intrinsic hydrophilic nature of the pyrrolidinium group enables high aqueous solubilities (over 3.35 m for Pyr‐TEMPO and 1.13 m for [PyrPV]Cl4 ). Furthermore, the interaction of nitroxyl radicals with water is observed, which may be helpful to prevent collision‐induced side reactions or structure decomposition. Notably, the assembled AORFBs realize a high energy density of 16.8 Wh L ‐1 and a peak power density of 317 mW cm ‐2 . The evidence is provided to clarify the capacity degradation mechanism of TEMPO/viologen AORFB systems by a series of comprehensive characterizations. Furthermore, the reversible consumption and re‐generation of the nitroxyl radicals upon charging and discharging are well understood. This work presents effective electrochemical and spectroscopic approaches to clarify the redox chemistry and capacity degradation mechanism of radical incorporating AORFB systems. Abstract : A redox pair of pyrrolidinium functionalized TEMPO radical and extended viologen, namely Pyr‐TEMPO and [PyrPV]Cl4, exhibits ultrahigh cell voltage (1.57 V) and prolonged cycling life (over 1000 cycles) in aqueous organic redox flow batteries. The reversible redox chemistry and capacity degradation mechanism are clarified by a series of electrochemical and spectroscopic analyses.