A π‐Conjugation Extended Viologen as a Two‐Electron Storage Anolyte for Total Organic Aqueous Redox Flow Batteries

Abstract

Extending the conjugation of viologen by ap lanar thiazolo [5,4-d]thiazole (TTz) framework and functionalizing the pyridinium with hydrophilic ammonium groups yielded ah ighly water-soluble p-conjugation extended viologen, 4,4'-(thiazolo [5,4-d] With the advantages of decoupled energy and power, high current and power performance,non-flammable and low cost aqueous supporting electrolytes,aswell as the tunable redox potentials of the organic active materials,a queous organic redox flow batteries (AORFBs) have attracted increasing research and technology development for large scale and dispatchable storage (up to MW/MWh) of the intermittent renewable energy including solar and wind energy.[1] In AORFBs,w ater-soluble organic redox active materials or compounds are applied as electrolyte materials.Inthe charge process,e nergy is stored by the reduction of anolyte and oxidation of catholyte;inthe discharge process,the energy is outputted by the re-oxidation of anolyte and re-reduction of catholyte

Unprecedented Capacity and Stability of Ammonium Ferrocyanide Catholyte in pH Neutral Aqueous Redox Flow Batteries

“…4,5 Thus, the discovery of new redox active electrolyte materials is key to realizing high-performance, low-cost, and benign redox flow batteries to enable future green energy storage. [6][7][8][9][10] Recently there have been increasing efforts in designing and applying redox active organic and organometallic electrolyte materials in aqueous organic/organometallic RFBs (AORFBs) 4,5,[11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] and non-aqueous organic/organometallic RFBs (NAORFBs) [28][29][30][31][32][33][34][35][36][37][38][39][40][41][42] in order to overcome the challenges of traditional AIRFBs. In addition to retaining the general features of ARFBs discussed above, AORFBs have two major technological and economic advantages over AIRFBs for large-scale energy storage: (1) redox active organic/organometallic molecules are synthetically tunable to achieve high (for catholyte) or low (for anolyte) redox potentials, high solubility, and excellent chemical and electrochemical stability, thus high-energy-density, durable RFBs; and (2) redox active organic/organometallic molecules consisting of earth-abundant eleme...…”

“…[11][12][13]16,17,26,27,43 We, Schubert, and others have employed water-soluble viologen (anolyte), ferrocene (catholyte), and TEMPO (catholyte) derivatives to develop high-voltage and stable pH neutral AORFBs. 4,5,14,15,[18][19][20][21][22]25 Thus far, neutral viologen AORFBs have demonstrated the most stable flow battery performance with capacity retention up to 99.99% per cycle for up to 700 cycles, and represent the state of the art for organic redox flow batteries. 4,19,21,25 Many studies have focused on developing organic and organometallic anolyte materials for AORFB applications; 5,11,13,15,17,21,22 however, few studies have been pursued to design low-cost and robust organic and organometallic catholyte materials.…”

“…4,5,14,15,[18][19][20][21][22]25 Thus far, neutral viologen AORFBs have demonstrated the most stable flow battery performance with capacity retention up to 99.99% per cycle for up to 700 cycles, and represent the state of the art for organic redox flow batteries. 4,19,21,25 Many studies have focused on developing organic and organometallic anolyte materials for AORFB applications; 5,11,13,15,17,21,22 however, few studies have been pursued to design low-cost and robust organic and organometallic catholyte materials. 4,18,19,23 In fact, the lack of low cost and robust organic and organometallic catholyte materials has become a bottleneck in developing high-performance AORFBs.…”

Bio-inspired Molecular Redesign of a Multi-redox Catholyte for High-Energy Non-aqueous Organic Redox Flow Batteries

“…[18][19][20][21][22][23][24][25][26][27] For these anolyte ROMs, remarkable performance enhancements in terms of the solubility and multi-electron redox activity have been achieved. 23,26,28,29 Nevertheless, only a limited number of ROMs have been reported as promising catholyte materials (i.e., p-type or oxidation type). 8,30 Research on these p-type (oxidation type) ROMs is still in its infancy, and high-energy organic RFBs can only be realized when anolytes are coupled with appropriate catholytes.…”

Design Rules for Membranes from Polymers of Intrinsic Microporosity for Crossover-free Aqueous Electrochemical Devices

“…Furthermore, the design rules laid out here for linking membrane stability, conductivity, and transport selectivity to prospects for cell performance are also compelling. These experimentally validated guiding principles should accelerate the identification of ion-selective polymer membranes for the broad palette of emerging aqueous cell chemistries, including those based on inorganics, 15,19,20 metal coordination complexes, 14,[21][22][23] organometallics, 24,25 polyoxometalates, [26][27][28] redox-active organic molecules, 13,25,[29][30][31][32][33][34][35][36] and related macromolecular redoxmers. [37][38][39][40][41][42][43][44]…”