N-Sulfonated Poly(arylene-oxindole) for Vanadium Redox Flow Battery Applications

Abstract

We describe the synthesis of N-sulfonated poly(arylene-oxindole) by metal-free superacid, denoted IDB, IBP, and IFP by polycondensation of isatin with 1,4-diphenoxybenzene, biphenyl, and fluorene, monomer, respectively. All three polymers provide flexible transparent films with high decomposition temperatures (400 to 500 °C) as well as good mechanical and oxidative stability. The physiochemical and electrochemical characteristics of the IDB membrane were better, in comparison to IBP and IFP. The presence of an ether linkage in IDB facilitates the formation of a highly negative charge amide ion, resulting in a high degree of N-sulfonation. To evaluate performance in VRFB, relevant physical properties and stability in a highly oxidative environment (2.1 M H2SO4 and 1.6 M VO2 +) were evaluated. In a single cell VRFB test, the peak power density for IDB, IBP, and IFP was 275 mW cm–2, 240 mW cm–2, and 225 mW cm–2 respectively, at 300 mA cm–2 current density. The IDB membrane showed 97% Coulombic, 68% energy, and 66% voltage efficiencies at 100 mA cm–2 over 200 charge/discharge cycles. In comparison to Nafion 117 in identical experimental settings, the OCV studies validated the low rate of self-discharge, showing the IDB membrane is better suited for VRFB applications.

An aqueous polysulfide redox flow battery with a semi-fluorinated cation exchange membrane

“…The obtained burette reading was placed in eqn (3) to calculate IEC. 47 where M dry represents the dry weight of the membrane, and C NaOH and V NaOH are the concentration and volume of NaOH consumed during the titration.…”

“…The cross-over of polysulfide and iron species through the membrane was evaluated in a twocompartment cell as reported in our previous studies. 47,48 The diffusion coefficient (k) of polysulfide and ferricyanide across the membrane was calculated to be 4.57 Â 10 À11 and 3.05 Â 10 À12 dm 2 s À1 , respectively. Extremely low diffusion of ferricyanide across the membrane can be explained based on the Donnan exclusion principle.…”

A poly(2-ethylaniline) blend membrane for vanadium redox flow batteries

“…Characteristically, CE increased while VE and EE decreased as the current density increased from 20 to 100 mA cm −2 for all the membranes. As current density resulting less time was required for the cell to charge and dis- RSC Applied Polymers Paper charge, 53 resulting less vanadium ion crossover and hence high coulombic efficiency. In contrast, VE decreased with increasing current density due to the increasing internal resistance in the system and ohmic polarization.…”

Beyond conventional batteries: a review on semi-solid and redox targeting flow batteries-LiFePO4 as a case study

“…Aer the invention of the rst RFB (iron-chromium RFB) by Thallet at NASA in 1974, different RFBs were developed based on metallic active species as catholyte and anolyte. Among existing metal based RFBs, iron-titanium, 73 all vanadium, [74][75][76][77][78][79][80] iron-vanadium, 68,[81][82][83] vanadium-bromine, 84,85 vanadiumcerium, 86-89 etc. have been developed.…”