High-Capacity Retention Thermally Reinforced Pore-Filled Anion Exchange Membrane for All-Vanadium Flow Batteries

Abstract

In this work, we report a thermally annealed porefilled anion exchange membrane (PFAEM) with excellent mechanical and chemical stability effected by a polypropylene support and impressive electrochemical properties induced by a pore-filled poly (4-vinyl pyridine) matrix followed by its successful demonstration in vanadium redox flow batteries (VRFBs). As expected, a low swelling ratio synergized with Donnan exclusion resulted in low vanadium ion diffusion. The calculated permeability rates for V +3 , VO 2+ , and VO 2 + were 4.80 × 10 −7 , 7.11 × 10 −7 , and 9.4 × 10 −7 dm s −1 , respectively. An exceptionally low dimension change (∼4.5%) was observed in 1.6 M VO 2 + /2 M H 2 SO 4 solution over 15 days. The assembled VRFB exhibited a Coulombic efficiency (CE) of 98.6% and energy efficiency (EE) of 69.2% over 50 charge/discharge cycles at 150 mA cm −2 with a high-capacity retention of 70% and average capacity decay of 0.63% per cycle. The observed peak power density was 340 mW cm −2 . Finally, the autopsy of the membrane after battery performance suggested negligible depreciation in mechanical and electrochemical properties, confirming its potential applicability in VRFBs.

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

“…The wet and dry weights of the membrane were placed in eqn (4) to calculate the water uptake. 48 where M wet and M dry are the wet and dry weights of the membrane, respectively.…”

“…Swelling ratio (SR) was determined from the percentage difference in dimension (length) between the dried and fully hydrated membrane (eqn (5)). 48 where, L wet and L dr y are the wet and dry length of the membrane.…”

“…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

“…In contrast, VE decreased with increasing current density due to the increasing internal resistance in the system and ohmic polarization. [54][55][56] Amongst prepared membranes, EP3 membrane had the best electrochemical properties along with lowest diffusion coefficient for different vanadium ions and this was reflected in its VRFB performance as it showed highest CE (90.5, 92.0, 94. The cycling stability of the best membrane EP3 was further evaluated in an asymmetrical cell and data are presented in Fig.…”

Radiation synthesis of imidazolium ionic liquid grafted PVDF as the anion exchange membrane for vanadium redox flow batteries

“…As the positively charged functional groups in AEMs can repulse the positively charged vanadium species, the AEMs usually achieve very low vanadium ion permeability. Mostly, AEMs were fabricated by incorporating positively charged functional groups (such as quaternary ammonium, 8–10 bipyridine 11,12 and imidazolium 13,14 ) on the polymer matrix (such as poly(arylene ether sulfone), 9 poly(sulfone), 11 poly(vinylidene difluoride), 15 and poly(fluorenyl ether)s 16 ). Among them, imidazolium-based AEMs show superior performance attributed to the unique π-conjugated five-membered ring 14 and positive charge.…”