Novel Anion Exchange Membrane Based on Poly(Pentafluorostyrene) Substituted with Mercaptotetrazole Pendant Groups and Its Blend with Polybenzimidazole for Vanadium Redox Flow Battery Applications

Abstract

In order to evaluate the performance of the anion exchange membranes in a vanadium redox flow battery, a novel anion exchange polymer was synthesized via a three step process. Firstly, 1-(2-dimethylaminoethyl)-5-mercaptotetrazole was grafted onto poly(pentafluorostyrene) by nucleophilic F/S exchange. Secondly, the tertiary amino groups were quaternized by using iodomethane to provide anion exchange sites. Finally, the synthesized polymer was blended with polybenzimidazole to be applied in vanadium redox flow battery. The blend membranes exhibited better single cell battery performance in terms of efficiencies, open circuit voltage test and charge-discharge cycling test than that of a Nafion 212 membrane. The battery performance results of synthesized blend membranes suggest that those novel anion exchange membranes are promising candidates for vanadium redox flow batteries.Polymers 2020, 12, 915 2 of 14 and superior chemical stability; however, it has been found that Nafion ® type membranes suffer from high vanadium ion cross-over, resulting in fast capacity fade when used in VRFBs [4,5].In the last decade, interest in using AEMs in various applications, such as alkaline anion exchange membrane fuel cells [6], alkaline anion exchange membrane water electrolysis [7], ionic polymer membrane actuators [8], dye-sensitized solar cells [9], CO 2 pumps [10] and redox flow batteries [11] has strongly increased. In a recent review paper, the number of journal articles published in the field of anion exchange membranes was analyzed using Web of Science (SCI-EXPANDED), showing a steady growth since 2007 [12]. The significant advantage of AEMs when applied in a VRFB is that their positively charged fixed ion groups (commonly quaternary ammonium) exclude positively charged, strongly oxidizing vanadium ions from the membrane interior due to the Donnan exclusion effect, leading to extremely low vanadium ion cross-over [11].Additionally, modified poly(pentafluorostyrene) (PPFSt) was applied in proton exchange membrane fuel cells as sulfonated [13] or phosphonated [14] CEMs, exhibiting outstanding oxidative and thermal stabilities, which were better than those of their non-fluorinated styrene polymer analogs due to the higher bond strengths of the C-F bonds compared to those of C-H bonds [15]. The outstanding stability of PPFSt-based CEMs inspired us to find a route to prepare a PPFSt-based anion exchange polymer with the advantages of AEMs. Introducing spacer units between the polymer backbone and the side chains in an AEM was thought to lead to an enhanced ion-conductivity, which might be facilitated by an improved phase separation between the hydrophobic polymer backbone and the cation-carrying side chains [16]. Tetrazole tethered polymers showed an improved conductivity compared to that of tetramethylammonium-based quaternized poly(phenylene oxide) AEMs, which is thought to be caused by the long-range hydrogen bond network formation by the tetrazole moiety contributing to the ion conductivity [17].In this study, we synthesize...

Performance Enhancement of Vanadium Redox Flow Battery by Treated Carbon Felt Electrodes of Polyacrylonitrile using Atmospheric Pressure Plasma

“…The VRFB system consists of an energy management system (EMS) to control the power in and out, a battery management system (BMS) of two electrolyte tanks with V 2+ /V 3+ and VO 2+ /VO 2 + redox species in sulfuric or other acidic solutions with both negative and positive electrodes, and at least two pumps, as well as a battery stack where the key battery reaction takes place. The electrolyte is pumped into the stack and separated by the ion exchange membrane and fills the reaction area [ 4 , 5 , 6 ]. The electrode in the battery is used to conduct the electrons, provide the charge transfer platform, and make good contact with the electrolyte.…”

Improving proton conductivity of poly(oxyphenylene benzimidazole) membranes with sulfonation and magnetite addition

“…The effect of the crystallinity gave PBIO membranes excellent IEC properties. The IEC value for PBIOsm obtained in the study was slightly higher than that reported in the literature [43][44][45][46][47][48]. In Table 4, the IEC values reported in the literature studies are compared with those obtained for the PBIO membranes synthesized in this study.…”

“…In this study, according to TGA analysis, IEC was calculated for PBIOs and PBIOsm. It is important that the decomposition temperature of the sulfonic acid groups is in the range of 250 °C and 400 °C and that the 3.12 meq/g [46] Poly(pentafluorostyrene) substituted with mercaptotetrazole pendant groups and its blend with polybenzimidazole 19.1 ± 1.64 mS/cm 13.5 ± 0.68 mS/cm [47] High molecular weight polybenzimidazole 0.83 to 1.36 mmol/g [48] Poly (oxyphenylene benzimidazole) membranes with sulfonic group modification and magnetite addition 8 meq/g at 60 °C 8.3 meq/g at 90 °C This study degradation of the PVDF and PBIO hybrid polymer chains is above 400 °C. As a result of the calculation, IEC (TGA) values of 3.78 and 3.51 meq/g were obtained for PBIOs and PBI-Osm membranes.…”

Blended Anion Exchange Membranes for Vanadium Redox Flow Batteries

“…The electrolytes were cyclically pumped into the corresponding half-cell using peristaltic pumps with a flow rate 150 mL/min. The redox flow battery was charged to 1.7 V at a current density of 100 mA/cm, and the open circuit voltage was checked by a battery test system (SP-240, Bio Logic Science Instrument, Seyssinet-Pariset, France) [ 30 ].…”