Novel amphoteric ion exchange membranes by blending sulfonated poly(ether ether ketone) with ammonium polyphosphate for vanadium redox flow battery applications

Abstract

A novel amphoteric ion exchange membrane for vanadium redox flow battery (VRFB) was explored by blending sulfonated poly(ether ether ketone) (SPEEK) and ammonium polyphosphate (APP). The high-stability flame retardant of crosslinked APP with a large number of NH 4 + groups was first introduced into SPEEK membrane. It was observed that the addition of APP with special structure could achieve a good balance between proton conductivity and vanadium ions permeability. The abundant NH 4 + in APP could block the penetration of vanadium ions by Donnan/Manning exclusion effect and ionic crossing networks due to the ionic bonds between cation and anion groups, and specially a small amount of APP within 5% could remarkably improve the proton conductivity of pristine SPEEK membrane might be ascribed to the unique fast proton transport channels formed by hydrogen bond networks and particular micro-phase separation as a result of interaction between SPEEK and APP. When 5% APP was blended, the SPEEK/ APP-5% (S/APP-5%) amphoteric membrane showed a higher selectivity of 20.87 × 10 4 S min/cm 3 (with a good proton conductivity of 0.075 S/cm and a lower VO 2+ permeability of 3.45 × 10 −7 cm 2 / min) and presented better thermal and chemical stability compared to Nafion115 and SPEEK membranes. The VRFB single cell assembled with S/APP-5% amphoteric membrane exhibited more excellent performance than that of Nafion115 and pristine SPEEK membranes, which revealed a higher coulombic efficiency of 96.3%-98.3%, comparable voltage efficiency of 88.4%-78.7% and higher energy efficiency of 85.1%-77.4% from 40 to 80 mA/cm 2 , respectively, and showed relatively good stability of the efficiency up to 50 cycles at 60 mA/cm 2. The results demonstrated that the designed S/APP amphiprotic membrane of outstanding selectivity, high battery efficiency, and good durability is a prospected VRFB separator.

Deciphering the role of 2D graphene oxide nanofillers in polymer membranes for vanadium redox flow batteries

“…Amphoteric and zwitterion polymer membranes have attracted considerable attention in recent periods because of their effectiveness in enhancing the membrane properties by simultaneous activities of cationic and anionic sites in the membrane. 227–229 Apart from the polymers, new strategies were approached to introduce the amphoteric and zwitterionic functional properties of the inorganic additives to enhance the proton conductivity and decrease the vanadium ion permeability. The amphoteric and zwitterionic nature of GO was developed as GO was grafted with 3-(1-vinyl-3-imidazole) propane sulfonate (GO-VIPS), 226 ethylenediamine (EDA) propane sultone, 230 zwitterion polymer-functionalized GO 231 and 2,2′-benzidinedisulfonic acid functionalized amphoteric-GO nanosheets.…”

Sulfonated poly(ether ether ketone): efficient ion-exchange polymer electrolytes for fuel cell applications–a versatile review

“…The research group of Chen et al 2021 synthesized various modified SPEEK for the highperformance batteries. [28][29][30][31] It is a semi-crystalline polymer, amorphous in nature, and shows high thermal and chemical stabilities due to the presence of aromatic rings. [32][33][34] It can be formed by post-sulfonation of commercial PEEK or presulfonation by polymerization of various monomers in the synthesis method of (i) Friedel-craft acylation (ii) displacement reaction (iii) nickel-catalyzed coupling polymerization and (iv) ring-opening polymerisation involving monomers with sulfonic acid groups.…”

An overview on the progress and development of modified sulfonated polyether ether ketone membranes for vanadium redox flow battery applications

“…SPEEK was mixed with ammonium polyphosphate (APP) to form an amphoteric ion exchange membrane applied for the first time in VRFB. 70 Adding APP that contains a large number of NH4 + groups could block the penetration of vanadium ions by Donnan/Manning exclusion effect. A small amount of APP could remarkably accelerate the proton transport probably because of the formation of special fast proton transfer channels due to hydrogen bond networks and particular micro-phase separation between SPEEK and APP according to the vehicular transport and Grotthuss mechanism.…”