Pendent Persubstituted Imidazolium and a Polyimidazolium Cross-Linked Polymer as Robust Alkaline Anion Exchange Membranes for Solid-State Zn–Air Batteries

Abstract

Alkaline anion exchange membranes (AEMs) were developed from a series of persubstituted imidazolium cations with varying alkyl chains (Im-nC, nC = (CH2) n−1CH3; n = 4, 12, and 16) tethered on poly­(vinylbenzyl chloride-co-acrylonitrile) (PVC-co-AN) to prepare a comb-shaped polymer membrane (M1-nC) and a cross-linked polymer membrane from polyimidazolium cations and PVC-co-AN (M3). The PVC-co-AN polymer backbone shows high stability after curing, and the water uptake and swelling ratio are controlled by varying the alkyl chain length in M1-nC even with temperature variation. Results show that M1-16C retains the highest ion exchange capacity (IEC) of 95% among the M1-nC series of membranes after exposure to 1 M KOH solution at 80 °C for 30 days. However, the longer alkyl chains hindered the interconnected ion channels limiting the hydrophobic/hydrophilic phase separation and the hydroxide ion conductivity. Meanwhile, M3 exhibits a distinct microphase-separated morphology and a high ionic conductivity of 54.5 mS/cm for a 2.02 IEC with high stability to retain an IEC of 97% after storage in 1 M KOH solution at 80 °C for 30 days. In addition, all the AEMs exhibit high oxidation stability and retain >96% weight after immersion into 4 ppm Fenton’s reagent at 80 °C. Moreover, the flexible solid-state zinc–air batteries comprising an M3 membrane displayed a peak power density of 165 mW cm–2 and superior cycling stability (30 h at 10 mA cm–2) demonstrating very promising applications in solid-state flexible rechargeable Zn–air batteries.

Poly(acrylic acid)-Based Composite Gel Polymer Electrolytes with High Mechanical Strength and Ionic Conductivity toward Flexible Zinc–Air Batteries with Long Cycling Lifetime

“…Currently, there are two kinds of flexible electrolytes suitable for FZABs, namely the alkaline anion exchange membrane (AAEM) and the gel polymer electrolyte (GPE). , The AAEM consists of a fixed cation tied to the polymer membrane backbone and a movable hydroxide (OH – ) anion. The appropriate thickness of the polymer backbone ensures the flexibility of the electrolyte, while OH – ions guarantee the reliable operation of the battery. , However, the high cost, complex preparation procedures of the AAEM, and slow reaction kinetics present in the battery when using AAEM limit AAEM’s practical application in FZABs . In contrast, the GPE has aroused great interest attributed to its relatively low cost, simple synthesis steps, and fast reaction kinetics present in the battery when using the GPE .…”

“…The appropriate thickness of the polymer backbone ensures the flexibility of the electrolyte, while OH − ions guarantee the reliable operation of the battery. 10,11 However, the high cost, complex preparation procedures of the AAEM, and slow reaction kinetics present in the battery when using AAEM limit AAEM's practical application in FZABs. 12 In contrast, the GPE has aroused great interest attributed to its relatively low cost, simple synthesis steps, and fast reaction kinetics present in the battery when using the GPE.…”

Tuning the Hydrophobic Component in Reinforced Poly(arylimidazolium)-Based Anion Exchange Membranes for Alkaline Fuel Cells

“…The E a values were 8.0, 14.8, 15.7, and 15.8 kJ mol –1 for the QPAF-MEIm-PE, QQP-MEIm-PE, QBAF-MEIm-PE, and QPP3-MEIm-PE, respectively, which were comparable or somewhat higher than that of the other reinforced imidazolium-based AEMs (10.8–11.8 kJ mol –1 ) due to the suppressed water absorption of the former membranes; the water uptake of the reinforced MEIm-PE AEMs ranged from 5 to 95% compared to 60–110% of the other reinforced imidazolium-based AEMs. The E a values of the reinforced MEIm-PE AEMs were within those of the unreinforced, self-standing AEMs containing similar imidazolium groups (6.2–23.6 kJ mol –1 ). − …”

Poly(alkyl-biphenyl pyridinium) anion exchange membranes with a hydrophobic side chain for mono-/divalent anion separation

“…11,12 As polymer backbones also greatly affect the morphology and characteristics of AEMs, numerous studies have focused on novel polymer designs. 13,14 Polymer chains with twisted structures, 15 fluorinated block polymers, 16 local densely functionalized sites on polymer backbones, 17 cross-linked polymers, 18 and superacid-catalyzed Friedel-Crafts polymerization to integrate aromatic polymers significantly raise the alkaline stability of AEMs. 19 Despite all these efforts, superacid-catalyzed step-growth polymerization of aromatic fragments has emerged as a prosperous procedure to obtain a great variety of high-performance polymers with diverse structures.…”