Anion Exchange Membranes Incorporating Multi N-Spirocyclic Quaternary Ammonium Cations via Ultraviolet-Initiated Polymerization for Zinc Slurry-Air Flow Batteries

Abstract

Four anion exchange membranes (AEMs) incorporating multi N-spirocyclic quaternary ammoniums via an ultraviolet (UV)-curing method were prepared and tested as separators in zinc (Zn) slurry-air flow batteries (referred to here as ZSAFBs), an environmentally friendly, high specific energy, and low cost energy storage device. The multi N-spirocyclic cations chain was grafted onto the PPO backbone via a hexyl spacer and its chain length, and the thus membrane ion exchange capacity was tuned by varying the molar ratio between the hexyl diallyl ammonium grafted on PPO and the diallyl piperidinium monomer. This rationally designed 3D polymer results in a membrane with a well-developed phase separation morphology, as confirmed by atomic force microscopy, with a high hydroxide ion conductivity and low zincate ion diffusion coefficient, i.e., the PO-6CH2-3x membrane exhibited 19 mS/cm and 2.3 × 10–12 m2/s at 20 °C, respectively. The membranes exhibited great alkaline stability, with PPO-6CH2-3x showing less than 8% drop in ionic conductivity after 2 weeks of accelerated degradation test (1 M KOH, 60 °C). The ZSAFB cell assembled with the PPO-6CH2-3x membrane exhibited an excellent maximum power density (153 mW/cm2), surpassing those of the reported values, making it a very promising membrane material for rechargeable ZSAFBs.

Anion Exchange Membranes Based on Styrene–Ethylene/Butene–Styrene Consist of Two Grafting Forms: N Heterocyclic Cations with Alkyl Intervals and Flexible Long Hydrophobic Side Chains

“…The membrane was immersed in 2 M NaOH solution for 1400 h and the change of ionic conductivity of the membrane was recorded at different times to judge the alkali resistance of the membrane, and the results are shown in Figure a. It was found that the ionic conductivity of the SEBS-C16D60-DMHP-40% membrane decreased by only 10.29% after soaking for 1400 h. At the same time, we compared the alkaline resistance of the AEM in this work with the data of previous work (Figure c) and found that the alkaline resistance of the SEBS-C16D60-DMHP-40% membrane was superior to the results that are reported in most literature. ,− ,,,,, This is because the heteroatom-free structure of SEBS helps improve the alkali resistance of the membrane, and the introduction of N heteroalicyclic cations with larger steric hindrance can effectively reduce the attack of OH – ions. , Therefore, in general, the SEBS-C16D60-DMHP-40% membrane has better alkali resistance.…”

“…9,[11][12][13]16,22,30,32,50 This is because the heteroatomfree structure of SEBS helps improve the alkali resistance of the membrane, and the introduction of N heteroalicyclic cations with larger steric hindrance can effectively reduce the attack of OH − ions. 51,52 Therefore, in general, the SEBS-C16D60-DMHP-40% membrane has better alkali resistance.…”

Zinc–Air Flow Batteries at the Nexus of Materials Innovation and Reaction Engineering

“…To address this issue, the same group further modified the ionomer by attaching methyldiallylammonium groups to the PPO backbone via a C 6 alkyl chain. 111 Such a modification enables multication side chains and facilitates phase separation, both of which contribute to enhanced OH − conductivity. As a result, the maximum power density of ZAFBs reached 153 mW cm −2 , surpassing those of the reported values for ZAFBs with anion exchange membranes.…”

“…This result was obtained, however, at the expense of an ∼27% decrease in the peak power density (66 vs 90 mW cm –2 ) due to the lowered OH – conductivity. To address this issue, the same group further modified the ionomer by attaching methyldiallylammonium groups to the PPO backbone via a C 6 alkyl chain . Such a modification enables multication side chains and facilitates phase separation, both of which contribute to enhanced OH – conductivity.…”

Modified Membranes for Redox Flow Batteries—A Review

“…One of the main challenges in Zn-based FBs is the crossover of active species, mainly zincate ions from the cathode to the anode side, resulting in capacity fade [ 72 , 73 , 74 ]. Mainly, dense AEM [ 75 ] and modified porous membranes [ 18 , 19 ] have been employed to address this issue. The latter strategy, which falls under the scope of the current review work, is discussed below.…”