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Anion exchange membranes (AEMs) are crucial components for advanced energy and environment processes including alkaline fuel cells, redox flow batteries, and industrial effluent treatment; while low anionic conductivity and poor stability remain the major challenges for the widespread implementation of AEMs. Through molecular engineering, comb-shaped AEMs have been proved possessing the capability of delivering both high conductivity and good alkaline stability. However, how to precisely control the side chain topology and how the chain topology would influence the membrane properties need to be further elucidated. We hereby propose a radically novel and readily scalable route towards the controllable synthesis of comb-shaped AMEs and we were able to determine the length of side chains and the number of ionic groups along the side chains. To probe the effect of side chain topology on membrane properties, two types of AEMs of densely grafted short side chains or loosely grafted long side chains with similar ion exchange capacity (IEC, ∼1.7 mmol/g) were synthesized and compared. We found that the comb-shaped AEMs with loosely grafted long chains (LG-LS-DIm), with higher hydroxide conductivity (55 mS cm−1 at 30 °C) and better alkaline stability (∼80 % of IEC retention after soaking in 2 mol L−1 NaOH solution at 60 °C for 25 days), outperform those with densely grafted short chains (HG-SS-DIm) and the benchmark main-chain type AEMs (DIm-PPO), which is also superior to those of conventional linear AEMs with densely functionalized structure.

The grid-scale integration of solar or wind energy that fluctuates over time will compromise the stability of the power grid. All-vanadium redox flow battery (VRFB) is among the most feasible electrochemical energy storage solutions, while the grand challenge is to develop membranes that separate vanadium electrolytes effectively and transport protons rapidly. Here we present highly conductive and vanadium sieving microporous membranes from shape persistent Trӧger's Base polymer. The N-rich and microporous polymer skeleton facilitate H+ transport. In contrast, hydrated vanadium ions are blocked due to size exclusion and coulombic repulsion. This increases the H/V selectivity of the membrane to >6300, lowers the membrane resistance to 0.57 Ω cm2, and raises the battery power density to 710.9 mW cm−2. A round-trip energy efficiency of 80% and a coulombic efficiency of >99% are maintained during long periods of charge/discharge. We believe the results will stimulate new directions for advanced VRFB membranes.

In this study, acidified lithium ion-sieves (HMOs) containing unique inner ionic channels suitable for the transfer of H + are selected as proton-conductive fillers to prepare hybrid membranes for the first time. By using facile distillation-precipitation polymerization process, two types of sulfonated HMOs (SHMOs) are prepared: L-SHMOs, which are modified by sulfonate polyelectrolyte layer, and B-SHMOs, which are sulfonate polyelectrolyte brushes. The results demonstrate that these fillers improve the thermal and mechanical stabilities of chitosan (CS) control membranes. The incorporation of pristine HMOs enhances the water uptakes and proton conduction abilities of hybrid membranes at suitable loading. By comparison, SHMOs-filled membranes possess higher proton conductivities than those of HMO-filled membranes, owing to the additional proton hopping sites of –SO 3 H and acid-base pairs (–SO 3 − ··· + 3 HN–). Moreover, B-SHMO-filled membranes exhibit superior proton conductivities over L -SHMO-filled ones, demonstrating that the polymer brushes on HMOs allow more –SO 3 H groups to form acid-base pairs with CS chains. Particularly, CS/B-SHMO-12 obtains the highest hydrated and anhydrous conductivities of 0.0224 S cm −1 and 10.03 mS cm −1 , enhancing by 91.4% and 98.6% respectively compared with those of CS control membrane under identical conditions. The enhanced proton conductivities offer SHMO-filled membranes elevated cell performances.