•Sulfonated poly(phthalazinone ether ketone)s (SPPEK-P) membranes were prepared.•SPPEK-P membranes exhibited very low vanadium ions permeability.•SPPEK-P membranes exhibited good stability and high VRFB cell efficiency.•SPPEK-P membrane showed stable cell performance over 100 charge-discharge cycles.A series of novel sulfonated poly(phthalazinone ether ketone)s containing pendant phenyl moieties (SPPEK-Ps) are synthesized and thoroughly characterized. The chemical structures of the polymers are confirmed by 1H NMR and FTIR analysis. The physicochemical properties and single cell performance of SPPEK-P membranes are systematically evaluated, revealing that the membranes are thermally, chemically and mechanically stable. The area resistances of SPPEK-P-90 and SPPEK-P-100 are 0.75 Ω cm2 and 0.34 Ω cm2, respectively. SPPEK-P membranes are impermeable to the bulky hydrated VO2+ ion and exhibited low V3+ ion permeability (SPPEK-P-90, 2.53 × 10−5 cm min−1) (Nafion 115 membrane: 9.0 × 10−4 cm min−1). Tests of SPPEK-P-90 in vanadium redox flow batteries (VRFBs) demonstrate a comparable columbic efficiency (CE) and energy efficiency (EE) to that of Nafion 115, where the CE is 98% and the EE is 83% at 60 mA cm−2. Moreover, the SPPEK-P-90 membrane exhibits stable performance in cell over 100 charge-discharge cycles (∼450 h).Download high-res image (216KB)Download full-size image

•New adamantane-containing poly(aryl ether ketone) membranes are prepared for VRFB.•QADMPEK membranes show significantly low vanadium ions permeability.•High battery efficiency of VRFB with QADMPEK membranes are obtained.•QADMPEK membranes show high stability in VRFB.Quaternized adamantane-containing poly(aryl ether ketone) anion exchange membranes (QADMPEK) are prepared and investigated for vanadium redox flow batteries (VRFB) application. The bulky, rigid and highly hydrophobic adamantane segment incorporated into the backbone of membrane material makes QADMPEK membranes have low water uptake and swelling ratio, and the as-prepared membranes display significantly lower permeability of vanadium ions than that of Nafion117 membrane. As a consequence, the VRFB cell with QADMPEK-3 membrane shows higher coulombic efficiency (99.4%) and energy efficiency (84.0%) than those for Nafion117 membrane (95.2% and 80.5%, respectively) at the current density of 80 mA cm−2. Furthermore, at a much higher current density of 140 mA cm−2, QADMPEK membrane still exhibits better coulombic efficiency and energy efficiency than Nafion117 membrane (coulombic efficiency 99.2% vs 96.5% and energy efficiency 76.0% vs 74.0%). Moreover, QADMPEK membranes show high stability in in-situ VRFB cycle test and ex-situ oxidation stability test. These results indicate that QADMPEK membranes are good candidates for VRFB applications.

A series of sulfonated poly(phthalazinone ether ketone)s containing 3,5-diphenyl phthalazinone moieties (SPPEK-dPs) were prepared by the sulfonation of poly(aryl ether ketone)s containing 3,5-diphenyl phthalazinone moieties (PPEK-dPs) which were synthesized via direct nucleophilic polycondensation from 4-(4-hydroxyphenyl)-2,3-phthalazin-1-ketone (DHPZ), 4-(3,5-diphenyl-4-hydroxyphenyl)-2,3-phthalazin-1-ketone (DHPZ-dP) and 4,4-difluorobenzophenone (DFB). The molecular structures were assessed by FTIR and 1H-NMR spectroscopy. The ion exchange capacity (IEC) of these sulfonated polymers were in the range of 0.99–1.81 mmol g−1. SPPEK-dP proton exchange membranes demonstrated good mechanical properties as well as dimensional, thermal, and oxidative stability. The proton conductivities of SPPEK-dP membranes increased with DHPZ-dP content and temperature. The proton conductivity of SPPEK-dP-55 was 13.18 × 10−2 S cm−1 at 95 °C. Furthermore, the methanol diffusion coefficients of SPPEK-dP membranes were 0.12 × 10−7 cm2 s−1 to 1.09 × 10−7 cm2 s−1 depending on the molar ratio of DHPZ-dP. Remarkably, the selectivity of SPPEK-dP membranes was 5–7 times higher than that of Nafion 117 membranes under the same conditions. All of the above properties indicate that SPPEK-dPs have potential applications in proton exchange membranes for direct methanol fuel cells.

A series of heterocyclic poly(aryl ether ketone)s containing 3,5-dimethyl phthalazinone moieties were synthesized via the copolymerization of 4-(3,5-dimethyl-4-hydroxyphenyl)(2H)-phthalazin-1-one, 4-(4-hydroxyphenyl)(2H)-phthalazin-1-one and 4,4′-difluorobenzophenone. The resulting polymers were brominated with N-bromosuccinimide as the bromination reagent. Brominated poly(phthalazinone ether ketone) (BPPEK) with a degree of substitution in the range of 0.48–0.82 was obtained. Quaternized poly(phthalazinone ether ketone) anion exchange membranes (QBPPEK) were prepared from BPPEK membranes with trimethylamine as the amination reagent. Ion exchange capacity (IEC) values of the QBPPEK membranes were in the range of 0.82–1.53 mmol g−1. Compared with Nafion117 membrane, QBPPEK membranes showed much lower vanadium permeability. Coulombic efficiencies of the vanadium redox flow battery (VRB) with QBPPEK membranes were higher than that with the Nafion117 membrane. The energy efficiency of the VRB increased with an increase in the IEC of the QBPPEK membrane. The energy efficiency of the VRB cell with the QBPPEK membrane having an IEC of 1.53 mmol g−1 was 88%, which was higher than that of the cell with the Nafion117 membrane. During 100 charge–discharge cycles, the QBPPEK anion exchange membrane showed a stable performance.

Poly(phthalazinone ether ketone ketone) anion exchange membranes with pyridinium as anion exchange groups (PyPPEKK) were prepared by reacting chloromethylated poly(phthalazinone ether ketone ketone) membranes with pyridine in solution. The reaction conditions including diluent solvents, pyridine concentration, reaction time and temperature were investigated. Under the optimized reaction condition, PyPPEKK anion exchange membranes with IEC values in the range of 0.96–1.55 mmol g−1 and water uptake in the range of 10.2–16.5% were obtained. The swelling ratio of PyPPEKK membranes in deionized water and VOSO4 solution were in the range of 3.2–10.6% and 2.5–7.8%, respectively. PyPPEKK membranes showed good chemical stability in VO2+ solution. Notably, PyPPEKK membranes had higher coulombic efficiencies of VRB and much lower vanadium permeability compared with Nafion117 membrane. The energy efficiency of VRB with PyPPEKK membrane reached 83.6% at 80 mA cm−2 while the energy efficiency of VRB with Nafion117 membrane was 80.7% at the same charge–discharge current density. Furthermore, PyPPEKK membrane exhibited good performance in the 100-cycle charge–discharge VRB test.

To develop cost-effective membranes with low permeability of vanadium ions for vanadium redox flow battery (VRB) application, an inexpensive precursor membrane material, chloromethylated poly(phthalazinone ether ketone ketone), is first prepared from poly(phthalazinone ether ketone ketone) with nitrobenzene as the solvent, and then reacted with trimethylamine to form quaternized poly(phthalazinone ether ketone ketone) (QAPPEKK) anion exchange membranes. At an ion exchange capacity of 1.56 mmol g−1, the QAPPEKK membrane shows much lower permeability of vanadium ions (0.17 × 10−4 cm min−1 for V3+ and 0.21 × 10−4 cm min−1 for VO2+) than that of Nafion117 membrane (1.34 × 10−4 cm min−1 for V3+ and 1.19 × 10−4 cm min−1 for VO2+), resulting in higher coulombic efficiency (99.4% at 80 mA cm−2). In addition, the energy efficiency of the VRB with QAPPEKK membrane is comparable to that of VRB with Nafion117 membrane. Moreover, the QAPPEKK membrane is stable in VO2+ electrolyte, and exhibits good performance in the 100-cycle charge-discharge test of VRB.Highlights► CMPPEKK was first prepared with nitrobenzene as solvent. ► QAPPEKK membrane showed low vanadium ions permeability. ► QAPPEKK membrane in VRB showed high columbic efficiency. ► QAPPEKK membrane was stable in VO2+ electrolyte. ► QAPPEKK membrane showed stable performance in VRB cycling test.

Chloromethylated poly(phthalazinone ether ketone) (CMPPEK) was prepared from poly(phthalazinone ether ketone), with chloromethyl methyl ether (CME) as the chlromethylating reagent and concentrated sulfuric acid as the solvent. The effects of CME quantity, reaction temperature, and reaction time on degree of chloromethylation (DCM) were investigated. CMPPEK with DCM ranging from 0.73 to 2.32 mmol g−1 were obtained. CMPPEK were characterized with 1H NMR and TGA. CMPPEK membranes were prepared from CMPPEK/N-methyl-2-pyrrolidinone casting solutions. Quaternized poly(phthalazinone ether ketone) (QAPPEK) anion exchange membranes were prepared from CMPPEK membranes with different DCM. The ion exchange capacity (IEC) and water content (Wc) of QAPPEK membranes were studied. QAPPEK membranes exhibited IEC ranging from 0.70 to 2.04 mmol g−1 and Wc ranging from 12.9 to 52.3%. IEC and Wc of QAPPEK increased with an increase in DCM of CMPPEK. The vanadium ion permeability of QAPPEK membranes was much lower than that of Nafion117 membrane. The performance of vanadium redox flow battery (VRB) single cell with QAPPEK membranes was investigated. Compare to VRB cell with Nafion117 membrane, the VRB single cell with QAPPEK membranes exhibited higher columbic efficiency. The results show that QAPPEK membranes could be promising anion exchange membranes for VRB applications.Research highlights▶ Preparation of chloromethylated/quaternized poly(phthalazinone ether ketone) anion exchange membranes. ▶ Quaternized poly(phthalazinone ether ketone) anion exchange membranes show low vanadium ion permeability and high columbic efficiency. ▶ Quaternized poly(phthalazinone ether ketone) membranes could be promising anion exchange membranes for vanadium redox flow battery applications.

•SPPBES was firstly used as the active layer material for composite NF membranes.•The additive LiCl can improve the performance of SPPBES membrane.•The composite membrane has excellent thermal stability and chlorine resistance.Thin composite nanofiltration membranes with improved thermal stability were prepared by coating sulfonated copoly (phthalazinone biphenyl ether sulfone) (SPPBES) on poly (phthalazinone ether sulfone ketone) ultrafiltration support membranes. The effects of polymer concentration, degree of sulfonation of SPPBES, crosslinking agent, curing treatment temperature and curing time on the performance of composite membranes were investigated. The membrane prepared under the optimum condition exhibited a permeate flux of 73 L/m2h and 84% rejection of Na2SO4 at 1.0 MPa and 20 °C. Moreover, these membranes showed good stability against chemical attack and high tolerance to chlorine. When the temperature of feed solution increased from 20 to 90 °C, solution permeate flux increased three-fold while the rejection of the membrane decreased by 2%.

Poly(phthalazinone ether ketone ketone) anion exchange membranes with pyridinium as anion exchange groups (PyPPEKK) were prepared by reacting chloromethylated poly(phthalazinone ether ketone ketone) membranes with pyridine in solution. The reaction conditions including diluent solvents, pyridine concentration, reaction time and temperature were investigated. Under the optimized reaction condition, PyPPEKK anion exchange membranes with IEC values in the range of 0.96–1.55 mmol g−1 and water uptake in the range of 10.2–16.5% were obtained. The swelling ratio of PyPPEKK membranes in deionized water and VOSO4 solution were in the range of 3.2–10.6% and 2.5–7.8%, respectively. PyPPEKK membranes showed good chemical stability in VO2+ solution. Notably, PyPPEKK membranes had higher coulombic efficiencies of VRB and much lower vanadium permeability compared with Nafion117 membrane. The energy efficiency of VRB with PyPPEKK membrane reached 83.6% at 80 mA cm−2 while the energy efficiency of VRB with Nafion117 membrane was 80.7% at the same charge–discharge current density. Furthermore, PyPPEKK membrane exhibited good performance in the 100-cycle charge–discharge VRB test.

A series of heterocyclic poly(aryl ether ketone)s containing 3,5-dimethyl phthalazinone moieties were synthesized via the copolymerization of 4-(3,5-dimethyl-4-hydroxyphenyl)(2H)-phthalazin-1-one, 4-(4-hydroxyphenyl)(2H)-phthalazin-1-one and 4,4′-difluorobenzophenone. The resulting polymers were brominated with N-bromosuccinimide as the bromination reagent. Brominated poly(phthalazinone ether ketone) (BPPEK) with a degree of substitution in the range of 0.48–0.82 was obtained. Quaternized poly(phthalazinone ether ketone) anion exchange membranes (QBPPEK) were prepared from BPPEK membranes with trimethylamine as the amination reagent. Ion exchange capacity (IEC) values of the QBPPEK membranes were in the range of 0.82–1.53 mmol g−1. Compared with Nafion117 membrane, QBPPEK membranes showed much lower vanadium permeability. Coulombic efficiencies of the vanadium redox flow battery (VRB) with QBPPEK membranes were higher than that with the Nafion117 membrane. The energy efficiency of the VRB increased with an increase in the IEC of the QBPPEK membrane. The energy efficiency of the VRB cell with the QBPPEK membrane having an IEC of 1.53 mmol g−1 was 88%, which was higher than that of the cell with the Nafion117 membrane. During 100 charge–discharge cycles, the QBPPEK anion exchange membrane showed a stable performance.