Editorial

3 pages, 183 KiB

Open AccessEditorial

by Byungchan Bae and Dukjoon Kim

Membranes 2021, 11(4), 244; https://doi.org/10.3390/membranes11040244 - 29 Mar 2021

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Recently, polymer electrolyte membranes have been used in various electrochemical energy devices and other applications, such as fuel cells, lithium secondary batteries, redox flow batteries, electrodialysis, and membrane capacitive deionization [...] Full article

(This article belongs to the Special Issue Polymer Electrolyte Membranes)

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15 pages, 2587 KiB

Open AccessArticle

Highly Dispersed CeO_x Hybrid Nanoparticles for Perfluorinated Sulfonic Acid Ionomer–Poly(tetrafluoethylene) Reinforced Membranes with Improved Service Life

by Juhee Ahn, Mobina Irshad Ali, Jun Hyun Lim, Yejun Park, In Kee Park, Denis Duchesne, Lisa Chen, Juyoung Kim and Chang Hyun Lee

Membranes 2021, 11(2), 143; https://doi.org/10.3390/membranes11020143 - 18 Feb 2021

Cited by 9 | Viewed by 2490

Abstract

CeO_x hybrid nanoparticles were synthesized and evaluated for use as radical scavengers, in place of commercially available Ce(NO₃)₃ and CeO₂ nanoparticles, to avoid deterioration of the initial electrochemical performance and/or spontaneous aggregation/precipitation issues encountered in polymer electrolyte membranes. [...] Read more.

CeO_x hybrid nanoparticles were synthesized and evaluated for use as radical scavengers, in place of commercially available Ce(NO₃)₃ and CeO₂ nanoparticles, to avoid deterioration of the initial electrochemical performance and/or spontaneous aggregation/precipitation issues encountered in polymer electrolyte membranes. When CeO_x hybrid nanoparticles were used for membrane formation, the resulting membranes exhibited improved proton conductivity (improvement level = 2–15% at 30–90 °C), and thereby electrochemical single cell performance, because the –OH groups on the hybrid nanoparticles acted as proton conductors. In spite of a small amount (i.e., 1.7 mg/cm³) of introduction, their antioxidant effect was sufficient enough to alleviate the radical-induced decomposition of perfluorinated sulfonic acid ionomer under a Fenton test condition and to extend the chemical durability of the resulting reinforced membranes under fuel cell operating conditions. Full article

(This article belongs to the Special Issue Polymer Electrolyte Membranes)

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11 pages, 3409 KiB

Open AccessFeature PaperArticle

Fabrication and Electrolyte Characterizations of Nanofiber Framework-Based Polymer Composite Membranes with Continuous Proton Conductive Pathways

by Takeru Wakiya, Manabu Tanaka and Hiroyoshi Kawakami

Membranes 2021, 11(2), 90; https://doi.org/10.3390/membranes11020090 - 27 Jan 2021

Cited by 9 | Viewed by 2130

Abstract

For future fuel cell operations under high temperature and low- or non-humidified conditions, high-performance polymer electrolyte membranes possessing high proton conductivity at low relative humidity as well as suitable gas barrier property and sufficient membrane stability are strongly desired. In this study, novel [...] Read more.

For future fuel cell operations under high temperature and low- or non-humidified conditions, high-performance polymer electrolyte membranes possessing high proton conductivity at low relative humidity as well as suitable gas barrier property and sufficient membrane stability are strongly desired. In this study, novel nanofiber framework (NfF)-based composite membranes composed of phytic acid (Phy)-doped polybenzimidazole nanofibers (PBINf) and Nafion matrix electrolyte were fabricated through the compression process of the nanofibers. The NfF composite membrane prepared from the pressed Phy-PBINf showed higher proton conductivity and lower activation energy than the conventional NfF composite and recast-Nafion membranes, especially at low relative humidity. It is considered that the compression process increased the nanofiber contents in the composite membrane, resulting in the construction of the continuously formed effective proton conductive pathway consisting of the densely accumulated phosphoric acid and sulfonic acid groups at the interface of the nanofibers and the Nafion matrix. Since the NfF also improved the mechanical strength and gas barrier property through the compression process, the NfF composite polymer electrolyte membranes have the potential to be applied to future fuel cells operated under low- or non-humidified conditions. Full article

(This article belongs to the Special Issue Polymer Electrolyte Membranes)

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12 pages, 3558 KiB

Open AccessArticle

Sulfonyl Imide Acid-Functionalized Membranes via Ni (0) Catalyzed Carbon-Carbon Coupling Polymerization for Fuel Cells

by Sabuj Chandra Sutradhar, Sujin Yoon, Taewook Ryu, Lei Jin, Wei Zhang, Hohyoun Jang and Whangi Kim

Membranes 2021, 11(1), 49; https://doi.org/10.3390/membranes11010049 - 12 Jan 2021

Cited by 3 | Viewed by 2301

Abstract

Polymer membranes, having improved conductivity with enhanced thermal and chemical stability, are desirable for proton exchange membranes fuel cell application. Hence, poly(benzophenone)s membranes (SI-PBP) containing super gas-phase acidic sulfonyl imide groups have been prepared from 2,5-dichlorobenzophenone (DCBP) monomer by C-C coupling polymerization using [...] Read more.

Polymer membranes, having improved conductivity with enhanced thermal and chemical stability, are desirable for proton exchange membranes fuel cell application. Hence, poly(benzophenone)s membranes (SI-PBP) containing super gas-phase acidic sulfonyl imide groups have been prepared from 2,5-dichlorobenzophenone (DCBP) monomer by C-C coupling polymerization using Ni (0) catalyst. The entirely aromatic C-C coupled polymer backbones of the SI-PBP membranes provide exceptional dimensional stability with rational ion exchange capacity (IEC) from 1.85 to 2.30 mS/cm. The as-synthesized SI-PBP membranes provide enhanced proton conductivity (107.07 mS/cm) compared to Nafion 211^® (104.5 mS/cm). The notable thermal and chemical stability of the SI-PBP membranes have been assessed by the thermogravimetric analysis (TGA) and Fenton’s test, respectively. The well distinct surface morphology of the SI-PBP membranes has been confirmed by the atomic force microscopy (AFM). These results of SI-PBP membranes comply with all the requirements for fuel cell applications. Full article

(This article belongs to the Special Issue Polymer Electrolyte Membranes)

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16 pages, 2755 KiB

Open AccessArticle

Multilayered PVDF-HFP Porous Separator via Phase Separation and Selective Solvent Etching for High Voltage Lithium-Ion Batteries

by Van-Tien Bui, Van-Toan Nguyen, Ngoc-Anh Nguyen, Reddicherla Umapathi, Liudmila L. Larina, Jong Heon Kim, Hyun-Suk Kim and Ho-Suk Choi

Membranes 2021, 11(1), 41; https://doi.org/10.3390/membranes11010041 - 07 Jan 2021

Cited by 15 | Viewed by 7708

Abstract

The development of highly porous and thin separator is a great challenge for lithium-ion batteries (LIBs). However, the inevitable safety issues always caused by poor mechanical integrity and internal short circuits of the thin separator must be addressed before this type of separator [...] Read more.

The development of highly porous and thin separator is a great challenge for lithium-ion batteries (LIBs). However, the inevitable safety issues always caused by poor mechanical integrity and internal short circuits of the thin separator must be addressed before this type of separator can be applied to lithium-ion batteries. Here, we developed a novel multilayer poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) membrane with a highly porous and lamellar structure, through a combination of evaporation-induced phase separation and selective solvent etching methods. The developed membrane is capable of a greater amount of electrolyte uptake and excellent electrolyte retention resulting from its superior electrolyte wettability and highly porous structure, thereby offering better electrochemical performance compared to that of a commercial polyolefin separator (Celgard). Moreover, benefiting from the layered configuration, the tensile strength of the membrane can reach 13.5 MPa, which is close to the mechanical strength of the Celgard type along the transversal direction. The elaborate design of the multilayered structure allows the fabrication of a new class of thin separators with significant improvements in the mechanical and electrochemical performance. Given safer operation, the developed multilayer membrane may become a preferable separator required for high-power and high-energy storage devices. Full article

(This article belongs to the Special Issue Polymer Electrolyte Membranes)

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17 pages, 9618 KiB

Open AccessArticle

Synergistic Effect of 2-Acrylamido-2-methyl-1-propanesulfonic Acid on the Enhanced Conductivity for Fuel Cell at Low Temperature

by Murli Manohar and Dukjoon Kim

Membranes 2020, 10(12), 426; https://doi.org/10.3390/membranes10120426 - 15 Dec 2020

Cited by 6 | Viewed by 2420

Abstract

This present work focused on the aromatic polymer (poly (1,4-phenylene ether-ether-sulfone); SPEES) interconnected/ cross-linked with the aliphatic monomer (2-acrylamido-2-methyl-1-propanesulfonic; AMPS) with the sulfonic group to enhance the conductivity and make it flexible with aliphatic chain of AMPS. Surprisingly, it produced higher conductivity than [...] Read more.

This present work focused on the aromatic polymer (poly (1,4-phenylene ether-ether-sulfone); SPEES) interconnected/ cross-linked with the aliphatic monomer (2-acrylamido-2-methyl-1-propanesulfonic; AMPS) with the sulfonic group to enhance the conductivity and make it flexible with aliphatic chain of AMPS. Surprisingly, it produced higher conductivity than that of other reported work after the chemical stability was measured. It allows optimizing the synthesis of polymer electrolyte membranes with tailor-made combinations of conductivity and stability. Membrane structure is characterized by ¹H NMR and FT-IR. Weight loss of the membrane in Fenton’s reagent is not too high during the oxidative stability test. The thermal stability of the membrane is characterized by TGA and its morphology by SEM and SAXS. The prepared membranes improved proton conductivity up to 0.125 Scm⁻¹ which is much higher than that of Nafion N115 which is 0.059 Scm⁻¹. Therefore, the SPEES-AM membranes are adequate for fuel cell at 50 °C with reduced relative humidity (RH). Full article

(This article belongs to the Special Issue Polymer Electrolyte Membranes)

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16 pages, 2770 KiB

Open AccessFeature PaperArticle

Poly(meta/para-Terphenylene-Methyl Piperidinium)-Based Anion Exchange Membranes: The Effect of Backbone Structure in AEMFC Application

by T. S. Mayadevi, Seounghwa Sung, Listo Varghese and Tae-Hyun Kim

Membranes 2020, 10(11), 329; https://doi.org/10.3390/membranes10110329 - 05 Nov 2020

Cited by 24 | Viewed by 3610

Abstract

A series of poly(meta/para-terphenylene-methyl piperidinium)-based anion exchange membranes devoid of benzylic sites or aryl ether bonds, that are vulnerable to degradation by hydroxide ions, are synthesized and investigated for their application as novel anion exchange membranes. The copolymers are composed of [...] Read more.

A series of poly(meta/para-terphenylene-methyl piperidinium)-based anion exchange membranes devoid of benzylic sites or aryl ether bonds, that are vulnerable to degradation by hydroxide ions, are synthesized and investigated for their application as novel anion exchange membranes. The copolymers are composed of both linear para-terphenyl units and kink-structured meta-terphenyl units. The meta-connectivity in terphenyl units permits the polymer backbones to fold back, maximizing the interactions among the hydrocarbon polymer chains and enhancing the peripheral formation of ion aggregates, due to the free volume generated by the kink structure. The effects of the copolymer composition between para-terphenyl and meta-terphenyl on the morphology and the electrochemical and physicochemical properties of the corresponding polymer membranes are investigated. Full article

(This article belongs to the Special Issue Polymer Electrolyte Membranes)

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13 pages, 3051 KiB

Open AccessArticle

Quaternary Ammonium-Bearing Perfluorinated Polymers for Anion Exchange Membrane Applications

by Seunghyun Lee, Hyejin Lee, Tae-Hyun Yang, Byungchan Bae, Nguyen Anh Thu Tran, Younghyun Cho, Namgee Jung and Dongwon Shin

Membranes 2020, 10(11), 306; https://doi.org/10.3390/membranes10110306 - 26 Oct 2020

Cited by 12 | Viewed by 3680

Abstract

Perfluorinated polymers are widely used in polymer electrolyte membranes because of their excellent ion conductivity, which are attributed to the well-defined morphologies resulting from their extremely hydrophobic main-chains and flexible hydrophilic side-chains. Perfluorinated polymers containing quaternary ammonium groups were prepared from Nafion- and [...] Read more.

Perfluorinated polymers are widely used in polymer electrolyte membranes because of their excellent ion conductivity, which are attributed to the well-defined morphologies resulting from their extremely hydrophobic main-chains and flexible hydrophilic side-chains. Perfluorinated polymers containing quaternary ammonium groups were prepared from Nafion- and Aquivion-based sulfonyl fluoride precursors by the Menshutkin reaction to give anion exchange membranes. Perfluorinated polymers tend to exhibit poor solubility in organic solvents; however, clear polymer dispersions and transparent membranes were successfully prepared using N-methyl-2-pyrrolidone at high temperatures and pressures. Both perfluorinated polymer-based membranes exhibited distinct hydrophilic-hydrophobic phase-separated morphologies, resulting in high ion conductivity despite their low ion exchange capacities and limited water uptake properties. Moreover, it was found that the capacitive deionization performances and stabilities of the perfluorinated polymer membranes were superior to those of the commercial Fumatech membrane. Full article

(This article belongs to the Special Issue Polymer Electrolyte Membranes)

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14 pages, 2756 KiB

Open AccessArticle

Anion Exchange Membranes Prepared from Quaternized Polyepichlorohydrin Cross-Linked with 1-(3-aminopropyl)imidazole Grafted Poly(arylene ether ketone) for Enhancement of Toughness and Conductivity

by Cao Manh Tuan, Vo Dinh Cong Tinh and Dukjoon Kim

Membranes 2020, 10(7), 138; https://doi.org/10.3390/membranes10070138 - 30 Jun 2020

Cited by 13 | Viewed by 3920

Abstract

A novel anion exchange membrane was synthesized via crosslinking of the quaternized polyepichlorohydrin (QPECH) by 1-(3-aminopropyl) imidazole grafted poly(arylene ether ketone) (PAEK-API). While the QPECH provided an excellent ion conductive property, the rigid rod-structured PAEK-API played a reinforcing role, along with providing the [...] Read more.

A novel anion exchange membrane was synthesized via crosslinking of the quaternized polyepichlorohydrin (QPECH) by 1-(3-aminopropyl) imidazole grafted poly(arylene ether ketone) (PAEK-API). While the QPECH provided an excellent ion conductive property, the rigid rod-structured PAEK-API played a reinforcing role, along with providing the high conductivity associated with the pendant API group. The chemical structure of QPECH/PAEK-API membranes was identified by ¹H nuclear magnetic resonace spectroscopy. A variety of membrane properties, such as anion conductivity, water uptake, length swelling percentage, and thermal, mechanical and chemical stability, were investigated. The QPECH/PAEK-API1 membrane showed quite high hydroxide ion conductivity, from 0.022 S cm⁻¹ (30 °C) to 0.033 S cm⁻¹ (80 °C), and excellent mechanical strength, associated with the low water uptake of less than 40%, even at 80 °C. Such high conductivity at relatively low water uptake is attributed to the concentrated cationic groups, in a cross-linked structure, facilitating feasible ion transport. Further, the QPECH/PAEK-API membranes showed thermal stability up to 250 °C, and chemical stability for 30 days in a 4 NaOH solution, without significant loss of ion exchange capacity. Full article

(This article belongs to the Special Issue Polymer Electrolyte Membranes)

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