Cross-linked Polymer Electrolyte Membranes Research Articles

Synthesis of a Cross-Linked Polymer Electrolyte Membrane with an Ultra-High Density of Sulfonic Acid Groups

Synthesis of a Cross-Linked Polymer Electrolyte Membrane with an Ultra-High Density of Sulfonic Acid Groups

Tough and redox-mediated alkaline gel polymer electrolyte membrane for flexible supercapacitor with high energy density and low temperature resistance

To meet the practical application requirements of the flexible supercapacitors, the improvements of the toughness and energy density attract more and more attention. Herein, a physically cross-linked double network alkaline gel polymer electrolyte (AGPE) membrane based on PVA and kappa-carrageenan is developed. In this AGPE membrane, KOH plays a dual role including carrier donator and ion cross-linker, which makes the AGPE membrane show the unique improvement of ionic conductivity (0.31 S/cm) and mechanical properties (tensile strength of 1.62 MPa and tensile elongation of 670%) at the same time. In order to improve energy density, the redox-active mediator p-phenylene diamine has been introduced in the AGPE membrane, endowing the fabricated supercapacitor with high electrode specific capacitance (741 F/g) and energy density (18.3 Wh/kg) with a maximum power density of 800 W/kg. Meanwhile, the supercapacitor can exhibit great flexibility and toughness, and maintain stable capacitance performance under bending and stretching state. Moreover, the supercapacitor shows an excellent low temperature resistance and it is able to maintain 82% of its room-temperature capacitance even at -40 °C. This investigation offers a strategy to prepare gel polymer electrolyte membrane with high adaptive ability of deformation and low temperature, which has potential application in various flexible, portable and wearable electronics. • Dual role KOH can improve conductivity and mechanical properties simultaneously. • PPD can signally increase the capacitance and energy density of EDLC supercapacitor. • Supercapacitor shows ideal electrochemical properties under deformation and coldness.

Self-Healing of a Covalently Cross-Linked Polymer Electrolyte Membrane by Diels-Alder Cycloaddition and Electrolyte Embedding for Lithium Ion Batteries.

Thermally reversible self-healing polymer (SHP) electrolyte membranes are obtained by Diels-Alder cycloaddition and electrolyte embedding. The SHP electrolytes membranes are found to display high ionic conductivity, suitable flexibility, remarkable mechanical properties and self-healing ability. The decomposition potential of the SHP electrolyte membrane is about 4.8 V (vs. Li/Li+) and it possesses excellent electrochemical stability, better than that of the commercial PE film which is only stable up to 4.5 V (vs. Li/Li+). TGA results show that the SHP electrolyte membrane is thermally stable up to 280 °C in a nitrogen atmosphere. When the SHP electrolyte membrane is used as a separator in a lithium-ion battery with an LCO-based cathode, the SHP membrane achieved excellent rate capability and stable cycling for over 100 cycles, and the specific discharge capacity could be almost fully recovered after self-healing. Furthermore, the electrolyte membrane exhibits excellent electrochemical performance, suggesting its potential for application in lithium-ion batteries as separator material.

UV-Cured Cross-Linked Astounding Conductive Polymer Electrolyte for Safe and High-Performance Li-Ion Batteries.

UV-cured cross-linked polymer electrolytes are promising electrolytes for safe Li-ion batteries (LIBs) application due to their excellent conduction ability, low glass-transition temperature (Tg), and high discharge capacity. Herein, we have prepared novel fluorosulfonylimide methacrylic-based cross-linked polymer electrolyte membranes for LIBs via UV-curing process, which is a well-known, easy, low-cost, fast, and reliable technique. The synthesized UV-reactive novel methacrylate monomer with directly attached fluorosulfonylimide functional group methacryloylcarbamoyl sulfamoyl fluoride (MACSF) was used as a precursor for UV curing along with poly(ethylene glycol) dimethacrylate (PEGDMA) and lithium bis(fluorosulfonyl)imide (LiFSI). The results demonstrated that the cross-linked membrane with an optimized amount (30 wt %) of MACSF monomer (noted as CPE-3) showed the best performance. The nonflammable fluorosulfonyl group (a hydrophilic group of MACSF monomer) in the polymer matrix formed a wide channel, as a result of which Li ion can migrate easily via forming an ionic linkage. The CPE-3 electrolyte exhibited a low Tg (-79 °C), excellent phase separation, high conductivity (σ) (ca. 3.5 × 10-4 and 8.50 × 10-3 S·cm-1 at 30 and 80 °C, respectively), and high flame retardancy. The battery performance of half-cell (LiFePO4/CPE-3/Li) and full cell (LiFePO4/CPE-3/graphite) with CPE-3 electrolyte were attractive: discharge capacities (155 and 152 mAh/g) with the capacity retentions of 96.17 and 95.17% after 500 cycles at 0.1 C rate for half-cell and full-cell LIBs, respectively.

Nanostructured high-performance electrolyte membranes based on polymer network post-assembly for high-temperature supercapacitors

The development of high-temperature supercapacitors highly relies on the explore of stable polymer electrolyte membranes (PEMs) with high ionic conductivities at high-temperature conditions. However, it is a challenge to achieve both high stability and high conductivity in a PEM at elevated temperatures. Herein, we report the fabrication of high-performance proton conductive PEMs suitable for high-temperature supercapacitors (HT-SCs), which is based on a post-assembly strategy to control the rearrangement of polymer networks in the PEMs. This strategy can create cross-linked PEMs with bicontinuous nanostructures, as well as highly stable and highly conductive features. Specifically, a series of bicontinuous PEMs are prepared by the controllable cross-linking of poly(ether-ether-ketone) and poly(4-vinylpyridine), followed by the inducement of phosphoric acid. These PEMs exhibit both a high proton conductivity of 70 mS cm−1 and a high modulus of 39.3 MPa at 150 ℃, which can serve as high-performance electrolytes. The HT-SCs based on these PEMs display a specific capacitance of 138.0 F g−1 and a high capacitance retention of 80.0% after 2500 galvanostatic charge–discharge cycles at 150 ℃, exhibiting excellent high-temperature capacitance and cycle stability. This post-assembly concept can provide a new route to design high-performance PEMs for HT-SC and other energy device applications.

Silica-assisted cross-linked polymer electrolyte membrane with high electrochemical stability for lithium-ion batteries

This study aims to prepare an organic-inorganic reticular polymer electrolyte. Isocyanate acts as a bridge that connects fumed silica and PEO molecular chains. The PEO-TDI-SiO2 solid polymer electrolytes developed can significantly have improved ionic conductivity of 0.12 mS cm−1 at ambient temperature. This is because the TDI-SiO2 nanoparticles inhibits polymer crystallization which provides more continuous Li-ion transport pathways. Tests at 60 °C indicate that the cross-linked structure of covalent TSI bonded to PEO effectively enlarges the electrochemical window of the polymer electrolyte to 5.6 V. Also, the PTSI electrolyte membrane has a higher Li+ transference number of 0.33 compared to the PEO-LiTFSI electrolytes. It is worth noting that the assembled LiFePO4|PTSI8%|Li cells deliver outstanding rate performance and stable cycling performance. All these considerable merits of PTSI membrane demonstrate that PTSI is a promising candidate that can be used as solid polymer electrolytes for the next-generation Li-ion batteries.

Dual cross-linked polymer electrolyte membranes based on poly(aryl ether ketone) and poly(styrene-vinylimidazole-divinylbenzene) for high temperature proton exchange membrane fuel cells

One critical issue to phosphoric acid (PA) doped high-temperature proton exchange membranes (HT-PEMs) is to balance the proton conductivity and mechanical properties for overall application performance in fuel cells. Addressing the issue, we prepare durable HT-PEMs having the dual crosslinking structure by employing poly(vinylimidazole-divinylbenzene-styrene) (poly(VIm-DVB-St)) copolymer as a crosslinker and using the poly (aromatic ether ketone) (PAEK) polymer containing four methyl groups as the host membrane matrix. The imidazole groups of poly(VIm-DVB-St) react with benzyl bromide groups of brominated PAEK for both the primary cross-linking network and high PA doping. The divinylbenzene crosslinked poly (styrene-co-vinylimidazole) network generates the secondary cross-linking structure. The formed reticular polymer chain structure brings on low swelling and high mechanical strength of the HT-PEMs. The fuel cell based on the acid doped PAEK41-85%VIm/233.0 PA shows a H2-air fuel cell peak power density of 306 mW cm−2 at 200 °C without back pressure, and a low degradation rate of 3.9 × 10−5 V h−1 during a period of 600 h under a constant current density of 200 mA cm−2 at 160 °C.

Well-designed Crosslinked Polymer Electrolyte Enables High Ionic Conductivity and Enhanced Salt Solvation

A new facile single-step method to fabricate crosslinked polymer electrolyte membranes consisting of branched poly(ethyleneimine), (PEI) and poly(ethylene oxide), (PEO) is demonstrated. The membranes exhibit excellent ionic conductivity (1.2 × 10−3 S cm−1 at 80 °C) with minimal addition of plasticizer (20 wt%). The amine functional group in the PEI-PEO crosslinked matrix provides Lewis basic and hydrogen bonding characteristics that facilitate the dissolution of lithium salt and enables a higher cation transport number than a PEO crosslinked matrix. The glass transition temperature, degree of crystallinity, and room temperature storage modulus increases with decreasing crosslink density and increasing ratio of free amines. The resultant ionic conductivity and mechanical strength can be flexibly tailored by varying the molar ratio of free amine moieties in the crosslinked PEI-PEO matrix. This study provides an improved synthesis method, in-depth characterization, and fundamental insights on the effect of free amine moieties on the transport properties of a highly conductive gel polymer electrolyte.

Fabrication and characterizations of soft and flexible Poly(dimethylsiloxane)-incorporated network polymer electrolyte membranes

Simultaneous improvements in both structural and ionic conductive properties in solid polymer electrolytes are crucial for developing all-solid-state rechargeable lithium ion batteries with high performance and long-term durability. The incorporation of polydimethylsiloxane (PDMS) units into polymer electrolyte system can provide a route to achieve good lithium ion conduction and mechanical properties. Herein, we prepare cross-linked network polymer electrolyte membranes comprising of poly (ethylene glycol)-diacrylate and methacrylate-terminated PDMS that covalently bonded with four-arm cross-linker with thiol terminal groups via a single-pot facile in-situ thiol-ene polymerization method. The network polymer electrolyte membranes provide the unprecedented combination of mechanical strength, ionic conductivity, and merits for good interfacial compatibility with electrodes in all-solid-state battery applications. The overall performance demonstrates that the PDMS-based electrolytes are promising solid electrolytes for future high-performance rechargeable lithium ion batteries.

Ion dynamics, rheology and electrochemical performance of UV cross-linked gel polymer electrolyte for Li-ion battery

The structural, vibrational, thermal, rheological, electrical, and dielectric properties of a series of UV cross-linked gel polymer electrolyte membranes, comprising ionic liquid, carbonate plasticizers, and lithium tetrafluoroborate salt, are investigated using x-ray diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetry, rheology, and broadband dielectric spectroscopy. Rheological studies suggest that the synthesized gel polymer electrolyte membranes exhibit stable elastic behavior. The ionic transport mechanism and relaxation dynamics are systematically studied using broadband dielectric spectroscopy. The conductivity of these semi-interpenetrating polymer network based gel polymer electrolytes is found to be ∼10−3 S cm−1. The composition, which shows the highest conductivity value of 6.69×10−3 S cm−1 at ambient temperature, is also mechanically very much stable at a yield stress of 872 Pa. Hence, this gel polymer electrolyte is worthy of the device fabrication. Finally, coin cell batteries are fabricated using these gel polymer electrolyte membranes and their electrochemical performance is analyzed using electrochemical impedance spectroscopy. The optimized gel polymer electrolyte membrane shows long-term oxidative stability against lithium. The batteries also exhibit excellent cyclability.

Bicontinuously crosslinked polymer electrolyte membranes with high ion conductivity and mechanical strength

Recently, safety has become an important issue for energy storage devices due to explosion and leakage of conventional liquid electrolytes. Traditional polymer electrolytes also have a strong dependence on the tradeoff relationship and do not exhibit sufficient ionic conductivity as a solid; thus, they are often used as a gel. We report the preparation of a highly ion-conductive, mechanically strong solid electrolyte membranes based on bicontinuously crosslinked polymer electrolytes for solid-state supercapacitors. The solid electrolyte membranes are synthesized in situ via facile ring-opening polymerization in the presence of a conductive ionic liquid without any solvents. The crosslinking structure is based on the reaction of the amines of the polyethylenimine oligomer with the epoxy groups of hydrophilic poly(ethylene glycol) diglycidyl ether and hydrophobic bisphenol A diglycidyl ether at 50 °C for 3 h. This unique structure endows the solid electrolyte membranes with high tensile strength as well as high ion conductivity (2.41 × 10−3 S cm−1 at 25 °C). All the membranes have good thermal stability and an amorphous phase in which the ionic species are uniformly distributed in the matrix. Upon application to solid-state supercapacitors based on carbon electrodes, a capacitance of 19.8 F g−1 at 2 mV s−1 is obtained, with an excellent capacitance retention and a coulombic efficiency close to 100% for 10,000 cycles. The solid electrolyte membrane has potential applications in structural supercapacitors and batteries, which require high mechanical strength.

High-performance binary cross-linked alkaline anion polymer electrolyte membranes for all-solid-state supercapacitors and flexible rechargeable zinc–air batteries

A high-performance binary cross-linked alkaline anion polymer electrolyte membrane was fabricated for energy storage and conversion devices.

Deformable and flexible electrospun nanofiber-supported cross-linked gel polymer electrolyte membranes for high safety lithium-ion batteries

A deformable and flexible Li/CGPE/LiFePO4 cell based on CGPE-3 exhibited a high specific capacity and superior cycling stability for lithium-ion batteries.

Enhanced proton conductivity at low humidity of proton exchange membranes with triazole moieties in the side chains

Highly conductive, novel sulfonated poly(arylene ether) membranes with different amounts of triazole-introduced monomers (SPAE-TM) were prepared via conventional aromatic condensation reactions. The triazole-introduced monomer (TM) was used as a proton transfer moiety to increase the proton conductivities of polymer electrolyte membranes (PEMs). To compare the chemical, mechanical and thermal stabilities of non-crosslinked polymer electrolyte membranes (SPAE-TM10, SPAE-TM20), crosslinked polymer electrolyte membranes were prepared via the thermal crosslinking method (cSPAE-TM10, cSPAE-TM20). The SPAE-TM membranes exhibited excellent thermal stabilities, and the non-crosslinked SPAE-TM membranes showed satisfactory glass transition temperatures (Tg=250°C). The water uptakes and swelling ratios of the SPAE-TM membranes were successfully suppressed in comparison with the SPAE-TM0 membrane. The proton conductivities of all membranes were higher than those of Nafion 212 over a wide range of temperatures (0.211–0.256S/cm at 80°C, 100% R.H.). The SPAE-TM20 presented a proton conductivity that was 2.3 times higher than that of SPAE-TM0 at 80°C and 30% R.H.

Effect of Plasticization on Ionic Conductivity Enhancement in Relation to Glass Transition Temperature of Crosslinked Polymer Electrolyte Membranes

The relationship between glass transition (Tg) and ionic conductivity (σ) of an amorphous crosslinked polymer electrolyte membrane (PEM) was examined based on ion–dipole complexation between dissociated lithium cations and ether oxygen of poly(ethylene glycol diacrylate) and plasticization by succinonitrile (SCN). In a binary PEM consisting of a lithium salt/polymer network, Tg increased due to a strong ion–dipole interaction, whereas σ declined due to lower ion mobility coupled to reduced chain mobility. Above the threshold salt concentration of 7 mol %, dual loss tangent peaks were observed in dynamic mechanical studies, which may be ascribed to segmental relaxations of ion–dipole complexed networks and that of polymer chains surrounding the undissociated lithium salt acting like “fillers”. Upon SCN plasticization, these two peaks merged into one that was further suppressed below Tg of the pure network, whereas σ improved to the superionic conductor level. The role of plasticization on the ionic conduct...

Guanidimidazole-quanternized and cross-linked alkaline polymer electrolyte membrane for fuel cell application

A modified imidazole, namely guanidimidazole (GIm) was designed and synthesized as a novel quaternizing- and cross-linking agent for alkaline polymer electrolyte membrane fabrication. The resulting membrane was more alkali tolerant and swelling resistant than that quaternized purely by 1-methylimidazole owing to the enhanced resonance and cross-linking ability of GIm, the former confirmed by a LUMO (lowest unoccupied molecular orbital) energy calculation. The membrane also showed good ionic conductivity, mechanical strength and thermal stability. A H2/O2 fuel cell using the synthesized membrane showed a peak power density of 39mWcm−2 at 50°C. This work preliminarily demonstrates the beneficial effect of imidazole modification by both experimental and computational investigation; it provides a new cation design strategy that may potentially achieve simultaneous improvement of alkali stability and swelling resistance of alkaline electrolyte membranes.

Gradiently crosslinked polymer electrolyte membranes in fuel cells

Polymer electrolyte membranes in fuel cells should be high in both ionic conductivity and mechanical strength. However, the two are often exclusive to each other. To solve this conundrum, a novel strategy is proposed in this paper, with extensively researched sulfonated poly (ether ether ketone) (SPEEK) membrane as a paradigm. A SPEEK membrane of high sulfonation degree is simply post-treated with NaBH4 and H2SO4 solution at ambient temperature for a certain time to afford the membrane with a gradient crosslinking structure. Measurements via 1H NMR, ATR-FTIR and SEM-EDS are conducted to verify such structural changes. The gradient crosslinks make practically no damage to proton conductance, but effectively restrain the membrane from over swelling and greatly enhance its tensile strength. A H2–O2 fuel cell with the gradiently crosslinked SPEEK membrane shows a maximal power density of 533 mW cm−2 at 80 °C, whereas the fuel cell with the pristine SPEEK membrane cannot be operated beyond 30 °C.

EB‐crosslinked Polymer Electrolyte Membranes Based on Highly Sulfonated Poly(ether ether ketone) and Poly(vinylidene fluoride)/Triallyl Isocyanurate

AbstractIn this study, crosslinked polymer electrolyte membranes for polymer electrolyte membrane fuel cell (PEMFC) applications are prepared using electron beam irradiation with a mixture of sulfonated poly(ether ether ketone) (SPEEK), poly(vinylidene fluoride) (PVDF), and triallyl isocyanurate (TAIC) at a dose of 300 kGy. The gel‐fraction of the irradiated SPEEK/PVDF/TAIC (95/4.5/0.5) membrane is 87% while the unirradiated membrane completely dissolves in DMAc solvent. In addition, the water uptake of the irradiated membrane is 221% at 70 °C while that of the unirradiated membrane completely dissolves in water at above 70 °C. The ion exchange capacity and proton conductivity of the crosslinked membrane are 1.57 meq g−1, and 4.0 × 10−2 S cm−1 (at 80 °C and RH 90%), respectively. Furthermore, a morphology study of the membranes is conducted using differential scanning calorimetry and X‐ray diffractometry. The cell performance study with the crosslinked membrane demonstrates that the maximum power density is 518 mW cm−2 at 1036 mA cm−2 and the maximum current density at applied voltage of 0.4 V is 1190 mA cm−2.

Bi-functionalized copolymer-sulphonated SiO2 embedded with aprotic ionic liquid based anhydrous proton conducting membrane for high temperature application

We prepared highly charged bi-functionalized copolymer (BFC) and sulphonated mesoporous silica embedded with aprotic ionic liquid (IL) (1-ethyl-3-methylimidazolium ethyl sulfate) based anhydrous conducting cross-linked polymer electrolyte membrane (PEM) by sol–gel. Composite PEMs with 0–10wt% sulphonated silica and 20wt% IL content (BFC/Si-x/IL) were characterized by their morphology, stability, IEC, water retention ability and temperature dependent anhydrous conductivity. Conductivity of pristine BFC membrane (1.57mScm−1) was increased with incorporation of sulphonated-SiO2 (10wt%) in the membrane matrix (BFC/Si-10) (3.56mScm−1), may be due to formation of interconnected network or channels in the membrane matrix. After embedding of aprotic IL (20wt%; ~80µS/cm conductivity) in highly acidic polymer (BFC/Si-10), conductivity of BFC/Si-10/IL composite PEM was about 8.79mScm−1 at 30°C. High anhydrous conductivity for BFC/Si-10/IL PEM was attributed to the exchanged protons from highly acidic membrane matrix by IL cation, and accordingly a mechanism was proposed. Further, enhanced bound water content and thus slow dehydration of BFC/Si-x/IL composite PEMs, make them a promising candidate for fuel cell application under low humidification.

An all-solid-state lithium ion battery electrolyte membrane fabricated by hot-pressing method

A cross-linked polymer electrolyte membrane (SPE) was fabricated by a solvent-free hot-pressing method for all-solid-state lithium ion battery. The ionic conductivity of the electrolyte is 1.34 × 10−3 S cm−1 and the decomposition potential is 4.87 V at the ethylene oxide (EO):LiN(SO2CF3)2 (LiTFSI) molar ratio of 20:1 and 120 °C. TG-DSC results show that the SPE is thermally stable up to 230 °C in argon atmosphere. The assembled LiFePO4/SPE/Li all-solid-state battery can stably work in the temperature range of 80–140 °C. At 120 °C, the initial discharge capacity of the battery is 156.7 mAh g−1 at 1C which is close to the theoretical capacity of the cathode material, showing that the solvent-free filming method is low-cost and environment-friendly for solid polymer electrolyte and all-solid-state lithium ion battery.