Composite proton-conducting membranes

Abstract

A composite proton-conducting membrane comprising: an inorganic filler having covalently bonded acidic functional groups and a high surface area of at least 150 m 2 / g; and a water-insoluble ion-conducting polymer. The membrane for redox flow battery, fuel cell, and electrolysis applications provides advantages over traditional polymeric proton-conducting membranes, including: 1) improved proton conductivity / permeability due to the formation of additional nanochannels for proton conduction; 2) improved proton / electrolyte selectivity for redox flow battery applications; 3) reduced swelling of the membrane and permeation of gases or electrolytes; 4) improved chemical stability; 5) increased battery operation time with stable performance; and 6) reduced membrane cost.

Description

[0001] Priority Statement

[0002] This application claims priority to U.S. Application No. 17 / 162,421, filed January 29, 2021, the entire contents of which are incorporated herein by reference. Background Technology

[0003] Energy storage systems play a crucial role in harvesting energy from a variety of sources. These systems can be used to store energy and convert it for use in many different applications, such as buildings, transportation, public services, and industry. A wide variety of energy storage systems are already in commercial use, and new systems are currently under development. Energy storage systems can be categorized as electrochemical and battery, thermal, thermochemical, flywheel, compressed air, pumped hydro storage, magnetic, biological, chemical, and hydrogen storage. There is a need to develop cost-effective and eco-friendly energy storage systems to address the energy crisis and overcome the mismatch between power generation and end-use.

[0004] Renewable energy sources, such as wind and solar, have transient characteristics that require energy storage. Renewable energy storage systems, such as redox flow batteries (RFBs), have attracted significant attention from the power grid, electric vehicles, and other large-scale stationary applications. RFBs are electrochemical energy storage systems that directly and reversibly convert chemical energy into electricity. By converting electricity into hydrogen as an energy carrier through water electrolysis without producing carbon monoxide or carbon dioxide as byproducts, they integrate the power, chemical, transportation, and heating sectors. Hydrogen plays a crucial role in the path towards an environmentally friendly, low-carbon energy structure, serving as an energy carrier for grid balancing or power-to-gas and power-to-liquid processes. Water electrolysis produces high-quality hydrogen by electrochemically decomposing water into hydrogen and oxygen; this reaction is given by Equation 1. The water electrolysis process is endothermic, and electricity is the energy source. When operated using renewable energy sources such as wind, solar, or geothermal energy, water electrolysis has a zero carbon footprint. Major water electrolysis technologies include alkaline electrolysis, proton exchange membrane (PEM) electrolysis, anion exchange membrane (AEM) electrolysis, and solid oxide electrolysis. In a PEM water electrolysis system, the anode and cathode are separated by a solid PEM electrolyte, such as a trademarked... Fluoropolymer copolymer based on sulfonated tetrafluoroethylene, sold by Chemours Company. The anode and cathode catalysts typically contain IrO2 and Pt, respectively. At the positively charged anode, pure water is oxidized to produce oxygen and electrons (e). -The reaction is given by Equation 2. Protons are transported from the anode to the cathode via a proton-conducting PEM. At the negatively charged cathode, a reduction reaction occurs, where electrons from the cathode are donated to protons to form hydrogen; this reaction is given by Equation 3. The PEM not only conducts protons from the anode to the cathode but also separates the H2 and O2 produced in the water electrolysis reaction. PEM water electrolysis is one of the advantageous methods for converting renewable energy into high-purity hydrogen, with advantages such as high pressure differential, high current density, high efficiency, fast response, small footprint, low temperature (20°C–90°C) operation, and compact system design with high-purity oxygen byproducts. However, one of the main challenges of PEM water electrolysis is the high capital cost of the battery stack, including expensive acid-resistant stack hardware, expensive precious metal catalysts required for the electrodes, and expensive PEM.

[0005] Water electrolysis reaction: 2H₂O → 2H₂ + O₂ (1)

[0006] Anodizing reaction: 2H₂O → O₂ + 4H + +4e - (2)

[0007] Cathodic reduction reaction: 2H + +2e - →H2 (3)

[0008] Fuel cells, as a next-generation clean energy source, convert the energy from chemical reactions such as the oxidation / reduction redox reaction of hydrogen and oxygen into electrical energy. The three main types of fuel cells are alkaline electrolyte fuel cells, polymer electrolyte membrane fuel cells, and solid oxide fuel cells. Polymer electrolyte membrane fuel cells can include proton exchange membrane fuel cells (PEMFCs), anion exchange membrane fuel cells (AEMFCs), and direct methanol fuel cells.

[0009] The anode in an electrochemical cell is the electrode where the main reaction is oxidation (e.g., the water oxidation / oxygen evolution reaction electrode used in water or CO2 electrolyzers, or the hydrogen oxidation electrode used in fuel cells).

[0010] Significant advancements are needed in cost-effective catalysts, membrane materials, and other battery stack components for PEM water electrolysis and PEMFC, which have wide applications in renewable energy systems.

[0011] An RFB (Reduction Flow Battery) consists of two external storage tanks filled with active material, two circulation pumps, and a flow cell with a separation membrane. This active material contains metal ions that can be in different valence states. The separation membrane is located between the anode and cathode and is used to separate the anolyte and catholyte, and to utilize the current loop by allowing the transfer of equilibrium ions. The anolyte, catholyte, anode, and cathode can also be referred to as electroplating electrolyte or negative electrode electrolyte, redox electrolyte or positive electrode electrolyte, electroplating electrode or negative electrode, and redox electrode or positive electrode, respectively. Of all redox flow batteries developed to date, the vanadium redox flow battery (VRFB) has been the most extensively studied. VRFB uses the same vanadium element in both half-cells, which prevents electrolyte permeation contamination from one half-cell to the other. However, VRFB is inherently expensive due to the use of high-cost vanadium and expensive membranes. The all-iron redox flow battery (IFB) is particularly attractive for grid-scale storage applications due to the use of low-cost and readily available iron, salt, and water as electrolytes, and the non-toxicity of the system. The IFB uses iron in different valence states as the positive and negative electrode electrolytes, respectively. The iron-based positive and negative electrode electrolyte solutions, stored in an external storage tank, flow through the battery stack. The cathode-side half-cell reaction involves the deposition and dissolution of iron in solid plate form; this reaction is given by Equation 4. The anode-side half-cell reaction involves the deposition and dissolution of Fe during charging. 2+ Losing electrons to form Fe 3+ And during discharge Fe 3+ Gain electrons to form Fe 2+ The reaction is given by Equation 5. The overall reaction is shown in Equation 6.

[0012] Redox electrode:

[0013] Electroplating electrodes:

[0014] total:

[0015] Membranes are one of the key materials in batteries or electrolyzers, serving as a crucial driver of safety and performance. Some important properties of membranes used in flow batteries, fuel cells, and membrane electrolysis include high conductivity, high ion permeability (porosity, pore size, and pore size distribution), high ion exchange capacity (for ion exchange membranes), high ion / electrolyte selectivity (low permeability / permeability to the electrolyte), and low cost (less than $150 / m³). 2 -$200 / m 2It features low areal resistivity that minimizes efficiency loss due to ohmic polarization, high tolerance to oxidative and reducing conditions, chemical inertness over a wide pH range, high thermal stability along with high proton conductivity (greater than or equal to 120°C for fuel cells), high proton conductivity at high temperatures in the absence of H2O, high proton conductivity at high temperatures while maintaining high RH, and high mechanical strength (thickness, low swelling).

[0016] The two main types of membranes used in redox flow batteries, fuel cells, and electrolysis applications are polymer ion exchange membranes and microporous separators. Polymer ion exchange membranes can contain -SO3... - -COO - -PO3 2- -PO3H - or -C6H4O - Cation exchange membranes with cation exchange functional groups, including -NH3 + -NRH2 + -NR2H + -NR3 + or -SR2 - Anion exchange membranes with anion exchange functional groups, or bipolar membranes comprising both cation exchange polymers and anion exchange polymers. The polymers used to prepare the ion exchange membranes can be perfluorinated ionomers (such as...). and -F), partially fluorinated polymers, non-fluorinated hydrocarbon polymers, non-fluorinated polymers with aromatic backbones, or acid-base blends. Generally speaking, membranes based on perfluorosulfonic acid (PFSA), such as and They are used in vanadium redox flow battery (VRFB) systems due to their oxidative stability, good ionic conductivity, unique morphology, mechanical strength, and high electrochemical performance. However, these membranes exhibit low equilibrium ion / electrolyte metal ion selectivity and high electrolyte metal ion permeation, which leads to capacitance decay in VRFBs, and they are also expensive.

[0017] Microporous and nanoporous membrane separators can be inert microporous / nanoporous polymer membrane separators, inert nonwoven porous membranes, or separators coated / impregnated with polymer / inorganic materials. Inert microporous / nanoporous polymer membrane separators can be microporous polyethylene (PE), polypropylene (PP), PE / PP, or composite inorganic / PE / PP membranes, inert nonwoven porous membranes, nonwoven PE, PP, polyamide (PA), polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC), polyethylene terephthalate (PET), or polyester porous membranes. For example, microporous membranes made of PE, PP, or copolymers of PE and PP polymers. and Membrane separators are commercially available. They typically have high ionic conductivity, but also high electrolyte permeation for RFB applications.

[0018] Despite extensive research efforts, there remains a need for a reliable, high-performance (low gas permeation and excellent conductivity), low-cost membrane for electrochemical conversion and storage applications, such as redox flow batteries, fuel cells, and electrolysis applications. Attached Figure Description

[0019] Figure 1 The 5AMPA-D2021 and Water electrolysis performance of 212MEA at 80℃ and atmospheric pressure.

[0020] Figure 2 In the 5AMPA-D2021 MEA, the polarization voltage decreases as the operating temperature increases from 80°C to 100°C. Detailed Implementation

[0021] Most electrochemical conversion and storage systems (such as electrolyzers, fuel cells, and redox flow batteries) rely on the stable, high performance of ion-conducting membranes. These systems cannot achieve the desired long-term performance if the membrane cannot effectively separate electrochemically active substances (e.g., electrodes, electrolytes) from products and byproducts (e.g., oxygen and hydrogen) and conduct specific ions (e.g., protons and supporting non-electrochemically active electrolyte cations) to mediate electrochemical reactions occurring at the anode and cathode.

[0022] This invention provides a novel composite proton-conducting membrane, and more specifically, a novel composite proton-conducting membrane comprising: an inorganic filler having covalently bonded acidic functional groups and at least 150 μm 2 / g, or at least 300m 2 / g, or at least 400m 2 High surface area per gram; water-insoluble ion-conducting polymer; and optionally, a microporous supporting membrane. This novel composite proton-conducting membrane can be used in electrochemical energy systems such as electrolyzers, fuel cells, and redox flow batteries. Other aspects include methods for manufacturing the membrane, membrane electrode assemblies for water electrolysis or fuel cell systems, and redox flow battery systems incorporating the composite proton-conducting membrane.

[0023] It contains acidic functional groups with covalent bonds and at least 150m 2A novel composite proton-conducting membrane is provided by incorporating a high-surface-area inorganic filler into a water-insoluble ion-conducting polymer. This novel composite proton-conducting membrane possesses additional nanochannels with acidic proton-conducting functional groups for proton conduction, and exhibits good adhesion between the inorganic filler and the water-insoluble ion-conducting polymer matrix. The thickness of the composite proton-conducting membrane is typically in the range of 5 μm to 500 μm, or 20 μm to 300 μm, or 20 μm to 200 μm. The inorganic filler is dispersed in the water-insoluble ion-conducting polymer matrix to form a dense, non-porous composite proton-conducting membrane.

[0024] Compared with traditional polymer proton-conducting membranes (such as...) and In contrast, it contains acidic functional groups with covalent bonds and at least 150m 2 The advantages of novel composite proton-conducting membranes with high surface area inorganic fillers for redox flow batteries, fuel cells, and electrolysis applications include: 1) improved proton conductivity / permeability due to the formation of additional nanochannels for proton conduction; 2) improved proton / electrolyte selectivity in redox flow batteries; 3) reduced membrane swelling and gas or electrolyte permeation; 4) improved chemical stability; 5) increased battery operating time with stable performance; and 6) reduced membrane cost.

[0025] Contains acidic functional groups with covalent bonds and at least 150m 2 A novel composite proton-conducting membrane for redox flow batteries, fuel cells, and electrolysis applications, comprising a high surface area inorganic filler, a water-insoluble ion-conducting polymer, and optionally a microporous support membrane, exhibits high ionic conductivity and can conduct charged ions (such as protons and / or potassium cations (K+)) into a single layer. + The ionic conductivity (σ) of the membrane is a measure of its ability to conduct charged ions from one side to the other to maintain the circuit. During the operation of an electrochemical cell, electrical equilibrium is achieved by the transport of charged ions (such as protons in PEM water electrolysis, protons in an all-iron redox flow cell system, potassium cations, ammonium cations, or sodium cations) across the composite proton-conducting membrane. The ionic conductivity (σ) of the membrane is a measure of its ability to conduct charged ions, and the unit of measurement for conductivity is Siemens per meter (S / m). The ionic conductivity (σ) of the composite proton-conducting membrane can be measured by determining the resistance (R) of the membrane between two electrodes separated by a fixed distance. The resistance can be determined by electrochemical impedance spectroscopy (EIS), and the unit of measurement for resistance is ohms (Ohm). The area resistivity (RA) is the product of the membrane resistance (R) and the effective area (A) of the membrane, and the unit of measurement for area resistivity is (Ω·cm). 2The membrane ionic conductivity (σ, S / cm) is proportional to the membrane thickness (L, cm) and related to the membrane area resistivity (RA, Ω·cm). 2 It is inversely proportional to the others.

[0026] The performance of composite proton-conducting membranes used in RFB applications can be evaluated using several parameters, including membrane solubility and stability in the electrolyte, areal resistivity, battery charge / discharge cycle count, electrolyte permeation through the membrane, voltage efficiency (VE), coulombic efficiency (CE), and energy efficiency (EE) of the RFB battery. CE is the ratio of the battery's discharge capacity to its charge capacity. A higher CE, indicating lower capacity loss, is primarily due to the lower permeation rate of electrolyte ions (such as ferric and ferrous ions) in the iron-redox flow battery system. VE is defined as the ratio of the battery's average discharge voltage to its average charge voltage (see M. Skyllas-Kazacos, C. Menictas, and T. Lim, Chapter 12 on Redox Flow Batteries for Medium to Large-Scale Energy Storage in Electricity Transmission, Distribution and Storage Systems, A volume in Woodhead Publishing Series in Energy, 2013). A higher VE, indicating higher ionic conductivity, is primarily due to the membrane's low areal resistivity. EE is the product of VE and CE and is an indicator of energy loss during charge-discharge. EE is a key parameter for evaluating energy storage systems.

[0027] The performance of composite proton-conducting membranes for water electrolysis applications was evaluated using polarization voltage (total cell voltage), high-frequency resistance (HFR), and gas permeation. Polarization voltage (E... cell E is given in Equation 7, where E rev R is the reversible battery voltage, which is a function of temperature and pressure, and i is the current. memb R e and R H+ These are the ohmic resistance of the membrane, the resistance of the electrical contacts, and the effective proton transport resistance in the electrodes, respectively. η HER and η OER It is the kinetic overpotential of the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), η mtThe additional resistance related to mass transport is described (Journal of the Electrochemical Society (JElectrochem.Soc.), 2016, 163, F3179). The high-frequency resistance (HFR) is equal to R. memb +R e +R H+ Therefore, a lower HFR generally indicates a higher membrane conductivity. Gas permeation (e.g., hydrogen and oxygen in water electrolyzers) is a parameter for evaluating the hydrogen and oxygen permeability of the membrane under water electrolysis conditions. Low gas permeation (especially hydrogen permeation) is preferred for energy efficiency and safety reasons. The performance of PEM electrolyzer cells or PEMFCs, which respectively contain composite proton conduction membranes and commercially available proton exchange membranes, can be compared by their polarization curves, which are obtained by plotting the relationship between polarization voltage and current density. Unlike PEM fuel cells, the better the PEM electrolyzer, the lower the cell voltage at a given current density in the polarization curve.

[0028] Polarization voltage equation: E cell =E rev +i·(R memb +R e +R H+ )+η HER +η OER +η mt (7)

[0029] The novel composite proton-conducting membrane contains covalently bonded acidic functional groups and at least 150m... 2 / g, or at least 300m 2 / g, or at least 400m 2 The high surface area inorganic filler can be selected from, but is not limited to, silica gel, precipitated silica, fumed silica, colloidal silica, alumina, silica-alumina, zirconium oxide, molecular sieves, metal-organic frameworks, zeolite imidazole salt frameworks, covalent organic frameworks, or combinations thereof, wherein the filler comprises covalently bonded acidic functional groups and 150 m 2 / g or higher, or 300m 2 / g or higher, or 400m 2Both have a high surface area of ​​ / g or higher. Molecular sieves have a framework structure, characterized by a unique wide-angle X-ray diffraction pattern. Zeolites are a subclass of molecular sieves based on aluminosilicate compositions. Non-zeolite molecular sieves are based on other compositions, such as aluminophosphates, aluminosilicates, and silica. Molecular sieves can have different chemical compositions and different framework structures. Molecular sieves can be microporous or mesoporous and need to be stable in aqueous solutions with a pH less than 6. The acidic functional groups covalently bonded to the inorganic filler can be selected from, but are not limited to, -H2PO3, -R-H2PO3, -SO3H, -R-SO3H, -COOH, -R-COOH, -C6H5OH, -R-C6H5OH, or combinations thereof, where R represents a straight-chain alkyl group, a branched alkyl group, a cycloalkyl group, an organic amino group, an acid-substituted organic amino group, or an aryl group, and the number of carbon atoms in these groups is preferably 1 to 20, more preferably 1 to 10. Inorganic fillers can be in the form of, but are not limited to, particles, beads, sheets, rods, or fibers. The size of the inorganic filler is in the range of 2 nm to 200 μm, or in the range of 10 nm to 100 μm, or in the range of 50 nm to 80 μm. The weight ratio of inorganic filler to water-insoluble ion-conducting polymer in the composite proton-conducting membrane is in the range of 1 / 400 to 40 / 100, or in the range of 1 / 200 to 25 / 100, or in the range of 1 / 100 to 10 / 100.

[0030] In some embodiments, the inorganic filler is aminopropyl-N,N-di(methylphosphonic acid) functionalized silica gel, such as... AMPA, aminopropyl-N,N-di(methylphosphonic acid)-functionalized fumed silica, n-propylphosphonic acid-functionalized silica, p-toluenesulfonic acid-functionalized silica, p-toluenesulfonic acid-functionalized fumed silica, 4-ethylbenzenesulfonic acid-functionalized silica, etc. Tosic acid, 4-ethylbenzenesulfonic acid-functionalized fumed silica, n-propylsulfonic acid-functionalized silica, n-propylsulfonic acid-functionalized fumed silica, or combinations thereof.

[0031] The water-insoluble ion-conducting polymer in the novel composite proton-conducting membrane may be selected from, but is not limited to, perfluorinated ionomers (the perfluorinated ionomers are selected from, but are not limited to, those selected from...). -F、 Crosslinked perfluorinated cation exchange polymers, partially fluorinated cation exchange polymers, crosslinked partially fluorinated cation exchange polymers, nonfluorinated hydrocarbon cation exchange polymers, crosslinked nonfluorinated hydrocarbon cation exchange polymers, or combinations thereof.

[0032] In some implementations, the water-insoluble ion-conducting polymer is -F、 Sulfonated polysulfone, crosslinked sulfonated polysulfone, sulfonated poly(phenylene sulfone), sulfonated phenylenediamine poly(phenylene), sulfonated polystyrene, sulfonated trifluorostyrene-trifluorostyrene copolymer, sulfonated polystyrene-poly(vinylidene fluoride) copolymer, sulfonated polyethersulfone, crosslinked sulfonated polyethersulfone, sulfonated polyether ether ketone, crosslinked sulfonated polyether ether ketone, or combinations thereof.

[0033] The water-insoluble ion-conducting polymer in the novel composite proton-conducting membrane may also be selected from, but is not limited to, water-insoluble hydrophilic polymers or water-insoluble hydrophilic polymer complexes. These water-insoluble hydrophilic polymers or water-insoluble hydrophilic polymer complexes comprise repeating units containing both electrically neutral repeating units and a subset of ionized functional groups, such as –SO3. - –COO - -PO3 2- –PO3H - –C6H4O – Or –O4B – Water-insoluble hydrophilic polymers are insoluble in water but contain highly hydrophilic polar or charged functional groups, such as -SO3. - -COO - -PO3 2- or -PO3H - Group. Water-insoluble hydrophilic polymer complexes comprise water-insoluble hydrophilic polymers complexed with complexing agents (such as polyphosphates, boric acids, metal ions, or mixtures thereof). Water-insoluble hydrophilic ionomers exhibit high stability in aqueous solutions not only due to their insolubility in water, but also due to the polymer's hydrophilicity and ionomer properties, and are resistant to water and charged ions (such as H3O). + or K + It has high affinity, and therefore high ionic conductivity and low film specific surface area resistivity.

[0034] Suitable water-insoluble hydrophilic ion-conducting polymers include, but are not limited to, polysaccharide polymers, cross-linked polysaccharide polymers, metal ion-complexed polysaccharide polymers, acid-complexed polysaccharide polymers, cross-linked polyvinyl alcohol polymers, acid-complexed polyvinyl alcohol polymers, metal ion-complexed polyvinyl alcohol polymers, cross-linked poly(acrylic acid) polymers, metal ion-complexed poly(acrylic acid) polymers, acid-complexed poly(acrylic acid) polymers, cross-linked poly(methacrylic acid), metal ion-complexed poly(methacrylic acid), acid-complexed poly(methacrylic acid), or combinations thereof.

[0035] Various types of polysaccharide polymers may be used, including but not limited to chitosan, sodium alginate, potassium alginate, alginic acid, sodium carrageenan, potassium carrageenan, sodium hyaluronate, potassium hyaluronate, hyaluronic acid, dextran, pullulan, carboxymethyl gel polysaccharide, pectic acid, chitin, chondroitin, xanthan gum, pectic acid, or combinations thereof.

[0036] In some embodiments, the water-insoluble hydrophilic ion-conducting polymer is alginic acid, cross-linked alginic acid, chitosan, cross-linked chitosan, hyaluronic acid, cross-linked hyaluronic acid, or a combination thereof. The cross-linked water-insoluble hydrophilic ion-conducting polymer can be formed via any suitable cross-linking method, such as chemical cross-linking or physical cross-linking, or a combination thereof.

[0037] In some embodiments, the metal ion complexing agent used to form the hydrophilic ion-conducting polymer with metal ion complexes is an iron ion, a ferrous ion, a silver ion, or a vanadium ion.

[0038] The novel composite proton-conducting membrane may comprise a microporous support membrane, on which an inorganic filler and a water-insoluble ion-conducting polymer are coated. The inorganic filler and water-insoluble ion-conducting polymer may also be present within the micropores of the microporous support membrane. The microporous support membrane should possess good thermal stability (stable at least 100°C), high tolerance to aqueous and organic solutions at low pH conditions (e.g., pH less than 6) (insoluble in aqueous and organic solutions), high tolerance to oxidizing and reducing conditions (insoluble and without performance degradation under oxidizing and reducing conditions), high mechanical strength (no dimensional change under system operating conditions), and other factors determined by the operating conditions of electrochemical energy conversion and storage applications (such as water electrolyzers, fuel cells, and redox flow batteries). The microporous support membrane must be chemically compatible with the battery and meet the mechanical requirements of battery stacking or winding assembly operations. Microporous supported membranes have high ionic conductivity, but exhibit low selectivity for charged ions (such as protons, hydrated protons, potassium ions, hydrated potassium ions, sodium ions, hydrated sodium ions, or ammonium ions) compared to electrolytes (such as ferric ions, hydrated ferric ions, ferrous ions, and hydrated ferrous ions).

[0039] Polymers suitable for preparing microporous supported membranes can be selected from, but are not limited to, polyolefins such as polyethylene and polypropylene, polytetrafluoroethylene, fluorinated ethylene propylene, polyvinylidene fluoride, polychlorotrifluoroethylene, nylon 6, nylon 6,6, polyacrylonitrile, polyethersulfone, sulfonated polyethersulfone, polysulfone, sulfonated polysulfone, poly(ether ether ketone), sulfonated poly(ether ether ketone), polyester, cellulose acetate, cellulose triacetate, cellulose, phenolic resins, polybenzimidazole, or combinations thereof. These polymers offer a variety of properties such as, for example, low cost, high stability in water and electrolytes over a wide pH range, good mechanical stability, and ease of processability in membrane fabrication.

[0040] Microporous support membranes can have symmetrical or asymmetrical porous structures. Asymmetrical microporous support membranes can be formed by direct air drying after phase inversion membrane manufacturing methods, or by solvent exchange after phase inversion. Microporous support membranes can also be manufactured by dry processing or wet processing of thermoplastic polyolefins. Dry processing of thermoplastic polyolefins utilizes extrusion to bring the polymer above its melting point and shape it into the desired form. Subsequent annealing and stretching processes can also be performed to increase the crystallinity, orientation, and size of the micropores. Wet processing of polyolefin separators is carried out by mixing hydrocarbon liquids or low molecular weight oils with polymer resins or mixtures of polymer resins and inorganic nanoparticles in a molten phase. The molten mixture is extruded through a die similar to that used in dry processing of separators. The thickness of the microporous support membrane can range from 10 micrometers to 1000 micrometers, or from 10 micrometers to 900 micrometers, or from 10 micrometers to 800 micrometers, or from 10 micrometers to 700 micrometers, or from 10 micrometers to 600 micrometers, or from 10 micrometers to 500 micrometers, or from 20 micrometers to 500 micrometers. The pore size of the microporous membrane can range from 10 nanometers to 50 micrometers, or from 50 nanometers to 10 micrometers, or from 0.2 micrometers to 1 micrometer.

[0041] The coating of inorganic filler and water-insoluble ion-conducting polymer contained on top of the microporous support membrane is a dense, non-porous layer, and its thickness is typically in the range of 1 micrometer to 100 micrometers, or in the range of 5 micrometers to 50 micrometers.

[0042] Another aspect of the present invention is a method for preparing a composite proton-conducting membrane. In one embodiment, the method includes the following steps: a) preparing a dispersion of a water-insoluble ion-conducting polymer in water, an organic solvent, or a water / organic solvent mixture; b) preparing a mixed dispersion comprising the water-insoluble ion-conducting polymer and the inorganic filler by adding an inorganic filler or a dispersion of the inorganic filler in water, an organic solvent, or a water / organic solvent mixture to the dispersion of the water-insoluble ion-conducting polymer under stirring and / or ultrasonication; and c) preparing a composite proton-conducting membrane by casting a layer of the mixed dispersion onto a non-porous substrate (such as a glass plate or a Teflon sheet), subsequently drying the layer of the mixed dispersion, and separating the layer from the substrate to form a dense, non-porous composite proton-conducting membrane.

[0043] In some embodiments, the organic solvent is selected from methanol, ethanol, n-propanol, 2-propanol, acetone, acetic acid, or mixtures thereof.

[0044] In some embodiments, the inorganic filler has covalently bonded acidic functional groups and at least 150 m... 2 / g, or at least 300m 2 / g, or at least 400m 2 / g high surface area.

[0045] In some embodiments, the acidic functional group is selected from -H2PO3, -R-H2PO3, -SO3H, -R-SO3H, -COOH, -R-COOH, -C6H5OH, -R-C6H5OH or combinations thereof, wherein R represents a straight-chain alkyl group, a branched alkyl group, a cycloalkyl group, an organic amino group, an acid-substituted organic amino group, or an aryl group, and the number of carbon atoms in these groups is preferably 1 to 20, more preferably 1 to 10.

[0046] In some embodiments, the inorganic filler is aminopropyl-N,N-di(methylphosphonic acid) functionalized silica gel, such as... AMPA, aminopropyl-N,N-di(methylphosphonic acid)-functionalized fumed silica, n-propylphosphonic acid-functionalized silica, p-toluenesulfonic acid-functionalized silica, p-toluenesulfonic acid-functionalized fumed silica, 4-ethylbenzenesulfonic acid-functionalized silica, etc. Methylbenzenesulfonic acid, 4-ethylbenzenesulfonic acid-functionalized fumed silica, n-propylsulfonic acid-functionalized silica, n-propylsulfonic acid-functionalized fumed silica, or combinations thereof.

[0047] In some embodiments, the water-insoluble ion-conducting polymer is selected from perfluorinated ionomers, cross-linked perfluorinated cation exchange polymers, partially fluorinated cation exchange polymers, cross-linked partially fluorinated cation exchange polymers, nonfluorinated hydrocarbon cation exchange polymers, cross-linked nonfluorinated hydrocarbon cation exchange polymers, or combinations thereof.

[0048] In some implementations, the water-insoluble ion-conducting polymer is -F、 Sulfonated polysulfone, crosslinked sulfonated polysulfone, sulfonated poly(phenylene sulfone), sulfonated phenylenediamine poly(phenylene), sulfonated polystyrene, sulfonated trifluorostyrene-trifluorostyrene copolymer, sulfonated polystyrene-poly(vinylidene fluoride) copolymer, sulfonated polyethersulfone, crosslinked sulfonated polyethersulfone, sulfonated polyether ether ketone, crosslinked sulfonated polyether ether ketone, or combinations thereof.

[0049] In some embodiments, the membrane can be dried at a temperature ranging from 40°C to 150°C, or 40°C to 120°C, or 80°C to 110°C for a time ranging from 5 minutes to 72 hours, or 1 hour to 56 hours, or 12 hours to 52 hours, or 10 minutes to 2 hours, or 30 minutes to 1 hour.

[0050] In some embodiments, the thickness of the composite proton conduction membrane is in the range of 5 micrometers to 500 micrometers, or in the range of 20 micrometers to 300 micrometers, or in the range of 20 micrometers to 200 micrometers.

[0051] In some implementations, the inorganic filler is in the form of particles, beads, plates, rods or fibers.

[0052] In some embodiments, the size of the inorganic filler is in the range of 2 nm to 200 μm, or in the range of 10 nm to 100 μm, or in the range of 50 nm to 80 μm.

[0053] In some embodiments, the weight ratio of inorganic filler to water-insoluble ion-conducting polymer in the composite proton-conducting membrane is in the range of 1 / 400 to 40 / 100, or 1 / 200 to 25 / 100, or 1 / 100 to 10 / 100.

[0054] In some embodiments, the concentration of the water-insoluble ion-conducting polymer in the dispersion of the water-insoluble ion-conducting polymer in water, an organic solvent, or a water / organic solvent mixture is in the range of 5% to 35% by weight, or in the range of 10% to 25% by weight. The organic solvent is selected from methanol, ethanol, n-propanol, 2-propanol, acetone, acetic acid, or mixtures thereof. In another embodiment, the method includes the steps of: a) preparing a dispersion of the water-insoluble ion-conducting polymer in water, an organic solvent, or a water / organic solvent mixture; b) preparing a mixed dispersion comprising the water-insoluble ion-conducting polymer and an inorganic filler by adding an inorganic filler or a dispersion of an inorganic filler in water, an organic solvent, or a water / organic solvent mixture to the dispersion of the water-insoluble ion-conducting polymer under stirring and / or ultrasonication; and c) preparing a composite proton-conducting membrane by casting a layer of the mixed dispersion onto a microporous support membrane and subsequently drying a composite proton-conducting membrane comprising a dense, non-porous layer having the inorganic filler and the water-insoluble ion-conducting polymer and a microporous support membrane layer.

[0055] In some embodiments, the inorganic filler has covalently bonded acidic functional groups and at least 150 m... 2 / g, or at least 300m 2 / g, or at least 400m 2 / g high surface area.

[0056] In some embodiments, the acidic functional group is selected from -H2PO3, -R-H2PO3, -SO3H, -R-SO3H, -COOH, -R-COOH, -C6H5OH, -R-C6H5OH or combinations thereof, wherein R represents a straight-chain alkyl group, a branched alkyl group, a cycloalkyl group, an organic amino group, an acid-substituted organic amino group, or an aryl group, and the number of carbon atoms in these groups is preferably 1 to 20, more preferably 1 to 10.

[0057] In some embodiments, the inorganic filler is aminopropyl-N,N-di(methylphosphonic acid) functionalized silica gel, such as... AMPA, aminopropyl-N,N-di(methylphosphonic acid)-functionalized fumed silica, n-propylphosphonic acid-functionalized silica, p-toluenesulfonic acid-functionalized silica, p-toluenesulfonic acid-functionalized fumed silica, 4-ethylbenzenesulfonic acid-functionalized silica, etc. Methylbenzenesulfonic acid, 4-ethylbenzenesulfonic acid-functionalized fumed silica, n-propylsulfonic acid-functionalized silica, n-propylsulfonic acid-functionalized fumed silica, or combinations thereof.

[0058] In some embodiments, the water-insoluble ion-conducting polymer is selected from perfluorinated ionomers, cross-linked perfluorinated cation exchange polymers, partially fluorinated cation exchange polymers, cross-linked partially fluorinated cation exchange polymers, nonfluorinated hydrocarbon cation exchange polymers, cross-linked nonfluorinated hydrocarbon cation exchange polymers, or combinations thereof.

[0059] In some implementations, the water-insoluble ion-conducting polymer is -F、 Sulfonated polysulfone, crosslinked sulfonated polysulfone, sulfonated poly(phenylene sulfone), sulfonated phenylenediamine poly(phenylene), sulfonated polystyrene, sulfonated trifluorostyrene-trifluorostyrene copolymer, sulfonated polystyrene-poly(vinylidene fluoride) copolymer, sulfonated polyethersulfone, crosslinked sulfonated polyethersulfone, sulfonated polyether ether ketone, crosslinked sulfonated polyether ether ketone, or combinations thereof.

[0060] In some embodiments, the microporous support membrane comprises polyethylene, polypropylene, polytetrafluoroethylene, fluorinated ethylene propylene, polyvinylidene fluoride, polychlorotrifluoroethylene, nylon 6, nylon 6,6, polyacrylonitrile, polyethersulfone, sulfonated polyethersulfone, polysulfone, sulfonated polysulfone, poly(ether ether ketone), sulfonated poly(ether ether ketone), polyester, cellulose acetate, cellulose triacetate, cellulose, phenolic resin, polybenzimidazole, or combinations thereof.

[0061] In some embodiments, the membrane can be dried at a temperature ranging from 40°C to 150°C, or 40°C to 120°C, or 80°C to 110°C for a time ranging from 5 minutes to 72 hours, or 1 hour to 56 hours, or 12 hours to 52 hours, or 10 minutes to 2 hours, or 30 minutes to 1 hour.

[0062] In some embodiments, the thickness of the coating layer containing inorganic filler and water-insoluble ion-conducting polymer contained on top of the microporous support membrane is in the range of 1 micrometer to 100 micrometers, or in the range of 5 micrometers to 50 micrometers.

[0063] In some implementations, the inorganic filler is in the form of particles, beads, plates, rods or fibers.

[0064] In some embodiments, the size of the inorganic filler is in the range of 2 nm to 200 μm, or in the range of 10 nm to 100 μm, or in the range of 50 nm to 80 μm.

[0065] In some embodiments, the weight ratio of inorganic filler to water-insoluble ion-conducting polymer in the composite proton-conducting membrane is in the range of 1 / 400 to 40 / 100, or 1 / 200 to 25 / 100, or 1 / 100 to 10 / 100.

[0066] In another embodiment, the method includes the following steps: a) preparing a homogeneous solution of a water-soluble hydrophilic ion-conducting polymer in water or a water / organic solvent mixture; b) preparing a dispersion comprising the water-soluble hydrophilic ion-conducting polymer and dispersed inorganic filler by adding an inorganic filler or a dispersion of inorganic filler in water or a water / organic solvent mixture to the solution of the water-soluble hydrophilic ion-conducting polymer under stirring and / or ultrasonication; c) casting a layer of the dispersion comprising the water-soluble hydrophilic ion-conducting polymer and dispersed inorganic filler onto a microporous support membrane, and subsequently drying the dispersion layer; and d) preparing a composite proton-conducting membrane by converting the water-soluble hydrophilic ion-conducting polymer in the dried coating layer into a water-insoluble ion-conducting polymer to form a composite proton-conducting membrane comprising a dense non-porous layer having inorganic filler and a water-insoluble ion-conducting polymer and a microporous support membrane layer.

[0067] In some embodiments, the inorganic filler has covalently bonded acidic functional groups and at least 150 m... 2 / g, or at least 300m 2 / g, or at least 400m 2 / g high surface area.

[0068] In some embodiments, the acidic functional group is selected from -H2PO3, -R-H2PO3, -SO3H, -R-SO3H, -COOH, -R-COOH, -C6H5OH, -R-C6H5OH or combinations thereof, wherein R represents a straight-chain alkyl group, a branched alkyl group, a cycloalkyl group, an organic amino group, an acid-substituted organic amino group, or an aryl group, and the number of carbon atoms in these groups is preferably 1 to 20, more preferably 1 to 10.

[0069] In some embodiments, the inorganic filler is aminopropyl-N,N-di(methylphosphonic acid) functionalized silica gel, such as... AMPA, aminopropyl-N,N-di(methylphosphonic acid)-functionalized fumed silica, n-propylphosphonic acid-functionalized silica, p-toluenesulfonic acid-functionalized silica, p-toluenesulfonic acid-functionalized fumed silica, 4-ethylbenzenesulfonic acid-functionalized silica, etc. Methylbenzenesulfonic acid, 4-ethylbenzenesulfonic acid-functionalized fumed silica, n-propylsulfonic acid-functionalized silica, n-propylsulfonic acid-functionalized fumed silica, or combinations thereof.

[0070] In some embodiments, the water-soluble hydrophilic ion-conducting polymer comprises polysaccharides, polyvinyl alcohol, poly(acrylic acid), poly(meth)acrylic acid, or combinations thereof.

[0071] In some embodiments, the polysaccharide polymer includes chitosan, sodium alginate, potassium alginate, alginic acid, sodium carrageenan, potassium carrageenan, sodium hyaluronate, potassium hyaluronate, hyaluronic acid, dextran, pullulan, carboxymethyl gelatin, pectic acid, chitin, chondroitin, xanthan gum, pectic acid, or combinations thereof.

[0072] In some embodiments, the microporous support membrane comprises polyethylene, polypropylene, polytetrafluoroethylene, fluorinated ethylene propylene, polyvinylidene fluoride, polychlorotrifluoroethylene, nylon 6, nylon 6,6, polyacrylonitrile, polyethersulfone, sulfonated polyethersulfone, polysulfone, sulfonated polysulfone, poly(ether ether ketone), sulfonated poly(ether ether ketone), polyester, cellulose acetate, cellulose triacetate, cellulose, phenolic resin, polybenzimidazole, or combinations thereof.

[0073] In some embodiments, the membrane can be dried at a temperature ranging from 40°C to 150°C, or 40°C to 120°C, or 55°C to 65°C for a time ranging from 5 minutes to 24 hours, or 5 minutes to 5 hours, or 5 minutes to 3 hours, or 10 minutes to 2 hours, or 30 minutes to 1 hour.

[0074] In some embodiments, the thickness of the coating layer containing inorganic filler and water-insoluble ion-conducting polymer contained on top of the microporous support membrane is in the range of 1 micrometer to 100 micrometers, or in the range of 5 micrometers to 50 micrometers.

[0075] In some implementations, the inorganic filler is in the form of particles, beads, plates, rods or fibers.

[0076] In some embodiments, the size of the inorganic filler is in the range of 2 nm to 200 μm, or in the range of 10 nm to 100 μm, or in the range of 50 nm to 80 μm.

[0077] In some embodiments, the weight ratio of inorganic filler to water-insoluble ion-conducting polymer in the composite proton-conducting membrane is in the range of 1 / 400 to 40 / 100, or 1 / 200 to 25 / 100, or 1 / 100 to 10 / 100.

[0078] In some implementations, the water-soluble hydrophilic ion-conducting polymer is converted into a water-insoluble ion-conducting polymer by using a complexing agent to complex the water-soluble hydrophilic ion-conducting polymer.

[0079] In some implementations, the complexing agent is selected from polyphosphates, boric acids, metal ions, or combinations thereof.

[0080] In some embodiments, the metal ion complexing agent used to form the hydrophilic ion-conducting polymer with metal ion complexes is an iron ion, a ferrous ion, a silver ion, or a vanadium ion.

[0081] In some implementations, a water-soluble hydrophilic ion-conducting polymer is converted into a water-insoluble ion-conducting polymer by radiation crosslinking of a water-soluble hydrophilic polymer.

[0082] In some implementations, the water-soluble hydrophilic ion-conducting polymer is chemically crosslinked using a chemical crosslinking agent, thereby converting the water-soluble hydrophilic ion-conducting polymer into a water-insoluble ion-conducting polymer.

[0083] In some embodiments, the chemical crosslinking agent is selected from glyoxal, glutaraldehyde, sulfosuccinic acid, ethylene glycol diglycidyl ether, 1,6-hexamethylene diisocyanate, divinyl sulfone, or combinations thereof.

[0084] In some embodiments, the homogeneous solution of the water-soluble ion-conducting polymer contains acetic acid or other inorganic or organic acids.

[0085] In some embodiments, a water-soluble hydrophilic ion-conducting polymer is converted into a water-insoluble hydrophilic ion-conducting polymer by immersing a dried membrane in an aqueous solution of polyphosphate, boric acid, metal salt, hydrochloric acid, or a combination thereof.

[0086] In some embodiments, the water-soluble hydrophilic ion-conducting polymer on the membrane is immersed in an aqueous solution of polyphosphate, boric acid, metal salt, hydrochloric acid, or combinations thereof for a period of time ranging from 5 minutes to 24 hours, or 5 minutes to 12 hours, or 5 minutes to 8 hours, or 10 minutes to 5 hours, or 30 minutes to 1 hour.

[0087] In other embodiments, the water-soluble hydrophilic ion-conducting polymer is in situ complexed with a complexing agent in the negative electrode electrolyte, positive electrode electrolyte, or both negative and positive electrode electrolytes in the redox flow battery cell.

[0088] Another aspect of the present invention is a redox flow battery system. In one embodiment, the redox flow battery system includes: at least one rechargeable battery, the at least one rechargeable battery including a positive electrode electrolyte, a negative electrode electrolyte, and a composite proton conduction membrane positioned between the positive electrode electrolyte and the negative electrode electrolyte, the positive electrode electrolyte being in contact with the positive electrode, and the negative electrode electrolyte being in contact with the negative electrode; wherein the composite proton conduction membrane contains acidic functional groups having covalent bonds and at least 150 μm 2 / g of high surface area inorganic filler, water-insoluble ion-conducting polymer and optionally microporous support membrane.

[0089] In some embodiments, the acidic functional groups covalently bonded to the inorganic filler are selected from -H2PO3, -R-H2PO3, -SO3H, -R-SO3H, -COOH, -R-COOH, -C6H5OH, -R-C6H5OH, or combinations thereof, wherein R represents a straight-chain alkyl group, a branched alkyl group, a cycloalkyl group, an organic amino group, an acid-substituted organic amino group, or an aryl group, and the number of carbon atoms in these groups is preferably 1 to 20, more preferably 1 to 10.

[0090] In some embodiments, the inorganic filler is aminopropyl-N,N-di(methylphosphonic acid) functionalized silica gel, such as... AMPA, aminopropyl-N,N-di(methylphosphonic acid)-functionalized fumed silica, n-propylphosphonic acid-functionalized silica, p-toluenesulfonic acid-functionalized silica, p-toluenesulfonic acid-functionalized fumed silica, 4-ethylbenzenesulfonic acid-functionalized silica, etc. Methylbenzenesulfonic acid, 4-ethylbenzenesulfonic acid-functionalized fumed silica, n-propylsulfonic acid-functionalized silica, n-propylsulfonic acid-functionalized fumed silica, or combinations thereof.

[0091] In some embodiments, the water-insoluble ion-conducting polymer is a perfluorinated ionomer, a cross-linked perfluorinated cation exchange polymer, a partially fluorinated cation exchange polymer, a cross-linked partially fluorinated cation exchange polymer, a nonfluorinated hydrocarbon cation exchange polymer, a cross-linked nonfluorinated hydrocarbon cation exchange polymer, or a combination thereof.

[0092] In some implementations, the water-insoluble ion-conducting polymer is -F、 Sulfonated polysulfone, crosslinked sulfonated polysulfone, sulfonated poly(phenylene sulfone), sulfonated phenylenediamine poly(phenylene), sulfonated polystyrene, sulfonated trifluorostyrene-trifluorostyrene copolymer, sulfonated polystyrene-poly(vinylidene fluoride) copolymer, sulfonated polyethersulfone, crosslinked sulfonated polyethersulfone, sulfonated polyether ether ketone, crosslinked sulfonated polyether ether ketone, or combinations thereof.

[0093] In some embodiments, the water-insoluble ion-conducting polymer is a polysaccharide polymer, a cross-linked polysaccharide polymer, a metal ion-complexed polysaccharide polymer, an acid-complexed polysaccharide polymer, a cross-linked polyvinyl alcohol polymer, an acid-complexed polyvinyl alcohol polymer, a metal ion-complexed polyvinyl alcohol polymer, a cross-linked poly(acrylic acid) polymer, a metal ion-complexed poly(acrylic acid) polymer, an acid-complexed poly(acrylic acid) polymer, a cross-linked poly(methacrylic acid), a metal ion-complexed poly(methacrylic acid), an acid-complexed poly(methacrylic acid), or a combination thereof.

[0094] In some embodiments, the water-insoluble ion-conducting polymer is alginic acid, cross-linked alginic acid, chitosan, cross-linked chitosan, hyaluronic acid, cross-linked hyaluronic acid, or a combination thereof.

[0095] In some embodiments, the microporous support membrane comprises polyethylene, polypropylene, polytetrafluoroethylene, fluorinated ethylene propylene, polyvinylidene fluoride, polychlorotrifluoroethylene, nylon 6, nylon 6,6, polyacrylonitrile, polyethersulfone, sulfonated polyethersulfone, polysulfone, sulfonated polysulfone, poly(ether ether ketone), sulfonated poly(ether ether ketone), polyester, cellulose acetate, cellulose triacetate, cellulose, phenolic resin, polybenzimidazole, or combinations thereof.

[0096] In some embodiments, the negative electrode electrolyte, the positive electrode electrolyte, or both the negative electrode electrolyte and the positive electrode electrolyte contain a boric acid additive that can complex with the ion-conducting polymer on the composite proton-conducting membrane.

[0097] In some implementations, the negative electrode electrolyte, the positive electrode electrolyte, or both the negative electrode electrolyte and the positive electrode electrolyte contain ferrous chloride.

[0098] In some implementations, the negative electrode electrolyte, the positive electrode electrolyte, or both the negative electrode electrolyte and the positive electrode electrolyte contain a supporting electrolyte.

[0099] In some implementations, the supporting electrolyte is selected from ammonium chloride, potassium chloride, sodium chloride, or combinations thereof.

[0100] In some implementations, the positive electrode electrolyte comprises ferrous chloride, a supporting electrolyte, and hydrochloric acid.

[0101] In some implementations, the negative electrode electrolyte, the positive electrode electrolyte, or both the negative electrode electrolyte and the positive electrode electrolyte contain glycine.

[0102] In some implementations, the water-insoluble ion-conducting polymer is formed in situ by complexing the water-soluble ion-conducting polymer with a complexing agent of the negative electrolyte, the positive electrolyte, or both the negative and positive electrolytes.

[0103] Another aspect of the present invention is a membrane electrode assembly. In one embodiment, the membrane electrode assembly includes: a composite proton-conducting membrane; an anode comprising an anode catalyst on one surface of the composite proton-conducting membrane; an anode gas diffusion layer; a cathode comprising a cathode catalyst on another surface of the composite proton-conducting membrane; and a cathode gas diffusion layer; wherein the composite proton-conducting membrane comprises acidic functional groups having covalent bonds and at least 150 μm 2 / g of high surface area inorganic filler, water-insoluble ion-conducting polymer and optionally microporous support membrane.

[0104] In some embodiments, the acidic functional groups covalently bonded to the inorganic filler are selected from -H2PO3, -R-H2PO3, -SO3H, -R-SO3H, -COOH, -R-COOH, -C6H5OH, -R-C6H5OH, or combinations thereof, wherein R represents a straight-chain alkyl group, a branched alkyl group, a cycloalkyl group, an organic amino group, an acid-substituted organic amino group, or an aryl group, and the number of carbon atoms in these groups is preferably 1 to 20, more preferably 1 to 10.

[0105] In some embodiments, the inorganic filler is aminopropyl-N,N-di(methylphosphonic acid) functionalized silica gel, such as... AMPA, aminopropyl-N,N-di(methylphosphonic acid)-functionalized fumed silica, n-propylphosphonic acid-functionalized silica, p-toluenesulfonic acid-functionalized silica, p-toluenesulfonic acid-functionalized fumed silica, 4-ethylbenzenesulfonic acid-functionalized silica, etc. Methylbenzenesulfonic acid, 4-ethylbenzenesulfonic acid-functionalized fumed silica, n-propylsulfonic acid-functionalized silica, n-propylsulfonic acid-functionalized fumed silica, or combinations thereof.

[0106] In some embodiments, the water-insoluble ion-conducting polymer is a perfluorinated ionomer, a cross-linked perfluorinated cation exchange polymer, a partially fluorinated cation exchange polymer, a cross-linked partially fluorinated cation exchange polymer, a nonfluorinated hydrocarbon cation exchange polymer, a cross-linked nonfluorinated hydrocarbon cation exchange polymer, or a combination thereof.

[0107] In some implementations, the water-insoluble ion-conducting polymer is -F、 Sulfonated polysulfone, crosslinked sulfonated polysulfone, sulfonated poly(phenylene sulfone), sulfonated phenylenediamine poly(phenylene), sulfonated polystyrene, sulfonated trifluorostyrene-trifluorostyrene copolymer, sulfonated polystyrene-poly(vinylidene fluoride) copolymer, sulfonated polyethersulfone, crosslinked sulfonated polyethersulfone, sulfonated polyether ether ketone, crosslinked sulfonated polyether ether ketone, or combinations thereof.

[0108] In some embodiments, the water-insoluble ion-conducting polymer is a polysaccharide polymer, a cross-linked polysaccharide polymer, a metal ion-complexed polysaccharide polymer, an acid-complexed polysaccharide polymer, a cross-linked polyvinyl alcohol polymer, an acid-complexed polyvinyl alcohol polymer, a metal ion-complexed polyvinyl alcohol polymer, a cross-linked poly(acrylic acid) polymer, a metal ion-complexed poly(acrylic acid) polymer, an acid-complexed poly(acrylic acid) polymer, a cross-linked poly(methacrylic acid), a metal ion-complexed poly(methacrylic acid), an acid-complexed poly(methacrylic acid), or a combination thereof.

[0109] In some embodiments, the water-insoluble ion-conducting polymer is alginic acid, cross-linked alginic acid, chitosan, cross-linked chitosan, hyaluronic acid, cross-linked hyaluronic acid, or a combination thereof.

[0110] In some embodiments, the microporous support membrane comprises polyethylene, polypropylene, polytetrafluoroethylene, fluorinated ethylene propylene, polyvinylidene fluoride, polychlorotrifluoroethylene, nylon 6, nylon 6,6, polyacrylonitrile, polyethersulfone, sulfonated polyethersulfone, polysulfone, sulfonated polysulfone, poly(ether ether ketone), sulfonated poly(ether ether ketone), polyester, cellulose acetate, cellulose triacetate, cellulose, phenolic resin, polybenzimidazole, or combinations thereof.

[0111] In some implementations, the anode catalyst comprises metallic iridium, iridium oxide, a bimetallic oxide of iridium and a non-noble metal, or a combination thereof.

[0112] In some embodiments, the anode catalyst comprises metallic iridium, iridium oxide, iridium-ruthenium alloy, iridium-ruthenium oxide alloy, or a combination thereof.

[0113] In some implementations, the cathode catalyst comprises platinum metal, platinum oxide, or a combination thereof.

[0114] In some implementations, the anode catalyst and cathode catalyst comprise proton-conducting ionomers.

[0115] In some embodiments, the proton-conducting ionomer is selected from perfluorinated ionomers, partially fluorinated cation exchange polymers, nonfluorinated hydrocarbon cation exchange polymers, or combinations thereof.

[0116] In some implementations, the water-insoluble ion-conducting polymer is -F、 Sulfonated polysulfone, crosslinked sulfonated polysulfone, sulfonated poly(phenylene sulfone), sulfonated phenylenediamine poly(phenylene), sulfonated polystyrene, sulfonated trifluorostyrene-trifluorostyrene copolymer, sulfonated polystyrene-poly(vinylidene fluoride) copolymer, sulfonated polyethersulfone, crosslinked sulfonated polyethersulfone, sulfonated polyether ether ketone, crosslinked sulfonated polyether ether ketone, or combinations thereof.

[0117] In some embodiments, the anode and cathode catalysts comprise inorganic fillers having covalently bonded acidic functional groups and at least 150 m... 2 / g, or at least 300m 2 / g, or at least 400m 2 / g high surface area.

[0118] Example

[0119] The following embodiments are provided to illustrate one or more embodiments of the present invention, but the invention is not limited to the specific embodiments described. Many variations can be made to the following embodiments that fall within the scope of the invention.

[0120] Comparative Example 1: Alginic Acid Membrane (abbreviated as) Preparation

[0121] A 6.5 wt% sodium alginate aqueous solution was prepared by dissolving a sodium alginate polymer in deionized water. The solution was purchased from Daramic, LLC. A thin layer of 6.5 wt% sodium alginate aqueous solution was coated on one surface of a 175 microporous support membrane and dried in an oven at 60°C for 2 hours to achieve the desired effect. A thin, non-porous sodium alginate layer with a thickness of 15 micrometers is formed on the surface of the support membrane. The dried membrane is then treated with a 1.0M hydrochloric acid aqueous solution for 30 minutes to convert the water-soluble sodium alginate coating into a water-insoluble alginate coating.

[0122] Example 1: AMPA-Alginic Acid Composite membrane (abbreviated as AMPA-) SiO2- Preparation of )

[0123] A solution with a molecular weight of 480m was prepared by adding 0.5g AMPA-SiO2 and 10.0g sodium alginate to 150.0mL deionized water and stirring the mixture for 8 hours. 2 / g-550mm 2 / g of high surface area aminopropyl-N,N-bis(methylphosphonic acid) functionalized silica gel (purchased from Silicycle) AMPA (abbreviated as AMPA-SiO2) and sodium alginate dispersion in water. Purchased from Deremics Ltd. A thin layer of dispersion was coated on one surface of the 175 microporous support membrane and dried in an oven at 60°C for 2 hours to obtain the desired microporous structure. A thin, non-porous layer containing AMPA-SiO2 and sodium alginate, with a thickness of 15 micrometers, is formed on the surface of the support membrane. The dried membrane is then treated with a 1.0M hydrochloric acid aqueous solution for 30 minutes to convert the water-soluble sodium alginate coating into water-insoluble alginic acid.

[0124] Example 2: Analysis of AA / Daramic and AMPA-SiO2- Membrane-based all-iron redox flow battery Performance Study

[0125] The AA / Daramic membrane prepared in Comparative Example 1 and the AMPA-SiO2- membrane prepared in Example 1 The ionic conductivity, battery charge / discharge cycle life, VE, CE, and EE of the composite membrane were measured using EIS with a BCS-810 battery cycling system (Biologic, France) at room temperature, and the results are shown in Table 1. As can be seen from Table 1, the novel AMPA-SiO2-containing inorganic filler... The membrane exhibits lower areal resistivity, longer battery cycles, higher CE, and higher EE than AA / Daramic membranes without AMPA-SiO2 inorganic filler.

[0126] Table 1. AA / Daramic and AMPA-SiO2- membrane a All-iron redox flow battery performance

[0127]

[0128] aNegative electrode electrolyte solution: 1.5M FeCl2, 3.5M NH4Cl, 0.2M boric acid; Positive electrode electrolyte solution: 1.5M FeCl2, 3.5M NH4Cl, 0.4M HCl; Charging current density: 30mA / cm² 2 Charging time: 4 hours; Discharge current density: 30mA / cm³ 2 Discharge time: 4 hours; Number of cycles is counted when ≥70% CE.

[0129] Example 3: Composite membrane (abbreviated as AMPA-) ) Preparation

[0130] In order to prepare AMPA- Composite membrane, formed by adding AMPA-SiO2 under ultrasonication and stirring. In dispersion D2021 (1100 EW, 20 wt% in alcohol), a mixture containing 480 m 2 / g-550mm 2 / g of high surface area aminopropyl-N,N-di(methylphosphonic acid) functionalized silica gel (purchased from Silicycle) AMPA (abbreviated as AMPA-SiO2) and The dispersion of AMPA-SiO2 with The polymer weight ratio was 1:20. The dispersion was cast onto a clean glass plate using a casting tool and dried on a hot plate at 30°C for 12 hours to form AMPA. A membrane was formed, thus creating a thin-layer dispersion. The membrane was further dried at 80°C for 9 hours. The dried membrane was then peeled off the glass plate and further heated at 100°C for 9 hours. The final membrane thickness was 60 μm.

[0131] Example 4: Methylbenzenesulfonic acid / Composite membrane (abbreviated as TA-) ) Preparation

[0132] In order to prepare TA- Composite membrane, formed by adding TA-SiO2 under ultrasonication and stirring. In dispersion D2021 (1100 EW, 20 wt% in alcohol), 4-ethylbenzenesulfonic acid-functionalized silica (purchased from Silicycle) was prepared. Methylbenzenesulfonic acid (abbreviated as TA-SiO2) and The dispersion of TA-SiO2 and... The polymer weight ratio was 1:20. The dispersion was cast onto a clean glass plate using a casting tool and dried on a hot plate at 30°C for 12 hours to form TA-. A membrane was formed, thus creating a thin-layer dispersion. The membrane was further dried at 80°C for 9 hours. The dried membrane was then peeled off the glass plate and further heated at 100°C for 9 hours. The final membrane thickness was 60 μm.

[0133] Example 5: AMPA-containing formulation for water electrolysis Composite membrane (abbreviated as 5AMPA-D2021) Fabrication of membrane electrode assembly (MEA)

[0134] An APA-containing catalyst was prepared by coating a catalyst onto a gas diffusion layer (CCG), using an IrO2 oxygen evolution reaction (OER) catalyst for the anode and a Pt / C hydrogen evolution reaction (HER) catalyst for the cathode. The 5AMPA-D2021MEA composite membrane. This was achieved by mixing the catalyst in deionized water and alcohol. An ionomer (5% by weight in alcohol) was used to prepare a catalyst ink for spraying. The mixture was finely dispersed in an ultrasonic bath. [The following appears to be unrelated and possibly a separate sentence fragment:] Anode and cathode... The content of ionomers was controlled to be that of catalyst and The total ionomer content is 30% by weight. Pt / C ink is sprayed onto carbon paper used as the cathode gas diffusion layer. The Pt loading is 0.3 mg / cm³. 2 IrO2 ink was sprayed onto a Pt-Ti felt used as the anode gas diffusion layer. The IrO2 loading was 1.0 mg / cm³. 2 AMPA- The composite membrane is sandwiched between two catalyst-coated gas diffusion layers. A test cell is then installed using a 5AMPA-D2021 MEA.

[0135] Comparative Example 2: A product used in water electrolysis containing... 212 commercial membrane (abbreviated as) 212) membrane electrode Fabrication of Components (MEAs)

[0136] The catalyst containing [a specific component] was prepared by coating a catalyst onto a gas diffusion layer (CCG) using the same method as used in Example 5. 212 commercial membrane 212MEA, the difference lies in the use of 212 commercial membrane as a replacement for AMPA Composite membrane.

[0137] Example 6: Using 5AMPA-D2021 MEA and Water electrolysis performance evaluation of 212MEA

[0138] The 5AMPA-D2021 MEA was evaluated using a PEM water electrolysis test station (Scribner 600 electrolyzer test system) and... 212MEA were applied to an active membrane with an area of ​​5 cm². 2 The water electrolysis performance in a single-cell electrolyzer was evaluated. The test station included an integrated power supply, a voltage regulator, an impedance analyzer for electrochemical impedance spectroscopy (EIS) and high-frequency resistance (HFR), and real-time sensors for product flow rate and permeation monitoring. Tests were conducted at 80-100°C and atmospheric pressure. Ultrapure water was supplied to the anode of the MEA at a flow rate of 100 mL / min. The cell underwent a preconditioning process prior to testing. The cell was heated to 60°C and subjected to 200 mA / cm². 2 Maintain for 1 hour at 1A / cm 2 Maintain for 1 hour, then maintain at 1.7V for 4 hours. Then heat the battery to 80°C and at 200mA / cm. 2 Keep for 1 hour and at 1A / cm 2 Hold for 1 hour. These steps together constitute one conditioning cycle. After conditioning, plot the polarization curve (hold each data point for 1 minute at the end). After two conditioning cycles, the polarization results are shown below. Figure 1 In the middle. 5AMPA-D2021 MEA shows a difference compared to The lower polarization voltage of the 212MEA indicates the inclusion of a novel AMPA- The 5AMPA-D2021MEA composite membrane has better performance than commercially available membranes. 212 film 212MEA has higher proton conductivity. Figure 1 The 5AMPA-D2021 and Water electrolysis performance of 212MEA at 80℃ and atmospheric pressure.

[0139] From a thermodynamic and kinetic perspective, water electrolyzers offer advantages when operating at higher temperatures. For example... Figure 2 As shown, the polarization voltage of the 5AMPA-D2021 MEA decreases as the operating temperature increases from 80°C to 100°C. At 100°C, the current density of the water electrolyzer containing the 5AMPA-D2021 MEA reaches 2.7 A / cm² at a polarization voltage of 1.75 V. 2 . Figure 2 The effect of temperature on the water electrolysis performance of 5AMPA-D2021 MEA is shown.

[0140] Example 7: AMPA containing catalyst-coated Composite membrane (abbreviated as 5AMPA-D2021-) C) Fabrication of the membrane electrode assembly (MEA)

[0141] By coating a catalyst onto a membrane, using an IrO2 oxygen evolution reaction (OER) catalyst for the anode and a Pt / C hydrogen evolution reaction (HER) catalyst for the cathode, AMPA- is prepared. The 5AMPA-D2021-C MEA composite membrane. This was achieved by mixing the catalyst in deionized water and alcohol. An ionomer (5% by weight in alcohol) was used to prepare a catalyst ink for spraying. The mixture was finely dispersed in an ultrasonic bath. [The following appears to be unrelated and possibly a separate sentence fragment:] Anode and cathode... The content of ionomers was controlled to be that of catalyst and 30% by weight of total ionomer content. Pt / C ink is sprayed onto pretreated AMPA- On one surface of the composite membrane, the Pt loading is 0.3 mg / cm³. 2 IrO2 ink is sprayed onto pretreated AMPA- On the other surface of the composite membrane, the IrO2 loading is 1.0 mg / cm³. 2 The catalyst-coated AMPA- The composite membrane is sandwiched between carbon paper, which serves as the cathode gas diffusion layer, and Pt-Ti felt, which serves as the anode gas diffusion layer, to form 5AMPA-D2021-C MEA.

[0142] Specific implementation plan

[0143] While the following description is presented in conjunction with specific embodiments, it should be understood that the description is intended to illustrate, and not limit, the scope of the foregoing description and the appended claims.

[0144] The first embodiment of the present invention is a composite proton-conducting membrane, which comprises: an inorganic filler having covalently bonded acidic functional groups and at least 150 μm 2 / g high surface area; and water-insoluble ion-conducting polymer. Embodiments of the present invention are one, any, or all of the embodiments described in the preceding embodiments to the first embodiment described in this paragraph, and further include a microporous support membrane. Embodiments of the present invention are one, any, or all of the embodiments described in the preceding embodiments to the first embodiment described in this paragraph, wherein the inorganic filler is selected from silica gel, precipitated silica, fumed silica, colloidal silica, alumina, silica-alumina, zirconium oxide, molecular sieves, metal-organic frameworks, zeolite imidazole salt frameworks, covalent organic frameworks, or combinations thereof, wherein the inorganic filler comprises covalently bonded acidic functional groups. The embodiments of the present invention are one, any one, or all of the embodiments described in the preceding embodiments to the first embodiment described in this paragraph, wherein the acidic functional group is selected from -H2PO3, -R-H2PO3, -SO3H, -R-SO3H, -COOH, -R-COOH, -C6H5OH, -R-C6H5OH, or combinations thereof, wherein R represents a straight-chain alkyl group, a branched alkyl group, a cycloalkyl group, an organic amino group, an acid-substituted organic amino group, or an aryl group, and the number of carbon atoms in these groups is in the range of 1 to 20. The embodiments of the present invention are one, any one, or all of the embodiments described in the preceding embodiments to the first embodiment described in this paragraph, wherein the inorganic filler is selected from aminopropyl-N,N-di(methylphosphonic acid) functionalized silica, aminopropyl-N,N-di(methylphosphonic acid) functionalized fumed silica, n-propylphosphonic acid functionalized silica, n-propylphosphonic acid functionalized fumed silica, p-toluenesulfonic acid functionalized silica, p-toluenesulfonic acid functionalized fumed silica, 4-ethylbenzenesulfonic acid functionalized silica, 4-ethylbenzenesulfonic acid functionalized fumed silica, n-propylsulfonic acid functionalized silica, n-propylsulfonic acid functionalized fumed silica, or combinations thereof. The embodiments of the present invention are any one or all of the embodiments described in the preceding embodiments to the first embodiment described in this paragraph, wherein the water-insoluble ion-conducting polymer is selected from perfluorinated cation exchange polymers, cross-linked perfluorinated cation exchange polymers, partially fluorinated cation exchange polymers, cross-linked partially fluorinated cation exchange polymers, nonfluorinated hydrocarbon cation exchange polymers, cross-linked nonfluorinated hydrocarbon cation exchange polymers, or combinations thereof. The embodiments of the present invention are any one or all of the embodiments described in the preceding embodiments to the first embodiment described in this paragraph, wherein the water-insoluble ion-conducting polymer is a water-insoluble hydrophilic polymer or a water-insoluble hydrophilic polymer complex, which comprises repeating units of both electrically neutral repeating units and a subset of ionized functional groups, the ionized functional groups being such as –SO3. - –COO - -PO3 2- –PO3H -–C6H4O – Or –O4B –The embodiments of the present invention are one, any, or all of the embodiments described in the preceding embodiments to the first embodiment described in this paragraph, wherein the water-insoluble hydrophilic polymer complex comprises a water-insoluble hydrophilic polymer complexed with a complexing agent selected from polyphosphoric acid, boric acid, metal ions, or mixtures thereof. The embodiments of the present invention are one, any, or all of the embodiments described in the preceding embodiments to the first embodiment described in this paragraph, wherein the water-insoluble ion-conducting polymer is selected from polysaccharide polymers, cross-linked polysaccharide polymers, metal ion-complexed polysaccharide polymers, acid-complexed polysaccharide polymers, cross-linked polyvinyl alcohol polymers, acid-complexed polyvinyl alcohol polymers, metal ion-complexed polyvinyl alcohol polymers, cross-linked poly(acrylic acid) polymers, metal ion-complexed poly(acrylic acid) polymers, acid-complexed poly(acrylic acid) polymers, cross-linked poly(methacrylic acid), metal ion-complexed poly(methacrylic acid), acid-complexed poly(methacrylic acid), or combinations thereof. The embodiments of the present invention are one, any one, or all of the embodiments described in the preceding embodiments to the first embodiment described in this paragraph, wherein the polysaccharide polymer is selected from alginic acid, cross-linked alginic acid, chitosan, cross-linked chitosan, hyaluronic acid, cross-linked hyaluronic acid, or combinations thereof. The embodiments of the present invention are one, any one, or all of the embodiments described in the preceding embodiments to the first embodiment described in this paragraph, wherein the metal ion complexing agent used to form the hydrophilic ion-conducting polymer with metal ion complexation is ferric ion, ferrous ion, silver ion, or vanadium ion. Embodiments of the present invention are any one or all of the embodiments described in the preceding embodiments to the first embodiment described in this paragraph, wherein the microporous support membrane is prepared from a polymer selected from: polyethylene, polypropylene, polytetrafluoroethylene, fluorinated ethylene propylene, polyvinylidene fluoride, polychlorotrifluoroethylene, polycaprolactam, a polymer prepared from hexamethylenediamine and adipic acid, polyacrylonitrile, polyethersulfone, sulfonated polyethersulfone, polysulfone, sulfonated polysulfone, poly(ether ether ketone), sulfonated poly(ether ether ketone), polyester, cellulose acetate, cellulose triacetate, cellulose, phenolic resin, polybenzimidazole, or combinations thereof. Embodiments of the present invention are any one or all of the embodiments described in the preceding embodiments to the first embodiment described in this paragraph, wherein the microporous support membrane has a thickness of 10 micrometers to 1000 micrometers and contains pores with a pore size ranging from 10 nanometers to 50 micrometers. Embodiments of the present invention are any one or all of the embodiments described in the preceding embodiments to the first embodiment described in this paragraph, wherein the microporous support membrane is coated with a coating layer comprising an inorganic filler and a water-insoluble ion-conducting polymer, and wherein the coating layer has a thickness of 1 micrometer to 100 micrometers. Embodiments of the present invention are any one or all of the embodiments described in the preceding embodiments to the first embodiment described in this paragraph, wherein the inorganic filler is in the form of particles, beads, sheets, rods, or fibers and has a size of 2 nm to 80 μm.The embodiments of the present invention are one, any one, or all of the embodiments from the previous embodiments to the first embodiment in this paragraph, wherein the weight ratio of inorganic filler to water-insoluble ion-conducting polymer in the composite proton-conducting membrane is in the range of 1 / 400 to 40 / 100.

[0145] A second embodiment of the present invention is a method for preparing a composite proton-conducting membrane, the method comprising: preparing a dispersion of a water-insoluble ion-conducting polymer in water, an organic solvent, or a water / organic solvent mixture; and preparing a mixed dispersion comprising the water-insoluble ion-conducting polymer and an inorganic filler by adding an inorganic filler or a dispersion of an inorganic filler in water, an organic solvent, or a water / organic solvent mixture to the dispersion of the water-insoluble ion-conducting polymer under stirring and / or ultrasonication, wherein the inorganic filler has covalently bonded acidic functional groups and at least 150 μm 2 The composite proton-conducting membrane is prepared by casting a layer of the mixed dispersion onto a non-porous substrate or a microporous support membrane and then drying it.

[0146] A third embodiment of the present invention is a redox flow battery system comprising at least one rechargeable battery, the at least one rechargeable battery comprising a positive electrolyte, a negative electrolyte and the aforementioned composite proton conduction membrane, wherein the composite proton conduction membrane is positioned between the positive electrolyte and the negative electrolyte, the positive electrolyte being in contact with the positive electrode and the negative electrolyte being in contact with the negative electrode.

[0147] A fourth embodiment of the present invention is a membrane electrode assembly, which includes:

[0148] The aforementioned composite proton-conducting membrane; an anode comprising an anode catalyst on one surface of the composite proton-conducting membrane;

[0149] Anode gas diffusion layer; cathode, which contains a cathode catalyst on another surface of the composite proton-conducting membrane; and

[0150] Cathode gas diffusion layer; wherein the composite proton conduction membrane comprises:

[0151] Inorganic packing material having covalently bonded acidic functional groups and at least 150 m 2 High surface area per g; and water-insoluble ion-conducting polymer.

Claims

1. A composite proton conduction membrane, the composite proton conduction membrane comprising: Inorganic filler, wherein the inorganic filler has covalently bonded acidic functional groups and at least 150 m 2 / g high surface area; and Water-insoluble ion-conducting polymers; The inorganic filler is aminopropyl-N,N-di(methylphosphonic acid)-functionalized silica, aminopropyl-N,N-di(methylphosphonic acid)-functionalized fumed silica, n-propylphosphonic acid-functionalized silica, n-propylphosphonic acid-functionalized fumed silica, p-toluenesulfonic acid-functionalized silica, p-toluenesulfonic acid-functionalized fumed silica, 4-ethylbenzenesulfonic acid-functionalized silica, 4-ethylbenzenesulfonic acid-functionalized fumed silica, n-propylsulfonic acid-functionalized silica, n-propylsulfonic acid-functionalized fumed silica, or combinations thereof; and The water-insoluble ion-conducting polymer is selected from polysaccharide polymers, cross-linked polyvinyl alcohol polymers, acid-complexed polyvinyl alcohol polymers, metal ion-complexed polyvinyl alcohol polymers, cross-linked poly(acrylic acid) polymers, metal ion-complexed poly(acrylic acid) polymers, acid-complexed poly(acrylic acid) polymers, cross-linked poly(methacrylic acid), metal ion-complexed poly(methacrylic acid), acid-complexed poly(methacrylic acid), or combinations thereof.

2. The composite proton conduction membrane according to claim 1, further comprising a microporous support membrane, the microporous support membrane being prepared from a polymer selected from: polyethylene, polypropylene, polytetrafluoroethylene, fluorinated ethylene propylene, polyvinylidene fluoride, polychlorotrifluoroethylene, polycaprolactam, a polymer prepared from hexamethylenediamine and adipic acid, polyacrylonitrile, polyethersulfone, sulfonated polyethersulfone, polysulfone, sulfonated polysulfone, poly(ether ether ketone), sulfonated poly(ether ether ketone), polyester, cellulose acetate, cellulose triacetate, cellulose, phenolic resin, polybenzimidazole, or combinations thereof.

3. The composite proton-conducting membrane according to claim 1, wherein the water-insoluble ion-conducting polymer is selected from cross-linked polysaccharide polymers, metal ion-complexed polysaccharide polymers, and acid-complexed polysaccharide polymers.

4. The composite proton-conducting membrane according to claim 1, wherein the polysaccharide polymer is selected from alginate, chitosan, hyaluronic acid, or combinations thereof.

5. The composite proton-conducting membrane according to claim 4, wherein the polysaccharide polymer is selected from cross-linked alginate, cross-linked chitosan, cross-linked hyaluronic acid, or combinations thereof.

6. A redox flow battery system, the redox flow battery system comprising: At least one rechargeable battery, the at least one rechargeable battery comprising a positive electrolyte, a negative electrolyte, and a composite proton conduction membrane according to claim 1, wherein the composite proton conduction membrane is positioned between the positive electrolyte and the negative electrolyte, the positive electrolyte being in contact with a positive electrode, and the negative electrolyte being in contact with a negative electrode.

7. A membrane electrode assembly, said membrane electrode assembly include: The composite proton-conducting membrane according to claim 1; The anode comprises an anode catalyst on one surface of the composite proton-conducting membrane; Anode gas diffusion layer; Cathode, the cathode comprising a cathode catalyst on the other surface of the composite proton-conducting membrane; and Cathode gas diffusion layer; The composite proton-conducting membrane comprises: Inorganic filler, wherein the inorganic filler has covalently bonded acidic functional groups and at least 150 m 2 / g high surface area; and Water-insoluble ion-conducting polymer.

8. A method for preparing a composite proton-conducting membrane, the method comprising: a. Preparation of dispersions of water-insoluble ion-conducting polymers in water, organic solvents, or water / organic solvent mixtures; b. A mixed dispersion comprising the water-insoluble ion-conducting polymer and the inorganic filler is prepared by adding a dispersion of the inorganic filler or an inorganic filler in water, an organic solvent, or a water / organic solvent mixture to the dispersion of the water-insoluble ion-conducting polymer under stirring and / or ultrasonication, wherein the inorganic filler has covalently bonded acidic functional groups and at least 150 m 2 / g high surface area; as well as A composite proton-conducting membrane is prepared by casting a layer of the aforementioned mixed dispersion onto a non-porous substrate or a microporous support membrane, followed by drying. The inorganic filler is aminopropyl-N,N-di(methylphosphonic acid)-functionalized silica, aminopropyl-N,N-di(methylphosphonic acid)-functionalized fumed silica, n-propylphosphonic acid-functionalized silica, n-propylphosphonic acid-functionalized fumed silica, p-toluenesulfonic acid-functionalized silica, p-toluenesulfonic acid-functionalized fumed silica, 4-ethylbenzenesulfonic acid-functionalized silica, 4-ethylbenzenesulfonic acid-functionalized fumed silica, n-propylsulfonic acid-functionalized silica, n-propylsulfonic acid-functionalized fumed silica, or combinations thereof; and The water-insoluble ion-conducting polymer is selected from polysaccharide polymers, cross-linked polyvinyl alcohol polymers, acid-complexed polyvinyl alcohol polymers, metal ion-complexed polyvinyl alcohol polymers, cross-linked poly(acrylic acid) polymers, metal ion-complexed poly(acrylic acid) polymers, acid-complexed poly(acrylic acid) polymers, cross-linked poly(methacrylic acid), metal ion-complexed poly(methacrylic acid), acid-complexed poly(methacrylic acid), or combinations thereof.

9. The method according to claim 8, wherein the water-insoluble ion-conducting polymer is selected from cross-linked polysaccharide polymers, metal ion-complexed polysaccharide polymers, and acid-complexed polysaccharide polymers.

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