CN116154245B - Proton exchange membrane for all-vanadium redox flow battery and preparation method thereof - Google Patents
Proton exchange membrane for all-vanadium redox flow battery and preparation method thereof Download PDFInfo
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/18—Regenerative fuel cells, e.g. redox flow batteries or secondary fuel cells
- H01M8/184—Regeneration by electrochemical means
- H01M8/188—Regeneration by electrochemical means by recharging of redox couples containing fluids; Redox flow type batteries
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Abstract
The invention provides a proton exchange membrane capable of being used for an all-vanadium redox flow battery, which comprises a proton exchange membrane base membrane, two first nano carbon coatings respectively positioned on two side surfaces of the proton exchange membrane base membrane and two second nano carbon coatings respectively positioned on two first nano carbon coatings, wherein the first nano carbon coatings comprise PFSA and nano carbon materials A, the second nano carbon coatings comprise PFSA and nano carbon materials B, the nano carbon materials A are selected from one or two of single-wall carbon nanotubes and multi-wall carbon nanotubes, and the nano carbon materials B are conductive carbon black. The proton exchange membrane has the advantages that the ion selectivity and the puncture strength are greatly improved, the contact resistance between the proton exchange membrane and the carbon felt electrode is reduced, and the cycle life and the energy efficiency of the vanadium redox flow battery are improved.
Description
Technical Field
The invention belongs to the technical field of battery materials, and particularly relates to a proton exchange membrane for an all-vanadium redox flow battery and a preparation method thereof.
Background
Compared with the traditional storage battery, the all-vanadium redox flow battery (VFB) is a novel electrochemical storage energy storage device and has the advantages of being independent and adjustable in system capacity and power, high in charging and discharging speed, safe and reliable, environment-friendly, long in cycle life, easy to maintain and the like.
The proton exchange membrane is one of key materials and important components of the all-vanadium redox flow battery, and can prevent mixing of vanadium ions with different valence states in positive and negative electrolyte while allowing hydrogen ions to pass through, so as to prevent the short circuit of the battery. Thus, proton exchange membranes determine to a large extent the coulombic efficiency, energy efficiency, and cycle life of all-vanadium redox flow batteries. The ideal proton exchange membrane should have the characteristics of high physicochemical stability, low membrane resistance, high vanadium ion selectivity, high proton conductivity, low water permeability and low cost.
At present, commercial proton exchange membranes commonly used at home and abroad are perfluorosulfonic acid series membranes, and although the perfluorosulfonic acid proton membranes have good chemical stability and high proton conductivity, the membranes have some defects: the dimensional stability is poor, the vanadium ion transmittance is high, and the self-discharge phenomenon of the battery is obvious. Therefore, how to prepare the proton exchange membrane material for the high-performance low-cost all-vanadium redox flow battery has become one of the key bottlenecks for restricting the engineering and technical development of the all-vanadium redox flow battery.
Various researches are also carried out on the modification of the perfluorosulfonic acid proton membrane at home and abroad, and the modification means mainly develop around how to reduce the permeability of vanadium ions. The modifying means mainly comprises the following steps: introducing organic or inorganic filler, mixing with other polymers, recasting to prepare a composite membrane, modifying the surface of a perfluorosulfonic acid Polymer (PFSA), and the like. However, the above methods have drawbacks. For example, the polymer is subjected to surface modification, so that the uniformity is poor, and the effect of blocking vanadium ion permeation cannot be achieved; the preparation process of the blending heavy casting compound is complex and tedious, the cost and the time consumption are relatively large, and the blending heavy casting compound is not suitable for large-scale industrialization; the introduction of the filler into the film body may cause the film to have a deteriorated structure and performance, such as a decreased conductivity, a decreased puncture strength, etc.
Disclosure of Invention
In order to overcome the problems in the prior art, the invention provides a proton exchange membrane for an all-vanadium redox flow battery and a preparation method thereof. According to the invention, the mixed slurry containing the nano carbon material is coated on two sides of the proton exchange membrane, and the nano carbon coating is formed after solidification, wherein the pore diameter of the nano carbon coating is in gradient change along the thickness direction of the coating (the pore diameter of the part close to the proton exchange membrane base membrane is smaller). According to the invention, the penetration of vanadium ions through the proton exchange membrane is greatly reduced, and the nano carbon coating can also reduce the contact resistance between the proton exchange membrane and the electrode. Meanwhile, the proton exchange membrane with the nano carbon coating has higher puncture strength, can meet the applicability of the proton exchange membrane under the working condition of higher compression ratio, and has important significance for prolonging the cycle life and the energy efficiency of the all-vanadium redox flow battery, reducing the volume of a galvanic pile and improving the power density of the galvanic pile.
Specifically, one aspect of the invention provides a proton exchange membrane, which comprises a proton exchange membrane base membrane, two first nano carbon coatings respectively positioned on two side surfaces of the proton exchange membrane base membrane and two second nano carbon coatings respectively positioned on two first nano carbon coating surfaces, wherein the first nano carbon coatings comprise perfluorosulfonic acid Polymer (PFSA) and nano carbon material A, the second nano carbon coatings comprise PFSA and nano carbon material B, the nano carbon material A is selected from one or two of single-wall carbon nanotubes and multi-wall carbon nanotubes, and the nano carbon material B is conductive carbon black.
In one or more embodiments, the proton exchange membrane base membrane is a perfluorosulfonic acid proton exchange membrane.
In one or more embodiments, the thickness of each of the first nanocarbon coating and the second nanocarbon coating is 3-15 μm independently.
In one or more embodiments, the total thickness of the first nanocarbon coating and the second nanocarbon coating on the same side of the proton exchange membrane base membrane is 10-20 μm.
In one or more embodiments, the first nanocarbon coating has a single-sided areal density of 1 x 10 -5 ~2.5×10 -4 g/cm 2 。
In one or more embodiments, in the first nanocarbon coating, the mass ratio of PFSA to nanocarbon material a is 1:1 to 10:1.
In one or more embodiments, the second nanocarbon coating has a single-sided areal density of 5 x 10 -4 ~ 4×10 -3 g/cm 2 。
In one or more embodiments, in the second nanocarbon coating, the mass ratio of PFSA to nanocarbon material B is 1:1 to 1:10.
In one or more embodiments, the average pore size of the first nanocarbon coating is less than the average pore size of the second nanocarbon coating.
In one or more embodiments, the average pore size of the first nanocarbon coating is 10-50 nm.
In one or more embodiments, the average pore size of the second nanocarbon coating is 100-200 nm.
In one or more embodiments, the average diameter of the nanocarbon material a is 2 to 20 nm.
In one or more embodiments, the average particle size of the nanocarbon material B is 30 to 100 nm.
In one or more embodiments, the proton exchange membrane base membrane includes a reaction region and a non-reaction region, and the first nanocarbon coating is located on a surface of the reaction region of the proton exchange membrane base membrane.
Another aspect of the present invention provides a method of making a proton exchange membrane as described in any of the embodiments herein, the method comprising the steps of:
(1) Dispersing PFSA and the nano carbon material A in a solvent A to obtain mixed slurry A; dispersing PFSA and the nano carbon material B in a solvent B to obtain mixed slurry B;
(2) And coating the mixed slurry A on two sides of the proton exchange membrane base membrane, drying to form the first nano carbon coating, coating the mixed slurry B on the surface of the first nano carbon coating, and drying to obtain the proton exchange membrane.
In one or more embodiments, the solvent a and the solvent B each independently comprise one or more selected from the group consisting of water and an alcoholic solvent; preferably, the solvent A comprises 80-100% of isopropanol and 0-20% of water by mass, the solvent B comprises 80-100% of isopropanol and 0-20% of water by mass.
In one or more embodiments, the mass fraction of PFSA in the mixed slurry A is 0.1% -0.5%, the mass fraction of the nano carbon material A is 0.05% -0.1%, the mass fraction of PFSA in the mixed slurry B is 0.1% -0.5%, and the mass fraction of the nano carbon material B is 0.5% -1%.
In one or more embodiments, in step (1), solvent a and solvent B are the same, both being the first solvent; firstly dispersing PFSA in a first solvent to obtain first mixed slurry, and dispersing the nano carbon material A in the first mixed slurry to obtain mixed slurry A; dispersing the nano carbon material B in the first mixed slurry to obtain mixed slurry B; preferably, the mass fraction of PFSA in the first mixed slurry is 0.1% -0.5%.
In one or more embodiments, the first solvent comprises one or more selected from the group consisting of water and an alcoholic solvent; preferably, the first solvent comprises 80-100% of isopropanol and 0-20% of water, wherein the isopropanol and the water are optionally present.
In one or more embodiments, in the step (2), the coating mode is spraying, knife coating or transfer printing, and the temperature of the two drying is 50-80 ℃.
The invention also provides proton exchange membranes prepared by the method described in any of the embodiments herein.
Another aspect of the invention provides an all-vanadium flow battery comprising a proton exchange membrane as described in any of the embodiments herein.
Drawings
FIG. 1 is a schematic illustration of the locations of the reaction and non-reaction zones of a proton exchange membrane in some embodiments of the present invention.
Fig. 2 is a schematic view of a proton exchange membrane containing a nanocarbon coating in some embodiments of the invention, wherein 1 is a proton exchange membrane base membrane and 2 is a nanocarbon coating.
Detailed Description
So that those skilled in the art can appreciate the features and effects of the present invention, a general description and definition of the terms and expressions set forth in the specification and claims follows. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs, and in the event of a conflict, the present specification shall control.
The theory or mechanism described and disclosed herein, whether right or wrong, is not meant to limit the scope of the invention in any way, i.e., the present disclosure may be practiced without limitation to any particular theory or mechanism.
Herein, "comprising," "including," "containing," and similar terms are intended to cover the meaning of "consisting essentially of … …" and "consisting of … …," e.g., "a consisting essentially of B and C" and "a consisting of B and C" should be considered to have been disclosed herein when "a comprises B and C" is disclosed herein.
In this document, all features such as values, amounts, and concentrations that are defined as ranges of values or percentages are for brevity and convenience only. Accordingly, the description of a numerical range or percentage range should be considered to cover and specifically disclose all possible sub-ranges and individual values (including integers and fractions) within the range.
Herein, unless otherwise specified, percentages refer to mass percentages, and proportions refer to mass ratios.
Herein, when embodiments or examples are described, it should be understood that they are not intended to limit the invention to these embodiments or examples. On the contrary, all alternatives, modifications, and equivalents of the methods and materials described herein are intended to be included within the scope of the invention as defined by the appended claims.
In this context, not all possible combinations of the individual technical features in the individual embodiments or examples are described in order to simplify the description. Accordingly, as long as there is no contradiction between the combinations of these technical features, any combination of the technical features in the respective embodiments or examples is possible, and all possible combinations should be considered as being within the scope of the present specification.
In the present invention, PFSA means as known in the art, perfluorosulfonic acid-based polymers.
In the present invention, the nanocarbon coating layer on one side of the proton exchange membrane base membrane preferably comprises at least two coating layers. In the present invention, the thickness of each nanocarbon coating layer is preferably 3 to 15 μm, for example 5 μm, 8 μm, 10 μm, 12 μm, and the total thickness of the coating layer on the proton exchange membrane base membrane side is preferably 10 to 20 μm, for example 11 μm, 13 μm, 15 μm, 18 μm. The thickness of the nano carbon coating is controlled within the range, so that the selectivity of the proton exchange membrane is improved, and the proton conductivity is ensured.
The proton exchange membrane base membrane suitable for the invention is a perfluorosulfonic acid proton exchange membrane.
In the invention, the nano carbon coating contacted with the proton exchange membrane base membrane is a first nano carbon coating. The first nanocarbon coating comprises PFSA and nanocarbonCarbon material a. The thickness of the first nanocarbon coating is preferably 3 to 15 μm, for example 3 to 10 μm, 3 to 5 μm. The single-sided area density of the first nanocarbon coating is preferably 1×10 -5 ~2.5×10 -4 g/cm 2 For example 2X 10 -5 g/cm 2 、4.4×10 -5 g/cm 2 、5×10 -5 g/cm 2 、1×10 -4 g/cm 2 、2×10 -4 g/cm 2 、2.3×10 -4 g/cm 2 . The thickness and the single-sided surface density of the first nano carbon coating are controlled within the range, so that the ion selectivity and the puncture strength of the proton exchange membrane are improved, and the contact resistance between the proton exchange membrane and the carbon felt electrode is reduced.
In the present invention, the nanocarbon material a may be a single-walled carbon nanotube (SWCNT), a multi-walled carbon nanotube (MWCNT), or a single/multi-walled mixed carbon tube (S/MWCNT). The average diameter of the nanocarbon material A is preferably 2 to 20 nm, for example, 5 nm, 10 nm, 15 nm. Controlling the average diameter of the nano carbon material A within the above range is beneficial to constructing a smaller nano pore structure while ensuring the high strength and high conductivity of the nano carbon material A.
In the first nanocarbon coating, the mass ratio of PFSA to nanocarbon material a may be 1:1 to 10:1, for example 1.2:1, 1.3:1, 1.5:1, 2:1, 2.1:1, 2.5:1, 5:1. Controlling the mass ratio of the PFSA and the nano carbon material A within the above range is beneficial to enabling the first nano carbon coating to have an average pore diameter of 10-50 nm.
In the invention, one surface of the first nano carbon coating is contacted with the proton exchange membrane base membrane, and the other surface is contacted with the second nano carbon coating. The second nanocarbon coating comprises PFSA and nanocarbon material B. The thickness of the second nanocarbon coating is preferably 3 to 15 μm, for example 5 to 15 μm, 8 to 15 μm, 10 to 15 μm. The single-sided density of the second nanocarbon coating is preferably 5×10 -4 ~4×10 -3 g/cm 2 For example 6X 10 -4 g/cm 2 、8×10 -4 g/cm 2 、1×10 -3 g/cm 2 、2×10 -3 g/cm 2 、3×10 -3 g/cm 2 、3.6×10 - 3 g/cm 2 . Controlling the thickness and the single-sided area density of the second nano carbon coating to beIn the range, the ion selectivity and the puncture strength of the proton exchange membrane are improved, and the contact resistance between the proton exchange membrane and the carbon felt electrode is reduced.
In the invention, the nano carbon material B is conductive carbon black. Examples of conductive carbon black include ketjen black, acetylene black, and the like, such as Vulcan XC-72 carbon black, EC600JD carbon black. The average particle diameter of the nanocarbon material B is preferably 30 to 100. 100 nm, for example 35. 35 nm, 40. 40 nm, 50. 50 nm, 70. 70 nm. Compared with the micron-sized pore structure of the electrode material, the nano-sized pores can be constructed by coating the nano-carbon material B with the average particle diameter in the above range.
In the second nanocarbon coating, the mass ratio of the PFSA to the nanocarbon material B may be 1:1 to 1:10, for example, 1:2, 1:5. Controlling the mass ratio of the PFSA and the nano carbon material B within the above range is beneficial to enabling the second nano carbon coating to have an average pore diameter of 100-200 nm.
The proton exchange membrane can be prepared by coating slurry containing nano carbon materials on two sides of a proton exchange membrane base membrane, and forming a nano carbon coating after curing. In some embodiments, the invention designs the gradient structure of the aperture of the nano carbon coating along the thickness direction of the coating, the aperture of the nano carbon coating close to the proton exchange membrane base membrane is smaller, and the aperture of the nano carbon coating far away from the proton exchange membrane base membrane is larger, so as to better play roles in preventing vanadium ion permeation, reducing membrane resistance and enhancing. Preferably, the average pore diameter of the first nanocarbon coating is 10-50 nm, for example 20 nm, 30 nm, 40 nm. Preferably, the average pore diameter of the second nanocarbon coating is 100-200 nm, for example 120 nm, 150 nm, 180 nm. The use of nanocarbon material a and nanocarbon material B as the nanocarbon materials of the first nanocarbon coating layer and the second nanocarbon coating layer, respectively, is advantageous in that the pore diameters of the first nanocarbon coating layer and the second nanocarbon coating layer form the aforementioned gradient structure design.
As shown in fig. 1, the proton exchange membrane base membrane comprises a reaction area and a non-reaction area, wherein the reaction area is positioned in the middle of the proton exchange membrane base membrane, and the non-reaction area is positioned around the reaction area. In some embodiments, as shown in fig. 2, two layers of nanocarbon coating 2 are located on the surface of the reaction region of the proton exchange membrane base membrane 1.
The proton exchange membrane can be prepared by adopting the method comprising the following steps:
(1) Dispersing PFSA and the nano carbon material A in a solvent A to obtain mixed slurry A; dispersing PFSA and the nano carbon material B in a solvent B to obtain mixed slurry B;
(2) And coating the mixed slurry A on two sides of the proton exchange membrane base membrane, drying to form the first nano carbon coating, coating the mixed slurry B on the surface of the first nano carbon coating, and drying to obtain the proton exchange membrane.
In the present invention, the solvent a and the solvent B may contain one or more selected from water and alcohol solvents. Preferably, solvent a and solvent B comprise isopropanol and optionally water. Preferably, in solvent A and solvent B, the total mass fraction of isopropanol and optionally water is greater than or equal to 80%, for example greater than or equal to 90%, greaterthan or equal to 95%, greaterthan or equal to 98%, greaterthan or equal to 99%, 100%. Preferably, in the solvent A and the solvent B, the mass fraction of the isopropanol is 80% -100%, for example 90% -100%, 95% -100%, 98% -100%, 99% -100%, and the mass fraction of the water is 0% -20%, for example 0% -10%, 0% -5%, 0% -2%, 0% -1%. In some embodiments, solvent a and solvent B are free of water.
In the invention, the mass fraction of PFSA in the mixed slurry A is preferably 0.1% -0.5%, such as 0.125%, 0.2%, 0.25%, 0.3%, 0.4%, and the mass fraction of the nano carbon material A is preferably 0.05% -0.1%, such as 0.06%, 0.07%, 0.08%, 0.09%, 0.096%. Controlling the mass fraction of PFSA and nanocarbon material a in the mixed slurry a within the aforementioned range is advantageous for forming a first nanocarbon coating having a thickness, average pore diameter, areal density, and mass ratio of PFSA and nanocarbon material a satisfying the aforementioned requirements.
In the invention, the mass fraction of PFSA in the mixed slurry B is preferably 0.1% -0.5%, such as 0.125%, 0.2%, 0.25%, 0.3%, 0.4%, and the mass fraction of the nano carbon material B is preferably 0.5% -1%, such as 0.6%, 0.7%, 0.8%, 0.9%. Controlling the mass fraction of PFSA and nanocarbon material B in the mixed slurry B within the aforementioned range is advantageous for forming a second nanocarbon coating having a thickness, an average pore diameter, an areal density, and a mass ratio of PFSA and nanocarbon material B satisfying the aforementioned requirements.
In the invention, when PFSA and the nano carbon material A or B are dispersed in the solvent A or B, ultrasonic dispersion is preferably carried out, and the ultrasonic time can be 30-60 min.
In some embodiments, the proton exchange membrane of the present invention is prepared by a process comprising the steps of:
firstly, mixing PFSA and a first solvent in a certain proportion to obtain mixed slurry of the PFSA and the first solvent, namely first mixed slurry;
secondly, weighing a proper amount of nano carbon material A, mixing the nano carbon material A with the first mixed slurry in a certain proportion, and preferably performing ultrasonic dispersion to obtain mixed slurry containing the nano carbon material A, namely mixed slurry A;
thirdly, weighing a proper amount of nano carbon material B, mixing the nano carbon material B with the first mixed slurry in a certain proportion, and preferably performing ultrasonic dispersion to obtain mixed slurry containing the nano carbon material B, namely mixed slurry B;
and fourthly, a proper amount of mixed slurry A is coated on the reaction areas on two sides of the proton exchange membrane base membrane, a proper amount of mixed slurry B is further coated on the formed first nano carbon coating after the mixed slurry A is dried and solidified, and the proton exchange membrane containing the nano carbon coating can be obtained after the mixed slurry A is completely dried and solidified.
In the present invention, the first solvent may comprise one or more selected from water and alcohol solvents, preferably a mixed solvent comprising isopropyl alcohol and optionally water. In a preferred embodiment, the total mass fraction of isopropanol and optionally water in the first solvent is greater than or equal to 80%, for example greater than or equal to 90%, greaterthan or equal to 95%, greaterthan or equal to 98%, greaterthan or equal to 99%, 100%. In a preferred embodiment, the mass fraction of isopropanol in the first solvent is 80% -100%, for example 90% -100%, 95% -100%, 98% -100%, 99% -100%, and the mass fraction of water is 0% -20%, for example 0% -10%, 0% -5%, 0% -2%, 0% -1%. In the present invention, the water is preferably deionized water. In some embodiments, the first solvent is free of water.
In the present invention, the mass fraction of PFSA in the first mixed slurry is preferably 0.1% -0.5%, for example 0.125%, 0.2%, 0.25%, 0.3%, 0.4%.
In the invention, the mass fraction of the nano carbon material A in the mixed slurry A is preferably 0.05% -0.1%, such as 0.06%, 0.07%, 0.08%, 0.09% and 0.096%. When the nano carbon material A and the first mixed slurry are subjected to ultrasonic dispersion, the ultrasonic time can be 30-60 min.
In the invention, the mass fraction of the nano carbon material B in the mixed slurry B is preferably 0.5% -1.0%, for example 0.6%, 0.7%, 0.8% and 0.9%. When the nano carbon material B and the first mixed slurry are subjected to ultrasonic dispersion, the dispersion time can be 30-60 min.
The mixed slurry A and the mixed slurry B can be coated by spraying, knife coating or transfer printing. When the mixed slurry A and the mixed slurry B are dried, the drying temperature may be 50 to 80 ℃, for example 60 ℃ and 70 ℃, and the drying time may be 15 to 30 minutes.
The invention includes proton exchange membranes prepared by the methods described in any of the embodiments herein. The invention also includes an all-vanadium flow battery comprising a proton exchange membrane as described in any of the embodiments herein.
The invention has the following beneficial technical effects: compared with an unmodified proton exchange membrane, the modified proton exchange membrane has the advantages that the ion selectivity and the puncture strength are greatly improved, the contact resistance between the modified proton exchange membrane and a carbon felt electrode is reduced, the modified proton exchange membrane can be suitable for the assembly and the operation of a battery in a high compression ratio state, the cycle life and the energy efficiency of an all-vanadium redox flow battery are improved, the volume of a galvanic pile is reduced, and the power density of the galvanic pile is improved.
The invention will be illustrated by way of specific examples. It should be understood that these examples are illustrative only and are not intended to limit the scope of the invention. The methods, reagents and materials used in the examples are those conventional in the art unless otherwise indicated. The starting compounds in the examples are all commercially available. In the invention, the thickness of the nano carbon coating is measured by a digital display micrometer, and the aperture is measured by an aperture analyzer.
Example 1
The proton exchange membrane containing the nano carbon coating is prepared in the embodiment:
1. 1.25 PFSA solution (PFSA content 10wt% manufactured by Belgium Sovier Co., ltd.) of g was weighed and dissolved in 100 g isopropyl alcohol to obtain a mixed solution of PFSA solution and isopropyl alcohol;
2. 0.015 g of SWCNT (average diameter 2 nm, chengdu Ke Zhou Naenergy technology) is weighed and dissolved in the mixed solution of the PFSA solution of 25 g and isopropanol, and the mixed slurry (mixed slurry A) containing the SWCNT is obtained after ultrasonic dispersion for 60 min by a cell breaker, wherein the PFSA concentration in the mixed slurry A is about 0.125wt%, the SWCNT concentration is about 0.06wt%, and the mass ratio of the PFSA to the SWCNT is about 2.1:1;
3. weighing 0.300 g of Vulcan XC-72 carbon black (average particle size is 30 nm), dissolving the Vulcan XC-72 carbon black in a mixed solution of 50 g PFSA solution and isopropanol, and performing ultrasonic dispersion for 30 min to obtain a mixed slurry (mixed slurry B) containing carbon black, wherein the concentration of PFSA in the mixed slurry B is about 0.125wt%, the concentration of carbon black is about 0.6wt%, and the mass ratio of PFSA to carbon black is about 1:4.8;
4. 1.14 and g SWCNT-containing mixed slurry was removed and uniformly sprayed onto the reaction zone (area 48 cm) on one side of a perfluorosulfonic acid proton exchange membrane (N212, duPont, U.S.) 2 ) The single-sided coating amount of the mixed slurry A was found to be 2.375×10 by conversion -2 g/cm 2 The modified perfluorosulfonic acid proton exchange membrane containing the single-layer nano carbon coating is obtained by drying and curing at 60 ℃, and the single-side surface density of the first nano carbon coating is about 4.4 multiplied by 10 through conversion -5 g/cm 2 ；
5. The mixed slurry containing the carbon black of 4.00 times g is continuously removed and evenly sprayed on the solidified single-layer carbon coating, and the single-side coating amount of the mixed slurry B is about 8.3 multiplied by 10 after conversion -2 g/cm 2 The modified perfluorosulfonic acid proton exchange membrane containing the double-layer nano carbon coating is obtained by drying and curing at 60 ℃, and the single-side surface density of the second nano carbon coating is about 6 multiplied by 10 through conversion -4 g/cm 2 The method comprises the steps of carrying out a first treatment on the surface of the And then the other side of the proton exchange membrane is treated by adopting the same operation, so as to obtain the modified perfluorosulfonic acid proton exchange membrane with the nano carbon coating on both sides of the membrane. Measured byThe first nanocarbon coating had a thickness of 3 μm and an average pore diameter of 20 nm, and the second nanocarbon coating had a thickness of 8 μm and an average pore diameter of 150 nm.
Example 2
1. 1.25 PFSA solution (PFSA content 10wt% manufactured by Belgium Sovier Co., ltd.) of g was weighed and dissolved in 100 g isopropyl alcohol to obtain a mixed solution of PFSA solution and isopropyl alcohol;
2. weighing 0.024 g of MWCNT (average diameter 10 nm, chengdu Ke-Shi nano energy technology), dissolving the MWCNT in the mixed solution of the PFSA solution of 25 g and isopropanol, and performing ultrasonic dispersion for 30 min by a cell disruptor to obtain mixed slurry (mixed slurry A) containing the MWCNT, wherein the concentration of PFSA in the mixed slurry A is about 0.125wt%, the concentration of the MWCNT is about 0.096wt%, and the mass ratio of the PFSA to the MWCNT is about 1.3:1;
3. 0.300 g of EC600JD carbon black (average particle size 35 nm) is weighed and dissolved in the mixed solution of 50 g PFSA solution and isopropanol, and the mixed slurry (mixed slurry B) containing carbon black is obtained after ultrasonic dispersion for 30 min, wherein the concentration of PFSA in the mixed slurry B is about 0.125wt%, the concentration of carbon black is about 0.6wt%, and the mass ratio of PFSA to carbon black is about 1:4.8;
4. the mixed slurry containing MWCNT was removed by 5.0. 5.0 g, and uniformly sprayed onto the reaction zone (area 48 cm) on one side of the perfluorosulfonic acid proton exchange membrane (N-212, manufactured by Jiangsu Kongsu Co., ltd.) 2 ) The single-sided coating amount of the mixed slurry A was found to be 0.104 g/cm by conversion 2 The modified perfluorosulfonic acid proton membrane containing the single-layer nano carbon coating is obtained by drying and curing at 70 ℃, and the single-side surface density of the first nano carbon coating is about 2.3 multiplied by 10 after conversion -4 g/cm 2 ；
5. Continuously transferring the mixed slurry containing 24.00 and g carbon black, uniformly spraying the mixed slurry on the solidified single-layer carbon coating, and converting to obtain the single-side coating amount of the mixed slurry B of about 0.5 g/cm 2 The modified perfluorosulfonic acid proton membrane containing the double-layer nano carbon coating is obtained by drying and curing at 60 ℃, and the single-side surface density of the second nano carbon coating is about 3.6x10 after conversion -3 g/cm 2 The method comprises the steps of carrying out a first treatment on the surface of the Then the same operation is adopted to exchange the other side of the proton exchange membraneAnd (3) processing to obtain the modified perfluorosulfonic acid proton membrane with the nano carbon coating on both sides of the membrane. The first nanocarbon coating was measured to have a thickness of 5 μm and an average pore size of 50 nm, and the second nanocarbon coating was measured to have a thickness of 15 μm and an average pore size of 120 nm.
Comparative example 1
Perfluorosulfonic acid proton exchange membrane (NR 212, duPont, U.S.A.).
Comparative example 2
1. 1.25 PFSA solution (PFSA content 10wt% manufactured by Belgium Sovier Co., ltd.) was weighed and dissolved in 100 g isopropyl alcohol to obtain a mixed solution of PFSA solution and isopropyl alcohol;
2. weighing 0.30 g of Vulcan XC-72 carbon black (average particle size is 30 and nm), dissolving the Vulcan XC-72 carbon black in a mixed solution of 50 g PFSA solution and isopropanol, and performing ultrasonic dispersion for 30 min to obtain a mixed slurry containing carbon black, wherein the concentration of PFSA in the mixed slurry is about 0.125wt%, the concentration of carbon black is about 0.6wt%, and the mass ratio of PFSA to carbon black is about 1:4.8;
3. a mixed slurry of 4.00. 4.00 g carbon black was removed and sprayed uniformly onto the reaction zone (area 48 cm) on one side of a perfluorosulfonic acid proton exchange membrane (NR 212, duPont, U.S.) 2 ) The single-sided coating amount of the mixed slurry is about 8.3X10 after conversion -2 g/cm 2 The modified perfluorosulfonic acid proton exchange membrane containing the single-layer nano carbon coating is obtained by drying and curing at 60 ℃, and the single-side surface density of the nano carbon coating is about 6 multiplied by 10 after conversion -4 g/cm 2 The method comprises the steps of carrying out a first treatment on the surface of the And then the other side of the proton exchange membrane is treated by adopting the same operation, so as to obtain the modified perfluorosulfonic acid proton exchange membrane with the nano carbon coating on both sides of the membrane. The nanocarbon coating was measured to have a thickness of 8 μm and an average pore diameter of 150 nm.
Test example 1
The perfluorosulfonic acid proton exchange membranes of examples 1-2 and comparative examples 1-2 were subjected to puncture strength test (GB/T37841-2019), and the results are shown in Table 1. The results show that the puncture strength of the modified perfluorosulfonic acid proton membrane of example 1 is increased from 140N/mm to 170N/mm compared to the unmodified perfluorosulfonic acid proton membrane of comparative example 1, and thus can be applied to battery assembly under high compression ratio conditions.
Table 1: puncture strength of perfluorosulfonic acid proton exchange membranes of examples 1-2 and comparative examples 1-2
Test example 2
The perfluorosulfonic acid proton exchange membranes of examples 1-2 and comparative examples 1-2 were assembled into batteries, and the characteristics (energy efficiency, internal resistance of charge and discharge) and stability of the batteries were tested, and the results are shown in tables 2 and 3, respectively.
Wherein the battery preparation conditions are as follows: active substances in the positive and negative electrolyte are respectively 1.5 mol/L V 4+ /V 5+ And 1.5 mol/L V 2+ /V 3+ The supporting electrolyte is sulfuric acid with the concentration of 3 mol/L, the volume of the positive and negative electrolyte is 70 mL, the electrode is a carbon felt electrode (produced by Liaoyang Jingu), and the effective area of the carbon felt electrode is 48 cm 2 The compression ratio was 40%.
In the characteristic test, constant current test is adopted, and the electric density is 150, 200, 250 and 300 mA/cm in sequence 2 The upper limit of charge is 1.55V, the lower limit of discharge is 1.00V, and each electric charge circulates 5 times.
In the stability test, constant current test is adopted, and the density is 200 mA/cm 2 The upper limit of charge is 1.55V, the lower limit of discharge is 1.00V, and the cycle is 200 times.
Test results: all vanadium flow batteries, 150, 200, 250 and 300 mA/cm, employing the unmodified perfluorosulfonic acid proton membrane of comparative example 1 2 The energy efficiencies below are 84.40%, 82.13%, 80.28% and 78.74%, respectively; 200 mA/cm 2 The energy efficiency decays from 82.13% to 81.15% over 200 cycles. Whereas all vanadium flow batteries employing the modified perfluorosulfonic acid proton exchange membrane of example 1, 150, 200, 250 and 300 mA/cm 2 The energy efficiencies below are 85.36%, 83.86%, 82.63% and 81.77%, respectively; 200 mA/cm 2 The energy efficiency decays from 83.86% to 83.25% after 200 cycles; and the internal resistance of charge and discharge is reduced by about 15% -45% compared with comparative example 1.
Table 2: energy efficiency of cells assembled from perfluorosulfonic acid proton exchange membranes of examples 1-2 and comparative examples 1-2
Table 3: charge and discharge internal resistance of batteries assembled from the perfluorosulfonic acid proton exchange membranes of examples 1-2 and comparative examples 1-2
Claims (8)
1. The proton exchange membrane is characterized by comprising a proton exchange membrane base membrane, two first nano carbon coatings respectively positioned on two side surfaces of the proton exchange membrane base membrane and two second nano carbon coatings respectively positioned on two first nano carbon coatings, wherein the first nano carbon coatings are composed of PFSA and nano carbon materials A, the second nano carbon coatings are composed of PFSA and nano carbon materials B, the nano carbon materials A are selected from one or two of single-wall carbon nanotubes and multi-wall carbon nanotubes, the average diameter of the nano carbon materials A is 2-20 nm, the nano carbon materials B are conductive carbon black, the average particle diameter of the nano carbon materials B is 30-100 nm, the average pore diameter of the first nano carbon coatings is 10-50 nm, and the average pore diameter of the second nano carbon coatings is 100-200 nm.
2. The proton exchange membrane of claim 1, wherein the proton exchange membrane has one or more of the following characteristics:
the proton exchange membrane base membrane is a perfluorosulfonic acid proton exchange membrane;
the thickness of each first nano carbon coating and the thickness of each second nano carbon coating are respectively and independently 3-15 mu m;
the total thickness of the first nano carbon coating and the second nano carbon coating which are positioned on the same side of the proton exchange membrane base membrane is 10-20 mu m;
the first mentionedThe single-sided area density of the nano carbon coating is 1 multiplied by 10 -5 ~2.5×10 -4 g/cm 2 ；
In the first nano carbon coating, the mass ratio of PFSA to the nano carbon material A is 1:1-10:1;
the single-sided surface density of the second nano carbon coating is 5 multiplied by 10 -4 ~4×10 -3 g/cm 2 ；
In the second nano carbon coating, the mass ratio of the PFSA to the nano carbon material B is 1:1-1:10;
the proton exchange membrane base membrane comprises a reaction area and a non-reaction area, and the first nano carbon coating is positioned on the surface of the reaction area of the proton exchange membrane base membrane.
3. A method of making the proton exchange membrane of claim 1 or 2, comprising the steps of:
(1) Dispersing PFSA and the nano carbon material A in a solvent A to obtain mixed slurry A; dispersing PFSA and the nano carbon material B in a solvent B to obtain mixed slurry B;
(2) Coating the mixed slurry A on two sides of the proton exchange membrane base membrane, drying to form the first nano carbon coating, coating the mixed slurry B on the surface of the first nano carbon coating, and drying to obtain the proton exchange membrane;
the solvent A comprises 80-100% of isopropanol or isopropanol and 0-20% of water, the solvent B comprises 80-100% of isopropanol or isopropanol and 0-20% of water.
4. The method according to claim 3, wherein the mass fraction of PFSA in the mixed slurry A is 0.1% -0.5%, the mass fraction of the nano carbon material A is 0.05% -0.1%, the mass fraction of PFSA in the mixed slurry B is 0.1% -0.5%, and the mass fraction of the nano carbon material B is 0.5% -1%.
5. A method according to claim 3, wherein in step (1), the solvent a and the solvent B are the same, both being first solvents; firstly dispersing PFSA in a first solvent to obtain first mixed slurry, and dispersing the nano carbon material A in the first mixed slurry to obtain mixed slurry A; dispersing the nano carbon material B in the first mixed slurry to obtain mixed slurry B; the mass fraction of PFSA in the first mixed slurry is 0.1% -0.5%.
6. The method of claim 3, wherein in the step (2), the coating is performed by spraying, knife coating or transfer printing, and the temperature of the two drying steps is 50-80 ℃.
7. A proton exchange membrane prepared by the method of any one of claims 3-6.
8. An all-vanadium flow battery comprising the proton exchange membrane of claim 1, 2 or 7.
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