CN115101790A - Composite electrolyte membrane with high conductivity and preparation method thereof - Google Patents
Composite electrolyte membrane with high conductivity and preparation method thereof Download PDFInfo
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- CN115101790A CN115101790A CN202210684009.3A CN202210684009A CN115101790A CN 115101790 A CN115101790 A CN 115101790A CN 202210684009 A CN202210684009 A CN 202210684009A CN 115101790 A CN115101790 A CN 115101790A
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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
- H01M8/10—Fuel cells with solid electrolytes
- H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
- H01M8/1018—Polymeric electrolyte materials
- H01M8/1041—Polymer electrolyte composites, mixtures or blends
- H01M8/1046—Mixtures of at least one polymer and at least one additive
- H01M8/1048—Ion-conducting additives, e.g. ion-conducting particles, heteropolyacids, metal phosphate or polybenzimidazole with phosphoric acid
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- H—ELECTRICITY
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
- H01M8/1018—Polymeric electrolyte materials
- H01M8/1065—Polymeric electrolyte materials characterised by the form, e.g. perforated or wave-shaped
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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
- H01M8/10—Fuel cells with solid electrolytes
- H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
- H01M8/1018—Polymeric electrolyte materials
- H01M8/1067—Polymeric electrolyte materials characterised by their physical properties, e.g. porosity, ionic conductivity or thickness
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- H—ELECTRICITY
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
- H01M8/1018—Polymeric electrolyte materials
- H01M8/1069—Polymeric electrolyte materials characterised by the manufacturing processes
- H01M8/1072—Polymeric electrolyte materials characterised by the manufacturing processes by chemical reactions, e.g. insitu polymerisation or insitu crosslinking
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- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
- H01M8/1018—Polymeric electrolyte materials
- H01M8/1069—Polymeric electrolyte materials characterised by the manufacturing processes
- H01M8/1081—Polymeric electrolyte materials characterised by the manufacturing processes starting from solutions, dispersions or slurries exclusively of polymers
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
- H01M8/1018—Polymeric electrolyte materials
- H01M8/1069—Polymeric electrolyte materials characterised by the manufacturing processes
- H01M8/1086—After-treatment of the membrane other than by polymerisation
- H01M8/1088—Chemical modification, e.g. sulfonation
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Abstract
The invention provides a composite electrolyte membrane with high conductivity and a preparation method thereof, wherein the preparation method comprises the following steps: s1: dissolving polybenzimidazole and polyvinylidene chloride in a polar organic solvent; s2: adding a cross-linking agent into S1, and uniformly stirring to obtain a polymer solution, wherein the cross-linking agent is a binary or multi-element halide R-X; s3: casting the polymer solution of S2 in a mould, drying and then carrying out heat treatment to obtain a polybenzimidazole film; s4: and (3) immersing the polybenzimidazole membrane obtained in the step (S3) in phosphoric acid, standing, and taking out the polybenzimidazole membrane after standing to obtain the composite electrolyte membrane. The preparation method has the advantages of simple preparation process, easy implementation, low cost, no change of PBI resin synthesis process and reaction conditions, no modification requirement on film forming equipment, very simple process, low raw material cost, and easy batch production, and the composite film obtained by the preparation method.
Description
Technical Field
The invention relates to the field of preparation of composite electrolyte membranes, in particular to a composite electrolyte membrane with high conductivity and a preparation method thereof.
Background
Nowadays, fossil energy is increasingly reduced and environmental problems caused by the use of fossil energy are increasingly highlighted, and hydrogen energy is considered as a good substitute for fossil energy, and the use of hydrogen energy requires energy conversion. The PEMFC (proton exchange membrane fuel cell) can be used as an energy conversion device and can be used as an energy device of mobile equipment such as new energy vehicles and the like. Proton exchange membrane PEM, also known as proton membrane or hydrogen ion exchange membrane, is an ion permselective membrane that functions in the cell to provide a pathway for proton transfer and transport, to separate gaseous reactants, and to block electrolytes.
Polybenzimidazole (PBI) and its derivatives are widely studied in PEM. Polybenzimidazole (PBI) is a linear heterocyclic polymer containing polybenzimidazole groups in repeating units, and has good thermal stability and chemical stability and higher mechanical strength, but polybenzimidazole does not have proton conductivity per se, so the polybenzimidazole can obtain higher proton conductivity after being compounded with phosphoric acid, usually higher phosphoric acid doping amount is needed to obtain higher battery performance, but also the mechanical performance of a film-forming material is reduced, a large amount of free acid which is easy to run off is generated when the phosphoric acid doping amount of the film material is too large, and the loss of phosphoric acid can cause the problems of performance reduction, size reduction, electrode corrosion and the like of the film material.
At present, in order to solve the problem of the reduction of the mechanical strength caused by the excessive doping amount of phosphoric acid, the strengthening linkage modification is generally carried out by adopting the crosslinking modification, and the strengthening linkage modification is divided into two main modes of copolymerization crosslinking and post covalent crosslinking according to different reactions. The copolymerization crosslinking is carried out in the process of synthesizing PBI resin, and 3,3' -diaminobenzidine and isophthalic acid react with polyacid compounds such as trimesic acid to obtain crosslinking modified polymer, and the polymer has a hyperbranched structure. And the covalent crosslinking modification is carried out after PBI is synthesized, PBI resin and a proper crosslinking agent are simultaneously dissolved in an organic solvent, and the crosslinking agent and N-H on imidazole rings on a PBI structure are subjected to substitution reaction. At present, dichloromethyl hypophosphorous acid, benzoxazole, dibromotoluene, epoxy resin and the like are commonly used as cross-linking agents, the cross-linking agents usually need to participate in the PBI resin synthesis reaction process, the PBI resin synthesis reaction is adversely affected, and the prepared resin is not easy to dissolve in an organic solvent due to the cross-linking effect, so that inconvenience is brought to film formation. There is therefore a need for improvements to existing processes.
Disclosure of Invention
In order to solve the problem that the mechanical strength of the existing electrolyte membrane is lost due to the over-high doped phosphoric acid amount, the composite electrolyte membrane with high conductivity and the preparation method thereof are provided.
The specific technical scheme is as follows:
a preparation method of a composite electrolyte membrane with high conductivity is characterized by comprising the following steps:
s1: dissolving polybenzimidazole and polyvinylidene chloride in a polar organic solvent;
s2: adding a cross-linking agent into S1, uniformly stirring to obtain a polymer solution, wherein the cross-linking agent is binary or multi-element halogenated hydrocarbon R-X, and modifying occurs after PBI synthesis, so that the cross-linking agent does not participate in PBI resin synthesis reaction, does not bring adverse effect to the PBI resin synthesis reaction, and does not bring the problem of difficult film forming of a composite film;
s3: casting the polymer solution of S2 in a mould, drying and then carrying out heat treatment to obtain a polybenzimidazole film;
s4: and (3) immersing the polybenzimidazole film obtained in the step (S3) in phosphoric acid, standing, and taking out the polybenzimidazole film after standing to obtain the composite electrolyte film.
After the polybenzimidazole membrane is treated by phosphoric acid doping, a large number of phosphoric acid molecules can enter between polymer chains to destroy hydrogen bonds in the polymer chains. And the "strong plasticizing" action of the incorporated phosphoric acid molecules can significantly reduce the mechanical properties of the membrane material, resulting in dimensional swelling. Crosslinking generally refers to a process of forming a network structure in a polymer, and is a common method for modifying a polymer, wherein the formed network structure can provide additional force when chain segments and inter-chain movement occur, so that the mechanical properties of a membrane material are improved. While the inter-polymer chain forces may be enhanced when swelling occurs, so that the membrane material exhibits higher dimensional stability. Meanwhile, the formation of a cross-linked network can provide greater resistance to phosphoric acid loss and improve the phosphoric acid retention capacity of the phosphoric acid.
The mass ratio of the polybenzimidazole, the polyvinylidene chloride and the organic solvent in the S1 is 1 (100-400).
The mass ratio of the cross-linking agent in the S2 to the mass of the polybenzimidazole and the polyvinylidene chloride is 1 (10-100), compared with an ionic cross-linking structure, the formed covalent cross-linking structure is more obviously improved on the mechanical property of the membrane, which means that the membrane can bear higher phosphoric acid doping level, but simultaneously, with the increase of the cross-linking degree, the chains of the polymer are more closely stacked, the doping capacity of the phosphoric acid is limited, and the mutual influence of the two is balanced, so that the use amount of the cross-linking agent needs to be controlled and optimized to achieve the optimal effect.
The temperature for heat treatment in the S3 is 150-200 ℃.
And the drying temperature in the S3 is 80-120 ℃.
X in the halogenated compound R-X is Cl, Br or I.
The organic solvent in the S1 is a mixture of N, N-dimethylformamide, N-dimethylacetamide, dimethyl sulfoxide and N-methylpyrrolidone mixed in any proportion.
And the standing time in the S4 is 1-12 h.
A composite electrolyte membrane with high conductivity is prepared by the preparation method.
Has the advantages that:
(1) according to the composite electrolyte membrane with high conductivity and the preparation method thereof, provided by the invention, aiming at the problem of reduction of the mechanical strength of the composite membrane, the composite membrane is modified by using the cross-linking agent, the cross-linking agent used in the preparation method is a binary or multi-element halide, and the modification is carried out after PBI is synthesized, so that the composite electrolyte membrane does not participate in PBI resin synthesis reaction, does not bring adverse effect to the PBI resin synthesis reaction, and does not bring the problem of difficult film forming of the composite membrane.
(2) The polymer skeleton has a grid structure by adding the cross-linking agent, and the composite membrane has higher mechanical strength by optimizing the addition proportion of the cross-linking agent.
(3) The amount of the crosslinking agent added in the preparation method is 1-10% of the weight of PBI/PVDF, the doping capacity of phosphoric acid is not limited, and the composite membrane can obtain excellent mechanical properties.
(4) The preparation process is simple, easy to implement, low in cost, free of change of the PBI resin synthesis process and reaction conditions, free of modification requirements on film forming equipment, very simple in process, low in raw material cost and easy for batch production.
Drawings
FIG. 1 is a graph of tensile curves of PVDF/polybenzimidazole membranes of different crosslinking ratios.
FIG. 2 shows proton conductivities of PVDF/polybenzimidazole/phosphoric acid composite membranes with different crosslinking ratios.
Detailed Description
For the purpose of enhancing the understanding of the present invention, the present invention will be further described in detail with reference to the following examples and the accompanying drawings, which are provided for the purpose of illustration only and are not intended to limit the scope of the present invention.
Example 1
A preparation method of a composite electrolyte membrane with high conductivity mainly comprises the following steps:
(1) 0.6g of polybenzimidazole was dissolved in 100g of N, N-dimethylformamide;
(2) after the polybenzimidazole in the step (1) is completely dissolved, casting the polymer solution in a flat mold, and drying at 100 ℃ to volatilize the organic solvent;
(3) after the organic solvent in the step (2) is completely volatilized, carrying out heat treatment at 180 ℃ to form a polybenzimidazole film;
(4) the polybenzimidazole membrane was immersed in concentrated sulfuric acid at 130 ℃ and allowed to stand for 12 hours.
Example 2
A preparation method of a composite electrolyte membrane with high conductivity mainly comprises the following steps:
(1) 0.6g of polybenzimidazole was dissolved in 100g of N, N-dimethylformamide;
(2) after the polybenzimidazole in the step (1) is completely dissolved, adding 0.024g of halohydrocarbon, and uniformly stirring to obtain a uniform and stable polybenzimidazole solution;
(3) casting the polymer solution in a flat mold, and drying at 100 ℃ to volatilize the organic solvent;
(4) after the organic solvent in the step (3) is completely volatilized, carrying out heat treatment at 180 ℃ to form a polybenzimidazole film;
(5) the polybenzimidazole membrane was immersed in concentrated sulfuric acid at 130 ℃ and allowed to stand for 12 hours.
Example 3
A preparation method of a composite electrolyte membrane with high conductivity mainly comprises the following steps:
(1) 0.6g of polybenzimidazole was dissolved in 100g of N, N-dimethylformamide;
(2) after the polybenzimidazole in the step (1) is completely dissolved, adding 0.042g of halohydrocarbon, and uniformly stirring to obtain a uniform and stable polybenzimidazole solution;
(3) casting the polymer solution in a flat mold, and drying at 100 ℃ to volatilize the organic solvent;
(4) after the organic solvent in the step (3) is completely volatilized, carrying out heat treatment at 180 ℃ to form a polybenzimidazole film;
(5) the polybenzimidazole membrane was immersed in concentrated sulfuric acid at 130 ℃ and allowed to stand for 12 hours.
The composite membranes prepared in the three groups of examples are subjected to performance tests:
(I) mechanical Property testing
The test method comprises the following steps: before testing, all samples are cut into sample pieces with certain specifications, and the composite electrolyte membrane in the running process has certain mechanical properties to bear the pressure generated by gas flow at two sides, so that the mechanical properties of the membrane samples are evaluated by tensile testing, wherein a tensile curve of a composite membrane prepared by using different cross-linking agent ratios is shown in figure 1, and as shown in figure 1, in example 1, because no cross-linking agent is added, a large number of phosphoric acid molecules enter a polymer to play a role of 'strong plasticization', so that the composite membrane shows lower mechanical strength, and in example 3, when the ratio of the cross-linking agent is 7% of the mass of PBI, the tensile strength is the best.
(II) proton conductivity test
The composite membrane samples prepared in the three groups of examples are cut into the same specification, and the cut samples are used for proton conductivity test. The test was carried out during the cooling from 180 ℃ to 100 ℃ to remove the effect of water, the impedance value (R) of the sample was measured by a four-electrode AC impedance method, and the proton conductivity σ was obtained by calculation, with the formula: σ ═ L/(a × R); wherein L is the distance between the two electrodes; a is the cross-sectional area of the film sample. FIG. 2 shows proton conductivity of composite membranes prepared using different ratios of cross-linking agents, from which it can be seen that the conductivity is best when the ratio of cross-linking agents is 4% by mass of PBI.
As a further improvement, the above-mentioned is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. A preparation method of a composite electrolyte membrane with high conductivity is characterized by comprising the following steps:
s1: dissolving polybenzimidazole and polyvinylidene chloride in a polar organic solvent;
s2: adding a cross-linking agent into S1, and uniformly stirring to obtain a polymer solution, wherein the cross-linking agent is binary or polybasic halogenated hydrocarbon R-X;
s3: casting the polymer solution of S2 in a mould, drying and then carrying out heat treatment to obtain a polybenzimidazole film;
s4: and (3) immersing the polybenzimidazole membrane obtained in the step (S3) in phosphoric acid, standing, and taking out the polybenzimidazole membrane after standing to obtain the composite electrolyte membrane.
2. The method for preparing a composite electrolyte membrane with high conductivity according to claim 1, wherein the mass ratio of the cross-linking agent in S2 to the mass ratio of the polybenzimidazole and the polyvinylidene chloride is 1 (10-100).
3. The method for preparing a composite electrolyte membrane with high conductivity according to claim 1, wherein the mass ratio of polybenzimidazole, polyvinylidene chloride and organic solvent in S1 is 1 (100-400).
4. The method for preparing a composite electrolyte membrane with high conductivity according to claim 1, wherein the temperature of the heat treatment in S3 is 150-200 ℃.
5. The method for preparing a composite electrolyte membrane with high conductivity according to claim 1, wherein the drying temperature in S3 is 80-120 ℃.
6. The method for preparing a composite electrolyte membrane with high conductivity according to claim 1, wherein X in the halogenated compound R-X is Cl, Br or I.
7. The method for preparing a composite electrolyte membrane with high conductivity according to claim 1, wherein the organic solvent in S1 is a mixture of N, N-dimethylformamide, N-dimethylacetamide, dimethylsulfoxide and N-methylpyrrolidone in any ratio.
8. The method for preparing a composite electrolyte membrane with high conductivity according to claim 1, wherein the standing time in S4 is 1-12 h.
9. A composite electrolyte membrane with high electrical conductivity, characterized in that it is produced by the method according to any one of claims 1 to 8.
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| CN116284778A (en) * | 2023-03-01 | 2023-06-23 | 上海空间电源研究所 | Polybenzimidazole with cross-linked structure, high-temperature proton exchange membrane and preparation method thereof |
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| CN116284778A (en) * | 2023-03-01 | 2023-06-23 | 上海空间电源研究所 | Polybenzimidazole with cross-linked structure, high-temperature proton exchange membrane and preparation method thereof |
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