Disclosure of Invention
The invention aims to provide a composite diaphragm for a flow battery and a preparation method thereof, wherein the composite diaphragm not only has better conductivity in an electrolyte, but also can effectively block free active substances in the electrolyte, prevent the self-discharge of the battery, improve the comprehensive performance of the flow battery and ensure the continuous and stable operation of the battery.
In order to achieve the purpose, the invention adopts the following technical scheme:
the composite diaphragm for the flow battery is obtained by coating an ion exchange layer on one side of a microporous diaphragm of a zinc-bromine flow battery, wherein the ion exchange layer is formed by coating an ion exchange solution added with a surfactant, the ion exchange solution is a perfluorosulfonic acid ion exchange solution, a sulfonated polysulfone ion exchange solution or a sulfonated polyethersulfone ion exchange solution, and the surfactant is an anionic surfactant.
The zinc-bromine flow battery microporous membrane is prepared by mixing 10-35 parts by weight of silicon dioxide, 35-65 parts by weight of plasticizer, 10-40 parts by weight of PE raw material, 1-5 parts by weight of color master batch for absorbing 900-1000nm laser energy and 1-2 parts by weight of antioxidant.
The addition amount of the surfactant in the ion exchange solution is 0.08-0.12g/1ml solution.
The ion exchange solution is prepared by the following method:
adding 1 weight part of perfluorinated sulfonic acid resin, 1 weight part of sulfonated polysulfone resin or sulfonated polyether sulfone resin and 12.7-23.3 weight parts of high-boiling-point solvent into a high-pressure reaction kettle, stirring and heating to 200-250 ℃, keeping the pressure at 1-1.5MPa for 2-6h, then cooling to room temperature, discharging solution from the reaction kettle, precipitating and filtering to obtain filtrate, namely the ion exchange solution.
In the preparation process of the composite diaphragm for the flow battery and the ion exchange solution, the resin and the solvent are stirred and heated to 200 ℃ and the pressure is 1MPa, and the temperature is kept for 4 hours.
The high-boiling-point solvent is N, N-dimethylformamide, N-dimethylacetamide or dimethyl sulfoxide.
In the composite diaphragm for the flow battery, the anionic surfactant is sodium dodecyl benzene sulfonate or an active agent containing sodium dodecyl benzene sulfonate; because the ion exchange solution contains sulfonic acid groups and the sodium dodecyl benzene sulfonate also contains sulfonic acid groups, the sodium dodecyl benzene sulfonate used as the surfactant can not introduce other groups, and is easy to obtain and low in cost.
The preparation method of the composite separator for the flow battery comprises the following steps:
A. cutting the microporous diaphragm;
B. adding a surfactant into the ion exchange solution, and uniformly stirring to obtain a coating solution;
C. coating the surface of one side of the microporous membrane cut in the step A with the coating solution prepared in the step B;
D. putting the coated microporous diaphragm into an oven for drying, taking out and cooling to room temperature;
E. repeating the steps C-D for 2-5 times to obtain the product.
Further, the preparation method of the composite diaphragm for the flow battery comprises the following steps:
A. cutting the microporous membrane into the actual required size;
B. adding a surfactant into the ion exchange solution, wherein the addition amount of the surfactant is 0.08-0.12g/1ml of solution, and uniformly stirring to obtain a coating solution;
C. coating the surface of one side of the microporous membrane cut in the step A with the coating solution prepared in the step B in an amount of 1.3-2.1ml/1dm 2 ;
D. Putting the coated microporous membrane into an oven, drying at 40-70 ℃ for 20-120min, taking out and cooling to room temperature;
E. repeating the step C-D for 3-4 times to obtain the product.
In the preparation method of the composite diaphragm for the flow battery, in the step C, the coating mode is spraying, brushing or rolling.
Compared with the prior art, the invention has the following advantages: the composite diaphragm has good conductivity in electrolyte, can effectively block free active substances in the electrolyte, prevents the occurrence of self-discharge of the battery, can improve the comprehensive performance of the flow battery, and ensures the continuous and stable operation of the battery. Compared with the traditional microporous diaphragm, the composite diaphragm effectively blocks active substances in the electrolyte, greatly reduces the self-discharge of the battery and improves the charge and discharge performance of the battery; compared with the ion exchange membrane, the membrane has high mechanical strength, is not easy to damage, prolongs the service life of the battery, and has comprehensive performance superior to that of the microporous membrane and the ion exchange membrane. The composite membrane of the invention has thin ion exchange layer, less resin consumption and reduced production cost.
The preparation method of the composite diaphragm is to make the ion exchange layer completely attached to the microporous diaphragm, various coating modes including roll coating, dip coating, spray coating and the like all aim at making the film layer complete, and the ion exchange layer has certain thickness so as to ensure the ion exchange function. According to the preparation method, the surfactant is added into the ion exchange solution, so that the solute of the ion exchange solution effectively enters the micropores of the microporous diaphragm, a tiny polymer is generated in the micropores, the polymer is a chain polymer, and the chain polymer extends in the electrolyte to form a polymer brush and block active substances in the electrolyte. If the dosage of the ion exchange solution is large, a complete and continuous film layer can be formed by one-time coating, but the film layer can cover the holes of the microporous diaphragm, so that the resistance of the composite diaphragm in the electrolyte is increased, and the voltage efficiency of the battery is reduced; if the coating amount is reduced, the number of ion exchange functional groups is reduced, so that the capability of blocking active substances in the electrolyte is reduced, and the self-discharge of the battery is caused, thereby reducing the coulomb efficiency. The invention uses a mode of multiple coating, the dosage of ion exchange solution coated once is less, the surfactant is added in the ion exchange solution, a continuous film layer can not be formed, the micro polymer generated in the micropore diaphragm hole is used for exchanging ions, the resistance can not be increased, the number of ion exchange active groups is further increased, the voltage loss is reduced, the charging and discharging efficiency of the battery is improved, and the continuous and stable operation of the battery is ensured.
Detailed Description
Example 1 of the invention: a preparation method of a composite diaphragm for a flow battery comprises the following steps:
A. cutting the zinc-bromine flow battery microporous membrane into 10cm multiplied by 10cm (the zinc-bromine flow battery microporous membrane is prepared by mixing 240g of silicon dioxide (the brand number of AEROSIL 200), 500g of plasticizer (special oil for PE separators), 240g of PE raw material (120 g of UHMWPE with 500 million molecular weight and 120g of HDPE with 20 million molecular weight), 10g of color master (such as plasblak un 2014) for absorbing laser energy of 900-1000nm and 10g of antioxidant);
B. adding 200g of perfluorosulfonic acid resin and 3800g of high-boiling-point solvent N, N-Dimethylformamide (DMF) into a high-pressure reaction kettle, stirring and heating to 200 ℃, keeping the temperature for 4 hours under the pressure of 1.0MPa, then cooling to room temperature, discharging the solution from the reaction kettle, and preparing perfluorosulfonic acid ion exchange solution through precipitation and filtration; measuring 10ml of perfluorinated sulfonic acid ion exchange solution, adding 1g of sodium dodecyl benzene sulfonate, and uniformly stirring to obtain a coating solution;
C. brushing the coating solution prepared in the step B on one side of the microporous membrane cut in the step A, wherein the brushing amount is 1.7ml;
D. putting the coated microporous membrane into an oven, heating at 60 ℃ for 30min, taking out and cooling to room temperature;
E. repeating the steps C-D for 3 times to obtain the product.
The composite membrane prepared in the embodiment and used for the flow battery is assembled in a zinc-bromine single flow battery developed by the applicant to test the battery performance, and the test conditions are as follows: electrolyte concentration: the zinc bromide was 2.25M; the complexing agent MEP (N-methyl-N-ethyl-pyrrolidium bromide) is 0.8M, and the conductive supporting agent (potassium chloride) is 1M; the current density of charge and discharge is 15mA cm -2 Charging time 2h, electrode area 100cm -2 (ii) a The galvanic pile is formed by superposing four groups of sequentially arranged anodes, composite diaphragms and cathodes of the current collector. The cyclic voltammetry curve of the composite membrane zinc-bromine single flow battery is shown in fig. 1, after the battery is subjected to 100 normal charge and discharge cycles, the average coulombic efficiency of the battery is 91.2%, the average voltage efficiency of the battery is 84.8%, and the average energy efficiency of the battery is 77.3%.
As a comparison, a Polyethylene (PE) microporous separator (ZBMM 01 film, baodingboenghuitong New energy science and technology Co., ltd.) without an ion exchange layer was packedThe zinc bromide single flow battery prepared by the applicant is matched to test the battery performance, and the test conditions are as follows: electrolyte concentration: zinc bromide 2.25M; the complexing agent MEP (N-methyl-N-ethyl-pyrrolidium bromide) is 0.8M, and the conductive supporting agent (potassium chloride) is 1M; the current density of charge and discharge is 15mA cm -2 Charging time 2h, electrode area 100cm -2 (ii) a The galvanic pile is formed by overlapping four single batteries which are connected in series and consists of a positive end plate, a current collector, a negative end plate, four groups of positive electrodes, polyethylene (PE) microporous diaphragms and negative electrodes which are sequentially arranged, and the current collector. As shown in fig. 2, after the battery undergoes 16 normal charge and discharge cycles, the average coulombic efficiency of the battery is 86.2%, the average voltage efficiency of the battery is 84.2%, and the average energy efficiency of the battery is 72.5%.
The comparison result shows that after 100 times of normal charge-discharge cycles, the composite diaphragm provided by the invention is still superior to the battery using the PE microporous diaphragm after 16 times of normal charge-discharge cycles, so that the composite diaphragm provided by the invention has very obvious improvement on the charge-discharge performance and the service life of the battery.
Example 2: a preparation method of a composite diaphragm for a flow battery comprises the following steps:
A. the zinc-bromine flow battery microporous membrane is a ZBMM01 membrane produced by Baodingbeihuitong New energy science and technology Limited and cut into 10cm multiplied by 10cm;
B. adding 150g of perfluorosulfonic acid resin and 3500g of high-boiling-point solvent N, N-Dimethylformamide (DMF) into a high-pressure reaction kettle, stirring and heating to 200 ℃, keeping the temperature for 4 hours under the pressure of 1.0MPa, then cooling to room temperature, discharging the solution from the reaction kettle, and preparing perfluorosulfonic acid ion exchange solution through precipitation and filtration; measuring 10ml of perfluorinated sulfonic acid ion exchange solution, adding 1g of sodium dodecyl benzene sulfonate, and uniformly stirring to obtain a coating solution;
C. rolling and coating the coating solution prepared in the step B on one side of the microporous membrane cut in the step A, wherein the rolling and coating amount is 1.5-1.7ml;
D. putting the coated microporous membrane into an oven, heating at 40 ℃ for 120min, taking out and cooling to room temperature;
E. repeating the steps C-D for 3 times to obtain the product.
Example 3: a preparation method of a composite diaphragm for a flow battery comprises the following steps:
A. cutting the microporous diaphragm of the zinc-bromine flow battery into 10cm multiplied by 10cm (the microporous diaphragm of the zinc-bromine flow battery is prepared by mixing 350g of silicon dioxide, 500g of plasticizer (special oil for PE separator), 100g of PE raw material (50 g of UHMWPE with 500 ten thousand molecular weight and 50g of HDPE with 15 ten thousand molecular weight), 30g of color master (such as Polyblack-2778) for absorbing laser energy of 900-1000nm and 20g of antioxidant);
B. adding 200g of sulfonated polysulfone resin and 3000g of high-boiling-point solvent N, N-dimethylacetamide (DMAc) into a high-pressure reaction kettle, stirring and heating to 200 ℃ and keeping the temperature under the pressure of 1.5MPa for 6 hours, then cooling to room temperature, discharging solution from the reaction kettle, and preparing sulfonated polysulfone ion exchange solution through precipitation and filtration; measuring 6ml of sulfonated polysulfone ion exchange solution, adding 0.72g of surfactant containing sodium dodecyl benzene sulfonate, and uniformly stirring to obtain a coating solution;
C. spraying the coating solution prepared in the step B on one side of the microporous membrane cut in the step A, wherein the spraying amount is 1.3ml;
D. putting the coated microporous membrane into an oven, heating at 40 ℃ for 60min, taking out and cooling to room temperature;
E. repeating the steps C-D for 5 times to obtain the product.
Example 4: a preparation method of a composite diaphragm for a flow battery comprises the following steps:
A. cutting the zinc-bromine flow battery microporous membrane into 12cm multiplied by 15cm (the zinc-bromine flow battery microporous membrane is prepared by mixing 300g of silicon dioxide, 350g of plasticizer (PE separator special oil), 320g of PE raw material (UHMWPE 192g with 500 million molecular weight and HDPE 128g with 15 million molecular weight), 20g of color master (such as Polyblack-2778) for absorbing laser energy of 900-1000nm and 10g of antioxidant);
B. adding 200g of perfluorosulfonic acid resin and 3700g of high-boiling-point solvent N, N-Dimethylformamide (DMF) into a high-pressure reaction kettle, stirring and heating to 210 ℃, keeping the temperature under the pressure of 1.1MPa for 2 hours, cooling to room temperature, discharging solution from the reaction kettle, precipitating and filtering to prepare perfluorosulfonic acid ion exchange solution; measuring 20ml of perfluorinated sulfonic acid ion exchange solution, adding 1.6g of sodium dodecyl benzene sulfonate, and uniformly stirring to obtain a coating solution;
C. rolling and coating the coating solution prepared in the step B on one side of the microporous membrane cut in the step A, wherein the rolling and coating amount is 3.8ml;
D. putting the coated microporous membrane into an oven, heating at 50 ℃ for 40min, taking out and cooling to room temperature;
E. repeating the steps C-D for 4 times to obtain the product.
Example 5: a preparation method of a composite diaphragm for a flow battery comprises the following steps:
A. the zinc-bromine flow battery microporous membrane is a ZBMM01 membrane produced by Baoding Baineng New energy science and technology Limited and cut into 10cm multiplied by 20cm;
B. adding 200g of sulfonated polyethersulfone resin and 3800g of high-boiling-point solvent dimethyl sulfoxide into a high-pressure reaction kettle, stirring and heating to 250 ℃ and keeping the temperature under the pressure of 1.2MPa for 5 hours, then cooling to room temperature, discharging the solution from the reaction kettle, and preparing sulfonated polyethersulfone ion exchange solution by precipitation and filtration; measuring 10ml of sulfonated polyether sulfone ion exchange solution, adding 0.8g of sodium dodecyl benzene sulfonate, and uniformly stirring to obtain a coating solution;
C. spraying the coating solution prepared in the step B on one side of the microporous membrane cut in the step A, wherein the spraying amount is 3ml;
D. putting the coated microporous membrane into an oven, heating at 70 ℃ for 20min, taking out and cooling to room temperature;
E. repeating the steps A-D for 2 times to obtain the product.
Example 6: a preparation method of a composite diaphragm for a flow battery comprises the following steps:
A. cutting the zinc-bromine flow battery microporous membrane into 20cm multiplied by 30cm (the zinc-bromine flow battery microporous membrane is prepared by mixing 100g of silicon dioxide, 650g of plasticizer (30% DOP is added into special oil for PE separator), 180g of PE raw material (120 g of UHMWPE with molecular weight of 400 ten thousand and 60g of HDPE with molecular weight of 5 ten thousand), 50g of color master (such as Polyblack-2778) for absorbing laser energy of 900-1000nm and 20g of antioxidant);
B. adding 300g of sulfonated polyethersulfone resin and 3800g of high-boiling-point solvent dimethyl sulfoxide into a high-pressure reaction kettle, stirring and heating to 220 ℃ and keeping the temperature for 3 hours under the pressure of 1.0MPa, then cooling to room temperature, discharging the solution from the reaction kettle, and preparing sulfonated polyethersulfone ion exchange solution by precipitation and filtration; measuring 40ml of sulfonated polyether sulfone ion exchange solution, adding 4g of sodium dodecyl benzene sulfonate, and uniformly stirring to obtain a coating solution;
C. spraying the coating solution prepared in the step B on one side of the microporous membrane cut in the step A, wherein the spraying amount is 9.6ml;
D. putting the coated microporous membrane into an oven, heating at 60 ℃ for 30min, taking out and cooling to room temperature;
E. repeating the steps A-D for 4 times to obtain the product.