CN118919789A - Preparation method of diaphragm assembly for vanadium battery - Google Patents

Abstract

The present invention relates to the technical field of vanadium liquid flow battery diaphragm, and discloses a method for preparing a diaphragm assembly for vanadium battery, which comprises at least the following steps: pouring cross-linked polyvinyl pyrrolidone (PVPP) powder into a solvent, preparing a PVPP suspension, spraying the PVPP suspension on both sides of the diaphragm by ultrasonic spraying equipment and drying, hot pressing the dried diaphragm, and maintaining the pressure for a period of time, cooling after maintaining the pressure to obtain a PVPP-modified diaphragm, and stacking the PVPP-modified diaphragm between two microporous membranes to form a diaphragm assembly with a three-layer membrane structure. The diaphragm assembly for vanadium battery prepared by the present invention can better meet the requirements of high ion selectivity, high ion conductivity and high stability required by the diaphragm of vanadium battery.

Description

A method for preparing a diaphragm assembly for a vanadium battery

Technical Field

The invention relates to the technical field of diaphragm for all-vanadium liquid flow battery, and in particular to a method for preparing a diaphragm assembly for a vanadium battery.

Background Art

As a large-scale energy storage device, flow batteries have the function of shaving peaks and filling valleys to maintain the stability of the power grid. Due to the characteristics of high safety, long life, and high energy conversion efficiency, many flow battery energy storage power stations have been built and applied. Among them, all-vanadium flow batteries (abbreviated as vanadium batteries) are one of the most mature and widely used flow batteries. Vanadium batteries are mainly composed of electrode materials, bipolar plates, electrolytes, and diaphragms. Among them, the diaphragm, as one of the core components of vanadium batteries, should have excellent ion conductivity, high ion selectivity, excellent mechanical and chemical stability, and low cost.

Commercial porous membranes are widely used in water treatment and other fields, but they have low ion conductivity when used in vanadium batteries, while anion exchange membranes generally require a complex preparation process and have low coulombic efficiency. At present, perfluorosulfonic acid membranes have become the most widely used membranes for vanadium batteries due to their excellent electrochemical properties and chemical stability, but the ion selectivity of such membranes is also not high, which is manifested as the mutual connection of positive and negative vanadium ions, which ultimately leads to capacity decay. Therefore, it is necessary to modify such membranes, but the effect is minimal. Some of them damage the membrane structure (such as organic or inorganic blending), some add complex modification processes (such as surface chemical grafting, porous matrix filling, etc.), and some can meet the requirements in the early stage of the battery but cannot meet the long-term cycle of vanadium batteries (such as physical modification of the surface that is not resistant to electrolyte erosion and some soluble positively charged polymer additives that have an inert effect on the electrode, etc.). Finding low-cost, high ion selectivity, and high ion conductivity vanadium battery membranes and their modification methods has become one of the hot topics in the field of vanadium batteries.

Summary of the invention

In view of the above problems or shortcomings, the present invention provides a method for preparing a diaphragm assembly for a vanadium battery. The technical solution adopted by the present invention is as follows:

A method for preparing a diaphragm assembly for a vanadium battery comprises at least the following steps:

Step S1: Weigh 4-30 parts by weight of cross-linked polyvinyl pyrrolidone powder and pour it into 70-96 parts by weight of solvent, disperse it by ultrasonic and stir it to prepare a cross-linked polyvinyl pyrrolidone suspension with a mass fraction of 4%-30%;

Step S2: spraying the cross-linked polyvinyl pyrrolidone suspension on both sides of the diaphragm using an ultrasonic spraying device, and drying on a heating platform of the ultrasonic spraying device;

Step S3: hot pressing the dried diaphragm in step S2, maintaining the pressure for a period of time, and cooling to 25° C. to obtain a cross-linked polyvinyl pyrrolidone-modified diaphragm;

Step S4: stacking the cross-linked polyvinyl pyrrolidone-modified diaphragm between two microporous membranes of the same length and width to form a diaphragm assembly with a three-layer membrane structure.

Preferably, the particle size of the cross-linked polyvinyl pyrrolidone powder in step S1 is 0.1-2 μm.

Preferably, the solvent in step S1 is at least one of deionized water, anhydrous ethanol, anhydrous propanol, dimethyl sulfoxide, N,N-dimethylformamide, and N,N-dimethylacetamide.

Preferably, the spraying parameters of the ultrasonic spraying equipment in step S2 are: nozzle atomization radius 5-20 mm, nozzle movement speed 5-30 mm/s, spray flow rate 1-10 mL/min, and heating table temperature 90-140°C.

Preferably, the membrane in step S2 is a fluorinated sulfonic acid membrane.

Preferably, in step S3, the hot pressing temperature is 120-170° C., and the holding time is 10-60 min.

Preferably, the microporous membrane in step S4 is at least one of a polyethylene membrane, a polypropylene membrane, a polyethersulfone membrane, a polyvinylidene fluoride membrane, a polyacrylonitrile membrane, and a polyamide membrane.

Preferably, in step S4, the pore size of the microporous membrane is 0.45-2 μm, and the thickness is 50-100 μm.

The beneficial effects of the present invention include at least:

1. Cross-linked polyvinyl pyrrolidone (PVPP) can be obtained by the repolymerization of polyvinyl pyrrolidone. It contains a positively charged pyrrole ring structure, has good vanadium barrier properties, and can reduce the shuttling of vanadium;

2. Unlike some soluble positively charged polymer additives (such as polyvinyl pyrrolidone), PVPP is granular. The PVPP modified layer after hot pressing can form porous channels, which does not affect proton transmission. PVPP is insoluble in water, acidic and alkaline solutions, that is, it cannot be dissolved by vanadium battery electrolyte, and will not act on the electrode to make the electrode inert. The activity of the electrode can be maintained when the battery is cycled for a long time;

3. In the three-layer membrane assembly structure, the microporous membrane does not affect the transmission of active ions, but can effectively reduce the scouring and disturbance of the electrolyte on the PVPP-modified diaphragm, so that PVPP adheres to the diaphragm for a long time, and finally enables the diaphragm assembly to maintain excellent ion conductivity and high ion selectivity for a long time.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a flow chart of a method for preparing a diaphragm assembly for a vanadium battery according to the present invention;

FIG2 is a schematic structural diagram of a diaphragm assembly for a vanadium battery according to the present invention;

Figure numerals: 1. microporous membrane; 2. PVPP-modified diaphragm.

DETAILED DESCRIPTION

Referring to Figure 1, cross-linked polyvinyl pyrrolidone (PVPP) powder is poured into a solvent to prepare a PVPP suspension, and the PVPP suspension is sprayed on both sides of the diaphragm using an ultrasonic spraying device. The dried diaphragm is hot-pressed and maintained for a period of time, and then cooled to 25°C to obtain a PVPP-modified diaphragm. The PVPP-modified diaphragm is stacked between two microporous membranes to form a diaphragm assembly with a three-layer membrane structure, as shown in Figure 2, with a PVPP-modified diaphragm 2 in the middle and microporous membranes 1 on both sides.

Embodiment 1: comprising the following steps:

Step S1: Weigh 4 g of cross-linked polyvinyl pyrrolidone (PVPP) powder with a particle size of 0.1 μm, pour it into 96 g of deionized water, and stir after ultrasonic dispersion to prepare a PVPP suspension with a mass fraction of 4%;

Step S2: using ultrasonic spraying equipment, setting the spraying parameters as follows: nozzle atomization radius 20 mm, nozzle movement speed 5 mm/s, spray flow rate 10 mL/min, heating table temperature control 90°C, spraying the PVPP suspension on both sides of the perfluorosulfonic acid diaphragm, and using the built-in heating table to dry while spraying;

Step S3: hot pressing the dried perfluorosulfonic acid membrane at a temperature of 120° C., maintaining the pressure for 60 minutes, and cooling to 25° C. to obtain a PVPP-modified perfluorosulfonic acid membrane;

Step S4: stacking the PVPP-modified perfluorosulfonic acid diaphragm between two polyethylene microporous membranes with a pore size of 0.45 μm and a thickness of 50 μm to form a diaphragm assembly with a three-layer membrane structure.

Embodiment 2: comprising the following steps:

Step S1: weigh 8 g of cross-linked polyvinyl pyrrolidone (PVPP) powder with a particle size of 0.3 μm, pour it into 92 g of anhydrous ethanol, and stir after ultrasonic dispersion to prepare a PVPP suspension with a mass fraction of 8%;

Step S2: using ultrasonic spraying equipment, setting the spraying parameters as follows: nozzle atomization radius 17 mm, nozzle movement speed 14 mm/s, spray flow rate 8 mL/min, heating table temperature control 100°C, spraying the PVPP suspension on both sides of the partially fluorinated sulfonic acid diaphragm, and using the built-in heating table to dry while spraying;

Step S3: hot-pressing the dried partially fluorinated sulfonic acid membrane at a temperature of 130° C., maintaining the pressure for 50 minutes, and cooling to 25° C. to obtain a PVPP-modified partially fluorinated sulfonic acid membrane;

Step S4: stacking the PVPP-modified partially fluorinated sulfonic acid membrane between two polypropylene microporous membranes with a pore size of 0.6 μm and a thickness of 60 μm to form a three-layer membrane structure membrane assembly.

Embodiment 3: comprising the following steps:

Step S1: weigh 12 g of cross-linked polyvinyl pyrrolidone (PVPP) powder with a particle size of 0.5 μm, pour it into 88 g of anhydrous propanol, and stir after ultrasonic dispersion to prepare a PVPP suspension with a mass fraction of 12%;

Step S2: using ultrasonic spraying equipment, setting the spraying parameters as follows: nozzle atomization radius 14 mm, nozzle movement speed 18 mm/s, spray flow rate 6.5 mL/min, heating table temperature control 110°C, spraying the PVPP suspension on both sides of the partially fluorinated sulfonic acid diaphragm, and using the built-in heating table to dry while spraying;

Step S3: hot-pressing the dried partially fluorinated sulfonic acid membrane at a temperature of 135° C., maintaining the pressure for 40 minutes, and cooling to 25° C. to obtain a PVPP-modified partially fluorinated sulfonic acid membrane;

Step S4: stacking the partially fluorinated sulfonic acid diaphragm modified by PVPP between a polyethersulfone and a polyvinylidene fluoride microporous membrane with a pore size of 0.8 μm and a thickness of 70 μm to form a diaphragm assembly with a three-layer membrane structure.

Embodiment 4: comprising the following steps:

Step S1: weigh 16 g of cross-linked polyvinyl pyrrolidone (PVPP) powder with a particle size of 0.6 μm, pour it into 84 g of N,N-dimethylacetamide, and stir after ultrasonic dispersion to prepare a PVPP suspension with a mass fraction of 16%;

Step S2: using ultrasonic spraying equipment, setting the spraying parameters as follows: nozzle atomization radius 12 mm, nozzle movement speed 20 mm/s, spray flow rate 5.5 mL/min, heating table temperature control 120°C, spraying the PVPP suspension on both sides of the perfluorosulfonic acid diaphragm, and using the built-in heating table to dry while spraying;

Step S3: hot pressing the dried perfluorosulfonic acid membrane at a temperature of 140° C., maintaining the pressure for 30 minutes, and cooling to 25° C. to obtain a PVPP-modified perfluorosulfonic acid membrane;

Step S4: stacking the PVPP-modified perfluorosulfonic acid diaphragm between two polyethersulfone microporous membranes with a pore size of 1 μm and a thickness of 80 μm to form a diaphragm assembly with a three-layer membrane structure.

Embodiment 5: comprising the following steps:

Step S1: weigh 20 g of cross-linked polyvinyl pyrrolidone (PVPP) powder with a particle size of 1 μm, pour it into 80 g of dimethyl sulfoxide, and stir after ultrasonic dispersion to prepare a PVPP suspension with a mass fraction of 20%;

Step S2: using ultrasonic spraying equipment, setting the spraying parameters as follows: nozzle atomization radius 9 mm, nozzle movement speed 22 mm/s, spray flow rate 4.5 mL/min, heating table temperature control 125°C, spraying the PVPP suspension on both sides of the partially fluorinated sulfonic acid diaphragm, and using the built-in heating table to dry while spraying;

Step S3: hot-pressing the dried partially fluorinated sulfonic acid membrane at a temperature of 150° C., maintaining the pressure for 20 minutes, and cooling to 25° C. to obtain a PVPP-modified partially fluorinated sulfonic acid membrane;

Step S4: stacking the PVPP-modified partially fluorinated sulfonic acid membrane between two polyvinylidene fluoride microporous membranes with a pore size of 1.2 μm and a thickness of 85 μm to form a three-layer membrane structure membrane assembly.

Embodiment 6: comprising the following steps:

Step S1: weigh 25 g of cross-linked polyvinyl pyrrolidone (PVPP) powder with a particle size of 1.5 μm, pour it into 75 g of N,N-dimethylformamide, and stir after ultrasonic dispersion to prepare a PVPP suspension with a mass fraction of 25%;

Step S2: using ultrasonic spraying equipment, setting the spraying parameters as follows: nozzle atomization radius 7 mm, nozzle movement speed 26 mm/s, spray flow rate 2.5 mL/min, heating table temperature control 130°C, spraying the PVPP suspension on both sides of the perfluorosulfonic acid diaphragm, and using the built-in heating table to dry while spraying;

Step S3: hot pressing the dried perfluorosulfonic acid membrane at a temperature of 160° C., maintaining the pressure for 15 minutes, and cooling to 25° C. to obtain a PVPP-modified perfluorosulfonic acid membrane;

Step S4: stacking the PVPP-modified perfluorosulfonic acid diaphragm between two polyacrylonitrile microporous membranes with a pore size of 1.6 μm and a thickness of 90 μm to form a diaphragm assembly with a three-layer membrane structure.

Embodiment 7: comprising the following steps:

Step S1: weigh 30 g of cross-linked polyvinyl pyrrolidone (PVPP) powder with a particle size of 2 μm, pour it into 70 g of deionized water, and stir after ultrasonic dispersion to prepare a PVPP suspension with a mass fraction of 30%;

Step S2: using ultrasonic spraying equipment, setting the spraying parameters as follows: nozzle atomization radius 5 mm, nozzle movement speed 30 mm/s, spray flow rate 1 mL/min, heating table temperature control 140°C, spraying the PVPP suspension on both sides of the perfluorosulfonic acid diaphragm, and using the built-in heating table to dry while spraying;

Step S3: hot pressing the dried perfluorosulfonic acid membrane at a temperature of 170° C., maintaining the pressure for 10 minutes, and cooling to 25° C. to obtain a PVPP-modified perfluorosulfonic acid membrane;

Step S4: stacking the PVPP-modified perfluorosulfonic acid diaphragm between two polyamide microporous membranes with a pore size of 2 μm and a thickness of 100 μm to form a diaphragm assembly with a three-layer membrane structure.

Comparative Example 1: A blank perfluorosulfonic acid diaphragm is stacked between two polyethersulfone microporous membranes with a pore size of 1 μm and a thickness of 80 μm to form a diaphragm assembly with a three-layer membrane structure.

Comparative Example 2: The preparation process is the same as that of Example 4, except that in step S1, soluble polyvinyl pyrrolidone (PVP) is used instead of cross-linked polyvinyl pyrrolidone (PVPP).

Comparative Example 3: The preparation process is consistent with that of Example 4, except that step S4 is not performed, that is, microporous membranes are not placed on both sides of the polymer-modified diaphragm.

The diaphragm assemblies made in Examples 1 to 7 and Comparative Examples 1 to 3 were assembled on a battery stack for testing, and the coulombic efficiency, voltage efficiency, and energy efficiency at the 10th and 1000th cycles were tested and recorded under the same test conditions. The test results are shown in Table 1:

Table 1 Battery performance test table of battery stack

As shown in Table 1, compared with Comparative Example 1, the coulombic efficiency, energy efficiency and voltage efficiency of the stack in Examples 1 to 7 are higher after the 10th cycle and the 1000th cycle of the initial test. This is because cross-linked polyvinyl pyrrolidone (PVPP) can be obtained by repolymerization of polyvinyl pyrrolidone, and also contains a positively charged pyrrole ring structure, which has good vanadium resistance and can reduce the shuttling of vanadium. Compared with Comparative Example 2, the coulombic efficiency, energy efficiency and voltage efficiency of the stack in Example 4 are more stable after 1000 cycles. This is because unlike some soluble positively charged polymer additives (such as polyvinyl pyrrolidone), PVPP is granular, and the PVP after hot pressing is The P modified layer can form a porous channel without affecting the proton transport, and PVPP is insoluble in water and acidic and alkaline solutions, that is, it cannot be dissolved by the vanadium battery electrolyte, and cannot act on the electrode to make the electrode inert, so the activity of the electrode is maintained when the battery is cycled for a long time; compared with the comparative example 3, the ionic efficiency, energy efficiency and voltage efficiency of the battery stack in Example 4 are more stable after 1000 cycles. This is because in the diaphragm component structure of the three-layer membrane, the microporous membrane does not affect the transmission of active ions, but can effectively reduce the scouring and disturbance of the electrolyte on the PVPP-modified diaphragm, so that the PVPP adheres to the diaphragm for a long time, and finally the diaphragm component maintains excellent ion conductivity and high ion selectivity for a long time.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims (8)

1. The preparation method of the diaphragm component for the vanadium battery is characterized by comprising the following steps of: at least comprises the following steps:

Step S1: weighing 4-30 parts by mass of crosslinked polyvinylpyrrolidone powder, pouring the powder into 70-96 parts by mass of solvent, and stirring after ultrasonic dispersion to prepare a crosslinked polyvinylpyrrolidone suspension with the mass fraction of 4% -30%;

Step S2: spraying the cross-linked polyvinylpyrrolidone suspension on two sides of the diaphragm by adopting ultrasonic spraying equipment, and drying on a heating table of the ultrasonic spraying equipment;

Step S3: performing hot pressing on the membrane dried in the step S2, maintaining the pressure for a period of time, and cooling to 25 ℃ to obtain a crosslinked polyvinylpyrrolidone modified membrane;

Step S4: the membrane component with a three-layer membrane structure is formed by stacking the cross-linked polyvinylpyrrolidone modified membrane between two microporous membranes with the same length and width.

2. The method for preparing the diaphragm assembly for the vanadium battery according to claim 1, wherein the method comprises the following steps: the particle size of the crosslinked polyvinylpyrrolidone powder in the step S1 is 0.1-2 μm.

3. The method for preparing the diaphragm assembly for the vanadium battery according to claim 1, wherein the method comprises the following steps: the solvent in the step S1 is one of deionized water, absolute ethyl alcohol, absolute propyl alcohol, dimethyl sulfoxide, N-dimethylformamide and N, N-dimethylacetamide.

4. The method for preparing the diaphragm assembly for the vanadium battery according to claim 1, wherein the method comprises the following steps: the spraying parameters of the ultrasonic spraying device in the step S2 are as follows: the atomizing radius of the nozzle is 5-20 mm, the moving speed of the nozzle is 5-30 mm/s, the spraying flow is 1-10 ml/min, and the temperature of the heating table is 90-140 ℃.

5. The method for preparing the diaphragm assembly for the vanadium battery according to claim 1, wherein the method comprises the following steps: the membrane in the step S2 is a fluorinated sulfonic acid membrane.

6. The method for preparing the diaphragm assembly for the vanadium battery according to claim 1, wherein the method comprises the following steps: and in the step S3, the hot pressing temperature is 120-170 ℃, and the pressure maintaining time is 10-60 min.

7. The method for preparing the diaphragm assembly for the vanadium battery according to claim 1, wherein the method comprises the following steps: the microporous membrane in the step S4 is one of a polyethylene membrane, a polypropylene membrane, a polyether sulfone membrane, a polyvinylidene fluoride membrane, a polyacrylonitrile membrane and a polyamide membrane.

8. The method for preparing the diaphragm assembly for the vanadium battery according to claim 1, wherein the method comprises the following steps: and in the step S4, the pore diameter of the microporous membrane is 0.45-2 mu m, and the thickness of the microporous membrane is 50-100 mu m.