CN114573847B

CN114573847B - Ultra-high mechanical strength ultrathin membrane for flow battery and preparation and application thereof

Info

Publication number: CN114573847B
Application number: CN202011374710.2A
Authority: CN
Inventors: 李先锋; 石梦奇; 张华民
Original assignee: Dalian Institute of Chemical Physics of CAS
Current assignee: Dalian Institute of Chemical Physics of CAS
Priority date: 2020-11-30
Filing date: 2020-11-30
Publication date: 2023-01-10
Anticipated expiration: 2040-11-30
Also published as: CN114573847A

Abstract

An ultra-high mechanical strength ultra-thin film for a flow battery and preparation and application thereof are disclosed, the method comprises the following steps: laying a liquid phase raw material dissolved with resin in a device capable of preparing a planar membrane, immersing the liquid phase raw material dissolved with the resin in a liquid phase system containing a cross-linking agent, and standing to form a membrane I; the liquid phase raw material comprises a good solvent of the resin; the liquid phase system comprises a poor solvent A of the resin; transferring the film I into a poor solvent A or a poor solvent B of the resin, and standing to obtain a composite film comprising the film I and a film II; and peeling the membrane II to obtain the ion-conducting membrane. The membrane has ultrahigh mechanical strength, simple preparation method, environment-friendly process, good chemical stability, excellent ion selectivity and good ion conductivity. The ultrathin membrane is beneficial to reducing the internal resistance of the membrane, and is expected to further improve the ionic conductivity of the membrane while maintaining the high ionic selectivity of the membrane.

Description

Ultra-high mechanical strength ultrathin membrane for flow battery and preparation and application thereof

Technical Field

The invention relates to the research field of flow batteries, in particular to application of an ultra-thin film with ultra-high mechanical strength in a flow battery.

Background

The flow battery is a large-scale electrochemical energy storage technology, has the advantages of long cycle life, high safety, mutual independence of power and capacity and the like, can be widely applied to power generation and energy storage of renewable energy sources such as wind energy, solar energy and the like, and realizes large-scale application of the renewable energy sources. Among them, the energy storage technology of the vanadium redox flow battery (VFB) is one of the preferred technologies for large-scale high-efficiency energy storage due to the characteristics of high safety, long service life, large output power and energy storage capacity, good charge-discharge cycle performance, environmental friendliness, etc.

The film is one of key materials of VFB, plays a role in blocking the cross blending of vanadium ions in positive and negative electrolyte and transferring hydrogen ions to form a battery loop, and the performance of the film directly influences the performance of a battery system. An ideal membrane should have high ion selectivity, high ionic conductivity, high chemical stability, and low cost. Currently, the most widely used commercial membrane is the perfluorosulfonic acid ion exchange membrane (Nafion) manufactured by dupont, usa. However, the problems of poor ion selectivity and high price limit the industrial application. The non-fluorine ion exchange membrane becomes a research hotspot due to the advantages of low cost, good thermal stability and mechanical stability, high ion selectivity and the like. But the chemical stability of the membrane is greatly reduced due to the introduction of ion exchange groups. The ion conduction membrane realizes the selective separation of vanadium ions and protons by utilizing a pore size sieving mechanism and a charge exclusion effect, breaks through the limitation of the traditional ion exchange membrane, gets rid of the dependence on ion exchange groups, and fundamentally solves the problem of poor membrane stability caused by the introduction of the ion exchange groups.

Disclosure of Invention

The invention aims to solve the problems of poor selectivity and low conductivity of an all-vanadium redox flow battery membrane, and provides a diffusion-reaction induced phase conversion method for preparing an ultrathin membrane. The membrane has the advantages of simple preparation method, environment-friendly process, excellent ion selectivity and good ion conductivity. The ultrathin membrane is beneficial to reducing the internal resistance of the membrane, and is expected to further improve the ionic conductivity of the membrane while maintaining the high ionic selectivity of the membrane.

In one aspect, the present invention provides a method for preparing an ion-conducting membrane, comprising the steps of:

laying a liquid phase raw material dissolved with resin in a device capable of preparing a planar membrane, immersing the liquid phase raw material dissolved with the resin in a liquid phase system containing a cross-linking agent, and standing to form a membrane I;

the liquid phase raw material comprises a good solvent of the resin;

the liquid phase system comprises a poor solvent A of the resin;

step (2) transferring the film I into a poor solvent A or a poor solvent B of the resin, and standing to obtain a composite film containing the film I and the film II;

and (3) stripping the membrane II to obtain the ion-conducting membrane.

The stripping is generally carried out by conventional physical methods.

Preferably, the poor solvent A is at least one of n-hexane, n-heptane, n-octane, n-pentane and cyclohexane;

the poor solvent B is at least one of water, ethanol, isopropanol or acetone.

Preferably, in the step (1), the mass ratio of the cross-linking agent to the resin is more than or equal to 0.01;

in the liquid phase system, the ratio of the poor solvent A to the crosslinking agent is (0.001-20): 100g/ml.

Preferably, in the step (1), the crosslinking agent is at least one of aromatic organic matters containing acid chloride functional groups;

preferably, the aromatic organic compound containing acyl chloride functional groups is at least one of benzoyl chloride, phthaloyl chloride, isophthaloyl chloride, terephthaloyl chloride, 1,3,5-benzenetricarboxyacyl chloride, phenylacetyl chloride and phenylpropionyl chloride.

Preferably, in the step (1), the good solvent of the resin is at least one of dimethyl sulfoxide (DMSO), N-Dimethylacetamide (DMAC), N-methylpyrrolidone (NMP), and N, N-Dimethylformamide (DMF).

Preferably, in step (1), the resin is polybenzimidazole polymer;

preferably, the concentration of the resin in the liquid phase raw material is 5-60 wt%; the preferred concentration is 10wt% to 20wt%.

The invention also provides the ion-conducting membrane prepared by the preparation method, wherein the membrane thickness is less than or equal to 10 mu m; the film thickness is preferably 5 μm or less.

Preferably, the elongation at break of the film is more than or equal to 18%; the tensile strength is more than or equal to 94MPa; the elastic modulus is more than or equal to 1054MPa; VO (vacuum vapor volume) ₂ ⁺ The penetration rate is less than or equal to 2.65 multiplied by 10 ^-7 cm ² H; the surface resistance is less than or equal to 0.044 omega/cm ² 。

In a further aspect, the present invention provides the use of an ion-conducting membrane as described above in a flow battery.

Preferably, the flow battery comprises an all vanadium flow battery, a zinc/bromine flow battery, a zinc/iodine flow battery, an iron/chromium flow battery, or a vanadium/bromine flow battery.

The ion conducting membrane may be used in flow batteries including, but not limited to, all-vanadium flow batteries, zinc/bromine flow batteries, sodium polysulfide/bromine flow batteries, iron/chromium flow batteries, vanadium/bromine flow batteries, or zinc/cerium flow batteries.

Advantageous effects

1. The invention provides a method for preparing an ultrathin film with ultrahigh mechanical strength, the thickness of the prepared ultrathin film is less than 10 mu m, the mass transfer resistance of the film is greatly reduced, and the ionic conductivity of the film is improved.

2. The invention utilizes a diffusion-reaction induced phase inversion method, on one hand, chemical crosslinking reaction can be carried out between a high molecular polymer and a crosslinking agent to form a polymer crosslinking network, thereby improving the chemical stability of the membrane and ensuring the ultrahigh mechanical strength of the membrane, and on the other hand, a slow solvent-non-solvent exchange process is formed by controlling the diffusion rate of a solvent-non-solvent, thereby improving the compactness of the membrane and further improving the ion selectivity of the membrane.

3. The ultrathin membrane prepared by the invention has the advantages of simple preparation method, obvious improvement on membrane performance, easy amplification and realization of industrialization.

4. The ultrathin film prepared by the invention is applied to the flow battery, has ultrahigh battery performance, synchronously obtains high coulombic efficiency, high voltage efficiency and high energy efficiency, and has very high application value.

5. The ultrathin film prepared by the invention can realize controllable regulation of the appearance and performance of the film by regulating parameters.

Drawings

FIG. 1 is a TEM cross-sectional view of an ultra-thin film with ultra-high mechanical strength

Detailed Description

An ultra-high-mechanical-strength ultra-thin film for flow batteries is prepared from organic high-molecular resin through dissolving in organic solvent, spreading on a flat plate, immersing in the bath A containing cross-linking agent, and transferring to the bath B.

The ion-conducting membrane is prepared by adopting the following steps:

(1) Dissolving organic high molecular resin in an organic solvent, fully stirring for 2-48 h at the temperature of 10-80 ℃ to prepare a uniform blending solution, and then standing for 2-48 h at normal temperature to remove air bubbles in the blending solution;

(2) Pouring the blending solution prepared in the step (1) on one side of a flat plate, volatilizing the solvent for 0-60 s, coating the blending solution on the flat plate by adopting a scraper with the thickness of 5-50 mu m, and then immersing the blending solution into a poor solvent A of resin containing a cross-linking agent for 10 s-100 min at the temperature of-20-70 ℃; then transferring the mixture into a poor solvent B of the resin to be cured into a film. The formed membrane is an ultrathin compact membrane with a double-layer structure of a crosslinking layer and a supporting layer, the crosslinking layer and the supporting layer are compact layers, the thickness of the crosslinking layer is 10-300nm, preferably 10-100nm, and the thickness of the membrane is 1-10 mu m, preferably 1-5 mu m.

Example 1

The ion-conducting membrane is prepared by adopting the following steps:

(1) Dissolving PBI in DMAc, fully stirring for 24h at the temperature of 20 ℃ to prepare a uniform blending solution, and then standing for 24h at normal temperature to remove bubbles in the blending solution; wherein the PBI concentration is 15wt%.

(2) Pouring the blended solution prepared in the step (1) on one side of a flat plate, volatilizing the solvent for 10s, scraping the mixed solution on the flat plate by using a 10-micron scraper, and then immersing the mixed solution into an n-heptane solution containing 1,3,5-benzene tricarbochloride for 10s at the temperature of 20 ℃, wherein each 100mL of n-heptane contains 0.01g of 1,3, 5-benzene tricarbochloride; then transferred to water to be solidified into a film. The formed membrane is an ultrathin compact membrane with a double-layer structure of a cross-linking layer and a supporting layer, the thickness of the cross-linking layer is 100nm, and the membrane thickness is 2 mu m.

Examples 2 to 13

The parameters in Table 1 below were varied and the other conditions were the same as in example 1.

Comparative example 1

A commercially available Nafion212 membrane.

Comparative example 2

The ion-conducting membrane is prepared by the following process:

(2) Pouring the blended solution prepared in the step (1) on one side of a flat plate, volatilizing the solvent for 10s, coating the mixture on the flat plate by a scraper with the thickness of 10 mu m, and then immersing the mixture into n-heptane for 10s at the temperature of 20 ℃; then transferred to water and could not be formed into a film because the thickness was too thin by knife application.

Comparative example 3

The ion-conducting membrane is prepared by the following process:

(2) Pouring the blending solution prepared in the step (1) on one side of a flat plate, volatilizing the solvent for 10s, coating the blending solution on the flat plate by a scraper with the thickness of 60 mu m, and then immersing the blending solution into n-heptane for 10s at the temperature of 20 ℃; then transferred to water to be solidified into a film. The film formed was a porous film having a porosity of 40% and a film thickness of 10 μm.

Comparative example 4

The ion-conducting membrane is prepared by adopting the following steps:

(2) Pouring the blended solution prepared in the step (1) on one side of a flat plate, volatilizing the solvent for 10s, coating the mixture on the flat plate by a 150-micron scraper, and then immersing the mixture in water at the temperature of 20 ℃ to be solidified into a film. The film formed was a porous film having a porosity of 70% and a film thickness of 52 μm.

(3) Immersing the PPBI porous membrane prepared in the step (2) into an n-heptane solution containing 1,3,5-benzene tricarboxychloride at a temperature of 20 ℃ for 48h, wherein each 100mL of the n-heptane solution contains 0.01g of 1,3,5-benzene tricarboxychloride. The film formed was a fully crosslinked, dense film with a film thickness of 52 μm.

TABLE 1 preparation parameters of ultra-high mechanical strength ultra-thin films

TABLE 2 Properties of ultra-high mechanical Strength ultra-thin films

	CE(％)	VE(％)	EE(％)	Elongation at Break (%)	Tensile strength (Mpa)	Modulus of elasticity (Mpa)
							Example 1	99.05	93.34	92.45	18	118	2863
Example 2	97.34	92.52	90.06	25	94	3498
							Example 3	99.13	91.38	90.58	19	122	2884
Example 4	99.28	90.81	90.16	17	169	2462
							Example 5	98.67	91.56	90.34	19	98	2763
Example 6	99.08	93.21	92.35	20	121	2813
							Example 7	99.12	91.38	90.58	22	116	2834
Example 8	99.14	91.36	90.57	21	135	2846
							Example 9	99.19	91.12	90.38	19	129	2816
Example 10	99.25	90.89	90.21	23	127	2889
							Example 11	99.31	90.77	90.14	22	129	2876
Example 12	99.42	90.62	90.09	38	215	1489
							Example 13	99.67	89.64	89.34	46	351	1054
Comparative example 1	94.35	90.68	85.56	343	32	266
							Comparative example 2	—	—	—	—	—	—
Comparative example 3	76.38	90.86	69.40	11	21	106
							Comparative example 4	98.86	83.46	82.51	10	107	1796

An ultrathin membrane assembled vanadium redox flow battery with ultrahigh mechanical strength prepared by a diffusion-reaction induced phase conversion method, wherein a catalyst layer is an activated carbon felt, a bipolar plate is a graphite plate, and the effective area of the membrane is 48cm ² The current density is 80mA.cm ^-2 The concentration of vanadium ions in the electrolyte is 1.50mol L ^-1 ，H ₂ SO ₄ The concentration is 3mol L ^-1 . From the view point of battery performance, the coulombic efficiency, the voltage efficiency and the energy efficiency of the embodiment are all higher than those of the comparative example, which shows that the composite membrane can realize the synchronous improvement of the ion selectivity and the ion conductivity and is suitable for a flow battery system. Comparative example 1 has low coulombic efficiency and poor ion selectivity. Comparative example 2 did not cause a crosslinking reaction and an ultra-thin film could not be prepared. Comparative example 3 no crosslinking reaction occurred, the poor solvent a affected the solvent-non-solvent exchange rate during the film formation process, further affected the film's appearance, formed the porous film, coulombic inefficiency, the ion selectivity of the film is poor. Comparative example 4 a PBI porous membrane was prepared by the immersion phase inversion method and then immersed in a poor solvent a containing a crosslinking agent, and the membrane prepared by this method was a completely crosslinked membrane, and the prepared membrane was thick and the time required for the crosslinking reaction was longThe formed membrane has low voltage efficiency and low ionic conductivity. From the mechanical properties, the examples have high tensile strength, high modulus of elasticity and high elongation at break simultaneously. This is caused by the double-layer structure of the cross-linked layer and the support layer of the ion-conductive membrane.

Selection of stable VO in air ²⁺ Permeability of comparative example and example were evaluated for ion selectivity. The test comprises two chambers separated by a membrane with an effective area of 3 × 3, the left chamber is filled with 80mL1.5mol L ^-1 VOSO ₄ +3.0mol L ^-1 H ₂ SO ₄ The right chamber of the solution is filled with 80mL1.5mol L ^-1 MgSO ₄ +3.0mol L ^-1 H ₂ SO ₄ And (3) solution. In the test process, the solutions in the left and right chambers are simultaneously stirred to reduce concentration polarization, 3mL of sample solution is taken out from the right chamber at intervals of 24 hours in the test process, and 3mL1.5mol L of sample solution is added into the right chamber while the sample is taken out ^-1 MgSO ₄ +3.0mol L ^-1 H ₂ SO ₄ The solution was added to keep the volume of the solution constant.

The sheet resistance can be evaluated for the ionic conductivity of comparative examples and examples, and measured by an ac impedance tester. The test cell is divided into two chambers by a circular membrane with the effective diameter of 1cm, and the chambers are filled with 3.0mol L ^-1 H ₂ SO ₄ The solution, the conductivity of which is measured. Test cell, comparative example and example before testing at 3.0mol L ^-1 H ₂ SO ₄ Soaking in the solution.

The vanadium ion permeability and sheet resistance test results are listed in table 3. The results show that the vanadium resistance of the embodiment is far greater than that of the comparative example, and the surface resistance is far less than that of the comparative example, because the ultrathin membrane prepared by the diffusion-reaction induced phase conversion method can greatly reduce the internal resistance of the membrane, improve the ionic conductivity of the membrane, and the high ionic selectivity of the membrane is ensured by the chemical cross-linked polymer chain formed by the cross-linking reaction between the high molecular polymer and the cross-linking agent.

TABLE 3 vanadium ion permeability and sheet resistance of ultra-high mechanical Strength ultra-thin films

Claims

1. A method of making an ion-conducting membrane, comprising the steps of:

(2) Pouring the blending solution prepared in the step (1) on one side of a flat plate, volatilizing the solvent for 0-60 s, coating the blending solution on the flat plate by adopting a scraper with the thickness of 5-50 microns, and then immersing the blending solution into a poor solvent A of resin containing a cross-linking agent at the temperature of-20-70 ℃ for 10 s-100 min; then transferring the mixture into a poor solvent B of resin to be cured into a film;

the poor solvent A is at least one of n-hexane, n-heptane, n-octane, n-pentane and cyclohexane;

the poor solvent B is at least one of water, ethanol, isopropanol or acetone;

the cross-linking agent is at least one of aromatic organic matters containing acid chloride functional groups;

the organic solvent is at least one of dimethyl sulfoxide, dimethylacetamide, N-methylpyrrolidone and N, N-dimethylformamide;

the resin is polybenzimidazole polymer.

2. The method of claim 1, wherein:

the mass ratio of the cross-linking agent to the resin is more than or equal to 0.01;

the ratio of the poor solvent A to the crosslinking agent is 0.001-20: 100g/ml.

3. The method of claim 1, wherein:

the aromatic organic matter containing acyl chloride functional groups is at least one of benzoyl chloride, phthaloyl chloride, isophthaloyl chloride, terephthaloyl chloride, 1,3,5-benzenetricarboxychloride, phenylacetyl chloride and phenylpropionyl chloride.

4. The method of claim 1, wherein:

the concentration of the resin in the liquid phase raw material is 5wt% -60 wt%.

5. The method of claim 1, wherein: the concentration of the resin in the liquid phase raw material is 10wt% -20 wt%.

6. An ion-conducting membrane obtainable by the process of any one of claims 1 to 5, wherein: the film thickness is less than or equal to 10 mu m.

7. The ion-conducting membrane according to claim 6, wherein the membrane thickness is ≦ 5 μm.

8. An ion-conducting membrane according to claim 6 or 7, characterized in that: the elongation at break of the film is more than or equal to 18 percent; the tensile strength is more than or equal to 94MPa; the elastic modulus is more than or equal to 1054MPa; VO (volatile organic compound) ₂ ⁺ Penetration rate is less than or equal to 2.65 multiplied by 10 ^-7 cm ² H; the surface resistance is less than or equal to 0.044 omega/cm ² 。

9. Use of the ion-conducting membrane of claim 8 in a flow battery.

10. The use of claim 9, wherein the flow battery comprises an all vanadium flow battery, a zinc/bromine flow battery, a zinc/iodine flow battery, an iron/chromium flow battery, or a vanadium/bromine flow battery.