Application of a metal-organic dense separation membrane in zinc-based flow batteries

Abstract

The present invention discloses an application of a metal-organic dense separation membrane in a zinc-based liquid flow battery, which has a regulating effect on the zinc deposition morphology and can alleviate the generation of zinc dendrites. The separation membrane surface has a metal coordination layer. During the battery operation, metal ions interact with zincate, which can regulate the zinc deposition morphology on the electrode surface. Furthermore, the separation membrane surface has a concave-convex stripe structure, has good mechanical properties, and provides space for zinc deposition at the interface between the diaphragm and the electrode, so it can operate normally at high surface capacity and improve conductivity.

Description

Technical Field

[0001] The invention belongs to the field of liquid flow batteries, and in particular relates to the application of a metal-organic dense separation membrane in a zinc-based liquid flow battery. Background Art

[0002] In today's society, secondary batteries are an indispensable device in people's daily lives. Large-scale energy storage batteries such as flow batteries and portable batteries such as lithium-ion batteries play an important role in energy storage and other fields. However, lithium-ion batteries have problems such as high prices, flammability and potential dangers. On this basis, researchers have gradually paid attention to zinc-based secondary batteries with zinc as the negative electrode.

[0003] Zinc is high in the earth's crust, so its cost is low; at the same time, its redox process is a two-electron transfer process, which can increase the energy density of the battery; and zinc is used in aqueous secondary batteries, reducing the threat of flammable explosions in the electrolyte. However, similar to the problem of lithium dendrites when lithium is used as an anode, zinc is prone to produce zinc dendrites during the charging and discharging process due to uneven ion concentration and electric field distribution, which pierces the diaphragm, causing internal short circuits and reducing battery life. Methods to alleviate zinc dendrites are generally divided into electrolyte modification, electrode modification, and diaphragm modification. At present, a large amount of research work is concentrated on the first two: electrolyte modification usually uses additives to adjust the solvation environment of zinc ions in the electrolyte, but it is easy to cause the electrolyte conductivity to decrease, which is not conducive to ion transmission; electrode modification is to perform surface coating and other modifications, which can improve the zinc deposition process, but it is easy to increase the internal electron transfer resistance of the battery. Summary of the invention

[0004] In order to solve the above technical problems, the present invention aims to provide an application of a metal-organic dense separation membrane in a zinc-based liquid flow battery. The metal-organic interface layer has a regulating effect on the zinc deposition morphology and can alleviate the generation of zinc dendrites.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] The preparation of metal-organic dense separation membrane is divided into a phase inversion process and a curing process. In the phase inversion process, the functional groups in the organic polymer resin coordinate with the metal ions in the phase inversion reaction liquid to form a metal-organic polymer (activator) with a metal coordination layer on the surface. The metal ions are desolvated to produce free solvents (inhibitors). When the activator and the inhibitor are distributed in a certain pattern on the surface of the organic polymer resin, uneven linear stripes will be generated on the membrane surface. Further in the curing process, the membrane is cured and formed to form this special morphology of metal-organic dense separation membrane.

[0007] The specific preparation steps are as follows:

[0008] (1) dissolving an organic polymer resin in an organic solvent, stirring the organic polymer resin in an organic solvent at a temperature of 10 to 50° C. for 2 to 48 hours to obtain a casting solution. The organic polymer resin is one or more of polyphenylquinoxaline, sulfonated polysulfone, and polybenzimidazole; the organic solvent is one or more of N,N'-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), dimethylformamide (DEM); the mass fraction of the organic polymer resin in the organic solvent is 10wt% to 30wt%, preferably 15 to 20wt%.

[0009] (2) Dissolve the metal chloride in an organic solvent and stir evenly to obtain a homogeneous phase conversion solution. The organic solvent is one or more of N, N'-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), dimethylformamide (DEM); the metal salt is one or more of nickel salt, copper salt, manganese salt or silver salt; the organic solvent is consistent with that in (1); the concentration of the metal salt is 1 to 2.5 mol L -1 ; When the organic solvent in step (1) and step (2) is DMAc, the metal salt is a copper salt.

[0010] (3) Scrape the casting solution prepared in (1) onto a glass plate and immerse it in the phase conversion solution prepared in (2) to obtain a film precursor having a metal-organic interface layer. The coating thickness is 50 to 500 μm, preferably 100 to 200 μm; and the phase conversion time is 0.5 to 4 hours.

[0011] (4) Transferring the film precursor obtained in (3) to a poor solvent for the resin and curing it into a film. The poor solvent for the resin is one or more of water, ethanol, acetone, acetonitrile, and isopropanol; the curing liquid temperature is 15 to 30° C.; and the curing time is 4 minutes to 24 hours, preferably 10 to 24 hours.

[0012] One side surface of the metal-organic dense separation membrane has a concave-convex band-shaped undulating stripe structure. When applied to a zinc-based liquid flow battery, the side surface of the metal-organic dense separation membrane with the undulating stripes faces the negative electrode of the battery.

[0013] The zinc-based liquid flow battery includes zinc-iron liquid flow battery, zinc-bromine liquid flow battery, zinc-iodine liquid flow battery, and zinc-nickel liquid flow battery.

[0014] Beneficial results of the present invention: Beneficial effects of the present invention The metal-organic dense separation membrane with a concave-convex stripe structure prepared by the present invention has good mechanical properties.

[0015] 1. The metal-organic dense separation membrane prepared by the phase transformation process and the curing process of the present invention has a metal coordination layer on its surface. During the operation of the battery, the metal ions interact with the zincate, which can regulate the zinc deposition morphology on the electrode surface and significantly alleviate the generation of zinc dendrites.

[0016] 2. The metal-organic dense separation membrane with a concave-convex stripe structure prepared by the present invention has good mechanical properties and provides space for zinc deposition at the interface between the diaphragm and the electrode, so it can operate normally under high surface capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The surface morphologies of Comparative Example 4 (a) and Example 1 (b) were photographed at 200 μm using an optical microscope.

[0018] Figure 2 Cross-sectional SEM images of Comparative Example 4(b) and Example 1(a).

[0019] Figure 3 Comparative Example 3, Example 1, Comparative Example 1 Preparation of separation membrane at 160 mAh mA·em -2 and 80mA·cm -2 Comparison of cycling stability of zinc symmetric flow batteries at different current densities.

[0020] Figure 4 Comparative SEM images of zinc deposition morphology of separation membranes prepared in Comparative Example 2 (a), Example 2 (b), Comparative Example 3 (c) and Example 1 (d) at the end of charging of alkaline zinc symmetric flow batteries. DETAILED DESCRIPTION

[0021] The following examples are provided to further illustrate the present invention, but are not intended to limit the scope of the present invention.

[0022] Example 1

[0023] 12g polybenzimidazole (PBI) was dissolved in 72g DMAc and stirred at 25°C for 12 hours to obtain a 17wt% casting solution. 170.5g cupric chloride dihydrate was dissolved in 500mL DMAc and stirred to obtain a 2mol / L phase conversion solution. The casting solution was scraped onto a glass plate with a scraping thickness of 100μm, and the glass plate was immersed in a 25°C phase conversion solution for 1h to obtain Cu-PBI. The glass plate loaded with Cu-PBI was placed in a water curing solution and cured for 2h to obtain a metal-organic dense separation membrane.

[0024] The above separation membrane is used to assemble a zinc-based liquid flow symmetrical battery, wherein the electrode is activated carbon felt, the bipolar plate is a graphite plate, and the membrane effective area is 9 cm 2The positive and negative electrolytes were both 0.2 mol / L zinc oxide and 3.8 mol / L sodium hydroxide, and the volumes were the same, 300 ml each. The positive and negative electrodes were pumped with magnetic pumps at a current density of 80 mA cm -2 The stability test of the zinc symmetric flow battery was carried out under the conditions of charging for 2 hours and discharge cut-off voltage of -0.1V.

[0025] Table 1. Preparation parameters and membrane structures of various examples (preparation parameters are the same as those of Example 1 unless otherwise specified)

[0026]

[0027] Table 2. Application of each embodiment and comparative example to zinc symmetric flow battery (test conditions are the same as those of embodiment 1 unless otherwise specified)

[0028]

[0029]

[0030] It can be seen from the implementation data of the above-mentioned Examples 1-5 and Comparative Examples 1-4 that the separation membrane prepared by the present invention is used for zinc symmetric liquid flow batteries. Since it has a metal ion coordination layer, during the operation of the battery, the metal ions interact with zincate, and the zinc deposition morphology on the electrode surface can be regulated, which significantly alleviates the generation of zinc dendrites; further, the concave and convex stripes on the membrane surface can tolerate zinc dendrites generated under high surface capacity, avoid adverse effects on the battery service life, and improve the safety of the battery.

[0031] like Figure 1 , Figure 2 As shown, the surface of the membrane prepared in Comparative Example 4 is smooth, while the surface of the separation membrane prepared in Example 1 of the present invention has an uneven striped structure.

[0032] like Figure 3 As shown, at 160 mAh cm -2 At high surface capacity, in Comparative Example 1, zinc dendrites pierced the diaphragm, resulting in an internal short circuit in the battery; in Comparative Example 3, after about 20 hours of cycling, the internal polarization increased and the battery eventually short-circuited; while in Example 1, it can be stably cycled for 120 hours.

[0033] like Figure 4 As shown, Example 1-2 has a concave-convex stripe structure, which can accommodate more deposited zinc under high surface capacity; at the same time, a layer of metal ions is complexed on the surface, which can even out the zinc deposition process, thereby regulating the zinc deposition morphology and obtaining tightly packed zinc deposition. However, the battery assembled in Comparative Example 2-3 produces sharp zinc dendrites at the end of charging, which may damage the membrane.

Claims

1. Application of a metal-organic dense separation membrane in a zinc-based liquid flow battery, wherein the metal-organic dense separation membrane is prepared according to the following steps: (1) dissolving an organic polymer resin in an organic solvent and stirring to obtain a solution A; (2) Dissolve the metal salt in an organic solvent to obtain solution B, where the concentration of solution B is 1 to 2.5 mol L -1 ; The metal salt is one or more of nickel salt, copper salt, manganese salt or silver salt; (3) coating the solution A in step (1) on a flat plate to a thickness of 50 to 500 μm, and then immersing the plate in the solution B in step (2) for a phase inversion reaction for 0.5 to 4 h to obtain a film precursor having a metal-organic interface layer; (4) transferring the membrane precursor obtained in step (3) into a poor solvent for the resin for solidification to obtain the metal-organic dense separation membrane; The organic polymer resin is one or more of polyphenylquinoxaline, sulfonated polysulfone and polybenzimidazole; In step (2), the anion of the metal salt is one or more of chloride ion, acetate ion or nitrate ion.

2. The use according to claim 1, characterized in that: In step (1), The stirring temperature is 10-50° C., the stirring time is 2-48 hours, and the mass fraction of the organic polymer resin in the organic solvent is 10wt%-30wt%; The organic solvent is one or more of N,N'-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP) and formamide (DEM).

3. The use according to claim 2, characterized in that: The mass fraction of the organic polymer resin in the organic solvent is 15-20wt%.

4. The use according to claim 1, characterized in that: In step (2), the organic solvent is the same as that in (1).

5. The use according to claim 1, characterized in that: When the organic solvent in step (1) and step (2) is DMAc, the metal salt is a copper salt.

6. The use according to claim 1, characterized in that: In step (3), the coating thickness of the layer is 100-200 μm.

7. The use according to claim 1, characterized in that: In step (4), the poor solvent of the resin is one or more of water, ethanol, acetone, acetonitrile and isopropanol; the curing temperature is 15 to 30° C.; and the curing time is 10 to 24 hours.

8. The use according to claim 1, characterized in that: One side surface of the metal-organic dense separation membrane has a concave-convex band-shaped undulating stripe structure. When applied to a zinc-based liquid flow battery, the side surface of the metal-organic dense separation membrane with the undulating stripes faces the negative electrode of the battery.

9. The use according to claim 1, characterized in that: The zinc-based liquid flow battery includes zinc-iron liquid flow battery, zinc-bromine liquid flow battery, zinc-iodine liquid flow battery, and zinc-nickel liquid flow battery.

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