A hydrophilic composite separator for secondary zinc-manganese batteries and a preparation method thereof

Abstract

The application discloses a preparation method of a hydrophilic composite diaphragm for a secondary zinc-manganese battery, and is characterized in that the method is prepared as follows: a hydrophilic polymer compound with O-rich or N-rich functional groups is water-swollen, a binder is added, and stirring and uniform mixing are performed to prepare a hydrophilic functional layer coating slurry; the hydrophilic functional layer coating slurry is scraped on a base film, and drying is performed to obtain the hydrophilic composite diaphragm. The method directly scrapes the hydrophilic polymer functional layer on the base film, and a large number of O or N heteroatoms on the polymer promote uniform deposition of zinc metal and improve the cycle reversibility of a zinc ion battery. 2+ The selective interaction promotes uniform deposition of zinc metal and improves the cycle reversibility of the zinc ion battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of new materials, and particularly relates to a hydrophilic composite diaphragm for a secondary zinc-manganese battery and a preparation method thereof. BACKGROUND

[0002] The aqueous secondary zinc-manganese battery has been widely concerned due to its high capacity, high safety, low cost, green friendliness and other advantages, and is considered as one of the power systems with the most broad development potential for large-scale energy storage and wearable electronic devices. However, the zinc negative electrode surface in the aqueous electrolyte solution will cause serious metal dendrite growth, corrosion and hydrogen evolution and other side reactions, resulting in low coulombic efficiency, rapid capacity decay and greatly shortened cycle life of the battery. Therefore, the diaphragm mainly used for large-scale application of the aqueous secondary zinc-manganese battery is a glass fiber diaphragm with high strength. However, when the diaphragm is used, it has no selectivity to the migration of zinc ions, which is easy to cause self-discharge, or the zinc ions are not controlled to be unevenly deposited during the charging process, and finally the metal dendrites formed will penetrate through the entire diaphragm, causing short circuit and battery failure, and even safety problems.

[0003] Therefore, researchers change the diaphragm substrate or modify the diaphragm surface by a magnetron sputtering method to improve the selectivity of zinc ion migration, regulate the uniform deposition of zinc, inhibit or resist dendrite growth, so as to improve the cycle capacity of the zinc ion battery. For example, a glass fiber diaphragm (GF@SM) modified by a functional supramolecule is used as the diaphragm of the aqueous zinc ion battery, the migration behavior of zinc ions in the electrolyte between the positive and negative electrodes is regulated, the negative electrode dendrite growth is effectively reduced, and the electrochemical performance of the aqueous zinc ion battery is greatly improved.

[0004] However, the current diaphragm modification method using a supramolecular material has a complex process, high cost and often uses toxic and harmful organic reagents, and is not suitable for large-scale production. Therefore, there is an urgent need for a diaphragm modification method which is simple in process, environmentally friendly and safe, and can greatly improve the service life of the aqueous zinc ion battery such as the secondary zinc-manganese battery. SUMMARY

[0005] In order to solve the above technical problems, the application provides a preparation method of a hydrophilic composite diaphragm for a secondary zinc-manganese battery, and also provides a hydrophilic composite diaphragm for a secondary zinc-manganese battery prepared by the method. 2+ The selective interaction promotes the uniform deposition of zinc metal and improves the cycle reversibility of the zinc ion battery.

[0006] To achieve the above first object, the application is implemented by the following technical scheme: a preparation method of a hydrophilic composite diaphragm for a secondary zinc-manganese battery, characterized in that the method is prepared as follows: a hydrophilic polymer compound with O-rich functional groups or N-rich functional groups is water-swollen, a binder is added and mixed and stirred uniformly to prepare a hydrophilic functional layer coating slurry; the hydrophilic functional layer coating slurry is scraped on a base film and dried to obtain the hydrophilic composite diaphragm.

[0007] The hydrophilic functional layer coating slurry partially penetrates into the pore structure of the base film to form a mutually penetrating structure, and partially does not penetrate into the pore structure of the base film to form a layered structure.

[0008] In the above scheme: the O-rich functional groups are at least one of hydroxyl, carboxyl, aldehyde group or sulfonic acid group.

[0009] In the above scheme: the N-rich functional groups are at least one of amide group or amino group.

[0010] In the above scheme: the O-rich functional groups or N-rich functional groups are on the side chain of the hydrophilic polymer compound. Avoiding the hydrophobic carbon chain to destroy the continuous hydrophilic network formed by the O-rich functional groups or N-rich functional groups.

[0011] In the above scheme: the hydrophilic polymer compound is one of polyvinyl alcohol, polyacrylic acid, polyacrylamide, cellulose, chitin and chitosan. Avoiding the hydrophobic carbon chain to destroy the continuous hydrophilic network formed by the O-rich functional groups or N-rich functional groups.

[0012] In the above scheme: the concentration of the water-swollen hydrophilic polymer compound is 40-240 mg·ml -1 .

[0013] In the above scheme: the binder is at least one of sodium carboxymethyl cellulose, sodium alginate, butyl rubber latex, water-based polyurethane or polyvinyl alcohol water-based adhesive; the mass ratio of the hydrophilic polymer compound to the binder is 2:1-100:1.

[0014] In the above scheme: the base film is one of glass fiber diaphragm, polypropylene diaphragm, polyethylene diaphragm, non-woven diaphragm, polyvinylidene fluoride filter membrane or nylon filter membrane.

[0015] In the above scheme: the average thickness of the hydrophilic functional layer in the prepared hydrophilic composite diaphragm is 10-150 μm.

[0016] The preparation method of the hydrophilic composite diaphragm for the secondary zinc-manganese battery.

[0017] Beneficial effects:

[0018] The present application improves the nucleation overpotential of zinc by the selective interaction of a large number of O or N heteroatoms in the functional layer with Zn 2+ , induces uniform deposition of Zn 2+ , inhibits the formation and growth of zinc dendrites; and competes with zinc negative electrode surface water molecules through hydrogen bonding, reducing water activity and reducing the occurrence of corrosion and hydrogen evolution and other side reactions. According to the test, the zinc-zinc symmetric battery assembled by using the hydrophilic composite diaphragm prepared by the present application can be stably cycled for 1390h in a constant current charge-discharge test at 1mA·cm -2 . Moreover, the preparation process of the composite diaphragm is simple, easy to repeat and low in cost, can significantly improve the cycle life of zinc electrode in aqueous electrolyte, and can be widely applied to secondary zinc-manganese batteries and other aqueous zinc ion batteries.

[0019] The hydrophilic composite diaphragm for secondary zinc-manganese batteries of the present application directly scrapes the functional layer on the base film, which is simple, economical and fast, and is convenient for repeated experiments and mass production. The preparation process of the composite diaphragm is simple, easy to repeat and low in cost, can significantly improve the cycle life of zinc electrode in aqueous electrolyte, and can be widely applied to secondary zinc-manganese batteries and other aqueous zinc ion batteries. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is a scanning electron microscope image of the hydrophilic composite diaphragm in Example 5.

[0021] Figure 2 It is the cycle life of the zinc-zinc symmetric battery in Example 5 under constant current charge-discharge at 1mA·cm -2 current density for 1h each.

[0022] Figure 3 It is the cycle life of the zinc-zinc symmetric battery in Comparative Example 1 under constant current charge-discharge at 1mA·cm -2 current density for 1h each. DETAILED DESCRIPTION

[0023] The present application will be further described below in conjunction with examples and drawings

[0024] A preparation method of a hydrophilic composite diaphragm for secondary zinc-manganese batteries is prepared as follows: a hydrophilic polymer compound with O-rich functional groups or N-rich functional groups is water-swollen, a binder is added and mixed and stirred uniformly to prepare a hydrophilic functional layer coating slurry; the hydrophilic functional layer coating slurry is scraped on the base film, and dried to obtain the hydrophilic composite diaphragm.

[0025] The O-rich functional group is at least one of hydroxyl, carboxyl, aldehyde or sulfonic acid group. The N-rich functional group is at least one of amide or amino group. The O-rich functional group or the N-rich functional group is on the side chain of the hydrophilic macromolecular compound. The hydrophilic macromolecular compound is one of polyvinyl alcohol, polyacrylic acid, polyacrylamide, cellulose, chitin and chitosan. The concentration of the hydrophilic macromolecular compound after water swelling is 40-240 mg·ml -1 The binder is at least one of sodium carboxymethyl cellulose, sodium alginate, butyl rubber latex ammonia, water-based polyester or polyvinyl alcohol-based water-based adhesive. The mass ratio of the hydrophilic macromolecular compound to the binder is 2:1-100:1. The base film is one of glass fiber separator, polypropylene separator, polyethylene separator, non-woven fabric separator, polyvinylidene fluoride filter membrane or nylon filter membrane. The average thickness of the hydrophilic functional layer in the hydrophilic composite separator is 10-150 μm.

[0026] Example 1

[0027] 18 g of hydroxyl-containing side chain hydrophilic macromolecular polyvinyl alcohol is added to 100 mL of deionized water to swell, and then 0.9 g of sodium carboxymethyl cellulose binder is added to mix and stir uniformly to prepare a hydrophilic functional layer coating slurry. The hydrophilic functional layer coating slurry is blade coated on a glass fiber separator, the slurry penetrates into the pore structure of the base film to form an interpenetrating structure, and is dried to obtain a hydrophilic composite separator with an average thickness of the hydrophilic functional layer of 60 μm. The zinc-zinc symmetric battery is assembled with the separator, two pieces of zinc foil as positive and negative electrodes and 2M ZnSO4 electrolyte, and constant current charge-discharge test is carried out. The current density is 1 mA·cm -2 The cycle test is carried out under the condition of constant current charging for 1 h and transverse current discharging for 1 h. The results show that the cycle life of the symmetric battery reaches 620 h.

[0028] Example 2

[0029] 15 g of carboxyl-containing side chain hydrophilic macromolecular polyacrylic acid is added to 100 mL of deionized water to swell, and then 1.35 g of sodium carboxymethyl cellulose binder is added to mix and stir uniformly to prepare a hydrophilic functional layer coating slurry. The hydrophilic functional layer coating slurry is blade coated on a polypropylene separator, the slurry does not penetrate into the pore structure of the base film to form a layered structure, and is dried to obtain a hydrophilic composite separator with an average thickness of the hydrophilic functional layer of 10 μm. The zinc-zinc symmetric battery is assembled with the separator, two pieces of zinc foil as positive and negative electrodes and 2M ZnSO4 electrolyte, and constant current charge-discharge test is carried out. The current density is 1 mA·cm -2 The cycle test is carried out under the condition of constant current charging for 1 h and transverse current discharging for 1 h. The results show that the cycle life of the symmetric battery reaches 430 h.

[0030] Example 3

[0031] The 4 g of hydrophilic polymer polyacrylamide containing amide group in side chain was added into 100 mL of deionized water to swell, and then 1.8 g of sodium alginate binder was added to mix and stir uniformly to prepare a hydrophilic functional layer coating slurry; the hydrophilic functional layer coating slurry was blade coated on a polyethylene separator, the slurry did not penetrate into the pore structure of the base film, forming a layered structure, and after drying, a hydrophilic composite separator with an average thickness of 100 um of the hydrophilic functional layer was obtained. The zinc-zinc symmetric battery was assembled with the separator, two pieces of zinc foil as positive and negative electrodes, and 2M ZnSO4 electrolyte, and constant current charge-discharge test was performed. At a current density of 1 mA·cm -2 , the constant current charging was 1 h, and the cross current discharging was 1 h, and the cycle test was performed. The results showed that the cycle life of the symmetric battery reached 770 h.

[0032] Example 4

[0033] The 18 g of hydrophilic polymer chitosan containing hydroxyl and amino groups in side chain was added into 100 mL of deionized water to swell, and then 0.18 g of butyl rubber latex ammonia binder was added to mix and stir uniformly to prepare a hydrophilic functional layer coating slurry; the hydrophilic functional layer coating slurry was blade coated on a polyvinylidene fluoride filter membrane, the slurry penetrated into the pore structure of the base film, forming a mutually penetrating structure, and after drying, a hydrophilic composite separator with an average thickness of 150 um of the hydrophilic functional layer was obtained. The zinc-zinc symmetric battery was assembled with the separator, two pieces of zinc foil as positive and negative electrodes, and 2M ZnSO4 electrolyte, and constant current charge-discharge test was performed. At a current density of 1 mA·cm -2 , the constant current charging was 1 h, and the cross current discharging was 1 h, and the cycle test was performed. The results showed that the cycle life of the symmetric battery reached 940 h.

[0034] Example 5

[0035] The 18 g of hydrophilic polymer chitosan containing hydroxyl and amino groups in side chain was added into 100 mL of deionized water to swell, and then 0.18 g of butyl rubber latex ammonia binder was added to mix and stir uniformly to prepare a hydrophilic functional layer coating slurry; the hydrophilic functional layer coating slurry was blade coated on a polyvinylidene fluoride filter membrane, the slurry penetrated into the pore structure of the base film, forming a mutually penetrating structure, and after drying, a hydrophilic composite separator with an average thickness of 150 um of the hydrophilic functional layer was obtained. The zinc-zinc symmetric battery was assembled with the separator, two pieces of zinc foil as positive and negative electrodes, and 2M ZnSO4 electrolyte, and constant current charge-discharge test was performed. At a current density of 1 mA·cm -2 , the constant current charging was 1 h, and the cross current discharging was 1 h, and the cycle test was performed. The results showed that the cycle life of the symmetric battery reached 940 h.

[0036] Example 6

[0037] A 24 g hydrophilic polymer chitin containing hydroxyl and amide groups in the side chain was added to 100 mL of deionized water to swell, then 0.72 g of butyl rubber latex binder was added and mixed uniformly to prepare a hydrophilic functional layer coating slurry; the hydrophilic functional layer coating slurry was blade coated on a polypropylene separator, the slurry did not penetrate into the pore structure of the base film, forming a layered structure, and was dried to obtain a hydrophilic composite separator with an average thickness of 20 um of the hydrophilic functional layer. A zinc-zinc symmetric battery was assembled with the separator, two pieces of zinc foil as the positive and negative electrodes, and 2M ZnSO4 electrolyte, and constant current charge-discharge tests were performed. At a current density of 1 mA·cm -2 , the symmetric battery was cycled for 920 h.

[0038] Comparative Example 1

[0039] A zinc-zinc symmetric battery was assembled with a glass fiber separator, two pieces of zinc foil as the positive and negative electrodes, and 2M ZnSO4 electrolyte, and constant current charge-discharge tests were performed. At a current density of 1 mA·cm -2 , the symmetric battery was cycled for 180 h.

[0040] Although embodiments of the present application have been shown and described, it is to be understood that various modifications, substitutions, replacements and variations can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a hydrophilic composite separator for a secondary zinc-manganese battery, characterized by, The hydrophilic functional layer coating slurry is prepared by the following method: a hydrophilic polymer compound with O-rich or N-rich functional groups is water-swollen, a binder is added and mixed uniformly to obtain the hydrophilic functional layer coating slurry; the hydrophilic functional layer coating slurry is scraped on a base film and dried to obtain the hydrophilic composite diaphragm; the hydrophilic polymer compound is one of polyvinyl alcohol, polyacrylamide, chitin and chitosan; the binder is at least one of sodium carboxymethyl cellulose, sodium alginate, butylphenyl latex, water-based polyurethane or polyvinyl alcohol water-based adhesive; the mass ratio of the hydrophilic polymer compound to the binder is (2-100):1; the concentration of the water-swollen hydrophilic polymer compound is 40-240 mg·ml -1 ; the base film is one of glass fiber diaphragm, polypropylene diaphragm, polyethylene diaphragm, polyvinylidene fluoride filter membrane or nylon filter membrane; the hydrophilic functional layer coating slurry partially penetrates into the pore structure of the base film to form a mutually penetrating structure, and partially does not penetrate into the pore structure of the base film to form a layered structure.

2. The method for preparing the hydrophilic composite separator for secondary zinc-manganese batteries according to claim 1, characterized in that: The average thickness of the hydrophilic functional layer in the prepared hydrophilic composite diaphragm is 10-150 μm.

3. A method for preparing a hydrophilic composite diaphragm for secondary zinc-manganese batteries according to any one of claims 1-2.

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