A diaphragm, its preparation method and use

Abstract

The application discloses a diaphragm and a preparation method and application thereof. The diaphragm is obtained by spinning a spinning solution containing a polymer and polydopamine modified MOP crystals; and the thickness is 10-100 mu m. The polydopamine modified MOP is introduced into the polymer for blending, and the small crystal size of the MOP provides a powerful condition for the dispersion of the MOP in the polymer; the polydopamine modification can prevent the agglomeration of the MOP crystals, and simultaneously acts as an interface adhesive, repairs gaps and promotes the hybridization of the MOP crystals and the polymer at a molecular level. The MOP crystals are rich in abundant nano-cage structures, and provide channels for ion transmission.

Description

Technical Field

[0001] This application relates to a separator, its preparation method, and its application, belonging to the field of battery materials. Background Technology

[0002] In recent years, aqueous zinc-ion batteries have shown great promise in large-scale energy storage and smart wearable devices due to their high discharge capacity, good cycle performance, rapid charge / discharge capability, low cost, ease of processing, environmental friendliness, high ionic conductivity, and high safety. However, during charge / discharge, the repeated uneven deposition and dissolution of zinc ions on the surface of the zinc electrode leads to the formation of rough and irregular dendrites. Once these dendrites, possessing an extremely high Young's modulus (108 GPa), pierce the separator, causing direct contact between the positive and negative electrodes and resulting in a short circuit. This hinders the superior performance and practical industrialization of zinc-ion batteries. The growth of zinc dendrites is one of the most difficult drawbacks to overcome in aqueous zinc-ion batteries.

[0003] To date, extensive research has been conducted to suppress dendrite formation and protect zinc anodes, for example, by introducing coatings on the anode surface or modulating the electrolyte-electrode interface to provide physical protection; adding electrolyte additives or developing new electrolyte salts to coordinate ion transport, homogenize the interfacial electric field, and induce zinc deposition. However, research on the role of battery separators in stabilizing zinc-ion batteries is relatively limited.

[0004] As is well known, the separator, as a component of a battery, not only allows ion transport but also prevents direct contact between the positive and negative electrodes. Therefore, the performance of the separator has a significant impact on the overall performance of the zinc-ion battery. Designing and controlling the separator's structure and performance holds promise for solving the problem of zinc dendrite formation during battery operation. Currently, zinc-ion batteries primarily use glass fiber (GF) separators several hundred micrometers thick due to their good compatibility with aqueous electrolytes and high ion conductivity. Unfortunately, their poor mechanical properties and large pore size make them susceptible to dendrite puncture, leading to short circuits. Summary of the Invention

[0005] One objective of this application is to prepare a molecular-level hybrid nanofiber membrane by blending polydopamine-modified MOP with polymer materials. The small crystal size of MOP (10–30 nm) provides favorable conditions for its dispersion in polymers; polydopamine modification can prevent the aggregation of MOP crystals and, at the same time, act as an interfacial binder to repair the gaps between polymers and MOPs, promoting the hybridization of MOP crystals and polymers at the molecular level.

[0006] The second objective of this application is to provide an electrospun MOP molecular-level hybrid nanofiber separator, wherein the electrospun MOP molecular-level hybrid nanofiber separator is prepared from a polymer matrix and polydopamine-modified MOP (MOP) by the preparation method described in the first objective. The separator thickness is 10–100 μm, and the MOP crystal size is 10–30 nm.

[0007] The third objective of this application is to provide an application of an electrospun MOP molecular-level hybrid nanofiber separator, wherein the electrospun MOP molecular-level hybrid nanofiber separator is the separator described in the second objective, and is applied in an aqueous zinc-ion battery.

[0008] According to one aspect of this application, a diaphragm is provided, said diaphragm being obtained by spinning a spinning solution containing polymer and polydopamine-modified MOP crystals;

[0009] The thickness of the diaphragm is 10–100 μm.

[0010] The size of the polydopamine-modified MOP crystal is 10–30 nm.

[0011] According to another aspect of this application, a method for preparing the above-mentioned diaphragm is provided, comprising the following steps:

[0012] The polymer, polydopamine-modified MOP crystals, and a polar solvent are mixed to obtain a spinning solution. The electrospinning solution is added to a syringe, and electrospinning is performed under appropriate voltage, receiving distance, and extrusion speed. After drying and hot pressing, the diaphragm is obtained.

[0013] The polymer is selected from at least one of polyacrylonitrile, polyvinylidene fluoride, polyvinyl alcohol, polyurethane, and polycaprolactone.

[0014] The polar solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and tetrahydrofuran;

[0015] In the spinning solution, the concentration of the polymer is 8-20 wt%.

[0016] In the spinning solution, the mass of the polydopamine-modified MOP crystals is 5 to 30 wt% of the mass of the polymer.

[0017] The voltage for electrospinning is 15–30 kV;

[0018] The extrusion speed is 1.5–3 ml / h;

[0019] The receiving distance is 8-25cm.

[0020] The drying temperature is 80–120°C;

[0021] The drying process is carried out under vacuum.

[0022] The hot pressing temperature is 80–120°C;

[0023] The pressure of the hot pressing is 5-15 MPa;

[0024] The hot pressing time is 3 to 15 minutes.

[0025] The polydopamine-modified MOP crystal is obtained through the following steps:

[0026] MOP crystals were immersed in a buffer solution containing dopamine hydrochloride and stirred at 30–60°C for 24–72 h. The product was separated by centrifugation, washed with deionized water, and freeze-dried to obtain the polydopamine-modified MOP crystals.

[0027] The buffer solution is a tris(hydroxymethyl)aminomethane solution with a pH of 7–12;

[0028] The solid-liquid ratio of the MOP crystal to the buffer solution containing dopamine hydrochloride is 10–100 g / L;

[0029] The concentration of dopamine hydrochloride in the buffer solution containing dopamine hydrochloride is 0.1–5 g / L.

[0030] MOP crystals are obtained through the following steps:

[0031] The metal salt and organic ligand were added to the solvent separately, dissolved completely, mixed evenly, and placed in a dark and dry place to react for one day. After washing and drying, MOP crystals were obtained.

[0032] The metal salt is selected from at least one of zinc chloride, zinc nitrate hexahydrate, copper chloride, copper acetate, zirconium nitrate pentahydrate, and zirconium dichlorocerocene.

[0033] The organic ligand is selected from one of 2-methylimidazolium, 5-hydroxyisophthalic acid, 1,3,5-triimidazolebenzene, and 5-aminoisophthalic acid;

[0034] The solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, tetrahydrofuran, methanol, and water.

[0035] The ratio of the metal salt to the solvent is (0.1-2) mol / L.

[0036] The ratio of the organic ligand to the solvent is (0.5–2) mol / L.

[0037] According to another aspect of this application, the above-described separator is provided for use in an aqueous zinc-ion battery.

[0038] The electrospun MOP molecular-level hybrid nanofiber separator has higher porosity, electrolyte absorption rate, and hydrophilicity, which can bind a large number of water molecules, thus reducing the corrosion of the zinc anode by contact with the aqueous electrolyte. It also has extremely high mechanical strength, which can induce uniform deposition of zinc ions, thereby effectively inhibiting the growth of zinc dendrites and preventing the separator from being punctured by dendrites, thereby improving the electrochemical performance and cycle life of the aqueous zinc-ion battery as a whole.

[0039] Compared with the prior art, the electrospun MOP molecular-level hybrid nanofiber membrane provided in this application has the following advantages:

[0040] (1) In this application, polydopamine-modified MOP is introduced into polymers for blending. The small crystal size of MOP (10-30 nm) provides favorable conditions for its dispersion in polymers. Polydopamine modification can prevent the aggregation of MOP crystals and, at the same time, act as an interfacial adhesive to repair the gaps between polymers and MOPs, promoting the hybridization of MOP crystals and polymers at the molecular level, thereby obtaining a molecular-level hybrid nanofiber membrane of MOP.

[0041] (2) MOP crystals are rich in nanocage structures, which provide channels for ion transport.

[0042] (3) Electrospun MOP molecular-level hybrid nanofiber separators have higher porosity, electrolyte absorption rate and hydrophilicity, which can bind a large number of water molecules, which helps to reduce the corrosion of zinc anode by contact with aqueous electrolyte; and have extremely high mechanical strength, which can induce uniform deposition of zinc ions, thereby effectively inhibiting zinc dendrite growth and preventing the separator from being pierced by dendrites, thus improving the electrochemical performance and cycle life of aqueous zinc-ion batteries as a whole, and has great application potential in the field of aqueous zinc-ion battery separators. Attached Figure Description

[0043] Figure 1 This is a scanning electron microscope image of the electrospun MOP molecular-level hybrid nanofiber membrane in Example 1 of this application, with a scale of 100 nm.

[0044] Figure 2 This is a scanning electron microscope image of the electrospun nanofiber diaphragm in Comparative Example 1 of this application, at a scale of 100 nm.

[0045] Figure 3 This is a scanning electron microscope image of the commercial electrospun PAN nanofiber membrane in Comparative Example 2 of this application, at a scale of 100 nm.

[0046] Figure 4a b, c, d, and e are zinc-to-zinc batteries assembled with nanofiber separators in Examples 1, 2, 1, 2, and 3 of this application, operating at 5 mA / cm².2 The polarization long cycle curve below. Detailed Implementation

[0047] The present application is described in detail below with reference to the embodiments, but the present application is not limited to the following embodiments.

[0048] Example 1

[0049] (1) Preparation of MOP: 14.87g of zinc nitrate hexahydrate and 8.21g of 2-methylimidazole were added to 50ml of methanol respectively. After being fully dissolved, they were mixed evenly and placed in a dark and dry place to react for one day. After washing and drying, MOP crystals were obtained.

[0050] (2) Polydopamine modification of MOP: 0.5g of the above MOP crystals were placed in 50ml of dopamine hydrochloride buffer solution (2g / L, pH=9), stirred at 30℃ for 24h, the product was separated by centrifugation, the obtained product was washed with deionized water, and then freeze-dried to obtain polydopamine modified MOP.

[0051] (3) Preparation of electrospinning solution: 1.17g of polyacrylonitrile was added to 8g of N,N-dimethylformamide and stirred to dissolve; 0.12g of the above polydopamine-modified MOP was dissolved in 2g of N,N-dimethylformamide; the two solutions were mixed evenly to obtain electrospinning solution.

[0052] (4) Preparation of MOP hybrid nanofiber membrane: The above electrospinning solution was added to a syringe, and electrospinning was carried out under the conditions of 25kV voltage, receiving distance of 15cm, and extrusion speed of 2ml / h. The composite membrane was collected, dried under vacuum at 80℃, and hot-pressed at 100℃ and 10MPa for 3min to finally obtain the electrospinned MOP molecular-level hybrid nanofiber membrane.

[0053] Figure 1 This is a scanning electron microscope (SEM) image of the electrospun MOP molecular-level hybrid nanofiber membrane from Example 1 of this application, at a scale of 100 nm. Figure 1 It is evident that the nanofibers are uniform in size and the membrane has a high porosity. No large particle agglomeration was observed in the fiber filaments, and uniformly distributed protrusions were visible on the surface of the fiber filaments, indicating that the MOP particles were uniformly encapsulated inside the fiber filaments.

[0054] Comparative Example 1

[0055] Compared with Example 1, except that polydopamine was not introduced to modify MOP, the other steps were exactly the same, and an electrospun nanofiber membrane with a thickness of 75 μm was finally obtained.

[0056] Figure 2This is a scanning electron microscope (SEM) image of the electrospun nanofiber membrane in Comparative Example 1 of this application, at a scale of 100 nm. As can be seen from the image, the nanofibers are uniform in size and the membrane exhibits high porosity, consistent with... Figure 1 In comparison, the surface of the fiber is smoother.

[0057] Comparative Example 2

[0058] Comparative Example 2 is a commercially available electrospun PAN nanofiber membrane with a thickness of 75 μm.

[0059] Figure 3 This is a scanning electron microscope (SEM) image of the commercially available electrospun PAN nanofiber membrane from Comparative Example 2 of this application, at a scale of 100 nm. As can be seen from the image, the nanofibers are uniform in size and the membrane exhibits high porosity. Figure 1 In comparison, the surface of the fiber is smoother.

[0060] Comparative Example 3

[0061] Comparative Example 3 is a commercial glass cellulose membrane with a thickness of 220 μm.

[0062] Figure 4a b, c, d, and e are zinc-to-zinc batteries assembled with nanofiber separators in Examples 1, 2, 1, 2, and 3 of this application, operating at 5 mA / cm². 2 The polarization long cycle curve below.

[0063] The separators from Examples 1, 2, Comparative Examples 1, 2, and 3 were cut into circular pieces, immersed in 1M zinc sulfate for 1 minute, and excess water was absorbed. Zinc-to-zinc batteries were then assembled and tested at 5 mA / cm². 2 The polarization stability of zinc-zinc batteries was tested at a current density, and the results are shown in Figure 4. In Examples 1 and 2, the batteries could cycle stably for over 1900 and 1500 hours, respectively. In Comparative Example 1, the battery short-circuited after 1100 cycles; in Comparative Example 2, the battery short-circuited after 900 cycles; and in Comparative Example 3, the battery short-circuited after 350 cycles.

[0064] It can be seen that the stability of the electrospun nanofiber membrane and the commercial electrospun PAN membrane in aqueous zinc-ion batteries is much higher than that of the commercial glass cellulose membrane. The stability of the electrospun MOP molecular-level hybrid nanofiber membrane in Examples 1 and 2 is significantly improved. This is mainly because the MOP crystals are rich in nanocage structures, providing channels for ion transport. At the same time, the electrospun MOP molecular-level hybrid nanofiber membrane has higher porosity, electrolyte absorption rate, and hydrophilicity, which can bind a large number of water molecules, thus reducing the corrosion of the zinc anode by contact with the aqueous electrolyte. It also has extremely high mechanical strength, which can induce uniform deposition of zinc ions, thereby effectively inhibiting zinc dendrite growth and preventing the membrane from being pierced by dendrites. The electrospun MOP molecular-level hybrid nanofiber membrane has a high zinc ion transference number, uniform electrolyte wetting, and high mechanical strength, which improves its resistance to zinc dendrites, thus showing higher stability.

[0065] Example 2

[0066] (1) Preparation of MOP: 3.993g of copper acetate and 9.11g of 5-hydroxyisophthalic acid were added to 50ml of water respectively, dissolved completely, mixed evenly, and placed in a dark and dry place to react for one day. After washing and drying, MOP crystals were obtained.

[0067] (2) Polydopamine modification of MOP: 2g of the above MOP crystals were placed in 50ml of dopamine hydrochloride buffer solution (0.5g / L, pH=7), stirred at 60℃ for 48h, the product was separated by centrifugation, the obtained product was washed with deionized water, and then freeze-dried to obtain polydopamine modified MOP.

[0068] (3) Preparation of electrospinning solution: Add 1.0g polyacrylonitrile and 0.5g polyurethane to 10g dimethyl sulfoxide and stir to dissolve; dissolve 0.5g of the above polydopamine-modified MOP in 5g N,N-dimethylformamide; mix the two solutions evenly to obtain electrospinning solution.

[0069] (4) Preparation of MOP hybrid nanofiber membrane: The above electrospinning solution was added to a syringe, and electrospinning was carried out under the conditions of 20kV voltage, receiving distance of 10cm, and extrusion speed of 1.5ml / h. The composite membrane was collected, dried under vacuum at 100℃, and hot-pressed at 100℃ and 5MPa for 12min to finally obtain the MOP hybrid nanofiber membrane.

[0070] Example 3

[0071] (1) Preparation of MOP: 5.85g of zirconium dichloroethylene and 10.87g of 5-aminoisophthalic acid were added to 50ml of N,N-dimethylacetamide, respectively. After being fully dissolved, they were mixed evenly and placed in a dark and dry place to react for one day. After washing and drying, MOP crystals were obtained.

[0072] (2) Polydopamine modification of MOP: 1.5g of the above MOP crystals were placed in 50ml of dopamine hydrochloride buffer solution (3g / L, pH=10), stirred at 50℃ for 72h, the product was separated by centrifugation, the obtained product was washed with deionized water, and then freeze-dried to obtain polydopamine modified MOP.

[0073] (3) Preparation of electrospinning solution: Add 0.5g polyvinylidene fluoride and 0.8g polycaprolactone to 8g N,N-dimethylformamide and stir to dissolve; dissolve 0.25g of the above polydopamine-modified MOP in 2g N,N-dimethylformamide; mix the two solutions evenly to obtain electrospinning solution.

[0074] (4) Preparation of MOP hybrid nanofiber membrane: The above electrospinning solution was added to a syringe, and electrospinning was carried out under the conditions of 15kV voltage, receiving distance of 25cm, and extrusion speed of 2.5ml / h. The composite membrane was collected, dried under vacuum at 80℃, and hot-pressed at 120℃ and 5MPa for 3min to finally obtain the MOP hybrid nanofiber membrane.

[0075] Example 4

[0076] (1) Preparation of MOP: 4.09 g of zinc chloride and 8.21 g of 2-methylimidazole were added to 50 ml of methanol respectively. After being fully dissolved, they were mixed evenly and placed in a dark and dry place to react for one day. After washing and drying, MOP crystals were obtained.

[0077] (2) Polydopamine modification of MOP: 1.2g of the above MOP crystals were placed in 50ml of dopamine hydrochloride buffer solution (5g / L, pH=12), stirred at 40℃ for 48h, the product was separated by centrifugation, the obtained product was washed with deionized water, and then freeze-dried to obtain polydopamine modified MOP.

[0078] (3) Preparation of electrospinning solution: 1.0g polyacrylonitrile and 0.2g polyvinylidene fluoride were added to 7g dimethyl sulfoxide and stirred to dissolve; 0.3g of the above polydopamine-modified MOP was dissolved in 2g tetrahydrofuran; the two solutions were mixed evenly to obtain electrospinning solution.

[0079] (4) Preparation of MOP hybrid nanofiber membrane: The above electrospinning solution was added to a syringe, and electrospinning was carried out under the conditions of 20kV voltage, receiving distance of 15cm, and extrusion speed of 1.5ml / h. The composite membrane was collected, dried under vacuum at 100℃, and hot-pressed at 100℃ and 8MPa for 6min to finally obtain the MOP hybrid nanofiber membrane.

[0080] Example 5

[0081] (1) Preparation of MOP: 4.63g zirconium nitrate pentahydrate and 9.29g 5-hydroxyisophthalic acid were added to 50ml of water respectively, dissolved completely, mixed evenly, and placed in a dark and dry place to react for one day. After washing and drying, MOP crystals were obtained.

[0082] (2) Polydopamine modification of MOP: 1.2g of the above MOP crystals were placed in 50ml of dopamine hydrochloride buffer solution (0.5g / L, pH=7), stirred at 60℃ for 48h, the product was separated by centrifugation, the obtained product was washed with deionized water, and then freeze-dried to obtain polydopamine modified MOP.

[0083] (3) Preparation of electrospinning solution: Add 1.0g polyacrylonitrile and 0.5g polyurethane to 10g dimethyl sulfoxide and stir to dissolve; dissolve 0.5g of the above polydopamine-modified MOP in 5g N,N-dimethylformamide; mix the two solutions evenly to obtain electrospinning solution.

[0084] (4) Preparation of MOP hybrid nanofiber membrane: The above electrospinning solution was added to a syringe, and electrospinning was carried out under the conditions of 15kV voltage, receiving distance of 15cm, and extrusion speed of 2ml / h. The composite membrane was collected, dried under vacuum at 100℃, and hot-pressed at 80℃ and 5MPa for 12min to finally obtain the MOP hybrid nanofiber membrane.

[0085] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A membrane for use with zinc ions in aqueous systems, characterized in that, The diaphragm is obtained by spinning a spinning solution containing polymer and polydopamine-modified MOP crystals; The thickness of the diaphragm is 10~100μm; The polydopamine-modified MOP crystal is obtained through the following steps: MOP crystals were immersed in a buffer solution containing dopamine hydrochloride and then freeze-dried to obtain the polydopamine-modified MOP crystals.

2. The diaphragm according to claim 1, characterized in that, The size of the polydopamine-modified MOP crystal is 10~30 nm.

3. A method for preparing the diaphragm according to any one of claims 1 or 2, characterized in that, Includes the following steps: The polymer, polydopamine-modified MOP crystals, and a polar solvent are mixed to obtain a spinning solution, which is then electrospun, dried, and hot-pressed to obtain the diaphragm.

4. The preparation method according to claim 3, characterized in that, The polymer is selected from at least one of polyacrylonitrile, polyvinylidene fluoride, polyvinyl alcohol, polyurethane, and polycaprolactone. The polar solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and tetrahydrofuran; The polymer concentration in the spinning solution is 8-20 wt%. In the spinning solution, the mass of polydopamine-modified MOP crystals is 5-30 wt% of the mass of the polymer.

5. The preparation method according to claim 3, characterized in that, The voltage for electrospinning is 15~30kV; The extrusion speed is 1.5~3 ml / h; The receiving distance is 8~25cm.

6. The preparation method according to claim 3, characterized in that, The drying temperature is 80~120℃; The drying process is carried out under vacuum. The hot pressing temperature is 80~120℃; The pressure of the hot pressing is 5~15MPa; The hot pressing time is 3 to 15 minutes.

7. The preparation method according to claim 3, characterized in that, The solid-liquid ratio of the MOP crystal to the buffer solution containing dopamine hydrochloride is 10~100g / L; The concentration of dopamine hydrochloride in the buffer solution containing dopamine hydrochloride is 0.1~5 g / L.

8. A diaphragm according to any one of claims 1 or 2, characterized in that, Used in aqueous zinc-ion batteries.

Images