Preparation method of sodium ion battery separator, sodium ion battery separator and application thereof

Abstract

The present application discloses a method for preparing a sodium ion battery separator, a sodium ion battery separator and its application. The preparation method comprises the following steps: (1) stirring a mixture containing polyether block polyamide, polyacrylonitrile and a solvent to obtain a spinning solution; (2) subjecting the spinning solution to electrostatic spinning, hot pressing and drying to obtain the sodium ion battery separator. During the preparation process, a fiber separator prepared by electrostatic spinning technology is integrated on a receiving roller. The spinning solution of the new separator is composed of polyether block polyamide (Pebax) and polyacrylonitrile (PAN). The advantages of the present application are that the electrolyte wettability of the separator can be greatly improved, the contact angle can be reduced, and the liquid absorption rate can be increased to ensure the free transmission of sodium ions during the charge and discharge process; compared with traditional polyolefin separators, the new sodium ion battery separator has excellent electrochemical cycle stability and capacity retention rate.

Description

Technical Field

[0001] The present application relates to a preparation method of a sodium ion battery separator, a sodium ion battery separator and applications thereof, and belongs to the technical field of sodium ion batteries. Background Art

[0002] The rapid development of emerging portable electronics, transportation (such as electric vehicles, hybrid vehicles, autonomous aircraft, etc.) and smart grid-scale energy storage has stimulated the growing demand for high energy density, high safety and low-cost energy storage systems. However, the continued large-scale application of lithium-ion batteries is limited by their soaring costs. Considering the shortage and uneven distribution of lithium resources, it hinders the development of the new energy industry. Therefore, it is imperative to develop new secondary batteries that can replace lithium-ion batteries. Among several alternative batteries, sodium-ion batteries (SIBs) have a reaction mechanism similar to that of lithium-ion batteries. In addition, sodium has the huge advantages of abundant reserves and relatively low cost, which has attracted the attention of many researchers.

[0003] Sodium-ion batteries are mainly composed of four parts: positive electrode material, negative electrode material, separator, and electrolyte. During charging, sodium ions are released from the positive electrode, pass through the separator, and embed into the negative electrode material. During discharge, the opposite occurs, with sodium ions released from the negative electrode, pass through the separator, and embed into the positive electrode material. Therefore, the separator material is also a key component of sodium-ion batteries. The separator commonly used in sodium-ion batteries is generally made of glass fiber material, but the glass fiber separator is a fibrous non-woven filter paper that is inherently thick and has excessive internal resistance, resulting in decreased battery cycle performance. It is not suitable for high-energy-density batteries, and is also expensive and has low tensile strength. Traditional polyolefin separators have poor wettability and thermal stability, which limits their application.

[0004] The electrospinning process is a fiber manufacturing technology. Under the action of a high-voltage electric field, the polymer liquid will be filled with electric charges. The electric field force and the surface tension of the liquid will act, and the liquid at the end of the nozzle will form a "Taylor cone". As the electric field force gradually increases, the fibers will split, the solution will evaporate, and the fibers will solidify. Finally, they will be collected on the receiving plate to form a fiber membrane. Electrospinning technology can realize the synthesis of one-dimensional nanomaterials with controllable structure and uniform morphology, and plays an important role in battery separators. Summary of the Invention

[0005] In response to the problems existing in the general glass fiber diaphragm of sodium ion batteries, the present invention provides a method for preparing a new sodium ion battery diaphragm. The new diaphragm prepared by this method has a simple process, is easy to operate, and has low equipment requirements. The prepared sodium ion battery diaphragm has a high liquid absorption rate, good electrolyte wettability and cycle performance.

[0006] According to one aspect of the present application, a method for preparing a sodium ion battery separator is provided, the method comprising the following steps:

[0007] (1) stirring a mixture containing polyether block polyamide, polyacrylonitrile, and a solvent to obtain a spinning solution;

[0008] (2) The spinning solution is subjected to electrospinning, hot pressing, and drying to obtain the sodium ion battery separator.

[0009] Optionally, in step (1), the mass ratio of the polyether block polyamide to the polyacrylonitrile is 3-7:7-3.

[0010] Optionally, in step (1), the mass ratio of the polyether block polyamide to the polyacrylonitrile is independently selected from any value among 1:1, 3:4, 3:5, 3:6, 3:7, 4:3, 4:5, 4:6, 4:7, 5:3, 5:4, 5:5, 5:6, 5:7, 6:3, 6:4, 6:5, 6:7, 7:3, 7:4, 7:5, 7:6, or a range between any two of the above.

[0011] Optionally, in step (1), the solid content of the spinning solution is 10-16%.

[0012] Optionally, in step (1), the solid content in the spinning solution is independently selected from any value among 10%, 11%, 12%, 13%, 14%, 15%, 16% or a range between any two of the above.

[0013] Optionally, in step (2), the electrospinning conditions are:

[0014] The voltage of electrospinning is 12 to 20 kV, the spinning speed is 0.05 to 0.15 mm / min, and the spinning receiving distance is 10 to 18 cm.

[0015] Optionally, the electrospinning voltage is independently selected from any value among 12 kV, 13 kV, 14 kV, 15 kV, 16 kV, 18 kV, 20 kV or a range between any two of the above values.

[0016] Optionally, the spinning push speed is independently selected from any value among 0.05 mm / min, 0.08 mm / min, 0.10 mm / min, 0.12 mm / min, 0.15 mm / min or a range between any two of the above values.

[0017] Optionally, the receiving distance of the spinning is independently selected from any value among 10 cm, 12 cm, 14 cm, 16 cm, 18 cm or a range between any two of the above values.

[0018] Optionally, in step (2), the temperature of the hot pressing is 80-120°C.

[0019] Optionally, in step (2), the temperature of the hot pressing is independently selected from any value among 80°C, 90°C, 100°C, 110°C, 120°C or a range between any two of the above values.

[0020] Optionally, in step (2), the drying temperature is 60 to 80° C., and the drying time is 10 to 24 hours.

[0021] Optionally, in step (2), the drying temperature is independently selected from any value among 60°C, 65°C, 70°C, 75°C, 80°C or a range between any two of the above values.

[0022] Optionally, in step (2), the drying time is independently selected from any value among 10h, 12h, 14h, 16h, 18h, 20h, 24h or a range between any two of the above.

[0023] Optionally, in step (1), the stirring time is 10 to 24 hours, and the stirring speed is 200 to 600 rpm.

[0024] Optionally, in step (1), the stirring time is independently selected from any value among 10h, 12h, 14h, 16h, 18h, 20h, 24h or a range between any two of the above.

[0025] Optionally, in step (1), the stirring speed is independently selected from any value among 200 rpm, 300 rpm, 400 rpm, 500 rpm, 600 rpm or a range between any two of the above values.

[0026] Optionally, in step (1), the solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, acetone, and isopropyl alcohol.

[0027] According to another aspect of the present application, a sodium ion battery separator prepared by the above-described preparation method is provided, wherein the diameter of the sodium ion battery separator is 100 to 400 nm.

[0028] Optionally, the liquid absorption rate of the sodium ion battery separator is 700% to 800%.

[0029] Optionally, the liquid absorption rate of the sodium ion battery separator is independently selected from any value of 700%, 720%, 740%, 750%, 760%, 780%, 800% or a range between any two of the above.

[0030] According to another aspect of the present application, there is provided an application of the above-mentioned sodium ion battery separator in a sodium ion battery, wherein the sodium ion battery comprises: a sodium ferrite positive electrode, a sodium ion battery separator and a sodium metal negative electrode.

[0031] As an optional implementation method, the present application is implemented through the following technical solutions:

[0032] A method for preparing a novel sodium ion battery separator, the method comprising the following steps:

[0033] Step 1: Preparation of spinning solution

[0034] First, a certain amount of polyether block polyamide (Pebax) is dissolved in a solvent and stirred continuously at 50-80°C for 3-8 hours with a magnetic stirrer speed of 200-600 rpm. After the Pebax particles are dissolved, a certain amount of polyacrylonitrile (PAN) powder is added and stirred at room temperature for 10-24 hours with a magnetic stirrer speed of 200-600 rpm to obtain a uniform spinning solution.

[0035] Step 2: Preparation of Pebax / PAN fiber membrane

[0036] Take the spinning solution in step 1, adjust the spinning voltage, spinning distance, and solution flow rate, and then perform electrospinning to obtain a uniform Pebax / PAN fiber membrane.

[0037] Step 3: Processing of Pebax / PAN fiber membrane

[0038] The Pebax / PAN fiber membrane obtained in step 2 is dried in a vacuum drying oven for 10 to 24 hours, and then hot-pressed at 80 to 120° C. to completely evaporate the solvent, thereby obtaining a sodium ion battery separator.

[0039] Optionally, the specific steps of the electrospinning include: magnetically stirring the spinning solution for 12 to 24 hours, taking 5 mL of the spinning solution and placing it in a syringe, using a 21G nozzle, setting the voltage to 12 to 20 kV, and performing electrospinning at a push speed of 0.05 to 0.15 mm / min and a receiving distance of 10 to 18 cm to prepare the new sodium ion battery membrane.

[0040] The sodium ion battery prepared by the novel sodium ion battery separator disclosed in the present application, wherein sodium ferrite and sodium flakes are used as active materials in the positive electrode and negative electrode, respectively. During the preparation process, the fiber separator prepared by electrospinning technology is integrated on the receiving roller. The spinning solution of the novel separator is composed of polyether block polyamide (Pebax) and polyacrylonitrile (PAN). The advantage of the present invention is that it can greatly improve the electrolyte wettability of the separator, reduce the contact angle, and increase the liquid absorption rate to ensure the free transmission of sodium ions during the charge and discharge process; compared with traditional polyolefin separators, the novel sodium ion battery separator has excellent electrochemical cycle stability and capacity retention.

[0041] The beneficial effects of this application include:

[0042] 1) This application combines the advantages of polyether block polyamide and polyacrylonitrile. The polyether block polyamide material has the properties of a thermoplastic elastomer and good and stable performance at low temperatures, while polyacrylonitrile has the advantages of high ionic conductivity, good thermal stability, and good cycle performance. The prepared Pebax / PAN fiber membrane exhibits good dimensional stability and low interfacial internal resistance.

[0043] 2) The preparation process provided in this application is simple and has low equipment requirements. The fiber membrane obtained by electrospinning does not have beaded fibers, the fibers are evenly distributed, the fiber diameter distribution is 100-400nm, and the membrane has good wettability, which can achieve an initial coulombic efficiency of 98%.

[0044] 3) The method for preparing the sodium ion battery separator provided in this application is simple and efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is a SEM image of the Pebax / PAN fiber membrane prepared in Example 1 of the present application, with a scale of 2 μm;

[0046] Figure 2 This is an SEM image of the Pebax / PAN fiber membrane prepared in Example 2 of the present application, with a scale of 5 μm;

[0047] Figure 3 This is a contact angle test diagram of the Pebax / PAN fiber membrane prepared in Example 1 of the present application;

[0048] Figure 4 In this application, the Pebax / PAN fiber membrane prepared in Example 1 was used as a separator to assemble a sodium ion battery, and the charge and discharge cycle performance was tested. DETAILED DESCRIPTION

[0049] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0050] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0051] This application uses Beijing Yongkang Leye SS-2535H electrospinning machine to prepare the diaphragm, uses scanning electron microscope to perform SEM test on the sample, uses German Krues DSA25 equipment to perform contact angle test, uses weighing method to perform liquid absorption rate test, and uses Shenzhen Xinwei Instrument to perform battery cycle performance test.

[0052] Example 1

[0053] The preparation method of the sodium ion battery separator of this embodiment comprises the following steps:

[0054] Step 1: Prepare the spinning solution: dissolve commercially available Pebax particles in DMF, stir continuously at 70°C for 5 hours, and use a magnetic stirrer at a speed of 300 rpm. After the Pebax particles are dissolved, add PAN powder with a mass ratio of 1:1, stir at room temperature for 12 hours, and use a magnetic stirrer at a speed of 400 rpm to obtain a uniform spinning solution.

[0055] Step 2 Preparation of Pebax / PAN composite fiber membrane: Take 10 mL of the spinning solution with a solid content of 10% in step 1, adjust the spinning voltage to 16 kV, the spinning distance to 14 cm, and the solution flow rate to 0.1 mm / min, and then perform electrospinning to obtain a uniform Pebax / PAN composite fiber membrane.

[0056] Step 3: Treatment of the Pebax / PAN composite fiber membrane: The Pebax / PAN composite fiber membrane obtained in step 2 was hot-pressed at 100°C, and then placed in a vacuum drying oven at 60°C for 12 hours to completely evaporate the solvent to obtain a sodium ion battery separator.

[0057] The SEM image of the Pebax / PAN composite fiber membrane prepared in this example is shown in FIG. Figure 1 As shown by Figure 1 It can be seen that the electrospun membrane presents a uniform fiber shape.

[0058] Assemble a half-cell, where the positive electrode material is sodium ferrite (NFM), the negative electrode is sodium metal, and the electrode loading is 10 mg / cm 2 At a current density of 0.2C, the first-cycle coulombic efficiency is 98%. After 200 cycles, the battery maintains 106.95mAh / g, and the capacity retention rate reaches 82%.

[0059] Example 2

[0060] The preparation method of the sodium ion battery separator of this embodiment comprises the following steps:

[0061] Step 1: Prepare the spinning solution: dissolve commercially available Pebax particles in DMF, stir continuously at 70°C for 5 hours, and use a magnetic stirrer at a speed of 300 rpm. After the Pebax particles are dissolved, add PAN powder with a mass ratio of 4:6, stir at room temperature for 12 hours, and use a magnetic stirrer at a speed of 400 rpm to obtain a uniform spinning solution.

[0062] Step 2 Preparation of Pebax / PAN composite fiber membrane: Take 10 mL of the spinning solution with a solid content of 10% in step 1, adjust the spinning voltage to 16 kV, the spinning distance to 14 cm, and the solution flow rate to 0.1 mm / min, and then perform electrospinning to obtain a uniform Pebax / PAN composite fiber membrane.

[0063] Step 3: Treatment of the Pebax / PAN composite fiber membrane: The Pebax / PAN composite fiber membrane obtained in step 2 was hot-pressed at 100°C, and then placed in a vacuum drying oven at 60°C for 12 hours to completely evaporate the solvent to obtain a sodium ion battery separator.

[0064] The SEM image of the Pebax / PAN composite fiber membrane prepared in this example is shown in FIG. Figure 2 As shown by Figure 2 It can be seen that the electrospun membrane only presents a partially uniform fiber shape and has serious agglomeration.

[0065] Example 3

[0066] The preparation method of the sodium ion battery separator of this embodiment comprises the following steps:

[0067] Step 1: Prepare the spinning solution: dissolve commercially available Pebax particles in DMF, stir continuously at 70°C for 5 hours, and use a magnetic stirrer at a speed of 300 rpm. After the Pebax particles are dissolved, add PAN powder with a mass ratio of 1:1, stir at room temperature for 12 hours, and use a magnetic stirrer at a speed of 400 rpm to obtain a uniform spinning solution.

[0068] Step 2 Preparation of Pebax / PAN composite fiber membrane: Take 5 mL of the spinning solution with a solid content of 12% in step 1, adjust the spinning voltage to 16 kV, the spinning distance to 14 cm, and the solution flow rate to 0.1 mm / min, and then perform electrospinning to obtain a uniform Pebax / PAN composite fiber membrane.

[0069] Step 3: Treatment of the Pebax / PAN composite fiber membrane: The Pebax / PAN composite fiber membrane obtained in step 2 was hot-pressed at 100°C, and then placed in a vacuum drying oven at 60°C for 12 hours to completely evaporate the solvent to obtain a sodium ion battery separator.

[0070] Test Example 1

[0071] The diameter, liquid absorption rate, electrolyte wettability, and cycle performance of the sodium ion battery separator prepared in Example 1 were measured. The separator fiber diameter was 180 nm. As shown in Table 1, the liquid absorption rate of the PAN / Pebax membrane was as high as 772.3% compared to other separators. Figure 3 It can be seen from the contact angle test that the contact angle of PAN / Pebax membrane is about 0° within 0.1s, showing excellent wettability to the electrolyte.

[0072] Table 1

[0073] PAN / Pebax PP PAN Before aspiration 2.2 3.06 6.71 After aspiration 19.19 9.65 39.53 Liquid absorption rate 772.3％ 215.4％ 489.1％

[0074] Test Example 2

[0075] A sodium ion battery was assembled with a sodium ferrite positive electrode, a sodium metal negative electrode and the sodium ion battery separator prepared in Example 1, and the electrochemical performance was tested. Figure 4 It can be seen that at a current density of 0.2C, the first cycle coulombic efficiency is 98%. After 200 cycles, the battery maintains 106.95mAh / g, and the capacity retention rate reaches 82%.

[0076] The above descriptions are merely a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application discloses the preferred embodiments as above, they are not intended to limit the present application. Any technical personnel familiar with the present profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing a sodium ion battery separator, characterized in that: The preparation method comprises the following steps: (1) stirring a mixture containing polyether block polyamide, polyacrylonitrile, and a solvent to obtain a spinning solution; (2) subjecting the spinning solution to electrospinning, hot pressing, and drying to obtain the sodium ion battery separator; In the step (1), the mass ratio of the polyether block polyamide to the polyacrylonitrile is 3-7:7-3; In the step (2), the electrospinning conditions are: The electrospinning voltage is 12~20kV, the spinning speed is 0.05~0.15mm / min, and the spinning receiving distance is 10~18cm; In the step (2), the temperature of the hot pressing is 80-120°C.

2. The preparation method according to claim 1, characterized in that In the step (1), the solid content of the spinning solution is 10-16%.

3. The preparation method according to claim 1, characterized in that In the step (2), the drying temperature is 60-80° C., and the drying time is 10-24 h.

4. The preparation method according to claim 1, characterized in that In the step (1), the stirring time is 10 to 24 hours, and the stirring speed is 200 to 600 rpm.

5. The preparation method according to claim 1, characterized in that In the step (1), the solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, acetone, and isopropyl alcohol.

6. The sodium ion battery separator prepared by the preparation method according to any one of claims 1 to 5, characterized in that: The fiber diameter of the sodium ion battery separator is 100-400 nm.

7. The sodium ion battery separator according to claim 6, characterized in that The liquid absorption rate of the sodium ion battery separator is 700% to 800%.

8. Use of the sodium ion battery separator according to claim 6 or 7 in a sodium ion battery, characterized in that: The sodium ion battery comprises a sodium ferrite positive electrode, a sodium ion battery separator and a sodium metal negative electrode.

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