Glass fiber / amphoteric polysaccharide nanofiber composite separator for sodium battery and preparation method thereof

Abstract

The application provides a preparation method of a glass fiber / amphoteric polysaccharide nanofiber composite diaphragm for a sodium battery. The preparation method is as follows: uniformly dispersing glass fibers in an aqueous solution; adding amphoteric polysaccharide nanofibers into the glass fiber dispersion liquid and uniformly mixing; and obtaining the composite diaphragm by wet papermaking technology, dehydration forming, pressing and drying in the net part. The preparation process is simple and easy to operate, and continuous production can be carried out through existing papermaking industrialization equipment. The composite diaphragm prepared by the application has the advantages of high porosity, uniform pore size, good thermal stability, excellent electrolyte wettability and high mechanical strength, and a large number of functional groups on the amphoteric polysaccharide nanofiber provide binding sites for solvent molecules to bind to the fiber surface, which helps to remove the solvation sheath in the solvation structure of sodium ion, promotes the transport and transfer of sodium ion, and enhances the sodium deposition kinetics.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of sodium battery separators, in particular to a glass fiber / amphoteric polysaccharide nanofiber composite separator for sodium batteries and a preparation method thereof. BACKGROUND

[0002] Sodium batteries (SIBs) are considered as a promising next-generation energy storage system due to their low cost and abundant sodium resources. The separator is an important component that determines the electrochemical performance of sodium ion batteries. The separator physically prevents contact between the anode and the cathode and allows Na + transport between the cathode and the anode. Therefore, the microstructure of the separator and the interface interaction between the electrolyte and the separator have a significant influence on the electrochemical performance of SIBs.

[0003] Generally, an ideal SIBs separator should have the following basic characteristics: 1) excellent mechanical strength, which can withstand the volume deformation during the Na stripping / deposition cycle process; 2) low thickness, which can maintain high energy density under long-term stable cycling; 3) good thermal stability, which can avoid thermal shrinkage and deterioration of mechanical properties; 4) suitable porous structure and modified functional groups to control Na + transport and Na deposition behavior. Traditional polyolefin separators, such as polyethylene and polypropylene, exhibit good performance in lithium ion batteries, but they have poor wettability for carbonate-based electrolytes such as ethylene carbonate and propylene carbonate in SIBs. In addition, polyolefin-based separators usually have a certain thermal shrinkage at high temperatures, which will likely cause internal short circuits. In recent years, glass fiber separators have been widely used in most laboratory-scale studies due to their high porosity, strong ionic conductivity, excellent wettability and thermal stability. However, high brittleness and low tensile strength make it very challenging in the industrial production of batteries such as winding, folding, packaging, etc. In addition, commercial glass fiber separators have a large thickness and occupy a large space in the battery, and are expensive (for example, 100 Whatman GF / C with a diameter of 70 mm requires 450 yuan), which makes it difficult to control the cost of energy density in the unit battery. In addition, the coexistence of high porosity and thickness means that a large amount of electrolyte is needed to fill the internal space to ensure the stable operation of the battery, increasing the risk of leakage of flammable electrolyte. Therefore, it is necessary to develop a new type of glass fiber separator with low cost and excellent comprehensive performance by appropriate regulation for the practical application of SIBs.

[0004] Patent (202210087640.5) discloses a preparation method of a cellulose-based sodium ion battery separator, which uniformly mixes plant fiber slurry and glass fiber solution at a ratio of 6:4, and casts paper from the composite slurry. Its advantages are to improve the mechanical strength, heat resistance and liquid absorption of the separator, and also to increase the sodium ion conductivity of the separator, but the functional groups on the plant fiber are relatively single, the capacity attenuation after cycling is relatively fast, and the capacity retention rate is relatively low. SUMMARY

[0005] In view of the problems of low mechanical strength, high brittleness, large thickness and high price of commercial glass fiber separators, the purpose of the present application is to provide a glass fiber / amphoteric polysaccharide nanofiber composite separator and a preparation method thereof, which have low cost, good mechanical strength and flexibility, ideal thickness, thermal stability and electrolyte wettability, and excellent electrochemical performance. The present application utilizes glass fiber and amphoteric polysaccharide nanofiber to prepare a new type of glass fiber composite separator combined with organic / inorganic phases. The composite separator has good mechanical strength, appropriate thickness, good wettability, high thermal stability and excellent electrochemical performance.

[0006] To achieve the above-mentioned purpose, the technical solutions adopted by the present application are as follows:

[0007] A preparation method of a glass fiber / amphoteric polysaccharide nanofiber composite separator for sodium batteries, comprising the following steps:

[0008] 1) uniformly dispersing glass fiber in an aqueous solution to obtain a glass fiber suspension.

[0009] 2) adding amphoteric polysaccharide nanofiber to the glass fiber suspension of step 1) and mixing uniformly.

[0010] 3) using wet papermaking technology, the glass fiber / amphoteric polysaccharide nanofiber mixture of step 2) is dehydrated and formed on a net, pressed and dried to obtain a glass fiber / amphoteric polysaccharide nanofiber composite separator.

[0011] Preferably, the pH of the dilute sulfuric acid in step 1) is 2.5-7.

[0012] Further preferably, the pH of the dilute sulfuric acid in step 1) is 3-4.

[0013] Preferably, the dispersion mode in step 1) is defibration, and the defibration treatment has a defibration revolution of 5000-50000 and a time of 5-30 min.

[0014] Preferably, the concentration of the glass fiber suspension in step 1) is 0.05-5 wt.%.

[0015] Further preferably, the concentration of the glass fiber suspension in step 1) is 0.1-0.5 wt.%.

[0016] Preferably, the amount of the polysaccharide nanofiber added in step 2) is 5-30% of the absolute dry weight of the glass fiber.

[0017] Further preferably, the amount of the polysaccharide nanofiber added in step 2) is 10-15% of the absolute dry weight of the glass fiber.

[0018] Preferably, the mixing method in step 2) is defibration, and the defibration treatment has a defibration rotation of 5000-50000 and a time of 5-30 min.

[0019] Further preferably, the defibration treatment in step 2) has a defibration rotation of 5000-10000 and a time of 5-10 min.

[0020] Preferably, in step 2), the preparation of the amphoteric polysaccharide nanofiber is as follows:

[0021] 1) Dissolve sodium alginate in water to obtain a solution A, with a concentration of 0.01-10 wt%;

[0022] 2) Dissolve chitosan in an acid solution with a pH of 3-5 to obtain a solution B, with a concentration of 0.01-10 wt%;

[0023] 3) Mix solution A in step 1) and solution B in step 2) according to a mass ratio of (1:1)-(1:5) to obtain a mixed solution C;

[0024] 4) Ultrasonically treat the mixed solution C for 1-8 hours, with an ultrasonic power of 500-750 W, to obtain the amphoteric polysaccharide nanofiber.

[0025] 5) Dry the amphoteric polysaccharide nanofiber obtained in step 4) to obtain a dried amphoteric polysaccharide nanofiber.

[0026] Preferably, in step 3), the drying temperature is 50-150°C, and the drying time is 10 s-30 min.

[0027] Preferably, in step 3), the basis weight of the composite film is 30-80 g / m 2 .

[0028] Further preferably, in step 3), the basis weight of the composite film is 45-55 g / m 2 .

[0029] A glass fiber / polysaccharide nanofiber composite diaphragm for a sodium battery, which is prepared by the above preparation method.

[0030] In the present application, the glass fiber / amphoteric polysaccharide nanofiber composite diaphragm is interwoven by fibers, and presents a three-dimensional network structure, and the glass fiber surface and interior are deposited with a layered porous polysaccharide nanofiber network, so that the combination between the fibers is more compact; the tensile strength of the diaphragm is 4.7-11.4 MPa; and the thickness of the diaphragm is 50-300 μm.

[0031] A sodium battery is assembled by a positive electrode, a negative electrode and the glass fiber / polysaccharide nanofiber composite diaphragm as described above arranged between the positive and negative electrodes.

[0032] Application of the sodium battery as described above in the field of energy storage, the field of power batteries and the field of electronic products.

[0033] The present application utilizes glass fibers and amphoteric polysaccharide nanofibers to prepare a novel glass fiber composite diaphragm combined with organic / inorganic phases. The amphoteric polysaccharide nanofibers are filled in the macropores inside the glass fibers, and mainly play the following roles: (1) uniform pore size, which is beneficial to the uniform deposition of sodium ions; (2) strengthening the internal combination between the glass fibers, improving the stability and mechanical strength of the overall structure of the diaphragm, and the dense membrane structure can make the glass fiber / polysaccharide nanofiber composite diaphragm meet the mechanical strength requirement of the battery at a lower thickness; (3) the rich functional groups (-NH2, -COOH and -OH) on the amphoteric polysaccharide nanofibers provide binding sites for the solvent to bind to the fiber surface, which helps to remove the solvent sheath in the solvation structure of sodium ions, promotes the transport and transfer of sodium ions, enhances the sodium deposition kinetics, and improves the overall performance of the battery. The preparation process of the present application is simple and easy to implement, and can be continuously produced by the existing papermaking industrialization equipment. The sodium battery diaphragm prepared by the present application has the advantages of uniform pore size distribution, high porosity, low thickness, strong thermal stability, excellent electrolyte wettability and high mechanical strength. The composite membrane applied as a diaphragm in a sodium battery presents the characteristics of high capacity, good stability and excellent rate performance.

[0034] The beneficial results of the present application are that the glass fiber / amphoteric polysaccharide nanofiber composite diaphragm nanofiber diaphragm has the characteristics of rich functional groups, high mechanical strength, good wettability and excellent electrochemical performance, and the preparation process is simple and easy to implement, and can be continuously produced by the existing papermaking industrialization equipment.

[0035] Specifically:

[0036] (1) The glass fibers used in the present application are low in cost, and the amphoteric polysaccharide nanofibers are green and environmentally friendly.

[0037] (2) The macropores in the glass fiber of the prepared separator are filled with the three-dimensional network structure formed by the amphoteric polysaccharide nanofiber, which is beneficial to form smaller and more uniform pore structures. Uniform pore size helps to promote uniform deposition and stripping of sodium, so that it still has a required pore size, mechanical strength and flexibility at a lower thickness.

[0038] (3) The prepared composite separator has abundant functional groups, which provide binding sites for solvent molecules in the electrolyte, reduce the desolvation energy barrier of Na + , and is beneficial to the dissolution and transport of sodium ions, so that the overall performance of the battery is improved.

[0039] (4) The prepared separator has excellent mechanical strength and thermal stability, which effectively resists the penetration of dendrites and the contact between the two poles, and improves the overall safety of the battery.

[0040] (5) The prepared separator has good flexibility, which is convenient for the folding and packaging process of the battery, and has practical significance.

[0041] (6) The prepared separator has high capacity, good stability and excellent rate performance when applied to sodium batteries. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 The scanning electron microscope images of Examples 1-4.

[0043] Figure 2 The stress-strain curves of Examples 1-4.

[0044] Figure 3 The mechanical properties and flexibility diagram of Example 2.

[0045] Figure 4 The thickness measurement diagram of Example 2.

[0046] Figure 5 The cycle diagram of Example 2 at a current density of 1.0C.

[0047] Figure 6 The rate cycle diagram of Example 2 at a current density of 0.5-20C. DETAILED DESCRIPTION

[0048] The application will be further explained and described below in conjunction with specific embodiments, but the embodiments of the application are not limited thereto. For parameters and processes not specified, refer to conventional techniques.

[0049] The preparation method of amphoteric polysaccharide nanofiber in the following examples is as follows:

[0050] 1) Dissolve sodium alginate in water to obtain solution A with a concentration of 3wt%.

[0051] 2) Dissolve chitosan in acid solution with pH 4, concentration is 3%, get solution B;

[0052] 3) Mix solution A in step 1) and solution B in step 2) according to mass ratio 1:2, get mixed solution C;

[0053] 4) Ultrasonic treat mixed solution C for 2 hours, ultrasonic power is 600W, then get amphoteric polysaccharide nanofiber.

[0054] Example 1

[0055] A glass fiber / amphoteric polysaccharide nanofiber composite diaphragm for sodium battery, the preparation method comprises the following steps:

[0056] 1) Disperse glass fiber in water solution with pH 3, defibrate 5000 turns to get glass fiber suspension with concentration of 0.2%.

[0057] 2) Add 5% amphoteric polysaccharide nanofiber relative to dry weight of glass fiber, defibrate 5000 turns to get glass fiber / polysaccharide nanofiber mixture.

[0058] 3) According to 50g / m -2 of quantitative, glass fiber / amphoteric polysaccharide nanofiber mixture is used to make paper by wet papermaking technology, through net dehydration forming, pressing and drying to get glass fiber / amphoteric polysaccharide nanofiber composite diaphragm.

[0059] Performance test:

[0060] 1) The scanning electron microscope (SEM) image of the diaphragm of this embodiment is shown in Figure 1 .

[0061] As shown in Figure 1 , the diaphragm is interwoven by fibers, showing a three-dimensional network structure. The surface and interior of glass fiber are deposited with layered porous polysaccharide nanofiber network, making the combination between fibers more compact.

[0062] 2) The stress-strain curve of the diaphragm of this embodiment is shown in Figure 2 .

[0063] As shown in Figure 2 , the tensile strength of the diaphragm is 4.7MPa.

[0064] Example 2

[0065] A glass fiber / amphoteric polysaccharide nanofiber composite diaphragm for sodium battery, the preparation method comprises the following steps:

[0066] 1) Disperse glass fibers in water solution with pH = 3.5 for 5000 revolutions to obtain a glass fiber suspension with a concentration of 0.2%.

[0067] 2) Add 10% of amphoteric polysaccharide nanofibers relative to the dry weight of glass fibers, and disperse for 5000 revolutions to obtain a glass fiber / polysaccharide nanofiber mixture.

[0068] 3) Use the glass fiber / amphoteric polysaccharide nanofiber mixture to make a wet papermaking technology with a quantitative amount of 50 g / m -2 , and through the net dehydration forming, pressing, and drying to obtain a glass fiber / amphoteric polysaccharide nanofiber composite diaphragm.

[0069] Performance test:

[0070] 1) The SEM image of the diaphragm of this embodiment is shown in Figure 1 .

[0071] As can be seen from Figure 1 , the diaphragm is interwoven by fibers, showing a three-dimensional network structure. The glass fiber surface and interior deposit a layered porous polysaccharide nanofiber network, making the combination between fibers more compact.

[0072] 2) The stress-strain curves of the diaphragm of this embodiment are shown in Figure 2 .

[0073] As can be seen from Figure 2 , the tensile strength of the diaphragm is 7.2 MPa.

[0074] 3) The mechanical property diagram of the diaphragm of this embodiment is shown in Figure 3 .

[0075] As shown in Figure 3 , the diaphragm has a certain flexibility and exhibits excellent liquid disintegration resistance.

[0076] 4) The thickness measurement diagram of the diaphragm of this embodiment is shown in Figure 4 .

[0077] As shown in Figure 4 , the thickness of the diaphragm is 100 μm, which is much lower than the thickness of GF / A and GF / D diaphragms.

[0078] 5) The cycle of Na / / NaV2(PO4)3 battery assembled by the diaphragm of this embodiment at 1.0C is shown in Figure 5 .

[0079] As shown in Figure 5 , the initial specific capacity of the Na / / NaV2(PO4)3 battery assembled by the diaphragm at 1.0C is 102.7 mAh g -1, the capacity retention rate is close to 100% and the coulombic efficiency is close to 100% after 500 cycles. The cycle performance is better than that of the GF / A and GF / D separators.

[0080] 6) The cycle performance of the Na / / NaV2(PO4)3 battery assembled with the separator of the embodiment at 0.5-20C is shown in Figure 6 .

[0081] As shown in Figure 6 : the specific capacity at the current density of 0.5, 1.0, 2.0, 5.0, 10, 20C is 107.6, 105.8, 103.2, 97.7, 90.5 and 78.6 mAh g -1 , respectively. When the current is changed from 20C to 0.5C, the specific capacity is restored to 107.4 mAh g -1 . The rate performance is better than that of the GF / A and GF / D separators.

[0082] Embodiment 3

[0083] A glass fiber / polysaccharide nanofiber composite separator for a sodium battery, a preparation method thereof comprises the following steps:

[0084] 1) Disperse glass fibers in an aqueous solution with pH = 3.5 to defibrate 10,000 revolutions to obtain a glass fiber suspension with a concentration of 0.1%.

[0085] 2) Add 15% of amphoteric polysaccharide nanofibers relative to the dry weight of the glass fibers, defibrate 10,000 revolutions to obtain a glass fiber / amphoteric polysaccharide nanofiber mixture.

[0086] 3) Quantify the glass fiber / amphoteric polysaccharide nanofiber mixture at 50 g m -2 -1 , and use wet papermaking technology to form, press and dry the glass fiber / amphoteric polysaccharide nanofiber composite separator.

[0087] Performance test:

[0088] 1) The SEM image of the separator of the embodiment is shown in Figure 1 .

[0089] As can be seen from Figure 1 : the separator is interwoven by fibers, showing a three-dimensional network structure. The glass fiber surface and the inside are deposited with a layered porous polysaccharide nanofiber network, making the combination between the fibers more compact.

[0090] 2) The stress-strain curves of the separator of the embodiment are shown in Figure 2 .

[0091] As can be seen from Figure 2 : the tensile strength of the separator is 8.1 MPa.

[0092] Example 4

[0093] A glass fiber / polysaccharide nanofiber composite separator for sodium batteries, the preparation method comprising the following steps:

[0094] 1) Glass fibers are dispersed in an aqueous solution with pH = 2.5 and defibrated for 5000 revolutions to obtain a glass fiber suspension with a concentration of 0.5%.

[0095] 2) Add 20% of amphoteric polysaccharide nanofibers relative to the absolute dry weight of glass fibers, defibrate for 10000 revolutions to obtain a glass fiber / polysaccharide nanofiber mixture.

[0096] 3) The glass fiber / amphoteric polysaccharide nanofiber mixture is used in wet papermaking technology with a quantitative amount of 50g / m -2 , and is formed into a glass fiber / amphoteric polysaccharide nanofiber composite separator through web dewatering, pressing and drying.

[0097] Performance test:

[0098] 1) The SEM image of the separator of this embodiment is shown in Figure 1 .

[0099] As can be seen from Figure 1 : The separator is interwoven by fibers, showing a three-dimensional network structure. The glass fiber surface and the inside are deposited with a layered porous polysaccharide nanofiber network, making the combination between fibers more compact.

[0100] 2) The stress-strain curves of the separator of this embodiment are shown in Figure 2 .

[0101] As can be seen from Figure 2 : The tensile strength of the separator is 11.4MPa.

[0102] Example 5

[0103] A glass fiber / polysaccharide nanofiber composite separator for sodium batteries, the preparation method comprising the following steps:

[0104] 1) Glass fibers are dispersed in an aqueous solution with pH = 2.5 and defibrated for 10000 revolutions to obtain a glass fiber suspension with a concentration of 0.5%.

[0105] 2) Add 30% of amphoteric polysaccharide nanofibers relative to the absolute dry weight of glass fibers, defibrate for 10000 revolutions to obtain a glass fiber / polysaccharide nanofiber mixture.

[0106] 3) The glass fiber / amphoteric polysaccharide nanofiber mixture is used in wet papermaking technology with a quantitative amount of 50g / m -2 , and is formed into a glass fiber / amphoteric polysaccharide nanofiber composite separator through web dewatering, pressing and drying.

[0107] Example 6

[0108] A glass fiber / polysaccharide nanofiber composite separator for sodium batteries, the preparation method comprising the following steps:

[0109] 1) Glass fibers are dispersed in an aqueous solution with pH = 3 and defibrated for 5000 revolutions to obtain a glass fiber suspension with a concentration of 0.2%.

[0110] 2) Add 10% of amphoteric polysaccharide nanofibers relative to the absolute dry weight of glass fibers, defibrate for 5000 revolutions to obtain a glass fiber / polysaccharide nanofiber mixture.

[0111] 3) The glass fiber / amphoteric polysaccharide nanofiber mixture is quantified at 60 g / m -2 The glass fiber / amphoteric polysaccharide nanofiber composite separator is obtained by using wet papermaking technology, through web dewatering forming, pressing, and drying.

[0112] Example 7

[0113] A glass fiber / polysaccharide nanofiber composite separator for sodium batteries, the preparation method comprising the following steps:

[0114] 1) Glass fibers are dispersed in an aqueous solution with pH = 3 and defibrated for 5000 revolutions to obtain a glass fiber suspension with a concentration of 0.5%.

[0115] 2) Add 10% of amphoteric polysaccharide nanofibers relative to the absolute dry weight of glass fibers, defibrate for 5000 revolutions to obtain a glass fiber / polysaccharide nanofiber mixture.

[0116] 3) The glass fiber / amphoteric polysaccharide nanofiber mixture is quantified at 40 g / m -2 The glass fiber / amphoteric polysaccharide nanofiber composite separator is obtained by using wet papermaking technology, through web dewatering forming, pressing, and drying.

[0117] Comparative Example 1

[0118] 1) Glass fibers are dispersed in an aqueous solution with pH = 3.5 and defibrated for 5000 revolutions to obtain a glass fiber suspension with a concentration of 0.2%.

[0119] 2) The glass fiber / amphoteric polysaccharide nanofiber mixture is quantified at 50 g / m -2 The glass fiber / amphoteric polysaccharide nanofiber composite separator is obtained by using wet papermaking technology, through web dewatering forming, pressing, and drying.

[0120] Performance test:

[0121] 1) The SEM image of the separator of this example is shown in Figure 1 .

[0122] It can be seen that the diaphragm is interwoven by fibers, showing a three-dimensional network structure, large and irregular pore size. Figure 1

[0123] 2) The stress-strain curves of the diaphragm of the example are shown in Figure 2

[0124] It can be seen that the tensile strength of the diaphragm is 1.1 MPa. Figure 2

[0125] 3) The cycle of the Na / / NaV2(PO4)3 battery assembled by the diaphragm of the comparative example at 1.0C is shown in Figure 5

[0126] As shown in Figure 5 : the initial specific capacity of the Na / / NaV2(PO4)3 battery assembled by the GF diaphragm at 1.0C is 99.3 mAh g -1 , the coulombic efficiency fluctuates greatly, the specific capacity decreases rapidly, and a short circuit occurs in less than 100 cycles.

[0127] Comparative Example 2

[0128] 1) The glass fibers were dispersed in an aqueous solution with pH=3 and defibered for 10,000 revolutions to obtain a glass fiber suspension with a concentration of 0.5%.

[0129] 2) The glass fiber / amphoteric polysaccharide nanofiber mixture was quantified at 60 g m -2 -1, and a glass fiber / amphoteric polysaccharide nanofiber composite diaphragm was obtained by wet papermaking technology, through web dewatering forming, pressing, and drying.

[0130] The above examples are the preferred embodiments of the present application, but the embodiments of the present application are not limited by the above examples, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application are equivalent replacement methods, and are all included in the protection scope of the present application.​​​​

Claims

1. A method for preparing a glass fiber / amphoteric polysaccharide nanofiber composite separator for a sodium battery, characterized by, The method comprises the following steps: 1) uniformly dispersing glass fibers in an aqueous solution to obtain a glass fiber suspension; 2) adding zwitterionic polysaccharide nanofibers to the glass fiber suspension of step 1) and uniformly mixing; the preparation steps of the zwitterionic polysaccharide nanofibers are as follows: ① dissolving sodium alginate in water to obtain solution A, with a concentration of 0.01-10 wt%; ② dissolving chitosan in an acid solution with a pH of 3-5 to obtain solution B, with a concentration of 0.01-10 wt%; ③ mixing solution A in step ① and solution B in step ② according to a mass ratio of (1:1)-(1:5) to obtain a mixed solution C; ④ ultrasonically treating the mixed solution C for 1-8 hours at an ultrasonic power of 500-750 W to obtain zwitterionic polysaccharide nanofibers; 3) using a wet papermaking technology to form the glass fiber / zwitterionic polysaccharide nanofiber mixture liquid into a glass fiber / zwitterionic polysaccharide nanofiber composite diaphragm through a wire section dehydration forming, pressing and drying.

2. The method of claim 1, wherein the glass fiber / amphoteric polysaccharide nanofiber composite separator for sodium batteries is characterized by, In step 1), the pH of the aqueous solution is 2.5-7, which is adjusted by sulfuric acid, and the concentration of the glass fiber suspension is 0.05-5 wt.%.

3. The method of claim 1, wherein the glass fiber / amphoteric polysaccharide nanofiber composite separator for sodium batteries is characterized by, In step 2), the addition amount of the zwitterionic polysaccharide nanofibers is 5%-30% of the absolute dry weight of the glass fibers.

4. The method of claim 1, wherein the glass fiber / amphoteric polysaccharide nanofiber composite separator for sodium batteries is characterized by, In step 3), the drying temperature is 50-150°C, and the drying time is 10 s-30 min.

5. The method of claim 1, wherein the glass fiber / amphoteric polysaccharide nanofiber composite separator for sodium batteries is characterized by, In step 3), the complex separator is quantified at 30-80 g / m 2 .

6. A glass fiber / zwitterionic polysaccharide nanofiber composite diaphragm for a sodium battery, which is prepared by the preparation method of any one of claims 1-5.

7. The glass fiber / amphoteric polysaccharide nanofiber composite separator for sodium battery according to claim 6, characterized in that, The glass fiber / zwitterionic polysaccharide nanofiber composite diaphragm is formed by interweaving fibers and presents a three-dimensional network structure, and the surface and interior of the glass fibers are deposited with a layered porous polysaccharide nanofiber network, so that the combination between the fibers is more compact; The tensile strength of the diaphragm is 4.7-11.4 MPa, and the thickness of the diaphragm is 50-300 μm.

8. A sodium battery, characterized by, 7. A sodium battery comprising a positive electrode, a negative electrode and the glass fiber / zwitterionic polysaccharide nanofiber composite diaphragm of claim 6 arranged between the positive electrode and the negative electrode.

9. Use of the sodium battery of claim 8 in the fields of energy storage, power batteries and electronic products.

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