A sulfonated nanocellulose / polyvinylidene fluoride electrolyte film and a preparation method and application thereof

Abstract

This invention provides a sulfonated nanocellulose / polyvinylidene fluoride electrolyte film, its preparation method, and its application. The sulfonated preparation method includes the following steps: (1) dispersing sulfonated nanocellulose, conductive carbon black, polyvinylidene fluoride, and zinc trifluoromethanesulfonate in water to obtain a mixed solution; (2) heating the mixed solution, adding an organic solvent, and mixing evenly to obtain a sulfonated nanocellulose / polyvinylidene fluoride electrolyte slurry; (3) pouring the sulfonated nanocellulose / polyvinylidene fluoride electrolyte slurry into a mold, and drying it after the liquid self-leveling surface is smooth and in full contact with the mold to obtain a sulfonated nanocellulose / polyvinylidene fluoride electrolyte film. The sulfonated nanocellulose / polyvinylidene fluoride electrolyte film obtained by this invention can be directly used as an electrolyte under low water content conditions, and can achieve better results with external water and electrolyte supplementation.

Description

Technical Field

[0001] This invention relates to the field of zinc and battery technology, and in particular to a sulfonated nanocellulose / polyvinylidene fluoride electrolyte film, its preparation method, and its application. Background Technology

[0002] With rapid economic and social development, people's demand for energy is increasing daily. Currently, energy supply still relies heavily on traditional fossil fuels such as coal and oil. These non-renewable energy sources face two core problems: over-exploitation violates the concept of sustainable development and will eventually lead to resource depletion; combustion processes emit large amounts of pollutants, causing ecological problems such as the greenhouse effect and air pollution. Against this backdrop, renewable energy sources such as wind, solar, and tidal power have become the core direction of energy transformation due to their sustainability advantages. However, the inherent dispersion, randomness, and intermittency of these energy sources make it difficult for their power generation output to match the stable electricity demand of users and industrial scenarios, severely restricting large-scale application. Therefore, developing efficient energy storage systems to achieve flexible storage and stable transmission of renewable energy has become a key approach to breaking through the bottlenecks of energy transformation.

[0003] Among various novel energy storage devices, aqueous zinc-ion batteries have rapidly become a research hotspot due to their outstanding characteristics such as high safety performance, low cost, and abundant zinc resources. However, their large-scale application still faces severe challenges: during the charge-discharge cycle, the zinc anode is prone to problems such as disordered growth of zinc dendrites, hydrogen evolution side reactions, and surface passivation. These phenomena can significantly damage structural integrity and drastically shorten battery life, becoming the core bottleneck hindering the technology's implementation.

[0004] As one of the core components of a battery, the electrolyte plays multiple crucial roles, including isolating the positive and negative electrodes, storing the electrolyte, and constructing ion transport channels. Its performance directly determines the battery's charge-discharge cycle stability and long-term reliability. Currently, the research depth and breadth of understanding on separator modification in the field of aqueous zinc-ion batteries are still insufficient. Although the mainstream glass fiber separator has advantages such as excellent electrolyte wettability and low interfacial resistance, it suffers from structural defects such as excessive porosity and uneven pore size distribution. This easily induces uneven zinc ion deposition, which in turn exacerbates zinc dendrite growth and severely limits the improvement of battery cycle life. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a sulfonated nanocellulose / polyvinylidene fluoride electrolyte film, its preparation method, and its application, to solve the problem of poor cycle stability and short lifespan caused by structural defects such as excessive porosity and uneven pore size distribution of glass fiber separators in existing aqueous zinc-ion batteries.

[0006] To achieve the above and other related objectives, the present invention provides a method for preparing a sulfonated nanocellulose / polyvinylidene fluoride electrolyte film, comprising the following steps:

[0007] (1) Disperse sulfonated nanocellulose, conductive carbon black, polyvinylidene fluoride and zinc trifluoromethanesulfonate in water to obtain a mixed solution;

[0008] (2) Heat the mixture, add an organic solvent, and mix evenly to obtain sulfonated nanocellulose / polyvinylidene fluoride electrolyte slurry;

[0009] (3) Pour the sulfonated nanocellulose / polyvinylidene fluoride electrolyte slurry into the mold. After the liquid self-leveling surface is flat and in full contact with the mold, dry it to obtain the sulfonated nanocellulose / polyvinylidene fluoride electrolyte film.

[0010] This invention combines sulfonated cellulose nanoparticles with the polymer polyvinylidene fluoride (PVDF) to form a thin film with excellent mechanical properties. The abundant sulfonic acid groups on the sulfonated cellulose nanoparticles provide zinc ion migration sites, while the hydrogen bonds between the sulfonic acid groups and the excellent film-forming properties of PVDF solve problems such as dendrite growth and hydrogen evolution reactions caused by uneven zinc ion deposition. Uniform zinc ion deposition is achieved, and the excellent mechanical properties of the electrolyte film prevent short circuits caused by zinc dendrite penetration. Furthermore, the minimal water content within this system inhibits side reactions between water molecules and zinc metal, effectively extending the cycle stability and lifespan of zinc-ion batteries.

[0011] Preferably, in step (1), sulfonated nanocellulose is first dispersed in water to obtain an aqueous dispersion of sulfonated nanocellulose; then conductive carbon black, polyvinylidene fluoride and zinc trifluoromethanesulfonate are added to the aqueous dispersion of sulfonated nanocellulose.

[0012] Preferably, in step (1), the mass fraction of the aqueous dispersion of sulfonated nanocellulose is 1~1.1%; the content of sulfonated nanocellulose sulfonic acid groups in the aqueous dispersion of sulfonated nanocellulose is 1.2~1.5 mmol / g.

[0013] Preferably, in step (1), the polyvinylidene fluoride has a molecular weight of 900,000 to 1,000,000 and a particle size of 20 to 30 µm.

[0014] Preferably, in step (2), the heating temperature is 55~65℃ and the heating time is 4~5h.

[0015] Preferably, in step (2), the organic solvent is N-methylpyrrolidone or dimethylformamide; the drying temperature is 55~65℃ and the drying time is 8~12h.

[0016] Preferably, the mass ratio of the sulfonated nanocellulose aqueous dispersion, polyvinylidene fluoride, conductive carbon black, and organic solvent is (25~35):(0.5~1):(0.02~0.03):(10~10.5), more preferably 30:1:0.025:10.3.

[0017] Preferably, polyvinylidene fluoride powder is slowly added to the sulfonated nanocellulose aqueous dispersion while stirring. After the powder is relatively uniformly dispersed, N-methylpyrrolidone is slowly added dropwise to achieve optimal solubility and solution uniformity.

[0018] The present invention also provides a sulfonated nanocellulose / polyvinylidene fluoride electrolyte film prepared by the above preparation method.

[0019] This invention also provides an application of sulfonated nanocellulose / polyvinylidene fluoride electrolyte film as a separator in the preparation of aqueous zinc-ion batteries.

[0020] Preferably, no electrolyte is added to the aqueous zinc-ion battery.

[0021] Preferably, the sulfonated nanocellulose / polyvinylidene fluoride electrolyte membrane is immersed in a zinc trifluoromethanesulfonate solution before preparation.

[0022] Preferably, the concentration of the zinc trifluoromethanesulfonate solution is 1.5~3 mol / L, and the soaking time is 12~24h.

[0023] As described above, the present invention has the following beneficial effects:

[0024] (1) The raw materials are widely available and inexpensive. The synthesis and preparation process is simple and mild, and can be prepared on a large scale as needed.

[0025] (2) The sulfonated nanocellulose / polyvinylidene fluoride electrolyte film prepared by the present invention has abundant zinc ion transport channels, which is conducive to uniform zinc ion deposition and promotes the performance improvement of aqueous zinc ion batteries.

[0026] (3) The sulfonated nanocellulose / polyvinylidene fluoride electrolyte film prepared by the present invention has excellent mechanical properties and maintains good performance even when bent and folded, and has considerable prospects for application in flexible devices.

[0027] (4) The sulfonated nanocellulose / polyvinylidene fluoride electrolyte membrane prepared by the present invention can be used directly as an electrolyte under the condition of low water content, and can achieve better results with the supplementation of external water and electrolyte. Attached Figure Description

[0028] Figure 1The images shown are surface SEM images and macroscopic photographs of the sulfonated nanocellulose / polyvinylidene fluoride electrolyte film prepared in Example 1.

[0029] Figure 2 The image shown is an infrared spectrum of the sulfonated nanocellulose / polyvinylidene fluoride electrolyte film prepared in Example 1.

[0030] Figure 3 The tensile stress-strain graphs are shown for the sulfonated nanocellulose / polyvinylidene fluoride electrolyte membranes of Examples 1 and 2, and the commercial glass fiber membranes of the comparative example.

[0031] Figure 4 The sulfonated nanocellulose / polyvinylidene fluoride electrolyte membrane shown in Example 1 and the glass fiber separator of the comparative example were respectively assembled into symmetrical cells at 0.2 mA cm⁻¹. -2 0.2 mA h cm -2 Time-voltage cycle diagrams under current density and rate conditions.

[0032] Figure 5 The sulfonated nanocellulose / polyvinylidene fluoride electrolyte membrane shown in Example 1 and the glass fiber membrane of the comparative example were respectively assembled into Zn / / (NH4)2V 10 O 25 ·8H2O full cell at 1 A g -1 With 2 Ag -1 Cycle count-specific capacity cycle diagram at current density. Detailed Implementation

[0033] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0034] It should be noted that the process equipment or apparatus not specifically mentioned in the following embodiments are all conventional equipment or apparatus in the art.

[0035] Furthermore, it should be understood that the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, does not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, unless otherwise stated. It should also be understood that the combined connection relationship between one or more devices / apparatus mentioned in this invention does not preclude the existence of other devices / apparatus before or after the combined devices / apparatus, or the insertion of other devices / apparatus between these explicitly mentioned devices / apparatus, unless otherwise stated. Moreover, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or limiting the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0036] Example 1

[0037] This application provides a method for preparing a sulfonated nanocellulose / polyvinylidene fluoride electrolyte film, comprising the following steps:

[0038] (1) Add 30 g of sulfonated nanocellulose dispersion (mass fraction of 1%~1.1%, sulfonic acid group content of 1.2 mmol / g~1.5 mmol / g), 1.5 g of zinc trifluoromethanesulfonate powder, and 2.5 mg of conductive carbon black (ECP) to a 100 ml glass beaker. Stir at 60 ℃ and 600 rpm for 15 min to obtain a mixture;

[0039] (2) Take 1 g of polyvinylidene fluoride powder (PVDF-HSV-900) and slowly add it to the stirred mixture. After stirring for 10 min at 60℃ and 600 rpm, take 10 ml of N-methylpyrrolidone (NMP) and slowly add it dropwise. After the addition is complete, stir on a constant temperature stirring table at 60℃ and 600 rpm for 6 h until the PVDF powder is completely dissolved and the solution is uniform and free of particles. Sulfonated nanocellulose / polyvinylidene fluoride composite electrolyte slurry is obtained.

[0040] (3) Pour the stirred sulfonated nanocellulose / polyvinylidene fluoride composite electrolyte slurry into a Teflon mold (10 cm * 3 cm). After the liquid self-leveling surface is smooth and in full contact with the mold, transfer it to a forced-air drying oven and dry it at 60 ℃ for 10 h. Remove the mold and peel off the dried sulfonated nanocellulose / polyvinylidene fluoride electrolyte film.

[0041] Example 2

[0042] This application provides a method for preparing a sulfonated nanocellulose / polyvinylidene fluoride electrolyte film, comprising the following steps:

[0043] (1) Add 30 g of sulfonated nanocellulose aqueous dispersion (mass fraction of 1%~1.1%, sulfonic acid group content of 1.2 mmol / g~1.5 mmol / g), 1.5 g of zinc trifluoromethanesulfonate powder, and 2.5 mg of conductive carbon black (ECP) to a 100 ml glass beaker. Stir at 60 ℃ and 600 rpm for 15 min to obtain a mixture;

[0044] (2) Take 0.5 g of polyvinylidene fluoride powder (PVDF-HSV-900) and slowly add it to the stirred mixture. After stirring for 10 min at 60 ℃ and 600 rpm, take 5 ml of N-methylpyrrolidone (NMP) and slowly add it dropwise. After the addition is complete, stir on a constant temperature heating stirring table at 60 ℃ and 600 rpm for 6 h until the PVDF powder is completely dissolved and the solution is uniform and free of particles, to obtain sulfonated nanocellulose / polyvinylidene fluoride composite electrolyte slurry;

[0045] (3) Take out the stirred solution and pour it into a Teflon mold (10 cm * 3 cm). After the liquid self-levels and is in full contact with the mold, transfer it to a forced-air drying oven and dry it at 60 ℃ for 10 h. Remove the mold and peel off the dried sulfonated nanocellulose / polyvinylidene fluoride electrolyte film;

[0046] Example 3

[0047] This application provides a method for preparing a sulfonated nanocellulose / polyvinylidene fluoride electrolyte film, comprising the following steps:

[0048] (1) Add 30 g of sulfonated nanocellulose dispersion (mass fraction of 1%~1.1%, sulfonic acid group content of 1.6 mmol / g), 1.5 g of zinc trifluoromethanesulfonate powder, and 2.5 mg of conductive carbon black (ECP) to a 100 ml glass beaker. Stir for 15 min at 60 ℃ and 600 rpm to obtain a mixture;

[0049] (2) Take 1 g of polyvinylidene fluoride powder (PVDF-HSV-900) and slowly add it to the stirred mixture. After stirring for 10 min at 60℃ and 600 rpm, take 10 ml of N-methylpyrrolidone (NMP) and slowly add it dropwise. After the addition is complete, stir on a constant temperature stirring table at 60℃ and 600 rpm for 6 h until the PVDF powder is completely dissolved and the solution is uniform and free of particles. Sulfonated nanocellulose / polyvinylidene fluoride composite electrolyte slurry is obtained.

[0050] (3) Take out the stirred solution and pour it into a Teflon mold (10 cm * 3 cm). After the liquid self-levels and is in full contact with the mold, transfer it to a forced-air drying oven and dry it at 60 ℃ for 10 h. Remove the mold and peel off the dried sulfonated nanocellulose / polyvinylidene fluoride electrolyte film;

[0051] Example 4

[0052] This application provides a method for preparing a sulfonated nanocellulose / polyvinylidene fluoride electrolyte film, comprising the following steps:

[0053] (1) Add 30 g of sulfonated nanocellulose dispersion (mass fraction of 1%~1.1%, sulfonic acid group content of 1.6 mmol / g), 1.5 g of zinc trifluoromethanesulfonate powder, and 2.5 mg of conductive carbon black (ECP) to a 100 ml glass beaker. Stir for 15 min at 60 ℃ and 600 rpm to obtain a mixture;

[0054] (2) Take 1 g of polyvinylidene fluoride powder (PVDF-HSV-900) and slowly add it to the stirred mixture. After stirring for 10 min at 60℃ and 600 rpm, take 10 ml of dimethylformamide (DMF) and slowly add it dropwise. After the addition is complete, stir on a constant temperature heating and stirring table at 60℃ and 600 rpm for 4 h until the PVDF powder is completely dissolved and the solution is uniform and free of particles. Sulfonated nanocellulose / polyvinylidene fluoride composite electrolyte slurry is obtained.

[0055] (3) Take out the stirred solution and pour it into a Teflon mold (10 cm * 3 cm). After the liquid self-levels and is in full contact with the mold, transfer it to a forced-air drying oven and dry it at 60 ℃ for 10 h. Remove the mold and peel off the dried sulfonated nanocellulose / polyvinylidene fluoride electrolyte film;

[0056] (4) Cut the dried sulfonated nanocellulose / polyvinylidene fluoride electrolyte film into pieces (12 mm diameter round pieces) and soak them in 3 mol / L zinc trifluoromethanesulfonate solution for 24 h.

[0057] Example 5

[0058] This application provides a method for preparing a sulfonated nanocellulose / polyvinylidene fluoride electrolyte film, comprising the following steps:

[0059] (1) Add 30 g of sulfonated nanocellulose dispersion (mass fraction of 1%~1.1%, sulfonic acid group content of 1.6 mmol / g), 1.5 g of zinc trifluoromethanesulfonate powder, and 2.5 mg of conductive carbon black (ECP) to a 100 ml glass beaker. Stir for 15 min at 60 ℃ and 600 rpm to obtain a dispersion of sulfonated nanocellulose, zinc trifluoromethanesulfonate, and ECP.

[0060] (2) Take 1 g of polyvinylidene fluoride powder (PVDF-HSV-900) and slowly add it to the sulfonated nanocellulose, zinc trifluoromethanesulfonate, and ECP dispersion that is being stirred. After stirring at 60 ℃ and 600 rpm for 10 min, take 10 ml of N-methylpyrrolidone (NMP) and slowly add it dropwise. After the addition is complete, stir on a constant temperature stirring table at 60 ℃ and 600 rpm for 6 h until the PVDF powder is completely dissolved and the solution is homogeneous and free of particles. Sulfonated nanocellulose / polyvinylidene fluoride composite electrolyte slurry is obtained.

[0061] (3) Take out the stirred solution and pour it into a Teflon mold (10 cm * 3 cm). After the liquid self-levels and is in full contact with the mold, transfer it to a forced-air drying oven and dry it at 60 ℃ for 10 h. Remove the mold and peel off the dried sulfonated nanocellulose / polyvinylidene fluoride electrolyte film;

[0062] (4) Cut the dried sulfonated nanocellulose / polyvinylidene fluoride electrolyte film into 12 mm diameter discs. Use them directly as electrolytes.

[0063] Comparative Example

[0064] The comparative example used a commercially available glass fiber diaphragm, which was purchased from Whatman, model GF / D, with a pore size of 2.7 µm and a thickness of 675 µm.

[0065] The sulfonated nanocellulose / polyvinylidene fluoride electrolyte membranes prepared in Examples 1-5 and the commercial glass fiber diaphragm of the comparative example were cut into discs with a diameter of 12 mm. The discs of Examples 1-4 were immersed in a 3 mol / L zinc trifluoromethanesulfonate solution for 24 h. The disc of Example 5 was not treated in any way. 120 µL of 3 mol / L zinc trifluoromethanesulfonate electrolyte was dropped onto the disc of the comparative example.

[0066] Assemble the batteries using the processed wafers as follows:

[0067] (1) Prepare the negative electrode shell, funnel spring (size 15.4 mm*1.2 mm), gasket (size 15.8 mm*0.5 mm), and positive electrode shell (all purchased from NEWALE, model CR2032).

[0068] (2) Select an 80-micron thick zinc plate and cut it to a size of 1.766 cm. -2 The circular piece was cut from carbon paper to a size of 1.13 cm. -2 A round disc.

[0069] (3) Assemble a symmetrical battery (full cell) in the following order: negative electrode shell, funnel spring, gasket, zinc plate from step (2), the above-treated disc, zinc plate from step (2) (or carbon paper loaded with about 1 mg of positive electrode material), and positive electrode shell.

[0070] The morphology of the sulfonated nanocellulose / polyvinylidene fluoride electrolyte film prepared in Example 1 was characterized, and the results are as follows: Figure 1 As shown, from Figure 1 It can be seen that the membrane surface is relatively flat and the texture is relatively uniform, with no obvious defects.

[0071] Infrared spectroscopy analysis was performed on the sulfonated nanocellulose / polyvinylidene fluoride electrolyte film prepared in Example 1, and the results are as follows: Figure 2 The display shows absorption peaks for S=O, SO, CF, and CF2, indicating that sulfonated nanocellulose and polyvinylidene fluoride were successfully composited.

[0072] The stress-strain curves of the materials were obtained by performing mechanical property tests using a constant-temperature double-column tensile testing machine on Examples 1, 2, and the comparative example. The results are as follows: Figure 3 As shown, at a constant tensile speed of 50 mm / min, the electrolyte film containing 1 g of polyvinylidene fluoride (Example 1) has better stress resistance than the electrolyte film containing 0.5 g of polyvinylidene fluoride (Example 2) and the comparative example, while the electrolyte film containing 0.5 g of polyvinylidene fluoride (Example 2) has better strain resistance.

[0073] The sulfonated nanocellulose / polyvinylidene fluoride electrolyte film prepared in Example 1 and the comparative example Zn / / Zn symmetric cell assembled with zinc plate (thickness of 80 µm) were subjected to cycle tests at different current densities.

[0074] The results are as follows Figure 4 As shown, at 0.2 mA cm -2 0.2 mA h cm -2Symmetric cells using sulfonated nanocellulose / polyvinylidene fluoride electrolyte films at current densities exhibit nearly 10 times the cycle life of comparative cells, and also achieve excellent performance under symmetric cell rate conditions.

[0075] The sulfonated nanocellulose / polyvinylidene fluoride electrolyte film prepared in Example 1 and the comparative example were respectively assembled with Zn / / (NH4)2V. 10 O 25 ·8H2O full cell, respectively at 1 A g -1 With 2 Ag -1 Cyclic testing was performed at current density. Results are as follows: Figure 5 As shown, at both current densities, the full-cell cycle life and capacity retention of the sulfonated nanocellulose / polyvinylidene fluoride electrolyte membrane are significantly higher than those of the comparative cell using a commercial glass fiber separator.

[0076] Among them (NH4)2V 10 O 25 The preparation process of the ·8H2O cathode material is as follows: 1.17 g of NH4VO3 (0.01 mol) and 1.891 g of H2C2O4·2H2O (0.015 mol) were dissolved in 70 ml of deionized water and stirred at 80 °C until a dark green color appeared (approximately 15 min). The mixture was then transferred to a 100 ml reactor and hydrothermally reacted at 140 °C for 12 h. The product was removed and centrifuged three times at 8000 rpm for 5 min each time. Finally, it was dried and ground in a vacuum oven at 80 °C to obtain (NH4)2V. 10 O 25 ·8H2O powder.

[0077] In summary, the sulfonated nanocellulose / polyvinylidene fluoride electrolyte film of this invention can effectively improve the performance, stability, and lifespan of aqueous zinc-ion batteries. It has high application prospects and commercial value.

[0078] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preparing a sulfonated nanocellulose / polyvinylidene fluoride electrolyte film, characterized in that, Includes the following steps: (1) Disperse sulfonated nanocellulose, conductive carbon black, polyvinylidene fluoride and zinc trifluoromethanesulfonate in water to obtain a mixed solution; (2) Heat the mixture, add an organic solvent, and mix evenly to obtain sulfonated nanocellulose / polyvinylidene fluoride electrolyte slurry; (3) Pour the sulfonated nanocellulose / polyvinylidene fluoride electrolyte slurry into the mold. After the liquid self-leveling surface is flat and in full contact with the mold, dry it to obtain the sulfonated nanocellulose / polyvinylidene fluoride electrolyte film.

2. The preparation method according to claim 1, characterized in that: In step (1), sulfonated nanocellulose is first dispersed in water to obtain an aqueous dispersion of sulfonated nanocellulose; then conductive carbon black, polyvinylidene fluoride and zinc trifluoromethanesulfonate are added to the aqueous dispersion of sulfonated nanocellulose.

3. The preparation method according to claim 1, characterized in that: In step (1), the mass fraction of the aqueous dispersion of sulfonated nanocellulose is 1~1.1%; the sulfonated nanocellulose sulfonic acid group content in the aqueous dispersion of sulfonated nanocellulose is 1.2~1.5 mmol / g; the mass ratio of the aqueous dispersion of sulfonated nanocellulose, polyvinylidene fluoride, conductive carbon black and organic solvent is (25~35):(0.5~1):(0.02~0.03):(10~10.5).

4. The preparation method according to claim 1, characterized in that: In step (1), the polyvinylidene fluoride has a molecular weight of 900,000 to 1,000,000 and a particle size of 20 to 30 µm.

5. The preparation method according to claim 1, characterized in that: In step (2), the heating temperature is 55~65℃ and the heating time is 4~5h; the organic solvent is N-methylpyrrolidone or dimethylformamide; the drying temperature is 55~65℃ and the drying time is 8~12h.

6. A sulfonated nanocellulose / polyvinylidene fluoride electrolyte film prepared by any one of the preparation methods 1 to 5 above.

7. The application of the sulfonated nanocellulose / polyvinylidene fluoride electrolyte film as described in claim 6 as a separator in the preparation of an aqueous zinc-ion battery.

8. The application according to claim 7, characterized in that, Its features are, No electrolyte solution is added to the aqueous zinc-ion battery.

9. The application according to claim 7, characterized in that, Before preparation, the sulfonated nanocellulose / polyvinylidene fluoride electrolyte membrane was immersed in a zinc trifluoromethanesulfonate solution.

10. The application according to claim 9, characterized in that, The concentration of the zinc trifluoromethanesulfonate solution is 1.5~3 mol / L, and the soaking time is 12~24 h.

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