A polymer electrolyte with ion-selective linear channel and its preparation method and application

Abstract

The present invention provides a polymer electrolyte with ion-selective linear channels and its preparation method and application, belonging to the field of sodium metal battery technology. Specifically, the following steps are: dissolving a fluorine-containing polymer and a sodium-containing cationic polymer monomer into a first organic solvent, stirring to obtain a mixed solution A, then adding a metal salt catalyst and an amine catalyst, stirring and reacting at 100-150°C for 18-24 hours, cooling and precipitating the grafted copolymer using a second organic solvent, dissolving and precipitating multiple times, and drying to obtain a polymer electrolyte with ion-selective linear channels. The -SO3Na structure in the polymer electrolyte obtained by the present invention can achieve a single Na + The transmission channel can effectively accelerate ion transport and reduce the ion concentration gradient in the electrolyte. At the same time, it can ensure that the electrolyte film with a thickness of only 10 to 16 μm still has high strength, thereby jointly inhibiting dendrite growth and improving battery stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of sodium metal batteries, and in particular relates to a polymer electrolyte with an ion-selective linear channel, a preparation method thereof, and an application thereof. Background Art

[0002] With the increasing global demand for efficient energy storage and green energy technologies, high-energy-density batteries have become a key goal of next-generation battery technology. Traditional liquid electrolytes have bottlenecks in safety, stability, and energy density, especially in high-power, high-voltage, and high-temperature environments.

[0003] Polymer electrolytes based on traditional polyvinylidene fluoride (PVDF) have attracted widespread attention due to their good electrochemical stability. However, the semi-crystalline state of PVDF results in low ionic conductivity of the polymer, and severe dehydrogenation (HF) reactions are prone to occur during electrochemical charge and discharge, which will corrode the interfacial lithium metal and solid electrolyte interface (SEI), thereby worsening the interfacial ion deposition environment. At the same time, the sodium salts of PVDF-based polymer electrolytes contain both anions and cations, resulting in a low electrolyte cation migration number. In addition, the high thickness of the electrolyte (>65μm) will also cause problems such as increased internal ion concentration gradients and uneven electric fields at the electrode / electrolyte interface, resulting in uneven deposition of interfacial ions, promoting the growth of sodium metal dendrites and internal short circuits in the battery.

[0004] The gel single-ion polymer quasi-solid electrolyte with ion-selective conduction properties uses a single ion conductor to avoid interference from multiple ions, which can effectively increase the cation migration number, reduce the ion concentration gradient inside the electrolyte, and improve the electric field uniformity of the electrolyte / electrode interface.

[0005] Chinese patent CN 111326788 A discloses a single-ion polymer electrolyte system, its preparation method, and its application. However, the electrolyte thickness is still relatively large (50-300 μm). Thick electrolytes extend the ion path and increase internal impedance. Furthermore, high thickness increases the proportion of inactive materials in the battery, reducing the battery's energy density.

[0006] Chinese patent CN 111100249 A discloses a single-ion polymer electrolyte, its preparation method, and a lithium-ion battery. While this method increases the electrolyte cation transference number to mitigate internal concentration gradients, the electrolyte strength is less than 22 MPa. This low-strength electrolyte is unable to withstand the high stress-strain changes experienced during long battery cycles and is easily pierced by dendrites, causing internal short circuits in the battery.

[0007] Therefore, the preparation of ion-selective electrolytes with high strength, low thickness and high cation migration number can promote the development of high-energy-density batteries towards higher energy density and greater safety. Summary of the Invention

[0008] In response to the problem that existing single-ion polymer electrolytes cannot achieve high strength, low thickness and high cation migration number, the present invention provides a polymer electrolyte with ion-selective linear channels, its preparation method and application, and by covalently grafting a fluorine-containing polymer segment skeleton with a polymer monomer containing metal cations, a polymer electrolyte with high strength, low thickness and high cation migration number is obtained, which helps to achieve higher energy density sodium metal batteries.

[0009] In order to achieve the above purpose, the technical methods adopted by the present invention are as follows:

[0010] A polymer electrolyte with an ion-selective linear channel, the chemical structure of which is:

[0011]

[0012] Wherein, m, n, and o are all positive integers, n>1, and m:n:o=100:(9~13):(10~15).

[0013] A method for preparing a polymer electrolyte having an ion-selective linear channel comprises the following steps:

[0014] Step 1, dissolving a fluorine-containing polymer and a sodium-containing cationic polymer monomer in a first organic solvent in a mass ratio of (1-3): (0.5-2), and stirring to obtain a mixed solution A; wherein the mass ratio of the polymer solute to the first organic solvent is (1-3): (10-20);

[0015] Step 2: adding a metal salt catalyst and an amine catalyst in a molar ratio of (350-410): (0.2-1) to the mixed solution A, and stirring to obtain a mixed solution B; wherein the mass ratio between the metal salt catalyst and the fluoropolymer is (110-125): (0.5-2);

[0016] Step 3: placing the mixed solution B in nitrogen or a rare gas, reacting at 100-150° C. for 18-24 hours, cooling to room temperature, and precipitating the grafted copolymer using a second organic solvent that is incompatible with the fluorine-containing polymer and the sodium-containing cationic polymer monomer;

[0017] Step 4: The obtained copolymer is dissolved and precipitated multiple times, the metal salt catalyst is removed, and then dried to obtain a polymer electrolyte with ion-selective linear channels.

[0018] Furthermore, the fluorine-containing polymer in step 1 is at least one of polyvinylidene fluoride (PVDF) and poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP).

[0019] Furthermore, the sodium-containing cationic polymer monomer in step 1 is at least one of sodium β-styrene sulfonate, sodium 4-styrene sulfonate, sodium vinyl sulfonate, sodium dodecylbenzene sulfonate, and sodium thiomethane sulfonate.

[0020] Furthermore, the metal salt catalyst in step 2 is a copper salt catalyst.

[0021] Furthermore, the copper salt catalyst includes a monovalent copper salt catalyst and a divalent copper salt catalyst, and the molar ratio of the two is (0.1-1): (3-7).

[0022] Furthermore, the monovalent copper salt catalyst is specifically at least one of cuprous chloride, cuprous bromide, and cuprous iodide, and the divalent copper salt catalyst is specifically at least one of cupric chloride, cupric bromide, and cupric fluoride.

[0023] Furthermore, the amine catalyst in step 2 is specifically at least one of pentamethyldiethylenetriamine, triethylamine, p-phenylenediamine, and ethylenediamine.

[0024] Furthermore, the specific process of washing the precipitate in step 4 is: first dissolving the obtained copolymer in the third organic solvent, and then precipitating it with the second organic solvent, and repeating it 3 to 5 times.

[0025] Furthermore, the first organic solvent and the third organic solvent are at least one of N-methylpyrrolidone, dimethyl sulfoxide, and tetrahydrofuran.

[0026] Furthermore, the second organic solvent is at least one of methanol, anhydrous ethanol, and n-hexane.

[0027] Furthermore, in step 4, the drying temperature is 60-80° C. and the drying time is 24-48 hours.

[0028] The present invention also proposes the application of the obtained polymer electrolyte with ion-selective linear channels in sodium metal batteries.

[0029] A sodium metal battery comprises a positive electrode, a gel polymer electrolyte and a sodium negative electrode, wherein the gel polymer electrolyte is prepared based on the polymer electrolyte having ion-selective linear channels.

[0030] Furthermore, the specific preparation process of the gel polymer electrolyte is as follows:

[0031] Step A, mixing the polymer electrolyte having ion-selective linear channels with a fourth organic solvent in a mass ratio of (1-3): (8-12), and dissolving in a water bath to form a viscous and transparent slurry;

[0032] Step B: evenly coating the slurry on a substrate, drying to obtain an electrolyte film, and soaking the film in a plasticizer for 12 to 24 hours to form a gel polymer electrolyte.

[0033] Furthermore, the temperature of the water bath dissolution is 60-80°C.

[0034] Furthermore, the thickness of the electrolyte film is 10 to 16 μm.

[0035] Furthermore, the plasticizer is three of ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, fluoroethylene carbonate, and propylene carbonate.

[0036] Furthermore, the fourth organic solvent is at least one of N-methylpyrrolidone, dimethyl sulfoxide, and tetrahydrofuran.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1. The present invention provides a polymer electrolyte with an ion-selective linear channel, its preparation method, and application. By controlling the ratio between the fluorine-containing polymer chain segment skeleton and the sodium-containing cationic polymer monomer, utilizing the synergistic effect of metal salt catalysts and amine catalysts, a covalent bond addition reaction is carried out on the fluorine-containing polymer and the sodium-containing cationic polymer monomer at high temperature to prepare a polymer electrolyte with an ion-selective linear channel.

[0039] 2. The -SO3Na structure in the polymer electrolyte obtained by the present invention can realize a single Na + The transmission channel of the anion grafting fixation structure eliminates the anion input into the structure, thereby increasing the Na + The migration number effectively accelerates ion transport, reduces the ion concentration gradient in the electrolyte, and thus inhibits dendrite growth;

[0040] 3. When the polymer electrolyte obtained by the present invention is used in a sodium metal battery, it must first be made into an electrolyte film and then soaked to form a gel polymer electrolyte. Compared with traditional single-ion polymer electrolytes, the polymer electrolyte obtained by the present invention can ensure that the electrolyte film is only 10 to 16 μm thick and still has high strength. In addition, the electrolyte film can effectively solve the problem of uneven interfacial ion deposition caused by factors such as large concentration polarization and uneven electric field at the electrode / electrolyte interface in traditional high-thickness polymer electrolytes, fundamentally inhibiting the growth of interfacial nanometal dendrites, thereby effectively preventing internal short circuits in the battery.

[0041] 4. Preferably, the structure of the polymer electrolyte based on the sodium styrene sulfonate structure contains a rigid non-rotating benzene ring structure (aromatic bond), which has high structural stability and a bond energy of up to 150 kJ / mol, which is much higher than ordinary carbon-carbon single bonds and double bonds, thereby effectively improving the structural stability of the polymer electrolyte based on the sodium styrene sulfonate structure at ultra-thin thickness. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0043] Figure 1 The polymer electrolyte with ion-selective linear channels obtained in Example 1 1 H spectrum;

[0044] Figure 2 TEM (transmission electron microscopy) image of the polymer electrolyte having ion-selective linear channels obtained in Example 1;

[0045] Figure 3 This is a cycle diagram of a Na||NVP battery assembled with the polymer electrolyte having ion-selective linear channels obtained in Example 1 and the polymer electrolyte obtained in Comparative Example 1;

[0046] Figure 4 The charge-discharge curves of the Na||Na symmetric battery assembled with the polymer electrolyte having ion-selective linear channels obtained in Example 1;

[0047] Figure 5 The Na||Na symmetric battery assembled with the polymer electrolyte having ion-selective linear channels obtained in Example 1 was 0.03-0.3 mA cm -2 Constant current test results at current density of ;

[0048] Figure 6 The constant current test results of the Na||NVP battery assembled with the polymer electrolyte having ion-selective linear channels obtained in Example 1 are in the voltage range of 2.8 to 4.8 V and at a current density of 0.4C rate. DETAILED DESCRIPTION

[0049] To further understand the present invention, preferred embodiments of the present invention are described below with reference to the following examples. However, it should be understood that these examples are intended only to further illustrate the features and advantages of the present invention and are not intended to limit the scope of the claims. All raw materials used in the present invention are not particularly limited in their sources and may be purchased commercially or prepared according to conventional methods known to those skilled in the art.

[0050] Example 1

[0051] This embodiment prepares a polymer electrolyte having an ion-selective linear channel, which specifically includes the following steps:

[0052] Step 1, poly (vinylidene fluoride-co-hexafluoropropylene) and sodium 4-styrene sulfonate are dissolved in dimethyl sulfoxide at a mass ratio of 1.73:1, and magnetically stirred to obtain a mixed solution A; wherein the mass ratio of the polymer to the dimethyl sulfoxide is 1:6.98;

[0053] Step 2: adding a monovalent cuprous bromide catalyst, a divalent cupric bromide catalyst, and pentamethyldiethylenetriamine in a molar ratio of 286:49:0.9 to the mixed solution A, and stirring to obtain a mixed solution B; wherein the mass ratio of the metal salt catalyst to the poly(vinylidene fluoride-co-hexafluoropropylene) polymer is 115.38:1;

[0054] Step 3: Place the mixed solution B in a three-necked flask filled with nitrogen atmosphere, react at 120° C. for 24 hours, cool to room temperature, and precipitate the grafted copolymer using methanol;

[0055] Step 4: The obtained copolymer is dissolved in dimethyl sulfoxide and then precipitated with methanol. After repeating the dissolution and precipitation four times, the monovalent copper salt catalyst and the divalent copper salt catalyst are removed. Finally, the mixture is placed in a vacuum oven at 60°C and dried for 24 hours to remove the solvent in the polymer, thereby obtaining a polymer electrolyte with an ion-selective linear channel.

[0056] The polymer electrolyte with ion-selective linear channels obtained in this example is characterized in the following phase.

[0057] The different coordination environments of the H element in the polymer structure, as well as the bond lengths and bond angles of different bonding situations, will show different position peaks in the H element spectrum of the nuclear magnetic resonance spectrometer (NMR), thereby proving the spatial structure of the grafted polymer. Therefore, the polymer electrolyte with ion-selective linear channels obtained in this example was dissolved in a polar solvent of deuterated dimethyl sulfoxide and placed in an NMR device for testing. 1 H spectrum, the results are as follows Figure 1As shown, there are three different H coordination environments (a, b, c). Specifically, 2.3 and 2.9 PPM in the H spectrum correspond to the H element at position a, and 6.5 and 7.5 PPM correspond to the H elements at positions b and c, respectively, which are consistent with the chemical structure of the polymer electrolyte with ion-selective linear channels obtained in this example.

[0058] The TEM test results of the polymer electrolyte with ion-selective linear channels obtained in this example are as follows: Figure 2 As shown, the obtained polymer electrolyte has a regular lattice structure with a lattice spacing of Since the -SO3Na structure in the obtained polymer electrolyte can realize single Na + The transmission channel of the anion grafting fixation structure eliminates the anion input into the structure, thereby increasing the Na + Migration number: In the lattice structure, linear transmission channels can effectively accelerate ion transport, thereby reducing the ion concentration gradient in the electrolyte and inhibiting dendrite growth.

[0059] The polymer electrolyte with ion-selective linear channels obtained in this embodiment was tested for strength using a universal testing machine. The results are as follows: Figure 3 As shown in FIG, since the obtained polymer electrolyte has a rigid segment polystyrene structure, its high bond energy makes its strength as high as 43.3 MPa.

[0060] In order to better illustrate the positive effects of the polymer electrolyte with ion-selective linear channels obtained in this embodiment, a Na||NVP battery and a Na||Na symmetric battery are assembled for illustration.

[0061] When assembling the Na||NVP battery, a 12mm diameter Na3V2(PO4)3(NVP) film is used as the positive electrode, a 14mm diameter sodium metal disc is used as the negative electrode, a 17mm diameter gel polymer electrolyte is used to separate the positive and negative electrodes, a steel sheet is used as the current collector, and a spring sheet is used as a gasket to assemble a 2032 button cell, namely the Na||NVP battery; after the battery is packaged, it is placed in a 60°C oven for 24 hours to allow the polymer electrolyte to fully contact and infiltrate the positive and negative electrode interfaces.

[0062] Specifically, the preparation process of the positive electrode sheet is as follows:

[0063] The positive electrode material NVP, the conductive additive C45, and the binder polyvinylidene fluoride were mixed in an N-methylpyrrolidone (NMP) solvent in a mass ratio of 8:1:1. The mixture was magnetically stirred at room temperature for 12 h to obtain a uniform positive electrode slurry with uniform components and a positive electrode material mass fraction of 11.1%. The slurry was then coated on a carbon-coated aluminum foil. The thickness was controlled by a scraper to 900 μm and the coating was uniformly applied on an automatic coating machine. The film was placed in an oven at 80°C and vacuum dried for 24 h. After the solvent evaporated, the NVP film was obtained and cut into 12 mm diameter discs as positive electrode sheets. The loading was controlled to be 2.2 mg cm -2 .

[0064] Specifically, the preparation process of the gel polymer electrolyte is as follows:

[0065] The polymer electrolyte with ion-selective linear channels obtained in this example was mixed with dimethyl sulfoxide (DMSO) at a mass ratio of 1:12 and dissolved in a 60°C water bath to form a viscous, transparent slurry. The slurry was evenly coated on a rigid substrate using an automatic coating machine, using a doctor blade to control the thickness to 400 μm. The slurry was then placed in a 60°C oven and vacuum-dried for 24 hours. After the solvent evaporated, the resulting electrolyte film was dried and cut into 11 μm-thick, 17 mm-diameter discs using a cutter. The discs were then immersed in a plasticizer for 24 hours to form a gel polymer electrolyte. The plasticizer consisted of ethylene carbonate: dimethyl carbonate: fluoroethylene carbonate in a volume ratio of 10:10:1.

[0066] The assembled Na||NVP battery was tested with a constant current density of 0.4C at a voltage range of 2.8 to 4.8 V. The results are as follows: Figure 4 As shown, it still has 100mAh g after 300 cycles. -1 discharge capacity.

[0067] The only difference between the process of assembling Na||Na symmetric battery and that of assembling Na||NVP battery is that sodium metal disc is used as positive electrode; other structures and assembly processes remain unchanged. The obtained Na||Na symmetric battery has a capacitance of 0.03~0.3mAcm -2 The constant current test was carried out at a current density of Figure 5 As shown, it is shown that the Na||Na symmetric battery based on the polymer electrolyte with ion-selective linear channels obtained in this embodiment can withstand a large test current density and has excellent cycle stability.

[0068] The conductivity of the gel polymer electrolyte obtained in this embodiment at 60°C is higher than 10 -5 S cm -1 , cation migration number>0.9.

[0069] Comparative Example 1

[0070] This comparative example prepares a dual-ion polymer electrolyte, which specifically includes the following steps:

[0071] Step 1, poly (vinylidene fluoride-co-hexafluoropropylene) and sodium bistrifluoromethanesulfonyl imide (i.e., sodium salt containing cationic and anionic dual ions) are dissolved in N-methylpyrrolidone at a mass ratio of 1.25:1, and magnetically stirred to obtain a mixed solution A; wherein the mass ratio of poly (vinylidene fluoride-co-hexafluoropropylene) to N-methylpyrrolidone is 1:10;

[0072] Step 2: Stir the mixed solution A to a uniform transparent solution, and then apply the slurry on a rigid substrate, evenly coating it on an automatic coating machine by controlling the thickness of the scraper to 800 μm;

[0073] Step 3: Place the coated film in an oven at 60°C and vacuum dry it for 24 hours. After the solvent evaporates, complete the drying to obtain a dual-ion polymer electrolyte; use a cutter to cut the dual-ion polymer electrolyte into 100 μm thick and 17 mm diameter discs, and soak them in a plasticizer composed of ethylene carbonate: dimethyl carbonate: fluoroethylene carbonate in a volume ratio of 10:10:1 to obtain a gel polymer electrolyte for battery installation.

[0074] The strength test of the dual ion polymer electrolyte obtained in this comparative example was carried out using a universal testing machine. The results are as follows: Figure 3 As shown, its strength is only 5.5 MPa, which is much lower than the 43.3 MPa strength of the polymer electrolyte (single cation) with ion-selective linear channels obtained in Example 1. The high strength characteristics of the polymer electrolyte can effectively improve the stability of the battery during long cycles.

[0075] The Na||NVP battery and the Na||Na symmetric battery were assembled according to the method of Example 1.

[0076] For Na||NVP batteries, constant current tests were performed at a current density of 0.4C at a voltage range of 2.8 to 4.8 V. The results are as follows: Figure 4 As shown in the figure, it can be seen that the battery performance has obviously decayed after 60 cycles.

[0077] Through the Na||Na symmetric battery test, the cation transference number of the gel polymer electrolyte obtained in this comparative example at a temperature of 60° C. is 0.31, which is much lower than that of the gel polymer electrolyte obtained in Example 1.

[0078] Example 2

[0079] In this example, a polymer electrolyte having an ion-selective linear channel was prepared. The process was different from that in Example 1 except that the ratio of poly(vinylidene fluoride-co-hexafluoropropylene) to sodium 4-styrenesulfonate in step 1 was adjusted to 1:1, and the mass ratio of the polymer to dimethyl sulfoxide was adjusted to 2:11; the other steps remained unchanged.

[0080] Compared with Example 1, this embodiment increases the proportion of rigid chain sodium styrene sulfonate in the polymer electrolyte. Its low rotation and high glass transition temperature characteristics reduce the chain segment mobility of the polymer electrolyte, thereby weakening its ion transport capacity. By assembling Na||NVP batteries, constant current tests were performed at a current density of 0.4C at a voltage range of 2.8 to 4.8V. The results are as follows: Figure 6 As shown, it can be seen that it only has 75mAh g -1 The discharge capacity of the battery is very good, but its cycle stability is still very good, and it can cycle for at least 400 cycles without attenuation.

[0081] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas, including the best mode, and also enables any technician in the field to practice the present invention, including making and using any device or system, and implementing any combined method. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The scope of patent protection of the present invention is defined by the claims and may include other embodiments that can be thought of by those skilled in the art. If these other embodiments have structural elements that are not different from the literal description of the claims, or if they include equivalent structural elements that are not substantially different from the literal description of the claims, then these other embodiments should also be included in the scope of the claims.

Claims

1. A sodium metal battery, characterized in that The invention comprises a positive electrode, a gel polymer electrolyte and a sodium negative electrode. The gel polymer electrolyte is prepared based on a polymer electrolyte having an ion-selective linear channel. The specific preparation process of the gel polymer electrolyte is as follows: Step 1, dissolving a fluorine-containing polymer and a sodium-containing cationic polymer monomer in a first organic solvent in a mass ratio of (1-3): (0.5-2), and stirring to obtain a mixed solution A; wherein the mass ratio of the polymer solute to the first organic solvent is (1-3): (10-20); the fluorine-containing polymer is poly(vinylidene fluoride-co-hexafluoropropylene); and the sodium-containing cationic polymer monomer is sodium 4-styrene sulfonate; Step 2: adding a metal salt catalyst and an amine catalyst in a molar ratio of (350-410): (0.2-1) to the mixed solution A, and stirring to obtain a mixed solution B; wherein the mass ratio between the metal salt catalyst and the fluoropolymer is (110-125): (0.5-2); Step 3: placing the mixed solution B in nitrogen or a rare gas, reacting at 100-150° C. for 18-24 hours, cooling to room temperature, and precipitating the grafted copolymer using a second organic solvent that is incompatible with the fluorine-containing polymer and the sodium-containing cationic polymer monomer; Step 4: The obtained copolymer is dissolved and precipitated multiple times, the metal salt catalyst is removed, and then dried to obtain a polymer electrolyte having an ion-selective linear channel, the chemical structure of which is: Wherein, m, n, and o are all positive integers, n>1, and m:n:o=100:(9-13):(10-15); Step 5: mixing the polymer electrolyte having ion-selective linear channels with a fourth organic solvent in a mass ratio of (1-3): (8-12), and dissolving in a water bath to form a viscous and transparent slurry; Step 6: evenly apply the slurry on the substrate, and after drying, obtain an electrolyte film, which is then immersed in a plasticizer for 12 to 24 hours to form a gel polymer electrolyte.

2. The sodium metal battery according to claim 1, characterized in that The metal salt catalyst in step 2 is a copper salt catalyst, including a monovalent copper salt catalyst and a divalent copper salt catalyst, and the molar ratio of the two is (0.1-1): (3-7).

3. The sodium metal battery according to claim 2, characterized in that The monovalent copper salt catalyst is specifically at least one of cuprous chloride, cuprous bromide, and cuprous iodide, and the divalent copper salt catalyst is specifically at least one of cupric chloride, cupric bromide, and cupric fluoride.

4. The sodium metal battery according to claim 1, characterized in that The amine catalyst in step 2 is specifically at least one of pentamethyldiethylenetriamine, triethylamine, p-phenylenediamine, and ethylenediamine.

5. The sodium metal battery according to claim 1, characterized in that: The specific process of washing the precipitate in step 4 is: first dissolving the obtained copolymer in a third organic solvent, then precipitating it using a second organic solvent, and repeating 3 to 5 times; the first organic solvent and the third organic solvent are at least one of N-methylpyrrolidone, dimethyl sulfoxide, and tetrahydrofuran; the second organic solvent is at least one of methanol, anhydrous ethanol, and n-hexane.

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