Polymer production method, thin film and method for producing the same, gel electrolyte, battery

Abstract

The application relates to a high polymer preparation method, which comprises the following steps: providing a mixed system containing hexachlorocyclotriphosphazene, a predetermined monomer and a natural high polymer, and copolymerizing the hexachlorocyclotriphosphazene, the predetermined monomer and the natural high polymer in the mixed system to obtain the high polymer, wherein the predetermined monomer is at least one of 1,2-bis(2-aminoethoxy)ethane and 4,4-diaminodiphenyl methane, and the structural unit of the natural high polymer contains at least two condensable groups, which are hydroxyl groups or carboxyl groups. The high polymer provided by the application has excellent flame retardant capacity, thermal stability and ion transmission capacity, and is suitable for the preparation of a gel electrolyte.

Description

Technical Field

[0001] This application relates to the field of new energy battery technology, and in particular to electrolyte-related materials. Background Technology

[0002] Lithium-ion batteries have become increasingly important energy storage devices, widely used in smartphones, electric vehicles, electric bicycles, and aerospace. A lithium-ion battery typically consists of three parts: electrodes, electrolyte, and separator. The electrolyte, as a crucial component, plays a vital role in ion transport between the electrodes, determining the battery's electrochemical and safety performance. Lithium-ion battery electrolytes are classified as liquid, solid, and gel-state. Currently, most commercially available lithium-ion battery electrolytes are organic liquid electrolytes, which can lead to leakage or short circuits during use, and may even cause the battery to catch fire or explode, posing serious safety hazards. At present, all-solid-state electrolytes, due to their low conductivity at room temperature, cannot yet meet the requirements for practical applications. In contrast, gel electrolytes reduce the amount of free solvent, lowering the risk of electrolyte leakage and the possibility of combustion and explosion, thus improving battery safety.

[0003] However, simply gelling the electrolyte has limited effect on improving the flame retardant performance of batteries. Many researchers and companies both domestically and internationally have conducted extensive research aimed at improving the flame retardant properties of gel electrolytes. Currently, improving the flame retardant performance of gel electrolytes is mainly achieved by adding flame retardant additives. The addition of these additives transforms the gel electrolyte from a flammable to a flame-retardant or even flame-retardant electrolyte, thereby enhancing its safety and stability, and reducing the risk of combustion or explosion during use. However, the addition of flame retardant additives also reduces the ionic conductivity of the gel electrolyte, thus affecting battery capacity and adversely impacting cycle life.

[0004] Furthermore, one of the mainstream preparation routes for gel electrolytes involves first preparing a porous membrane or a thin film that can absorb the electrolyte, and then adding the electrolyte during battery assembly to achieve the gelation process. In this composite gel with a thin film, a portion of the polymer forming the film may undergo thermal decomposition at higher operating temperatures, affecting battery safety. Summary of the Invention

[0005] This application provides a polymer preparation method, a thin film and its preparation method, a gel electrolyte, and a battery to solve the technical problems of the risk of thermal decomposition of gel electrolytes and the contradiction between ionic conductivity and flame retardancy.

[0006] In a first aspect, embodiments of this application provide a method for preparing a polymer, the method comprising:

[0007] A mixed system containing hexachlorocyclotriphosphazene, a predetermined monomer, and a natural polymer is provided, and the hexachlorocyclotriphosphazene, the predetermined monomer, and the natural polymer in the mixed system are copolymerized to obtain the polymer.

[0008] The predetermined monomer is at least one of 1,2-bis(2-aminoethoxy)ethane and 4,4-diaminodiphenylmethane, and the structural unit of the natural polymer contains at least two polycondensable groups, wherein the polycondensable groups are hydroxyl or carboxyl groups.

[0009] In some embodiments of this application, the mixed system further includes an acid-binding agent; and / or,

[0010] The mixture also includes a solvent.

[0011] In some embodiments of this application, the predetermined monomer is at least one selected from 1,2-bis(2-aminoethoxy)ethane and 4,4-diaminodiphenylmethane; and / or,

[0012] The natural polymer is at least one selected from cellulose, chitosan, sodium alginate, hyaluronic acid, chitosan, guar gum, β-cyclodextrin, and gum arabic, and the average relative molecular mass of the natural polymer is between 1,000 and 220,000; and / or,

[0013] The acid-binding agent is at least one selected from triethylamine, sodium acetate, sodium carbonate, and potassium carbonate; and / or...

[0014] The solvent is selected from at least one of anhydrous ethanol, anhydrous acetonitrile, dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, and dichloromethane; and / or,

[0015] The molar ratio of the hexachlorocyclotriphosphazene, the predetermined monomer, the natural polymer, and the acid-binding agent is 1–50:3–150:3–300:3–30; and / or,

[0016] The copolymerization temperature is 50–100°C; and / or,

[0017] The copolymerization time is 6 to 24 hours.

[0018] Secondly, embodiments of this application provide a thin film, the thin film comprising:

[0019] 50–100 parts by weight of the main polymer;

[0020] 5 to 20 parts by weight of plasticizer;

[0021] 1 to 10 parts by mass of a polymer, wherein the polymer is the polymer described in the first aspect.

[0022] It is easy to understand that the film described in this application has similar functions to lithium battery separators, and the main polymer described in this application refers to the main polymer of lithium battery separators in this field.

[0023] In some embodiments of this application, the main polymer is at least one selected from polypropylene carbonate, polyvinylidene carbonate, polyvinylidene fluoride, polyvinylidene fluoride-hexachloropropylene, polyethylene oxide, polyacrylonitrile, and polyfluoropropylene carbonate; and / or,

[0024] The plasticizer is at least one of dibutyl phthalate, diethyl carbonate, succinic anhydride, polyethylene oxide, polyethylene glycol, ethylene carbonate, and propylene carbonate.

[0025] Thirdly, embodiments of this application provide a method for preparing a thin film, wherein the thin film is the thin film described in any embodiment of the second aspect, and the method for preparing the thin film includes the following steps:

[0026] The host polymer is provided, and the host polymer is prepared into a polymer slurry;

[0027] The plasticizer is added to the polymer slurry, and the reaction is carried out at a first temperature to crosslink the main polymer, thereby obtaining a crosslinked polymer slurry;

[0028] The polymer is added to the crosslinked polymer slurry and reacted at a second temperature to obtain a pre-prepared slurry;

[0029] The pre-made slurry is added to a mold and the solvent is removed to obtain the film.

[0030] In some embodiments of this application, the solvent for the polymer slurry is at least one selected from deionized water, ethanol, ethylene glycol, propylene glycol, isopropanol, acetone, N-methylpyrrolidone, and N,N-dimethylformamide; and / or,

[0031] The first temperature is 50–80°C; and / or,

[0032] The second temperature is 50–80°C.

[0033] Fourthly, embodiments of this application provide a gel electrolyte, the gel electrolyte comprising the thin film described in the second aspect, or the thin film prepared by the method described in the third aspect; the gel electrolyte further comprises an electrolyte comprising lithium salt, sodium salt and organic solvent.

[0034] In some embodiments of this application, the lithium salt is selected from at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalate borate, lithium dioxalate borate, and lithium bis(fluorosulfonyl)imide; and / or,

[0035] The sodium salt is selected from one or more of sodium perchlorate, sodium hexafluorophosphate, sodium bis(trifluoromethanesulfonyl)imide, sodium chloride, sodium iodide, and their analogues and derivatives, more preferably at least one of sodium perchlorate, sodium hexafluorophosphate, and sodium bis(trifluoromethanesulfonyl)imide; and / or,

[0036] The organic solvent is selected from at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, 1,3-oxocyclopentane, and dimethyl ether; and / or,

[0037] The total concentration of alkali metal ions in the lithium and sodium salts is 0.1 mol / L to 5 mol / L.

[0038] Fifthly, embodiments of this application provide a battery, which is a lithium-ion battery or a sodium-ion battery, and the battery includes the gel electrolyte described in the fourth aspect.

[0039] The technical solutions provided in this application have the following advantages compared with the prior art:

[0040] The polymer preparation method provided in this application involves modifying a natural polymer using hexachlorocyclotriphosphazene and a predetermined monomer. The natural polymer itself possesses excellent ion transport capabilities, and using it as the framework ensures good ionic conductivity. The phosphorus-chlorine bond in hexachlorocyclotriphosphazene exhibits high reactivity, easily introducing phosphazene groups through chlorine atom substitution, thereby increasing the flame retardancy of the natural polymer. Furthermore, the six-membered ring structure of hexachlorocyclotriphosphazene exhibits strong structural stability, withstands high temperatures, and increases the thermal stability of the polymer. The predetermined monomer is selected from at least one of 1,2-bis(2-aminoethoxy)ethane and 4,4-diaminodiphenylmethane, both ends of which are amino groups. These monomers can react simultaneously with the chlorine atoms on hexachlorocyclotriphosphazene and the abundant hydroxyl groups in the natural polymer. The suitable chain length reduces steric hindrance between reactant molecules, improves reaction conversion rate, and increases the distribution density of phosphazene groups in the polymer, thus enhancing its flame retardancy. In summary, the polymer provided in this application has excellent flame retardancy, thermal stability, and ion transport capabilities, making it suitable for the preparation of gel electrolytes. Attached Figure Description

[0041] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0042] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 A comparison diagram of vertical combustion tests of the gel electrolyte provided in Example 1 of this application and the commercial diaphragm provided in the comparative example;

[0044] Figure 2 A comparison diagram of heat shrinkage tests between the gel electrolyte provided in Example 1 of this application and the commercial diaphragm provided in the comparative example;

[0045] Figure 3 Thermogravimetric analysis (TGA) diagrams of the gel electrolyte provided in Example 1 of this application and the commercial diaphragm provided in the comparative example;

[0046] Figure 4 DSC thermograms of the gel electrolyte provided in Example 1 of this application and the commercial membrane provided in the comparative example;

[0047] Figure 5 The graph shows the lithium-ion conductivity of a coin cell prepared using the gel electrolyte provided in Example 1 of this application.

[0048] Figure 6 This is a cycle capacity curve of a full battery prepared using the gel electrolyte provided in Example 1 of this application. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0050] Unless otherwise specified, the terminology used herein should be understood as having the meaning as commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. In case of any conflict, this specification shall prevail.

[0051] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0052] To enhance flame retardancy, existing gel electrolytes often incorporate flame-retardant additives. However, the addition of these additives reduces the ionic conductivity of the gel electrolyte. Furthermore, some gel electrolytes include a membrane that absorbs the electrolyte, and some components of this membrane may undergo thermal decomposition at higher operating temperatures.

[0053] The technical solution provided in this application is to solve the above-mentioned technical problems, and the general idea is as follows:

[0054] In a first aspect, embodiments of this application provide a method for preparing a polymer, the method comprising:

[0055] A mixed system containing hexachlorocyclotriphosphazene, a predetermined monomer, and a natural polymer is provided, and the hexachlorocyclotriphosphazene, the predetermined monomer, and the natural polymer in the mixed system are copolymerized to obtain the polymer.

[0056] The predetermined monomer is at least one of 1,2-bis(2-aminoethoxy)ethane and 4,4-diaminodiphenylmethane, and the structural unit of the natural polymer contains at least two polycondensable groups, wherein the polycondensable groups are hydroxyl or carboxyl groups.

[0057] It is easy to understand that during the copolymerization process of hexachlorocyclotriphosphazene with predetermined monomers and natural polymers, it will form the structural unit of the polymer in the form of phosphazene groups.

[0058] The advantage of using hexachlorocyclotriphosphazene to introduce phosphazene groups is that the phosphorus-chlorine bond in hexachlorocyclotriphosphazene is very reactive, allowing chlorine to be easily substituted, resulting in a series of flame-retardant phosphazene derivatives. Furthermore, the structural stability of the six-membered ring in hexachlorocyclotriphosphazene gives it acid and alkali resistance, as well as high-temperature resistance.

[0059] The advantage of selecting at least one of 1,2-bis(2-aminoethoxy)ethane and 4,4-diaminodiphenylmethane as the predetermined monomer is that both 1,2-bis(2-aminoethoxy)ethane and 4,4-diaminodiphenylmethane have amino groups at both ends of their molecular structures, allowing them to react simultaneously with the chlorine atoms on hexachlorocyclotriphosphazene and the abundant hydroxyl groups found in natural polymers. Furthermore, the long-chain structure of the predetermined monomer reduces steric hindrance between the reactants, thus improving the reaction conversion rate.

[0060] Natural polymers generally have good ion permeability, and polymers prepared using natural polymers as the main framework are more likely to maintain good ion permeability.

[0061] This application modifies a natural polymer using hexachlorocyclotriphosphazene and the predetermined monomer. The natural polymer itself has good ion transport capabilities, and using the natural polymer as the framework ensures good ionic conductivity. The phosphorus-chlorine bond in hexachlorocyclotriphosphazene exhibits excellent reactivity, easily introducing phosphazene groups through chlorine atom substitution, thereby increasing the flame retardancy of the natural polymer. Furthermore, the six-membered ring structure of hexachlorocyclotriphosphazene is structurally stable and can withstand high temperatures, increasing the thermal stability of the polymer. The predetermined monomer is selected from at least one of 1,2-bis(2-aminoethoxy)ethane and 4,4-diaminodiphenylmethane, both ends of which are amino groups. These monomers can react simultaneously with the chlorine atoms on hexachlorocyclotriphosphazene and the abundant hydroxyl groups in the natural polymer. The suitable chain length reduces steric hindrance between reactant molecules, improves reaction conversion rate, and increases the distribution density of phosphazene groups in the polymer, thus increasing the flame retardancy of the polymer. In summary, the polymer provided in this application has excellent flame retardancy, thermal stability, and ion transport capabilities, making it suitable for the preparation of gel electrolytes.

[0062] In some embodiments of this application, the mixed system further includes an acid-binding agent; and / or,

[0063] The mixture also includes a solvent.

[0064] As is easily understood, acid-binding agents are commonly used reaction auxiliaries in the field of polymer synthesis, used to adjust the pH when acids are generated in the reaction, preventing the reaction system from becoming too acidic. The reason for adding an acid-binding agent in this application is that the condensation reaction between monomers containing diamine groups and monomers containing phosphazene groups produces hydrochloric acid. Adding an acid-binding agent can consume the hydrochloric acid, promote the rightward shift of the chemical equilibrium, and improve the conversion rate.

[0065] In some embodiments of this application, the predetermined monomer is at least one selected from 1,2-bis(2-aminoethoxy)ethane and 4,4-diaminodiphenylmethane; and / or,

[0066] The natural polymer is at least one selected from cellulose, chitosan, sodium alginate, hyaluronic acid, chitosan, guar gum, β-cyclodextrin, and gum arabic; and / or,

[0067] The acid-binding agent is at least one selected from triethylamine, sodium acetate, sodium carbonate, and potassium carbonate; and / or...

[0068] The solvent is selected from at least one of anhydrous ethanol, anhydrous acetonitrile, dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, and dichloromethane; and / or,

[0069] The molar ratio of the hexachlorocyclotriphosphazene, the predetermined monomer, the natural polymer, and the acid-binding agent is 1–50:3–150:3–300:3–30, and the average relative molecular mass of the natural polymer is between 1,000 and 220,000; and / or,

[0070] The copolymerization temperature is 50–100°C; and / or,

[0071] The copolymerization time is 6 to 24 hours.

[0072] The beneficial effect of selecting at least one of the following natural polymers—cellulose, chitin, sodium alginate, hyaluronic acid, chitosan, guar gum, β-cyclodextrin, and gum arabic—is that after the above monomers copolymerize to form structural units in the polymer, they can provide good ion permeability and have a certain mechanical strength.

[0073] As an example, one of the following molecular weight polymers can be selected: cellulose with a molecular weight of 100,000, chitin with a molecular weight of 50,000, sodium alginate with a molecular weight of 100,000, hyaluronic acid with a molecular weight of 200,000, chitosan with a molecular weight of 150,000, gum arabic with a molecular weight of 220,000, guar gum with a molecular weight of 200,000, and β-cyclodextrin with a molecular weight of 1,134.

[0074] The advantage of limiting the copolymerization temperature to 50–100°C is that, on the one hand, the copolymerization can proceed smoothly at a relatively fast rate, and on the other hand, the resulting polymer morphology and molecular weight will not be insufficiently uniform due to an excessively fast reaction rate.

[0075] Secondly, embodiments of this application provide a thin film, the thin film comprising:

[0076] 50–100 parts by weight of the main polymer;

[0077] 5 to 20 parts by weight of plasticizer;

[0078] 1 to 10 parts by mass of a polymer, wherein the polymer is the polymer described in the first aspect.

[0079] It is easy to understand that the film described in this application has similar functions to lithium battery separators, and the main polymer described in this application refers to the main polymer of lithium battery separators in this field.

[0080] In some embodiments of this application, the main polymer is at least one selected from polypropylene carbonate, polyvinylidene carbonate, polyvinylidene fluoride, polyvinylidene fluoride-hexachloropropylene, polyethylene oxide, polyacrylonitrile, and polyfluoropropylene carbonate; and / or,

[0081] The plasticizer is at least one of dibutyl phthalate, diethyl carbonate, succinic anhydride, polyethylene oxide, polyethylene glycol, ethylene carbonate, and propylene carbonate.

[0082] Thirdly, embodiments of this application provide a method for preparing a thin film, wherein the thin film is the thin film described in any embodiment of the second aspect, and the method for preparing the thin film includes the following steps:

[0083] S1: Provide the main polymer and prepare the main polymer into a polymer slurry;

[0084] S2: Add the plasticizer to the polymer slurry and react at a first temperature to crosslink the main polymer, thereby obtaining a crosslinked polymer slurry;

[0085] S3: Add the polymer to the crosslinked polymer slurry and react at a second temperature to obtain a pre-made slurry;

[0086] S4: After adding the pre-made slurry to the mold, the solvent is removed to obtain the film.

[0087] It is easy to understand that the main polymer can be prepared into a polymer slurry by dispersing the main polymer in a solvent.

[0088] Solvent removal can be achieved by conventional technical means, such as drying, natural air drying, vacuum drying, and freeze drying.

[0089] In some embodiments of this application, the solvent for the polymer slurry is at least one selected from deionized water, ethanol, ethylene glycol, propylene glycol, isopropanol, acetone, N-methylpyrrolidone, and N,N-dimethylformamide; and / or,

[0090] The first temperature is 50–80°C; and / or,

[0091] The second temperature is 50–80°C.

[0092] Fourthly, embodiments of this application provide a gel electrolyte, the gel electrolyte comprising the thin film described in the second aspect, or the thin film prepared by the method described in the third aspect; the gel electrolyte further comprises an electrolyte comprising lithium salt, sodium salt and organic solvent.

[0093] Those skilled in the art, having obtained the thin film described in the second aspect or the thin film prepared by the method described in the third aspect, can prepare gel electrolytes based on common knowledge in the art.

[0094] The gel electrolyte is implemented based on the embodiments of the second or third aspect. The specific implementation of the gel electrolyte can be referred to the embodiments of the first or second aspect and common knowledge in the art. Since the gel electrolyte adopts all the technical solutions of any one of the embodiments of the first or second aspect, it can have all the beneficial effects brought by the technical solutions of the first or second aspect, which will not be elaborated here.

[0095] In some embodiments of this application, the lithium salt is selected from at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalate borate, lithium dioxalate borate, and lithium bis(fluorosulfonyl)imide; and / or,

[0096] The sodium salt is selected from one or more of sodium perchlorate, sodium hexafluorophosphate, sodium bis(trifluoromethanesulfonyl)imide, sodium chloride, sodium iodide, and their analogues and derivatives, more preferably at least one of sodium perchlorate, sodium hexafluorophosphate, and sodium bis(trifluoromethanesulfonyl)imide; and / or,

[0097] The organic solvent is selected from at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, 1,3-oxocyclopentane, and dimethyl ether; and / or,

[0098] The total concentration of alkali metal ions in the lithium and sodium salts is 0.1 mol / L to 5 mol / L.

[0099] Fifthly, embodiments of this application provide a battery, which is a lithium-ion battery or a sodium-ion battery, and the battery includes the gel electrolyte described in the fourth aspect.

[0100] The battery is implemented based on the embodiments of the fourth aspect. The specific implementation of the battery can be referred to the embodiments of the fourth aspect and common knowledge in the art. Since the battery adopts all the technical solutions of any embodiment of the fourth aspect, it can have all the beneficial effects brought by the technical solutions of the fourth aspect, which will not be described in detail here.

[0101] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards. If there is no corresponding national standard, then general international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0102] Example 1

[0103] This embodiment provides a gel electrolyte, which is prepared by the following steps:

[0104] (I) Synthesis of Polymers

[0105] Cellulose nanofibers (CNFs) were selected as the natural polymer, and 10 mL of the sample contained 0.01 g of solids. -1 A CNFs solution was prepared by adding 0.15 g of 1,2-bis(2-aminoethoxy)ethane and 1 mL of triethylamine (TEA) to a 50 mL beaker to obtain a mixed solution. 0.38 g of hexachlorocyclotriphosphazene (HCCP) was dissolved in 10 mL of anhydrous acetonitrile, and the solution was heated and stirred at 50 °C for 1 h until completely dissolved. The HCCP solution was slowly added dropwise to a serum bottle containing the mixed solution, and the mixture was heated and stirred at 60 °C for 8 h to complete the polycondensation reaction. The resulting solution was filtered, washed with ethanol, centrifuged, and repeated three times. After drying, a flame-retardant modified natural polymer powder was obtained, which is the polymer described in this application.

[0106] (II) Thin Film Preparation

[0107] Dissolve 1.00 g of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) in 13.50 mL of anhydrous acetone. Stir at 500 rpm for 1 h in a constant-temperature magnetic stirrer at 60 °C to obtain a colorless, transparent, and clear polymer slurry. Add 0.05 g of PEO to the slurry and heat and stir at 60 °C for 2 h to obtain a homogeneous and stable crosslinked polymer slurry. Then add 1 mL of the polymer dispersion prepared in step (I), with a solid content of 0.01 g / mL. -1 After adding the solvent, heat and stir at 60°C for 12 hours to obtain a flame-retardant gel electrolyte slurry. Coat the electrolyte slurry onto a polytetrafluoroethylene (PTFE) plate with a spatula, let it stand at room temperature for 10 minutes, and then place it in a vacuum oven at 60°C to dry the solvent. Take 4 mL of the polymer slurry and cast it uniformly into a 10 mm × 10 mm PTFE mold. Dry it under vacuum at 60°C for 12 hours to remove the solvent, obtaining a flame-retardant gel electrolyte dry film, which is the film described in this application.

[0108] (III) Preparation of Gel Electrolytes

[0109] The film prepared in step (II) is immersed in 1 mol L -1 After immersing in the liquid electrolyte for 30 minutes, the film is removed to obtain the gel electrolyte described in this application. The lithium salt of the electrolyte is LiPF6 (lithium hexafluorophosphate), and the solvent is EC (ethylene carbonate) / DEC (diethyl carbonate) / DMC (dimethyl carbonate) in a volume ratio of 1:1:1.

[0110] Example 2

[0111] This embodiment provides a gel electrolyte, which is prepared by the following steps:

[0112] (I) Synthesis of Polymers

[0113] Chitosan was selected as a natural polymer, and 10 mL of the sample contained 0.01 g of solids. -1 A chitin dispersion was prepared by adding 0.19 g of 1,2-bis(2-aminoethoxy)ethane, 4,4-diaminodiphenylmethane, and 1 mL of 30% potassium carbonate solution to a 50 mL beaker to obtain a mixed solution. 0.38 g of hexachlorocyclotriphosphazene (HCCP) was dissolved in 10 mL of anhydrous acetonitrile, and the solution was heated and stirred at 50 °C for 1 h until completely dissolved. The HCCP solution was slowly added dropwise to a serum bottle containing the mixed solution, and the mixture was heated and stirred at 60 °C for 8 h to complete the polycondensation reaction. The resulting solution was filtered, washed with ethanol, centrifuged, and repeated three times. After drying, a flame-retardant modified natural polymer powder was obtained, which is the polymer described in this application.

[0114] (II) Thin Film Preparation

[0115] Dissolve 1.00 g of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) in 13.50 mL of anhydrous acetone. Stir at 500 rpm for 1 h in a constant-temperature magnetic stirrer at 60 °C to obtain a colorless, transparent, and clear polymer slurry. Add 0.05 g of PEO to the slurry and heat and stir at 60 °C for 2 h to obtain a homogeneous and stable crosslinked polymer slurry. Then add 1 mL of the polymer dispersion prepared in step (I), with a solid content of 0.01 g / mL. -1 After adding the solvent, heat and stir at 60°C for 12 hours to obtain a flame-retardant gel electrolyte slurry. Coat the electrolyte slurry onto a polytetrafluoroethylene (PTFE) plate with a spatula, let it stand at room temperature for 10 minutes, and then place it in a vacuum oven at 60°C to dry the solvent. Take 4 mL of the polymer slurry and cast it uniformly into a 10 mm × 10 mm PTFE mold. Dry it under vacuum at 60°C for 12 hours to remove the solvent, obtaining a flame-retardant gel electrolyte dry film, which is the film described in this application.

[0116] (III) Preparation of Gel Electrolytes

[0117] The film prepared in step (II) is immersed in 1 mol L -1 After immersing in the liquid electrolyte for 30 minutes, the film is removed to obtain the gel electrolyte described in this application. The lithium salt of the electrolyte is LiPF6 (lithium hexafluorophosphate), and the solvent is EC (ethylene carbonate) / DEC (diethyl carbonate) / DMC (dimethyl carbonate) in a volume ratio of 1:1:1.

[0118] Example 3

[0119] This embodiment provides a gel electrolyte, which is prepared by the following steps:

[0120] (I) Synthesis of Polymers

[0121] Sodium alginate was selected as a natural polymer, and 10 mL of the solution was prepared with a concentration of 0.01 g / mL. -1 A sodium alginate solution was prepared by adding 0.15 g of 1,2-bis(2-aminoethoxy)ethane and 1 mL of triethylamine (TEA) to a 50 mL beaker to obtain a mixed solution. 0.38 g of hexachlorocyclotriphosphazene (HCCP) was dissolved in 10 mL of anhydrous acetonitrile, and the solution was heated and stirred at 50 °C for 1 h until completely dissolved. The HCCP solution was slowly added dropwise to a serum bottle containing the mixed solution, and the mixture was heated and stirred at 60 °C for 8 h to complete the polycondensation reaction. The resulting solution was filtered, washed with ethanol, centrifuged, and repeated three times. After drying, a flame-retardant modified natural polymer powder was obtained, which is the polymer described in this application.

[0122] (II) Thin Film Preparation

[0123] Dissolve 1.00 g of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) in 13.50 mL of anhydrous acetone. Stir at 500 rpm for 1 h in a constant-temperature magnetic stirrer at 60 °C to obtain a colorless, transparent, and clear polymer slurry. Add 0.05 g of PEO to the slurry and heat and stir at 60 °C for 2 h to obtain a homogeneous and stable crosslinked polymer slurry. Then add 1 mL of the polymer dispersion prepared in step (I), with a solid content of 0.01 g / mL. -1 After adding the solvent, heat and stir at 60°C for 12 hours to obtain a flame-retardant gel electrolyte slurry. Coat the electrolyte slurry onto a polytetrafluoroethylene (PTFE) plate with a spatula, let it stand at room temperature for 10 minutes, and then place it in a vacuum oven at 60°C to dry the solvent. Take 4 mL of the polymer slurry and cast it uniformly into a 10 mm × 10 mm PTFE mold. Dry it under vacuum at 60°C for 12 hours to remove the solvent, obtaining a flame-retardant gel electrolyte dry film, which is the film described in this application.

[0124] (III) Preparation of Gel Electrolytes

[0125] The film prepared in step (II) is immersed in 1 mol L -1 After immersing in the liquid electrolyte for 30 minutes, the film is removed to obtain the gel electrolyte described in this application. The lithium salt of the electrolyte is LiPF6 (lithium hexafluorophosphate), and the solvent is EC (ethylene carbonate) / DEC (diethyl carbonate) / DMC (dimethyl carbonate) in a volume ratio of 1:1:1.

[0126] Example 4

[0127] This embodiment provides a gel electrolyte, which is prepared by the following steps:

[0128] (I) Synthesis of Polymers

[0129] Hyaluronic acid, a natural polymer, was selected, and 10 mL was taken with a concentration of 0.01 g / mL. -1 A hyaluronic acid solution was prepared by adding 0.15 g of 1,2-bis(2-aminoethoxy)ethane and 1 mL of triethylamine (TEA) to a 50 mL beaker to obtain a mixed solution. 0.38 g of hexachlorocyclotriphosphazene (HCCP) was dissolved in 10 mL of anhydrous acetonitrile, and the solution was heated and stirred at 50 °C for 1 h until completely dissolved. The HCCP solution was slowly added dropwise to a serum bottle containing the mixed solution, and the mixture was heated and stirred at 60 °C for 8 h to complete the polycondensation reaction. The resulting solution was filtered, washed with ethanol, centrifuged, and repeated three times. After drying, a flame-retardant modified natural polymer powder was obtained, which is the polymer described in this application.

[0130] (II) Thin Film Preparation

[0131] Dissolve 1.00 g of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) in 13.50 mL of anhydrous acetone. Stir at 500 rpm for 1 h in a constant-temperature magnetic stirrer at 60 °C to obtain a colorless, transparent, and clear polymer slurry. Add 0.05 g of PEO to the slurry and heat and stir at 60 °C for 2 h to obtain a homogeneous and stable crosslinked polymer slurry. Then add 1 mL of the polymer dispersion prepared in step (I), with a solid content of 0.01 g / mL. -1 After adding the solvent, heat and stir at 60°C for 12 hours to obtain a flame-retardant gel electrolyte slurry. Coat the electrolyte slurry onto a polytetrafluoroethylene (PTFE) plate with a spatula, let it stand at room temperature for 10 minutes, and then place it in a vacuum oven at 60°C to dry the solvent. Take 4 mL of the polymer slurry and cast it uniformly into a 10 mm × 10 mm PTFE mold. Dry it under vacuum at 60°C for 12 hours to remove the solvent, obtaining a flame-retardant gel electrolyte dry film, which is the film described in this application.

[0132] (III) Preparation of Gel Electrolytes

[0133] The film prepared in step (II) is immersed in 1 mol L -1 After immersing in the liquid electrolyte for 30 minutes, the film is removed to obtain the gel electrolyte described in this application. The lithium salt of the electrolyte is LiPF6 (lithium hexafluorophosphate), and the solvent is EC (ethylene carbonate) / DEC (diethyl carbonate) / DMC (dimethyl carbonate) in a volume ratio of 1:1:1.

[0134] Example 5

[0135] This embodiment provides a gel electrolyte, which is prepared by the following steps:

[0136] (I) Synthesis of Polymers

[0137] Chitosan was selected as the natural polymer. 10 mL of a CNFs solution with a solid content of 0.01 g mL⁻¹ was added to a 50 mL beaker, along with 0.15 g of 1,2-bis(2-aminoethoxy)ethane and 1 mL of triethylamine (TEA) to obtain a mixed solution. 0.38 g of hexachlorocyclotriphosphazene (HCCP) was dissolved in 10 mL of anhydrous acetonitrile, and the solution was heated and stirred at 50 °C for 1 h until completely dissolved. The HCCP solution was slowly added dropwise to a serum bottle containing the mixed solution, and the mixture was heated and stirred at 60 °C for 8 h to complete the polycondensation reaction. The resulting solution was filtered, washed with ethanol, centrifuged, and repeated three times. After drying, a flame-retardant modified natural polymer powder was obtained, which is the polymer described in this application.

[0138] (II) Thin Film Preparation

[0139] Dissolve 1.00 g of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) in 13.50 mL of anhydrous acetone. Stir at 500 rpm for 1 h in a constant-temperature magnetic stirrer at 60 °C to obtain a colorless, transparent, and clear polymer slurry. Add 0.05 g of PEO to the slurry and heat and stir at 60 °C for 2 h to obtain a homogeneous and stable crosslinked polymer slurry. Then add 1 mL of the polymer dispersion prepared in step (I), with a solid content of 0.01 g / mL. -1 After adding the solvent, heat and stir at 60°C for 12 hours to obtain a flame-retardant gel electrolyte slurry. Coat the electrolyte slurry onto a polytetrafluoroethylene (PTFE) plate with a spatula, let it stand at room temperature for 10 minutes, and then place it in a vacuum oven at 60°C to dry the solvent. Take 4 mL of the polymer slurry and cast it uniformly into a 10 mm × 10 mm PTFE mold. Dry it under vacuum at 60°C for 12 hours to remove the solvent, obtaining a flame-retardant gel electrolyte dry film, which is the film described in this application.

[0140] (III) Preparation of Gel Electrolytes

[0141] The film prepared in step (II) is immersed in 1 mol L -1 After immersing in the liquid electrolyte for 30 minutes, the film is removed to obtain the gel electrolyte described in this application. The lithium salt of the electrolyte is LiPF6 (lithium hexafluorophosphate), and the solvent is EC (ethylene carbonate) / DEC (diethyl carbonate) / DMC (dimethyl carbonate) in a volume ratio of 1:1:1.

[0142] Relevant experimental and effect data:

[0143] The flame retardant properties of the gel electrolyte prepared in Example 1 were evaluated through a vertical burning test. The test results are as follows: Figure 1 , Figure 1 This indicates that its flame retardancy reaches UL-94V0 level.

[0144] It should be noted that the UL-94V0 definition is: after two 10-second burning tests on the sample, the flame extinguishes within 30 seconds. No burning material should fall. The combustion phenomenon of this gel polymer is as follows: when the ignition source is brought close to the flame-retardant modified gel electrolyte, it is not ignited. In the first 10-second ignition and combustion, only melting and shrinkage occur, without producing droplets. In the second ignition, it rapidly turns black into char during a 10-second combustion and exhibits a blow-out effect, burning only in the area of ​​flame contact without diffusion, and self-extinguishing upon removal of the flame. In the third ignition, the gel polymer electrolyte is completely unable to burn; the charred area only turns red. These phenomena are sufficient to demonstrate that it meets the UL-94V0 flame-retardant rating.

[0145] Four portions each of the gel electrolyte and commercially available diaphragm prepared in Example 1 were provided and placed in a constant temperature heating chamber. The mixtures were then allowed to stand for 1 hour at 80, 100, 120, and 140°C, respectively. The shrinkage of both materials was then observed and recorded. Figure 2 .Depend on Figure 2 It can be observed that the commercial diaphragm has a thermal shrinkage rate of >50% at 140°C, while the flame-retardant gel electrolyte membrane has a thermal shrinkage rate of <5% at 140°C. Therefore, the thermal shrinkage performance of the gel electrolyte prepared in Example 1 is far superior to that of the commercial diaphragm.

[0146] It should be noted that the product information for the commercial diaphragm provided is as follows:

[0147] Manufacturer: Suzhou Duoduo Chemical Technology Co., Ltd.

[0148] Diaphragm product model: Celgrad2500.

[0149] Thermogravimetric analysis (TG) was performed on the gel electrolyte prepared in Example 1 and the commercially available separator, and the TG results are shown in the figure. Figure 3 As shown, the gel electrolyte exhibits thermogravimetric plateaus at 398℃, 447℃, and 468℃, corresponding to the CNFs, PEO, and PVDF-HFP components, respectively. The first two components are only used as modifying additives, while the final PVDF-HFP is the matrix material of the gel electrolyte; therefore, the thermal decomposition temperature should be interpreted as 468℃. It can be observed that the thermal decomposition temperatures of the gel electrolyte and the commercial separator are 468℃ and 330℃, respectively, indicating that the thermal stability of the gel electrolyte prepared in Example 1 is significantly better than that of the commercial separator.

[0150] It should be noted that the thermal decomposition temperature of PVDF-HFP is 437℃. The increased decomposition temperature of the gel electrolyte prepared in Example 1 is attributed to the formation of numerous hydrogen bonds between CNFs and the molecular chains of PEO and PVDF-HFP, which improves the thermal stability of the electrolyte membrane. The specific reaction mechanism is as follows: after the addition of PEO polymer and PVDF-HFP polymer matrix for blending modification, a large number of hydrogen bond acceptors are generated. Then, CNFs are added for crosslinking modification, so that the hydroxyl functional groups on CNFs can form abundant intermolecular hydrogen bonds with the -CF2 and -COC hydrogen bond acceptors of the PVDF-HFP@PEO blend polymer to the greatest extent, which greatly improves the degree of crosslinking of the polymer chains, thereby forming a stable and uniform porous network structure.

[0151] The heat of combustion of the gel electrolyte prepared in Example 1 and the commercial membrane was tested using differential scanning calorimetry (DSC). The resulting DSC thermograms are shown below. Figure 4 ,Depend on Figure 4 It can be observed that the heat of combustion of the gel electrolyte prepared in Example 1 and the commercial diaphragm are 108.7 J / g and 21.3 J / g, respectively.

[0152] The gel electrolyte membrane prepared in Example 1 was assembled into a coin cell using stainless steel sheets as electrodes. Its lithium-ion conductivity was tested on an electrochemical workstation, and the test results are as follows: Figure 5 It is easy to observe that its lithium-ion conductivity is 3.8 × 10⁻⁶. -4 S·cm -1 ( Figure 5 This demonstrates that the gel electrolyte membrane material of the present invention possesses excellent ionic conductivity.

[0153] LiFePO4, Super P carbon black conductive agent, and PVDF were weighed in a mass ratio of 8:1:1, and N-methylpyrrolidone (NMP) was added and ground and mixed. The mixture was then coated on aluminum foil and dried at 80°C to form a positive electrode sheet. A 14mm*14mm*0.5mm lithium metal sheet was used as the negative electrode. In a glove box under a high-purity argon atmosphere, the positive electrode shell, positive electrode sheet, gel electrolyte prepared in Example 1, negative electrode sheet, and negative electrode shell were assembled into a full battery. The obtained full battery was subjected to constant current charge-discharge testing using a battery charge-discharge workstation, with a test voltage range of 2.5–4.0V. The test results are as follows: Figure 6 . Figure 6 The results show that the obtained full cell maintains a capacity retention of 82.5% after 1000 charge-discharge cycles at a 1C rate and 85.3% after 200 charge-discharge cycles at a 0.2C rate. The excellent cycle stability of the full cell demonstrates that the gel electrolyte prepared in Example 1 can maintain stable performance during long-term charge-discharge cycles.

[0154] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0155] In this application, unless otherwise stated, directional terms such as "upper" and "lower" specifically refer to the drawing directions in the accompanying drawings. Furthermore, in the description of this application, the terms "comprising," "including," etc., mean "including but not limited to." Moreover, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. For associations involving three or more related objects described using "and / or", it indicates that any one of the three related objects can exist alone, or at least two of them can exist simultaneously. For example, for A, and / or B, and / or C, it can mean that any one of A, B, and C exists alone, or any two of them exist simultaneously, or all three of them exist simultaneously. In this document, "at least one" means one or more, and "more than one" means two or more. "At least one", "at least one of the following", or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can each be single or multiple.

[0156] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for preparing a polymer, characterized in that, The polymer preparation method includes: A mixed system containing hexachlorocyclotriphosphazene, a predetermined monomer, and a natural polymer is provided, and the hexachlorocyclotriphosphazene, the predetermined monomer, and the natural polymer in the mixed system are copolymerized to obtain the polymer. The predetermined monomer is at least one of 1,2-bis(2-aminoethoxy)ethane and 4,4-diaminodiphenylmethane, and the natural polymer is at least one of cellulose, chitin, sodium alginate, hyaluronic acid, chitosan, guar gum, and gum arabic. The molar ratio of the hexachlorocyclotriphosphazene, the predetermined monomer, and the natural polymer is 1~50:3~150:3~300.

2. The polymer preparation method according to claim 1, characterized in that, The mixture system further includes an acid-binding agent; and / or, The mixture also includes a solvent.

3. The polymer preparation method according to claim 2, characterized in that, The average relative molecular mass of the natural polymer is between 1,000 and 220,000; and / or, The acid-binding agent is at least one selected from triethylamine, sodium acetate, sodium carbonate, and potassium carbonate; and / or... The solvent is selected from at least one of anhydrous ethanol, anhydrous acetonitrile, dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, and dichloromethane; and / or, The molar ratio of hexachlorocyclotriphosphazene, the predetermined monomer, the natural polymer, and the acid-binding agent is 1~50:3~150:3~300:3~30; and / or, The copolymerization temperature is 50~100℃; and / or, The copolymerization time is 6~24h.

4. A thin film for gel electrolytes, characterized in that, The thin film includes: 50-100 parts by weight of the main polymer; 5-20 parts by weight of plasticizer; 1 to 10 parts by mass of a polymer, wherein the polymer is prepared by the polymer preparation method according to any one of claims 1-3.

5. The thin film according to claim 4, characterized in that, The main polymer is at least one selected from polypropylene carbonate, polyvinyl carbonate, polyvinylidene fluoride, polyvinylidene fluoride-hexachloropropylene, polyethylene oxide, polyacrylonitrile, and polyfluoropropylene carbonate; and / or, The plasticizer is at least one of dibutyl phthalate, diethyl carbonate, succinic anhydride, polyethylene oxide, polyethylene glycol, ethylene carbonate, and propylene carbonate.

6. A method for preparing a thin film, characterized in that, The thin film is the thin film according to claim 4 or 5, and the method for preparing the thin film includes the following steps: The host polymer is provided, and the host polymer is prepared into a polymer slurry; The plasticizer is added to the polymer slurry, and the reaction is carried out at a first temperature to crosslink the main polymer, thereby obtaining a crosslinked polymer slurry; The polymer is added to the crosslinked polymer slurry and reacted at a second temperature to obtain a pre-prepared slurry; The pre-made slurry is added to a mold and the solvent is removed to obtain the film.

7. The method for preparing the thin film according to claim 6, characterized in that, The solvent for the polymer slurry is at least one selected from deionized water, ethanol, ethylene glycol, propylene glycol, isopropanol, acetone, N-methylpyrrolidone, and N,N-dimethylformamide; and / or, The first temperature is 50~80℃; and / or, The second temperature is 50~80℃.

8. A gel electrolyte, characterized in that, The gel electrolyte includes the film as described in claim 4 or 5, or the film prepared by the method described in claim 6 or 7; the gel electrolyte also includes an electrolyte, which includes lithium salt, sodium salt and organic solvent.

9. The gel electrolyte according to claim 8, characterized in that, The lithium salt is selected from at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalate borate, lithium dioxalate borate, and lithium bis(fluorosulfonyl)imide; and / or, The sodium salt is selected from one or more of sodium perchlorate, sodium hexafluorophosphate, sodium bis(trifluoromethanesulfonyl)imide, sodium chloride, sodium iodide, and their analogues and derivatives, and / or, The organic solvent is selected from ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, 1,3-diethyl carbonate, etc. At least one of cyclopentane and dimethyl ether; and / or, The total concentration of alkali metal ions in the lithium and sodium salts is 0.1 mol / L to 5 mol / L.

10. A battery, characterized in that, The battery is a lithium-ion battery or a sodium-ion battery, and the battery includes the gel electrolyte as described in claim 8 or 9.

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