A composite diaphragm based on solid electrolyte coating and preparation method thereof

Abstract

The invention discloses a composite diaphragm based on a solid electrolyte coating and a preparation method thereof. A modified polyaryletherketone polymer is prepared by using 3,3'-sodium disulfonate-4,4'-difluorobenzophenone, 4,4'-difluorobenzophenone, 2,2'-bis(4-hydroxyphenyl)hexafluoropropane and 4,4'-methylene-bis[2-(1H-benzimidazole-2-yl)]phenol as monomers, and the modified polyaryletherketone polymer is used as a polymer electrolyte, and an inorganic solid electrolyte is doped to prepare a composite diaphragm based on a solid electrolyte coating by a phase inversion method. The introduction of benzimidazole and fluorine-containing groups enhances the rigidity of the polyaryletherketone molecular chain, and the proton donor group on the benzimidazole ring generates hydrogen bonds with the main chain ether group or the side chain fluorine-containing group, so that the polyaryletherketone exhibits excellent mechanical properties and improves the tensile strength of the composite diaphragm; and the doping of the hydroxylated inorganic solid electrolyte makes the organic-inorganic solid electrolyte coating more tightly combined, further improving the ionic conductivity of the diaphragm.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and in particular to a composite diaphragm based on a solid electrolyte coating and a preparation method thereof. Background Art

[0002] Conventional commercial separators, such as polyolefin separators, have low electrolyte wettability and melting point, and are prone to shrink significantly when the battery undergoes thermal runaway, leading to internal short circuits and safety accidents. Therefore, it is particularly important to develop new types of high-heat-resistant separators that can increase the safe operating temperature window of the battery and prevent the separator from overheating and shrinking, especially those that can meet the requirements of high energy density.

[0003] Polyaryletherketone (PAEK) is a polymer rich in benzene rings and ether bonds in the chain. This molecular structure feature makes the polymer exhibit excellent high temperature resistance and mechanical properties. However, the solubility of conventional PAEK polymers is relatively poor, which is one of its material properties. Specifically, polyaryletherketone is insoluble in ordinary organic solvents and is almost insoluble in other organic solvents except concentrated sulfuric acid, and has strong solvent resistance. This poor solubility limits its processing and molding process, which limits the application range of polyaryletherketone. An effective method is to modify the polymer skeleton or introduce a heterocyclic structure into the main chain. This method can not only increase the glass transition temperature (Tg) of polyaryletherketone, improve its solubility, and make the polymer easy to process and shape; in addition, functional comonomers are introduced during the polymerization process to construct polymers with unique characteristics. For example, the invention patent CN118271592 A discloses a preparation method of polyetheretherketone, a preparation method of a diaphragm and a battery, which specifically uses 3,3'-disulfonic acid sodium-4,4'-difluorobenzophenone, 4,4'-difluorobenzophenone and tert-butylhydroquinone as basic monomers to prepare a sulfonated polyetheretherketone with a tert-butyl group, and mixes it with inorganic powder and carbon nanotubes to prepare a coating slurry for application in the diaphragm coating, which significantly improves the solubility of polyetheretherketone in polar solvents, making the material easy to process, and the introduction of carbon nanotubes improves the antistatic properties of the composite diaphragm. However, with the development of high-energy density batteries, higher requirements are placed on the ion conduction rate of the diaphragm; and the poor compatibility of inorganic particles with the polymer substrate leads to poor coating adhesion and poor mechanical properties of the composite diaphragm.

[0004] In view of this, the present invention aims at regulating the molecular structure of polyaryletherketone, introduces functional comonomers to synthesize new polyaryletherketone polymers with unique properties, combines them with inorganic solid electrolytes, and uses the diaphragm base film as the skeleton to construct a composite diaphragm based on solid electrolyte coating with both high ionic conductivity and mechanical strength. Summary of the invention

[0005] The invention discloses a composite diaphragm based on a solid electrolyte coating and a preparation method thereof. Firstly, the molecular structure of polyaryletherketone (PAEK) is innovatively designed, and 2,2'-bis(4-hydroxyphenyl)hexafluoropropane and 4,4'-methylene-bis[2-(1H-benzimidazole-2-yl)]phenol are introduced on the basis of sulfonated polyaryletherketone to prepare a series of fluorinated sulfonated polyaryletherketones with pendant benzimidazole groups. The polyaryletherketones are used as a polymer electrolyte with good solubility and thermal stability, and are doped with inorganic solid electrolytes to prepare a composite diaphragm based on a solid electrolyte coating through a phase inversion method, thereby improving the thermal stability, wettability and ion conductivity of the diaphragm.

[0006] In one aspect, the present invention provides a composite diaphragm based on a solid electrolyte coating, wherein the composite diaphragm comprises a diaphragm base membrane and a solid electrolyte coating.

[0007] The separator base film includes one of a polyethylene microporous film, a polypropylene microporous film, a polyimide microporous film, a polyethylene terephthalate microporous film, and a non-woven fabric separator;

[0008] Preferably, the diaphragm base film is a microporous film with high porosity, and further, the porosity of the diaphragm base film is greater than 60%;

[0009] Furthermore, the solid electrolyte coating is obtained by coating the coating slurry on the surface of the diaphragm base film, and then drying after non-solvent-induced phase separation;

[0010] The solid electrolyte coating has a thickness of 1 to 6 μm.

[0011] The solid electrolyte coating is applied to the surface of the diaphragm base membrane, and at least part of the solid electrolyte in the coating enters the pores of the base membrane; the diaphragm base membrane provides a skeleton for the composite solid electrolyte membrane, so that the composite diaphragm based on the solid electrolyte coating obtained in the present application has both high ionic conductivity and mechanical strength.

[0012] The coating slurry comprises a modified polyaryletherketone polymer, a hydroxylated inorganic solid electrolyte, polyethylene glycol and a solvent;

[0013] The molecular structure of the modified polyaryletherketone polymer comprises at least one of the following segments:

[0014]

[0015] and / or

[0016]

[0017] and / or

[0018] Among them, n≥1.

[0019] Furthermore, the modified polyaryletherketone polymer is prepared by the following method:

[0020] Provide basic monomers of 3,3'-disulfonato-sodium-4,4'-difluorobenzophenone (SDFBP), 4,4'-difluorobenzophenone (DFBP), 2,2'-bis(4-hydroxyphenyl)hexafluoropropane (BPAF) and 4,4'-methylene-bis[2-(1H-benzimidazol-2-yl)]phenol (MBIP); use potassium carbonate as a catalyst to synthesize modified polyaryletherketone polymers with different molar percentages of benzimidazole (x%) but with a constant degree of sulfonation (SD 60%) through nucleophilic polycondensation, denoted as x% SCBI-SPAEK-6F. The reaction process is shown in the figure below:

[0021] In the above reaction formula, the value of x is 0<x<1;

[0022] Alternatively, x=0, and a SPAEK-6F polymer is obtained, and the chain segment structure is ;

[0023] Alternatively, x=1, and a SCBI-SPAEK polymer is obtained, and the chain segment structure is .

[0024] Specifically, the steps are: adding the base monomer, potassium carbonate and a solvent mixture into a reaction container, wherein the solvent mixture is a mixture of N,N-dimethylacetamide and toluene (in a volume ratio of 7:3);

[0025] First, the monomer, potassium carbonate, and solvent mixture were refluxed at 130° C. in a nitrogen atmosphere for 3 to 5 hours. After dehydration and removal of toluene, the temperature was raised to 160 to 180° C. and maintained for 18 to 22 hours. Next, the reaction solution was cooled to room temperature, and the resulting polymer was precipitated in excess ethanol. Finally, the crude product was purified by a redissolution-precipitation cycle, and then vacuum dried at 80° C. for 12 hours to obtain x% SCBI-SPAEK-6F polymer.

[0026] Further, the x% SCBI-SPAEK-6F polymer with different benzimidazole mole percentages (x%) but a constant degree of sulfonation (SD 60%) was adjusted by changing the ratio of 2,2'-bis(4-hydroxyphenyl)hexafluoropropane and 4,4'-methylene-bis[2-(1H-benzimidazol-2-yl)]phenol.

[0027] The hydroxylated inorganic solid electrolyte includes one or more of a hydroxylated oxide electrolyte, a hydroxylated sulfide electrolyte or a hydroxylated phosphate electrolyte;

[0028] Preferably, the hydroxylated inorganic solid electrolyte is a hydroxylated oxide electrolyte;

[0029] Further, the hydroxylated oxide electrolyte includes one or more of hydroxylated LLZO, hydroxylated LLZTO, and hydroxylated LLTO;

[0030] Furthermore, the hydroxylated inorganic solid electrolyte is prepared by the following method: first, the untreated inorganic solid electrolyte is slowly dispersed in H 2 O 2 The dosage is m 无机固态电解质 / V H2O2 =1 / 50; then stir at 100°C for 1 hour, finally centrifuge at 2500-3500 r / min for 3-5 times, and repeatedly filter and wash with distilled water for 3 times, dry in a vacuum oven at 40°C for 24 hours, and store for later use;

[0031] Preferably, the particle size of the hydroxylated inorganic solid electrolyte is 100-600 nm.

[0032] The solvent is one of N,N-dimethylacetamide, N-methylpyrrolidone, N,N-dimethylformamide or dimethyl sulfoxide;

[0033] Preferably, the polyethylene glycol is PEG-200;

[0034] The amount of the modified aromatic ether ketone polymer, polyethylene glycol and solvent is x% SCBI-SPAEK-6F:PEG:solvent=4-6:1:20;

[0035] The amount of the hydroxylated inorganic solid electrolyte is 5-30% of the modified aromatic ether ketone polymer by weight;

[0036] Preferably, the amount of the hydroxylated inorganic solid electrolyte is 10-20% of the modified aromatic ether ketone polymer;

[0037] The modified polyaryletherketone polymer is the x% SCBI-SPAEK-6F polymer prepared by the above method;

[0038] Further, the modified polyaryletherketone polymer is 0% SCBI-SPAEK-6F polymer (SPAEK-6F), 5% SCBI-SPAEK-6F polymer, 10% SCBI-SPAEK-6F polymer, 15% SCBI-SPAEK-6F polymer;

[0039] Preferably, the modified polyaryletherketone polymer is a 10% SCBI-SPAEK polymer.

[0040] The non-solvent induced phase separation is to immediately immerse the coated membrane in an ethanol coagulation bath for 2 to 4 hours to perform phase transformation of the coating, and then dry to obtain a composite membrane.

[0041] In a second aspect, the present invention provides a method for preparing a composite diaphragm based on a solid electrolyte coating, specifically comprising:

[0042] Step 1: Preparation of coating slurry:

[0043] (1) Under an inert atmosphere (such as argon), the hydroxylated inorganic solid electrolyte and the modified polyaryletherketone polymer are ground and mixed, and the particle size of the inorganic solid electrolyte is adjusted to 50-300 nm to obtain a solid electrolyte mixture;

[0044] (2) mixing the solid electrolyte mixture, polyethylene glycol and a solvent at 60° C. under stirring to obtain a coating slurry;

[0045] Step 2: Preparation of composite diaphragm:

[0046] The degassed coating slurry is coated on the surface of the microporous diaphragm, and the coated diaphragm is immediately immersed in an ethanol coagulation bath for 2 to 4 hours to perform a phase transformation of the coating, and then dried to obtain a solid electrolyte coating composite diaphragm.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] (1) The present invention improves the solubility of the polymer in polar aprotic solvents (including DMAc, DMF, DMSO and NMP) at room temperature by innovatively designing the molecular structure of polyaryletherketone (PAEK) and introducing 2,2'-bis(4-hydroxyphenyl)hexafluoropropane and 4,4'-methylene-bis[2-(1H-benzimidazole-2-yl)]phenol on the basis of the sulfonic acid functional group. This is mainly attributed to the steric hindrance effect of the bulky pendant benzimidazole group and the hexafluoropropylene bridging group, which weakens the interaction between the polymer chains. The improvement of solubility in polar aprotic solvents simplifies the production process of the diaphragm and reduces safety risks. Secondly, the thermal stability is further improved. Due to the strong intramolecular ionic interaction between sulfonic acid and benzimidazole, the introduction of the benzimidazole group improves the thermal stability of the polymer, so that the composite diaphragm has more excellent thermal shrinkage performance.

[0049] (2) In addition, the present invention uses 4,4'-methylene-bis[2-(1H-benzimidazole-2-yl)]phenol and 2,2'-bis(4-hydroxyphenyl)hexafluoropropane to modify PAEK. The introduction of benzimidazole groups and fluorine-containing groups enhances the rigidity of the PAEK molecular chain, mainly because the proton donor group (-NH-) on the imidazole ring of the pendant benzimidazole group can generate a large number of hydrogen bonds with the ether group on the main chain or the fluorine-containing group on the side chain, so that it exhibits excellent mechanical properties and improves the tensile strength of the composite diaphragm;

[0050] (3) The sulfonic acid groups in the modified polyaryletherketone polymer of the present invention endow the polymer with unique ion exchange capacity. On the one hand, the ether bonds in the polymer can act as a solvent to promote the dissolution of lithium salts, and the dissociation of sulfonates on the polymer introduces more binding sites to form continuous ion channels or networks. These channels provide paths for the transmission of lithium ions, allowing lithium ions to migrate effectively in the polymer material, thereby enhancing the ion conductivity of the separator.

[0051] (4) Doping with hydroxylated inorganic solid electrolytes. Hydroxylation treatment improves the interfacial compatibility to obtain a more tightly bonded organic-inorganic solid electrolyte coating, further improving the ionic conductivity of the composite diaphragm, increasing the ionic conductivity, and increasing the energy density of the diaphragm. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 Schematic diagram of a composite diaphragm based on solid electrolyte coating.

[0053] 1——diaphragm base film; 2——solid electrolyte coating. DETAILED DESCRIPTION

[0054] To make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be described clearly and completely below. If no specific conditions are specified in the embodiments, the conventional conditions or the conditions recommended by the manufacturer shall be followed.

[0055] PE diaphragm, Hefei Changyang Technology New Energy Co., Ltd., porosity is 70~80%.

[0056] The modified polyaryletherketone polymer (x% SCBI-SPAEK-6F) was prepared by the following steps:

[0057] First, build a 1000 mL three-necked flask apparatus, install a water separator, and pass a nitrogen tube;

[0058] Subsequently, the base monomers and potassium carbonate are added to a three-necked flask according to a molar ratio of monomer 1: monomer 2: monomer 3: monomer 4 = 4:6: (10-0): (0-10), wherein monomer 1 is 4,4'-difluorobenzophenone, monomer 2 is 3,3'-sodium disulfonate-4,4'-difluorobenzophenone, monomer 3 is 2,2'-bis(4-hydroxyphenyl)hexafluoropropane, and monomer 4 is 4,4'-bis(methylene)-[2-(1H-benzimidazol-2-yl)]phenol; in terms of molar ratio, the amount of potassium carbonate used is 60% of the total amount of the base monomers; and then 200 mL to 300 mL of a mixture of N,N-dimethylacetamide and toluene (V / V ratio by volume) is added. DMAc :V 甲苯 =7:3); stirred at 130°C, reacted for 4 hours, and removed water.

[0059] The temperature was raised to 170 °C and maintained for 20 h; next, the reaction solution was cooled to room temperature and the resulting polymer was precipitated in excess ethanol; finally, the crude product was purified three times through redissolution-precipitation cycles and finally dried under vacuum at 80 °C for 12 h to obtain the x% SCBI-SPAEK polymer.

[0060] The ratio of the basic monomers is adjusted to 4:6:10:0 to obtain a SPAEK-6F polymer.

[0061] The ratio of the basic monomers was adjusted to 4:6:9.5:0.5 to obtain a 5% SCBI-SPAEK-6F polymer.

[0062] The ratio of the basic monomers was adjusted to 4:6:9:1 to obtain a 10% SCBI-SPAEK-6F polymer;

[0063] The ratio of the basic monomers was adjusted to 4:6:8.5:1.5 to obtain a 15% SCBI-SPAEK-6F polymer;

[0064] The ratio of the basic monomers is adjusted to 4:6:0:10 to obtain a SCBI-SPAEK polymer;

[0065] The ratio of the basic monomers is adjusted to monomer 1: monomer 2: monomer 3: monomer 4 = 4: 6: 0: 0 to obtain a SPAEK polymer.

[0066] Hydroxylation treatment of LLZO: First, 1 g of untreated LLZO was slowly dispersed in 50 mL of H 2 O 2The mixture was stirred at 100°C for 1 hour, then centrifuged at 2500-3500 r / min for 3-5 times in a centrifuge, and filtered and washed with distilled water for 3 times, dried in a vacuum oven at 40°C for 24 hours, and stored for later use.

[0067] Example 1

[0068] A composite diaphragm based on a solid electrolyte coating, the composite diaphragm comprising a diaphragm base film and a solid electrolyte coating, such as Figure 1 As shown, the specific preparation method is as follows:

[0069] Step 1: Preparation of coating slurry:

[0070] (1) Under an inert atmosphere (such as argon), 7.5 parts of hydroxylated LLZO and 50 parts of 5% SCBI-SPAEK-6F polymer are ground and mixed, and the particle size of the inorganic solid electrolyte is adjusted to 50 to 300 nm to obtain a solid electrolyte mixture;

[0071] (2) mixing the solid electrolyte mixture obtained in step (1) with 10 parts of PEG 200 and 200 parts of N,N-dimethylacetamide at 60° C. under stirring to obtain a coating slurry with a solid content of about 23%;

[0072] Step 2: Preparation of composite diaphragm:

[0073] The degassed coating slurry was applied to both sides of the PE diaphragm to form a uniform coating with a thickness of 4 μm. The coated diaphragm was immediately immersed in an ethanol coagulation bath for 2 to 4 hours to perform a phase transformation of the coating, and then dried to obtain a solid electrolyte coating composite diaphragm.

[0074] Example 2

[0075] The modified polyaryletherketone polymer in Example 1 was adjusted to 10% SCBI-SPAEK-6F polymer, and the other steps remained unchanged.

[0076] Example 3

[0077] The modified polyaryletherketone polymer in Example 1 was adjusted to 15% SCBI-SPAEK-6F polymer, and the other steps remained unchanged.

[0078] Example 4

[0079] The modified polyaryletherketone polymer in Example 1 was adjusted to SPAEK-6F polymer, and the other steps remained unchanged.

[0080] Example 5

[0081] The modified polyaryletherketone polymer in Example 1 was adjusted to SCBI-SPAEK polymer, and the other steps remained unchanged.

[0082] Example 6

[0083] The amount of hydroxylated LLZO in Example 2 was adjusted to 2.5 parts, and the other steps remained unchanged.

[0084] Example 7

[0085] The amount of hydroxylated LLZO in Example 2 was adjusted to 15 parts, and the other steps remained unchanged.

[0086] Comparative Example 1

[0087] The modified polyaryletherketone in Example 1 was adjusted to a 60% sulfonated polyaryletherketone polymer, namely, SPAEK polymer, and the other steps remained unchanged.

[0088] Comparative Example 2

[0089] The amount of hydroxylated LLZO in Example 2 was adjusted to 0 parts, and the other steps remained unchanged.

[0090] Comparative Example 3

[0091] The inorganic solid electrolyte in Example 2 was adjusted to conventional LLZO, and the other steps remained unchanged.

[0092] Comparative Example 4

[0093] PE diaphragm, uncoated.

[0094] The performance of the composite diaphragms prepared in Examples 1-7 and Comparative Examples 1-4 was tested in the following manner, and the data results are shown in Table 1:

[0095] (1) Tensile strength test: Test according to the tensile strength test method in the national standard "GB / T-36363-2018";

[0096] (2) Liquid absorption rate test: A 1 mol lithium hexafluorophosphate solution of dimethyl carbonate and ethyl methyl carbonate were mixed in a volume ratio of 1:1 to prepare an electrolyte, and then the composite diaphragm sample was immersed in the electrolyte for 12 h. After completion, the excess electrolyte on the surface was wiped off and the liquid absorption rate was calculated;

[0097] (3) Ionic conductivity test: The ionic conductivity of each composite membrane was tested with reference to the relevant ionic conductivity test method of GB / T 36363-2018;

[0098] (4) Heat resistance test: The heat resistance of the diaphragm is characterized by the heat shrinkage rate. The test is carried out according to the test method for heat shrinkage rate in the national standard "GB / T-36363-2018". The instrument uses a blast oven;

[0099] (5) Air permeability test: The test is conducted according to the air permeability test method in the national standard GB / T-36363-2018. The air permeability results are expressed by the Gurley value. The smaller the Gurley value, the shorter the time for gas to pass through, and the better the air permeability of the membrane.

[0100] (6) Peel strength test: The test is conducted according to the method in the national standard "GB / T 2792-2014 Peel strength of adhesive tapes", and the instrument used is a universal material testing machine.

[0101] Table 1 Summary of the test results of battery separator performance prepared in Examples 1-7 and Comparative Examples 1-4

[0102]

[0103] From the comparison of the data of Examples 1 to 5 and Comparative Examples 1 and 4 in the table, it can be seen that after modification with 2,2'-bis(4-hydroxyphenyl)hexafluoropropane and 4,4'-methylene-bis[2-(1H-benzimidazol-2-yl)]phenol, the ionic conductivity, thermal shrinkage, tensile strength, etc. of the composite diaphragm based on the modified polyaryletherketone polymer coating are significantly improved; this may be because, on the one hand, polyaryletherketone is a polymer rich in benzene rings and ether bonds in the chain, and the molecular structure characteristics make the polymer itself show relatively excellent high temperature resistance; on the other hand, On the one hand, the introduction of phenylimidazole groups and fluorinated groups, the proton donor group (-NH-) on the imidazole ring of the pendant phenylimidazole group can generate a large number of hydrogen bonds with the ether group on the main chain or the fluorinated group on the side chain, further improving the mechanical strength of the composite coating, resulting in improved tensile strength of the composite diaphragm; secondly, the dissociation of sulfonates on the modified polyaryletherketone structure introduces more binding sites to form continuous ion channels or networks, which provide paths for the transmission of lithium ions; at the same time, the -N= group on the phenylimidazole group can interact with Li + The attraction is exerted to promote the dissociation of lithium salts, and the hydrogen bonds formed between -NH- groups also anchor the lithium salt anions, hindering their movement while promoting Li + Therefore, the functional groups work synergistically to promote the separation of free Li + The increase in concentration and the kinetic limitation of anion migration together increase the number of lithium ion migration, thereby improving ionic conductivity, helping to increase the energy density of lithium batteries and improving their tensile strength.

[0104] Comparison of the data of Example 2, Example 6-7 with Comparative Example 2 and Comparative Example 3 shows that after adding an appropriate amount of hydroxylated LLZO active inorganic filler, on the one hand, the doping of inorganic particles is conducive to the formation of a multi-morphology coating, and some particles enter the polymer pore structure as part of the skeleton, playing a supporting role, which helps to improve the air permeability of the diaphragm (low Gurley value), and at the same time increases the contact area between the diaphragm and the electrolyte to increase the liquid absorption rate, and can preserve the immersed electrolyte to increase the liquid absorption rate of the diaphragm and improve the ionic conductivity; on the other hand, LLZO can inhibit polymer crystallization, promote polymer chain segment movement, and promote lithium salt dissociation, and LLZO can directly participate in lithium ion (Li + ) conduction, thereby further improving the ionic conductivity of the composite diaphragm. However, adding too many particles is not conducive to the mechanical properties of the coating, and the inorganic particles and the polymer interface compatibility are poor, resulting in a decrease in the tensile strength of the composite material and a deterioration in the adhesion between the coating and the diaphragm. Therefore, the use of hydroxylated LLZO fillers makes the polymer and the oxide more closely combined, improves the mechanical properties while reducing the impedance increase caused by the interface, inhibits the contact deterioration caused by the volume change of the oxide solid electrolyte during the cycle, and at the same time expands the voltage window and chemical stability of the polymer solid electrolyte, improving the electrochemical properties of the composite diaphragm.

Claims

1. A composite diaphragm based on a solid electrolyte coating, comprising a diaphragm base film and a solid electrolyte coating arranged on the surface of the diaphragm base film, characterized in that: The solid electrolyte coating comprises a modified polyaryletherketone polymer, a hydroxylated inorganic solid electrolyte and polyethylene glycol; the amount of the modified polyaryletherketone polymer and the polyethylene glycol is 4 to 6:1 by weight, and the amount of the hydroxylated inorganic solid electrolyte is 5 to 30% of the modified polyaryletherketone polymer; the molecular structure of the modified polyaryletherketone polymer comprises at least one of the following segments: and / or , Among them, n≥1.

2. A composite diaphragm based on a solid electrolyte coating according to claim 1, characterized in that: The modified polyaryletherketone polymer is a modified polyaryletherketone polymer having different molar percentages of benzimidazole but a constant degree of sulfonation, which is synthesized by nucleophilic polycondensation reaction using potassium carbonate as a catalyst, 3,3'-sodium disulfonate-4,4'-difluorobenzophenone, 4,4'-difluorobenzophenone, 2,2'-bis(4-hydroxyphenyl)hexafluoropropane and 4,4'-methylene-bis[2-(1H-benzimidazole-2-yl)]phenol as basic monomers. The preparation method is as follows: providing basic monomers of 3,3'-sodium disulfonate-4,4'-difluorobenzophenone, 4,4'-difluorobenzophenone, 2,2'-bis(4-hydroxyphenyl)hexafluoropropane and 4,4'-methylene-bis[2-(1H-benzimidazol-2-yl)]phenol; heating the basic monomers and potassium carbonate in a solvent mixture to carry out a nucleophilic polycondensation reaction; after the nucleophilic polycondensation reaction is completed, precipitating and purifying the reaction mixture in ethanol to obtain a crude product.

3. A composite diaphragm based on a solid electrolyte coating according to claim 2, characterized in that: The solid electrolyte coating is obtained by coating the coating slurry on the surface of the diaphragm base film, performing non-solvent-induced phase separation, and then drying.

4. A composite diaphragm based on a solid electrolyte coating according to claim 2, characterized in that: The solvent mixture is a mixture of N,N-dimethylacetamide and toluene in a volume ratio of 7:

3.

5. A composite diaphragm based on a solid electrolyte coating according to claim 4, characterized in that: The solid electrolyte coating has a thickness of 1 to 6 μm.

6. A composite diaphragm based on a solid electrolyte coating according to claim 3, characterized in that: The coating slurry comprises a modified polyaryletherketone polymer, a hydroxylated inorganic solid electrolyte, polyethylene glycol and a solvent; in terms of mass, the amount of the modified polyaryletherketone polymer, polyethylene glycol and the solvent is the modified polyaryletherketone polymer: polyethylene glycol: solvent = 4 to 6:1:

20.

7. A composite diaphragm based on a solid electrolyte coating according to claim 6, characterized in that: The hydroxylated inorganic solid electrolyte is prepared by the following method: first, slowly dispersing an untreated inorganic solid electrolyte in H2O2 in an amount of m 无机固态电解质 / V H2O2 =1 / 50; then stirred at 100°C for 1 hour, finally centrifuged at 2500-3500 r / min in a centrifuge for 3-5 times, and repeatedly filtered and washed with distilled water for 3 times, and dried in a vacuum oven at 40°C for 24 hours.

8. A composite diaphragm based on a solid electrolyte coating according to claim 7, characterized in that: The diaphragm base film comprises one of a polyethylene microporous film, a polypropylene microporous film, a polyimide microporous film, a polyethylene terephthalate microporous film, and a non-woven fabric diaphragm; the porosity of the diaphragm base film is greater than 60%.

9. A composite diaphragm based on a solid electrolyte coating according to claim 6, characterized in that: The hydroxylated inorganic solid electrolyte includes one or more of a hydroxylated oxide electrolyte, a hydroxylated sulfide electrolyte or a hydroxylated phosphate electrolyte; the solvent is one of N,N-dimethylacetamide, N-methylpyrrolidone, N,N-dimethylformamide or dimethyl sulfoxide.

10. A method for preparing a composite diaphragm based on a solid electrolyte coating according to any one of claims 1 to 9, characterized in that: Specifically include: Step 1: Preparation of coating slurry: (1) grinding and mixing a hydroxylated inorganic solid electrolyte and a modified polyaryletherketone polymer under an inert atmosphere, and adjusting the particle size of the solid electrolyte to obtain a solid electrolyte mixture; (2) mixing the solid electrolyte mixture, polyethylene glycol and solvent at 60° C. under stirring to obtain a coating slurry; the particle size of the hydroxylated inorganic solid electrolyte in (1) of the preparation of the coating slurry is adjusted to 50 to 300 nm; Step 2, preparation of composite diaphragm: coating the degassed coating slurry onto the surface of the microporous diaphragm, immediately immersing the coated diaphragm in an ethanol coagulation bath for 2 to 4 hours to perform a phase transformation of the coating, and then drying to obtain a solid electrolyte coating composite diaphragm.

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