Composite solid electrolyte taking fluorinated carbon nitride as filler as well as preparation method and application of composite solid electrolyte

Abstract

The invention relates to the technical field of energy storage material development, and discloses a composite solid electrolyte with fluorinated carbon nitride as a filler and a preparation method and application thereof.The method comprises the steps that dicyandiamide and sodium fluoride are mixed and ground, ground powder is transferred to a crucible and placed in a muffle furnace, carbonization treatment is conducted in the air atmosphere, and the carbon nitride-based composite solid electrolyte is obtained; a faint yellow powder target product fluorinated carbon nitride is obtained; blending the fluorinated carbon nitride with ultrapure water and absolute ethyl alcohol, stripping by adopting a cell crusher, standing suspension liquid after crushing cells, and freeze-drying an upper-layer solution to obtain a powdery few-layer fluorinated carbon nitride sample; meanwhile, fluorine-containing single-ion polymer lithium salt is synthesized to improve the ionic conductivity, and polyethylene oxide is used as a polymer matrix to prepare the composite solid electrolyte. The prepared composite solid electrolyte has excellent ionic conductivity, a stable interface and a wide electrochemical window, and high stability and cycle performance of a lithium metal battery are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy storage material development, and particularly relates to a composite solid electrolyte filled with fluorinated carbon nitride, a preparation method thereof, and an application thereof. Background Art

[0002] All-solid-state lithium metal batteries have attracted extensive attention to meet the high safety and capacity requirements of high-efficiency electric vehicles and portable electronic devices. As an important component of all-solid-state batteries, solid electrolytes greatly affect the performance of the batteries. Low cost, light weight, chemical stability, and mechanical flexibility make polymer solid electrolytes an ideal choice for solid-state batteries. Common polymer solid electrolytes have attracted extensive attention due to their flexibility and easy manufacturability. However, their practical applications are limited by their low ionic conductivity (10 -5 ~10 -7 S cm -1 ), low shear modulus, and narrow potential window. At the same time, the poor interfacial contact / compatibility between polymer solid electrolytes and electrodes still seriously hinders the development of all-solid-state lithium metal batteries. On the one hand, different from traditional batteries in which electrodes (including anodes and cathodes) are easily wetted by liquid electrolytes, the interfacial contact between the electrodes and electrolytes of all-solid-state lithium metal batteries is poor, which is caused by the rigidity of solid materials and the volume change of active materials during battery operation, resulting in low rate and poor cycling performance. On the other hand, side reactions caused by electrolyte / electrode incompatibility also severely limit their practical applications.

[0003] To solve the problems encountered by polymer solid electrolytes, researchers have been exploring various improvement strategies. One of them is to prepare composite solid electrolytes by combining inorganic ceramics and polymer matrices, which can not only improve the mechanical properties and ionic conductivity at room temperature but also enhance the interfacial contact between the composite solid electrolyte and lithium metal. However, the mechanical properties of polymer electrolytes decrease with the addition of inorganic fillers, and they may separate from the electrolyte during cycling, thereby affecting the electrochemical performance. Therefore, how to effectively improve the ionic conductivity of solid electrolytes while maintaining the advantages of safety and stability, and broaden the electrochemical window, remains a hot spot and difficulty in current research. Summary of the Invention

[0004] In order to overcome the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a composite solid electrolyte filled with fluorinated carbon nitride, a preparation method thereof, and an application thereof, so as to solve the technical problems of low conductivity and narrow chemical window of pure polyethylene oxide-based solid electrolytes in the prior art.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a method for preparing a composite solid electrolyte with fluorinated carbon nitride as a filler, comprising the following steps:

[0007] S1, Mix and grind dicyandiamide and sodium fluoride, transfer the ground dicyandiamide powder to a crucible and place it in a muffle furnace, heat and keep warm for carbonization treatment to obtain a pale yellow powder target product, fluorinated carbon nitride;

[0008] S2, Mix fluorinated carbon nitride with ultrapure water and absolute ethanol, use a cell crusher to exfoliate, and let the suspension after cell crushing stand to obtain a powdery few-layer fluorinated carbon nitride sample;

[0009] S3, Under ice bath conditions, add carbon disulfide and 2-bromopropionic acid to tert-butyl mercaptan, and react to prepare intermediate product A. The structural formula of the intermediate product A is as follows:

[0010]

[0011] Under ice bath and nitrogen protection, react polyethylene glycol monomethyl ether and 4-vinylbenzyl chloride to prepare intermediate product B. The structural formula of the intermediate product B is as follows:

[0012]

[0013] Add styrenesulfonyl chloride to anhydrous and anaerobic acetonitrile, add fluorobenzenesulfonamide, 4-dimethylaminopyridine and triethylamine, stir and react under ice bath conditions. After the reaction ends, react the reaction product with anhydrous lithium hydroxide to prepare a fluorinated single-ion lithium salt. The structural formula of the fluorinated single-ion lithium salt is as follows:

[0014]

[0015] S4, Add the fluorinated single-ion lithium salt, polyethylene oxide and fluorinated carbon nitride to N,N'-dimethylformamide, continuously heat and stir until completely dissolved and dried to obtain a composite solid electrolyte.

[0016] A further improvement of the present invention is that, by weight, the ratio of dicyandiamide to sodium fluoride is 4:1 to 8:1.

[0017] A further improvement of the present invention is that the muffle furnace is heated at a rate of 5-10 °C min -1 to 520-550 °C and kept warm at this temperature for 3-5 h, and then naturally cooled to room temperature to complete the carbonization treatment process.

[0018] A further improvement of the present invention is that, by mass, the ratio of tert-butyl mercaptan, carbon disulfide and 2-bromopropionic acid is 3:(1-10):(5-15).

[0019] A further improvement of the present invention lies in that, by mass parts, the ratio of the polyethylene glycol monomethyl ether to 4-vinylbenzyl chloride is (2 - 5):(1 - 3).

[0020] A further improvement of the present invention lies in that, by mass parts, the ratio of the styrenesulfonyl chloride to 4-fluorobenzenesulfonamide is (14 - 20):(8 - 10).

[0021] A further improvement of the present invention lies in that, by mass parts, the ratio of the fluorinated carbon nitride to polyethylene oxide is (2 - 8):(8 - 12); the ratio of the fluorinated single-ion polymer lithium salt to polyethylene oxide is (16 - 20):1.

[0022] A further improvement of the present invention lies in that, in S4, the temperature for continuous heating and stirring is 50 - 80 °C, and the time is 10 - 16 h.

[0023] In a second aspect, the present invention also provides a composite solid electrolyte filled with fluorinated carbon nitride prepared by the above preparation method.

[0024] In a third aspect, the composite solid electrolyte filled with fluorinated carbon nitride provided by the present invention can be applied in the preparation of lithium metal batteries.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention provides a preparation method of a composite solid electrolyte filled with fluorinated carbon nitride. Fluorinated carbon nitride is synthesized by a simple high-temperature carbonization process, and then few-layer fluorinated carbon nitride is prepared by a liquid-phase exfoliation method, further improving the dispersion in the polymer and promoting the dissociation of lithium ions. As a new type of two-dimensional material, fluorinated carbon nitride can form an ion transport network in the polymer, effectively improving the ionic conductivity. The two-dimensional fluorinated carbon nitride nanosheets have a larger interaction area with the polymer, and the polymer chains are not prone to relative slippage under external forces, thereby improving the mechanical properties of the electrolyte. The surface of fluorinated carbon nitride is rich in nitrogen atoms, and the nitrogen atoms interact with the lithium salt polymer in the polymer, increasing the dissociation of lithium ions. Finally, different from other two-dimensional materials, the defects on the surface of fluorinated carbon nitride can be regarded as potential channels for vertical lithium ion transport, further improving the ion transport ability. Finally, a composite solid electrolyte filled with fluorinated carbon nitride is constructed, which has excellent ionic conductivity, a stable interface, and a wide electrochemical window, realizing the high stability and cycling performance of lithium metal batteries.

[0027] Furthermore, the composite solid electrolyte filled with fluorinated carbon nitride provided by the present invention has an electrochemical window of 3.5 - 5 V at room temperature. Description of the Drawings

[0028] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of the disclosure of the present invention in any way. Additionally, the shapes and proportional dimensions of the components in the figures are only schematic and are used to assist in understanding the present invention, rather than specifically defining the shapes and proportional dimensions of the components of the present invention.

[0029] Figure 1 It is a reaction process diagram for the preparation method of intermediate A of the present invention;

[0030] Figure 2 It is a reaction process diagram for the preparation method of intermediate B of the present invention;

[0031] Figure 3 It is a reaction process diagram for the preparation method of single-ion conductor polymer lithium salt of the present invention;

[0032] Figure 4 It is an XRD spectrum diagram of the inorganic filler prepared in Examples 1 to 3 of the present invention;

[0033] Figure 5 It is a transmission diagram of the composite solid electrolyte prepared in Examples 1 to 3 of the present invention;

[0034] Figure 6 It is the electrochemical window of the composite solid electrolyte prepared in Examples 1 to 3 of the present invention at 25°C. Detailed implementation manners

[0035] To enable those skilled in the art to understand the features and effects of the present invention, the following provides a general description and definition of the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein shall have the ordinary meaning understood by those skilled in the art regarding the present invention. In case of conflict, the definition in this specification shall prevail.

[0036] The theories or mechanisms described and disclosed herein, whether correct or incorrect, shall not limit the scope of the present invention in any way, that is, the content of the present invention can be implemented without being limited by any specific theory or mechanism.

[0037] In this document, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are only for the sake of brevity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be regarded as having covered and specifically disclosed all possible sub-ranges and individual numerical values within the range (including integers and fractions).

[0038] In this document, unless otherwise specified, the terms "comprising", "including", "containing", "having", or similar terms cover the meanings of "consisting of" and "consisting essentially of". For example, "A comprises a" covers the meanings of "A comprises a and others" and "A consists only of a".

[0039] In this text, for the sake of concise description, not all possible combinations of all technical features in each implementation or embodiment are described. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation or embodiment can be combined arbitrarily, and all possible combinations should be considered as the scope described in this specification.

[0040] The present invention provides a method for preparing a composite solid electrolyte with fluorinated carbon nitride as a filler, comprising the following steps:

[0041] Step S1, mix and grind dicyandiamide and sodium fluoride, transfer the ground dicyandiamide powder to a crucible and place it in a muffle furnace, heat and keep warm in an air atmosphere for carbonization treatment to obtain a pale yellow powder target product, fluorinated carbon nitride;

[0042] Among them, by weight, the ratio of dicyandiamide to sodium fluoride is 4:1 to 8:1;

[0043] The muffle furnace is heated at a rate of 5 - 10 °C / min -1 to 520 - 550 °C and kept warm at this temperature for 3 - 5 h, and then naturally cooled to room temperature to complete the carbonization treatment process.

[0044] Step S2, mix fluorinated carbon nitride with ultrapure water and absolute ethanol, use a cell disruptor to exfoliate, and let the suspension after cell disruption stand, and freeze-dry the upper layer solution to obtain a powdery few-layer fluorinated carbon nitride sample;

[0045] Among them, weigh 0.5 - 1 g of fluorinated carbon nitride and dissolve it in a mixed solvent of ultrapure water and absolute ethanol (volume ratio of 1:2 to 1:1), ultrasonically treat for 120 - 160 min, let the suspension stand for 24 - 48 h to complete the liquid-phase exfoliation process.

[0046] Step S3, under ice bath conditions, add carbon disulfide and 2-bromopropionic acid to tert-butyl mercaptan, and react to obtain intermediate product A, and the structural formula of the intermediate product A is formula (Ⅰ):

[0047]

[0048] Under ice bath and nitrogen protection, make polyethylene glycol monomethyl ether and 4-vinylbenzyl chloride react to obtain intermediate product B, and the structural formula of the intermediate product B is formula (Ⅱ):

[0049]

[0050] Add styrenesulfonyl chloride to anhydrous and oxygen-free acetonitrile, and add fluorobenzenesulfonamide, 4-dimethylaminopyridine, and triethylamine. Stir the reaction under an ice bath. After the reaction is completed, react the reaction product with anhydrous lithium hydroxide to obtain a fluorinated single-ion lithium salt. The structural formula of the fluorinated single-ion lithium salt is formula (Ⅲ):

[0051]

[0052] Among them, by mass fraction, the ratio of tert-butyl mercaptan, carbon disulfide, and 2-bromopropionic acid is 3:(1-10):(5-15);

[0053] By mass fraction, the ratio of polyethylene glycol monomethyl ether and 4-vinylbenzyl chloride is (2-5):(1-3);

[0054] By mass fraction, the ratio of styrenesulfonyl chloride and 4-fluorobenzenesulfonamide is (14-20):(8-10).

[0055] Step S4, add the fluorinated single-ion lithium salt, polyethylene oxide, and fluorinated carbon nitride to N,N'-dimethylformamide, and continuously heat and stir at a temperature of 50-80 °C for 10-16 h until completely dissolved and dried to obtain a composite solid electrolyte;

[0056] Among them, by mass fraction, the ratio of fluorinated carbon nitride and polyethylene oxide is (2-8):(8-12); the ratio of the fluorinated single-ion polymer lithium salt and polyethylene oxide is (16-20):1.

[0057] Furthermore, a preparation method of a composite solid electrolyte using fluorinated carbon nitride as a filler includes the following steps:

[0058] Step 1, by mass fraction, weigh the ratio of dicyandiamide and sodium fluoride as 4:1-8:1, grind in a mortar for 30-60 min, transfer the ground dicyandiamide powder to a crucible and place it in a muffle furnace, and heat it at a rate of 5-10 °C / min -1 to 520-550 °C and keep it at this temperature for 3-5 h, naturally cool to room temperature, wash with water and filter by suction to remove water-soluble impurities, and obtain light yellow powder fluorinated carbon nitride through freezing, drying, grinding, and sieving, denoted as g-C 3 N 4 ;

[0059] Step 2, Weigh 0.5 - 1 g of fluorinated carbon nitride and dissolve it in a mixed solvent of ultrapure water and absolute ethanol (the volume ratio of the two is 1:2 to 1:1). Place an ice bag around the beaker to keep the solution temperature not higher than 30 °C during ultrasonic treatment. Ultrasonic treat for 120 - 160 min (ultrasonic for 1 s, interval for 2 s); Let the suspension after cell crushing stand for 24 - 48 h, and then freeze-dry the upper solution to obtain a powdery few-layer fluorinated carbon nitride sample, denoted as F-g-C 3 N 4 ;

[0060] Step 3, By mass fraction, add 3 parts of tert-butyl mercaptan to 5 parts of ultrapure water and stir evenly to obtain a mixed solution; Drop a NaOH aqueous solution with a mass fraction of 40% - 50% into the above mixed solution and stir well. Stir the system to make the pH value of the system 8 - 12; Slowly add acetone (20.0 mL - 50.0 mL) to obtain a colorless transparent solution, stir for 0.5 - 1.0 h and cool to room temperature; Transfer the above reaction to an ice bath, add 1 - 10 parts of carbon disulfide, 5 - 15 parts of 2-bromopropionic acid and a NaOH aqueous solution with a mass fraction of 40% - 50%. Adding NaOH here makes the reaction process more complete. Control the reaction temperature not exceeding 60 °C. After the reaction stops exotherming, remove the ice bath and continue the reaction at room temperature for 24 - 48 h; After the reaction is completed, add 5 - 10 parts of concentrated hydrochloric acid and control the temperature below 10 °C to obtain a yellow oil layer and stir until it solidifies, wash with a large amount of ultrapure water, and vacuum dry for 12 - 15 h to obtain a yellow solid, obtaining the target product 2-{[(butylthio)thioxomethyl]thio}propanoic acid, denoted as BCSPA. The reaction equation in this process is shown in Figure 1 , and the structural formula of the product BCSPA is shown in (I):

[0061]

[0062] Step 4, Slowly add 1 - 5 parts of sodium hydride to 5 - 10 parts of dry and water-free tetrahydrofuran under nitrogen purging. Place it in an ice bath and add 2 - 5 parts of polyethylene glycol monomethyl ether with a molecular weight of 750 and 1 - 3 parts of 4-vinylbenzyl chloride, and react for 12 - 14 h; Then perform rotary evaporation on it, add dichloromethane and ultrapure water for extraction and filtration to obtain the pale yellow target product 4-vinylbenzyl-polyethylene glycol monomethyl ether, denoted as VBMPEG 750 ; In this process, the nitrogen atmosphere can prevent oxygen from participating in the reaction or causing the reactants to oxidize; Sodium hydride (NaH) is a strong base and is often used to generate organometallic compounds or carry out deprotonation reactions. In dry tetrahydrofuran, it can better play its basic role. The ice bath condition is used to control the reaction temperature to prevent the reaction from being too violent or producing unnecessary side reactions; Rotary evaporation can remove the solvent tetrahydrofuran, and extraction and filtration can remove unreacted reactants and by-products; The reaction equation in this process is shown inFigure 2 , the product VBMPEG 750 The structural formula of is shown in (II):

[0063]

[0064] Step 5, Add 5 parts of thionyl chloride (SOCl 2 ), 2 parts of sodium 4-styrenesulfonate and 6 parts of anhydrous N,N'-dimethylformamide (DMF) into a flask, stir successively for 0.5 - 5 h under ice bath conditions and for 6 - 10 h at room temperature. After completion, styrenesulfonyl chloride (SSC) is obtained through freezing, filtration and evaporation; Add fluorobenzenesulfonamide, 4-dimethylaminopyridine and triethylamine into anhydrous and oxygen-free acetonitrile (ACN). Among them, by mass parts, the ratio of the styrenesulfonyl chloride to fluorobenzenesulfonamide, 4-dimethylaminopyridine and triethylamine is (14 - 20):(15 - 20):1:(17 - 19). Stir for 0.5 - 3 h under ice bath conditions. After the reaction is completed, add an appropriate amount of anhydrous magnesium sulfate to the above mixed solution, dry, filter and evaporate to remove dichloromethane to obtain a yellow viscous product; Finally, dissolve the product and anhydrous lithium hydroxide (mass parts ratio is 20:(13 - 19)) in an appropriate amount of dichloromethane (Dichloromethane, DCM), stir at room temperature for 24 - 36 h to form a light yellow solution, that is, the target product, fluorine-containing single-ion lithium salt is obtained.

[0065] In this process, 4-dimethylaminopyridine (4-dimethylamino-pyridine, DMAP) is used as a catalyst for the acylation reaction, which can promote the reaction; Triethylamine (Triethylamine, Et3N) is used as a base to neutralize the acid generated during the reaction and also helps to increase the solubility of the reactants; The anhydrous and oxygen-free conditions are to prevent the reactants from being oxidized or hydrolyzed; The reaction equation in this process is shown in Figure 3 , The structural formula of the fluorine-containing single-ion lithium salt is shown in formula (III):

[0066]

[0067] Step 6, By mass parts, blend 3 - 8 parts of F-g-C 3 N 4 with 9 - 12 parts of polyethylene oxide and add them into a round-bottom flask containing 25.0 - 50.0 mL of N,N'-dimethylformamide, where the solid content is 3% - 8% (here the solid content refers to F-g-C 3 N 4(by mass percentage of polyethylene oxide), heat at 50 - 80 °C, stir for 1 - 3 h, and then add a fluorinated single-ion lithium salt. By mass fraction, the ratio of polyethylene oxide to the fluorinated single-ion lithium salt is (16 - 20):1, which can make the composite solid electrolyte have excellent conductivity. Continuously heat and stir for 10 - 16 h to completely dissolve and uniformly mix the mixture. Finally, pour the above mixture into a polytetrafluoroethylene plate and dry it in a vacuum oven at 30 - 70 °C for 24 - 48 h to obtain the composite solid electrolyte.

[0068] The present invention also provides a composite solid electrolyte prepared by the above preparation method using carbon nitride fluoride as a filler. The electrochemical window of this composite solid electrolyte at room temperature is 3.5 - 5 V.

[0069] The two-dimensional carbon nitride fluoride nanosheets used in the present invention have a larger interaction area with the polymer, and the surface is rich in nitrogen atoms. The nitrogen atoms interact with the lithium salt polymer in the polymer, increasing the dissociation of lithium ions; through the reasonable design of the single-ion conductor polymer lithium salt, a strong electron-withdrawing group is introduced into the lithium salt monomer, increasing the delocalization of negative charges in the anion group and improving the dissociation ability of lithium ions in the lithium salt; the polyethylene oxide matrix has the advantages of low cost, good flexibility, and good processability, and has been widely studied; finally, a composite solid electrolyte using carbon nitride fluoride as a filler is constructed, which has excellent ionic conductivity, stable interface, wide electrochemical window and other characteristics, realizing the high stability and cycling performance of lithium metal batteries.

[0070] The following further elaborates the present invention in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0071] Conventional instrument and equipment in the art are used in the following examples. For the experimental methods without specific conditions noted in the following examples, they are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer. Various raw materials are used in the following examples. Unless otherwise stated, commercially available products are used, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" represents weight percentage, "parts" represents weight parts, and the ratio represents weight ratio.

[0072] Example 1

[0073] This example provides a preparation method of a composite solid electrolyte using carbon nitride fluoride as a filler, including the following steps:

[0074] Step 1, Weigh 10.0 g of dicyandiamide and 2.5 g of sodium fluoride according to parts by mass. Grind them in a mortar for 30 min. Transfer the ground dicyandiamide powder to a crucible and place it in a muffle furnace. Heat it at a rate of 5 °C / min -1 to 520 °C and keep it at this temperature for 3 h. Naturally cool it to room temperature. Wash it with water and perform suction filtration to remove water-soluble impurities. Obtain light yellow powder of fluorinated carbon nitride through freezing, drying, grinding, and sieving, denoted as g-C 3 N 4 , and the carbon nitride without fluorine is denoted as C 3 N 4 ;

[0075] Step 2, Weigh 0.5 g of fluorinated carbon nitride and dissolve it in a mixed solvent of 75.0 mL of ultrapure water and 150.0 mL of absolute ethanol. Place an ice pack around the beaker to keep the solution temperature not higher than 30 °C during ultrasonic treatment. Perform ultrasonic treatment for 120 min (ultrasonic for 1 s, interval for 2 s); Let the suspension after cell crushing stand for 24 h, and then freeze-dry the upper solution to obtain a powdery few-layer fluorinated carbon nitride sample, denoted as F-g-C 3 N 4 ;

[0076] Step 3, Add 36.0 g of tert-butyl mercaptan to 60.0 mL of ultrapure water and stir evenly to obtain a mixed solution; Drop 50% NaOH aqueous solution into the above mixed solution and stir well; Slowly add 20.0 mL of acetone to obtain a colorless transparent solution, stir for 0.5 h and cool to room temperature; Transfer the above reaction to an ice bath, add 34.0 g of carbon disulfide, 62.0 g of 2-bromopropionic acid, and 50% NaOH aqueous solution, control the reaction temperature not exceeding 60 °C, and remove the ice bath and continue the reaction at room temperature for 24 h after the reaction stops exotherming; After the reaction is completed, add 60.0 mL of concentrated hydrochloric acid and control the temperature to be less than 10 °C to obtain a yellow oil layer and stir until it solidifies, then wash it with a large amount of ultrapure water and vacuum dry it for 12 h to obtain a yellow solid, denoted as BCSPA;

[0077] Step 4, Slowly add 3.0 g of sodium hydride to 150.0 mL of dry and water-free tetrahydrofuran under nitrogen purging. Place it in an ice bath and add 23.63 g of polyethylene glycol monomethyl ether with a molecular weight of 750 and 10.82 g of 4-vinylbenzyl chloride to react for 12 h; Then perform rotary evaporation on it, add dichloromethane and ultrapure water for extraction and filtration to obtain a light yellow target product, denoted as VBMPEG 750 ;

[0078] Step 5, stir for 0.5 h under ice bath conditions, add 60.0 mL of thionyl chloride, 20.6 g of sodium 4-styrenesulfonate and 60.0 mL of anhydrous N,N'-dimethylformamide into the flask, stir for 0.5 h under ice bath conditions and continue to stir for 6 h at room temperature respectively. After completion, styrenesulfonyl chloride (SSC) is obtained through freezing, filtration and evaporation; add 10.2 g of fluorinated benzenesulfonamide, 0.6 g of 4-dimethylaminopyridine and 10.8 g of triethylamine reagent into anhydrous and oxygen-free acetonitrile, stir for 0.5 h under ice bath conditions. After the reaction is completed, add an appropriate amount of anhydrous magnesium sulfate to the above mixed solution, dry, filter and evaporate to remove dichloromethane to obtain a yellow viscous product; finally, dissolve it with anhydrous lithium hydroxide (20:19) in an appropriate amount of dichloromethane and stir at room temperature for 24 h to form a light yellow solution, marked as SSFPSILi, that is, fluorinated single-ion polymer lithium salt;

[0079] Step 6, by mass, blend 0.3 g of F-g-C 3 N 4 with 1.0 g of polyethylene oxide and add them into a round-bottom flask containing 25.0 mL of N,N'-dimethylformamide, where the solid content is 3% - 8% (the solid content here refers to the mass percentage of F-g-C 3 N 4 in polyethylene oxide), heat at 50 °C and stir for 1 h; then add the fluorinated single-ion polymer lithium salt. By mass, the ratio of polyethylene oxide to the fluorinated single-ion polymer lithium salt is 16:1, which can make the composite solid electrolyte have excellent conductivity. Continuously heat and stir for 10 h to completely dissolve and mix the mixture evenly. Finally, pour the above mixture into a polytetrafluoroethylene plate and dry it in a vacuum oven at 50 °C for 24 h to obtain the composite solid electrolyte.

[0080] Example 2

[0081] This example provides a preparation method of a composite solid electrolyte with fluorinated carbon nitride as a filler, including the following steps:

[0082] Step 1, by mass, weigh 10.0 g of dicyandiamide and 2.0 g of sodium fluoride, grind them in a mortar for 50 min, transfer the ground dicyandiamide powder to a crucible and place it in a muffle furnace, heat it at a rate of 5 °C / min -1 to 530 °C and hold at this temperature for 4 h, naturally cool to room temperature, wash with water and filter by suction to remove water-soluble impurities, and obtain light yellow powder fluorinated carbon nitride through freezing, drying, grinding and sieving, denoted as g-C 3 N 4 ;

[0083] Step 2: Weigh 0.6 g of fluorinated carbon nitride and dissolve it in a mixed solvent of 75.0 mL of ultrapure water and 150.0 mL of absolute ethanol. Place an ice pack around the beaker to keep the solution temperature not higher than 30 °C during ultrasonic treatment. Ultrasonically treat for 140 min (ultrasonic for 1 s, interval for 2 s); let the suspension after cell crushing stand for 28 h, and then freeze-dry the upper solution to obtain a powdery few-layer fluorinated carbon nitride sample, denoted as F-g-C 3 N 4 ;

[0084] Step 3: Add 36.0 g of tert-butyl mercaptan to 60.0 mL of ultrapure water and stir evenly to obtain a mixed solution; drop a 50% NaOH aqueous solution into the above mixed solution and stir well; slowly add 20.0 mL of acetone to obtain a colorless transparent solution, stir for 0.5 h and cool to room temperature; transfer the above reaction to an ice bath, add 34.0 g of carbon disulfide, 62.0 g of 2-bromopropionic acid and a 50% NaOH aqueous solution, control the reaction temperature not exceeding 60 °C, and remove the ice bath after the reaction stops exotherming and continue the reaction at room temperature for 24 h; after the reaction is completed, add 60.0 mL of concentrated hydrochloric acid and control the temperature below 10 °C to obtain a yellow oil layer and stir until it solidifies, then wash with a large amount of ultrapure water and vacuum dry for 12 h to obtain a yellow solid, denoted as BCSPA;

[0085] Step 4: Slowly add 3.0 g of sodium hydride to 150.0 mL of dry and water-free tetrahydrofuran under nitrogen purging, place it in an ice bath, add 23.63 g of polyethylene glycol monomethyl ether with a molecular weight of 750 and 10.82 g of 4-vinylbenzyl chloride and react for 12 h; then rotary evaporate it, add dichloromethane and ultrapure water for extraction and filtration to obtain a pale yellow target product, denoted as VBMPEG 750 ;

[0086] Step 5: Stir for 0.5 h in an ice bath, add 60.0 mL of thionyl chloride, 20.6 g of sodium 4-styrenesulfonate and 60.0 mL of anhydrous N,N'-dimethylformamide to the flask, stir for 0.5 h in an ice bath and continue to stir for 6 h at room temperature respectively. After completion, obtain styrenesulfonyl chloride (SSC) through freezing, filtration and evaporation; add 10.2 g of fluorinated benzenesulfonamide, 0.6 g of 4-dimethylaminopyridine and 10.8 g of triethylamine reagent to anhydrous and oxygen-free acetonitrile, stir for 0.5 h in an ice bath. After the reaction is completed, add an appropriate amount of anhydrous magnesium sulfate to the above mixed solution, dry, filter and evaporate to remove dichloromethane to obtain a yellow viscous product; finally, dissolve it with anhydrous lithium hydroxide (20:19) in an appropriate amount of dichloromethane and stir at room temperature for 24 h to form a pale yellow solution, marked as SSFPSILi, that is, fluorinated single-ion polymer lithium salt;

[0087] Step 6, by mass parts, take 0.5 g of F-g-C 3 N 4 and blend it with 1.0 g of polyethylene oxide, and add it to a round-bottom flask containing 25.0 mL of N,N'-dimethylformamide. The solid content is 3% to 8% (here, the solid content refers to the mass percentage of F-g-C 3 N 4 in polyethylene oxide). Heat at 50 °C and stir for 2 h. Then add a fluorinated single-ion polymer lithium salt. By mass parts, the ratio of polyethylene oxide to the fluorinated single-ion polymer lithium salt is 18:1, which can make the composite solid electrolyte have excellent conductivity. Continuously heat and stir for 12 h to completely dissolve and mix the mixture evenly. Finally, pour the above mixture into a polytetrafluoroethylene plate and dry it in a vacuum oven at 60 °C for 24 h to obtain the composite solid electrolyte.

[0088] Example 3

[0089] This example provides a preparation method of a composite solid electrolyte using carbon nitride fluoride as a filler, including the following steps:

[0090] Step 1, by mass parts, weigh 10.0 g of dicyandiamide and 1.6 g of sodium fluoride, grind them in a mortar for 30 min, transfer the ground dicyandiamide powder to a crucible and place it in a muffle furnace, and heat it at a rate of 5 °C / min -1 to 540 °C and hold at this temperature for 5 h, then naturally cool to room temperature, wash with water and filter by suction to remove water-soluble impurities, and obtain light yellow powder carbon nitride fluoride through freezing, drying, grinding and sieving, denoted as g-C 3 N 4 ;

[0091] Step 2, weigh 0.5 g of carbon nitride fluoride and dissolve it in a mixed solvent of 150.0 mL of ultrapure water and 150.0 mL of absolute ethanol. Place an ice pack around the beaker to keep the solution temperature not higher than 30 °C during ultrasonic treatment, and perform ultrasonic treatment for 120 min (ultrasonic for 1 s, interval for 2 s); let the suspension after cell crushing stand for 24 h, and then freeze-dry the upper layer solution to obtain a powdery few-layer carbon nitride fluoride sample, denoted as F-g-C 3 N 4 ;

[0092] Step 3: Add 36.0 g of tert-butyl mercaptan to 60.0 mL of ultrapure water and stir evenly to obtain a mixed solution; drop a 50% NaOH aqueous solution into the above mixed solution and stir well; slowly add 20.0 mL of acetone to obtain a colorless transparent solution, stir for 0.5 h and cool to room temperature; transfer the above reaction to an ice bath, add 34.0 g of carbon disulfide, 62.0 g of 2-bromopropionic acid and a 50% NaOH aqueous solution, control the reaction temperature not to exceed 60 °C, and after the reaction stops exotherming, remove the ice bath and continue the reaction at room temperature for 24 h; after the reaction is completed, add 60.0 mL of concentrated hydrochloric acid and control the temperature to be less than 10 °C to obtain a yellow oil layer and stir until solidified, then wash with a large amount of ultrapure water and vacuum dry for 12 h to obtain a yellow solid, denoted as BCSPA;

[0093] Step 4: Slowly add 3.0 g of sodium hydride to 150.0 mL of dry and water-free tetrahydrofuran under nitrogen purging, add 23.63 g of polyethylene glycol monomethyl ether with a molecular weight of 750 and 10.82 g of 4-vinylbenzyl chloride under ice bath conditions and react for 12 h; then rotary evaporate it, add dichloromethane and ultrapure water for extraction and filtration to obtain a pale yellow target product, denoted as VBMPEG 750 ;

[0094] Step 5: Stir for 0.5 h under ice bath conditions, add 60.0 mL of thionyl chloride, 20.6 g of sodium 4-styrenesulfonate and 60.0 mL of anhydrous N,N'-dimethylformamide to the flask, stir for 0.5 h under ice bath conditions and continue to stir for 6 h at room temperature respectively. After completion, obtain styrenesulfonyl chloride (SSC) through freezing, filtration and evaporation; add 10.2 g of fluorobenzenesulfonamide, 0.6 g of 4-dimethylaminopyridine and 10.8 g of triethylamine reagent to anhydrous and oxygen-free acetonitrile, stir for 0.5 h under ice bath conditions. After the reaction is completed, add an appropriate amount of anhydrous magnesium sulfate to the above mixed solution, dry, filter and evaporate to remove dichloromethane to obtain a yellow viscous product; finally, dissolve it with anhydrous lithium hydroxide (20:19) in an appropriate amount of dichloromethane and stir at room temperature for 24 h to form a pale yellow solution, marked as SSFPSILi, i.e., fluorinated single-ion polymer lithium salt;

[0095] Step 6: By mass fraction, blend 0.7 g of F-g-C 3 N 4 with 1.0 g of polyethylene oxide and add them to a round-bottom flask containing 25.0 mL of N,N'-dimethylformamide, where the solid content is 3% - 8% (the solid content here refers to F-g-C 3 N 4(percentage by mass of polyethylene oxide), heated at 50 °C and stirred for 1 h; subsequently, a fluorinated single-ion polymer lithium salt was added, wherein the ratio of polyethylene oxide to the fluorinated single-ion polymer lithium salt was 16:1 by mass, which could make the composite solid electrolyte have excellent conductivity. Continuously heat and stir for 14 h to completely dissolve and mix the mixture evenly. Finally, pour the above mixture into a polytetrafluoroethylene plate and dry it in a vacuum oven at 60 °C for 28 h to obtain the composite solid electrolyte.

[0096] In order to test the performance of the composite solid electrolyte prepared by the present invention, the following characterizations were carried out, wherein:

[0097] Figure 4 XRD spectra of the inorganic fillers prepared in Examples 1 to 3 of the present invention. As can be seen from the figure, C 3 N 4 The XRD spectrum shows two obvious characteristic peaks at 12.9° and 27.3°, which are the diffraction peaks generated by the in-plane stacking of the heptazine ring and the interlayer stacking of conjugated aromatic compounds respectively. The crystal planes they represent are the (100) crystal plane and the (002) crystal plane, indicating that g-C 3 N 4 has been successfully prepared. In the XRD spectrum of F-g-C 3 N 4 , with the use of NaF, both peaks become broader and gradually weaken, indicating that the introduction of F atoms can inhibit the aggregation of g-C 3 N 4 and improve its performance construction and dispersibility in the composite solid electrolyte. It is worth noting that the peak at 2θ = 12.9° corresponding to the (100) crystal plane almost disappears, which should be due to the reaction of NaF with g-C 3 N 4 (or its molecular precursor) during the thermal polymerization process, resulting in the loss of the ordered structure within the framework. In addition, due to the doping of F atoms, the lattice constant of F-g-C 3 N 4 becomes smaller, resulting in the diffraction peak attributed to the (002) crystal plane shifting slightly to the right to 2θ = 27.6°. The changes in the intensity and position of the above diffraction peaks prove the successful preparation of F-g-C 3 N 4 .

[0098] Figure 5 Transmission diagrams of the composite solid electrolytes prepared in Examples 1 to 3 of the present invention. As can be seen from the figure, Figures a and d are g-C 3 N 4 and F-g-C 3 N 4 respectively. It can be seen from the figure that the black area is the area where the electron beam is difficult to penetrate, and the area where the electron beam can penetrate is the light gray area. Compared with g-C3 N 4 has relatively fewer black regions, demonstrating that the F-g-C 3 N 4 nanosheets are thinner. Further magnifying the resolution, the results are shown in Figures b and d. It can be clearly seen from Figure b that there are few-layer g-C 3 N 4 nanosheet structures, and the positions with more sheets are darker in color, which is consistent with the analysis in the previous text. From Figure d, it can be seen that the F-g-C 3 N 4 nanosheets have a uniform color distribution and basically show a single-layer structure. In addition, from Figures b and d, it can be seen that neither g-C 3 N 4 nor F-g-C 3 N 4 and F-g-C 3 N 4 samples show obvious lattice fringes, proving that the samples are all amorphous, which is consistent with the reports in the literature. To further explore the effect of F doping on the lattice structure of the samples, selected area electron diffraction (SAED) was taken for g-C 3 N 4 and F-g-C 3 N 4 respectively, as shown in Figures c and f. It can be more clearly observed from Figure c the diffraction rings belonging to the (100) and (002) crystal planes of g-C 3 N 4 . However, in Figure f, the intensities of the two diffraction rings are weakened to varying degrees, proving that the introduction of F element has damaged the lattice structure to a certain extent, which is consistent with the previous XRD analysis. Combining the morphological analysis of the transmission, it can be inferred that few-layer ultrathin g-C 3 N 4 and F-g-C 3 N 4 nanosheet samples have been successfully prepared by ultrasonic exfoliation method.

[0099] Figure 6 This is the electrochemical window of the composite solid electrolytes prepared in Examples 1 to 3 of the present invention at 25°C. The electrochemical stability of the solid electrolyte was studied by linear sweep voltammetry (LSV). Since the addition of F-g-C 3 N 4 helps to prevent the reaction between the end groups of PEO in the polymer matrix and lithium metal, the electrochemical stability window of the polymer electrolyte film increases to 4.7 V (vs. Li / Li 3 N 4 ) after the addition of F-g-C + ). The electrochemical stability window of the g-5PFT composite polymer electrolyte is 4.6 V (vs. Li / Li+ ), this is due to gC 3 N 4 The dispersibility in the polymer matrix is ​​poor, which weakens the protective effect on PEO to a certain extent.

[0100] Example 4

[0101] This embodiment provides a method for preparing a composite solid electrolyte using fluorinated carbon nitride as a filler, comprising the following steps:

[0102] Step 1: Weigh 4 parts of dicyandiamide and 1 part of sodium fluoride by weight, grind them in a mortar for 30 minutes, transfer the ground dicyandiamide powder to a crucible and place it in a muffle furnace at 5°C min. -1 The temperature was raised to 520°C at a rate of 1.50 °C and kept at this temperature for 3 h, then naturally cooled to room temperature, washed with water and filtered to remove water-soluble impurities, and then light yellow powdered carbon nitride fluoride was obtained by freezing, drying, grinding and sieving, recorded as gC 3 N 4 ;

[0103] Step 2, weighing 0.5 g of fluorinated carbon nitride and dissolving it in a mixed solvent of 75.0 mL of ultrapure water and 150.0 mL of anhydrous ethanol, placing an ice bag outside the beaker to keep the solution temperature below 30° C. during the ultrasonic process, and ultrasonic treatment for 120 min (ultrasound for 1 s, interval of 2 s); after the cell suspension was allowed to stand for 24 h, the upper layer solution was freeze-dried to obtain a powdered few-layer fluorinated carbon nitride sample, recorded as FgC 3 N 4 ;

[0104] Step 3, according to the mass fraction, 3 parts of tert-butyl mercaptan are added to 5 parts of ultrapure water and stirred evenly to obtain a mixed solution; a 45% mass fraction NaOH aqueous solution is dropped into the above mixed solution and fully stirred, and the system is stirred to make the pH value of the system 10; 40.0 mL of acetone is slowly added to obtain a colorless transparent solution, and the solution is stirred for 0.8 h and cooled to room temperature; the above reaction is transferred to an ice bath, 3 parts of carbon disulfide, 5 parts of 2-bromopropionic acid and a 45% mass fraction NaOH aqueous solution are added, and the reaction temperature is controlled not to exceed 60° C. After the reaction stops exothermic, the ice bath is removed and the reaction is continued at room temperature for 35 h; after the reaction is completed, 5 parts of concentrated hydrochloric acid are added and the temperature is controlled to be less than 10° C. to obtain a yellow oil layer and stir until solidified, wash with a large amount of ultrapure water, and vacuum dry for 13 h to obtain a yellow solid to obtain the target product, i.e., intermediate product A;

[0105] Step 4: Slowly add 3 parts of sodium hydride to 10 parts of dry and water - removed tetrahydrofuran under nitrogen purging. Place it in an ice bath and add 2 parts of polyethylene glycol monomethyl ether with a molecular weight of 750 and 1 part of 4 - vinylbenzyl chloride, and react for 13 h. Then perform rotary evaporation on it, add dichloromethane and ultrapure water for extraction and filtration to obtain a pale - yellow target product, denoted as VBMPEG 750 , which is intermediate B;

[0106] Step 5: Add 5 parts of thionyl chloride, 2 parts of sodium 4 - styrenesulfonate, and 6 parts of anhydrous N,N’ - dimethylformamide into a flask. Stir successively for 3 h under ice - bath conditions and 8 h at room temperature. After completion, obtain styrenesulfonyl chloride through freezing, filtration, and evaporation. Add 16 parts of styrenesulfonyl chloride, 17 parts of fluorinated benzenesulfonamide, 1 part of 4 - dimethylaminopyridine, and 18 parts of triethylamine into anhydrous and anaerobic acetonitrile, stir for 2 h under ice - bath conditions. After the reaction is completed, add an appropriate amount of anhydrous magnesium sulfate to the above - mentioned mixed solution, dry, filter, and evaporate to remove dichloromethane to obtain a yellow viscous product. Finally, dissolve the product and anhydrous lithium hydroxide (mass ratio is 20:15) in an appropriate amount of dichloromethane, stir at room temperature for 30 h to form a pale - yellow solution, that is, obtain the target product, namely fluorinated single - ion polymer lithium salt;

[0107] Step 6: By mass, blend 3 parts of F - g - C 3 N 4 with 10 parts of polyethylene oxide, add them into a round - bottom flask containing 25.0 mL of N,N’ - dimethylformamide, where the solid content is 3% - 8% (here the solid content refers to the mass percentage of F - g - C 3 N 4 in polyethylene oxide), heat at 50 °C and stir for 1 h. Then add the fluorinated single - ion polymer lithium salt. By mass, the ratio of polyethylene oxide to the fluorinated single - ion polymer lithium salt is 16:1, which can make the composite solid electrolyte have excellent conductivity. Continuously heat and stir for 10 h to completely dissolve and mix the mixture evenly. Finally, pour the above - mentioned mixture into a polytetrafluoroethylene plate and dry it in a vacuum oven at 50 °C for 24 h to obtain the composite solid electrolyte.

[0108] Example 5

[0109] This example provides a preparation method of a composite solid electrolyte using carbon nitride fluoride as a filler, including the following steps:

[0110] Step 1: By mass, weigh 5 parts of dicyandiamide and 1 part of sodium fluoride, grind them in a mortar for 50 min. Transfer the ground dicyandiamide powder to a crucible and place it in a muffle furnace, at a rate of 5 °C / min -1Heat it at a rate to 530 °C and hold at this temperature for 4 h, then cool it naturally to room temperature, wash it with water and filter it by suction to remove water-soluble impurities. Obtain light yellow powder of carbon nitride fluoride through freezing, drying, grinding and sieving, denoted as g-C 3 N 4 ;

[0111] Step 2: Weigh 0.6 g of carbon nitride fluoride and dissolve it in a mixed solvent of 75.0 mL of ultrapure water and 150.0 mL of absolute ethanol. Place an ice bag around the beaker to keep the solution temperature not higher than 30 °C during ultrasonic treatment, and perform ultrasonic treatment for 140 min (ultrasonic for 1 s, interval for 2 s); Let the suspension after cell crushing stand for 28 h, then freeze-dry the upper solution to obtain a powdery few-layer carbon nitride fluoride sample, denoted as F-g-C 3 N 4 ;

[0112] Step 3: According to the mass parts, add 3 parts of tert-butyl mercaptan to 5 parts of ultrapure water and stir evenly to obtain a mixed solution; Drop the NaOH aqueous solution with a mass fraction of 45% into the above mixed solution and stir well, stir the system to make the pH value of the system 10; Slowly add 40.0 mL of acetone to obtain a colorless transparent solution, stir for 0.8 h and cool to room temperature; Transfer the above reaction to an ice bath, add 3 parts of carbon disulfide, 5 parts of 2-bromopropionic acid and the NaOH aqueous solution with a mass fraction of 45%, control the reaction temperature not exceeding 60 °C, and remove the ice bath and continue the reaction at room temperature for 35 h after the reaction stops releasing heat; After the reaction is completed, add 5 parts of concentrated hydrochloric acid and control the temperature less than 10 °C, obtain a yellow oil layer and stir until it solidifies, wash it with a large amount of ultrapure water, and vacuum dry it for 13 h to obtain a yellow solid, to obtain the target product, that is, intermediate A;

[0113] Step 4: Slowly add 3 parts of sodium hydride to 10 parts of dry and water-free tetrahydrofuran under the condition of nitrogen purging, add 2 parts of polyethylene glycol monomethyl ether with a molecular weight of 750 and 1 part of 4-vinylbenzyl chloride under the ice bath condition and react for 13 h; Then perform rotary evaporation on it, add dichloromethane and ultrapure water for extraction and filtration to obtain a light yellow target product, denoted as VBMPEG 750 , that is, intermediate B;

[0114] Step 5: Add 5 parts of thionyl chloride, 2 parts of sodium 4-styrenesulfonate, and 6 parts of anhydrous N,N'-dimethylformamide into a flask, stir for 3 h under ice bath conditions and then for 8 h at room temperature in sequence. After completion, obtain styrenesulfonyl chloride through freezing, filtration, and evaporation. Add 17 parts of styrenesulfonyl chloride, 18 parts of fluorobenzene sulfonamide, 1 part of 4-dimethylaminopyridine, and 18 parts of triethylamine into anhydrous and oxygen-free acetonitrile, stir for 2 h under ice bath conditions. After the reaction ends, add an appropriate amount of anhydrous magnesium sulfate to the above mixed solution, dry, filter, and evaporate to remove dichloromethane to obtain a yellow viscous product. Finally, dissolve the product and anhydrous lithium hydroxide (mass fraction ratio is 20:15) in an appropriate amount of dichloromethane, stir at room temperature for 30 h to form a light yellow solution, namely the target product, i.e., fluorine-containing single-ion polymer lithium salt;

[0115] Step 6: Blend 5 parts of F-g-C 3 N 4 with 10 parts of polyethylene oxide, add them into a round-bottom flask containing 25.0 mL of N,N'-dimethylformamide, where the solid content is 3% - 8% (here the solid content refers to the mass percentage of F-g-C 3 N 4 in polyethylene oxide), heat at 50 °C, and stir for 2 h; then add the fluorine-containing single-ion polymer lithium salt, where the mass ratio of polyethylene oxide to the fluorine-containing single-ion polymer lithium salt is 18:1 by mass, which can make the composite solid electrolyte have excellent conductivity. Continuously heat and stir for 12 h to completely dissolve and mix the mixture evenly. Finally, pour the above mixture into a polytetrafluoroethylene plate and dry it in a vacuum oven at 60 °C for 24 h to obtain the composite solid electrolyte.

[0116] Example 6

[0117] This example provides a preparation method of a composite solid electrolyte with carbon nitride fluoride as a filler, including the following steps:

[0118] Step 1: Weigh 6 parts of dicyandiamide and 1 part of sodium fluoride by mass, grind them in a mortar for 30 min, transfer the ground dicyandiamide powder to a crucible and place it in a muffle furnace, heat it at a rate of 5 °C / min -1 to 540 °C and hold at this temperature for 5 h, naturally cool to room temperature, wash with water and filter by suction to remove water-soluble impurities, and obtain light yellow powder carbon nitride fluoride through freezing, drying, grinding, and sieving, denoted as g-C 3 N 4 ;

[0119] Step 2: Weigh 0.5 g of fluorinated carbon nitride and dissolve it in a mixed solvent of 150.0 mL of ultrapure water and 150.0 mL of absolute ethanol. Place an ice bag around the beaker to keep the solution temperature no higher than 30 °C during ultrasonic treatment. Ultrasonically treat for 120 min (ultrasonic for 1 s, interval for 2 s); let the suspension after cell crushing stand for 24 h, and then freeze-dry the upper solution to obtain a powdery few-layer fluorinated carbon nitride sample, denoted as F-g-C 3 N 4 ;

[0120] Step 3: According to the mass fraction, add 3 parts of tert-butyl mercaptan to 5 parts of ultrapure water and stir evenly to obtain a mixed solution; drop a 45% NaOH aqueous solution into the above mixed solution and stir well, stir the system to make the pH value of the system 10; slowly add 40.0 mL of acetone to obtain a colorless transparent solution, stir for 0.8 h and cool to room temperature; transfer the above reaction to an ice bath, add 3 parts of carbon disulfide, 5 parts of 2-bromopropionic acid and a 45% NaOH aqueous solution, control the reaction temperature not to exceed 60 °C, and remove the ice bath after the reaction stops exotherming and continue the reaction at room temperature for 35 h; after the reaction is completed, add 5 parts of concentrated hydrochloric acid and control the temperature to be less than 10 °C, obtain a yellow oil layer and stir until solidified, wash with a large amount of ultrapure water, and vacuum dry for 13 h to obtain a yellow solid, which is the target product, that is, intermediate A;

[0121] Step 4: Slowly add 3 parts of sodium hydride to 10 parts of dry and water-free tetrahydrofuran under nitrogen purge, add 2 parts of polyethylene glycol monomethyl ether with a molecular weight of 750 and 1 part of 4-vinylbenzyl chloride under ice bath conditions and react for 13 h; then rotary evaporate it, add dichloromethane and ultrapure water for extraction and filtration to obtain a pale yellow target product, denoted as VBMPEG 750 , that is, intermediate B;

[0122] Step 5: Add 5 parts of thionyl chloride, 2 parts of sodium 4-styrenesulfonate and 6 parts of anhydrous N,N'-dimethylformamide to the flask, stir for 3 h under ice bath conditions and 8 h at room temperature in sequence. After completion, obtain styrenesulfonyl chloride through freezing, filtration and evaporation; add 17 parts of styrenesulfonyl chloride, 18 parts of fluorinated benzenesulfonamide, 1 part of 4-dimethylaminopyridine and 18 parts of triethylamine to anhydrous and oxygen-free acetonitrile, and stir for 2 h under ice bath conditions. After the reaction is completed, add an appropriate amount of anhydrous magnesium sulfate to the above mixed solution, dry, filter and evaporate to remove dichloromethane to obtain a yellow viscous product. Finally, dissolve the product and anhydrous lithium hydroxide (mass fraction ratio of 20:15) in an appropriate amount of dichloromethane and stir at room temperature for 30 h to form a pale yellow solution, which is the target product, that is, fluorinated single-ion polymer lithium salt;

[0123] Step 6: According to the mass fraction, add 7 parts of F-g-C 3 N4 Blended with 10 parts of polyethylene oxide and added into a round-bottom flask containing 25.0 mL of N,N’-dimethylformamide, with a solid content of 3% to 8% (the solid content here refers to the mass percentage of F-g-C 3 N 4 in polyethylene oxide), heated at 50 °C and stirred for 1 h; subsequently, a fluorinated single-ion polymer lithium salt was added. By mass fraction, the ratio of polyethylene oxide to the fluorinated single-ion polymer lithium salt was 16:1, which can endow the composite solid electrolyte with excellent conductivity. Continuously heat and stir for 14 h to completely dissolve and mix the mixture evenly. Finally, pour the above mixture into a polytetrafluoroethylene plate and dry it in a vacuum oven at 60 °C for 28 h to obtain the composite solid electrolyte.

[0124] The above content is only to illustrate the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a composite solid electrolyte with fluorinated carbon nitride as filler, characterized in that: The following steps are involved: S1, mixing dicyandiamide and sodium fluoride and grinding them, transferring the ground dicyandiamide powder to a crucible and placing it in a muffle furnace, heating and keeping it warm for carbonization treatment, and obtaining a light yellow powder target product, fluorinated carbon nitride; S2, mixing the fluorinated carbon nitride with ultrapure water and anhydrous ethanol, peeling with a cell crusher, and letting the suspension after the cell crushing stand to obtain a powdered few-layer fluorinated carbon nitride sample; S3, under ice bath conditions, carbon disulfide and 2-bromopropionic acid are added to tert-butyl mercaptan to obtain an intermediate product A after reaction. The structural formula of the intermediate product A is as follows: In an ice bath and under nitrogen protection, polyethylene glycol monomethyl ether and 4-vinylbenzyl chloride were reacted to obtain an intermediate product B, the structural formula of which is as follows: Styrenesulfonyl chloride is added to anhydrous oxygen-free acetonitrile, and fluorine-containing benzenesulfonamide, 4-dimethylaminopyridine and triethylamine are added, and the mixture is stirred under ice bath conditions. After the reaction is completed, the reaction product is reacted with anhydrous lithium hydroxide to obtain a fluorine-containing single ion lithium salt. The structural formula of the fluorine-containing single ion lithium salt is as follows: S4, adding the fluorine-containing single ion lithium salt, polyethylene oxide and fluorinated carbon nitride into N,N'-dimethylformamide, continuously heating and stirring until completely dissolved and dried, to obtain a composite solid electrolyte.

2. The method for preparing a composite solid electrolyte with fluorinated carbon nitride as filler according to claim 1, characterized in that: In terms of weight, the ratio of dicyandiamide to sodium fluoride is 4:1 to 8:

1.

3. The method for preparing a composite solid electrolyte with fluorinated carbon nitride as filler according to claim 1, characterized in that: The muffle furnace is heated at 5-10°C min -1 The temperature is raised to 520-550°C at a rate of 1000 ℃ and kept at this temperature for 3-5 hours, and then naturally cooled to room temperature to complete the carbonization process.

4. The method for preparing a composite solid electrolyte with fluorinated carbon nitride as filler according to claim 1, characterized in that: In terms of mass fractions, the ratio of tert-butyl mercaptan, carbon disulfide and 2-bromopropionic acid is 3:(1-10):(5-15).

5. The method for preparing a composite solid electrolyte with fluorinated carbon nitride as filler according to claim 1, characterized in that: In terms of mass fractions, the ratio of the polyethylene glycol monomethyl ether to 4-vinylbenzyl chloride is (2-5):(1-3).

6. The method for preparing a composite solid electrolyte with fluorinated carbon nitride as filler according to claim 1, characterized in that: In terms of mass fractions, the ratio of styrenesulfonyl chloride to 4-fluorobenzenesulfonamide is (14-20):(8-10).

7. The method for preparing a composite solid electrolyte with fluorinated carbon nitride as filler according to claim 1, characterized in that: In terms of mass fractions, the ratio of the fluorinated carbon nitride to polyethylene oxide is (2-8):(8-12); the ratio of the fluorinated single ion polymer lithium salt to polyethylene oxide is (16-20):

1.

8. The method for preparing a composite solid electrolyte with fluorinated carbon nitride as filler according to claim 1, characterized in that: In S4, the temperature for continuous heating and stirring is 50 to 80° C., and the time is 10 to 16 hours.

9. A composite solid electrolyte with fluorinated carbon nitride as filler, prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the composite solid electrolyte with fluorinated carbon nitride as filler according to claim 9 in lithium metal batteries.

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