Ultrathin polymer solid electrolyte membrane and its preparation method and application

Abstract

The present invention discloses an ultrathin polymer solid electrolyte membrane, its preparation method, and application, belonging to the field of solid-state lithium batteries. The raw materials of the ultrathin polymer solid electrolyte membrane include: a mixture of a two-arm crosslinker, allylboronic acid pinacol ester, a fluorinated electrolyte, and a photoinitiator; and a boron nitride composite polymer membrane prepared by electrospinning; the fluorinated electrolyte includes a lithium salt, tetraethylene glycol dimethyl ether, and a fluorinated plasticizer, wherein the fluorinated plasticizer is selected from at least one of #imgabs0#, #imgabs1#, and #imgabs2#, where n is an integer from 1 to 10. The preparation method comprises: mixing the two-arm crosslinker, allylboronic acid pinacol ester, the fluorinated electrolyte, and the photoinitiator, coating the mixture on the surface of the boron nitride composite polymer membrane, and performing photoinitiated polymerization. The ultrathin polymer solid electrolyte membrane of the present invention has high ionic conductivity, a high lithium ion transference number, and high oxidative stability, and is compatible with high-voltage positive electrode materials to achieve excellent electrochemical performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid-state lithium batteries, and in particular relates to an ultra-thin polymer solid electrolyte membrane and a preparation method and application thereof. Background Art

[0002] Lithium metal has a high theoretical specific capacity (3860 mAh g -1 ), is considered a promising anode material. However, the continuous reaction between conventional commercial electrolytes and lithium metal leads to continuous consumption of both the lithium metal and the electrolyte, resulting in reduced capacity and a shortened cycle life. Furthermore, uneven lithium deposition on the lithium metal surface in commercial electrolytes can lead to the growth of lithium dendrites, ultimately causing a battery short circuit.

[0003] Compared to traditional organic electrolytes, solid-state electrolytes are generally considered to offer superior safety and stability. Among them, polymer solid electrolytes hold promise for large-scale industrial application due to their excellent flexibility, low interfacial impedance, and ease of processing. However, most reported solid polymer electrolytes exhibit dual ion conduction, meaning both lithium ions and anions can move freely. Due to the coordination between lithium ions and the Lewis basic sites of the polymer chains, lithium ions migrate much more slowly than anions, resulting in a lithium-ion transference number (LITN) typically below 0.5. Excessive anion accumulation on the cathode surface can lead to concentration polarization within the battery, resulting in a large overpotential that not only easily promotes lithium dendrite growth but also limits the energy and power density of lithium-ion batteries. Improving the LiTN of solid polymer electrolytes is a key challenge in improving solid-state battery performance. Furthermore, research has shown that electrolyte thickness significantly influences battery energy density, with thinner solid electrolytes facilitating higher gravimetric and volumetric energy densities. However, thinning the electrolyte membrane inevitably reduces its mechanical strength, increasing the risk of membrane rupture and Li dendrite penetration, leading to increased battery failure and safety risks. Therefore, preparing ultra-thin solid electrolytes is an effective means to improve the energy density of solid-state batteries by resolving the contradiction between thickness and mechanical strength.

[0004] To address the above problems, it is necessary to develop a solid polymer electrolyte that combines single-ion conduction and ultra-thin thickness. Summary of the Invention

[0005] To address the issues raised in the aforementioned background art, the present invention provides an ultrathin polymer solid electrolyte membrane, a method for preparing the membrane, and its application. The ultrathin polymer solid electrolyte membrane provided by the present invention has a membrane thickness between 20 and 30 microns, can achieve single-ion conduction, and exhibits high ionic conductivity, a high lithium ion transference number, and high oxidative stability. Furthermore, it can be used with high-voltage cathode materials to achieve excellent electrochemical performance.

[0006] In order to achieve the above-mentioned object, the technical solution adopted by the present invention is as follows: on the one hand, the present invention provides an ultra-thin polymer solid electrolyte membrane, the raw materials of which include: a mixture of a dual-arm crosslinking agent, allylboronic acid pinacol ester, a fluorinated electrolyte, and a photoinitiator, and a polymer membrane of composite boron nitride prepared by electrospinning;

[0007] The fluorinated electrolyte comprises a lithium salt, tetraethylene glycol dimethyl ether and a fluorinated plasticizer, wherein the fluorinated plasticizer is selected from at least one of the compounds shown in Formula 1, Formula 2 and Formula 3.

[0008]

[0009] Formula 1

[0010]

[0011] Formula 2

[0012]

[0013] Formula 3

[0014] In Formula 1 to Formula 3, n is an integer of 1-10.

[0015] Furthermore, the thickness of the ultra-thin polymer solid electrolyte membrane is 20-30 microns, and the thickness of the composite boron nitride polymer membrane is 5-15 microns.

[0016] Furthermore, the mass ratio of the two-arm cross-linking agent, allyl boric acid pinacol ester, lithium salt, tetraethylene glycol dimethyl ether, and fluorinated modified plasticizer is (5-10):(10-20):(40-45):(25-35):(4-10), and the amount of the photoinitiator added is 1%-5% of the total mass of the two-arm cross-linking agent and the allyl boric acid pinacol ester;

[0017] The mass ratio of boron nitride to polymer used in the preparation of the composite boron nitride polymer film using an electrospinning method is (0.2~2):15.

[0018] Further, the double-arm cross-linking agent is selected from polyethylene glycol dimethacrylate or N,N-methylenebis(acrylamide);

[0019] The molecular weight of the polyethylene glycol dimethacrylate is 200 g / mol to 600 g / mol.

[0020] Furthermore, the photoinitiator is selected from at least one of 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone, and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide.

[0021] Furthermore, the polymer used in the polymer film of the composite boron nitride is at least one selected from polyacrylonitrile, polypropylene carbonate, polyethyleneimine, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride, and polymethyl methacrylate;

[0022] The boron nitride used in the composite boron nitride polymer film is hexagonal boron nitride nanosheets, and the boron nitride sheet diameter is 80 nm to 100 nm.

[0023] Furthermore, the lithium salt is selected from at least one of lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium difluorooxalatoborate.

[0024] On the other hand, the present invention provides a method for preparing any of the above-mentioned ultrathin polymer solid electrolyte membranes, characterized in that it comprises the following steps:

[0025] S1: dissolving a polymer in a solvent to form a polymer solution, then uniformly dispersing boron nitride nanosheets in the polymer solution, obtaining a nanofiber membrane by electrospinning, and then drying and hot rolling to obtain a boron nitride composite polymer membrane;

[0026] S2: mixing a double-arm crosslinking agent, allylboronic acid pinacol ester, a fluorinated electrolyte, and a photoinitiator to obtain a polymerization precursor solution;

[0027] S3: coating the polymerization precursor solution described in S2 on the surface of the polymer film of the composite boron nitride described in S1, and then performing photoinitiated polymerization to prepare an ultrathin polymer solid electrolyte membrane;

[0028] or

[0029] S1: mixing a double-arm crosslinking agent, allyl boric acid pinacol ester, a fluorinated electrolyte, and a photoinitiator to obtain a polymerization precursor solution;

[0030] S2: dissolving a polymer in a solvent to form a polymer solution, then uniformly dispersing boron nitride nanosheets in the polymer solution, obtaining a nanofiber membrane by electrospinning, and then drying and hot rolling to obtain a boron nitride composite polymer membrane;

[0031] S3: coating the polymerization precursor solution described in S1 on the surface of the polymer film of the composite boron nitride described in S2, and then performing photoinitiated polymerization to prepare an ultrathin polymer solid electrolyte.

[0032] Furthermore, the solvent includes one of N,N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, and acetone.

[0033] In another aspect, the present invention provides a use of any of the above-mentioned ultrathin polymer solid electrolyte membranes in a lithium battery.

[0034] In another aspect, the present invention provides a lithium battery comprising any of the above-mentioned ultra-thin polymer solid electrolyte membranes.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] The fluorinated plasticizer molecules used in the ultrathin polymer solid electrolyte membrane of this invention effectively improve lithium ion transport kinetics and electrolyte stability for high-voltage cathodes. Boron nitride also binds anions through Lewis acid-base interactions, enabling single lithium ion transport. The ultrathin polymer solid electrolyte membrane of this invention exhibits high ionic conductivity, a high lithium ion transference number, and high oxidative stability, while also being compatible with high-voltage cathode materials to achieve excellent electrochemical performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a scanning electron microscope image of the ultrathin polymer solid electrolyte membrane prepared in Example 1 of the present invention;

[0038] Figure 2 This is a digital photo of the thickness of the ultra-thin polymer solid electrolyte membrane prepared in Example 1 of the present invention;

[0039] Figure 3 This is a graph of the ionic conductivity of the ultrathin polymer solid electrolyte membrane prepared in Example 1 of the present invention;

[0040] Figure 4 This is a linear sweep voltammogram of the ultrathin polymer solid electrolyte membrane prepared in Example 1 of the present invention;

[0041] Figure 5 This is a graph showing the lithium ion transference number test results of the ultra-thin polymer solid electrolyte membrane prepared in Example 1 of the present invention;

[0042] Figure 6 This is a cycling performance diagram of a symmetrical battery using the ultrathin polymer solid electrolyte membrane prepared in Example 1 of the present invention and lithium metal as electrodes on both sides;

[0043] Figure 7This is a cycle performance diagram of a battery using the ultra-thin polymer solid electrolyte membrane prepared in Example 1 of the present invention, lithium iron phosphate as the positive electrode, and lithium metal as the negative electrode;

[0044] Figure 8 This is a cycle performance diagram of a battery using the ultra-thin polymer solid electrolyte membrane prepared in Example 1 of the present invention, lithium nickel cobalt manganese oxide NCM811 as the positive electrode, and lithium metal as the negative electrode;

[0045] Figure 9 This is a cycle performance diagram of a battery using the ultrathin polymer solid electrolyte membrane prepared in Example 2 of the present invention, lithium nickel cobalt manganese oxide NCM811 as the positive electrode, and lithium metal as the negative electrode;

[0046] Figure 10 This is a cycle performance diagram of a battery using the ultra-thin polymer solid electrolyte membrane prepared in Comparative Example 1 of the present invention, lithium nickel cobalt manganese oxide NCM811 as the positive electrode, and lithium metal as the negative electrode;

[0047] Figure 11 This is a cycle performance diagram of a battery using the ultra-thin polymer solid electrolyte membrane prepared in Comparative Example 2 of the present invention, lithium nickel cobalt manganese oxide NCM811 as the positive electrode and lithium metal as the negative electrode. DETAILED DESCRIPTION

[0048] In order to better understand the content of the present invention, the content of the present invention is further described below in conjunction with specific implementation methods, but the protection content of the present invention is not limited to the following embodiments.

[0049] In the present invention, all equipment and raw materials can be purchased from the market or are commonly used in the industry.

[0050] Example 1

[0051] Ultrathin polymer solid electrolyte membrane: its raw materials include N,N-methylenebis(acrylamide), allylboronic acid pinacol ester, fluorinated electrolyte, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and a polymer membrane of composite boron nitride prepared by electrospinning; the fluorinated electrolyte includes lithium bis(trifluoromethylsulfonyl)imide, lithium difluorooxalatoborate, tetraethylene glycol dimethyl ether, and the compound shown in formula 1 (n is 4); the boron nitride used in the composite boron nitride polymer film is hexagonal boron nitride nanosheets, and the polymer is polyacrylonitrile.

[0052] The preparation method of the ultrathin polymer solid electrolyte membrane is as follows:

[0053] (1) Synthesis of fluorinated modified plasticizer molecules: Under argon protection, tetraethylene glycol monomethyl ether was weighed into a flask, and a certain amount of anhydrous dichloromethane was added for argon protection. The system was placed in an ice-water bath, and 2.5 molar equivalents of ultra-dry pyridine were added dropwise at 0°C. After the addition was completed, stirring was continued for 10 minutes. Then, 2.5 molar equivalents of trifluoroacetic anhydride were added dropwise at 0°C. After the addition was completed, the mixture was returned to room temperature and reacted for 2 hours. After the reaction was completed, saturated sodium bicarbonate aqueous solution was added dropwise at 0°C to quench the reaction. After separation, the mixture was extracted with dichloromethane. The resulting organic phase was washed once with 1 mol / L hydrochloric acid and once with sodium chloride aqueous solution, and then dried. The solvent was removed by rotary evaporation to obtain the compound shown in Formula 1. , n is 4.

[0054] (2) Preparation of composite boron nitride polymer membrane: 1.5 g of polyacrylonitrile was dissolved in 8.5 g of N,N-dimethylformamide solvent, and then 0.05 g of hexagonal boron nitride nanosheets was added and stirred at room temperature for 6 hours to obtain a uniformly dispersed electrospinning precursor solution; the precursor solution was spun into a nanofiber membrane under the spinning conditions of an electrostatic voltage of 15 kV, a spinning distance of 15 cm, a spinning solution flow rate of 0.5 mL / h, and a receiving tube speed of 1000 rpm, and then vacuum dried at 80°C for 24 hours and hot rolled at 60°C to obtain a composite boron nitride polymer membrane with a membrane thickness of 10 μm.

[0055] (3) Preparation of ultrathin polymer solid electrolyte membrane: 0.96 g of lithium bis(trifluoromethylsulfonyl)imide, 0.12 g of lithium difluorooxalatoborate, 0.72 g of tetraethylene glycol dimethyl ether and 0.20 g of the compound shown in Formula 1 were prepared into a fluorinated electrolyte; 0.01 g of N,N-methylenebis(acrylamide), 0.03 g of allylboronic acid pinacol ester, 0.16 g of the fluorinated electrolyte and 1.2 mg of 2-hydroxy-2-methyl-1-phenyl-1-propanone were mixed to obtain a polymerization precursor solution; a polymer film of composite boron nitride was placed on a glass plate, a layer of polymerization precursor solution was scraped on the surface of the glass plate, and then the film was irradiated under ultraviolet light for 10 minutes for photoinitiated polymerization to prepare an ultrathin polymer solid electrolyte membrane.

[0056] The prepared ultra-thin polymer solid electrolyte membrane was scanned by electron microscope, and the results were as follows: Figure 1 As shown, from Figure 1 It can be seen under the scanning electron microscope that the ultra-thin polymer solid electrolyte membrane was successfully prepared. The thickness of the prepared ultra-thin polymer solid electrolyte membrane was tested, and the results are as follows Figure 2 As shown, from Figure 2It can be seen that the thickness is 21 μm. A thinner electrolyte membrane thickness is more conducive to achieving a higher energy density. The ionic conductivity of the prepared ultra-thin polymer solid electrolyte membrane was calculated by electrochemical impedance spectroscopy test. The results are as follows Figure 3 As shown, from Figure 3 It can be seen that the ultrathin polymer solid electrolyte membrane exhibits a 1.9×10 -3 S cm -1 The high ionic conductivity can satisfy the battery to achieve good charge and discharge capacity. The prepared ultra-thin polymer solid electrolyte membrane was tested by linear sweep voltammetry. The results are as follows Figure 4 As shown, from Figure 4 It can be seen that the oxidation stability potential of the ultra-thin polymer solid electrolyte membrane can reach 5.3 V, which can be used with a positive electrode with a high working potential (such as lithium nickel cobalt manganese oxide NCM811). The prepared ultra-thin polymer solid electrolyte membrane was tested and calculated by time / current test and impedance test before and after polarization. The results are as follows Figure 5 As shown, from Figure 5 It can be seen that the ultra-thin polymer solid electrolyte membrane exhibits a high lithium ion migration number of 0.77, indicating that the electrolyte effectively realizes the binding effect of anions, achieves the effect of single ion transport and suppresses concentration polarization, and helps the battery achieve high rate performance.

[0057] A symmetrical battery with lithium metal as electrodes on both sides (the battery uses the ultra-thin polymer solid electrolyte membrane prepared in Example 1 of the present invention) was subjected to a cycle test. The cycle test results are as follows: Figure 6 As shown, from Figure 6 It can be seen that the battery is -2 , 0.1 mAh cm -2 Under the conditions of , a stable cycle of more than 2000 hours was achieved, indicating that the ultra-thin polymer solid electrolyte membrane prepared in Example 1 has good stability to lithium metal.

[0058] A battery with lithium iron phosphate (LFP) as the positive electrode and lithium metal as the negative electrode (the ultra-thin polymer solid electrolyte membrane prepared in Example 1 of the present invention is used in the battery) is subjected to a cycle test. The cycle test results are shown in FIG. Figure 7 As shown, from Figure 7 It can be seen from the figure that the battery can be stably cycled for more than 2000 cycles at a rate of 1 C, and the maximum discharge capacity reaches 146 mAh g -1 , the capacity retention rate is 80%, the Coulomb efficiency is above 99%, and it has good capacity performance, indicating that it has good practical application prospects.

[0059] A battery with lithium nickel cobalt manganese oxide NCM811 as the positive electrode and lithium metal as the negative electrode (the ultra-thin polymer solid electrolyte membrane prepared in Example 1 of the present invention is used in the battery) is subjected to a cycle test. The cycle test results are as follows: Figure 8 As shown, from Figure 8 As can be seen from the figure, the discharge capacity is as high as 188 mAh g at 0.5 C. -1 The battery maintained stable cycling for 800 cycles, with a Coulombic efficiency exceeding 99.5% and a capacity retention rate of 71%. The above results demonstrate that the lithium metal battery assembled with the ultra-thin polymer solid electrolyte membrane prepared in Example 1 can still achieve excellent capacity performance and cycling stability for high-voltage positive electrodes.

[0060] Example 2

[0061] Ultrathin polymer solid electrolyte membrane: its raw materials include N,N-methylenebis(acrylamide), allylboronic acid pinacol ester, fluorinated electrolyte, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and a polymer membrane of composite boron nitride prepared by electrospinning; the fluorinated electrolyte includes lithium bis(trifluoromethylsulfonyl)imide, lithium difluorooxalatoborate, tetraethylene glycol dimethyl ether, and the compound shown in formula 2 (n is 4); the boron nitride used in the composite boron nitride polymer film is hexagonal boron nitride nanosheets, and the polymer is polyacrylonitrile.

[0062] The preparation method of the ultrathin polymer solid electrolyte membrane is as follows:

[0063] (1) Synthesis of fluorinated modified plasticizer molecules: Under argon protection, tetraethylene glycol was weighed into a flask, and a certain amount of anhydrous dichloromethane was added for argon protection. The system was placed in an ice-water bath, and 2.5 molar equivalents of ultra-dry pyridine were added dropwise at 0°C. After the addition was completed, stirring was continued for 10 minutes. Then, 2.5 molar equivalents of trifluoroacetic anhydride were added dropwise at 0°C. After the addition was completed, the mixture was returned to room temperature and reacted for 2 hours. After the reaction was completed, saturated sodium bicarbonate aqueous solution was added dropwise at 0°C to quench the reaction. After separation, the mixture was extracted with dichloromethane. The resulting organic phase was washed once with 1 mol / L hydrochloric acid and sodium chloride aqueous solution, dried, and the solvent was removed by rotary evaporation to obtain the compound shown in Formula 2. , n is 4.

[0064] (2) Preparation of composite boron nitride polymer membrane: 1.5 g of polyacrylonitrile was dissolved in 8.5 g of N,N-dimethylformamide solvent, and then 0.05 g of hexagonal boron nitride nanosheets was added and stirred at room temperature for 6 hours to obtain a uniformly dispersed electrospinning precursor solution; the precursor solution was spun into a nanofiber membrane under the spinning conditions of an electrostatic voltage of 15 kV, a spinning distance of 15 cm, a spinning solution flow rate of 0.5 mL / h, and a receiving tube speed of 1000 rpm, and then vacuum dried at 80°C for 24 hours and hot rolled at 60°C to obtain a composite boron nitride polymer membrane with a membrane thickness of 10 μm.

[0065] (3) Preparation of ultrathin polymer solid electrolyte membrane: 0.96 g of lithium bis(trifluoromethylsulfonyl)imide, 0.12 g of lithium difluorooxalatoborate, 0.72 g of tetraethylene glycol dimethyl ether and 0.20 g of the compound shown in Formula 2 were prepared into a fluorinated electrolyte; 0.01 g of N,N-methylenebis(acrylamide), 0.03 g of allylboronic acid pinacol ester, 0.16 g of the fluorinated electrolyte and 1.2 mg of 2-hydroxy-2-methyl-1-phenyl-1-propanone were mixed to obtain a polymerization precursor solution; a polymer film of composite boron nitride was placed on a glass plate, a layer of polymerization precursor solution was scraped on the surface, and then irradiated under ultraviolet light for 10 minutes for photoinitiated polymerization to prepare an ultrathin polymer solid electrolyte membrane with a thickness of 25 μm.

[0066] A battery with lithium nickel cobalt manganese oxide NCM811 as the positive electrode and lithium metal as the negative electrode (the ultra-thin polymer solid electrolyte membrane prepared in Example 2 of the present invention is used in the battery) is subjected to a cycle test. The cycle test results are as follows: Figure 9 As shown, from Figure 9 As can be seen from the figure, the discharge capacity is as high as 189 mAh g at 0.5 C. -1 The above results prove that the lithium metal battery assembled with the ultra-thin polymer solid electrolyte membrane prepared in Example 2 can still achieve excellent capacity performance for the high-voltage positive electrode.

[0067] Example 3

[0068] Ultrathin polymer solid electrolyte membrane: its raw materials include N,N-methylenebis(acrylamide), allylboronic acid pinacol ester, fluorinated electrolyte, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and a polymer membrane of composite boron nitride prepared by electrospinning; the fluorinated electrolyte includes lithium bis(trifluoromethylsulfonyl)imide, lithium difluorooxalatoborate, tetraethylene glycol dimethyl ether, and the compound shown in formula 1 (n is 4); the boron nitride used in the composite boron nitride polymer film is hexagonal boron nitride nanosheets, and the polymer is polyacrylonitrile.

[0069] The preparation method of the ultrathin polymer solid electrolyte membrane is as follows:

[0070] (1) Synthesis of fluorinated modified plasticizer molecules: Under argon protection, tetraethylene glycol monomethyl ether was weighed into a flask, and a certain amount of anhydrous dichloromethane was added for argon protection. The system was placed in an ice-water bath, and 2.5 molar equivalents of ultra-dry pyridine were added dropwise at 0°C. After the addition was completed, stirring was continued for 10 minutes. Then, 2.5 molar equivalents of trifluoroacetic anhydride were added dropwise at 0°C. After the addition was completed, the mixture was returned to room temperature and reacted for 2 hours. After the reaction was completed, saturated sodium bicarbonate aqueous solution was added dropwise at 0°C to quench the reaction. After separation, the mixture was extracted with dichloromethane. The resulting organic phase was washed once with 1 mol / L hydrochloric acid and once with sodium chloride aqueous solution, and then dried. The solvent was removed by rotary evaporation to obtain the compound shown in Formula 1. , n is 4.

[0071] (2) Preparation of composite boron nitride polymer membrane: 1.5 g of polyacrylonitrile was dissolved in 8.5 g of N,N-dimethylformamide solvent, and then 0.02 g of hexagonal boron nitride nanosheets was added and stirred at room temperature for 6 hours to obtain a uniformly dispersed electrospinning precursor solution; the precursor solution was spun into a nanofiber membrane under the spinning conditions of an electrostatic voltage of 15 kV, a spinning distance of 15 cm, a spinning solution flow rate of 0.5 mL / h, and a receiving tube speed of 1000 rpm, and then vacuum dried at 80°C for 24 hours and hot rolled at 60°C to obtain a composite boron nitride polymer membrane with a membrane thickness of 10 μm.

[0072] (3) Preparation of ultrathin polymer solid electrolyte membrane: 0.96 g of lithium bis(trifluoromethylsulfonyl)imide, 0.12 g of lithium difluorooxalatoborate, 0.72 g of tetraethylene glycol dimethyl ether and 0.20 g of the compound shown in Formula 1 were prepared into a fluorinated electrolyte; 0.01 g of N,N-methylenebis(acrylamide), 0.03 g of allylboronic acid pinacol ester, 0.16 g of the fluorinated electrolyte and 1.2 mg of 2-hydroxy-2-methyl-1-phenyl-1-propanone were mixed to obtain a polymerization precursor solution; a polymer film of composite boron nitride was placed on a glass plate, a layer of polymerization precursor solution was scraped on the surface, and then irradiated under ultraviolet light for 10 minutes for photoinitiated polymerization to prepare an ultrathin polymer solid electrolyte membrane with a thickness of 25 μm.

[0073] Example 4

[0074] Ultrathin polymer solid electrolyte membrane: its raw materials include N,N-methylenebis(acrylamide), allylboronic acid pinacol ester, fluorinated electrolyte, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and a polymer membrane of composite boron nitride prepared by electrospinning; the fluorinated electrolyte includes lithium bis(trifluoromethylsulfonyl)imide, lithium difluorooxalatoborate, tetraethylene glycol dimethyl ether, and the compound shown in formula 1 (n is 4); the boron nitride used in the composite boron nitride polymer film is hexagonal boron nitride nanosheets, and the polymer is polyacrylonitrile.

[0075] The preparation method of the ultrathin polymer solid electrolyte membrane is as follows:

[0076] (1) Synthesis of fluorinated modified plasticizer molecules: Under argon protection, tetraethylene glycol monomethyl ether was weighed into a flask, and a certain amount of anhydrous dichloromethane was added for argon protection. The system was placed in an ice-water bath, and 2.5 molar equivalents of ultra-dry pyridine were added dropwise at 0°C. After the addition was completed, stirring was continued for 10 minutes. Then, 2.5 molar equivalents of trifluoroacetic anhydride were added dropwise at 0°C. After the addition was completed, the mixture was returned to room temperature and reacted for 2 hours. After the reaction was completed, saturated sodium bicarbonate aqueous solution was added dropwise at 0°C to quench the reaction. After separation, the mixture was extracted with dichloromethane. The resulting organic phase was washed once with 1 mol / L hydrochloric acid and once with sodium chloride aqueous solution, and then dried. The solvent was removed by rotary evaporation to obtain the compound shown in Formula 1. , n is 4.

[0077] (2) Preparation of composite boron nitride polymer membrane: 1.5 g of polyacrylonitrile was dissolved in 8.5 g of N,N-dimethylformamide solvent, and then 0.10 g of hexagonal boron nitride nanosheets was added and stirred at room temperature for 6 hours to obtain a uniformly dispersed electrospinning precursor solution; the precursor solution was spun into a nanofiber membrane under the spinning conditions of an electrostatic voltage of 15 kV, a spinning distance of 15 cm, a spinning solution flow rate of 0.5 mL / h, and a receiving tube speed of 1000 rpm, and then vacuum dried at 80°C for 24 hours and hot rolled at 60°C to obtain a composite boron nitride polymer membrane with a membrane thickness of 10 μm.

[0078] (3) Preparation of ultrathin polymer solid electrolyte membrane: 0.96 g of lithium bis(trifluoromethylsulfonyl)imide, 0.12 g of lithium difluorooxalatoborate, 0.72 g of tetraethylene glycol dimethyl ether and 0.20 g of the compound shown in Formula 1 were prepared into a fluorinated electrolyte; 0.01 g of N,N-methylenebis(acrylamide), 0.03 g of allylboronic acid pinacol ester, 0.16 g of the fluorinated electrolyte and 1.2 mg of 2-hydroxy-2-methyl-1-phenyl-1-propanone were mixed to obtain a polymerization precursor solution; a polymer film of composite boron nitride was placed on a glass plate, a layer of polymerization precursor solution was scraped on the surface, and then irradiated under ultraviolet light for 10 minutes for photoinitiated polymerization to prepare an ultrathin polymer solid electrolyte membrane with a thickness of 25 μm.

[0079] Example 5

[0080] Ultra-thin polymer solid electrolyte membrane: its raw materials include polyethylene glycol dimethacrylate, allyl boric acid pinacol ester, fluorinated electrolyte, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and a polymer membrane of composite boron nitride prepared by electrospinning; the fluorinated electrolyte includes lithium bis(trifluoromethylsulfonyl)imide, lithium difluorooxalatoborate, tetraethylene glycol dimethyl ether, and the compound shown in formula 1 (n is 4); the boron nitride used in the composite boron nitride polymer film is hexagonal boron nitride nanosheets, and the polymer is polyacrylonitrile.

[0081] The preparation method of the ultrathin polymer solid electrolyte membrane is as follows:

[0082] (1) Synthesis of fluorinated modified plasticizer molecules: Under argon protection, tetraethylene glycol monomethyl ether was weighed into a flask, and a certain amount of anhydrous dichloromethane was added for argon protection. The system was placed in an ice-water bath, and 2.5 molar equivalents of ultra-dry pyridine were added dropwise at 0°C. After the addition was completed, stirring was continued for 10 minutes. Then, 2.5 molar equivalents of trifluoroacetic anhydride were added dropwise at 0°C. After the addition was completed, the mixture was returned to room temperature and reacted for 2 hours. After the reaction was completed, saturated sodium bicarbonate aqueous solution was added dropwise at 0°C to quench the reaction. After separation, the mixture was extracted with dichloromethane. The resulting organic phase was washed once with 1 mol / L hydrochloric acid and once with sodium chloride aqueous solution, and then dried. The solvent was removed by rotary evaporation to obtain the compound shown in Formula 1. , n is 4.

[0083] (2) Preparation of composite boron nitride polymer membrane: 1.5 g of polyacrylonitrile was dissolved in 8.5 g of N,N-dimethylformamide solvent, and then 0.05 g of hexagonal boron nitride nanosheets was added and stirred at room temperature for 6 hours to obtain a uniformly dispersed electrospinning precursor solution; the precursor solution was spun into a nanofiber membrane under the spinning conditions of an electrostatic voltage of 15 kV, a spinning distance of 15 cm, a spinning solution flow rate of 0.5 mL / h, and a receiving tube speed of 1000 rpm, and then vacuum dried at 80°C for 24 hours and hot rolled at 60°C to obtain a composite boron nitride polymer membrane with a membrane thickness of 10 μm.

[0084] (3) Preparation of ultrathin polymer solid electrolyte membrane: 0.96 g of lithium bis(trifluoromethylsulfonyl)imide, 0.12 g of lithium difluorooxalatoborate, 0.72 g of tetraethylene glycol dimethyl ether and 0.20 g of the compound shown in Formula 1 were prepared into a fluorinated electrolyte; 0.01 g of polyethylene glycol dimethacrylate (molecular weight 550 g / mol), 0.03 g of allylboronic acid pinacol ester, 0.16 g of the fluorinated electrolyte and 1.2 mg of 2-hydroxy-2-methyl-1-phenyl-1-propanone were mixed to obtain a polymerization precursor solution; a polymer film of composite boron nitride was placed on a glass plate, a layer of polymerization precursor solution was scraped on the surface of the glass plate, and then the film was irradiated under ultraviolet light for 10 minutes for photoinitiated polymerization to prepare an ultrathin polymer solid electrolyte membrane with a thickness of 25 μm.

[0085] Example 6

[0086] Ultrathin polymer solid electrolyte membrane: its raw materials include N,N-methylenebis(acrylamide), allylboronic acid pinacol ester, fluorinated electrolyte, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and a polymer membrane of composite boron nitride prepared by electrospinning; the fluorinated electrolyte includes lithium bis(trifluoromethylsulfonyl)imide, lithium difluorooxalatoborate, tetraethylene glycol dimethyl ether, and the compound shown in formula 1 (n is 4); the boron nitride used in the composite boron nitride polymer film is hexagonal boron nitride nanosheets, and the polymer is polyacrylonitrile.

[0087] The preparation method of the ultrathin polymer solid electrolyte membrane is as follows:

[0088] (1) Synthesis of fluorinated modified plasticizer molecules: Under argon protection, tetraethylene glycol monomethyl ether was weighed into a flask, and a certain amount of anhydrous dichloromethane was added for argon protection. The system was placed in an ice-water bath, and 2.5 molar equivalents of ultra-dry pyridine were added dropwise at 0°C. After the addition was completed, stirring was continued for 10 minutes. Then, 2.5 molar equivalents of trifluoroacetic anhydride were added dropwise at 0°C. After the addition was completed, the mixture was returned to room temperature and reacted for 2 hours. After the reaction was completed, saturated sodium bicarbonate aqueous solution was added dropwise at 0°C to quench the reaction. After separation, the mixture was extracted with dichloromethane. The resulting organic phase was washed once with 1 mol / L hydrochloric acid and once with sodium chloride aqueous solution, and then dried. The solvent was removed by rotary evaporation to obtain the compound shown in Formula 1. , n is 4.

[0089] (2) Preparation of composite boron nitride polymer membrane: 1.5 g of polyacrylonitrile was dissolved in 8.5 g of N,N-dimethylformamide solvent, and then 0.05 g of hexagonal boron nitride nanosheets was added and stirred at room temperature for 6 hours to obtain a uniformly dispersed electrospinning precursor solution; the precursor solution was spun into a nanofiber membrane under the spinning conditions of an electrostatic voltage of 15 kV, a spinning distance of 15 cm, a spinning solution flow rate of 0.5 mL / h, and a receiving tube speed of 1000 rpm, and then vacuum dried at 80°C for 24 hours and hot rolled at 60°C to obtain a composite boron nitride polymer membrane with a membrane thickness of 10 μm.

[0090] (3) Preparation of ultrathin polymer solid electrolyte membrane: 0.96 g of lithium bis(trifluoromethylsulfonyl)imide, 0.12 g of lithium difluorooxalatoborate, 0.82 g of tetraethylene glycol dimethyl ether and 0.10 g of the compound shown in Formula 1 were prepared into a fluorinated electrolyte; 0.01 g of N,N-methylenebis(acrylamide), 0.03 g of allylboronic acid pinacol ester, 0.16 g of the fluorinated electrolyte and 1.2 mg of 2-hydroxy-2-methyl-1-phenyl-1-propanone were mixed to obtain a polymerization precursor solution; a polymer film of composite boron nitride was placed on a glass plate, a layer of polymerization precursor solution was scraped on the surface, and then irradiated under ultraviolet light for 10 minutes for photoinitiated polymerization to prepare an ultrathin polymer solid electrolyte membrane with a thickness of 25 μm.

[0091] Example 7

[0092] Ultrathin polymer solid electrolyte membrane: its raw materials include N,N-methylenebis(acrylamide), allylboronic acid pinacol ester, fluorinated electrolyte, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and a polymer membrane of composite boron nitride prepared by electrospinning; the fluorinated electrolyte includes lithium bis(trifluoromethylsulfonyl)imide, lithium difluorooxalatoborate, tetraethylene glycol dimethyl ether, and the compound shown in formula 3 (n is 4); the boron nitride used in the composite boron nitride polymer film is hexagonal boron nitride nanosheets, and the polymer is polyacrylonitrile.

[0093] The preparation method of the ultrathin polymer solid electrolyte membrane is as follows:

[0094] (1) Synthesis of fluorinated modified plasticizer molecules: Under argon protection, tetraethylene glycol monomethyl ether was weighed into a flask, and a certain amount of anhydrous dichloromethane was added for argon protection. The system was placed in an ice-water bath, and 2.5 molar equivalents of ultra-dry pyridine were added dropwise at 0°C. After the addition was completed, stirring was continued for 10 minutes. Then, 2.5 molar equivalents of difluoroacetic anhydride were added dropwise at 0°C. After the addition was completed, the mixture was returned to room temperature and reacted for 2 hours. After the reaction was completed, saturated sodium bicarbonate aqueous solution was added dropwise at 0°C to quench the reaction. After separation, the mixture was extracted with dichloromethane. The resulting organic phase was washed once with 1 mol / L hydrochloric acid and once with sodium chloride aqueous solution, and then dried. The solvent was removed by rotary evaporation to obtain the compound shown in Formula 3. , n is 4.

[0095] (2) Preparation of composite boron nitride polymer membrane: 1.5 g of polyacrylonitrile was dissolved in 8.5 g of N,N-dimethylformamide solvent, and then 0.05 g of hexagonal boron nitride nanosheets was added and stirred at room temperature for 6 hours to obtain a uniformly dispersed electrospinning precursor solution; the precursor solution was spun into a nanofiber membrane under the spinning conditions of an electrostatic voltage of 15 kV, a spinning distance of 15 cm, a spinning solution flow rate of 0.5 mL / h, and a receiving tube speed of 1000 rpm, and then vacuum dried at 80°C for 24 hours and hot rolled at 60°C to obtain a composite boron nitride polymer membrane with a membrane thickness of 10 μm.

[0096] (3) Preparation of ultrathin polymer solid electrolyte membrane: 0.96 g of lithium bis(trifluoromethylsulfonyl)imide, 0.12 g of lithium difluorooxalatoborate, 0.72 g of tetraethylene glycol dimethyl ether and 0.20 g of the compound shown in Formula 3 were prepared into a fluorinated electrolyte; 0.01 g of N,N-methylenebis(acrylamide), 0.03 g of allylboronic acid pinacol ester, 0.16 g of the fluorinated electrolyte and 1.2 mg of 2-hydroxy-2-methyl-1-phenyl-1-propanone were mixed to obtain a polymerization precursor solution; a polymer film of composite boron nitride was placed on a glass plate, a layer of polymerization precursor solution was scraped on the surface, and then irradiated under ultraviolet light for 10 minutes for photoinitiated polymerization to prepare an ultrathin polymer solid electrolyte membrane with a thickness of 25 μm.

[0097] Example 8

[0098] Ultrathin polymer solid electrolyte membrane: its raw materials include N,N-methylenebis(acrylamide), allylboronic acid pinacol ester, fluorinated electrolyte, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and a polymer membrane of composite boron nitride prepared by electrospinning; the fluorinated electrolyte includes lithium bis(trifluoromethylsulfonyl)imide, lithium difluorooxalatoborate, tetraethylene glycol dimethyl ether, and the compound shown in formula 1 (n is 5); the boron nitride used in the boron nitride composite polymer film is hexagonal boron nitride nanosheets, and the polymer is polyacrylonitrile.

[0099] The preparation method of the ultrathin polymer solid electrolyte membrane is as follows:

[0100] (1) Synthesis of fluorinated modified plasticizer molecules: Under argon protection, weigh pentaethylene glycol monomethyl ether into a flask, add a certain amount of anhydrous dichloromethane, and perform argon protection. Place the system in an ice-water bath, and add 2.5 molar equivalents of ultra-dry pyridine dropwise at 0°C. After the addition is complete, continue stirring for 10 minutes, then continue to add 2.5 molar equivalents of trifluoroacetic anhydride dropwise at 0°C. After the addition is complete, return to room temperature and react for 2 hours. After the reaction is completed, add saturated sodium bicarbonate aqueous solution at 0°C to quench the reaction, separate the liquids, and extract with dichloromethane. The resulting organic phase is washed once with 1 mol / L hydrochloric acid and sodium chloride aqueous solution, then dried, and the solvent is removed by rotary evaporation to obtain the compound shown in Formula 1. , n is 5.

[0101] (2) Preparation of composite boron nitride polymer membrane: 1.5 g of polyacrylonitrile was dissolved in 8.5 g of N,N-dimethylformamide solvent, and then 0.05 g of hexagonal boron nitride nanosheets was added and stirred at room temperature for 6 hours to obtain a uniformly dispersed electrospinning precursor solution; the precursor solution was spun into a nanofiber membrane under the spinning conditions of an electrostatic voltage of 15 kV, a spinning distance of 15 cm, a spinning solution flow rate of 0.5 mL / h, and a receiving tube speed of 1000 rpm, and then vacuum dried at 80°C for 24 hours and hot rolled at 60°C to obtain a composite boron nitride polymer membrane with a membrane thickness of 10 μm.

[0102] (3) Preparation of ultrathin polymer solid electrolyte membrane: 0.96 g of lithium bis(trifluoromethylsulfonyl)imide, 0.12 g of lithium difluorooxalatoborate, 0.72 g of tetraethylene glycol dimethyl ether and 0.20 g of the compound shown in Formula 1 were prepared into a fluorinated electrolyte; 0.01 g of N,N-methylenebis(acrylamide), 0.03 g of allylboronic acid pinacol ester, 0.16 g of the fluorinated electrolyte and 1.2 mg of 2-hydroxy-2-methyl-1-phenyl-1-propanone were mixed to obtain a polymerization precursor solution; a polymer film of composite boron nitride was placed on a glass plate, a layer of polymerization precursor solution was scraped on the surface, and then irradiated under ultraviolet light for 10 minutes for photoinitiated polymerization to prepare an ultrathin polymer solid electrolyte membrane with a thickness of 25 μm.

[0103] Example 9

[0104] Ultrathin polymer solid electrolyte membrane: its raw materials include N,N-methylenebis(acrylamide), allylboronic acid pinacol ester, fluorinated electrolyte, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and a polymer membrane of composite boron nitride prepared by electrospinning; the fluorinated electrolyte includes lithium bis(trifluoromethylsulfonyl)imide, lithium difluorooxalatoborate, tetraethylene glycol dimethyl ether, and the compound shown in formula 1 (n is 6); the boron nitride used in the composite boron nitride polymer film is hexagonal boron nitride nanosheets, and the polymer is polyacrylonitrile.

[0105] The preparation method of the ultrathin polymer solid electrolyte membrane is as follows:

[0106] (1) Synthesis of fluorinated modified plasticizer molecules: Under argon protection, hexaethylene glycol monomethyl ether was weighed into a flask, and a certain amount of anhydrous dichloromethane was added for argon protection. The system was placed in an ice-water bath, and 2.5 molar equivalents of ultra-dry pyridine were added dropwise at 0°C. After the addition was completed, stirring was continued for 10 minutes. Then, 2.5 molar equivalents of trifluoroacetic anhydride were added dropwise at 0°C. After the addition was completed, the mixture was returned to room temperature and reacted for 2 hours. After the reaction was completed, saturated sodium bicarbonate aqueous solution was added dropwise at 0°C to quench the reaction. After separation, the mixture was extracted with dichloromethane. The resulting organic phase was washed once with 1 mol / L hydrochloric acid and once with sodium chloride aqueous solution, and then dried. The solvent was removed by rotary evaporation to obtain the compound shown in Formula 1. , n is 6.

[0107] (2) Preparation of composite boron nitride polymer membrane: 1.5 g of polyacrylonitrile was dissolved in 8.5 g of N,N-dimethylformamide solvent, and then 0.05 g of hexagonal boron nitride nanosheets was added and stirred at room temperature for 6 hours to obtain a uniformly dispersed electrospinning precursor solution; the precursor solution was spun into a nanofiber membrane under the spinning conditions of an electrostatic voltage of 15 kV, a spinning distance of 15 cm, a spinning solution flow rate of 0.5 mL / h, and a receiving tube speed of 1000 rpm, and then vacuum dried at 80°C for 24 hours and hot rolled at 60°C to obtain a composite boron nitride polymer membrane with a membrane thickness of 10 μm.

[0108] (3) Preparation of ultrathin polymer solid electrolyte membrane: 0.96 g of lithium bis(trifluoromethylsulfonyl)imide, 0.12 g of lithium difluorooxalatoborate, 0.72 g of tetraethylene glycol dimethyl ether and 0.20 g of the compound shown in Formula 1 were prepared into a fluorinated electrolyte; 0.01 g of N,N-methylenebis(acrylamide), 0.03 g of allylboronic acid pinacol ester, 0.16 g of the fluorinated electrolyte and 1.2 mg of 2-hydroxy-2-methyl-1-phenyl-1-propanone were mixed to obtain a polymerization precursor solution; a polymer film of composite boron nitride was placed on a glass plate, a layer of polymerization precursor solution was scraped on the surface, and then irradiated under ultraviolet light for 10 minutes for photoinitiated polymerization to prepare an ultrathin polymer solid electrolyte membrane with a thickness of 25 μm.

[0109] Example 10

[0110] Ultrathin polymer solid electrolyte membrane: its raw materials include N,N-methylenebis(acrylamide), allylboronic acid pinacol ester, fluorinated electrolyte, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and a polymer membrane of composite boron nitride prepared by electrospinning; the fluorinated electrolyte includes lithium bis(trifluoromethylsulfonyl)imide, lithium difluorooxalatoborate, tetraethylene glycol dimethyl ether, and the compound shown in formula 1 (n is 4); the boron nitride used in the composite boron nitride polymer film is hexagonal boron nitride nanosheets, and the polymer is polyacrylonitrile.

[0111] The preparation method of the ultrathin polymer solid electrolyte membrane is as follows:

[0112] (1) Synthesis of fluorinated modified plasticizer molecules: Under argon protection, tetraethylene glycol monomethyl ether was weighed into a flask, and a certain amount of anhydrous dichloromethane was added for argon protection. The system was placed in an ice-water bath, and 2.5 molar equivalents of ultra-dry pyridine were added dropwise at 0°C. After the addition was completed, stirring was continued for 10 minutes. Then, 2.5 molar equivalents of trifluoroacetic anhydride were added dropwise at 0°C. After the addition was completed, the mixture was returned to room temperature and reacted for 2 hours. After the reaction was completed, saturated sodium bicarbonate aqueous solution was added dropwise at 0°C to quench the reaction. After separation, the mixture was extracted with dichloromethane. The resulting organic phase was washed once with 1 mol / L hydrochloric acid and once with sodium chloride aqueous solution, and then dried. The solvent was removed by rotary evaporation to obtain the compound shown in Formula 1. , n is 4.

[0113] (2) Preparation of composite boron nitride polymer membrane: 1.5 g of polyacrylonitrile was dissolved in 8.5 g of N,N-dimethylformamide solvent, and then 0.05 g of hexagonal boron nitride nanosheets was added and stirred at room temperature for 6 hours to obtain a uniformly dispersed electrospinning precursor solution; the precursor solution was spun into a nanofiber membrane under the spinning conditions of an electrostatic voltage of 15 kV, a spinning distance of 15 cm, a spinning solution flow rate of 0.5 mL / h, and a receiving tube speed of 1000 rpm, and then vacuum dried at 80°C for 24 hours and hot rolled at 60°C to obtain a composite boron nitride polymer membrane with a membrane thickness of 5 μm.

[0114] (3) Preparation of ultrathin polymer solid electrolyte membrane: 0.96 g of lithium bis(trifluoromethylsulfonyl)imide, 0.12 g of lithium difluorooxalatoborate, 0.72 g of tetraethylene glycol dimethyl ether and 0.20 g of the compound shown in Formula 1 were prepared into a fluorinated electrolyte; 0.01 g of N,N-methylenebis(acrylamide), 0.03 g of allylboronic acid pinacol ester, 0.16 g of the fluorinated electrolyte and 1.2 mg of 2-hydroxy-2-methyl-1-phenyl-1-propanone were mixed to obtain a polymerization precursor solution; a polymer film of composite boron nitride was placed on a glass plate, a layer of polymerization precursor solution was scraped on the surface, and then irradiated under ultraviolet light for 10 minutes for photoinitiated polymerization to prepare an ultrathin polymer solid electrolyte membrane with a thickness of 20 μm.

[0115] Example 11

[0116] Ultrathin polymer solid electrolyte membrane: its raw materials include N,N-methylenebis(acrylamide), allylboronic acid pinacol ester, fluorinated electrolyte, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and a polymer membrane of composite boron nitride prepared by electrospinning; the fluorinated electrolyte includes lithium bis(trifluoromethylsulfonyl)imide, lithium difluorooxalatoborate, tetraethylene glycol dimethyl ether, and the compound shown in formula 1 (n is 4); the boron nitride used in the composite boron nitride polymer film is hexagonal boron nitride nanosheets, and the polymer is polyacrylonitrile.

[0117] The preparation method of the ultrathin polymer solid electrolyte membrane is as follows:

[0118] (1) Synthesis of fluorinated modified plasticizer molecules: Under argon protection, tetraethylene glycol monomethyl ether was weighed into a flask, and a certain amount of anhydrous dichloromethane was added for argon protection. The system was placed in an ice-water bath, and 2.5 molar equivalents of ultra-dry pyridine were added dropwise at 0°C. After the addition was completed, stirring was continued for 10 minutes. Then, 2.5 molar equivalents of trifluoroacetic anhydride were added dropwise at 0°C. After the addition was completed, the mixture was returned to room temperature and reacted for 2 hours. After the reaction was completed, saturated sodium bicarbonate aqueous solution was added dropwise at 0°C to quench the reaction. After separation, the mixture was extracted with dichloromethane. The resulting organic phase was washed once with 1 mol / L hydrochloric acid and once with sodium chloride aqueous solution, and then dried. The solvent was removed by rotary evaporation to obtain the compound shown in Formula 1. , n is 4.

[0119] (2) Preparation of composite boron nitride polymer membrane: 1.5 g of polyacrylonitrile was dissolved in 8.5 g of N,N-dimethylformamide solvent, and then 0.05 g of hexagonal boron nitride nanosheets was added and stirred at room temperature for 6 hours to obtain a uniformly dispersed electrospinning precursor solution; the precursor solution was spun into a nanofiber membrane under the spinning conditions of an electrostatic voltage of 15 kV, a spinning distance of 15 cm, a spinning solution flow rate of 0.5 mL / h, and a receiving tube speed of 1000 rpm, and then vacuum dried at 80°C for 24 hours and hot rolled at 60°C to obtain a composite boron nitride polymer membrane with a membrane thickness of 15 μm.

[0120] (3) Preparation of ultrathin polymer solid electrolyte membrane: 0.96 g of lithium bis(trifluoromethylsulfonyl)imide, 0.12 g of lithium difluorooxalatoborate, 0.72 g of tetraethylene glycol dimethyl ether and 0.20 g of the compound shown in Formula 1 were prepared into a fluorinated electrolyte; 0.01 g of N,N-methylenebis(acrylamide), 0.03 g of allylboronic acid pinacol ester, 0.16 g of the fluorinated electrolyte and 1.2 mg of 2-hydroxy-2-methyl-1-phenyl-1-propanone were mixed to obtain a polymerization precursor solution; a polymer film of composite boron nitride was placed on a glass plate, a layer of polymerization precursor solution was scraped on the surface, and then irradiated under ultraviolet light for 10 minutes for photoinitiated polymerization to prepare an ultrathin polymer solid electrolyte membrane with a thickness of 30 μm.

[0121] Comparative Example 1

[0122] Ultra-thin polymer solid electrolyte membrane: its raw materials include a mixture of N,N-methylenebis(acrylamide), allylboronic acid pinacol ester, electrolyte, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and a polymer membrane prepared by electrospinning; the electrolyte includes lithium bis(trifluoromethylsulfonyl)imide, lithium difluorooxalatoborate, and tetraethylene glycol dimethyl ether; the polymer used in the polymer membrane is polyacrylonitrile.

[0123] The preparation method of the ultrathin polymer solid electrolyte membrane is as follows:

[0124] (1) Preparation of polymer membrane: 1.5 g of polyacrylonitrile was dissolved in 8.5 g of N,N-dimethylformamide solvent and stirred at room temperature for 6 hours to obtain a uniformly dispersed electrospinning precursor solution; the precursor solution was spun into a nanofiber membrane under the spinning conditions of an electrostatic voltage of 15 kV, a spinning distance of 15 cm, a spinning solution flow rate of 0.5 mL / h, and a receiving tube speed of 1000 rpm, and then vacuum dried at 80°C for 24 hours and hot rolled at 60°C to obtain a polymer membrane with a membrane thickness of 10 μm.

[0125] (2) Preparation of ultrathin polymer solid electrolyte membrane: 1.148 g of lithium bis(trifluoromethylsulfonyl)imide, 0.144 g of lithium difluorooxalatoborate, and 1.11 g of tetraethylene glycol dimethyl ether were prepared as an electrolyte; 0.01 g of N,N-methylenebis(acrylamide), 0.03 g of allylboronic acid pinacol ester, 0.16 g of electrolyte, and 1.2 mg of 2-hydroxy-2-methyl-1-phenyl-1-propanone were mixed to obtain a polymerization precursor solution; a polymer membrane was placed on a glass plate, a layer of polymerization precursor solution was scraped on the surface, and then the membrane was irradiated under ultraviolet light for 10 minutes for photoinitiated polymerization to prepare an ultrathin polymer solid electrolyte membrane with a thickness of 25 μm.

[0126] A battery with lithium nickel cobalt manganese oxide NCM811 as the positive electrode and lithium metal as the negative electrode (the ultra-thin polymer solid electrolyte membrane prepared in Comparative Example 1 of the present invention is used in the battery) is subjected to a cycle test. The cycle test results are shown in FIG. Figure 10 As shown, from Figure 10 As can be seen from the figure, the discharge capacity is low at 0.5 C, only 174 mAh g -1 The above results demonstrate that the lithium metal battery assembled with the ultrathin polymer solid electrolyte membrane prepared in Comparative Example 1 without boron nitride nanosheets and fluorinated modified plasticizer has poor performance in high-voltage positive electrode capacity.

[0127] Comparative Example 2

[0128] Ultra-thin polymer solid electrolyte membrane: Its raw materials include a mixture of N,N-methylenebis(acrylamide), allylboronic acid pinacol ester, electrolyte, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and a composite boron nitride polymer membrane prepared by electrospinning; the electrolyte includes lithium bis(trifluoromethylsulfonyl)imide, lithium difluorooxalatoborate, and tetraethylene glycol dimethyl ether; the boron nitride used in the composite boron nitride polymer membrane is hexagonal boron nitride nanosheets, and the polymer is polyacrylonitrile.

[0129] The preparation method of the ultrathin polymer solid electrolyte membrane is as follows:

[0130] (1) Preparation of composite boron nitride polymer membrane: 1.5 g of polyacrylonitrile was dissolved in 8.5 g of N,N-dimethylformamide solvent, and then 0.05 g of hexagonal boron nitride nanosheets was added and stirred at room temperature for 6 hours to obtain a uniformly dispersed electrospinning precursor solution; the precursor solution was spun into a nanofiber membrane under the spinning conditions of an electrostatic voltage of 15 kV, a spinning distance of 15 cm, a spinning solution flow rate of 0.5 mL / h, and a receiving tube speed of 1000 rpm, and then vacuum dried at 80°C for 24 hours and hot rolled at 60°C to obtain a composite boron nitride polymer membrane with a membrane thickness of 10 μm.

[0131] (2) Preparation of ultrathin polymer solid electrolyte membrane: 1.148 g of lithium bis(trifluoromethylsulfonyl)imide, 0.144 g of lithium difluorooxalatoborate, and 1.11 g of tetraethylene glycol dimethyl ether were prepared as an electrolyte; 0.01 g of N,N-methylenebis(acrylamide), 0.03 g of allylboronic acid pinacol ester, 0.16 g of electrolyte, and 1.2 mg of 2-hydroxy-2-methyl-1-phenyl-1-propanone were mixed to obtain a polymerization precursor solution; a polymer film of composite boron nitride was placed on a glass plate, a layer of polymerization precursor solution was scraped on the surface, and then the film was irradiated under ultraviolet light for 10 minutes for photoinitiated polymerization to prepare an ultrathin polymer solid electrolyte membrane with a thickness of 25 μm.

[0132] A battery with lithium nickel cobalt manganese oxide NCM811 as the positive electrode and lithium metal as the negative electrode (the ultra-thin polymer solid electrolyte membrane prepared in Comparative Example 2 of the present invention is used in the battery) is subjected to a cycle test. The cycle test results are shown in FIG. Figure 11 As shown, from Figure 11 As can be seen from the figure, the discharge capacity at 0.5 C is improved compared with that of comparative example 1, but is still low, only 178 mAh g -1 The above results prove that the lithium metal battery assembled with the ultra-thin polymer solid electrolyte membrane prepared in Comparative Example 1 without fluorinated modified plasticizer has insufficient high-voltage positive electrode capacity.

[0133] In summary, the ultrathin polymer solid electrolyte membrane of the present invention can be used in secondary batteries such as lithium metal batteries. The fluorinated plasticizer molecules in the ultrathin polymer solid electrolyte membrane can effectively improve the transport kinetics of lithium ions and the stability of the electrolyte to high-voltage positive electrodes. At the same time, boron nitride achieves anion binding through Lewis acid-base interactions, enabling single lithium ion transport. The resulting ultrathin polymer solid electrolyte membrane has high ionic conductivity, a high lithium ion transference number, and high oxidative stability, enabling stable cycling of lithium metal batteries and excellent battery performance when paired with high-voltage positive electrode materials.

[0134] The above description is only a specific embodiment of the present invention, not all embodiments. Any equivalent transformation of the technical solution of the present invention made by ordinary technicians in this field after reading the specification of the present invention is covered by the claims of the present invention.

Claims

1. An ultrathin polymer solid electrolyte membrane, characterized in that: The raw materials of the ultra-thin polymer solid electrolyte membrane include: a mixture of a double-arm crosslinking agent, allyl boric acid pinacol ester, a fluorinated electrolyte, a photoinitiator, and a polymer membrane of composite boron nitride prepared by electrospinning; The fluorinated electrolyte comprises a lithium salt, tetraethylene glycol dimethyl ether and a fluorinated plasticizer, wherein the fluorinated plasticizer is selected from at least one of the compounds shown in Formula 1, Formula 2 and Formula 3. ； Formula 1 ； Formula 2 ； Formula 3 In Formula 1 to Formula 3, n is an integer of 1-10.

2. The ultrathin polymer solid electrolyte membrane according to claim 1, characterized in that The thickness of the ultra-thin polymer solid electrolyte membrane is 20-30 microns, and the thickness of the composite boron nitride polymer membrane is 5-15 microns.

3. The ultrathin polymer solid electrolyte membrane according to claim 1, characterized in that The mass ratio of the two-arm cross-linking agent, allyl boric acid pinacol ester, lithium salt, tetraethylene glycol dimethyl ether, and fluorinated modified plasticizer is (5-10):(10-20):(40-45):(25-35):(4-10), and the amount of the photoinitiator added is 1%-5% of the total mass of the two-arm cross-linking agent and the allyl boric acid pinacol ester; The mass ratio of boron nitride to polymer used in the preparation of the composite boron nitride polymer film using an electrospinning method is (0.2~2):

15.

4. The ultrathin polymer solid electrolyte membrane according to claim 1, characterized in that The double-arm cross-linking agent is selected from polyethylene glycol dimethacrylate or N,N-methylenebis(acrylamide); The molecular weight of the polyethylene glycol dimethacrylate is 200 g / mol to 600 g / mol.

5. The ultrathin polymer solid electrolyte membrane according to claim 1, characterized in that The photoinitiator is selected from at least one of 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone, and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide.

6. The ultrathin polymer solid electrolyte membrane according to claim 1, characterized in that The polymer used in the polymer film of the composite boron nitride is selected from at least one of polyacrylonitrile, polypropylene carbonate, polyethyleneimine, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride, and polymethyl methacrylate; The boron nitride used in the composite boron nitride polymer film is hexagonal boron nitride nanosheets, and the boron nitride sheet diameter is 80 nm to 100 nm.

7. The ultrathin polymer solid electrolyte membrane according to claim 1, characterized in that The lithium salt is selected from at least one of lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium difluorooxalatoborate.

8. The method for preparing an ultrathin polymer solid electrolyte membrane according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1: dissolving a polymer in a solvent to form a polymer solution, then uniformly dispersing boron nitride nanosheets in the polymer solution, obtaining a nanofiber membrane by electrospinning, and then drying and hot rolling to obtain a boron nitride composite polymer membrane; S2: mixing a dual-arm crosslinking agent, allylboronic acid pinacol ester, a fluorinated electrolyte, and a photoinitiator to obtain a polymerization precursor solution; S3: coating the polymerization precursor solution described in S2 on the surface of the polymer film of the composite boron nitride described in S1, and then performing photoinitiated polymerization to prepare an ultrathin polymer solid electrolyte membrane; or S1: mixing a double-arm crosslinking agent, allyl boric acid pinacol ester, a fluorinated electrolyte, and a photoinitiator to obtain a polymerization precursor solution; S2: dissolving a polymer in a solvent to form a polymer solution, then uniformly dispersing boron nitride nanosheets in the polymer solution, obtaining a nanofiber membrane by electrospinning, and then drying and hot rolling to obtain a boron nitride composite polymer membrane; S3: coating the polymerization precursor solution described in S1 on the surface of the polymer film of the composite boron nitride described in S2, and then performing photoinitiated polymerization to prepare an ultrathin polymer solid electrolyte.

9. Use of the ultrathin polymer solid electrolyte membrane according to any one of claims 1 to 7 in a lithium battery.

10. A lithium battery, characterized in that: The invention comprises the ultra-thin polymer solid electrolyte membrane according to any one of claims 1 to 7.

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