Single ion conduction solid polymer electrolyte membrane, preparation method thereof and lithium battery

Abstract

The invention discloses a single-ion conduction solid-state polymer electrolyte membrane, a preparation method thereof and a lithium battery, and belongs to the field of solid-state polymer electrolyte. The single-ion conduction solid polymer electrolyte membrane comprises a polymer electrostatic spinning membrane, and solid polymer electrolyte is compounded on the inner and outer surfaces of pores of the polymer electrostatic spinning membrane. A precursor solution of the solid polymer electrolyte contains 1-5 wt% of an alkenyl borate compound, 5-10 wt% of a fluorine-containing acrylate monomer, 1-5 wt% of a cross-linking agent and the balance of a lithium salt electrolyte. According to the invention, the holding relationship between the mechanical strength of the solid-state polymer electrolyte and the conductivity of lithium ions is effectively decoupled, so that the properties of the solid-state polymer electrolyte membrane are synergistically enhanced, the transference number of the lithium ions is greatly improved, the concentration polarization is effectively inhibited, the effects of reducing the internal resistance and improving the high-voltage stability are achieved, and the service life of the solid-state polymer electrolyte membrane is prolonged. And long-term stable circulation of the lithium battery can be ensured.

Description

Technical Field

[0001] The present application belongs to the field of solid polymer electrolyte technology, and in particular relates to a single-ion conducting solid polymer electrolyte membrane and a preparation method thereof, and a lithium battery. Background Art

[0002] Lithium metal batteries, with their high energy density, have become one of the best candidates for energy storage in long-range electric vehicles and portable electronic devices. However, the liquid electrolytes used in conventional lithium metal batteries readily react chemically with the lithium metal, leading to safety concerns and reduced cycle life. Therefore, inhibiting the chemical reaction between the electrolyte and the lithium metal has attracted considerable attention.

[0003] Solid-state polymer electrolytes can fundamentally reduce reactions with lithium metal, enabling lithium metal batteries to achieve higher cycle efficiency and safety, and have become a major research direction for promoting the commercial application of lithium metal batteries. However, most existing solid-state polymer electrolytes are dual-ion conductors. The bidirectional migration of lithium ions and anions can cause interfacial concentration polarization, resulting in low lithium ion transfer numbers, higher internal resistance and discharge voltage, and poor long-term stable cycling performance of lithium metal batteries.

[0004] Therefore, how to increase the migration number of lithium ions and avoid interfacial concentration polarization to ensure the cycle stability of lithium metal batteries has become an urgent problem to be solved in this field. Summary of the Invention

[0005] This application discloses a single-ion conductive solid polymer electrolyte membrane and its preparation method, and a lithium battery, which effectively solves the technical problems of low lithium ion migration number and high battery internal resistance and discharge voltage in existing solid polymer electrolyte membranes.

[0006] In order to achieve the above objectives, the technical solutions adopted in this application are: The first aspect of the present application provides a single ion conducting solid polymer electrolyte membrane, wherein the single ion conducting solid polymer electrolyte membrane of the present invention comprises a polymer electrospun membrane; The pores and outer surfaces of the polymer electrospinning membrane are compounded with a solid polymer electrolyte, and the precursor solution of the solid polymer electrolyte contains the following components: (a) 1-5 wt% of an alkenyl borate compound; (b) 5-10 wt% of a fluorinated acrylate monomer; (c) 1-5 wt% cross-linking agent; (d) the balance lithium salt electrolyte.

[0007] According to the disclosure of the first aspect, the material components of the polymer electrospinning membrane include a spinnable polymer and carboxyl cellulose; The mass ratio of the spinnable polymer to the carboxyl cellulose is 100:(10-20).

[0008] According to the disclosure of the first aspect, the spinnable polymer is selected from at least one of polyacrylonitrile, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polymethacrylate, polyimide and polyacrylamide; And / or, the carboxycellulose is at least one selected from carboxymethyl cellulose, carboxyethyl cellulose and carboxypropyl cellulose.

[0009] According to the disclosure of the first aspect, the alkenyl borate compound is represented by Formula 1: Formula 1; and / or, the fluorine-containing acrylate monomer is at least one selected from trifluoroethyl methacrylate, 2,2,3,3,3-pentafluoropropyl methacrylate, and 2,2,3,3,4,4,4-heptafluorobutyl methacrylate; And / or, the crosslinking agent is selected from ethoxylated trimethylolpropane triacrylate and N,N' - at least one of methylenebisacrylamide; and / or, the lithium salt electrolyte comprises an organic solvent and a fluorine-containing organic lithium salt; The organic solvent is selected from at least one of tetraethylene glycol dimethyl ether and triethylene glycol dimethyl ether; The fluorine-containing organic lithium salt is selected from at least one of lithium bis(trifluoromethanesulfonyl)imide and lithium bis(fluorosulfonyl)imide.

[0010] According to the disclosure of the first aspect, the cross-linking agent is selected from N,N' - A combination of methylene bisacrylamide and ethoxylated trimethylolpropane triacrylate in a mass ratio of 1:(0.25~4).

[0011] According to the disclosure of the first aspect, the thickness of the single ion conductor solid polymer electrolyte membrane is 20-120 μm.

[0012] The second aspect of the present application further discloses a method for preparing the above-mentioned single ion conducting solid polymer electrolyte membrane, the steps of which include: Preparation of polymer electrospun membranes; After the polymer electrostatic spinning membrane is fully infiltrated by the precursor solution, a photo-crosslinking polymerization reaction is initiated to obtain a single ion conducting solid polymer electrolyte membrane.

[0013] According to the disclosure of the second aspect, when the precursor solution is used to infiltrate the polymer electrospinning membrane, the mass area ratio of the precursor solution to the polymer electrospinning membrane is (0.5~1) g: (15~50) cm 2 .

[0014] According to the disclosure of the second aspect, the electrospinning parameters for preparing the polymer electrospinning membrane include: voltage of 15~20kV, distance from needle tip to receiver of 10~15cm, drum speed of 500~1000rpm, and solution pushing rate of 0.96~1.44mL / h.

[0015] The third aspect of the present application further discloses a lithium battery comprising the single ion conducting solid polymer electrolyte membrane of the present invention.

[0016] Compared with the prior art, the advantages or beneficial effects of this application include at least: The single-ion conducting solid polymer electrolyte membrane provided by the present invention is provided with a solid polymer electrolyte based on the precursor component, and the solid polymer electrolyte is filled in the pores of the polymer electrospun membrane and covers its outer surface, thereby effectively decoupling the constraint relationship between the mechanical strength of the solid polymer electrolyte and the lithium ion conductivity, so that the performance of the prepared solid polymer electrolyte membrane is synergistically enhanced, which not only greatly improves the migration number of lithium ions, but also effectively suppresses concentration polarization, thereby achieving the effect of reducing internal resistance and improving high-voltage stability, and can ensure the long-term stable cycle of the lithium battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some of the embodiments described in this application. For those skilled in the art, other drawings can be derived from these drawings without inventive effort.

[0018] Figure 1 Digital photos of SICC-SEM1 provided for this application; Figure 2 Electrochemical impedance spectroscopy of the SS|SICC-SEM1|SS symmetric battery provided in this application; Figure 3 The linear sweep voltammetry curve of the Li|SICC-SEM1|SS battery provided in this application; Figure 4 The current / time test curve and impedance test curve before and after polarization of the Li|SICC-SEM1|Li symmetric battery provided in this application; Figure 5 The Li|SICC-SEM1|Li symmetric battery provided in this application is 0.1mA·cm -2 Constant current test diagram under current density; Figure 6Cycling diagram of the LFP|SICC-SEM1|Li battery provided for this application at 0.5C; Figure 7 Cycle diagram of the NCM811|SICC-SEM1|Li battery provided in this application at 0.5C; Figure 8 The current / time test curve and impedance test curve before and after polarization of the Li|LE / ESM1|Li symmetrical battery provided in this application; Figure 9 Cycle diagram of NCM811|LE / ESM1|Li battery at 0.5C provided for this application; Figure 10 The current / time test curve and impedance test curve before and after polarization of the Li|SPEM1|Li symmetric battery provided in this application; Figure 11 Cycle diagram of NCM811|SPEM1|Li battery at 0.5C provided for this application; Figure 12 The current / time test curve and impedance test curve before and after polarization of the Li|SPEM2|Li symmetrical battery provided in this application; Figure 13 Cycle diagram of NCM811|SPEM2|Li battery at 0.5C provided in this application. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments described in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0020] In the following description of this specification, the term "and / or" is used to describe the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, B exists alone, and A and B exist simultaneously. A and B can be singular or plural; the symbol " / " means "or".

[0021] In the following description of this specification, the term "at least one" means one or more, and "plurality" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, "at least one of A, B, or C" or "at least one of A, B, and C" can mean any one of A, B, or C, or A+B, or A+C, or B+C, or A+B+C, where A, B, and C can be single or plural.

[0022] In the following description of this specification, the order of serial numbers does not mean the order of execution. Some or all steps can be executed in parallel or one after another. The execution order of each process should be determined by its function and internal logic, and does not constitute any limitation on the execution process of this embodiment.

[0023] In the following description of this specification, numerical ranges should be understood to also specifically disclose each intermediate value between the upper and lower limits of the range. Each smaller range between the intermediate values ​​in any stated range and any other stated value or intermediate value in the stated range is also included in this embodiment, and the upper and lower limits of the smaller ranges may independently be included or excluded in the range.

[0024] Unless otherwise indicated, the technical / scientific terms used in this specification have the meanings commonly understood by those skilled in the art. Although this specification describes only preferred materials and methods, any similar or equivalent methods and materials may be used in the specific embodiments or test cases. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0025] In the most widely studied "salt-in-polymer" solid polymer electrolyte, the diffusion coefficient of lithium ions in the polymer matrix is ​​much lower than that of unbound anions, resulting in the lithium ion migration number of the electrolyte system generally being 0.2~0.3. The low lithium ion migration number will cause the battery to form a serious ion concentration gradient and concentration polarization, resulting in an increase in the battery's operating voltage and serious interface puncture problems, affecting the cycle life of the lithium metal battery.

[0026] To increase the lithium ion transference number of a solid polymer electrolyte, the first aspect of the present invention provides a single-ion conducting solid polymer electrolyte membrane. The single-ion conducting solid polymer electrolyte membrane of the present invention comprises an electrospun polymer membrane, wherein the solid polymer electrolyte is composited within the pores and on the outer surface of the electrospun polymer membrane. The precursor solution of the solid polymer electrolyte contains the following components:

[0027] (a) 1-5 wt% of an alkenyl borate compound; (b) 5-10 wt% of a fluorinated acrylate monomer;

[0028] (c) 1-5 wt% cross-linking agent; (d) the balance lithium salt electrolyte.

[0029] It should be noted that the phrase "solid polymer electrolyte is composited within the pores and on the outer surface of the polymer electrospun membrane" as used herein means that the solid polymer electrolyte fills the pores of the polymer electrospun membrane and also covers the outer surface of the polymer electrospun membrane. The solid polymer electrolyte is formed by a photopolymerization reaction of its precursor solution.

[0030] The present invention forms a solid polymer electrolyte by cross-linking an alkenyl borate compound and a fluorinated acrylate. On the one hand, it can ensure good film formation of the solid polymer electrolyte while improving the chain segment mobility, effectively promoting the dissociation and conduction of lithium ions from anions, so that the solid electrolyte membrane has high ionic conductivity characteristics; on the other hand, it can synergistically anchor anions based on a cross-linked network and strong coordination, so that the anion freedom is significantly constrained, effectively achieving a single-ion conduction effect; thirdly, it can moderately improve the mechanical properties of the solid polymer electrolyte and effectively enhance the inhibition of lithium dendrite penetration. At the same time, the solid polymer electrolyte is introduced into the pores of the polymer electrospinning membrane and covers its outer surface. The two work together to accurately construct a network interpenetrating structure, effectively decoupling the constraints between the mechanical strength of the solid polymer electrolyte and the lithium ion conductivity. In addition, a phase separation structure is formed between the solid polymer electrolyte and the polymer electrospinning membrane, which can form a continuous ion conduction phase and a mechanically stable phase, so that the solid polymer electrolyte membrane exhibits higher lithium ion conductivity and better ability to inhibit lithium dendrite puncture, thereby effectively avoiding interfacial concentration polarization, achieving the effect of reducing the internal resistance of the battery and improving high-voltage stability, and providing a basis for the long-term stable cycle of lithium metal batteries.

[0031] In a possible disclosed example, the polymer electrospun membrane of the present invention comprises a spinnable polymer and carboxycellulose. The spinnable polymer and carboxycellulose interact with each other through hydrogen bonding, which allows cross-linking to form a continuous ion-conducting phase that facilitates lithium ion transport, further promoting lithium ion transport. The mass ratio of the spinnable polymer to the carboxycellulose is selected to be 100:(10-20), including but not limited to 100:10, 100:15, 100:20, or any other value within this mass ratio range.

[0032] In possible disclosed examples, the spinnable polymer is selected from any one or a combination of polyacrylonitrile, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polymethacrylate, polyimide, and polyacrylamide; and the carboxycellulose is selected from any one or a combination of carboxymethyl cellulose, carboxyethyl cellulose, and carboxypropyl cellulose. Hydrogen bonds exist between these spinnable polymers and the carboxycellulose polymers, allowing them to cross-link to form a polymer network structure with excellent chain mobility and mechanical strength. This effectively enhances lithium ion conduction and inhibits lithium dendrite penetration, thereby enabling the lithium battery to have long-term stable cycling performance.

[0033] In a possible disclosed example, the alkenyl borate compound of the present invention is represented by Formula 1:

[0034] Formula 1.

[0035] It should be noted that the present invention selects a benzene ring-containing alkenyl borate compound, whose benzene ring rigid group not only helps to improve the mechanical properties and thermal stability of the solid polymer electrolyte, but also improves the processability of the solid polymer electrolyte, providing support for decoupling the relationship between the mechanical strength and lithium ion conductivity of the solid polymer electrolyte. In addition, the alkenyl borate compound contains a dynamic covalent bond BO bond. This dynamic reversibility gives the cross-linked polymer and the solid polymer electrolyte containing it flexibility and self-healing ability, enabling self-repair, inhibiting the growth of lithium dendrites, and reducing the damage caused by lithium dendrite growth to the solid polymer electrolyte.

[0036] In possible disclosed examples, the fluorine-containing acrylate monomer is preferably at least one of trifluoroethyl methacrylate, 2,2,3,3,3-pentafluoropropyl methacrylate, and 2,2,3,3,4,4,4-heptafluorobutyl methacrylate.

[0037] It should be noted that these fluorinated acrylate compounds have a strong electron-withdrawing effect, which can reduce the highest occupied molecular orbital (HOMO) energy level of the polymer, thereby improving the antioxidant capacity of the polymer and being compatible with high-voltage positive electrodes. Furthermore, fluorinated acrylates can form an inorganic interface layer rich in LiF components, thereby improving the interfacial stability of the electrolyte / lithium metal negative electrode, promoting uniform lithium deposition / stripping, and effectively inhibiting lithium dendrite growth. Furthermore, alkenyl borate compounds can form dynamic chemical entanglements with the ester groups in acrylates through their own transesterification reaction characteristics, which helps to enhance the chain motion ability of the polymer matrix of the solid polymer electrolyte.

[0038] In a possible disclosed example, the crosslinking agent is selected from at least one of ethoxylated trimethylolpropane triacrylate and N,N'-methylenebisacrylamide, preferably a combination of ethoxylated trimethylolpropane triacrylate and N,N'-methylenebisacrylamide in a mass ratio of 0.25 to 4:1.

[0039] It should be noted that when the cross-linking agent is selected as a combination of ethoxylated trimethylolpropane triacrylate and N,N'-methylenebisacrylamide in a mass ratio of 0.25~4:1, N,N'-methylenebisacrylamide can provide abundant hydrogen bonds for the cross-linking network, which is beneficial to improving the mechanical strength of the solid polymer electrolyte; ethoxylated trimethylolpropane triacrylate contains a large number of ether oxygen segments, which can provide a lithium ion transmission path. The combined action of the two can decouple the constraint relationship between the mechanical strength and lithium ion conductivity of the solid polymer electrolyte.

[0040] In possible disclosed examples, the lithium salt electrolyte includes an organic solvent and a fluorine-containing organic lithium salt, wherein the preferred organic solvent includes but is not limited to tetraethylene glycol dimethyl ether, triethylene glycol dimethyl ether or a combination thereof; and the preferred fluorine-containing organic lithium salt includes but is not limited to lithium bis(trifluoromethanesulfonyl imide), lithium bis(fluorosulfonyl imide) or a combination thereof.

[0041] It should be noted that the specific ratio of the organic solvent and the fluorine-containing organic lithium salt is not particularly limited in this application, and the ratio is based on the ability to obtain a lithium salt electrolyte with good lithium ion conductivity. For example, the embodiment of this application selects tetraethylene glycol dimethyl ether and lithium bis(trifluoromethanesulfonyl)imide in a molar ratio of 1:1.

[0042] In possible public examples, the single-ion conducting solid polymer electrolyte membrane has a thickness of 20~120µm, which can not only effectively inhibit lithium dendrite penetration, but also achieve the effect of unidirectional lithium ion transmission and increased lithium ion migration number, effectively avoid interfacial concentration polarization, reduce battery internal resistance and improve high-voltage stability, give lithium metal batteries high energy density, and provide guarantees for long-term stable circulation of lithium metal batteries.

[0043] In a second aspect, the present invention also provides a method for preparing a single ion conducting solid polymer electrolyte membrane according to the present invention, comprising the steps of:

[0044] Preparation of polymer electrospun membranes;

[0045] After the polymer electrospinning membrane is fully infiltrated by the precursor solution, a photocrosslinking reaction is initiated to obtain a single ion conducting solid polymer electrolyte membrane.

[0046] Among them, the preparation method provided by the embodiment of the present invention can accurately construct a single-ion conductive solid polymer electrolyte membrane by directly initiating a photopolymerization reaction after fully infiltrating the polymer electrospinning membrane with a precursor solution. It is simple to operate, has controllable parameters, and is easy to prepare on an industrial scale.

[0047] It should be noted that in order to achieve a photo-initiated cross-linking reaction, the above precursor solution should also contain a photoinitiator. This application does not specifically limit the photoinitiator and its amount, and is based on the ability to initiate polymerization of fluorinated acrylates, alkenyl borate compounds and cross-linking agents. Possible photoinitiators include but are not limited to 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. The amount added is 1 to 3% of the sum of the mass of the alkenyl borate compound, the fluorinated acrylate monomer and the cross-linking agent.

[0048] It should be noted that the present application does not have any special restrictions on the specific operation of fully infiltrating the polymer electrospinning membrane with the precursor solution, as long as the pores and outer surface of the polymer electrospinning membrane can be fully infiltrated by the precursor solution. For example, in the embodiment of the present application, the precursor solution can be dripped onto the polymer electrospinning membrane, and then a scraper is used for scraping and infiltration. The present application does not limit the parameters of scraping and infiltration. The available scraper specifications are 10~120µm, and the infiltration time is 0~5min.

[0049] In a possible disclosed example, when a precursor solution is used to infiltrate a polymer electrospun membrane, the mass area ratio of the precursor solution to the polymer electrospun membrane is (0.5-1) g: (15-50) cm 2 , the optional mass area ratio is 0.5g:33cm 2 、0.8g:33cm 2 、1g:33cm 2 、0.5g:15cm 2 、0.5g:50cm 2 、0.8g:15cm 2 、0.8g:50cm 2 wait.

[0050] In a possible disclosed example, the electrospinning parameters for preparing a polymer electrospinning membrane may preferably be: voltage of 15-20 kV, distance from needle tip to receiver of 10-15 cm, drum speed of 500-1000 rpm, and solution pushing rate of 0.96-1.44 mL / h.

[0051] It should be noted that the present invention controls the electrospinning parameters to effectively regulate the fiber size of the polymer electrospinning membrane, thereby preparing an electrospinning membrane with suitable pores, providing a basis for introducing solid polymer electrolytes and accurately constructing a network interpenetrating structure.

[0052] Thirdly, embodiments of the present application further provide a lithium battery comprising a positive electrode, a lithium negative electrode, and a single-ion conductive solid polymer electrolyte membrane positioned between the positive and negative electrodes. The positive electrode may utilize lithium iron phosphate, lithium cobalt oxide, or lithium nickel cobalt manganese oxide active materials, and the negative electrode may utilize a lithium sheet.

[0053] It should be noted that, since the single-ion conducting solid polymer electrolyte membrane of the present invention has the characteristics of high energy density and interface stability, it can give lithium batteries the advantages of high energy density and good cycle stability.

[0054] The technical solution of this application will be further explained below in conjunction with specific embodiments.

[0055] Example 1

[0056] This embodiment provides a method for preparing a single ion conducting solid polymer electrolyte membrane SICC-SEM1, and the specific steps are as follows:

[0057] S1: 0.8g (10wt%) of molecular weight Mn=1.5×10 5 Polyacrylonitrile (PAN) was dissolved in N,N-dimethylformamide (DMF) solution and stirred at room temperature for 4 h, then 0.08 g (1 wt %) of carboxymethyl cellulose was added and stirred at room temperature for 1 h to prepare a spinning solution. An electrospinning membrane ESM1 was prepared by an electrospinning method at a spinning voltage of 20 kV, a distance from the needle tip to the receiver of 10 cm, a drum speed of 1000 rpm, and a solution pushing rate of 1.26 mL / h.

[0058] S2: In an argon-filled glove box, 0.3742 g (46.78 wt%) of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), 0.2898 g (36.22 wt%) of tetraethylene glycol dimethyl ether (G4), 0.016 g (2 wt%) of a vinyl borate compound (PBMA, Formula 1), 0.08 g (10 wt%) of trifluoroethyl methacrylate (TFEMA), 0.008 g (1 wt%) of ethoxylated trimethylolpropane triacrylate (ETPTA), 0.032 g (4 wt%) of N,N'-methylenebisacrylamide (MBA) and 0.0041 g of a photoinitiator were stirred and mixed until completely dissolved to obtain a precursor solution SPEPS1;

[0059] S3: Use a dropper to draw 0.8g of precursor solution SPEPS1 and drop it on an area of ​​33cm 2After being coated on the electrospun membrane ESM1, a 90µm scraper was used to fully spread and infiltrate for 3 minutes, and then transferred to a UV lamp for UV free radical polymerization for 15 minutes to obtain a single ion conducting solid polymer electrolyte membrane SICC-SEM1. Figure 1 As shown. Among them, Figure 1 A digital photograph of SICC-SEM1 is shown.

[0060] according to Figure 1 It can be seen that the single ion conducting solid polymer electrolyte membrane was successfully prepared in this embodiment, and the single ion conducting solid polymer electrolyte membrane has good flexibility.

[0061] Example 2

[0062] This embodiment provides a method for preparing a single ion conducting solid polymer electrolyte membrane SICC-SEM2, the specific steps of which are as follows:

[0063] S1: 0.8g (10wt%) of molecular weight Mn=1.5×10 5 Polyacrylonitrile (PAN) was dissolved in N,N-dimethylformamide (DMF) solution and stirred at room temperature for 4 h, then 0.4 g (5 wt %) of carboxymethyl cellulose was added and stirred at room temperature for 1 h to prepare a spinning solution. An electrospinning membrane ESM2 was prepared by an electrospinning method at a spinning voltage of 20 kV, a distance from the needle tip to the receiver of 10 cm, a drum speed of 1000 rpm, and a solution pushing rate of 1.26 mL / h.

[0064] S2: Prepare precursor solution SPEPS1 (same as in Example 1);

[0065] S3: Use a dropper to draw 0.8g of precursor solution SPEPS1 and drop it on an area of ​​33cm 2 After being coated on the electrospun membrane ESM2, a 90µm scraper was used to fully spread and infiltrate for 3 minutes, and then transferred to a UV lamp for UV free radical polymerization for 15 minutes to obtain a single ion conducting solid polymer electrolyte membrane SICC-SEM2.

[0066] Example 3

[0067] This embodiment provides a method for preparing a single ion conducting solid polymer electrolyte membrane SICC-SEM3, and the specific steps are as follows:

[0068] S1: 0.8g (10wt%) of molecular weight Mn=1.5×10 5Polyacrylonitrile (PAN) was dissolved in N,N-dimethylformamide (DMF) solution and stirred at room temperature for 4 h, then 0.8 g (10 wt %) of carboxymethyl cellulose was added and stirred at room temperature for 1 h to prepare a spinning solution. An electrospinning membrane ESM3 was prepared by an electrospinning method at a spinning voltage of 20 kV, a needle tip to receiver distance of 10 cm, a drum speed of 1000 rpm, and a solution push rate of 1.26 mL / h.

[0069] S2: Prepare precursor solution SPEPS1 (same as in Example 1);

[0070] S3: Use a dropper to draw 0.8g of precursor solution SPEPS1 and drop it on an area of ​​33cm 2 After being coated on the electrospun membrane ESM3, a 90µm scraper was used to fully scrape and infiltrate for 3 minutes, and then transferred to a UV lamp for UV free radical polymerization for 15 minutes to obtain a single ion conducting solid polymer electrolyte membrane SICC-SEM3.

[0071] Example 4

[0072] This embodiment provides a method for preparing a single ion conducting solid polymer electrolyte membrane SICC-SEM4, and the specific steps are as follows:

[0073] S1: Preparation of electrospun membrane ESM1 (same as in Example 1);

[0074] S2: In an argon-filled glove box, 0.3607 g (45.09 wt%) of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), 0.2793 g (34.91 wt%) of tetraethylene glycol dimethyl ether (G4), 0.04 g (5 wt%) of a polyvinyl borate compound (PBMA, Formula 1), 0.08 g (10 wt%) of trifluoroethyl methacrylate (TFEMA), 0.008 g (1 wt%) of ethoxylated trimethylolpropane triacrylate (ETPTA), 0.032 g (4 wt%) of N,N'-methylenebisacrylamide (MBA) and 0.0048 g of a photoinitiator were stirred and mixed until completely dissolved to obtain a precursor solution SPEPS2;

[0075] S3: Use a dropper to draw 0.8g of precursor solution SPEPS2 and drop it on an area of ​​33cm 2 After being coated on the electrospun membrane ESM1, a 90µm scraper was used to fully spread and infiltrate for 3 minutes, and then transferred to a UV lamp for UV free radical polymerization for 15 minutes to obtain a single ion conducting solid polymer electrolyte membrane SICC-SEM4.

[0076] Example 5

[0077] This embodiment provides a method for preparing a single ion conducting solid polymer electrolyte membrane SICC-SEM5, and the specific steps are as follows:

[0078] S1: Preparation of electrospun membrane ESM1 (same as in Example 1);

[0079] S2: In an argon-filled glove box, 0.3742 g (46.78 wt%) of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), 0.2898 g (36.22 wt%) of tetraethylene glycol dimethyl ether (G4), 0.016 g (2 wt%) of a boronate compound (PBMA, Formula 1), 0.08 g (10 wt%) of trifluoroethyl methacrylate (TFEMA), 0.032 g (4 wt%) of ethoxylated trimethylolpropane triacrylate (ETPTA), 0.008 g (1 wt%) of N,N'-methylenebisacrylamide (MBA) and 0.0041 g of a photoinitiator were stirred and mixed until completely dissolved to obtain a precursor solution SPEPS3;

[0080] S3: Use a dropper to draw 0.8g of precursor solution SPEPS3 and drop it on an area of ​​33cm 2 After being coated on the electrospun membrane ESM1, a 90µm scraper was used to fully scrape and infiltrate for 3 minutes, and then transferred to a UV lamp for UV free radical polymerization for 15 minutes to obtain a single ion conducting solid polymer electrolyte membrane SICC-SEM5.

[0081] Example 6

[0082] This embodiment provides a method for preparing a single ion conducting solid polymer electrolyte membrane SICC-SEM6, and the specific steps are as follows:

[0083] S1: Prepare electrospun membrane ESM1 (same as Example 1);

[0084] S2: Prepare precursor solution SPEPS1 (same as in Example 1);

[0085] S3: Use a dropper to draw 0.5g of precursor solution SPEPS1 and drop it on an area of ​​33cm 2 After being coated on the electrospun membrane ESM1, a 90µm scraper was used to fully scrape and infiltrate for 3 minutes, and then transferred to a UV lamp for UV free radical polymerization for 15 minutes to obtain a single ion conducting solid polymer electrolyte membrane SICC-SEM6.

[0086] Example 7

[0087] This embodiment provides a method for preparing a single ion conducting solid polymer electrolyte membrane SICC-SEM7, and the specific steps are as follows:

[0088] S1: Prepare electrospun membrane ESM1 (same as Example 1);

[0089] S2: Prepare precursor solution SPEPS1 (same as in Example 1);

[0090] S3: Use a dropper to draw 0.8g of precursor solution SPEPS1 and drop it on an area of ​​33cm 2 After being coated on the electrospun membrane ESM1, a 25µm scraper was used to fully spread and infiltrate for 3 minutes, and then transferred to a UV lamp for UV free radical polymerization for 15 minutes to obtain a single ion conducting solid polymer electrolyte membrane SICC-SEM7.

[0091] In order to illustrate the practical effect of the technical solution of this application, this application also provides comparative examples 1 to 3.

[0092] Comparative Example 1

[0093] This comparative example provides a method for preparing a liquid electrolyte LE / ESM1, and the specific steps are as follows:

[0094] S1: Preparation of electrospun membrane ESM1 (same as in Example 1);

[0095] S2: In an argon-filled glove box, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and tetraethylene glycol dimethyl ether (G4) were stirred and mixed to obtain a liquid electrolyte LE.

[0096] S3: Use a dropper to draw 0.8g of liquid electrolyte LE and drop it on an area of ​​33cm 2 After being deposited on the electrospun membrane ESM1, a 90µm scraper was used to fully spread and infiltrate for 3 minutes to obtain the liquid electrolyte LE / ESM1.

[0097] Comparative Example 2

[0098] This comparative example provides a method for preparing a solid polymer electrolyte membrane SPEM1, and the specific steps are as follows:

[0099] S1: In an argon-filled glove box, 0.3833 g (47.91 wt%) of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), 0.2967 g (37.09 wt%) of tetraethylene glycol dimethyl ether (G4), 0.08 g (10 wt%) of trifluoroethyl methacrylate (TFEMA), 0.008 g (1 wt%) of ethoxylated trimethylolpropane triacrylate (ETPTA), 0.032 g (4 wt%) of N,N'-methylenebisacrylamide (MBA) and 0.0036 g of photoinitiator were stirred and mixed until completely dissolved to obtain a precursor solution SPEPS4;

[0100] S2: Use a dropper to draw 0.8g of precursor solution SPEPS4 and drop it on an area of ​​33cm 2 After being coated with a 90µm scraper in a solid electrolyte mold, it was transferred to a UV lamp for 15 minutes of UV free radical polymerization to obtain a solid polymer electrolyte membrane SPEM1.

[0101] Comparative Example 3

[0102] This comparative example provides a method for preparing a solid polymer electrolyte membrane SPEM2, and the specific steps are as follows:

[0103] S1: In an argon-filled glove box, 0.3742 g (46.78 wt%) of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), 0.2898 g (36.22 wt%) of tetraethylene glycol dimethyl ether (G4), 0.016 g (2 wt%) of an alkenyl borate compound (AAPE, Formula 2), 0.08 g (10 wt%) of trifluoroethyl methacrylate (TFEMA), 0.008 g (1 wt%) of ethoxylated trimethylolpropane triacrylate (ETPTA), 0.032 g (4 wt%) of N,N'-methylenebisacrylamide (MBA) and 0.0041 g of a photoinitiator were stirred and mixed until completely dissolved to obtain a precursor solution SPEPS5;

[0104] S2: Use a dropper to draw 0.8g of precursor solution SPEPS5 and drop it on an area of ​​33cm 2 After being coated with a 90µm scraper in a solid electrolyte mold, the membrane was transferred to a UV lamp for 15 minutes of UV free radical polymerization to obtain a solid polymer electrolyte membrane SPEM2; wherein,

[0105] Formula 2.

[0106] Test Example 1

[0107] In an argon-filled glove box, SICC-SEM1 was placed between two stainless steel sheets (SS) and sealed to form a SS|SICC-SEM1|SS symmetrical cell. The impedance spectroscopy test of the SS|SICC-SEM1|SS symmetrical cell was performed using an electrochemical workstation at 25°C. The results were: Figure 2 As shown. Among them, Figure 2 Electrochemical impedance spectrum of the SS|SICC-SEM1|SS symmetric battery.

[0108] according to Figure 2 It can be seen that the electrochemical impedance of the SS|SICC-SEM1|SS symmetric battery is small, and its ionic conductivity is calculated to be 2.22×10 -3 S / cm.

[0109] Test Example 2

[0110] Stainless steel (SS) and lithium metal (Li) were used as electrodes. In an argon-filled glove box, SICC-SEM1 was placed between the electrodes and sealed to form a Li|SICC-SEM1|SS battery. Using an electrochemical workstation, a linear sweep voltammetry curve test of the Li|SICC-SEM1|SS battery was performed at 25°C. The results were as follows: Figure 3 As shown. Among them, Figure 3 Linear sweep voltammetry curve of Li|SICC-SEM1|SS battery.

[0111] according to Figure 3 It can be seen that the oxidation stability potential of the Li|SICC-SEM1|SS battery can reach 5.2 V, indicating that SICC-SEM1 exhibits excellent electrochemical stability.

[0112] Test Example 3

[0113] Lithium metal (Li) was used as the electrode. In an argon-filled glove box, SICC-SEM1 was placed between the electrodes and sealed to form a Li|SICC-SEM1|Li symmetric cell. Steady-state current polarization tests and impedance spectroscopy tests before and after polarization were performed on the Li|SICC-SEM1|Li symmetric cell at 25°C using an electrochemical workstation. The results were as follows: Figure 4 As shown. Among them, Figure 4 The current / time test curve of the Li|SICC-SEM1|Li symmetric battery and the impedance test curve before and after polarization.

[0114] according to Figure 4 It can be seen that SICC-SEM1 exhibits a lithium ion transfer number of 0.75, and the resistance of the electrolyte membrane changes little before and after polarization, while the semicircle of the curve does not change much, indicating that SICC-SEM1 can effectively suppress anion migration and concentration polarization.

[0115] Test Example 4

[0116] Lithium metal (Li) was used as the electrode. In an argon-filled glove box, SICC-SEM1 was placed between the electrodes and sealed to form a Li|SICC-SEM1|Li symmetric battery. The Li|SICC-SEM1|Li symmetric battery was tested at 0.1 mA·cm at 25°C. -2 The constant current test was carried out at a current density of Figure 5 As shown. Among them, Figure 5 For Li|SICC-SEM1|Li symmetric cell at 0.1 mA·cm -2 Constant current test diagram under current density.

[0117] according to Figure 5 It can be seen that the Li|SICC-SEM1|Li symmetric battery is -2 Lithium plating / stripping was carried out for 2000 h at a current density of 1.5 Å, indicating that the use of SICC-SEM1 in Li||Li symmetric batteries can not only reduce concentration polarization, but also inhibit the growth of lithium dendrites.

[0118] Test Example 5

[0119] Lithium iron phosphate (LFP) was used as the positive electrode and lithium metal (Li) as the negative electrode. In an argon-filled glove box, SICC-SEM1 was placed between the positive and negative electrodes and sealed to form an LFP|SICC-SEM1|Li battery. The LFP|SICC-SEM1|Li battery was subjected to constant current charge and discharge tests at a rate of 0.5C at 25°C (the test voltage range was 2.5~4V). The results were as follows: Figure 6 As shown. Among them, Figure 6 This is the cycle diagram of LFP|SICC-SEM1|Li battery at 0.5C.

[0120] according to Figure 6 It can be seen that the LFP|SICC-SEM1|Li battery has been stably cycled for 500 cycles at a rate of 0.5C. At the same time, the initial discharge capacity of the LFP|SICC-SEM1|Li battery at a rate of 0.5C is 146 mAh g -1 The discharge capacity after 500 cycles is 143.6 mAh g -1 The capacity retention rate is 98.4% and the coulombic efficiency is above 99%, indicating that SICC-SEM1 can exhibit excellent cycling stability when used in LFP||Li batteries.

[0121] Test Example 6

[0122] Nickel cobalt manganese oxide 811 (NCM811) was used as the positive electrode and lithium metal (Li) was used as the negative electrode. In an argon-filled glove box, SICC-SEM1 was placed between the positive and negative electrodes and sealed to form an NCM811|SICC-SEM1|Li battery. The NCM811|SICC-SEM1|Li battery was subjected to constant current charge and discharge tests at a rate of 0.5C at 25°C (the test voltage range was 2.8~4.3V). The results were as follows: Figure 7 As shown. Among them, Figure 7 This is the cycle diagram of NCM811|SICC-SEM1|Li battery at 0.5C.

[0123] according to Figure 7It can be seen that the NCM811|SICC-SEM1|Li battery cycled stably for 200 cycles at a rate of 0.5C. At the same time, the initial discharge capacity of the NCM811|SICC-SEM1|Li battery at a rate of 0.5C was 211.7 mAh g -1 The discharge capacity after 200 cycles is 178.4 mAh g -1 The capacity retention rate is 84.3% and the coulombic efficiency is above 99%, indicating that SICC-SEM1 has excellent cycling stability for NCM811||Li batteries.

[0124] Test Example 7

[0125] Lithium metal (Li) was used as the electrode. In an argon-filled glove box, LE / ESM1 was placed between the electrodes and sealed to form a Li|LE / ESM1|Li symmetrical cell. Using an electrochemical workstation, steady-state current polarization tests and impedance spectroscopy tests before and after polarization were performed on the Li|LE / ESM1|Li symmetrical cell at 25°C. The results were as follows: Figure 8 As shown. Among them, Figure 8 The current / time test curve of the Li|LE / ESM1|Li symmetric battery and the impedance test curve before and after polarization.

[0126] According to Figure 8, LE / ESM1 only exhibits a lithium ion migration number of 0.42, which is much lower than 0.75 of SICC-SEM1, indicating that the solid polymer electrolyte of the present application can effectively suppress the migration number of anions by compounding the solid polymer electrolyte of the present application into the pores and outer surfaces of the polymer electrospinning membrane.

[0127] Test Example 8

[0128] Nickel cobalt manganese oxide 811 (NCM811) was used as the positive electrode and lithium metal (Li) was used as the negative electrode. In an argon-filled glove box, LE / ESM1 was placed between the positive and negative electrodes and sealed to form an NCM811|LE / ESM1|Li battery. The NCM811|LE / ESM1|Li battery was subjected to a constant current charge and discharge test at 0.5C rate (test voltage range 2.8~4.3V) at 25℃. The results were as follows: Figure 9 As shown. Among them, Figure 9 This is the cycle diagram of NCM811|LE / ESM1|Li battery at 0.5C.

[0129] according to Figure 9 It can be seen that after 50 cycles of the NCM811|LE / ESM1|Li battery, the coulombic efficiency is significantly reduced and the battery fails.

[0130] Test Example 9

[0131] Lithium metal (Li) was used as the electrode. In an argon-filled glove box, SPEM1 was placed between the electrodes and sealed to form a Li|SPEM1|Li symmetrical cell. Using an electrochemical workstation, steady-state current polarization tests and impedance spectroscopy tests before and after polarization were performed on the Li|SPEM1|Li symmetrical cell at 25°C. The results were as follows: Figure 10 As shown. Among them, Figure 10 The current / time test curve of the Li|SPEM1|Li symmetric battery and the impedance test curve before and after polarization.

[0132] according to Figure 10 It can be seen that SPEM1 only exhibits a lithium ion transference number of 0.42, which is much lower than 0.75 of SICC-SEM1, indicating that the solid polymer electrolyte membrane without the alkenyl borate compound of Formula 1 cannot effectively inhibit anion migration.

[0133] Test Example 10

[0134] Nickel cobalt manganese oxide 811 (NCM811) was used as the positive electrode and lithium metal (Li) was used as the negative electrode. In an argon-filled glove box, SPEM1 was placed between the positive and negative electrodes and sealed to form an NCM811|SPEM1|Li battery. The NCM811|SPEM1|Li battery was subjected to constant current charge and discharge tests at 0.5C rate (test voltage range 2.8~4.3V) at 25℃. The results were as follows: Figure 11 As shown. Among them, Figure 11 This is the cycle diagram of NCM811|SPEM1|Li battery at 0.5C.

[0135] according to Figure 11 It can be seen that the initial discharge capacity of NCM811|SPEM1|Li battery at 0.5C rate is 193.6mAh·g -1 The discharge capacity after 200 cycles is 140.2 mAh g -1 , the capacity retention rate is 72.42%, and its cycle performance is relatively poor compared with that of NCM811|SICC-SEM1|Li battery.

[0136] Test Example 11

[0137] Lithium metal (Li) was used as the electrode. In an argon-filled glove box, a single-ion conducting solid polymer electrolyte membrane SPEM2 was placed between the electrodes and sealed to form a Li|SPEM2|Li symmetric cell. Using an electrochemical workstation, steady-state current polarization tests and impedance spectroscopy tests before and after polarization were performed on the Li|SPEM2|Li symmetric cell at 25°C. The results were as follows: Figure 12 shown. Figure 12The current / time test curve of the Li|SPEM2|Li symmetric battery and the impedance test curve before and after polarization.

[0138] according to Figure 12 It can be seen that SPEM2 exhibits a lithium ion transference number of 0.59, indicating that SPEM2 also has the effect of inhibiting anion migration and concentration polarization, but it is worse than SICC-SEM1.

[0139] Test Example 12

[0140] Nickel cobalt manganese oxide 811 (NCM811) was used as the positive electrode and lithium metal (Li) was used as the negative electrode. In an argon-filled glove box, SPEM2 was placed between the positive and negative electrodes and sealed to form an NCM811|SPEM2|Li battery. The NCM811|SPEM2|Li battery was subjected to constant current charge and discharge tests at a rate of 0.5C at 25°C (the test voltage range was 2.8~4.3V). The results were as follows: Figure 13 As shown. Among them, Figure 13 This is the cycle diagram of NCM811|SPEM2|Li battery at 0.5C.

[0141] according to Figure 13 It can be seen that the NCM811|SPEM2|Li battery has been stably cycled for 150 cycles at a rate of 0.5C. At the same time, the initial discharge capacity of the NCM811|SPEM2|Li battery at a rate of 0.5C is 191.5mAh·g -1 The discharge capacity after 150 cycles is 144 mAh g -1 The capacity retention rate is 75.2% and the coulombic efficiency is above 99%, indicating that although SPEM2 also exhibits excellent cycling stability when used in NCM811||Li batteries, it is still inferior to SICC-SEM1.

[0142] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0143] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit the present application. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments can still be modified, or some or all of the technical features therein can be replaced by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present application.

Claims

1. A single ion conducting solid polymer electrolyte membrane, characterized in that: comprising a polymer electrospun membrane; The pores and outer surfaces of the polymer electrospinning membrane are compounded with a solid polymer electrolyte, and the precursor solution of the solid polymer electrolyte contains the following components: (a) 1-5 wt% of an alkenyl borate compound; (b) 5-10 wt% of a fluorinated acrylate monomer; (c) 1-5 wt% cross-linking agent; (d) the balance lithium salt electrolyte.

2. The single ion conducting solid polymer electrolyte membrane according to claim 1, wherein: The material components of the polymer electrospinning membrane include a spinnable polymer and carboxyl cellulose; The mass ratio of the spinnable polymer to the carboxyl cellulose is 100:(10-20).

3. The single ion conducting solid polymer electrolyte membrane according to claim 2, wherein: The spinnable polymer is selected from at least one of polyacrylonitrile, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polymethacrylate, polyimide and polyacrylamide; And / or, the carboxycellulose is at least one selected from carboxymethyl cellulose, carboxyethyl cellulose and carboxypropyl cellulose.

4. The single ion conducting solid polymer electrolyte membrane according to claim 1, wherein: The alkenyl borate compound is represented by Formula 1: Formula 1; and / or, the fluorine-containing acrylate monomer is at least one selected from trifluoroethyl methacrylate, 2,2,3,3,3-pentafluoropropyl methacrylate, and 2,2,3,3,4,4,4-heptafluorobutyl methacrylate; And / or, the crosslinking agent is selected from ethoxylated trimethylolpropane triacrylate and N,N' - at least one of methylenebisacrylamide; and / or, the lithium salt electrolyte comprises an organic solvent and a fluorine-containing organic lithium salt; The organic solvent is selected from at least one of tetraethylene glycol dimethyl ether and triethylene glycol dimethyl ether; The fluorine-containing organic lithium salt is selected from at least one of lithium bis(trifluoromethanesulfonyl)imide and lithium bis(fluorosulfonyl)imide.

5. The single ion conducting solid polymer electrolyte membrane according to claim 4, characterized in that: The cross-linking agent is selected from N,N' - A combination of methylene bisacrylamide and ethoxylated trimethylolpropane triacrylate in a mass ratio of 1:(0.25~4).

6. The single ion conducting solid polymer electrolyte membrane according to any one of claims 1 to 5, characterized in that: The thickness of the single ion conductive solid polymer electrolyte membrane is 20-120 μm.

7. A method for preparing a single ion conducting solid polymer electrolyte membrane according to any one of claims 1 to 6, comprising: Preparation of polymer electrospun membranes; After the polymer electrostatic spinning membrane is fully infiltrated by the precursor solution, a photo-crosslinking polymerization reaction is initiated to obtain a single ion conducting solid polymer electrolyte membrane.

8. The preparation method according to claim 7, characterized in that: When the precursor solution is used to infiltrate the polymer electrospinning membrane, the mass area ratio of the precursor solution to the polymer electrospinning membrane is (0.5-1) g: (15-50) cm 2 .

9. The preparation method according to claim 7, characterized in that: The electrospinning parameters for preparing the polymer electrospinning membrane include: voltage of 15-20 kV, distance from needle tip to receiver of 10-15 cm, drum speed of 500-1000 rpm, and solution pushing rate of 0.96-1.44 mL / h.

10. A lithium battery, characterized in that: The invention comprises the single ion conducting solid polymer electrolyte membrane according to any one of claims 1 to 6.

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