An isolated ion-conducting solid-state polymer electrolyte membrane and a preparation method thereof, and a lithium battery

Abstract

The application discloses a single-ion-conducting solid-state polymer electrolyte film and a preparation method thereof and a lithium battery, and belongs to the solid-state polymer electrolyte field.The single-ion-conducting solid-state polymer electrolyte film comprises a polymer electrostatic spinning film, the inside of pores of the polymer electrostatic spinning film and the outer surface of the polymer electrostatic spinning film are both compounded with a solid-state polymer electrolyte, a precursor solution of the solid-state polymer electrolyte contains 1-5 wt% of an alkenyl borate compound, 5-10 wt% of a fluorine-containing acrylic ester monomer, 1-5 wt% of a crosslinking agent and a residual amount of a lithium salt electrolyte.The application effectively decouples the restraint relationship between the mechanical strength and the lithium ion conductivity of the solid-state polymer electrolyte, the performance of the solid-state polymer electrolyte film is synergistically enhanced, the migration number of 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 long-term stable cycle of the lithium battery can be ensured.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of solid-state polymer electrolyte, and particularly relates to a single-ion-conducting solid-state polymer electrolyte film, a preparation method thereof and a lithium battery. BACKGROUND

[0002] Lithium metal batteries have become one of the best candidates for long-range electric vehicles and portable electronic device energy storage fields due to their high energy density. However, the liquid electrolyte used in traditional lithium metal batteries is prone to chemical reaction with lithium metal, which leads to safety problems and reduces the cycle life of lithium metal batteries. Therefore, inhibiting the chemical reaction between the electrolyte and lithium metal is of great concern.

[0003] Solid-state polymer electrolytes can fundamentally reduce the reaction with lithium metal, making lithium metal batteries have higher cycle efficiency and safety performance, and have become the main research direction to promote the commercial application of lithium metal batteries. However, most of the existing solid-state polymer electrolytes are double-ion conductors. Since lithium ions and anions migrate in both directions, it can cause interfacial concentration polarization, resulting in low lithium ion transference number, higher internal resistance and discharge voltage, and poor long-term stable cycle performance of lithium metal batteries.

[0004] Therefore, how to improve the transference number of lithium ions and avoid interfacial concentration polarization to ensure the cycle stability of lithium metal batteries has become a problem to be solved in the field. SUMMARY

[0005] The application discloses a single-ion-conducting solid-state polymer electrolyte film, a preparation method thereof and a lithium battery, which effectively solve the technical problems of low lithium ion transference number and high battery internal resistance and discharge voltage of the existing solid-state polymer electrolyte film.

[0006] In order to achieve the above purpose, the technical scheme adopted by the application is:

[0007] The first aspect of the application provides a single-ion-conducting solid-state polymer electrolyte film, and the single-ion-conducting solid-state polymer electrolyte film comprises a polymer electrospun film.

[0008] The solid-state polymer electrolyte is compounded in the pores and the outer surface of the polymer electrospun film, and the precursor solution of the solid-state polymer electrolyte comprises the following components:

[0009] (a) 1-5 wt% of an alkenyl borate compound; (b) 5-10 wt% of a fluorine-containing acrylic ester monomer;

[0010] (c) 1-5 wt% of a crosslinking agent; (d) the rest of a lithium salt electrolyte.

[0011] According to the first aspect, the material composition of the polymer electrospun membrane comprises a spinnable polymer and carboxyl cellulose;

[0012] The mass ratio of the spinnable polymer to the carboxyl cellulose is 100:(10~20).

[0013] According to the first aspect, the spinnable polymer is selected from at least one of polyacrylonitrile, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polymethacrylate, polyimide and polyacrylamide.

[0014] And / or, the carboxyl cellulose is selected from at least one of carboxymethyl cellulose, carboxyethyl cellulose and carboxypropyl cellulose.

[0015] According to the first aspect, the alkenyl borate compound is shown in formula 1:

[0016] Formula 1;

[0017] And / or, the fluorine-containing acrylate monomer is selected from at least one of trifluoroethyl methacrylate, 2,2,3,3,3-pentafluoropropyl methacrylate and 2,2,3,3,4,4,4-heptafluorobutyl methacrylate;

[0018] And / or, the crosslinking agent is selected from at least one of methylene bisacrylamide and ethoxylated trimethylolpropane triacrylate; N,N'

[0019] And / or, the lithium salt electrolyte comprises an organic solvent and a fluorine-containing organic lithium salt;

[0020] The organic solvent is selected from at least one of tetraethylene glycol dimethyl ether and triethylene glycol dimethyl ether;

[0021] The fluorine-containing organic lithium salt is selected from at least one of lithium bis(trifluoromethanesulfonyl)imide and lithium bis(fluorosulfonyl)imide.

[0022] According to the first aspect, the crosslinking agent is selected as N,N' Methylene bisacrylamide and ethoxylated trimethylolpropane triacrylate in a mass ratio of 1:(0.25~4).

[0023] According to the first aspect, the thickness of the single-ion conductor solid-state polymer electrolyte membrane is 20~120µm.

[0024] The second aspect of the present application further discloses a preparation method of the single-ion conducting solid-state polymer electrolyte membrane described above, the steps of which comprise:

[0025] Preparation of a polymer electrospun membrane;

[0026] ​After the polymer electrospun membrane is sufficiently infiltrated by the precursor solution, a photo-crosslinking polymerization reaction is initiated, thereby obtaining the single-ion-conducting solid-state polymer electrolyte membrane.

[0027] According to the second aspect, when the polymer electrospun membrane is infiltrated by the precursor solution, the mass area ratio of the precursor solution to the polymer electrospun membrane is (0.5-1) g :(15-50) cm 2 .

[0028] According to the second aspect, the electrospinning parameters for preparing the polymer electrospun membrane include: a voltage of 15-20 kV, a distance from the needle tip to the receiver of 10-15 cm, a roller rotation speed of 500-1000 rpm, and a solution pushing rate of 0.96-1.44 mL / h.

[0029] The third aspect of the present application further discloses a lithium battery comprising the single-ion-conducting solid-state polymer electrolyte membrane.

[0030] Compared with the prior art, the advantages or beneficial effects of the present application at least include:

[0031] The single-ion-conducting solid-state polymer electrolyte membrane provided by the present application effectively decouples the mechanical strength of the solid-state polymer electrolyte and the lithium ion conductivity by arranging the solid-state polymer electrolyte based on the precursor components and filling the solid-state polymer electrolyte in the pores of the polymer electrospun membrane and covering the outer surface thereof, so that the performance of the prepared solid-state polymer electrolyte membrane is synergistically enhanced, the number of lithium ion migration is greatly improved, the concentration polarization is effectively inhibited, the internal resistance is reduced, and the high-voltage stability is improved, thereby ensuring the long-term stable cycle of the lithium battery. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments described in the present application, and those skilled in the art can also obtain other drawings according to these drawings without creating any creative labor.

[0033] Figure 1 The digital photo of SICC-SEM1 provided by the present application;

[0034] Figure 2 The electrochemical impedance spectrum of the S|SICC-SEM1|S symmetric battery provided by the present application;

[0035] Figure 3 The linear sweep voltammetry curve of the Li|SICC-SEM1|S battery provided by the present application;

[0036] Figure 4 Current / time test curve and impedance test curve before and after polarization of Li|SICC-SEM1|Li symmetric battery provided for the present application;

[0037] Figure 5 Constant current test graph of Li|SICC-SEM1|Li symmetric battery provided for the present application at a current density of 0.1 mA·cm -2

[0038] Figure 6 Cycle graph of LFP|SICC-SEM1|Li battery provided for the present application at 0.5C;

[0039] Figure 7 Cycle graph of NCM811|SICC-SEM1|Li battery provided for the present application at 0.5C;

[0040] Figure 8 Current / time test curve and impedance test curve before and after polarization of Li|LE / ESM1|Li symmetric battery provided for the present application;

[0041] Figure 9 Cycle graph of NCM811|LE / ESM1|Li battery provided for the present application at 0.5C;

[0042] Figure 10 Current / time test curve and impedance test curve before and after polarization of Li|SPEM1|Li symmetric battery provided for the present application;

[0043] Figure 11 Cycle graph of NCM811|SPEM1|Li battery provided for the present application at 0.5C;

[0044] Figure 12 Current / time test curve and impedance test curve before and after polarization of Li|SPEM2|Li symmetric battery provided for the present application;

[0045] Figure 13 Cycle graph of NCM811|SPEM2|Li battery provided for the present application at 0.5C. DETAILED DESCRIPTION

[0046] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments described in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.​

[0047] In the following description of the specification, the term "and / or" is used to describe the association relationship of associated objects, which means that there can be three relationships, for example, A and / or B, which can represent the cases of A alone, B alone and A and B existing at the same time. Among them, A and B can be singular or plural; the symbol " / " represents the meaning of "or".

[0048] In the following description of the specification, the term "at least one" means one or more, and "multiple" means two or more. "At least one of the following" or similar expressions means any combination of the items, including any combination of single or multiple items. For example, "at least one of A, B or C", or "at least one of A, B and C", can represent any one of A, B, C, or A+B, or A+C, or B+C, or A+B+C, wherein A, B, C can be single or multiple.

[0049] In the following description of the specification, the order of the serial numbers does not mean the order of execution, and part or all of the steps can be executed in parallel or in sequence, and the execution order of each process should be determined according to its function and internal logic, without any limitation on the execution process of the embodiment.

[0050] In the following description of the specification, the numerical range should be understood as also specifically disclosing each intermediate value between the upper limit and the lower limit of the range. Any intermediate value in the stated range, as well as any other stated value or each smaller range between the intermediate values in the stated range, is also included in the embodiment, and the upper limit and the lower limit of the smaller range can be independently included or excluded from the range.

[0051] Unless otherwise specified, the technical / scientific terms used in the specification have the meanings commonly understood by those skilled in the art. Although only preferred materials and methods are described in the specification, any method and material similar or equivalent to those described in the specific examples or test examples can also be used. All documents mentioned in the specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In the event of conflict with any incorporated document, the content of the specification shall prevail.

[0052] In the most widely studied "salt-in-polymer" type solid-state polymer electrolyte, the diffusion coefficient of lithium ions in the polymer matrix is much lower than that of the unbound anion, resulting in a lithium ion transference number of 0.2~0.3 for the electrolyte system. The low lithium ion transference number will lead to a serious ion concentration gradient and concentration polarization in the battery, resulting in an increase in the working voltage of the battery and a serious interface penetration problem, affecting the cycle life of the lithium metal battery.

[0053] To improve the lithium ion transference number of the solid-state polymer electrolyte, the first aspect of the embodiments of the present application provides a single-ion-conducting solid-state polymer electrolyte film. The single-ion-conducting solid-state polymer electrolyte film of the present application comprises a polymer electrospun membrane, and the pores inside and the outer surface of the polymer electrospun membrane are both compounded with a solid-state polymer electrolyte. The precursor solution of the solid-state polymer electrolyte contains the following components:

[0054] (a) 1-5 wt% of an alkenyl borate compound; (b) 5-10 wt% of a fluorine-containing acrylic ester monomer;

[0055] (c) 1-5 wt% of a crosslinking agent; (d) the rest of a lithium salt electrolyte.

[0056] It should be noted that the pores inside and the outer surface of the polymer electrospun membrane mentioned in the present application are both compounded with a solid-state polymer electrolyte, which means that the solid-state polymer electrolyte is filled in the pores of the polymer electrospun membrane and also covers the outer surface of the polymer electrospun membrane. The solid-state polymer electrolyte is formed by the photopolymerization of its precursor solution.

[0057] The alkenyl borate compound and the fluorine-containing acrylic ester are crosslinked to form a solid-state polymer electrolyte, which can ensure good film formation of the solid-state polymer electrolyte, improve the chain segment mobility, effectively promote the dissociation and conduction of lithium ions from the anion, make the solid-state electrolyte film have high ionic conductivity, and also effectively achieve the single-ion-conduction effect by anchoring the anion based on the crosslinking network and strong coordination effect. In addition, the mechanical properties of the solid-state polymer electrolyte are improved, and the inhibition of lithium dendrite penetration is effectively enhanced. Meanwhile, the solid-state polymer electrolyte is introduced into the pores of the polymer electrospun membrane and covers the outer surface of the polymer electrospun membrane, and the two are mutually synergistic to accurately construct a network interpenetrating structure, effectively decouple the mechanical strength and lithium ion conductivity of the solid-state polymer electrolyte, and form a continuous ion-conducting phase and a mechanically stable phase between the solid-state polymer electrolyte and the polymer electrospun membrane, so that the solid-state polymer electrolyte film exhibits higher lithium ion conductivity and better inhibition of lithium dendrite penetration, thereby effectively avoiding interfacial concentration polarization, reducing the internal resistance of the battery and improving the high-voltage stability, and providing a basis for long-term stable cycling of lithium metal batteries.

[0058] In the possible disclosed examples, the material composition of the polymer electrostatic spinning film of the present application comprises a spinnable polymer and carboxyl cellulose, there is a hydrogen bond interaction between the spinnable polymer and the carboxyl cellulose, and the cross-linking forms a continuous ion conduction phase conducive to lithium ion transmission, further promoting lithium ion transmission. The mass ratio of the spinnable polymer to the carboxyl cellulose is selected as 100:(10-20), including but not limited to 100:10, 100:15, 100:20 or any other value within the mass ratio range.

[0059] In the possible disclosed examples, the spinnable polymer is selected from any one or combination of polyacrylonitrile, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polymethacrylate, polyimide and polyacrylamide; and the carboxyl cellulose is any one or combination of carboxymethyl cellulose, carboxyethyl cellulose and carboxypropyl cellulose. There is a hydrogen bond interaction between the spinnable polymer and the carboxyl cellulose, and the cross-linking forms a polymer network structure with good chain mobility and mechanical strength, which can effectively improve the promotion of lithium ion conduction and effectively inhibit the penetration of lithium dendrites, so that the lithium battery has long-term stable cycle performance.

[0060] In the possible disclosed examples, the alkenyl borate compound of the present application is shown in formula 1:

[0061] Formula 1.

[0062] It should be noted that the alkenyl borate compound containing a benzene ring is selected in the present application, and the benzene ring rigid group not only helps to improve the mechanical properties and thermal stability of the solid-state polymer electrolyte, but also improves the processability of the solid-state polymer electrolyte, thereby supporting the decoupling of the mechanical strength and lithium ion conductivity of the solid-state polymer electrolyte. In addition, the alkenyl borate compound contains a dynamic covalent B-O bond, and the dynamic reversibility endows the cross-linked polymer and the solid-state polymer electrolyte with flexibility and self-healing ability, which can self-repair, inhibit lithium dendrite growth and reduce the damage of lithium dendrite growth to the solid-state polymer electrolyte.

[0063] In the possible disclosed examples, the fluorine-containing acrylic ester 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.

[0064] It should be noted that the fluorine-containing acrylate compounds have strong electron-withdrawing effect, which can reduce the highest occupied molecular orbital (HOMO) energy level of the polymer, and is beneficial to improve the oxidation resistance of the polymer, and can be matched with high-voltage positive electrodes. In addition, the fluorine-containing acrylate can form a LiF-rich inorganic interfacial layer, thereby improving the interfacial stability of the electrolyte / lithium metal negative electrode, promoting uniform lithium deposition / peeling, and effectively inhibiting lithium dendrite growth. In addition, the alkenyl borate compound can form dynamic chemical entanglement with the ester group in the acrylate through its own ester exchange reaction characteristics, which is beneficial to improve the chain movement ability of the polymer matrix of the solid-state polymer electrolyte.

[0065] In the possible disclosed examples, the crosslinking agent is selected to be 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 0.25-4:1.

[0066] It should be noted that when the crosslinking agent is selected to be a combination of ethoxylated trimethylolpropane triacrylate and N,N'-methylenebisacrylamide in a mass ratio of 0.25-4:1, the N,N'-methylenebisacrylamide can provide abundant hydrogen bonds for the crosslinking network, which is beneficial to improve the mechanical strength of the solid-state polymer electrolyte; the ethoxylated trimethylolpropane triacrylate contains a large number of ether oxygen segments, which can provide a lithium ion transport path, and the combination of the two can decouple the mechanical strength of the solid-state polymer electrolyte and the lithium ion conductivity.

[0067] In the possible disclosed examples, the lithium salt electrolyte contains an organic solvent and a fluorine-containing organic lithium salt, and 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.

[0068] It should be noted that the specific ratio of the organic solvent and the fluorine-containing organic lithium salt is not particularly limited in the present application, and can be adjusted according to the lithium ion conductivity of the lithium salt electrolyte, for example, the molar ratio of tetraethylene glycol dimethyl ether and lithium bis(trifluoromethanesulfonyl)imide is 1:1 in the present application.

[0069] In the possible disclosed examples, the single-ion-conducting solid-state polymer electrolyte film has a thickness of 20-120 µm, which can effectively inhibit lithium dendrite puncture, achieve the effects of one-way transport of lithium ions and improvement of lithium ion transference number, effectively avoid interfacial concentration polarization, reduce the internal resistance of the battery and improve the high-voltage stability, and endow the lithium metal battery with high energy density, thereby providing a guarantee for long-term stable cycling of the lithium metal battery.

[0070] In a second aspect, the embodiments of the present application also provide a preparation method of the single-ion-conducting solid-state polymer electrolyte film, which comprises the following steps:

[0071] preparing a polymer electrospun film;

[0072] After the polymer electrospun film is sufficiently infiltrated by the precursor solution, a photo-crosslinking reaction is initiated, and the single-ion-conducting solid-state polymer electrolyte film is obtained.

[0073] In the embodiments of the present application, the preparation method can be used to precisely construct the single-ion-conducting solid-state polymer electrolyte film by directly initiating a photo-polymerization reaction after the polymer electrospun film is sufficiently infiltrated by the precursor solution, and the operation is simple, the parameters are controllable, and the large-scale industrial preparation is easy.

[0074] It should be noted that, in order to achieve the photo-initiated crosslinking reaction, the precursor solution should further comprise a photo-initiator, and the present application does not have special limitations on the photo-initiator and the amount, which should be able to initiate the polymerization of the fluoroacrylate, alkenyl borate ester compound and crosslinking agent, and possible photo-initiators include but are not limited to 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2,4,6-trimethylbenzoyl-diphenyl phosphine oxide, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone, and phenyl bis(2,4,6-trimethylbenzoyl) phosphine oxide, and the amount of the photo-initiator is 1-3% of the sum of the mass of the alkenyl borate ester compound, the fluoroacrylate monomer and the crosslinking agent.

[0075] It should be noted that the present application does not have special limitations on the specific operation of the polymer electrospun film being sufficiently infiltrated by the precursor solution, which should be able to make the pores and the outer surface of the polymer electrospun film be sufficiently infiltrated by the precursor solution, for example, the precursor solution can be drop-coated on the polymer electrospun film, and then a doctor blade is used for scraping and infiltrating, and the present application does not have limitations on the parameters of the scraping and infiltrating, and the available doctor blade specifications are 10-120 µm, and the infiltration time is 0-5 min.

[0076] In the possible disclosed examples, when the polymer electrospun film is infiltrated by the precursor solution, the mass-area ratio of the precursor solution to the polymer electrospun film is (0.5-1) g :(15-50) cm 2 , and the optional mass-area ratio is 0.5 g:33 cm 2 , 0.8 g:33 cm 2 , 1 g:33 cm 2 , 0.5 g:15 cm 2 , 0.5 g:50 cm 2 , 0.8 g:15 cm 2, 0.8 g: 50 cm 2 etc.

[0077] In the possible disclosed examples, the electrospinning parameters for preparing the polymer electrospinning film can be preferably: a voltage of 15-20 kV, a needle tip to receiver distance of 10-15 cm, a drum rotation speed of 500-1000 rpm, and a solution pushing rate of 0.96-1.44 mL / h.

[0078] It should be noted that the control of the electrospinning parameters of the present application can effectively regulate the fiber size of the polymer electrospinning film, thereby preparing an electrospinning film with suitable pores, providing a basis for introducing a solid-state polymer electrolyte and accurately constructing a network interpenetrating structure.

[0079] In a third aspect, the embodiments of the present application also provide a lithium battery, specifically comprising a positive electrode, a lithium negative electrode, and a single-ion-conducting solid-state polymer electrolyte film located between the positive electrode and the lithium negative electrode. The positive electrode can use lithium iron phosphate, lithium cobaltate or nickel-cobalt-manganese acid lithium active material, and the negative electrode uses a lithium sheet.

[0080] It should be noted that the single-ion-conducting solid-state polymer electrolyte film has the characteristics of high energy density and stable interface, thereby imparting the lithium battery with the advantages of high energy density and good cycle stability.

[0081] The technical solutions of the present application will be further described below in combination with specific embodiments.

[0082] Embodiment 1

[0083] The present embodiment provides a preparation method of a single-ion-conducting solid-state polymer electrolyte film SICC-SEM1, and the specific steps are as follows:

[0084] S1: 0.8 g (10 wt%) of polyacrylonitrile (PAN) with a molecular weight of Mn=1.5×10 5 is dissolved in a N,N-dimethylformamide (DMF) solution and stirred at room temperature for 4 h, then 0.08 g (1 wt%) of carboxymethyl cellulose is added and stirred at room temperature for 1 h to prepare a spinning solution; an electrospinning film ESM1 is prepared by an electrospinning method under a spinning voltage of 20 kV, a needle tip to receiver distance of 10 cm, a drum rotation speed of 1000 rpm, and a solution pushing rate of 1.26 mL / h;

[0085] S2: In an argon-filled glove box, 0.3742 g (46.78 wt%) lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), 0.2898 g (36.22 wt%) tetraethylene glycol dimethyl ether (G4), 0.016 g (2 wt%) alkenyl borate compound (PBMA, Formula 1), 0.08 g (10 wt%) trifluoroethyl methacrylate (TFEMA), 0.008 g (1 wt%) ethoxylated trimethylolpropane triacrylate (ETPTA), 0.032 g (4 wt%) N,N'-methylenebisacrylamide (MBA) and 0.0041 g photoinitiator were stirred to be mixed uniformly until completely dissolved to obtain a precursor solution SPEPS1;

[0086] S3: After 0.8 g of the precursor solution SPEPS1 was dropped on the electrospun membrane ESM1 with an area of 33 cm 2 using a dropper, a 90 µm doctor blade was used for sufficient blade coating infiltration for 3 min, and then transferred to the ultraviolet lamp for ultraviolet radical polymerization for 15 min to obtain a single-ion-conducting solid-state polymer electrolyte membrane SICC-SEM1, and the result is shown in Figure 1 . Among them, Figure 1 Fig. 4 shows a digital photo of SICC-SEM1.

[0087] According to Figure 1 it can be seen that the single-ion-conducting solid-state polymer electrolyte membrane is successfully prepared in this embodiment, and the single-ion-conducting solid-state polymer electrolyte membrane has good flexibility.

[0088] Example 2

[0089] This embodiment provides a preparation method of a single-ion-conducting solid-state polymer electrolyte membrane SICC-SEM2, and the specific steps are as follows:

[0090] S1: 0.8 g (10 wt%) polyacrylonitrile (PAN) with a molecular weight of Mn=1.5×10 5 was dissolved in N,N-dimethylformamide (DMF) solution and stirred at room temperature for 4 h, then 0.4 g (5 wt%) carboxymethyl cellulose was added and stirred at room temperature for 1 h to prepare a spinning solution; an electrospun membrane ESM2 was prepared by an electrospinning method, and under the conditions of a spinning voltage of 20 kV, a distance between a needle tip and a receiver of 10 cm, a drum rotating speed of 1000 rpm, and a solution pushing rate of 1.26 mL / h;

[0091] S2: The precursor solution SPEPS1 (same as in Example 1) was prepared;

[0092] S3: 0.8 g of the precursor solution SPEPS1 was dropped on the electrospun membrane ESM1 with an area of 33 cm 2After 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.

[0093] Example 3

[0094] This embodiment provides a method for preparing a single ion conducting solid polymer electrolyte membrane SICC-SEM3, and the specific steps are as follows:

[0095] 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 0.8 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.

[0096] S2: Prepare precursor solution SPEPS1 (same as in Example 1);

[0097] 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.

[0098] Example 4

[0099] This embodiment provides a method for preparing a single ion conducting solid polymer electrolyte membrane SICC-SEM4, and the specific steps are as follows:

[0100] S1: Preparation of electrospun membrane ESM1 (same as in Example 1);

[0101] 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;

[0102] 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.

[0103] Example 5

[0104] This embodiment provides a method for preparing a single ion conducting solid polymer electrolyte membrane SICC-SEM5, and the specific steps are as follows:

[0105] S1: Preparation of electrospun membrane ESM1 (same as in Example 1);

[0106] 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;

[0107] 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.

[0108] Example 6

[0109] The embodiment provides a preparation method of a single-ion-conducting solid-state polymer electrolyte film SICC-SEM6, and the specific steps are as follows:

[0110] S1: prepare the electrospun film ESM1 (same as in Embodiment 1);

[0111] S2: prepare the precursor solution SPEPS1 (same as in Embodiment 1);

[0112] S3: after 0.5 g of the precursor solution SPEPS1 is dropped on the electrospun film ESM1 with an area of 33 cm 2

[0113] Embodiment 7

[0114] The embodiment provides a preparation method of a single-ion-conducting solid-state polymer electrolyte film SICC-SEM7, and the specific steps are as follows:

[0115] S1: prepare the electrospun film ESM1 (same as in Embodiment 1);

[0116] S2: prepare the precursor solution SPEPS1 (same as in Embodiment 1);

[0117] S3: after 0.8 g of the precursor solution SPEPS1 is dropped on the electrospun film ESM1 with an area of 33 cm 2

[0118] In order to illustrate the actual effect of the technical scheme of the application, the application also provides Comparative Examples 1-3.

[0119] Comparative Example 1

[0120] The comparative example provides a preparation method of a liquid electrolyte LE / ESM1, and the specific steps are as follows:

[0121] S1: prepare the electrospun film ESM1 (same as in Embodiment 1);

[0122] S2: in an argon-filled glove box, lithium bis-trifluoromethanesulfonimide (LiTFSI) and tetraethylene glycol dimethyl ether (G4) are stirred and uniformly mixed to obtain the liquid electrolyte LE;

[0123] ​​S3: After 0.8 g of liquid electrolyte LE was dropped on the electrospun membrane ESM1 with an area of 33 cm 2 , a 90 pm doctor blade was used for sufficient blade coating infiltration for 3 min, obtaining the liquid electrolyte LE / ESM1.

[0124] Comparative Example 2

[0125] This comparative example provides a preparation method of the solid-state polymer electrolyte membrane SPEM1, the specific steps are as follows:

[0126] S1: In an argon-filled glove box, 0.3833 g (47.91 wt%) of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), 0.2967 (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 a photoinitiator were stirred and mixed uniformly until completely dissolved, obtaining a precursor solution SPEPS4;

[0127] S2: 0.8 g of the precursor solution SPEPS4 was taken with a dropper and dropped in a solid-state electrolyte mold with an area of 33 cm 2 , and a 90 pm doctor blade was used for coating, then transferred to an ultraviolet lamp for 15 min of ultraviolet radical polymerization, obtaining the solid-state polymer electrolyte membrane SPEM1.

[0128] Comparative Example 3

[0129] This comparative example provides a preparation method of the solid-state polymer electrolyte membrane SPEM2, the specific steps are as follows:

[0130] 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 uniformly until completely dissolved, obtaining a precursor solution SPEPS5;

[0131] S2: 0.8 g of the precursor solution SPEPS5 was taken with a dropper and dropped in a solid-state electrolyte mold with an area of 33 cm 2SPEM2 was obtained by transferring the solid-state electrolyte mold into the ultraviolet lamp for 15 min of ultraviolet radical polymerization after being placed in the solid-state electrolyte mold and using a 90 µm doctor blade for doctor blading, wherein,

[0132] Formula 2.

[0133] Test Example 1

[0134] In an argon-filled glove box, SICC-SEM1 was placed between two stainless steel sheets (SS) to form a SS|SICC-SEM1|SS symmetric battery. An electrochemical workstation was used to test the impedance spectrum of the SS|SICC-SEM1|SS symmetric battery at 25°C, and the results are shown in FIG. 1. Among them, Figure 2 Figure 2 is the electrochemical impedance spectrum of the SS|SICC-SEM1|SS symmetric battery.

[0135] According to Figure 2 It can be seen that the electrochemical impedance of the SS|SICC-SEM1|SS symmetric battery is small, and the ion conductivity is calculated to be 2.22×10 -3 S / cm.

[0136] Test Example 2

[0137] Stainless steel sheets (SS) and lithium metal (Li) were selected as electrodes, and in an argon-filled glove box, SICC-SEM1 was placed between the electrodes to form a Li|SICC-SEM1|SS battery. An electrochemical workstation was used to test the linear sweep voltammetry curve of the Li|SICC-SEM1|SS battery at 25°C, and the results are shown in FIG. 2. Among them, Figure 3 Figure 3 is the linear sweep voltammetry curve of the Li|SICC-SEM1|SS battery.

[0138] According to Figure 3 It can be seen that the oxidation stable potential of the Li|SICC-SEM1|SS battery can reach 5.2V, indicating that SICC-SEM1 exhibits excellent electrochemical stability.

[0139] Test Example 3

[0140] Lithium metal (Li) was selected as the electrode, and in an argon-filled glove box, SICC-SEM1 was placed between the electrodes to form a Li|SICC-SEM1|Li symmetric battery. An electrochemical workstation was used to test the steady-state current polarization and impedance spectrum before and after polarization of the Li|SICC-SEM1|Li symmetric battery at 25°C, and the results are shown in FIG. 3. Among them, Figure 4 Figure 4 ​​​The current / time test curve and the impedance test curve before and after polarization of the Li|SICC-SEM1|Li symmetric battery are shown in the figure.

[0141] According to Figure 4 It can be seen that SICC-SEM1 has a lithium ion transference number of 0.75, and the resistance of the electrolyte film changes little before and after polarization, and the curve semicircle changes little, indicating that SICC-SEM1 can effectively inhibit anion migration and concentration polarization.

[0142] Test Example 4

[0143] Lithium metal (Li) was selected as the electrode, SICC-SEM1 was placed between the electrodes in an argon-filled glove box, and the Li|SICC-SEM1|Li symmetric battery was assembled and sealed. The Li|SICC-SEM1|Li symmetric battery was tested at a current density of 0.1 mA·cm -2 -2 at 25°C, and the results are shown in the figure. Figure 5 Figure 5 The current-time test curve of the Li|SICC-SEM1|Li symmetric battery at a current density of 0.1 mA·cm -2 -2.

[0144] According to Figure 5 It can be seen that the Li|SICC-SEM1|Li symmetric battery was subjected to lithium plating / stripping for 2000h at a current density of 0.1 mA·cm -2 -2, indicating that SICC-SEM1 used in the Li||Li symmetric battery not only reduces concentration polarization, but also has the effect of inhibiting lithium dendrite growth.

[0145] Test Example 5

[0146] Lithium iron phosphate (LFP) was selected as the positive electrode, lithium metal (Li) was selected as the negative electrode, SICC-SEM1 was placed between the positive and negative electrodes in an argon-filled glove box, and the LFP|SICC-SEM1|Li battery was assembled and sealed. The LFP|SICC-SEM1|Li battery was tested at a rate of 0.5C under constant current charging and discharging (test voltage interval: 2.5~4V) at 25°C, and the results are shown in the figure. Figure 6 Figure 6 The cycle graph of the LFP|SICC-SEM1|Li battery at 0.5C.

[0147] According to Figure 6 It can be seen that the LFP|SICC-SEM1|Li battery was subjected to stable cycling for 500 cycles at a rate of 0.5C; at the same time, the initial discharge specific capacity of the LFP|SICC-SEM1|Li battery at a rate of 0.5C was 146mAh·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.

[0148] Test Example 6

[0149] 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.

[0150] according to Figure 7 It 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.

[0151] Test Example 7

[0152] 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.

[0153] 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.

[0154] Test Example 8

[0155] Lithium metal (Li) was selected as the electrode, and SPEM1 was placed between the electrodes in an argon-filled glove box to assemble Li|SPEM1|Li symmetric battery. The steady-state current polarization test and impedance spectrum test before and after polarization of the above Li|SPEM1|Li symmetric battery were carried out at 25°C using an electrochemical workstation, and the results are shown in Table 6. Table 6 Figure 9 The current / time test curve and impedance test curve of Li|SPEM1|Li symmetric battery before and after polarization are shown in FIG. 6. Among them, Figure 9 is the cycle diagram of NCM811|LE / ESM1|Li battery at 0.5C.

[0156] According to Figure 9 It can be seen that after 50 cycles of NCM811|LE / ESM1|Li battery, the coulombic efficiency is obviously reduced, and the battery is invalid.

[0157] Test Example 9

[0158] Lithium metal (Li) was selected as the electrode, and SPEM1 was placed between the electrodes in an argon-filled glove box to assemble Li|SPEM1|Li symmetric battery. The steady-state current polarization test and impedance spectrum test before and after polarization of the above Li|SPEM1|Li symmetric battery were carried out at 25°C using an electrochemical workstation, and the results are shown in Table 6. Table 6 Figure 10 The current / time test curve and impedance test curve of Li|SPEM1|Li symmetric battery before and after polarization are shown in FIG. 6. Among them, Figure 10 is the cycle diagram of NCM811|LE / ESM1|Li battery at 0.5C.

[0159] According to Figure 10 It can be seen that SPEM1 only shows a lithium ion transference number of 0.42, which is much lower than 0.75 of SICC-SEM1, indicating that the solid-state polymer electrolyte membrane without alkenyl borate compound of formula 1 cannot effectively inhibit anion migration.

[0160] Test Example 10

[0161] Lithium metal (Li) was selected as the electrode, and SPEM1 was placed between the electrodes in an argon-filled glove box to assemble Li|SPEM1|Li symmetric battery. The steady-state current polarization test and impedance spectrum test before and after polarization of the above Li|SPEM1|Li symmetric battery were carried out at 25°C using an electrochemical workstation, and the results are shown in Table 6. Table 6 Figure 11 The current / time test curve and impedance test curve of Li|SPEM1|Li symmetric battery before and after polarization are shown in FIG. 6. Among them, Figure 11 is the cycle diagram of NCM811|LE / ESM1|Li battery at 0.5C.

[0162] According to Figure 11 It can be seen that the initial discharge specific capacity of the NCM811|SPEM1|Li battery at 0.5C rate is 193.6mAh·g -1 , and the discharge specific capacity after 200 cycles is 140.2mAh·g -1 , and the capacity retention rate is 72.42%, and the cycle performance is relatively poor compared with the NCM811|SICC-SEM1|Li battery.

[0163] Test Example 11

[0164] Lithium metal (Li) was selected as the electrode, and the single-ion conducting solid-state polymer electrolyte film SPEM2 was placed between the electrodes in an argon-filled glove box, and the Li|SPEM2|Li symmetric battery was sealed and assembled. The steady-state current polarization test and impedance spectrum test before and after polarization of the Li|SPEM2|Li symmetric battery were carried out at 25℃ using an electrochemical workstation, and the results are shown in Figure 12 . Figure 12 The current / time test curve and impedance test curve before and after polarization of the Li|SPEM2|Li symmetric battery are shown in

[0165] According to Figure 12 It can be seen that the SPEM2 exhibits a lithium ion transference number of 0.59, indicating that the SPEM2 also has the effect of inhibiting anion migration and concentration polarization, but is relatively poor compared with SICC-SEM1.

[0166] Test Example 12

[0167] Lithium nickel cobalt manganese oxide 811 (NCM811) was selected as the positive electrode, and lithium metal (Li) was selected as the negative electrode, and the SPEM2 was placed between the positive and negative electrodes in an argon-filled glove box, and the NCM811|SPEM2|Li battery was sealed and assembled. The NCM811|SPEM2|Li battery was tested at 0.5C rate under constant current charge and discharge at 25℃ (the test voltage interval was 2.8~4.3V), and the results are shown in Figure 13 Figure 13 is the cycle diagram of the NCM811|SPEM2|Li battery at 0.5C.

[0168] According to Figure 13 It can be seen that the NCM811|SPEM2|Li battery is stably cycled for 150 cycles at 0.5C rate; at the same time, the initial discharge specific capacity of the NCM811|SPEM2|Li battery at 0.5C rate is 191.5mAh·g -1 , and the discharge specific capacity after 150 cycles is 144mAh·g -1 ​, the capacity retention rate was 75.2%, and the coulombic efficiency was above 99%, indicating that although the NCM811||Li battery using SPEM2 also exhibited excellent cycle stability, it was still inferior to SICC-SEM1.

[0169] Each embodiment in the specification is described in a progressive manner, and the same or similar parts between each embodiment can be mutually referred to, and each embodiment focuses on the difference from other embodiments.

[0170] The above examples are only used to illustrate the technical solutions of the present application, and are not limited to the present application; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can still be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions 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; The alkenyl borate compound is represented by Formula 1: Formula 1.

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 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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