Solid electrolyte fiber diaphragm as well as preparation method and application thereof

Abstract

The invention relates to the field of solid-state lithium batteries, and discloses a solid-state electrolyte fiber diaphragm and a preparation method and application thereof.The preparation method comprises the steps that 1, a solution I is subjected to electrostatic spinning to obtain an electrostatic spinning membrane I, and the solution I contains a terephthalamide polymer and first ionic liquid; (2) performing first contact on the electrostatic spinning membrane I and second ionic liquid to obtain an electrostatic spinning membrane II; (3) carrying out second contact on the electrostatic spinning membrane II and lithium salt to obtain an electrostatic spinning membrane III; and (4) carrying out hot pressing on the electrostatic spinning membrane III to obtain the solid electrolyte fiber diaphragm, the diaphragm provided by the invention has excellent comprehensive performance, and particularly has high ionic conductivity, good thermal stability, good electrochemical performance and good mechanical performance.

Description

Technical Field

[0001] The present invention relates to the field of solid-state lithium batteries, and in particular to a solid-state electrolyte fiber diaphragm and a preparation method and application thereof. Background Art

[0002] The energy density of existing lithium-ion batteries using graphite negative electrodes can no longer meet the requirements of the rapidly developing electric vehicles and portable electronic devices. Lithium has a mass of 6.941 g.mol -1 Molar mass, theoretical specific capacity 3860mAh.g -1 The energy density of the battery is 10 times that of graphite. Using metallic lithium as the negative electrode can improve the specific energy of the battery. However, lithium inevitably undergoes uneven deposition in the organic electrolyte and forms lithium dendrites, which pierce the diaphragm and cause the battery to short-circuit, leading to safety accidents. Therefore, secondary batteries using metallic lithium as the negative electrode have not yet been commercialized.

[0003] All-solid-state lithium batteries replace flammable organic electrolytes with non-flammable solid electrolytes. They have the advantages of high safety and high energy density and are considered to be the preferred direction for the next generation of new power batteries and energy storage batteries. Among them, solid electrolyte membranes are one of the important components of all-solid-state lithium batteries. Solid electrolyte membranes can replace liquid electrolytes and membranes and should meet certain requirements: high ionic conductivity (>10 -4 S / cm), good thermal stability, electrochemical properties and mechanical properties to resist the impact during battery assembly and the damage of lithium dendrites during use.

[0004] The current solid electrolyte membranes can be divided into two types: inorganic solid electrolyte membranes and polymer solid electrolyte membranes. Compared with inorganic solid electrolyte membranes, polymer electrolyte membranes are easier to process and are suitable for large-scale industrial production, with better development prospects. However, although the existing polymer electrolyte membranes have good safety, they have poor contact with electrodes, resulting in high interface impedance. At the same time, the room temperature ionic conductivity of most polymer electrolytes is low, about 10 -7 -10 -4 S / cm, which is difficult to meet the needs of lithium-ion batteries.

[0005] Therefore, there is an urgent need to provide a polymer solid electrolyte membrane with high room temperature ionic conductivity. Summary of the invention

[0006] The purpose of the present invention is to overcome the above-mentioned defects of the prior art and provide a polymer solid electrolyte fiber membrane with high room temperature ionic conductivity. The obtained solid electrolyte fiber membrane also has excellent thermal stability, high tensile strength and excellent comprehensive performance.

[0007] In order to achieve the above object, the first aspect of the present invention provides a method for preparing a solid electrolyte fiber membrane, the method comprising:

[0008] (1) electrospinning a solution I to obtain an electrospinning membrane I, wherein the solution I contains a terephthalamide-based polymer and a first ionic liquid;

[0009] (2) bringing the electrospun membrane I into first contact with a second ionic liquid to obtain an electrospun membrane II;

[0010] (3) contacting the electrospun membrane II with a lithium salt for a second time to obtain an electrospun membrane III;

[0011] (4) hot pressing the electrospun membrane III to obtain a solid electrolyte fiber membrane;

[0012] Wherein, the first ionic liquid is selected from at least one of carboxylate ionic liquids, chloride ionic liquids and bromide ionic liquids; the second ionic liquid is selected from one of bisfluorosulfonyl imide ionic liquids, bistrifluoromethanesulfonyl imide ionic liquids, tetrafluoroborate ionic liquids, hexafluorophosphate ionic liquids and difluorophosphate ionic liquids;

[0013] The first ionic liquid and the second ionic liquid have the same cation, and the lithium salt and the second ionic liquid have the same anion.

[0014] The second aspect of the present invention provides a solid electrolyte fiber separator obtained by the above method.

[0015] The third aspect of the present invention provides the use of the aforementioned solid electrolyte fiber membrane in a solid-state lithium battery.

[0016] The solid electrolyte fiber diaphragm provided by the present invention has high room temperature ionic conductivity, which can meet the requirements of solid-state lithium-ion batteries. In addition, the solid electrolyte fiber diaphragm provided by the present invention also has good thermal stability, high tensile strength and excellent electrochemical properties, and has better comprehensive performance.

[0017] Other features and advantages of the present invention will be described in detail in the following detailed description. DETAILED DESCRIPTION

[0018] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0019] As mentioned above, the first aspect of the present invention provides a method for preparing a solid electrolyte fiber separator, the method comprising:

[0020] (1) electrospinning a solution I to obtain an electrospinning membrane I, wherein the solution I contains a terephthalamide-based polymer and a first ionic liquid;

[0021] (2) bringing the electrospun membrane I into first contact with a second ionic liquid to obtain an electrospun membrane II;

[0022] (3) contacting the electrospun membrane II with a lithium salt for a second time to obtain an electrospun membrane III;

[0023] (4) hot pressing the electrospun membrane III to obtain a solid electrolyte fiber membrane;

[0024] Wherein, the first ionic liquid is selected from at least one of carboxylate ionic liquids, chloride ionic liquids and bromide ionic liquids; the second ionic liquid is selected from one of bisfluorosulfonyl imide ionic liquids, bistrifluoromethanesulfonyl imide ionic liquids, tetrafluoroborate ionic liquids, hexafluorophosphate ionic liquids and difluorophosphate ionic liquids;

[0025] The first ionic liquid and the second ionic liquid have the same cation, and the lithium salt and the second ionic liquid have the same anion.

[0026] Preferably, the groups contained in the terephthalamide polymer are selected from at least one of sulfonic acid, benzenesulfonic acid, sulfonyl, sulfonamide, benzenesulfonamide, aniline, benzidine, benzoic acid, terephthalic acid, p-phenylenediamine, 2,4-diaminotoluene, 2,6-diaminotoluene, m-xylene diamine, and p-xylene diamine. More preferably, the terephthalamide polymer is selected from at least one of disulfonic acid-benzidine-terephthalamide polymer, diphenylsulfonic acid-benzidine-terephthalamide polymer, and disulfonamide-benzidine-terephthalamide polymer. Further preferably, the weight average molecular weight of the terephthalamide polymer is 8000-50000. According to the present invention, the terephthalamide polymer can be obtained commercially or prepared by existing preparation methods in the art.

[0027] Preferably, the first ionic liquid is selected from at least one of 1-ethyl-3-methylimidazolium acetate, 1-propyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium acetate, N-propyl-N-methylpyridine acetate, 1-ethyl-1-methylpyrrolidine acetate, 1-ethyl-3-methylimidazolium chloride, 1-propyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, N-propyl-N-methylpyrrolidine chloride, 1-ethyl-1-methylpyrrolidine chloride, 1-ethyl-3-methylimidazolium bromide, 1-propyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium bromide, N-propyl-N-methylpyrrolidine bromide, and 1-ethyl-1-methylpyrrolidine bromide. More preferably, the first ionic liquid is selected from at least one of 1-ethyl-3-methylimidazolium acetate, 1-propyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium acetate, 1-ethyl-3-methylimidazolium chloride, 1-propyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium bromide, 1-propyl-3-methylimidazolium bromide, and 1-butyl-3-methylimidazolium bromide.

[0028] According to a preferred embodiment of the present invention, the method of the present invention further comprises preparing the solution I by the following steps:

[0029] The terephthalamide-based polymer and the first ionic liquid are fully dissolved in a solvent at 20-100° C. to obtain the solution I.

[0030] Preferably, in the solution I, the concentration of the terephthalamide-based polymer is 0.1-20 wt %, and the concentration of the first ionic liquid is 1-70 wt %.

[0031] Preferably, the solvent of the solution I is selected from one of water, ethanol, methanol, DMF, DMSO, DMI, acetone, dichloromethane, dichloroethane and the like.

[0032] Preferably, the second ionic liquid is selected from 1-ethyl-3-methylimidazolium bisfluorosulfonyl imide, 1-propyl-3-methylimidazolium bisfluorosulfonyl imide, 1-butyl-3-methylimidazolium bisfluorosulfonyl imide, N-propyl-N-methylpyridine bisfluorosulfonyl imide, 1-ethyl-1-methylpyrrolidine bisfluorosulfonyl imide, 1-ethyl-3-methylimidazolium bistrifluoromethanesulfonyl imide, 1-propyl-3-methylimidazolium bistrifluoromethanesulfonyl imide, 1-butyl-3-methylimidazolium bistrifluoromethanesulfonyl imide, N-propyl-N-methylpyridine bistrifluoromethanesulfonyl imide, 1-ethyl-1-methylpyrrolidine bistrifluoromethanesulfonyl imide, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-propyl-3-methylimidazolium bistrifluoromethanesulfonyl imide, At least one of methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium tetrafluoroborate, N-propyl-N-methylpyridinium tetrafluoroborate, 1-ethyl-1-methylpyrrolidine tetrafluoroborate, 1-ethyl-3-methylimidazolium hexafluorophosphate, 1-propyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium hexafluorophosphate, N-propyl-N-methylpyridinium hexafluorophosphate, 1-ethyl-1-methylpyrrolidine hexafluorophosphate, 1-ethyl-3-methylimidazolium difluorophosphate, 1-propyl-3-methylimidazolium difluorophosphate, 1-butyl-3-methylimidazolium difluorophosphate, N-propyl-N-methylpyridinium difluorophosphate, and 1-ethyl-1-methylpyrrolidine difluorophosphate. More preferably, the second ionic liquid is selected from 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide, 1-propyl-3-methylimidazolium bis(fluorosulfonyl)imide, 1-butyl-3-methylimidazolium bis(fluorosulfonyl)imide, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-propyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-ethyl-3-methylimidazolium tetrakis At least one of fluoroborate, 1-propyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium hexafluorophosphate, 1-propyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium difluorophosphate, 1-propyl-3-methylimidazolium difluorophosphate, and 1-butyl-3-methylimidazolium difluorophosphate.

[0033] According to a most preferred embodiment of the present invention, the first ionic liquid, the second ionic liquid and the lithium salt are selected from the following combinations:

[0034] Combination 1: the first ionic liquid is 1-ethyl-3-methylimidazolium chloride; the second ionic liquid is 1-ethyl-3-methylimidazolium bisfluorosulfonyl imide, and the lithium salt is lithium bisfluorosulfonyl imide;

[0035] Combination 2: the first ionic liquid is 1-butyl-3-methylimidazolium acetate; the second ionic liquid is 1-butyl-3-methylimidazolium bisfluorosulfonyl imide salt, the lithium salt is lithium bisfluorosulfonyl imide, and the lithium salt is lithium bistrifluoromethanesulfonyl imide;

[0036] Combination 3: the first ionic liquid is 1-ethyl-3-methylimidazolium acetate; the second ionic liquid is 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, and the lithium salt is lithium bis(trifluoromethanesulfonyl)imide.

[0037] The inventors of the present invention have found that the solid electrolyte fiber separator obtained by specially selecting the combination of the first ionic liquid, the second ionic liquid and the lithium salt has better performance, such as higher ion conductivity.

[0038] Preferably, in step (1), the weight ratio of the first ionic liquid to the terephthalamide-based polymer is 1-50:1.

[0039] Preferably, in step (2), the weight ratio of the second ionic liquid to the terephthalamide-based polymer is 50-200:1.

[0040] Preferably, in step (3), the weight ratio of the lithium salt to the terephthalamide-based polymer is 1-15:1.

[0041] Preferably, in step (1), the electrospinning conditions include: spinning voltage of 10-30 kV, receiving distance of 10-30 cm, humidity of 20-60%, and temperature of 20-50°C.

[0042] Preferably, in step (2), the conditions for the first contact include: temperature 20-50° C., time 12-48 h.

[0043] Preferably, in step (3), the electrospinning membrane II is brought into second contact with a lithium salt to perform ion exchange, and the conditions of the second contact include: a temperature of 20-50° C. and a time of 12-48 h.

[0044] According to the method of the present invention, the present invention also includes a step of performing a second drying after the second contact to obtain the electrospinning membrane III. Preferably, the second drying is performed under vacuum conditions, the drying temperature is 30-100°C, and the drying time is 5-30h.

[0045] Preferably, in step (4), the hot pressing conditions include: the hot pressing temperature is 50-120° C., and the hot pressing time is 2-30 minutes.

[0046] As mentioned above, the second aspect of the present invention provides a solid electrolyte fiber separator obtained by the above method.

[0047] Preferably, the solid electrolyte fiber membrane has an ionic conductivity of 1-4 mS / cm, preferably 2.5-4 mS / cm; a tensile strength of 20-60 MPa, preferably 40-60 MPa; and a thermal shrinkage of <5%, preferably <3%.

[0048] The solid electrolyte fiber provided by the present invention has better comprehensive performance, especially high ion conductivity at room temperature, good thermal stability, electrochemical performance and high tensile strength.

[0049] As mentioned above, the third aspect of the present invention provides the use of the aforementioned solid electrolyte fiber membrane in a solid-state lithium battery.

[0050] The solid-state lithium battery obtained by using the solid electrolyte fiber diaphragm provided by the present invention has excellent electrochemical performance, high capacity retention rate and excellent rate performance.

[0051] In the present invention, unless otherwise specified, pressure refers to gauge pressure and room temperature refers to 25±2°C.

[0052] The present invention will be described in detail below through examples.

[0053] In the following examples, unless otherwise specified, all raw materials used are commercially available products.

[0054] The electrospinning device used below was purchased from Beijing Xinyan Hechuang Technology Co., Ltd.

[0055] The ionic liquids used in the following examples were purchased from TCI; the lithium salts used were purchased from New Energy Corporation;

[0056] Preparation Example A: Preparation of disulfonic acid-benzidine-terephthalamide polymer

[0057] (1) 0.02 mol of diaminobiphenyl-disulfonic acid, 0.04 mol of cesium hydroxide monohydrate, and 0.02 mol of sodium carbonate were mixed in 150 ml of deionized water, stirred thoroughly until dissolved, and then 30 ml of toluene was added to obtain a mixture A;

[0058] (2) dissolving 0.02 mol of terephthaloyl chloride in 30 ml of toluene to obtain a mixture B;

[0059] (3) adding mixture B to mixture A under high-speed stirring, stirring for 3 minutes, stopping stirring, adding 150 ml of ethanol, filtering and washing twice with 200 ml of ethanol to obtain a disulfonic acid-benzidine-terephthalamide polymer;

[0060] The weight average molecular weight Mw of the disulfonic acid-benzidine-terephthalamide polymer was determined by GPC, and the specific test conditions were: the chromatographic column was controlled at 40° C. with a thermostat, a flow rate of 0.6 ml / min, and sodium poly(p-styrene sulfonate) was used as a GPC standard.

[0061] Preparation Example B: Preparation of diphenylsulfonic acid-benzidine-terephthalamide polymer

[0062] A diphenylsulfonate-benzidine-terephthalamide polymer was prepared by a method similar to that of Preparation Example A, except that the diaminobiphenyl-disulfonic acid was replaced by diaminobiphenyl-dibenzenesulfonic acid, and the molecular weight Mw of the diphenylsulfonate-benzidine-terephthalamide polymer was determined by GPC to be 23400.

[0063] Preparation Example C: Preparation of disulfonamide-benzidine-terephthalamide polymer

[0064] A disulfonamide-benzidine-terephthalamide polymer was prepared by a method similar to the above method, except that the diaminobiphenyl-disulfonic acid was replaced by diaminobiphenyl-disulfonamide, and the molecular weight Mw of the disulfonamide-benzidine-terephthalamide polymer was determined by GPC to be 13500.

[0065] Preparation Example D: Preparation of disulfonic acid-benzidine-terephthalamide polymer

[0066] The disulfonic acid-benzidine-terephthalamide polymer was prepared by the following method:

[0067] (1) 0.02 mol of diaminobiphenyl-disulfonic acid, 0.02 mol of cesium hydroxide monohydrate, and 0.01 mol of sodium carbonate were mixed in 300 ml of deionized water, stirred thoroughly until dissolved, and then 30 ml of toluene was added to obtain a mixture A;

[0068] (2) dissolving 0.02 mol of terephthaloyl chloride in 60 ml of toluene to obtain a mixture B;

[0069] (3) adding mixture B to mixture A under high-speed stirring, stirring for 1 minute, stopping stirring, adding 150 ml of ethanol, filtering and washing twice with 200 ml of ethanol to obtain a disulfonic acid-benzidine-terephthalamide polymer;

[0070] The molecular weight Mw of the obtained disulfonic acid-benzidine-terephthalamide polymer was measured by GPC and was 4000.

[0071] Example 1

[0072] (1) 0.05 g of the disulfonic acid-benzidine-terephthalamide polymer prepared in Preparation Example A and 0.45 g of 1-ethyl-3-methylimidazolium chloride ionic liquid were fully dissolved in 5 g of a mixed solvent (water, acetone and dichloromethane in a volume ratio of 7:2:1), and mixed uniformly at 50° C. to obtain a solution I; the solution I was electrospun to prepare an electrospinning membrane I, and the electrospinning conditions included: a spinning voltage of 30 kV, a receiving distance of 15 cm, a humidity of 40%, and a temperature of 40° C.;

[0073] (2) immersing the obtained electrospun membrane I in 10 g of 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide salt ionic liquid at room temperature for 24 hours to obtain an electrospun membrane II;

[0074] (3) the obtained electrospun membrane II was contacted with 0.5 g of lithium bis(fluorosulfonyl)imide at room temperature for a second time to perform ion exchange, and the contact time was 24 hours. The membrane material after ion exchange was vacuum dried for 24 hours at a drying temperature of 70° C. to obtain an electrospun membrane III;

[0075] (4) The electrospun membrane III is hot pressed, and the hot pressing conditions include: the hot pressing temperature is 80° C. and the hot pressing time is 5 minutes, to obtain a solid electrolyte fiber membrane.

[0076] Example 2

[0077] (1) 0.1 g of the diphenylsulfonate-benzidine-terephthalamide polymer prepared in Preparation Example B and 0.5 g of 1-butyl-3-methylimidazolium acetate ionic liquid were fully dissolved in 5 g of a mixed solvent (water, acetone and DMF in a volume ratio of 4:2:4), and mixed uniformly at 50° C. to obtain a solution I. The solution I was electrospun to prepare an electrospinning membrane I, and the electrospinning conditions included: a spinning voltage of 20 kV, a receiving distance of 20 cm, a humidity of 30%, and a temperature of 30° C.;

[0078] (2) immersing the obtained electrospun membrane I in 6 g of 1-butyl-3-methylimidazolium bis(fluorosulfonyl)imide salt ionic liquid at room temperature for 24 hours to obtain an electrospun membrane II;

[0079] (3) the obtained electrospun membrane II was contacted with 1 g of lithium bis(fluorosulfonyl)imide at room temperature for a second time to perform ion exchange, and the contact time was 24 hours; the membrane material after ion exchange was vacuum dried for 24 hours at a drying temperature of 70° C. to obtain an electrospun membrane III;

[0080] (4) The electrospun membrane II is hot pressed, and the hot pressing conditions include: the hot pressing temperature is 80° C. and the hot pressing time is 5 minutes, to obtain a solid electrolyte fiber membrane.

[0081] Example 3

[0082] (1) 0.2 g of the disulfonamide-benzidine-terephthalamide polymer prepared in Preparation Example C and 0.3 g of 1-ethyl-3-methylimidazolium acetate ionic liquid were fully dissolved in 5 g of a mixed solvent (water, acetone, and DMF in a volume ratio of 4:2:4), and mixed uniformly at 50° C. to obtain a solution I; the solution I was electrospun to prepare an electrospinning membrane I, and the electrospinning conditions included: a spinning voltage of 20 kV, a receiving distance of 20 cm, a humidity of 30%, and a temperature of 30° C.;

[0083] (2) immersing the obtained electrospun membrane I in 10 g of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt ionic liquid at room temperature for 24 hours to obtain an electrospun membrane II;

[0084] (3) the obtained electrospun membrane II was contacted with 1.5 g of lithium bis(trifluoromethanesulfonyl)imide at room temperature for a second time to perform ion exchange for 24 hours, and the membrane material after ion exchange was vacuum dried for 24 hours at a drying temperature of 60° C. to obtain an electrospun membrane III;

[0085] (4) The electrospun membrane III is hot pressed, and the hot pressing conditions include: the hot pressing temperature is 80° C. and the hot pressing time is 5 minutes, to obtain a solid electrolyte fiber membrane.

[0086] Example 4

[0087] A method similar to that in Example 1 was adopted, with the only difference being that an equal mass of di-p-toluenesulfonyl-benzidine-terephthalamide polymer (prepared by the same method as in Preparation Example A, except that the diaminobiphenyl-disulfonic acid in Preparation Example A was replaced by diaminobiphenyl-di-p-toluenesulfonyl) was used instead of the disulfonic acid-benzidine-terephthalamide polymer in Example 1 to prepare a solid electrolyte fiber membrane.

[0088] Example 5

[0089] A similar method to Example 1 was used, except that an equal mass of 1-ethyl-1-methylpyrrolidine acetate ionic liquid was used to replace the first ionic liquid of the example, an equal mass of 1-ethyl-1-methylpyrrolidine tetrafluoroborate ionic liquid was used to replace the second ionic liquid in Example 1, and the lithium salt was replaced with an equal mass of lithium tetrafluoroborate to prepare a solid electrolyte fiber membrane.

[0090] Example 6

[0091] A solid electrolyte fiber membrane was prepared by a method similar to that of Example 1, except that an equal mass of the disulfonic acid-benzidine-terephthalamide polymer prepared in Preparation Example D was used instead of the disulfonic acid-benzidine-terephthalamide polymer prepared in Preparation Example A in Example 1.

[0092] Comparative Example 1

[0093] A solid electrolyte fiber membrane was prepared by using a method similar to that in Example 1, except that an equal mass of 1-ethyl-3-methylimidazole acetate was used to replace the first ionic liquid in Example 1, and an equal mass of N-propyl-N-methylpyridinium bisfluorosulfonyl imide was used to replace the second ionic liquid in Example 1.

[0094] Comparative Example 2

[0095] A solid electrolyte fiber membrane was prepared by a method similar to that of Example 1, except that an equal mass of lithium hexafluorophosphate was used instead of the lithium bis(fluorosulfonyl)imide of Example 1.

[0096] Test Case

[0097] 1. The following properties of the solid electrolyte membranes obtained in the above embodiments and comparative examples were tested. The test results are shown in Table 1 below.

[0098] (1) Ionic conductivity: The ionic conductivity of the diaphragm was measured using an electrochemical workstation. The test frequency range was 0.001 Hz to 10 5 Hz, the test temperature is room temperature (25℃), and then the conductivity (σ) is calculated according to the formula. The specific results are shown in the table below:

[0099]

[0100] Where, σ is the ionic conductivity of the membrane (S / cm), d is the thickness of the membrane (cm), R b is the bulk resistance of the diaphragm (Ω), A is the effective contact area between the diaphragm and the electrode (cm 2 ).

[0101] (2) Tensile strength: The tensile strength of the solid electrolyte fiber diaphragm prepared in the above example was tested using the plastic tensile test method of GB1040-79;

[0102] (3) Thickness: Use a thickness gauge (accuracy 0.1 μm) to test the thickness. Randomly select 5 points on the sample and take the average value.

[0103] (4) Thermal shrinkage: The thermal shrinkage of the dimensions was measured in an oven. The sample was heat treated at 150°C for 1 h, and then the thermal shrinkage (δ) was calculated according to the formula:

[0104]

[0105] Among them, S1 and S2 are the areas of the diaphragm before and after heat treatment;

[0106] Table 1

[0107] Examples Thickness / μm Ionic conductivity / mS / cm Tensile strength / MPa Thermal shrinkage Example 1 25 3.4 48 ＜3％ Example 2 30 2.8 56 ＜3％ Example 3 25 3.0 40 ＜3％ Example 4 25 1.9 29 ＜3％ Example 5 25 2.4 30 ＜3％ Example 6 25 0.8 9 15％ Comparative Example 1 25 0.3 13 10％ Comparative Example 2 25 0.1 25 ＜3％

[0108] 2. The solid electrolyte membranes obtained in the above embodiments and comparative examples were assembled into solid-state lithium batteries, and the following performances of the batteries were tested. The test results are shown in Table 2 below.

[0109] Preparation of solid-state lithium batteries:

[0110] The positive electrode formula is lithium iron phosphate: conductive carbon black: binder (PVDF) = 80:10:10, and the negative electrode is lithium metal. The battery is assembled in the order of negative electrode shell, lithium metal negative electrode, solid electrolyte composite diaphragm, positive electrode, stainless steel sheet, spring sheet, and positive electrode shell.

[0111] The solid-state lithium battery was charged and discharged at a rate of 1C in the range of 2.8-4.2V, and a battery assembled with a commercial liquid electrolyte and a PP separator was charged and discharged at a rate of 1C for comparison (see Comparative Example 2).

[0112] Table 2

[0113]

[0114] In summary, the solid electrolyte fiber membrane provided by the present invention has high room temperature ionic conductivity, which can meet the needs of solid-state lithium-ion batteries. In addition, the solid electrolyte fiber membrane provided by the present invention also has good thermal stability, high tensile strength and excellent electrochemical properties, and has excellent comprehensive performance.

[0115] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for preparing a solid electrolyte fiber membrane, characterized in that: The method includes: (1) electrospinning a solution I to obtain an electrospinning membrane I, wherein the solution I contains a terephthalamide-based polymer and a first ionic liquid; (2) bringing the electrospun membrane I into first contact with a second ionic liquid to obtain an electrospun membrane II; (3) contacting the electrospun membrane II with a lithium salt for a second time to obtain an electrospun membrane III; (4) hot pressing the electrospun membrane III to obtain a solid electrolyte fiber membrane; Wherein, the first ionic liquid is selected from at least one of carboxylate ionic liquids, chloride ionic liquids and bromide ionic liquids; the second ionic liquid is selected from one of bisfluorosulfonyl imide ionic liquids, bistrifluoromethanesulfonyl imide ionic liquids, tetrafluoroborate ionic liquids, hexafluorophosphate ionic liquids and difluorophosphate ionic liquids; The first ionic liquid and the second ionic liquid have the same cation, and the lithium salt and the second ionic liquid have the same anion.

2. The method according to claim 1, wherein: The groups contained in the terephthalamide-based polymer are selected from at least one of sulfonic acid, benzenesulfonic acid, sulfonyl, sulfonamide, benzenesulfonamide, aniline, benzidine, benzoic acid, terephthalic acid, p-phenylenediamine, 2,4-diaminotoluene, 2,6-diaminotoluene, m-xylene diamine, and p-xylene diamine; Preferably, the terephthalamide-based polymer is selected from at least one of disulfonic acid-benzidine-terephthalamide polymer, diphenylsulfonic acid-benzidine-terephthalamide polymer, and disulfonic acid-benzidine-terephthalamide polymer; Preferably, the weight average molecular weight of the terephthalamide-based polymer is 8,000-50,000.

3. The method according to claim 1 or 2, wherein: The first ionic liquid is selected from at least one of 1-ethyl-3-methylimidazolium acetate, 1-propyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium acetate, N-propyl-N-methylpyridine acetate, 1-ethyl-1-methylpyrrolidine acetate, 1-ethyl-3-methylimidazolium chloride, 1-propyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, N-propyl-N-methylpyrrolidine chloride, 1-ethyl-1-methylpyrrolidine chloride, 1-ethyl-3-methylimidazolium bromide, 1-propyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium bromide, N-propyl-N-methylpyrrolidine bromide, and 1-ethyl-1-methylpyrrolidine bromide; Preferably, the first ionic liquid is selected from at least one of 1-ethyl-3-methylimidazolium acetate, 1-propyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium acetate, 1-ethyl-3-methylimidazolium chloride, 1-propyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium bromide, 1-propyl-3-methylimidazolium bromide, and 1-butyl-3-methylimidazolium bromide.

4. The method according to any one of claims 1 to 3, wherein: The second ionic liquid is selected from 1-ethyl-3-methylimidazolium bisfluorosulfonyl imide, 1-propyl-3-methylimidazolium bisfluorosulfonyl imide, 1-butyl-3-methylimidazolium bisfluorosulfonyl imide, N-propyl-N-methylpyridine bisfluorosulfonyl imide, 1-ethyl-1-methylpyrrolidine bisfluorosulfonyl imide, 1-ethyl-3-methylimidazolium bistrifluoromethanesulfonyl imide, 1-propyl-3-methylimidazolium bistrifluoromethanesulfonyl imide, 1-butyl-3-methylimidazolium bistrifluoromethanesulfonyl imide, N-propyl-N-methylpyridine bistrifluoromethanesulfonyl imide, 1-ethyl-1-methylpyrrolidine bistrifluoromethanesulfonyl imide, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-propyl-3-methylimidazolium bistrifluoromethanesulfonyl imide, At least one of imidazole tetrafluoroborate, 1-butyl-3-methylimidazolium tetrafluoroborate, N-propyl-N-methylpyridine tetrafluoroborate, 1-ethyl-1-methylpyrrolidine tetrafluoroborate, 1-ethyl-3-methylimidazolium hexafluorophosphate, 1-propyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium hexafluorophosphate, N-propyl-N-methylpyridine hexafluorophosphate, 1-ethyl-1-methylpyrrolidine hexafluorophosphate, 1-ethyl-3-methylimidazolium difluorophosphate, 1-propyl-3-methylimidazolium difluorophosphate, 1-butyl-3-methylimidazolium difluorophosphate, N-propyl-N-methylpyridine difluorophosphate, and 1-ethyl-1-methylpyrrolidine difluorophosphate; Preferably, the second ionic liquid is selected from 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide, 1-propyl-3-methylimidazolium bis(fluorosulfonyl)imide, 1-butyl-3-methylimidazolium bis(fluorosulfonyl)imide, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-propyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-ethyl-3-methylimidazolium tetrakis At least one of fluoroborate, 1-propyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium hexafluorophosphate, 1-propyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium difluorophosphate, 1-propyl-3-methylimidazolium difluorophosphate, and 1-butyl-3-methylimidazolium difluorophosphate.

5. The method according to any one of claims 1 to 4, wherein: The first ionic liquid, the second ionic liquid and the lithium salt are selected from the following combinations: Combination 1: the first ionic liquid is 1-ethyl-3-methylimidazolium chloride; the second ionic liquid is 1-ethyl-3-methylimidazolium bisfluorosulfonyl imide, and the lithium salt is lithium bisfluorosulfonyl imide; Combination 2: the first ionic liquid is 1-butyl-3-methylimidazolium acetate; the second ionic liquid is 1-butyl-3-methylimidazolium bisfluorosulfonyl imide salt, and the lithium salt is lithium bisfluorosulfonyl imide; Combination 3: the first ionic liquid is 1-ethyl-3-methylimidazolium acetate; the second ionic liquid is 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, and the lithium salt is lithium bis(trifluoromethanesulfonyl)imide.

6. The method according to any one of claims 1 to 5, wherein: In step (1), the weight ratio of the first ionic liquid to the terephthalamide-based polymer is 1-50:1; and / or, in step (2), the weight ratio of the second ionic liquid to the terephthalamide-based polymer is 50-200:1; And / or, in step (3), the weight ratio of the lithium salt to the terephthalamide-based polymer is 1-15:

1.

7. The method according to any one of claims 1 to 6, wherein: In step (1), the electrospinning conditions include: spinning voltage of 10-30 kV, receiving distance of 10-30 cm, humidity of 20-60%, and temperature of 20-50° C.; And / or, in step (2), the conditions of the first contact include: temperature 20-50°C, time 12-48h; And / or, in step (3), the conditions of the second contact include: temperature 20-50°C, time 12-48h; And / or, in step (4), the hot pressing conditions include: the hot pressing temperature is 50-120° C., and the hot pressing time is 2-30 minutes.

8. A solid electrolyte fiber membrane prepared by the method according to any one of claims 1 to 7.

9. The solid electrolyte fiber membrane according to claim 8, wherein: The room temperature ionic conductivity of the solid electrolyte fiber membrane is 1-4 mS / cm, preferably 2.5-4 mS / cm; the tensile strength is 20-60 MPa, preferably 40-60 MPa; the thermal shrinkage is less than 5%, preferably less than 3%.

10. Use of the solid electrolyte fiber separator according to claim 8 or 9 in a solid-state lithium battery.

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