A solid-state electrolyte fiber separator and a preparation method and application thereof

Abstract

This invention relates to the field of solid-state lithium batteries, and discloses a solid electrolyte fiber separator, its preparation method and application. (1) Solution I is electrospun to obtain electrospun membrane I, wherein solution I contains terephthalamide polymer and a first ionic liquid; (2) Electrospun membrane I is first contacted with a second ionic liquid to obtain electrospun membrane II; (3) Electrospun membrane II is second contacted with a lithium salt to obtain electrospun membrane III; (4) Electrospun membrane III is hot-pressed to obtain a solid electrolyte fiber separator. The separator provided by this invention has excellent comprehensive performance, especially high ionic conductivity, good thermal stability, electrochemical performance and mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of solid-state lithium batteries, specifically to a solid electrolyte fiber separator, its preparation method, and its application. Background Technology

[0002] The energy density of existing lithium-ion batteries using graphite anodes can no longer meet the demands of rapidly developing electric vehicles and portable electronic devices. Lithium has an energy density of 6.941 g·mol⁻¹. -1 Molar mass, theoretical specific capacity 3860mAh.g -1 It is 10 times more potent than graphite, and using lithium metal as the negative electrode can improve the specific energy of the battery. However, lithium inevitably undergoes uneven deposition in organic electrolytes and forms lithium dendrites, which can pierce the separator, causing a short circuit and leading to safety accidents. Therefore, secondary batteries using lithium metal as the negative electrode have not yet been commercialized.

[0003] All-solid-state lithium batteries replace flammable organic electrolytes with non-flammable solid electrolytes, offering advantages such as high safety and high energy density. They are considered the preferred direction for next-generation power and energy storage batteries. The solid electrolyte membrane is a crucial component of all-solid-state lithium batteries, replacing both liquid electrolytes and the membrane itself. It must meet certain requirements, including high ionic conductivity (>10) at room temperature. -4 The battery possesses good thermal stability, electrochemical performance, and mechanical properties to resist impacts during battery assembly and lithium dendrite damage during use.

[0004] Currently, solid electrolyte membranes can be divided into two types: inorganic solid electrolyte membranes and polymer solid electrolyte membranes. Compared to inorganic solid electrolyte membranes, polymer electrolyte membranes are easier to process and mold, making them suitable for large-scale industrial production and showing better development prospects. However, while existing polymer electrolyte membranes offer good safety, their poor contact with electrodes leads to high interfacial impedance. Furthermore, most polymer electrolytes have low room-temperature ionic conductivity, approximately 10⁻⁶. -7 -10 -4 The S / cm ratio is relatively low, making it difficult to meet the requirements 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 this invention is to overcome the above-mentioned defects in 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 overall performance.

[0007] To achieve the above objectives, a first aspect of the present invention provides a method for preparing a solid electrolyte fiber membrane, the method comprising:

[0008] (1) Electrospinning solution I to obtain electrospun membrane I, wherein solution I contains terephthalamide polymer and a first ionic liquid;

[0009] (2) The electrospun membrane I is brought into first contact with the second ionic liquid to obtain the electrospun membrane II;

[0010] (3) The electrospun film II is brought into a second contact with lithium salt to obtain electrospun film III;

[0011] (4) The electrospun membrane III is hot-pressed to obtain a solid electrolyte fiber diaphragm;

[0012] Wherein, the first ionic liquid is selected from at least one of carboxylate ionic liquid, chloride ionic liquid and bromide ionic liquid; the second ionic liquid is selected from one of bis(fluorosulfonyl)imide ionic liquid, bis(trifluoromethanesulfonyl)imide ionic liquid, tetrafluoroborate ionic liquid, hexafluorophosphate ionic liquid and difluorophosphate ionic liquid.

[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] A second aspect of the present invention provides a solid electrolyte fiber membrane obtained by the aforementioned method.

[0015] The third aspect of the present invention provides the application of the aforementioned solid electrolyte fiber separator in solid-state lithium batteries.

[0016] The solid electrolyte fiber separator provided by this invention has high room temperature ionic conductivity, which can meet the requirements of solid-state lithium-ion batteries. Furthermore, the solid electrolyte fiber separator provided by this invention also has good thermal stability, high tensile strength, and excellent electrochemical performance, exhibiting superior overall performance.

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

[0018] The endpoints and any values ​​of the ranges disclosed herein 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 the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0019] As previously described, a first aspect of the present invention provides a method for preparing a solid electrolyte fiber membrane, the method comprising:

[0020] (1) Electrospinning solution I to obtain electrospun membrane I, wherein solution I contains terephthalamide polymer and a first ionic liquid;

[0021] (2) The electrospun membrane I is brought into first contact with the second ionic liquid to obtain the electrospun membrane II;

[0022] (3) The electrospun film II is brought into a second contact with lithium salt to obtain electrospun film III;

[0023] (4) The electrospun membrane III is hot-pressed to obtain a solid electrolyte fiber diaphragm;

[0024] Wherein, the first ionic liquid is selected from at least one of carboxylate ionic liquid, chloride ionic liquid and bromide ionic liquid; the second ionic liquid is selected from one of bis(fluorosulfonyl)imide ionic liquid, bis(trifluoromethanesulfonyl)imide ionic liquid, tetrafluoroborate ionic liquid, hexafluorophosphate ionic liquid and difluorophosphate ionic liquid.

[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 terephthalamide-based polymer contains at least one group selected from sulfonic acid group, benzenesulfonic acid group, sulfonyl group, sulfonamide group, benzenesulfonamide group, aniline, benzidine, benzoic acid, terephthalic acid, p-phenylenediamine, 2,4-diaminotoluene, 2,6-diaminotoluene, m-xylenediamine, and p-xylenediamine. More preferably, the terephthalamide-based polymer is selected from at least one of disulfonic acid-benzidine-terephthalamide polymer, dibenzidine-benzidine-terephthalamide polymer, and disulfonamide-benzidine-terephthalamide polymer. Even more preferably, the weight-average molecular weight of the terephthalamide-based polymer is 8000-50000. According to the present invention, the terephthalamide-based polymer can be obtained commercially or prepared by methods existing 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-methylpyridine chloride, 1-ethyl-1-methylpyrrolidine chloride, 1-ethyl-3-methylimidazolium bromide, 1-propyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium bromide, N-propyl-N-methylpyridine 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 further includes preparing the solution I by the following steps:

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

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

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

[0032] Preferably, the second ionic liquid is selected from 1-ethyl-3-methylimidazolium bisfluorosulfonylimide salt, 1-propyl-3-methylimidazolium bisfluorosulfonylimide salt, 1-butyl-3-methylimidazolium bisfluorosulfonylimide salt, N-propyl-N-methylpyridine bisfluorosulfonylimide salt, 1-ethyl-1-methylpyrrolidine bisfluorosulfonylimide salt, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonylimide) salt, 1-propyl-3-methylimidazolium bis(trifluoromethanesulfonylimide) salt, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonylimide) salt, N-propyl-N-methylpyridine bis(trifluoromethanesulfonylimide) salt, 1-ethyl-1-methylpyrrolidine bis(trifluoromethanesulfonylimide) salt, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-propyl-3- At least one of the following: methylimidazolium 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. More preferably, the second ionic liquid is selected from 1-ethyl-3-methylimidazolium difluorosulfonylimide salt, 1-propyl-3-methylimidazolium difluorosulfonylimide salt, 1-butyl-3-methylimidazolium difluorosulfonylimide salt, 1-ethyl-3-methylimidazolium difluoromethanesulfonylimide salt, 1-propyl-3-methylimidazolium difluoromethanesulfonylimide salt, 1-butyl-3-methylimidazolium difluoromethanesulfonylimide salt, 1-ethyl-3-methylimidazolium tetra ... At least one of the following: 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 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 difluorosulfonylimide salt, and the lithium salt is lithium difluorosulfonylimide;

[0035] Combination 2: The first ionic liquid is 1-butyl-3-methylimidazolium acetate; the second ionic liquid is 1-butyl-3-methylimidazolium difluorosulfonylimide salt, the lithium salt is lithium difluorosulfonylimide, and the lithium salt is lithium bistrifluoromethanesulfonylimide.

[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 salt, and the lithium salt is lithium bis(trifluoromethanesulfonyl)imide.

[0037] The inventors of this invention have discovered that solid electrolyte fiber membranes obtained by specifically selecting the combination of the first ionic liquid, the second ionic liquid, and the lithium salt have superior performance, such as higher ionic conductivity.

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

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

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

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

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

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

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

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

[0046] As previously stated, a second aspect of the present invention provides a solid electrolyte fiber membrane obtained by the aforementioned method.

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

[0048] The solid electrolyte fiber provided by this invention has excellent overall performance, especially high ionic 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 application of the aforementioned solid electrolyte fiber separator in solid-state lithium batteries.

[0050] Solid-state lithium batteries obtained using the solid electrolyte fiber separator provided by this invention exhibit excellent electrochemical performance, high capacity retention, and superior rate performance.

[0051] Unless otherwise specified, all pressures in this invention refer to gauge pressure, and room temperature refers to 25±2℃.

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

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

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

[0055] The ionic liquids used in the following examples were all purchased from TCI Corporation; the lithium salts used were all purchased from Shenzhen Capchem Technology Co., Ltd.

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

[0057] (1) Mix 0.02 mol diaminobiphenyl-disulfonic acid, 0.04 mol cesium hydroxide monohydrate, and 0.02 mol sodium carbonate in 150 ml of deionized water and stir thoroughly until dissolved. Then add 30 ml of toluene to obtain mixture A.

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

[0059] (3) Add mixture B to mixture A under high speed stirring, stop stirring after 3 minutes, add 150 ml of ethanol, filter and wash twice with 200 ml of ethanol to obtain disulfonic acid-benzidine-terephthalamide polymer;

[0060] The weight-average molecular weight (Mw) of the disulfonic acid-benzidine-terephthalamide polymer was determined by GPC (methodological chromatography) to be 17,000. The specific test conditions were as follows: the column temperature was controlled at 40°C using a thermostat, the flow rate was 0.6 ml / min, and sodium poly(p-styrene sulfonate) was used as the GPC standard.

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

[0062] The diphenylsulfonic acid-benzidine-terephthalamide polymer was prepared using a method similar to that used in Preparation Example A, except that the diaminobiphenyl-disulfonic acid was replaced with diaminobiphenyl-diphenylsulfonic acid. The molecular weight of the diphenylsulfonic acid-benzidine-terephthalamide polymer was determined by GPC to be Mw = 23400.

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

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

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

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

[0067] (1) Mix 0.02 mol diaminobiphenyl-disulfonic acid, 0.02 mol cesium hydroxide monohydrate, and 0.01 mol sodium carbonate in 300 ml of deionized water and stir thoroughly until dissolved. Then add 30 ml of toluene to obtain mixture A.

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

[0069] (3) Add mixture B to mixture A under high speed stirring, stop stirring after 1 minute, add 150 ml of ethanol, filter and wash twice with 200 ml of ethanol to obtain disulfonic acid-benzidine-terephthalamide polymer;

[0070] The molecular weight (Mw) of the obtained disulfonic acid-benzidine-terephthalamide polymer was determined to be 4000 using GPC.

[0071] Example 1

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

[0073] (2) The obtained electrospun membrane I was immersed in 10g of 1-ethyl-3-methylimidazolium difluorosulfonyl imide salt ionic liquid at room temperature for a first contact time of 24 hours to obtain electrospun membrane II.

[0074] (3) The obtained electrospun membrane II was subjected to a second contact with 0.5g of lithium difluorosulfonyl imide at room temperature for ion exchange. 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 electrospun membrane III.

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

[0076] Example 2

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

[0078] (2) The obtained electrospun membrane I was immersed in 6g of 1-butyl-3-methylimidazolium difluorosulfonyl imide salt ionic liquid at room temperature for a first contact time of 24 hours to obtain electrospun membrane II.

[0079] (3) The obtained electrospun membrane II was subjected to a second contact with 1g of lithium difluorosulfonyl imide at room temperature for ion exchange for 24 hours; the membrane material after ion exchange was vacuum dried for 24 hours at a drying temperature of 70°C to obtain electrospun membrane III.

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

[0081] Example 3

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

[0083] (2) The obtained electrospun membrane I was immersed in 10g of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt ionic liquid at room temperature for a first contact time of 24 hours to obtain electrospun membrane II.

[0084] (3) The obtained electrospun membrane II was subjected to a second contact with 1.5g of lithium bis(trifluoromethanesulfonyl)imide at room temperature for 24 hours to carry out ion exchange. The membrane material after ion exchange was vacuum dried for 24 hours at a drying temperature of 60°C to obtain electrospun membrane III.

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

[0086] Example 4

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

[0088] Example 5

[0089] Using a method similar to that of Example 1, the only difference is that: an equal mass of 1-ethyl-1-methylpyrrolidine acetate ionic liquid is used instead of the first ionic liquid in Example 1, an equal mass of 1-ethyl-1-methylpyrrolidine tetrafluoroborate ionic liquid is used instead of the second ionic liquid in Example 1, and the lithium salt is replaced with an equal mass of lithium tetrafluoroborate to obtain a solid electrolyte fiber membrane.

[0090] Example 6

[0091] A solid electrolyte fiber membrane was prepared using a method similar to that in 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-methylimidazolium acetate was used instead of the first ionic liquid in Example 1, and an equal mass of N-propyl-N-methylpyridine difluorosulfonylimide salt was used instead of the second ionic liquid in Example 1.

[0094] Comparative Example 2

[0095] A solid electrolyte fiber membrane was prepared using a method similar to that in Example 1, except that lithium hexafluorophosphate of equal mass was used instead of lithium difluorosulfonyl imide in 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, and 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, with a test frequency range of 0.001 Hz-10 Hz. 5 The test frequency was Hz, and the test temperature was room temperature (25℃). The conductivity (σ) was then 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), and R b A is the bulk resistance of the diaphragm (Ω), and A is the effective contact area between the diaphragm and the electrode (cm²). 2 ).

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

[0102] (3) Thickness: The thickness was measured using a thickness gauge (accuracy 0.1 micrometers). Five points were randomly selected on the sample and the average value was taken.

[0103] (4) Heat shrinkage rate: The dimensional heat shrinkage rate was determined by oven drying. The sample was heat-treated at 150℃ for 1 hour, and then the heat shrinkage rate (δ) was calculated according to the formula:

[0104]

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

[0106] Table 1

[0107] Example Thickness / μm Ionic conductivity / mS / cm Tensile strength / MPa thermal shrinkage rate 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 performance of the batteries were tested. The test results are shown in Table 2 below.

[0109] Solid-state lithium battery fabrication:

[0110] The positive electrode formulation 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 following order: negative electrode shell, lithium metal negative electrode, solid electrolyte composite separator, positive electrode, stainless steel sheet, spring sheet, and positive electrode shell.

[0111] Solid-state lithium batteries were charged and discharged at a rate of 1C within the range of 2.8-4.2V, and batteries assembled with commercial liquid electrolyte and PP separator were 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 separator provided by this invention has high room temperature ionic conductivity, which can meet the requirements of solid-state lithium-ion batteries. Furthermore, the solid electrolyte fiber separator provided by this invention also has good thermal stability, high tensile strength, and excellent electrochemical performance, exhibiting superior overall performance.

[0115] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within 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 solution I to obtain electrospun membrane I, wherein solution I contains terephthalamide polymer and a first ionic liquid; (2) The electrospun membrane I is brought into first contact with the second ionic liquid to obtain the electrospun membrane II; (3) The electrospun film II is brought into a second contact with lithium salt to obtain electrospun film III; (4) The electrospun membrane III is hot-pressed to obtain a solid electrolyte fiber diaphragm; Wherein, the first ionic liquid is selected from at least one of carboxylate ionic liquid, chloride ionic liquid and bromide ionic liquid; the second ionic liquid is selected from one of bis(fluorosulfonyl)imide ionic liquid, bis(trifluoromethanesulfonyl)imide ionic liquid, tetrafluoroborate ionic liquid, hexafluorophosphate ionic liquid and difluorophosphate ionic liquid. 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 terephthalamide polymer contains groups selected from at least one of sulfonic acid group, benzenesulfonic acid group, sulfonyl group, sulfonamide group, benzenesulfonamide group, aniline, benzidine, benzoic acid, terephthalic acid, p-phenylenediamine, 2,4-diaminotoluene, 2,6-diaminotoluene, m-xylenediamine, and p-xylenediamine.

3. The method according to claim 1, wherein, The terephthalamide-based polymer is selected from at least one of disulfonic acid-benzidine-terephthalamide polymer, dibenzylsulfonic acid-benzidine-terephthalamide polymer, and disulfonamide-benzidine-terephthalamide polymer.

4. The method according to claim 1, wherein, The weight-average molecular weight of the terephthalamide-based polymer is 8,000-50,000.

5. The method according to claim 1, 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-methylpyridine chloride, 1-ethyl-1-methylpyrrolidine chloride, 1-ethyl-3-methylimidazolium bromide, 1-propyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium bromide, N-propyl-N-methylpyridine bromide, and 1-ethyl-1-methylpyrrolidine bromide.

6. The method according to claim 1, 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, 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.

7. The method according to claim 1, wherein, The second ionic liquid is selected from 1-ethyl-3-methylimidazolium difluorosulfonylimide salt, 1-propyl-3-methylimidazolium difluorosulfonylimide salt, 1-butyl-3-methylimidazolium difluorosulfonylimide salt, N-propyl-N-methylpyridine difluorosulfonylimide salt, 1-ethyl-1-methylpyrrolidine difluorosulfonylimide salt, 1-ethyl-3-methylimidazolium difluoromethanesulfonylimide salt, 1-propyl-3-methylimidazolium difluoromethanesulfonylimide salt, 1-butyl-3-methylimidazolium difluoromethanesulfonylimide salt, N-propyl-N-methylpyridine difluoromethanesulfonylimide salt, 1-ethyl-1-methylpyrrolidine difluoromethanesulfonylimide salt, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-propyl-3-methylimidazolium difluorosulfonylimide salt, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium difluorosulfonylimide salt, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium tetrafluoromethanesulfonylimide salt ... At least one of the following: 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.

8. The method according to claim 1, wherein, The second ionic liquid is selected from 1-ethyl-3-methylimidazolium difluorosulfonylimide salt, 1-propyl-3-methylimidazolium difluorosulfonylimide salt, 1-butyl-3-methylimidazolium difluorosulfonylimide salt, 1-ethyl-3-methylimidazolium difluoromethanesulfonylimide salt, 1-propyl-3-methylimidazolium difluoromethanesulfonylimide salt, 1-butyl-3-methylimidazolium difluoromethanesulfonylimide salt, and 1-ethyl-3-methylimidazolium tetrafluoroboron. The salt, 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.

9. The method according to claim 1, 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 difluorosulfonylimide salt, and the lithium salt is lithium difluorosulfonylimide; Combination 2: The first ionic liquid is 1-butyl-3-methylimidazolium acetate; the second ionic liquid is 1-butyl-3-methylimidazolium difluorosulfonylimide salt, and the lithium salt is lithium difluorosulfonylimide; Combination 3: The first ionic liquid is 1-ethyl-3-methylimidazolium acetate; the second ionic liquid is 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt, and the lithium salt is lithium bis(trifluoromethanesulfonyl)imide.

10. The method according to any one of claims 1-9, wherein, In step (1), the weight ratio of the first ionic liquid to the terephthalamide polymer is 1-50:1; And / or, in step (2), the weight ratio of the second ionic liquid to the terephthalamide polymer is 50-200:1; And / or, in step (3), the weight ratio of the lithium salt to the terephthalamide polymer is 1-15:

1.

11. The method according to any one of claims 1-9, wherein, In step (1), the conditions for electrospinning include: spinning voltage of 10-30kV, receiving distance of 10-30cm, humidity of 20-60%, and temperature of 20-50℃. And / or, in step (2), the conditions for the first contact include: temperature 20-50°C, time 12-48h; And / or, in step (3), the conditions for the second contact include: temperature 20-50°C, time 12-48h; And / or, in step (4), the hot pressing conditions include: a hot pressing temperature of 50-120°C and a hot pressing time of 2-30 minutes.

12. A solid electrolyte fiber membrane prepared by the method according to any one of claims 1-11.

13. The solid electrolyte fiber membrane according to claim 12, wherein, The solid electrolyte fiber diaphragm has a room temperature ionic conductivity of 1-4 mS / cm, a tensile strength of 20-60 MPa, and a thermal shrinkage rate of <5%.

14. The solid electrolyte fiber membrane according to claim 12, wherein, The solid electrolyte fiber membrane has a room temperature ionic conductivity of 2.5-4 mS / cm.

15. The solid electrolyte fiber membrane according to claim 12, wherein, The tensile strength of the solid electrolyte fiber diaphragm is 40-60 MPa.

16. The solid electrolyte fiber membrane according to claim 12, wherein, The thermal shrinkage rate of the solid electrolyte fiber diaphragm is <3%.

17. The application of the solid electrolyte fiber separator according to any one of claims 12-16 in a solid-state lithium battery.

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