High-strength porous polymer electrolyte membrane and preparation method and application thereof

Abstract

The invention belongs to the technical field of electrolyte materials, and discloses a high-strength porous polymer electrolyte membrane as well as a preparation method and application thereof. The preparation method comprises the following steps: mixing polyvinylidene fluoride, polyacrylonitrile, a pore forming agent, a filler and a solvent to obtain a mixed solution; performing electrostatic spinning on the mixed solution to obtain a nanofiber membrane; and soaking the obtained nanofiber membrane in a pore-forming agent remover, taking out the nanofiber membrane, and sequentially performing activation and heat treatment to obtain the porous polymer electrolyte membrane. The obtained porous polymer electrolyte membrane has longer service life, higher power density and better safety in a lithium ion battery and a solid-state battery.

Description

Technical Field

[0001] The present invention relates to the technical field of electrolyte materials, and in particular to a high-strength porous polymer electrolyte membrane and a preparation method and application thereof. Background Art

[0002] As the application of lithium-ion batteries and solid-state batteries continues to expand, the demand for battery performance in existing technologies has also increased. As an important component of the battery, the performance of the electrolyte membrane directly affects the energy density, cycle life and safety of the battery. Existing polymer electrolyte membranes usually have the following problems: (1) Poor mechanical properties: The membrane is prone to breakage or deformation during the cycle, affecting the stability of the battery; (2) Uneven pore structure: The porosity and pore size distribution of the membrane are uneven, which makes ion migration difficult and affects the ionic conductivity of the electrolyte.

[0003] Therefore, it is of great significance to study a high-strength porous polymer electrolyte membrane with excellent mechanical properties and uniform pore structure distribution and its preparation method. Summary of the invention

[0004] In view of this, the present invention provides a high-strength porous polymer electrolyte membrane and a preparation method and application thereof, the purpose of which is to solve the problems of poor mechanical properties and uneven pore structure of the polymer electrolyte membrane in the prior art.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] The present invention provides a method for preparing a high-strength porous polymer electrolyte membrane, comprising the following steps:

[0007] 1) mixing polyvinylidene fluoride, polyacrylonitrile, a pore-forming agent, a filler and a solvent to obtain a mixed solution;

[0008] 2) electrospinning the mixed solution to obtain a nanofiber membrane;

[0009] 3) The obtained nanofiber membrane is immersed in a pore-forming agent remover, taken out, and then activated and heat-treated in sequence to obtain a porous polymer electrolyte membrane.

[0010] Preferably, in step 1), the pore-forming agent is polyethylene glycol and / or nano-silicon dioxide; the filler is nano-silicon dioxide, alumina or graphene; and the solvent is N,N-dimethylformamide or N-methylpyrrolidone.

[0011] Preferably, in step 1), the mass ratio of polyvinylidene fluoride to polyacrylonitrile is 1-2:2-4;

[0012] The mass ratio of polyvinylidene fluoride to polyacrylonitrile, pore-forming agent, filler and solvent is 10-20:5-15:3-7:100.

[0013] Preferably, in step 1), the mixing is ultrasonic mixing, the power of ultrasonic mixing is 200-500W, the time of ultrasonic mixing is 20-60min, and the temperature of ultrasonic mixing is 20-40°C.

[0014] Preferably, in step 2), the voltage of electrospinning is 15 to 20 kV, the speed of electrospinning is 0.5 to 1 mL / h, and the working distance of electrospinning is 12 to 20 cm.

[0015] Preferably, in step 3), the pore-forming agent remover is ethanol and / or water;

[0016] The soaking temperature is 40-60° C., and the soaking time is 30-120 min.

[0017] Preferably, in step 3), activation is performed by immersing in an electrolyte for 1 to 4 hours;

[0018] The electrolyte comprises a lithium-containing compound and a solvent, wherein the lithium-containing compound is lithium hexafluorophosphate or lithium bis(trifluoromethylsulfonyl)imide, and the solvent is one or more of polycarbonate, ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate; and the concentration of the electrolyte is 0.8-1.2 mol / L.

[0019] Preferably, in step 3), the heat treatment temperature is 100-120° C., and the heat treatment time is 1-2 hours.

[0020] The invention also provides a porous polymer electrolyte membrane prepared by the method for preparing a high-strength porous polymer electrolyte membrane.

[0021] The invention also provides application of the porous polymer electrolyte membrane in a battery.

[0022] It can be seen from the above technical solutions that, compared with the prior art, the present invention has the following beneficial effects:

[0023] The method for preparing the porous polymer electrolyte membrane of the present invention fully combines the technical advantages of mechanical property enhancement and pore structure regulation. Through process parameter control and material selection, the membrane optimizes the pore structure and improves the liquid conductivity while maintaining high mechanical strength. The preparation method can mass-produce electrolyte membranes with higher strength and better liquid conductivity.

[0024] The porous polymer electrolyte membrane obtained by the present invention has longer service life, higher power density and better safety in lithium ion batteries and solid-state batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0026] Figure 1 The present invention is a flow chart of the preparation process of the porous polymer electrolyte membrane. DETAILED DESCRIPTION

[0027] The present invention provides a method for preparing a high-strength porous polymer electrolyte membrane, comprising the following steps:

[0028] 1) mixing polyvinylidene fluoride, polyacrylonitrile, a pore-forming agent, a filler and a solvent to obtain a mixed solution;

[0029] 2) electrospinning the mixed solution to obtain a nanofiber membrane;

[0030] 3) The obtained nanofiber membrane is immersed in a pore-forming agent remover, taken out, and then activated and heat-treated in sequence to obtain a porous polymer electrolyte membrane.

[0031] In the present invention, the pore-forming agent in step 1) is preferably polyethylene glycol and / or nano-silica; the filler is preferably nano-silica, alumina or graphene; and the solvent is preferably N,N-dimethylformamide or N-methylpyrrolidone.

[0032] In the present invention, in the step 1), the mass ratio of polyvinylidene fluoride to polyacrylonitrile is preferably 1-2:2-4, more preferably 1.2-1.8:2.5-3.5, and more preferably 1.5-1.6:3;

[0033] The mass ratio of polyvinylidene fluoride to polyacrylonitrile, the pore former, the filler and the solvent is preferably 10 to 20:5 to 15:3 to 7:100, more preferably 12 to 18:7 to 13:4 to 6:100, and even more preferably 15 to 16:9 to 10:5:100.

[0034] In the present invention, polyvinylidene fluoride and polyacrylonitrile are compounded to form the substrate of the nanofiber membrane; the pore structure of the nanofiber membrane is regulated by adding a pore-forming agent, and the addition of fillers enhances the mechanical properties of the nanofiber membrane.

[0035] In the present invention, in the step 1), the mixing order is preferably to first mix the polyvinylidene fluoride, polyacrylonitrile and the solvent, and then add the pore former and the filler.

[0036] In the present invention, in the step 1), the mixing is preferably ultrasonic mixing, the power of the ultrasonic mixing is preferably 200-500 W, more preferably 250-450 W, more preferably 300-400 W, the time of ultrasonic mixing is preferably 20-60 min, more preferably 30-50 min, more preferably 40-45 min, the temperature of ultrasonic mixing is preferably 20-40° C., more preferably 25-35° C., more preferably 30-33° C.; ultrasonic mixing is preferably intermittent ultrasound, and the intermittent ultrasound is preferably ultrasound for 10 min and standing for 2 min.

[0037] In the present invention, the power of the ultrasonic mixing is set to 200-500W, which is conducive to the ultrasonic wave providing sufficient energy to break the agglomerates and make the pore-forming agent uniformly dispersed; the ultrasonic mixing time is 20-60min, which can ensure the uniform dispersion of the pore-forming agent and avoid the solution decomposition or polymer chain breakage caused by too long ultrasonic time; the intermittent ultrasound can prevent the solution from being overheated due to ultrasound and affecting the uniformity and stability of the mixed solution system.

[0038] In the present invention, in the step 2), the voltage of electrospinning is preferably 15 to 20 kV, more preferably 16 to 19 kV, and more preferably 17 to 18 kV. The speed of electrospinning is preferably 0.5 to 1 mL / h, more preferably 0.6 to 0.9 mL / h, and more preferably 0.7 to 0.8 mL / h. The working distance of electrospinning is preferably 12 to 20 cm, more preferably 14 to 18 cm, and more preferably 15 to 16 cm.

[0039] In the present invention, in the step 3), the pore-forming agent remover is preferably ethanol and / or water. When the pore-forming agent remover is a mixed solution of ethanol and water, the mass ratio of ethanol to water is preferably 55-65:35-45, more preferably 58-64:36-42, and more preferably 60-62:38-40;

[0040] The soaking temperature is preferably 40-60°C, more preferably 45-55°C, more preferably 50-52°C, and the soaking time is preferably 30-120 min, more preferably 60-100 min, more preferably 80-90 min.

[0041] In the present invention, in the step 3), the nanofiber membrane is taken out after being immersed in the pore-forming agent remover, and is washed and dried in sequence; the washing reagent is preferably water, and the number of washings is preferably 3 to 5 times. When the pore-forming agent remover is water, no washing is required; the drying time is preferably 30 to 120 minutes, more preferably 60 to 100 minutes, and more preferably 80 to 90 minutes. The drying temperature is preferably 60 to 80°C, more preferably 65 to 75°C, and more preferably 70 to 72°C.

[0042] In the present invention, in the step 3), activation is performed by immersing in an electrolyte, and the activation time is preferably 1 to 4 hours, more preferably 1.5 to 3.5 hours, and more preferably 2 to 3 hours;

[0043] The electrolyte comprises a lithium-containing compound and a solvent, the lithium-containing compound is preferably lithium hexafluorophosphate (LiPF6) or lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), and the solvent is preferably one or more of polycarbonate, ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate; the concentration of the electrolyte is preferably 0.8 to 1.2 mol / L, further preferably 0.9 to 1.1 mol / L, and more preferably 1 mol / L.

[0044] In the present invention, in step 3), the heat treatment temperature is preferably 100-120°C, more preferably 105-115°C, more preferably 110-112°C, and the heat treatment time is preferably 1-2h, more preferably 1.5h.

[0045] The invention also provides a porous polymer electrolyte membrane prepared by the method for preparing a high-strength porous polymer electrolyte membrane.

[0046] The invention also provides application of the porous polymer electrolyte membrane in a battery.

[0047] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0048] In the embodiments of the present invention, the numbers are all by mass.

[0049] Example 1

[0050] 3.75 parts of polyvinylidene fluoride, 11.25 parts of polyacrylonitrile and 100 parts of N,N-dimethylformamide were mixed, and then 10 parts of polyethylene glycol (molecular weight 4000) and 5 parts of aluminum oxide were added, and ultrasonically mixed at 30° C. for 30 min at a power of 300 W, and the mixture was allowed to stand for 2 min after every 10 min of ultrasonication (the standing time was not included in the ultrasonic mixing time), to obtain a mixed solution;

[0051] The mixed solution was placed in an electrospinning device (setting parameters: voltage 17 kV, working distance 15 cm, injection rate 0.6 mL / h) for electrospinning to obtain a nanofiber membrane;

[0052] The obtained nanofiber membrane was immersed in water at 40°C for 60 minutes, and then taken out and dried at 60°C for 60 minutes to obtain a porous membrane;

[0053] The porous membrane was immersed in 1 mol / L LiPF6 electrolyte (solvent is ethylene carbonate) for activation for 2 h, and then heat treated at 120°C for 2 h to obtain a porous polymer electrolyte membrane.

[0054] Example 2

[0055] 7.2 parts of polyvinylidene fluoride, 10.8 parts of polyacrylonitrile and 100 parts of N,N-dimethylformamide were mixed, and then 8 parts of polyethylene glycol (molecular weight 4000) and 3 parts of aluminum oxide were added, and ultrasonically mixed at 30° C. for 30 min at a power of 300 W, and the mixture was allowed to stand for 2 min after every 10 min of ultrasonication (the standing time was not included in the ultrasonic mixing time), to obtain a mixed solution;

[0056] The mixed solution was placed in an electrospinning device (setting parameters: voltage 18 kV, working distance 18 cm, injection rate 0.8 mL / h) for electrospinning to obtain a nanofiber membrane;

[0057] The obtained nanofiber membrane was immersed in anhydrous ethanol at 50°C for 60 minutes, then taken out and washed with water for 5 times, and dried at 60°C for 30 minutes after washing to obtain a porous membrane;

[0058] The porous membrane was immersed in 1 mol / L LiPF6 electrolyte (the solvent was ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1) for activation for 3 h, and then heat-treated at 110°C for 1.5 h to obtain a porous polymer electrolyte membrane.

[0059] Example 3

[0060] 4 parts of polyvinylidene fluoride, 8 parts of polyacrylonitrile and 100 parts of N-methylpyrrolidone were mixed, and then 5 parts of polyethylene glycol (molecular weight 2000) and 5 parts of nano-silicon dioxide were added, and ultrasonically mixed at 30°C for 20 minutes at a power of 250 W, and the mixture was allowed to stand for 2 minutes every 10 minutes of ultrasonication (the standing time was not included in the ultrasonic mixing time) to obtain a mixed solution;

[0061] The mixed solution was placed in an electrospinning device (setting parameters: voltage 16 kV, working distance 14 cm, injection rate 0.5 mL / h) for electrospinning to obtain a nanofiber membrane;

[0062] The obtained nanofiber membrane was immersed in water at 50°C for 45 min, and then dried at 70°C for 60 min to obtain a porous membrane;

[0063] The porous membrane was immersed in 1 mol / L LiPF6 electrolyte (the solvent was ethylene carbonate and dimethyl carbonate in a volume ratio of 1:2) for activation for 2 h, and then heat-treated at 100°C for 2 h to obtain a porous polymer electrolyte membrane.

[0064] Example 4

[0065] 3 parts of polyvinylidene fluoride, 12 parts of polyacrylonitrile and 100 parts of N,N-dimethylformamide were mixed, and then 7 parts of polyethylene glycol (molecular weight of 2000) and 3 parts of graphene were added, and ultrasonically mixed at 30°C for 40 minutes at a power of 400 W, and the mixture was allowed to stand for 2 minutes every 10 minutes of ultrasonication (the standing time was not included in the ultrasonic mixing time) to obtain a mixed solution;

[0066] The mixed solution was placed in an electrospinning device (setting parameters: voltage 20 kV, working distance 15 cm, injection rate 0.7 mL / h) for electrospinning to obtain a nanofiber membrane;

[0067] The obtained nanofiber membrane was immersed in a pore-forming agent remover (a mixed solution of anhydrous ethanol and water, with a mass ratio of anhydrous ethanol to water of 60:40) at 50°C for 60 minutes, and then dried at 60°C for 60 minutes to obtain a porous membrane;

[0068] The porous membrane was immersed in 1 mol / L LiPF6 electrolyte (solvent is polycarbonate) for activation for 2 h, and then heat treated at 120°C for 1 h to obtain a porous polymer electrolyte membrane.

[0069] Example 5

[0070] The electrolyte in Example 1 is replaced with "1 mol / L LiPF6 electrolyte (the solvent is ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1)", and the other steps are the same as Example 1.

[0071] Example 6

[0072] The electrolyte in Example 3 was replaced with "1 mol / L LiTFSI electrolyte (the solvent was polycarbonate and dimethyl carbonate in a volume ratio of 1:2)", and the other steps were the same as in Example 1.

[0073] Example 7

[0074] The electrolyte in Example 1 is replaced by "1 mol / L LiPF6 electrolyte (the solvent is ethyl methyl carbonate)", and "5 parts of aluminum oxide" is replaced by "2.5 parts of aluminum oxide and 2.5 parts of silicon dioxide", and the other steps are the same as Example 1.

[0075] The porous polymer electrolyte membranes obtained in Examples 1 to 7 were subjected to mechanical property tests, porosity tests, pore size distribution tests, anti-aging performance tests, mechanical strength retention rate tests, ionic conductivity tests, battery performance tests, charge and discharge efficiency tests, and electrochemical stability window tests. The specific test steps and test results are as follows:

[0076] Mechanical property test: According to GB / T1040.1-2006 "Determination of tensile properties of plastics", the porous polymer electrolyte membranes obtained in Examples 1 to 7 were cut into standard tensile strips of 5 mm width and 30 mm length, respectively, and the tensile strength and elongation at break of the porous polymer electrolyte membranes obtained in Examples 1 to 7 were recorded on a tensile machine with a clamping distance of 20 mm and a test speed of 50 mm / min. The test results are shown in Table 1:

[0077] Table 1 Mechanical properties test results of porous polymer electrolyte membranes obtained in Examples 1 to 7

[0078]

[0079] As shown in Table 1, the tensile strength of the porous polymer electrolyte membrane obtained in the present invention is greater than 55MPa, and the elongation at break is between 28% and 36%. Compared with the common polymer electrolyte membrane, the porous polymer electrolyte membrane obtained in the present invention has good toughness and strength. It can be seen that the addition of nanofillers in the present invention enhances the mechanical strength of the membrane; by adding nanofillers such as aluminum oxide (Al2O3) and graphene, the mechanical strength of the membrane is enhanced, the membrane is prevented from breaking or deforming during the battery charging and discharging process, and the cycle life and safety of the battery are improved.

[0080] Porosity and pore size distribution detection: The porosity and pore size distribution of the porous polymer electrolyte membranes obtained in Examples 1 to 7 were tested by scanning electron microscopy (SEM) and nitrogen adsorption method (BET method). The test results are shown in Table 2.

[0081] Filler dispersion test: Take the dried membrane samples of the porous polymer electrolyte membrane obtained in Examples 1 to 7, break them in a liquid nitrogen environment to obtain a cross section, spray gold on the membrane surface for 60 seconds, and use a scanning electron microscope with an acceleration voltage of 5 to 10 kV to obtain the morphology. The test results are shown in Table 2.

[0082] Anti-aging performance test: The porous polymer electrolyte membranes obtained in Examples 1 to 7 were subjected to an aging performance test at a high temperature of 150° C. for 500 h. The test results are shown in Table 2.

[0083] Mechanical strength retention test: The porous polymer electrolyte membranes obtained in Examples 1 to 7 were subjected to 500 repeated bending tests to detect the mechanical strength retention of the porous polymer electrolyte membranes. The test results are shown in Table 2.

[0084] Table 2 Performance test results of porous polymer electrolyte membranes obtained in Examples 1 to 7

[0085]

[0086] As can be seen from Table 2, the porosity of the porous polymer electrolyte membranes obtained in Examples 1 to 7 is 35-45%, and increasing the porosity of the polymer electrolyte membrane can improve the wettability of the electrolyte and the ion conductivity, so that the porous polymer electrolyte membrane can provide a smoother ion migration channel and improve the discharge efficiency and rate performance of the battery. The porosity of the membrane using polyethylene glycol as a pore-forming agent is 45%, while that of SiO2 is 40%. The difference in ionic conductivity between the two is small, which is 1.6×10 -3 / cm and 1.5×10 -3 S / cm, but the addition of polyethylene glycol performed better in terms of the uniformity of membrane pores and membrane flexibility.

[0087] The nanofillers are relatively evenly dispersed in the fiber matrix or surface, greatly improving the mechanical properties, thermal stability and ion transport channels of the membrane.

[0088] The pore size distribution is concentrated between 100 and 300 nm, which meets the high conductivity requirements of the electrolyte membrane, and the specific surface area is between 58 and 70 m 2 / g, further verifying the high porosity and good ion migration performance of the membrane.

[0089] After high-temperature aging test at 150°C, the porous polymer electrolyte membrane still maintains good mechanical properties and pore structure, is adaptable to battery operation in high-temperature environments, and has strong anti-fatigue ability.

[0090] After 500 repeated bending tests, the mechanical strength retention rate of the porous polymer electrolyte membrane exceeded 90%. It can be seen that the porous polymer electrolyte membrane obtained by the present invention has strong fatigue resistance and can adapt to battery operation in high temperature environments.

[0091] Ionic conductivity test: The porous polymer electrolyte membranes obtained in Examples 1 to 7 were cut into discs with a diameter of 16 mm, placed in a dry environment, sandwiched between two stainless steel electrodes, and placed in a special fixture. EIS tests were performed on an electrochemical workstation with a frequency range of 0.1 Hz to 1 MHz and an AC amplitude of 10 mV. The impedance spectra of the discs were measured at 25°C and 50°C, respectively, and the ionic conductivity σ was calculated by formula (I). The test results are shown in Table 3.

[0092] σ=d / (Rb·A) Formula (I);

[0093] Rb is the film body resistance, d is the film thickness, and A is the electrode effective area.

[0094] Table 3 Ionic conductivity of porous polymer electrolyte membranes obtained in Examples 1 to 7

[0095]

[0096]

[0097] As shown in Table 3, the ionic conductivity of the porous polymer electrolyte membrane obtained in Example 1 is 1.6×10 - 3 S / cm, increased to 2.3×10 at 50℃ -3 S / cm. This data shows that the porous polymer electrolyte membrane obtained by the present invention has good electrical conductivity at different operating temperatures, and the optimization of the pore structure has a significant improvement in ionic conductivity.

[0098] Electrochemical stability and charge and discharge efficiency test: The test was conducted in accordance with GB / T18287-2000 “General specification for lithium-ion batteries and battery packs for mobile phones”. The test results are shown in Table 4.

[0099] Electrochemical stability window test: The porous polymer electrolyte membranes obtained in Examples 1 to 7 were subjected to the following steps:

[0100] A Pt sheet was used as the working electrode and metallic lithium was used as the counter electrode to assemble the test fixture; the porous polymer electrolyte membrane contained the corresponding electrolyte. The starting potential was set to 2.5V (vs. Li / Li+), and the scan was performed to 5.0V at a scan rate of 5mV / s. The voltage at which an obvious oxidation current appeared in the high potential range was recorded, which was the oxidation decomposition potential of the electrolyte, i.e., the upper limit of the stability window. The test results are shown in Table 4.

[0101] Table 4 Test results of electrical properties of porous polymer electrolyte membranes obtained in Examples 1 to 7

[0102]

[0103]

[0104] As can be seen from Table 4, the porous polymer electrolyte membrane obtained by the present invention improves the initial capacity, rate performance and cycle stability of the battery by adding different types of nanofillers. Alumina fillers are particularly effective in improving mechanical strength, while graphene helps to improve the conductivity of the battery.

[0105] After 100 cycle tests, the capacity retention rate and the initial capacity can reach 96% and 150mAh / g respectively, which shows that the obtained porous polymer electrolyte membrane has excellent cycle stability; the charge and discharge efficiency at a rate of 0.5C can reach 98%, showing good rate performance and stable battery performance; at a rate of 3C, the battery's discharge specific capacity is still maintained at more than 130mAh / g, which is significantly better than most existing electrolyte membranes, indicating that the obtained porous polymer electrolyte membrane can meet the high-rate discharge requirements and is suitable for battery applications with high power requirements.

[0106] The electrochemical stability window test shows that the porous polymer electrolyte membrane obtained by the present invention shows a wide electrochemical stability window (>4.5V vs.Li / Li + ), that is, the obtained porous polymer electrolyte membrane can work stably at a higher voltage and is suitable for high-voltage battery systems.

[0107] Differential scanning calorimetry test: 5 mg of the dried porous polymer electrolyte membranes prepared in Examples 1 to 7 were placed in a DSC sample dish and nitrogen was introduced for protection. The temperature was set at 30 to 250°C, the temperature increase rate was 10°C / min, and the endothermic / exothermic peaks were recorded. The test results are shown in Table 5.

[0108] Table 5 Differential scanning calorimetry test results of porous polymer electrolyte membranes prepared in Examples 1 to 7

[0109]

[0110]

[0111] It can be seen from Table 5 that the melting temperature of the porous polymer electrolyte membrane obtained in the present invention is between 168 and 178°C, which is significantly higher than the melting temperature of 120 to 140°C of common polyolefin membranes, that is, the porous polymer electrolyte membrane obtained in the present invention has better thermal stability and safety under high temperature conditions.

[0112] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a high-strength porous polymer electrolyte membrane, characterized in that: The steps include: 1) mixing polyvinylidene fluoride, polyacrylonitrile, a pore-forming agent, a filler and a solvent to obtain a mixed solution; 2) electrospinning the mixed solution to obtain a nanofiber membrane; 3) The obtained nanofiber membrane is immersed in a pore-forming agent remover, taken out, and then activated and heat-treated in sequence to obtain a porous polymer electrolyte membrane.

2. The method for preparing a high-strength porous polymer electrolyte membrane according to claim 1, characterized in that: Step 1) The pore-forming agent is polyethylene glycol and / or nano-silicon dioxide; the filler is nano-silicon dioxide, alumina or graphene; and the solvent is N,N-dimethylformamide or N-methylpyrrolidone.

3. The method for preparing a high-strength porous polymer electrolyte membrane according to claim 2, characterized in that: In the step 1), the mass ratio of polyvinylidene fluoride to polyacrylonitrile is 1-2:2-4; The mass ratio of polyvinylidene fluoride to polyacrylonitrile, pore-forming agent, filler and solvent is 10-20:5-15:3-7:

100.

4. A method for preparing a high-strength porous polymer electrolyte membrane according to claim 2 or 3, characterized in that: In the step 1), the mixing is ultrasonic mixing, the power of the ultrasonic mixing is 200-500W, the time of the ultrasonic mixing is 20-60min, and the temperature of the ultrasonic mixing is 20-40°C.

5. The method for preparing a high-strength porous polymer electrolyte membrane according to claim 4, characterized in that: In the step 2), the voltage of electrospinning is 15-20 kV, the speed of electrospinning is 0.5-1 mL / h, and the working distance of electrospinning is 12-20 cm.

6. The method for preparing a high-strength porous polymer electrolyte membrane according to claim 5, characterized in that: In the step 3), the pore-forming agent remover is ethanol and / or water; The soaking temperature is 40-60° C., and the soaking time is 30-120 min.

7. A method for preparing a high-strength porous polymer electrolyte membrane according to claim 3 or 5, characterized in that: In the step 3), activation is performed by immersing the electrolyte in an electrolyte for 1 to 4 hours; The electrolyte comprises a lithium-containing compound and a solvent, wherein the lithium-containing compound is lithium hexafluorophosphate or lithium bis(trifluoromethylsulfonyl)imide, and the solvent is one or more of polycarbonate, ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate; and the concentration of the electrolyte is 0.8-1.2 mol / L.

8. The method for preparing a high-strength porous polymer electrolyte membrane according to claim 7, characterized in that: In the step 3), the heat treatment temperature is 100-120° C., and the heat treatment time is 1-2 hours.

9. A porous polymer electrolyte membrane obtained by the method for preparing a high-strength porous polymer electrolyte membrane according to any one of claims 1 to 8.

10. Use of the porous polymer electrolyte membrane according to claim 9 in a battery.

Images