Diaphragm capable of improving high pressure resistance and dendritic crystal puncture resistance and preparation method thereof

Abstract

The invention discloses a diaphragm capable of improving high pressure resistance and dendritic crystal puncture resistance and a preparation method thereof, and belongs to the technical field of diaphragms.The diaphragm capable of improving high pressure resistance and dendritic crystal puncture resistance is arranged on the negative electrode side of the diaphragm, and PPy or PANI is modified on the surfaces of Al2O3-coated ZrO2 core-shell structure nanoparticles; and poly (N-isopropylacrylamide) (PNIPAM) is used as a temperature response type polymer and is modified on the positive electrode side of the diaphragm. The diaphragm capable of improving high voltage resistance and dendrite puncture resistance can effectively prevent penetration of lithium dendrites and improve deposition and dissolution behaviors of lithium ions of a negative electrode in the charging and discharging process of a lithium ion battery, the lithium ions are uniformly deposited on the surface of the negative electrode, local supersaturation is reduced, and thus formation of the lithium dendrites is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of diaphragm, in particular to a diaphragm with high pressure resistance and dendrite penetration resistance and a preparation method thereof. BACKGROUND

[0002] During the charging and discharging process of the battery, the concentration of lithium ions in the electrolyte may change, especially under high-rate charging or low-temperature conditions. At high temperatures, the viscosity of the electrolyte decreases, although the ion migration rate increases, but due to the rapid flow of the electrolyte and the non-uniformity of the local temperature, it may cause the exacerbation of local concentration polarization. Local concentration polarization refers to the uneven distribution of lithium ion concentration in the electrolyte in some areas, which will further exacerbate the uneven deposition of lithium ions on the negative electrode surface, forming lithium dendrites. The growth of lithium dendrites not only reduces the performance of the battery, but also may pierce the diaphragm and cause internal short circuit of the battery. Under low-temperature conditions, the viscosity of the electrolyte increases, and the diffusion rate of lithium ions decreases, resulting in uneven deposition of lithium ions on the negative electrode surface, and more easily forming lithium dendrites.

[0003] During the process of lithium ion insertion and extraction, the negative electrode material (such as graphite, silicon, etc.) is prone to form lithium dendrites. During the process of lithium ion insertion and extraction, uneven dissolution refers to the uneven dissolution process of lithium ions on the negative electrode surface, that is, the extraction speed of lithium ions in some areas is faster than that in other areas, resulting in local supersaturation, which may cause local lithium dendrites to remain, but the local supersaturation state may exacerbate the growth of lithium dendrites. The growth direction of lithium dendrites is usually towards the diaphragm, so the negative side of the diaphragm needs to be able to effectively prevent the penetration of lithium dendrites. SUMMARY

[0004] As described in the above prior art, one of the purposes of the present application is to provide a diaphragm with high pressure resistance and dendrite penetration resistance, which can effectively prevent the penetration of lithium dendrites, improve the deposition and dissolution behavior of negative lithium ions in the charging and discharging process of the lithium ion battery, and uniformly deposit lithium ions on the negative electrode surface, thereby reducing local supersaturation and reducing the formation of lithium dendrites.

[0005] The second purpose of the present application is to provide a method for manufacturing a diaphragm with high pressure resistance and dendrite penetration resistance, which can successfully manufacture a diaphragm with high pressure resistance and dendrite penetration resistance.

[0006] One of the purposes of the present application is achieved by using the following technical solutions: The diaphragm with high pressure resistance and dendrite penetration resistance is modified on the surface of the Al2O3@ZrO2 core-shell structure nanoparticles on the negative side of the diaphragm, and PPy or PANI is modified on the surface of the Al2O3@ZrO2 core-shell structure nanoparticles on the negative side of the diaphragm. Poly N-isopropyl acrylamide (PNIPAM) is used as a temperature-responsive polymer and is modified on the positive side of the diaphragm.

[0007] Further, the diaphragm is a nanofiber diaphragm.

[0008] The second object of the application is achieved by the following technical solution: The method for manufacturing a diaphragm with high pressure resistance and dendrite penetration resistance comprises the following steps: S1, preparing a nanofiber diaphragm by electrospinning technology: dissolving polymer PVDF-HFP or PAN in a DMF / acetone system with a mass ratio of 7:3, and the solid content is 12wt%; adding 5-10wt% of Al2O3 nanoparticles with a particle size of 50nm and surface modified by silane coupling agent, and ball milling at 2000rpm for 2h to obtain a uniform suspension; preparing an Al2O3 nanofiber membrane diaphragm with a fiber diameter of 200-300nm and a porosity of 75% by electrospinning technology according to the electrospinning parameters: voltage 18kV, winding distance 15cm, flow rate 1mL·h-1, and humidity <40%; S2, preparing an Al2O3@ZrO2 nanofiber diaphragm: first, using Al2O3 nanoparticles (50nm) as seeds, and (TEMAZ+H2O / O3) as a gas precursor, depositing 5nm of ZrO2 nanoparticles on the surface of the Al2O3 nanoparticles on the negative side of the Al2O3 nanofiber membrane diaphragm by atomic layer deposition (ALD) to form a ZrO2 shell layer, and obtaining an Al2O3@ZrO2 nanofiber diaphragm; S3, modifying the negative side of the Al2O3@ZrO2 nanofiber diaphragm with PPy or PANI: directly coating PPy or PANI on the ZrO2 shell layer of the Al2O3@ZrO2 nanofiber diaphragm by in-situ oxidative polymerization, and the specific method of in-situ chemical oxidative polymerization is as follows: immersing the Al2O3@ZrO2 nanofiber diaphragm in a pyrrole and aniline monomer solution, and initiating polymerization by adding ammonium persulfate or FeCl3, so that PPy or PANI is coated on the ZrO2 shell layer of the Al2O3@ZrO2 nanofiber diaphragm, and an Al2O3@ZrO2 nanofiber diaphragm uniformly coated with PPy or PANI is formed; S4, modifying the positive side of the Al2O3@ZrO2 nanofiber diaphragm with a block copolymer brush of poly(N-isopropyl acrylamide)-b-poly(ethylene glycol methacrylate), and grafting the block copolymer brush on the positive side surface of the Al2O3@ZrO2 nanofiber diaphragm by surface-initiated atom transfer radical polymerization (SI-ATRP), wherein the block molar ratio of poly(N-isopropyl acrylamide): poly(N-isopropyl acrylamide) is 7:3, the grafting thickness is 80-100nm, and the diaphragm with high pressure resistance and dendrite penetration resistance is obtained; "PNIPAM-b-PEGMA block copolymer brush" refers to a block copolymer brush of poly(N-isopropylacrylamide)-b-poly(ethylene glycol methacrylate), wherein: The poly(N-isopropylacrylamide) segment provides temperature response with a LCST of 32°C; The poly(ethylene glycol methacrylate) segment provides low temperature hydrophilicity and electrolyte wetting function; The brush indicates that the chain end is fixed on the positive side surface of the Al2O3@ZrO2 nanofiber separator by a covalent bond, in a dense layer structure with vertical orientation.

[0009] Further, in step S4, the surface-initiated atom transfer radical polymerization (SI-ATRP) comprises the following steps: S1, substrate pretreatment: placing the Al2O3@ZrO2 nanofiber separator (cut into 5 cm x 5 cm) in a 50W oxygen plasma for 60s to introduce surface hydroxyl groups, immediately immersing in a 1wt% 3-(trimethoxysilyl)propyl-2-bromo-2-methylpropionate (BIBS) anhydrous toluene solution, under nitrogen protection at a temperature of 80°C for 2h to obtain a Br-initiator modified Al2O3@ZrO2 nanofiber separator (Br-Sub); after taking out, rinsing with toluene and ethanol each for 2 times, vacuum drying at 60°C for 30min; S2, first SI-ATRP polymerization (poly(N-isopropylacrylamide) segment) Reaction solution A: N-isopropylacrylamide (NIPAM) 4.0g (35.4mmol), catalyst CuBr 57mg and CuBr 27mg, ligand Me6TREN 93µL, solvent is a total volume of 20mL of ethanol / water solution (v / v) in a volume ratio of 80:20; nitrogen degassing for 30min, immersing the Br-initiator modified Al2O3@ZrO2 nanofiber separator vertically in the reaction solution A, under a temperature of 25°C for 60min; after the reaction is completed, rinsing with ethanol / water, nitrogen blowing dry, obtaining a poly(N-isopropylacrylamide) brush layer with a thickness of about 55-65nm, i.e. the SI-ATRP first polymerization separator; S3, second SI-ATRP polymerization (poly(ethylene glycol methacrylate) segment) Reaction solution B: poly(ethylene glycol methacrylate) (Mn≈360) 1.7 g (4.7 mmol), catalyst CuBr 57 mg and CuBr 27 mg, ligand Me6TREN 93 µL, solvent is 20 mL of ethanol / water solution (v / v) with a volume ratio of 80:20; the first SI-ATRP polymerized membrane is transferred into reaction solution B, and the reaction is continued at a temperature of 25°C for 30 min; after being taken out, it is washed with ethanol / water and vacuum dried at a temperature of 60°C for 2 h to obtain the second SI-ATRP polymerized membrane with a total thickness of 80-100 nm and a block molar ratio of poly(N-isopropyl acrylamide): poly(N-isopropyl acrylamide) = 7:3 1 H-NMR integral confirmation), thereby obtaining the high-pressure-resistant and dendrite-penetration-resistant membrane.

[0010] Further, the specific steps for preparing the Al2O3@ZrO2 nanofiber membrane in step S2 are as follows: S1, the Al2O3 nanofiber membrane roll that has been laid is placed into an ALD cavity at 150-200°C, vacuum is extracted to <1 Torr, and 50 sccm N2 is blown for 5 min; S2, 50 deposition cycles are performed using TEMAZ (zirconium tetraethoxide, Zr(OCH2CH3)4) or Zr(NMe2)4 (tetramethylzirconium diamine) in combination with water (H2O); S3, the ALD cavity is cooled to below 60°C, the vacuum is broken, and the roll is taken out, and the whole process takes 30-60 min, thereby obtaining the Al2O3@ZrO2 nanofiber membrane.

[0011] Compared with the prior art, the present application has the following beneficial effects: (1) The high-pressure-resistant and dendrite-penetration-resistant membrane provided by the present application adopts atomic layer deposition (ALD) to deposit 5 nm of ZrO2 nanoparticles on the surface of Al2O3 nanoparticles on the negative side of the Al2O3 nanofiber membrane, thereby forming a continuous and dense protective layer on the pore surface of the membrane, ensuring that the pores of the nanofiber membrane are not blocked, meeting the demand for fast ion transmission of high-nickel positive electrodes and solid-state batteries , maintaining the ion transmission channel and maintaining the ion conductivity (≥1.5 mS / cm), as the high modulus of the ZrO2 coating (ZrO2~200 GPa) makes it difficult for dendrites to penetrate, and the elastic deformation ability of Al2O3 absorbs part of the mechanical stress, thereby improving the mechanical strength of the membrane and effectively blocking the penetration of lithium dendrites, thereby improving the safety of the battery The poly pyrrole (PPy) or polyaniline (PANI) modified nanoparticles can significantly affect the deposition and dissolution behavior of lithium ions during the charging and discharging process of lithium ion batteries through their surface charge characteristics. During the charging process, the surface of the PPy or PANI modified nanoparticles will be negatively charged because PPy and PANI will undergo electrochemical reactions under the action of an electric field, and the surface charge distribution will change. This negative charge can attract lithium ions through electrostatic attraction, causing them to uniformly deposit on the surface of the nanoparticles, thereby reducing the formation of lithium dendrites on the negative side of the separator.

[0012] During the discharging process, the surface charge of the PPy or PANI modified nanoparticles will change. Specifically, the surface charge of PPy or PANI will change from negative to neutral or positive, at which point lithium ions dissolve from the negative electrode surface into the electrolyte. This change in charge helps lithium ions uniformly dissolve from the surface of the nanoparticles into the electrolyte, reducing local supersaturation at the negative electrode. In a high-temperature environment, the viscosity of the electrolyte decreases, the ion transport efficiency is already high, and the surface tension also changes, which can cause the electrolyte to accumulate locally on the positive side of the separator. Due to the low surface energy of the hydrophobic surface, the electrolyte has enhanced mobility on the hydrophobic surface, and the electrolyte is more inclined to move away from the hydrophobic surface rather than accumulate on it. The enhanced mobility of the electrolyte on the hydrophobic surface makes the electrolyte more inclined to distribute in other parts of the separator, such as the inside of the pores. The distribution of the electrolyte throughout the separator becomes more uniform, reducing the local accumulation of electrolyte on the positive side of the separator. Uniform distribution of the electrolyte throughout the separator helps lithium ions uniformly deposit on the negative electrode surface, reducing local supersaturation and thus reducing the formation of lithium dendrites.

[0013] Poly N-isopropyl acrylamide (PNIPAM) is used as a temperature-responsive polymer. When the temperature rises during battery operation, it undergoes a phase change above 32°C, changing from hydrophilic to hydrophobic. The surface of the separator on the positive side modified with poly N-isopropyl acrylamide changes from hydrophilic to hydrophobic, reducing the retention of electrolyte on the positive side of the separator and improving the safety of the battery.

[0014] In a low-temperature environment, the viscosity of the electrolyte is high and the ion transport efficiency is low. At this time, the wettability of the electrolyte on the surface of the separator becomes particularly important. Below 32°C, the poly N-isopropyl acrylamide segment remains well hydrophilic, ensuring uniform distribution of the electrolyte on the surface of the separator. This can enhance the wettability of the electrolyte on the surface of the separator, reduce local accumulation of the electrolyte, and allow the electrolyte to be more uniformly distributed on the surface of the separator. This can reduce the resistance of lithium ions during transport, thereby improving ion transport efficiency and ensuring the wettability and ion transport efficiency of the electrolyte. DETAILED DESCRIPTION

[0015] Hereinafter, the present application will be further described in conjunction with specific embodiments. It should be noted that the following described embodiments or technical features can be combined in any manner to form new embodiments without conflict.

[0016] Embodiment 1 The embodiment provides a high-pressure-resistant and dendrite-penetration-resistant separator with lotus flower, wherein PPy or PANI is modified on the surface of Al2O3@ZrO2 core-shell structure nanoparticles on the negative side of the separator; and poly-N-isopropyl acrylamide (PNIPAM) is modified on the positive side of the separator as a temperature-responsive polymer.

[0017] The embodiment also provides a method for manufacturing the high-pressure-resistant and dendrite-penetration-resistant separator, comprising the following steps. S1, preparing a nanofiber separator by electrospinning: dissolving a polymer PVDF-HFP or PAN in a DMF / acetone system with a mass ratio of 7:3, and the solid content is 12wt%; adding 50nm, 5-10wt% of Al2O3 nanoparticles modified by a silane coupling agent to the system, and ball milling at 2000rpm for 2h to obtain a uniform suspension; and preparing an Al2O3 nanofiber membrane separator with a fiber diameter of 200-300nm and a porosity of 75% by electrospinning according to the electrospinning parameters: a voltage of 18kV, a winding distance of 15cm, a flow rate of 1mL·h-1, and a humidity of <40%; S2, preparing an Al2O3@ZrO2 nanofiber separator: using Al2O3 nanoparticles (50nm) as seeds, using (TEMAZ+H2O / O3) as a gas-phase precursor, and using atomic layer deposition (ALD) to deposit 5nm of ZrO2 nanoparticles on the surface of the Al2O3 nanoparticles on the negative side of the Al2O3 nanofiber membrane separator to form a ZrO2 shell layer, thereby obtaining the Al2O3@ZrO2 nanofiber separator; S3, modifying PPy or PANI on the negative side of the Al2O3@ZrO2 nanofiber separator: directly coating PPy or PANI on the ZrO2 shell layer of the Al2O3@ZrO2 nanofiber separator by in-situ oxidative polymerization, and the specific method of in-situ chemical oxidative polymerization is as follows: immersing the Al2O3@ZrO2 nanofiber separator in a pyrrole and aniline monomer solution, and adding ammonium persulfate or FeCl3 to initiate polymerization, so that PPy or PANI is coated on the ZrO2 shell layer of the Al2O3@ZrO2 nanofiber separator to form the Al2O3@ZrO2 nanofiber separator coated with uniform PPy or PANI; S4, a positive electrode side of the Al2O3@ZrO2 nanofiber separator is modified with a block copolymer brush of poly(N-isopropylacrylamide)-b-poly(ethylene glycol methacrylate) grafted on the positive electrode side surface of the Al2O3@ZrO2 nanofiber separator by surface-initiated atom transfer radical polymerization (SI-ATRP), wherein: the block molar ratio of poly(N-isopropylacrylamide): poly(N-isopropylacrylamide) is 7:3, the grafted thickness is 80-100 nm, and a separator with improved high-pressure resistance and dendrite penetration resistance is obtained; “PNIPAM-b-PEGMA block copolymer brush” refers to a block copolymer brush of poly(N-isopropylacrylamide)-b-poly(ethylene glycol methacrylate), wherein: The poly(N-isopropylacrylamide) segment provides temperature response, and the LCST is 32°C; The poly(ethylene glycol methacrylate) segment provides low-temperature hydrophilicity and electrolyte wetting function; The brush indicates that the chain end is fixed on the positive electrode side surface of the Al2O3@ZrO2 nanofiber separator by a covalent bond, and is in a dense lamellar structure with vertical orientation.

[0018] In this embodiment, in step S4, the surface-initiated atom transfer radical polymerization (SI-ATRP) includes the following steps: S1, substrate pretreatment: the Al2O3@ZrO2 nanofiber separator (cut into 5 cm x 5 cm) is placed in a 50W oxygen plasma for 60s to introduce surface hydroxyl groups, and then immediately immersed in a 1wt% 3-(trimethoxysilyl)propyl-2-bromo-2-methylpropionate (BIBS) anhydrous toluene solution, and protected by nitrogen at a temperature of 80°C for 2h to obtain a Br-initiator modified Al2O3@ZrO2 nanofiber separator (Br-Sub); after taking out, rinse with toluene and ethanol each for 2 times, and vacuum dry at 60°C for 30min; S2, first SI-ATRP polymerization (poly(N-isopropylacrylamide) segment) Reaction solution A: N-isopropylacrylamide (NIPAM) 4.0g (35.4mmol), catalyst CuBr 57mg and CuBr 27mg, ligand Me6TREN 93µL, solvent is a total volume of 20mL of an ethanol / water solution (v / v) in a volume ratio of 80:20; nitrogen degassing for 30min, the Br-initiator modified Al2O3@ZrO2 nanofiber separator is vertically immersed in the reaction solution A, and the reaction is carried out at a temperature of 25°C for 60min; after the reaction is completed, rinse with ethanol / water, and dry with nitrogen, to obtain a poly(N-isopropylacrylamide) brush layer with a thickness of about 55-65nm, i.e. a SI-ATRP first polymerization separator; S3, SI-ATRP second polymerization (poly(ethylene glycol methacrylate) segment) Reaction solution B: poly(ethylene glycol methacrylate) (Mn≈360) 1.7 g (4.7 mmol), catalyst CuBr 57 mg and CuBr 27 mg, ligand Me6TREN 93 μL, solvent is 20 mL of ethanol / water solution (v / v) in a volume ratio of 80:20; the membrane of SI-ATRP first polymerization is transferred into reaction solution B, and the reaction is continued at a temperature of 25 °C for 30 min; after being taken out, it is washed with ethanol / water and vacuum dried at a temperature of 60 °C for 2 h to obtain a SI-ATRP second polymerization membrane with a total thickness of 80-100 nm and a block molar ratio of poly(N-isopropyl acrylamide): poly(N-isopropyl acrylamide) = 7:3 1 H-NMR integral confirmation), a membrane with improved high-pressure resistance and dendrite penetration resistance is obtained.

[0019] In this embodiment, the specific steps of preparing the Al2O3@ZrO2 nanofiber membrane in step S2 are as follows: S1, the already laid Al2O3 nanofiber membrane roll is placed into an ALD cavity at 150-200 °C, vacuum is extracted to <1 Torr, and 50 sccm N2 is blown for 5 min; S2, 50 deposition cycles are performed using TEMAZ (zirconium tetraethoxide, Zr(OCH2CH3)4) or Zr(NMe2)4 (tetramethylzirconium diamine) in combination with water (H2O); S3, cooling and taking out the material, the ALD cavity is lowered to below 60 °C, the vacuum is broken, and the roll is taken out, the whole process takes 30-60 min, and an Al2O3@ZrO2 nanofiber membrane is obtained.

[0020] In this embodiment, the nanofiber membrane (such as PVDF-HFP or PI fiber membrane prepared by electrospinning) generally has a porosity of 80-90% and a pore size of 0.5-2 μm, which provides a smooth transmission channel for Li + ions. Compared with commercial PP / PE membranes (porosity 40-50%), the nanofiber membrane can still retain >70% porosity after coating, meeting the ion conductivity requirement (>1.5 mS / cm requires porosity >60%).

[0021] CuBr: 57 mg (0.40 mmol) CuBr2: 7 mg (0.030 mmol) Function: Cu + is the active center of ATRP; Cu 2+ acts as a deactivator to maintain the controllable / active polymerization rate, reduce the free radical concentration, and prevent bulk polymerization.

[0022] 2 ligand Me6TREN: 93 µL (0.40 mmol) Function: Tridentate nitrogen ligand, stabilizes Cu + / Cu 2+ Forms soluble complex, improves catalyst activity and stabilizes Cu ions, avoids precipitation.

[0023] 3 Solvent Ethanol / water = 80:20 (v / v), total volume 20 mL Function: Balances monomer solubility and Cu complex stability, while maintaining polymerization temperature at 25 °C.

[0024] In-situ chemical oxidative polymerization: ZrO2 nanoparticles are ultrasonically dispersed in the pyrrole / aniline monomer solution, and polymerization is initiated by APS (ammonium persulfate) or FeCl3, forming uniform PPy / PANI coating.

[0025] On the surface of the membrane that has grown PNIPAM brushes, PEGMA monomers are allowed to "graft" onto the surface under Cu + catalysis, forming PNIPAM-b-PEGMA block copolymer brushes, with an additional thickness of 25-35 nm, for a total thickness of 80-100 nm.

[0026] Membrane pretreatment: The membrane (Br-Sub) has been treated by oxygen plasma and Br-initiators have been introduced, which will work synergistically with the Cu catalyst system to initiate polymerization.

[0027] Immersion in reaction solution: The membrane is vertically immersed in reaction solution A, ensuring uniform contact of the membrane surface with the reaction solution. Polymerization: Polymerization of NIPAM monomers under the action of Br-initiators and Cu catalysts occurs at 25 °C for 60 minutes, forming a PNIPAM brush layer.

[0028] Post-treatment: After the reaction is complete, the membrane is rinsed with ethanol / water to remove unreacted monomers and catalysts; then dried with nitrogen to obtain a membrane with a PNIPAM brush layer on the surface.

[0029] The above embodiments are only preferred embodiments of the present application, and cannot be used to limit the scope of protection of the present application. Any non-essential changes and substitutions made by those skilled in the art based on the present application are within the scope of the present application.

Claims

1. A diaphragm having improved high pressure resistance and dendrite penetration resistance, characterized in that, On the negative side of the diaphragm, PPy or PANI is modified on the surface of Al2O3@ZrO2 core-shell structure nanoparticles; poly N-isopropyl acrylamide is modified on the positive side of the diaphragm as a temperature-responsive polymer.

2. The separator of claim 1, wherein the separator has improved high pressure resistance and improved dendrite penetration resistance. The diaphragm is a nanofiber diaphragm.

3. A method for producing a diaphragm having improved high pressure resistance and dendrite penetration resistance, characterized by, The method comprises the following steps: S1, preparing nanofiber membrane by electrospinning technology: dissolving polymer PVDF-HFP or PAN in DMF / acetone system with mass ratio of 7:3, solid content of 12wt%; adding 5-10wt% of Al2O3 nanoparticles with particle size of 50nm and surface modified by silane coupling agent, ball milling at 2000rpm for 2h to obtain uniform suspension; preparing Al2O3 nanofiber membrane with fiber diameter of 200-300nm and porosity of 75% by electrospinning technology according to electrospinning parameters: voltage of 18kV, winding distance of 15cm, flow rate of 1mL·h -1 ​ S2, preparation of Al2O3@ZrO2 nanofiber diaphragm: first, Al2O3 nanoparticles are used as seeds, and tetraethoxy zirconium or tetramethyl diamine zirconium is used as a gas phase precursor to deposit 5 nm ZrO2 nanoparticles on the surface of Al2O3 nanoparticles on the negative side of the Al2O3 nanofiber diaphragm by atomic layer deposition, to form a ZrO2 shell layer, thereby obtaining the Al2O3@ZrO2 nanofiber diaphragm; S3, modification of polypropylene or polyaniline on the negative side of the Al2O3@ZrO2 nanofiber diaphragm: polypropylene or polyaniline is directly coated on the ZrO2 shell layer of the Al2O3@ZrO2 nanofiber diaphragm by in-situ oxidative polymerization, and the specific method of the in-situ chemical oxidative polymerization is as follows: the Al2O3@ZrO2 nanofiber diaphragm is immersed in a pyrrole and aniline monomer solution, ammonium persulfate or FeCl3 is added to initiate polymerization, polypropylene or polyaniline is coated on the ZrO2 shell layer of the Al2O3@ZrO2 nanofiber diaphragm, and a polypropylene or polyaniline uniformly coated Al2O3@ZrO2 nanofiber diaphragm is formed; S4, modification of a block copolymer brush of poly(N-isopropyl acrylamide)-b-poly(ethylene glycol methacrylate) on the positive side of the Al2O3@ZrO2 nanofiber diaphragm, which is grafted on the positive side surface of the Al2O3@ZrO2 nanofiber diaphragm by surface-initiated atom transfer radical polymerization, wherein: the block molar ratio of poly(N-isopropyl acrylamide) and poly(N-isopropyl acrylamide) is 7:3, the grafting thickness is 80-100 nm, and the diaphragm with improved high-pressure resistance and dendrite puncture resistance is obtained; Wherein: The poly(N-isopropyl acrylamide) segment provides temperature response, and the LCST thereof is 32°C; The poly(ethylene glycol methacrylate) segment provides low-temperature hydrophilicity and electrolyte wetting function; The brush indicates that the chain end is fixed on the positive side surface of the Al2O3@ZrO2 nanofiber diaphragm by a covalent bond, and is in a vertical orientation dense lamellar structure.

4. The method for preparing a diaphragm with improved high-pressure resistance and dendrite puncture resistance as described in claim 3, characterized in that, In step S4, the surface-initiated atom transfer radical polymerization comprises the following steps: S1, substrate pretreatment: the Al2O3@ZrO2 nanofiber diaphragm, which has been cut into 5 cm x 5 cm, is placed in a 50W oxygen plasma for 60s to introduce surface hydroxyl groups, and then immediately immersed in a 1wt% 3-(trimethoxysilyl)propyl-2-bromo-2-methylpropionate anhydrous toluene solution, and is protected by nitrogen at a temperature of 80°C for 2h to obtain a Br-initiator modified Al2O3@ZrO2 nanofiber diaphragm; after being taken out, it is rinsed with toluene and ethanol for 2 times respectively, and is vacuum dried at 60°C for 30min; S2, first polymerization of surface-initiated atom transfer radical polymerization Synthesis of poly(N-isopropylacrylamide) segment: Reaction solution A: N-isopropylacrylamide 4.0 g, catalyst CuBr 57 mg and CuBr 27 mg, ligand Me6TREN 93 μL, solvent is 20 mL of ethanol / water solution (v / v) with a volume ratio of 80:20; the Br-initiated modified Al2O3@ZrO2 nanofiber membrane is vertically immersed in the reaction solution A, and the reaction is carried out at a temperature of 25°C for 60 min; after the reaction is completed, it is washed with ethanol / water, dried with nitrogen, and a poly(N-isopropylacrylamide) brush layer with a thickness of about 55-65 nm is obtained, that is, the membrane after the first polymerization of surface-initiated atom transfer radical polymerization; S3, second polymerization of surface-initiated atom transfer radical polymerization Synthesis of poly(ethylene glycol methacrylate) segment: Reaction solution B: poly(ethylene glycol methacrylate) 1.7 g (4.7 mmol), catalyst CuBr 57 mg and CuBr 27 mg, ligand Me6TREN 93 μL, solvent is 20 mL of ethanol / water solution (v / v) with a volume ratio of 80:20; the membrane after the first polymerization of SI-ATRP is transferred into the reaction solution B, and the reaction is continued at a temperature of 25°C for 30 min; after being taken out, it is washed with ethanol / water, and vacuum dried at a temperature of 60°C for 2 h, to obtain the membrane after the second polymerization of surface-initiated atom transfer radical polymerization with a total thickness of 80-100 nm and a block molar ratio of poly(N-isopropylacrylamide): poly(N-isopropylacrylamide) = 7:3, to obtain the membrane with improved high-pressure resistance and dendrite puncture resistance.

5. The method for preparing a diaphragm with improved high-pressure resistance and dendrite puncture resistance as described in claim 3, characterized in that, The specific steps for preparing the Al2O3@ZrO2 nanofiber membrane in step S2 are as follows: S1, roll the Al2O3 nanofiber membrane prepared in step S0 into an ALD cavity at 150-200°C, vacuumize to <1 Torr, and blow with 50 sccm of N2 for 5 min; S2, 50 deposition cycles of tetraethoxysilane or tetramethylsilane and water (H2O) are carried out; S3, cool and take out the material, the ALD cavity is reduced to below 60°C, the vacuum is broken, and the roll is taken out, and the whole process takes 30-60 min, to obtain the Al2O3@ZrO2 nanofiber membrane.