PE-pbi composite battery separator and preparation method and application thereof

Abstract

The application relates to the technical field of battery separators, and discloses a PE-PBI composite battery separator as well as a preparation method and application thereof. The PE-PBI composite battery separator comprises the following raw materials in parts by weight: 58-70 parts of a separator base material, 5-10 parts of an ionic liquid, 5-10 parts of a carbonate, and 3-6 parts of lithium bis-trifluoromethanesulfonimide; the separator base material comprises polyethylene and polybenzimidazole; the ionic liquid comprises 1-butyl-3-methylimidazolium hexafluorophosphate and N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide; and the carbonate comprises ethylene carbonate and / or vinylene carbonate. The application effectively improves the ionic conductivity of the separator through the synergistic cooperation between the two specific ionic liquids, ethylene carbonate and LiTFSI, and the two ionic liquids [BMIM][PF6] and [P 13 ][TFSI].

Description

Technical Field

[0001] This invention relates to the field of battery separator technology, and in particular to a PE-PBI composite battery separator, its preparation method, and its application. Background Technology

[0002] As a crucial component between the positive and negative electrodes inside a battery, the performance of the battery separator directly affects the battery's safety, cycle life, and charge / discharge efficiency. Traditional polyolefin battery separators, such as polyethylene (PE) separators, while possessing good chemical stability and mechanical strength, suffer from poor thermal stability (easily shrinking and deforming at high temperatures, increasing the risk of short circuits) and insufficient electrolyte wettability (affecting ion transport efficiency). Polybenzimidazole (PBI) materials exhibit excellent thermal stability, chemical stability, and mechanical properties; however, their application as a standalone battery separator presents challenges such as high cost and complex film-forming processes.

[0003] To overcome the limitations of polybutadiene-grafted polystyrene (PBI), existing technologies often combine it with polyolefins for use in battery separators. For example, in patent CN115621664A, polybutadiene-grafted polystyrene is used as the surface layer material, high-density polyethylene and inorganic whiskers as the intermediate layer material, and homopolymer polypropylene and polybenzimidazole as the inner layer material, forming a lithium-ion battery separator through a three-layer co-extrusion process. However, the introduction of polyolefins can also cause a decrease in the ionic conductivity of the separator. Summary of the Invention

[0004] To address the technical problem of poor ionic conductivity in composite membranes of polyolefins and polybenzimidazoles, this invention provides a PE-PBI composite battery membrane, its preparation method, and its application. In this invention, 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) and N-methyl-N-propylpyrrolidine bis(trifluoromethanesulfonyl)imide ([P...)...) are introduced into the PE-PBI composite battery membrane. 13 The components [TFSI], ethylene carbonate, and lithium bis(trifluoromethanesulfonylimide) (LiTFSI) work together to give the membrane high ionic conductivity.

[0005] The specific technical solution of this invention is as follows:

[0006] In a first aspect, the present invention provides a PE-PBI composite battery separator, comprising the following raw materials in parts by weight: 58-70 parts of separator substrate, 5-10 parts of ionic liquid, 5-10 parts of carbonate, and 3-6 parts of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI); wherein the separator substrate comprises polyethylene (PE) and polybenzimidazole (PBI); and the ionic liquid comprises 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) and N-methyl-N-propylpyrrolidine bis(trifluoromethanesulfonyl)imide ([P... 13 [TFSI]); the carbonate includes ethylene carbonate and / or vinylene carbonate.

[0007] This invention utilizes [BMIM][PF6] and [P] in a PE-PBI composite battery separator. 13 [TFSI] These two ionic liquids, along with specific carbonates (ethylene carbonate and / or vinylene carbonate) and LiTFSI, can leverage the synergistic effect between these raw materials to improve the ionic conductivity of the membrane, specifically:

[0008] (1) [BMIM][PF6], [P 13 [TFSI] and ethylene carbonate (or vinylene carbonate) interact with LiTFSI, improving the dispersion uniformity of LiTFSI in the composite material. During the drying process after film formation, ethylene carbonate (or vinylene carbonate) has a suitable evaporation rate. Mixing with the ionic liquid adjusts the system viscosity, forming a liquid-liquid two-phase region during film formation, providing thermodynamic conditions for macropore formation. As the solvent slowly evaporates, the porous system undergoes controlled phase separation from the PE-PBI substrate. The droplets formed by the porous components gradually aggregate and grow, eventually leaving large-sized pores in the substrate after evaporation. Furthermore, the compounding with the ionic liquid optimizes interfacial tension, enhances the connectivity between pores, and prevents the formation of closed or isolated pores, significantly increasing porosity to over 60%, achieving a high-porosity, large-pore-size, and highly interconnected pore structure. LiTFSI adheres to the pore surface and the interior of the material, generating freely moving ions. Its unique chemical structure helps reduce the resistance to ion migration. In the channels formed by pores, ions can conduct efficiently, thereby improving the ionic conductivity of the membrane.

[0009] (2) This invention uses [BMIM][PF6] and [P] 13 [TFSI] These two ionic liquids are combined, in which the imidazole ring and pyrrolidine ring form multi-component coordination with the carbonyl group in ethylene carbonate (or vinylene carbonate), and TFSI - PF6 - Anions and Li +The formation of dynamically balanced ion clusters helps prevent ion aggregation, thereby improving the ionic conductivity of the membrane. Furthermore, the lower viscosity of [BMIM][PF6] contributes to increased ion migration rate, [P... 13 [TFSI] exhibits good compatibility with LiTFSI, which can reduce the thickness of the lithium-ion solvation layer. Based on this, [BMIM][PF6] and [P]... 13 [TFSI] work together to achieve higher ionic conductivity.

[0010] Preferably, the mass ratio of 1-butyl-3-methylimidazolium hexafluorophosphate to N-methyl-N-propylpyrrolidine bis(trifluoromethanesulfonyl)imide salt is 1:1 to 1.5.

[0011] Under the above ratio, [BMIM][PF6] and [P] 13 [TFSI] can form a better combination with carbonates and LiTFSI, further improving the ionic conductivity of the membrane.

[0012] Preferably, the carbonate includes ethylene carbonate.

[0013] Compared to other carbonate compounds, ethylene carbonate has moderate ring strain and a high dielectric constant, enabling it to dissolve LiTFSI more efficiently and promote its dissociation, thereby increasing the concentration of free lithium ions. Furthermore, ethylene carbonate has moderate molecular polarity, which is compatible with the TFSI in LiTFSI. - Anions, as well as [BMIM][PF6], [P] 13 [TFSI] can form a multi-component composite network, reduce ion aggregation, and lower lithium ion migration resistance. Therefore, when ethylene carbonate is used, the ionic conductivity of the membrane can be improved to a greater extent.

[0014] Preferably, the mass ratio of polyethylene to polybenzimidazole is 32~38:26~32.

[0015] Preferably, the PE-PBI composite battery separator further includes the following raw materials in parts by weight: 5-7 parts of nano-SiO2 and / or 5-8 parts of graphene oxide; the nano-SiO2 is pre-grafted with polyethylene glycol before use; and the graphene oxide is pre-modified with polydopamine before use.

[0016] PBI, nano-silica, and graphene oxide can synergistically improve the mechanical properties of the separator, helping to resist mechanical stress inside the battery, prevent short circuits caused by separator rupture, and improve battery safety. At the same time, they can also improve the thermal stability of the separator, helping to avoid battery safety hazards caused by separator shrinkage and deformation under high temperature conditions.

[0017] After polyethylene glycol grafting and modifying silica, the ether bonds (COC) and terminal hydroxyl groups in the PEG molecular chain can complex with electrolyte components through dipole interaction and hydrogen bonding, which greatly improves the affinity of the membrane for the electrolyte, allowing the electrolyte to quickly wet and be evenly distributed in the membrane pores.

[0018] Adding polydopamine to graphene oxide can serve as a flexible spacer. PDA molecular chains can be inserted between GO sheets, fixing the sheet spacing at 20~30nm. This solves the problem of decreased porosity caused by conventional GO sheet stacking, avoids pore blockage caused by sheet shrinkage during drying or hot pressing, improves its wettability to electrolyte and ion transport capacity, and enhances the flexibility of the membrane.

[0019] Preferably, the polyethylene glycol is grafted onto nano-SiO2 using an epoxy silane coupling agent; the weight-average molecular weight of the polyethylene glycol is 2000~2500 Da.

[0020] Preferably, the PE-PBI composite battery separator further includes the following raw materials in parts by weight: 5-8 parts of hollow mesoporous SiO2 and / or 8-12 parts of polyvinylidene fluoride-hexafluoropropylene copolymer; the hollow mesoporous SiO2 has an average particle size of 250-300 nm and an average pore size of 20-30 nm.

[0021] Hollow mesoporous SiO2 has a high specific surface area and a unique pore structure, which enables it to effectively adsorb electrolyte. PVDF-HFP helps improve the film-forming performance of the PE-PBI composite battery separator and its chemical stability in the electrolyte, making the separator less prone to chemical degradation during long-term use, thereby extending the battery's cycle life.

[0022] Preferably, the PE-PBI composite battery separator is modified with a coupling agent; the coupling agent includes γ-aminopropyltriethoxysilane and / or N-β-aminoethyl-γ-aminopropyltrimethoxysilane.

[0023] By using the above-mentioned coupling agent to modify the surface of the membrane, the electrolyte wettability of the membrane can be further improved, enabling it to quickly absorb the electrolyte and form a stable ion transport interface.

[0024] Secondly, the present invention provides a method for preparing the PE-PBI composite battery separator, comprising mixing all raw materials with an organic solvent, coating the mixture, and then drying it through the following process: maintaining the temperature at 40~50℃ and a vacuum of -0.08~-0.09MPa for 4~6h → maintaining the temperature at 60~65℃ and a vacuum of -0.08~-0.09MPa for 2~3h → maintaining the temperature at 75~80℃ and a vacuum of -0.09~-0.095MPa for 2~3h.

[0025] When the membrane raw material contains polyethylene glycol-grafted modified nano-SiO2 and polydopamine-modified graphene oxide, the following effects can be achieved by combining it with the above-mentioned stepwise drying process: Under heat treatment at 40~50℃ and vacuum conditions, the organic solvent slowly evaporates, forming a preliminary porous framework, preventing the surface layer from rapidly solidifying and forming a sealing layer that would prevent the internal solvent from escaping; at 60~65℃, hydrogen bonds can be formed between the imidazole groups in the PBI molecular chain and the terminal hydroxyl groups of PEG, strengthening the interfacial bonding, while allowing the ionic liquid to form preliminary ion channels in the PE-PBI matrix; the heat treatment process at 75~80℃ can strengthen the interfacial bonding between graphene oxide and nano-SiO2. By employing the aforementioned gradient heating heat treatment method and the specific temperature design for each stage, the effects of ionic liquid, graphene oxide, and polyethylene glycol-grafted modified nano-SiO2 can be enhanced. This process also creates a three-dimensional interconnected pore network in the separator that is more conducive to ion transport. The stable and regular pore structure helps improve the ionic conductivity of the separator. At the same time, the favorable pore structure also helps improve the mechanical properties of the separator, enabling it to better perform its function of isolating the positive and negative electrodes and ensuring ion transport in the battery. This effectively improves the battery's safety, cycle life, and charge / discharge performance.

[0026] Preferably, the preparation method includes the following steps: mixing all raw materials with an organic solvent, coating the mixture onto a substrate, and then processing it according to the drying procedure.

[0027] Preferably, the organic solvent includes N-methylpyrrolidone (NMP).

[0028] Preferably, in the drying process, the heating rate at each stage is 4~6℃ / h. Preferably, after the drying process is completed, the material is hot-pressed at 120~150℃ and 5~10MPa for 5~10min.

[0029] Preferably, after completing the drying process, the sample is soaked in a 2-5 wt% coupling agent solution for 1-2 hours, washed with water, and dried; the coupling agent includes γ-aminopropyltriethoxysilane (KH550) and / or N-β-aminoethyl-γ-aminopropyltrimethoxysilane (KH792).

[0030] Preferably, the step of pre-grafting polyethylene glycol onto nano-SiO2 before use includes: mixing nano-SiO2 with a 3-5 wt% silane coupling agent solution at 50-60°C for 1-2 hours, separating the product, and then mixing it with a 1-2 wt% polyethylene glycol solution at 75-85°C for 2-3 hours.

[0031] Preferably, the step of pre-modifying graphene oxide with polydopamine before use includes: adding dropwise a 1-2 mg / mL dopamine hydrochloride solution with pH=8.0-8.5 to a 0.5-1 mg / mL graphene oxide dispersion, ultrasonically stirring for 1-2 h after the addition is completed, and then stirring and maturing at 25-35℃ for 4-6 h; the mass ratio of graphene oxide to dopamine hydrochloride is 1:1-4.

[0032] Thirdly, the present invention provides the application of a battery separator in a lithium-ion battery, wherein the battery separator is the above-mentioned PE-PBI composite battery separator, or is a PE-PBI composite battery separator prepared by the above-mentioned preparation method.

[0033] Compared with the prior art, the present invention has the following advantages:

[0034] (1) This invention introduces two specific ionic liquids ([BMIM][PF6] and [P]) into the PE-PBI composite battery separator. 13 [TFSI]), specific carbonates (ethylene carbonate and / or vinylene carbonate) and LiTFSI, can utilize the interaction between these two ionic liquids, carbonates and LiTFSI, and the interaction between the two ionic liquids [BMIM][PF6] and [P 13 The synergistic effect between [TFSI] improves the ionic conductivity of the membrane.

[0035] (2) In the PE-PBI composite battery separator of the present invention, by introducing PEG grafted modified nano SiO2 as raw material, the ether bond (COC) and terminal hydroxyl group in the PEG molecular chain can be used to complex with the electrolyte components through dipole action and hydrogen bond, which greatly improves the affinity of the separator to the electrolyte, so that the electrolyte can quickly wet and be evenly distributed in the pores of the separator.

[0036] (3) In the PE-PBI composite battery separator of the present invention, by introducing PDA-modified graphene oxide, the mechanical properties and thermal stability of the separator can be improved by utilizing graphene oxide, and the ionic conductivity of the separator can be improved by utilizing the supporting effect of PDA between graphene oxide sheets.

[0037] (4) The PE-PBI composite battery separator of the present invention can better balance ionic conductivity, mechanical strength and thermal stability, so that when it is applied to lithium-ion batteries, it can give the battery better overall performance. Detailed Implementation

[0038] The present invention will be further described below with reference to embodiments.

[0039] First, the present invention relates to a PE-PBI composite battery separator, comprising the following raw materials in parts by weight: 58-70 parts of separator substrate, 5-10 parts of ionic liquid, 5-10 parts of carbonate, and 3-6 parts of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI); wherein the separator substrate comprises polyethylene (PE) and polybenzimidazole (PBI); and the ionic liquid comprises 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) and N-methyl-N-propylpyrrolidine bis(trifluoromethanesulfonyl)imide ([P... 13 [TFSI]); the carbonate includes ethylene carbonate and / or vinylene carbonate.

[0040] In some specific embodiments, the carbonate includes ethylene carbonate.

[0041] In some specific embodiments, the mass ratio of polyethylene to polybenzimidazole is 32~38:26~32.

[0042] In some specific embodiments, the mass ratio of 1-butyl-3-methylimidazolium hexafluorophosphate to N-methyl-N-propylpyrrolidine bis(trifluoromethanesulfonyl)imide salt is 1:1 to 1.5.

[0043] In some specific embodiments, the polyethylene is pre-ground into micro powder with an average particle size of 100~150μm before use, and the polybenzimidazole is pre-ground into powder with an average particle size of 0.5~1.5mm before use.

[0044] In some specific embodiments, the PE-PBI composite battery separator further includes the following raw materials in parts by weight: 5-7 parts of nano-SiO2; the nano-SiO2 is pre-grafted with polyethylene glycol before use; the polyethylene glycol is grafted onto the nano-SiO2 using an epoxy silane coupling agent; and the weight-average molecular weight of the polyethylene glycol is 2000-2500 Da.

[0045] In some specific embodiments, the PE-PBI composite battery separator further includes the following raw materials in parts by weight: 5-8 parts of graphene oxide; the graphene oxide is pre-modified with polydopamine before use.

[0046] In some specific embodiments, the PE-PBI composite battery separator further includes the following raw materials in parts by weight: 5-8 parts of hollow mesoporous SiO2; the average particle size of the hollow mesoporous SiO2 is 250-300 nm, and the average pore size is 20-30 nm.

[0047] In some specific embodiments, the PE-PBI composite battery separator further includes the following raw materials in parts by weight: 8-12 parts of polyvinylidene fluoride-hexafluoropropylene copolymer.

[0048] In some specific embodiments, the PE-PBI composite battery separator is modified with a coupling agent; the coupling agent includes γ-aminopropyltriethoxysilane and / or N-β-aminoethyl-γ-aminopropyltrimethoxysilane.

[0049] Second, the present invention relates to a method for preparing the PE-PBI composite battery separator, comprising mixing all raw materials with an organic solvent, coating the mixture, and then drying it through the following process: maintaining at 40~50℃ and vacuum degree -0.08~-0.09MPa for 4~6h → maintaining at 60~65℃ and vacuum degree -0.08~-0.09MPa for 2~3h → maintaining at 75~80℃ and vacuum degree -0.09~-0.095MPa for 2~3h.

[0050] In some specific embodiments, the preparation method includes the following steps: mixing all raw materials with an organic solvent, coating the mixture onto a substrate, and then processing it according to the drying procedure.

[0051] In some specific embodiments, the organic solvent includes N-methylpyrrolidone (NMP).

[0052] In some specific embodiments, the heating rate at each stage of the drying process is 4~6℃ / h.

[0053] Preferably, after the drying process is completed, the material is hot-pressed at 120~150℃ and 5~10MPa for 5~10min.

[0054] In some specific embodiments, after the drying process is completed, the sample is soaked in a 2-5 wt% coupling agent solution for 1-2 hours, washed with water, and dried; the coupling agent includes γ-aminopropyltriethoxysilane and / or N-β-aminoethyl-γ-aminopropyltrimethoxysilane.

[0055] In some specific embodiments, the step of pre-grafting polyethylene glycol onto nano-SiO2 before use includes: mixing nano-SiO2 with a 3-5 wt% silane coupling agent solution at 50-60°C for 1-2 hours, separating the product, and then mixing it with a 1-2 wt% polyethylene glycol solution at 75-85°C for 2-3 hours.

[0056] In some specific embodiments, the step of pre-modifying graphene oxide with polydopamine before use includes: adding dropwise a 1-2 mg / mL dopamine hydrochloride solution with pH=8.0-8.5 to a 0.5-1 mg / mL graphene oxide dispersion, ultrasonically stirring for 1-2 h after the addition is completed, and then stirring and aging at 25-35℃ for 4-6 h; the mass ratio of graphene oxide to dopamine hydrochloride is 1:1-4.

[0057] Third, the present invention relates to the application of battery separators in lithium-ion batteries, wherein the battery separator is the above-mentioned PE-PBI composite battery separator, or is a PE-PBI composite battery separator prepared by the above-mentioned preparation method.

[0058] The present invention will now be described with reference to specific embodiments and comparative examples. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0059] Example 1

[0060] The PE-PBI composite battery separator was prepared according to the following steps:

[0061] S1: Material preparation

[0062] Weigh the following raw materials according to weight: PE 32 parts, PBI 32 parts, nano SiO2 5 parts, hollow mesoporous SiO2 (average particle size 250nm, average pore size 20nm) 5 parts, graphene oxide 6 parts, [BMIM][PF6] ionic liquid 3 parts, [P 13 [TFSI] ionic liquid 3 parts, PVDF-HFP 6 parts, ethylene carbonate 5 parts, LiTFSI 3 parts.

[0063] S2: Raw material pretreatment

[0064] PE was dried at 55℃ for 4 hours to remove moisture, and then ground to an average particle size of 120μm for later use. PBI was ground to achieve an average particle size of 1.0mm for later use.

[0065] Nano-SiO2 was immersed in a 4wt% silane coupling agent KH560 solution (a mixture of NMP and ethanol with a volume ratio of 7:3) at a mass-to-volume ratio of 1g:15mL. The mixture was stirred at 55℃ for 1.5 hours. After centrifugation to separate the precipitate, it was rinsed with deionized water and dried at 85℃ and a vacuum of -0.095MPa for 3.5 hours. Then, it was added to a 1.5wt% polyethylene glycol (weight-average molecular weight 2000 Da) solution (a mixture of NMP and ethanol with a volume ratio of 7:3) at a mass-to-volume ratio of 1g:20mL. The mixture was reacted at 80℃ for 2 hours. After centrifugation to separate the precipitate, it was washed in stages (a mixture of NMP and ethanol with a volume ratio of 7:3 → ethanol → water). The mixture was dried at 85℃ and a vacuum of -0.095MPa for 4 hours to obtain modified nano-SiO2.

[0066] Graphene oxide was added to an NMP / ethanol mixture (NMP to ethanol volume ratio of 7:3) at a mass-to-volume ratio of 0.6 mg / mL. After ultrasonic dispersion at 400W for 1 hour, a 1.5 mg / mL dopamine hydrochloride aqueous solution (dopamine hydrochloride to graphene oxide mass ratio of 2.5:1) was added dropwise to adjust the pH to 8.0. After the addition was completed, the mixture was ultrasonically stirred for 1.5 hours and then matured at 30℃ for 5 hours to obtain the modified GO dispersion.

[0067] S3: Mixing

[0068] 128 parts of organic solvent NMP were added to the reactor, and the temperature was raised to 100°C. Under a nitrogen atmosphere, the PBI ground in step S2 was added, and the mixture was stirred at 200 r / min for 2 hours until the PBI was completely dissolved to form a homogeneous solution. To the above homogeneous solution, the dried and ground PE from step S2, the modified nano-SiO2 prepared in step S2, the modified GO, the hollow mesoporous SiO2, the [BMIM][PF6] ionic liquid, and the [P... 13 [TFSI] Ionic liquid, PVDF-HFP, ethylene carbonate and LiTFSI were first stirred and mixed at 120 r / min for 12 minutes, and then the stirring speed was increased to 250 r / min and stirred and mixed at 90℃ for 5 hours to obtain the film-forming solution.

[0069] S4: Film formation

[0070] The film-forming solution prepared in step S3 was uniformly coated onto a clean glass plate using a blade coating method, with the coating thickness controlled at 40 μm. The glass plate coated with the film-forming solution was placed in a vacuum drying oven and vacuum dried according to the following procedure to form a preliminary composite film: first, the temperature was increased to 45°C at a rate of 5°C / h, and maintained at 45°C and a vacuum of -0.08 MPa for 5 hours; then, the temperature was increased to 60°C at a rate of 5°C / h, and maintained at 60°C and a vacuum of -0.08 MPa for 2 hours; finally, the temperature was increased to 80°C at a rate of 5°C / h, and maintained at 80°C and a vacuum of -0.09 MPa for 2 hours.

[0071] S5: Hot pressing treatment

[0072] The composite membrane obtained in step S4 is placed in a hot press for hot pressing treatment. The hot pressing temperature is set to 130℃, the pressure to 8MPa, and the hot pressing time to 8 minutes.

[0073] S6: Surface finishing

[0074] After hot pressing in step S5, the composite membrane is immersed in a 4wt% silane coupling agent KH550 solution for 1.5 hours. After immersion, it is taken out, rinsed with deionized water, and then dried at 55°C for 2.5 hours to obtain the PE-PBI composite battery separator.

[0075] Example 2

[0076] The only difference between this embodiment and Embodiment 1 is that the [BMIM][PF6] ionic liquid is combined with [P 13 The mass ratio between the TFSI ionic liquids was changed to 1:1.5; all other raw materials and steps were the same as in Example 1. Specifically, this example prepared the PE-PBI composite battery separator according to the following steps:

[0077] S1: Material preparation

[0078] Weigh the following raw materials by weight: PE 32 parts, PBI 32 parts, nano SiO2 5 parts, hollow mesoporous SiO2 (average particle size 250nm, average pore size 20nm) 5 parts, graphene oxide 6 parts, [BMIM][PF6] ionic liquid 2.4 parts, [P 13 [TFSI] Ionic liquid 3.6 parts, PVDF-HFP 6 parts, ethylene carbonate 5 parts, LiTFSI 3 parts.

[0079] S2: Raw material pretreatment

[0080] PE was dried at 55℃ for 4 hours to remove moisture, and then ground to an average particle size of 120μm for later use. PBI was ground to achieve an average particle size of 1.0mm for later use.

[0081] Nano-SiO2 was immersed in a 4wt% silane coupling agent KH560 solution (a mixture of NMP and ethanol with a volume ratio of 7:3) at a mass-to-volume ratio of 1g:15mL. The mixture was stirred at 55℃ for 1.5 hours. After centrifugation to separate the precipitate, it was rinsed with deionized water and dried at 85℃ and a vacuum of -0.095MPa for 3.5 hours. Then, it was added to a 1.5wt% polyethylene glycol (weight-average molecular weight 2000 Da) solution (a mixture of NMP and ethanol with a volume ratio of 7:3) at a mass-to-volume ratio of 1g:20mL. The mixture was reacted at 80℃ for 2 hours. After centrifugation to separate the precipitate, it was washed in stages (a mixture of NMP and ethanol with a volume ratio of 7:3 → ethanol → water). The mixture was dried at 85℃ and a vacuum of -0.095MPa for 4 hours to obtain modified nano-SiO2.

[0082] Graphene oxide was added to an NMP / ethanol mixture (NMP to ethanol volume ratio of 7:3) at a mass-to-volume ratio of 0.6 mg / mL. After ultrasonic dispersion at 400W for 1 hour, a 1.5 mg / mL dopamine hydrochloride aqueous solution (dopamine hydrochloride to graphene oxide mass ratio of 2.5:1) was added dropwise to adjust the pH to 8.0. After the addition was completed, the mixture was ultrasonically stirred for 1.5 hours and then matured at 30℃ for 5 hours to obtain the modified GO dispersion.

[0083] S3: Mixing

[0084] 128 parts of organic solvent NMP were added to the reactor, and the temperature was raised to 100°C. Under a nitrogen atmosphere, the PBI ground in step S2 was added, and the mixture was stirred at 200 r / min for 2 hours until the PBI was completely dissolved to form a homogeneous solution. To the above homogeneous solution, the dried and ground PE from step S2, the modified nano-SiO2 prepared in step S2, the modified GO, the hollow mesoporous SiO2, the [BMIM][PF6] ionic liquid, and the [P... 13 [TFSI] Ionic liquid, PVDF-HFP, ethylene carbonate and LiTFSI were first stirred and mixed at 120 r / min for 12 minutes, and then the stirring speed was increased to 250 r / min and stirred and mixed at 90℃ for 5 hours to obtain the film-forming solution.

[0085] S4: Film formation

[0086] The film-forming solution prepared in step S3 was uniformly coated onto a clean glass plate using a blade coating method, with the coating thickness controlled at 40 μm. The glass plate coated with the film-forming solution was placed in a vacuum drying oven and vacuum dried according to the following procedure to form a preliminary composite film: first, the temperature was increased to 45°C at a rate of 5°C / h, and maintained at 45°C and a vacuum of -0.08 MPa for 5 hours; then, the temperature was increased to 60°C at a rate of 5°C / h, and maintained at 60°C and a vacuum of -0.08 MPa for 2 hours; finally, the temperature was increased to 80°C at a rate of 5°C / h, and maintained at 80°C and a vacuum of -0.09 MPa for 2 hours.

[0087] S5: Hot pressing treatment

[0088] The composite membrane obtained in step S4 is placed in a hot press for hot pressing treatment. The hot pressing temperature is set to 130℃, the pressure to 8MPa, and the hot pressing time to 8 minutes.

[0089] S6: Surface finishing

[0090] After hot pressing in step S5, the composite membrane is immersed in a 4wt% silane coupling agent KH550 solution for 1.5 hours. After immersion, it is taken out, rinsed with deionized water, and then dried at 55°C for 2.5 hours to obtain the PE-PBI composite battery separator.

[0091] Example 3

[0092] The only difference between this embodiment and Embodiment 1 is that the [BMIM][PF6] ionic liquid is combined with [P 13 The mass ratio between the TFSI ionic liquids was changed to 1:0.5; all other raw materials and steps were the same as in Example 1. Specifically, this example prepared the PE-PBI composite battery separator according to the following steps:

[0093] S1: Material preparation

[0094] Weigh the following raw materials by weight: PE 32 parts, PBI 32 parts, nano SiO2 5 parts, hollow mesoporous SiO2 (average particle size 250nm, average pore size 20nm) 5 parts, graphene oxide 6 parts, [BMIM][PF6] ionic liquid 4 parts, [P 13 [TFSI] ionic liquid 2 parts, PVDF-HFP 6 parts, ethylene carbonate 5 parts, LiTFSI 3 parts.

[0095] S2: Raw material pretreatment

[0096] PE was dried at 55℃ for 4 hours to remove moisture, and then ground to an average particle size of 120μm for later use. PBI was ground to achieve an average particle size of 1.0mm for later use.

[0097] Nano-SiO2 was immersed in a 4wt% silane coupling agent KH560 solution (a mixture of NMP and ethanol with a volume ratio of 7:3) at a mass-to-volume ratio of 1g:15mL. The mixture was stirred at 55℃ for 1.5 hours. After centrifugation to separate the precipitate, it was rinsed with deionized water and dried at 85℃ and a vacuum of -0.095MPa for 3.5 hours. Then, it was added to a 1.5wt% polyethylene glycol (weight-average molecular weight 2000 Da) solution (a mixture of NMP and ethanol with a volume ratio of 7:3) at a mass-to-volume ratio of 1g:20mL. The mixture was reacted at 80℃ for 2 hours. After centrifugation to separate the precipitate, it was washed in stages (a mixture of NMP and ethanol with a volume ratio of 7:3 → ethanol → water). The mixture was dried at 85℃ and a vacuum of -0.095MPa for 4 hours to obtain modified nano-SiO2.

[0098] Graphene oxide was added to an NMP / ethanol mixture (NMP to ethanol volume ratio of 7:3) at a mass-to-volume ratio of 0.6 mg / mL. After ultrasonic dispersion at 400W for 1 hour, a 1.5 mg / mL dopamine hydrochloride aqueous solution (dopamine hydrochloride to graphene oxide mass ratio of 2.5:1) was added dropwise to adjust the pH to 8.0. After the addition was completed, the mixture was ultrasonically stirred for 1.5 hours and then matured at 30℃ for 5 hours to obtain the modified GO dispersion.

[0099] S3: Mixing

[0100] 128 parts of organic solvent NMP were added to the reactor, and the temperature was raised to 100°C. Under a nitrogen atmosphere, the PBI ground in step S2 was added, and the mixture was stirred at 200 r / min for 2 hours until the PBI was completely dissolved to form a homogeneous solution. To the above homogeneous solution, the dried and ground PE from step S2, the modified nano-SiO2 prepared in step S2, the modified GO, the hollow mesoporous SiO2, the [BMIM][PF6] ionic liquid, and the [P... 13 [TFSI] Ionic liquid, PVDF-HFP, ethylene carbonate and LiTFSI were first stirred and mixed at 120 r / min for 12 minutes, and then the stirring speed was increased to 250 r / min and stirred and mixed at 90℃ for 5 hours to obtain the film-forming solution.

[0101] S4: Film formation

[0102] The film-forming solution prepared in step S3 was uniformly coated onto a clean glass plate using a blade coating method, with the coating thickness controlled at 40 μm. The glass plate coated with the film-forming solution was placed in a vacuum drying oven and vacuum dried according to the following procedure to form a preliminary composite film: first, the temperature was increased to 45°C at a rate of 5°C / h, and maintained at 45°C and a vacuum of -0.08 MPa for 5 hours; then, the temperature was increased to 60°C at a rate of 5°C / h, and maintained at 60°C and a vacuum of -0.08 MPa for 2 hours; finally, the temperature was increased to 80°C at a rate of 5°C / h, and maintained at 80°C and a vacuum of -0.09 MPa for 2 hours.

[0103] S5: Hot pressing treatment

[0104] The composite membrane obtained in step S4 is placed in a hot press for hot pressing treatment. The hot pressing temperature is set to 130℃, the pressure to 8MPa, and the hot pressing time to 8 minutes.

[0105] S6: Surface finishing

[0106] After hot pressing in step S5, the composite membrane is immersed in a 4wt% silane coupling agent KH550 solution for 1.5 hours. After immersion, it is taken out, rinsed with deionized water, and then dried at 55°C for 2.5 hours to obtain the PE-PBI composite battery separator.

[0107] Example 4

[0108] The only difference between this embodiment and Embodiment 1 is that the [BMIM][PF6] ionic liquid is combined with [P 13 The mass ratio between the ionic liquids [TFSI] was changed to 1:2; all other raw materials and steps were the same as in Example 1. Specifically, this example prepared the PE-PBI composite battery separator according to the following steps:

[0109] S1: Material preparation

[0110] Weigh the following raw materials according to weight: PE 32 parts, PBI 32 parts, nano SiO2 5 parts, hollow mesoporous SiO2 (average particle size 250nm, average pore size 20nm) 5 parts, graphene oxide 6 parts, [BMIM][PF6] ionic liquid 2 parts, [P 13 [TFSI] ionic liquid 4 parts, PVDF-HFP 6 parts, ethylene carbonate 5 parts, LiTFSI 3 parts.

[0111] S2: Raw material pretreatment

[0112] PE was dried at 55℃ for 4 hours to remove moisture, and then ground to an average particle size of 120μm for later use. PBI was ground to achieve an average particle size of 1.0mm for later use.

[0113] Nano-SiO2 was immersed in a 4wt% silane coupling agent KH560 solution (a mixture of NMP and ethanol with a volume ratio of 7:3) at a mass-to-volume ratio of 1g:15mL. The mixture was stirred at 55℃ for 1.5 hours. After centrifugation to separate the precipitate, it was rinsed with deionized water and dried at 85℃ and a vacuum of -0.095MPa for 3.5 hours. Then, it was added to a 1.5wt% polyethylene glycol (weight-average molecular weight 2000 Da) solution (a mixture of NMP and ethanol with a volume ratio of 7:3) at a mass-to-volume ratio of 1g:20mL. The mixture was reacted at 80℃ for 2 hours. After centrifugation to separate the precipitate, it was washed in stages (a mixture of NMP and ethanol with a volume ratio of 7:3 → ethanol → water). The mixture was dried at 85℃ and a vacuum of -0.095MPa for 4 hours to obtain modified nano-SiO2.

[0114] Graphene oxide was added to an NMP / ethanol mixture (NMP to ethanol volume ratio of 7:3) at a mass-to-volume ratio of 0.6 mg / mL. After ultrasonic dispersion at 400W for 1 hour, a 1.5 mg / mL dopamine hydrochloride aqueous solution (dopamine hydrochloride to graphene oxide mass ratio of 2.5:1) was added dropwise to adjust the pH to 8.0. After the addition was completed, the mixture was ultrasonically stirred for 1.5 hours and then matured at 30℃ for 5 hours to obtain the modified GO dispersion.

[0115] S3: Mixing

[0116] 128 parts of organic solvent NMP were added to the reactor, and the temperature was raised to 100°C. Under a nitrogen atmosphere, the PBI ground in step S2 was added, and the mixture was stirred at 200 r / min for 2 hours until the PBI was completely dissolved to form a homogeneous solution. To the above homogeneous solution, the dried and ground PE from step S2, the modified nano-SiO2 prepared in step S2, the modified GO, the hollow mesoporous SiO2, the [BMIM][PF6] ionic liquid, and the [P... 13 [TFSI] Ionic liquid, PVDF-HFP, ethylene carbonate and LiTFSI were first stirred and mixed at 120 r / min for 12 minutes, and then the stirring speed was increased to 250 r / min and stirred and mixed at 90℃ for 5 hours to obtain the film-forming solution.

[0117] S4: Film formation

[0118] The film-forming solution prepared in step S3 was uniformly coated onto a clean glass plate using a blade coating method, with the coating thickness controlled at 40 μm. The glass plate coated with the film-forming solution was placed in a vacuum drying oven and vacuum dried according to the following procedure to form a preliminary composite film: first, the temperature was increased to 45°C at a rate of 5°C / h, and maintained at 45°C and a vacuum of -0.08 MPa for 5 hours; then, the temperature was increased to 60°C at a rate of 5°C / h, and maintained at 60°C and a vacuum of -0.08 MPa for 2 hours; finally, the temperature was increased to 80°C at a rate of 5°C / h, and maintained at 80°C and a vacuum of -0.09 MPa for 2 hours.

[0119] S5: Hot pressing treatment

[0120] The composite membrane obtained in step S4 is placed in a hot press for hot pressing treatment. The hot pressing temperature is set to 130℃, the pressure to 8MPa, and the hot pressing time to 8 minutes.

[0121] S6: Surface finishing

[0122] After hot pressing in step S5, the composite membrane is immersed in a 4wt% silane coupling agent KH550 solution for 1.5 hours. After immersion, it is taken out, rinsed with deionized water, and then dried at 55°C for 2.5 hours to obtain the PE-PBI composite battery separator.

[0123] Example 5

[0124] The only difference between this embodiment and Example 1 is that polyethylene glycol was not grafted onto the surface of nano-SiO2 (only a silane coupling agent was grafted); the other raw materials and steps are the same as in Example 1. Specifically, this embodiment prepares the PE-PBI composite battery separator according to the following steps:

[0125] S1: Material preparation

[0126] Weigh the following raw materials according to weight: PE 32 parts, PBI 32 parts, nano SiO2 5 parts, hollow mesoporous SiO2 (average particle size 250nm, average pore size 20nm) 5 parts, graphene oxide 6 parts, [BMIM][PF6] ionic liquid 3 parts, [P 13 [TFSI] ionic liquid 3 parts, PVDF-HFP 6 parts, ethylene carbonate 5 parts, LiTFSI 3 parts.

[0127] S2: Raw material pretreatment

[0128] PE was dried at 55℃ for 4 hours to remove moisture, and then ground to an average particle size of 120μm for later use. PBI was ground to achieve an average particle size of 1.0mm for later use.

[0129] Nano-SiO2 was immersed in a 4wt% silane coupling agent KH560 solution (the solvent was a mixture of NMP and ethanol, with a volume ratio of NMP to ethanol of 7:3) at a mass-to-volume ratio of 1g:15mL. The mixture was stirred at 55℃ for 1.5 hours. After centrifugation to separate the precipitate, the nano-SiO2 was rinsed with deionized water and dried at 85℃ and a vacuum of -0.095MPa for 3.5 hours to obtain silane coupling agent modified nano-SiO2.

[0130] Graphene oxide was added to an NMP / ethanol mixture (NMP to ethanol volume ratio of 7:3) at a mass-to-volume ratio of 0.6 mg / mL. After ultrasonic dispersion at 400W for 1 hour, a 1.5 mg / mL dopamine hydrochloride aqueous solution (dopamine hydrochloride to graphene oxide mass ratio of 2.5:1) was added dropwise to adjust the pH to 8.0. After the addition was completed, the mixture was ultrasonically stirred for 1.5 hours and then matured at 30℃ for 5 hours to obtain the modified GO dispersion.

[0131] S3: Mixing

[0132] 128 parts of organic solvent NMP were added to the reactor, and the temperature was raised to 100°C. Under a nitrogen atmosphere, the PBI ground in step S2 was added, and the mixture was stirred at 200 r / min for 2 hours until the PBI was completely dissolved to form a homogeneous solution. To the above homogeneous solution, the dried and ground PE from step S2, the silane coupling agent-modified nano-SiO2 prepared in step S2, modified GO, hollow mesoporous SiO2, [BMIM][PF6] ionic liquid, and [P 13 [TFSI] Ionic liquid, PVDF-HFP, ethylene carbonate and LiTFSI were first stirred and mixed at 120 r / min for 12 minutes, and then the stirring speed was increased to 250 r / min and stirred and mixed at 90℃ for 5 hours to obtain the film-forming solution.

[0133] S4: Film formation

[0134] The film-forming solution prepared in step S3 was uniformly coated onto a clean glass plate using a blade coating method, with the coating thickness controlled at 40 μm. The glass plate coated with the film-forming solution was placed in a vacuum drying oven and vacuum dried according to the following procedure to form a preliminary composite film: first, the temperature was increased to 45°C at a rate of 5°C / h, and maintained at 45°C and a vacuum of -0.08 MPa for 5 hours; then, the temperature was increased to 60°C at a rate of 5°C / h, and maintained at 60°C and a vacuum of -0.08 MPa for 2 hours; finally, the temperature was increased to 80°C at a rate of 5°C / h, and maintained at 80°C and a vacuum of -0.09 MPa for 2 hours.

[0135] S5: Hot pressing treatment

[0136] The composite membrane obtained in step S4 is placed in a hot press for hot pressing treatment. The hot pressing temperature is set to 130℃, the pressure to 8MPa, and the hot pressing time to 8 minutes.

[0137] S6: Surface finishing

[0138] After hot pressing in step S5, the composite membrane is immersed in a 4wt% silane coupling agent KH550 solution for 1.5 hours. After immersion, it is taken out, rinsed with deionized water, and then dried at 55°C for 2.5 hours to obtain the PE-PBI composite battery separator.

[0139] Example 6

[0140] The only difference between this embodiment and Example 1 is that polydopamine was not used to modify the graphene oxide; all other raw materials and steps are the same as in Example 1. Specifically, this embodiment prepares the PE-PBI composite battery separator according to the following steps:

[0141] S1: Material preparation

[0142] Weigh the following raw materials according to weight: PE 32 parts, PBI 32 parts, nano SiO2 5 parts, hollow mesoporous SiO2 (average particle size 250nm, average pore size 20nm) 5 parts, graphene oxide 6 parts, [BMIM][PF6] ionic liquid 3 parts, [P 13 [TFSI] ionic liquid 3 parts, PVDF-HFP 6 parts, ethylene carbonate 5 parts, LiTFSI 3 parts.

[0143] S2: Raw material pretreatment

[0144] PE was dried at 55℃ for 4 hours to remove moisture, and then ground to an average particle size of 120μm for later use. PBI was ground to achieve an average particle size of 1.0mm for later use.

[0145] Nano-SiO2 was immersed in a 4wt% silane coupling agent KH560 solution (a mixture of NMP and ethanol with a volume ratio of 7:3) at a mass-to-volume ratio of 1g:15mL. The mixture was stirred at 55℃ for 1.5 hours. After centrifugation to separate the precipitate, it was rinsed with deionized water and dried at 85℃ and a vacuum of -0.095MPa for 3.5 hours. Then, it was added to a 1.5wt% polyethylene glycol (weight-average molecular weight 2000 Da) solution (a mixture of NMP and ethanol with a volume ratio of 7:3) at a mass-to-volume ratio of 1g:20mL. The mixture was reacted at 80℃ for 2 hours. After centrifugation to separate the precipitate, it was washed in stages (a mixture of NMP and ethanol with a volume ratio of 7:3 → ethanol → water). The mixture was dried at 85℃ and a vacuum of -0.095MPa for 4 hours to obtain modified nano-SiO2.

[0146] S3: Mixing

[0147] 128 parts of organic solvent NMP were added to the reactor, and the temperature was raised to 100°C. Under a nitrogen atmosphere, the PBI ground in step S2 was added, and the mixture was stirred at 200 r / min for 2 hours until the PBI was completely dissolved to form a homogeneous solution. To the above homogeneous solution, the dried and ground PE from step S2, the modified nano-SiO2 prepared in step S2, graphene oxide, hollow mesoporous SiO2, [BMIM][PF6] ionic liquid, and [P 13 [TFSI] Ionic liquid, PVDF-HFP, ethylene carbonate and LiTFSI were first stirred and mixed at 120 r / min for 12 minutes, and then the stirring speed was increased to 250 r / min and stirred and mixed at 90℃ for 5 hours to obtain the film-forming solution.

[0148] S4: Film formation

[0149] The film-forming solution prepared in step S3 was uniformly coated onto a clean glass plate using a blade coating method, with the coating thickness controlled at 40 μm. The glass plate coated with the film-forming solution was placed in a vacuum drying oven and vacuum dried according to the following procedure to form a preliminary composite film: first, the temperature was increased to 45°C at a rate of 5°C / h, and maintained at 45°C and a vacuum of -0.08 MPa for 5 hours; then, the temperature was increased to 60°C at a rate of 5°C / h, and maintained at 60°C and a vacuum of -0.08 MPa for 2 hours; finally, the temperature was increased to 80°C at a rate of 5°C / h, and maintained at 80°C and a vacuum of -0.09 MPa for 2 hours.

[0150] S5: Hot pressing treatment

[0151] The composite membrane obtained in step S4 is placed in a hot press for hot pressing treatment. The hot pressing temperature is set to 130℃, the pressure to 8MPa, and the hot pressing time to 8 minutes.

[0152] S6: Surface finishing

[0153] After hot pressing in step S5, the composite membrane is immersed in a 4wt% silane coupling agent KH550 solution for 1.5 hours. After immersion, it is taken out, rinsed with deionized water, and then dried at 55°C for 2.5 hours to obtain the PE-PBI composite battery separator.

[0154] Example 7

[0155] The only difference between this embodiment and Example 1 is that ethylene carbonate is replaced with an equal mass of vinylene carbonate; all other raw materials and steps are the same as in Example 1. Specifically, this embodiment prepares the PE-PBI composite battery separator according to the following steps:

[0156] S1: Material preparation

[0157] Weigh the following raw materials according to weight: PE 32 parts, PBI 32 parts, nano SiO2 5 parts, hollow mesoporous SiO2 (average particle size 250nm, average pore size 20nm) 5 parts, graphene oxide 6 parts, [BMIM][PF6] ionic liquid 3 parts, [P 13 [TFSI] ionic liquid 3 parts, PVDF-HFP 6 parts, vinylene carbonate 5 parts, LiTFSI 3 parts.

[0158] S2: Raw material pretreatment

[0159] PE was dried at 55℃ for 4 hours to remove moisture, and then ground to an average particle size of 120μm for later use. PBI was ground to achieve an average particle size of 1.0mm for later use.

[0160] Nano-SiO2 was immersed in a 4wt% silane coupling agent KH560 solution (a mixture of NMP and ethanol with a volume ratio of 7:3) at a mass-to-volume ratio of 1g:15mL. The mixture was stirred at 55℃ for 1.5 hours. After centrifugation to separate the precipitate, it was rinsed with deionized water and dried at 85℃ and a vacuum of -0.095MPa for 3.5 hours. Then, it was added to a 1.5wt% polyethylene glycol (weight-average molecular weight 2000 Da) solution (a mixture of NMP and ethanol with a volume ratio of 7:3) at a mass-to-volume ratio of 1g:20mL. The mixture was reacted at 80℃ for 2 hours. After centrifugation to separate the precipitate, it was washed in stages (a mixture of NMP and ethanol with a volume ratio of 7:3 → ethanol → water). The mixture was dried at 85℃ and a vacuum of -0.095MPa for 4 hours to obtain modified nano-SiO2.

[0161] Graphene oxide was added to an NMP / ethanol mixture (NMP to ethanol volume ratio of 7:3) at a mass-to-volume ratio of 0.6 mg / mL. After ultrasonic dispersion at 400W for 1 hour, a 1.5 mg / mL dopamine hydrochloride aqueous solution (dopamine hydrochloride to graphene oxide mass ratio of 2.5:1) was added dropwise to adjust the pH to 8.0. After the addition was completed, the mixture was ultrasonically stirred for 1.5 hours and then matured at 30℃ for 5 hours to obtain the modified GO dispersion.

[0162] S3: Mixing

[0163] 128 parts of organic solvent NMP were added to the reactor, and the temperature was raised to 100°C. Under a nitrogen atmosphere, the PBI ground in step S2 was added, and the mixture was stirred at 200 r / min for 2 hours until the PBI was completely dissolved to form a homogeneous solution. To the above homogeneous solution, the dried and ground PE from step S2, the modified nano-SiO2 prepared in step S2, the modified GO, the hollow mesoporous SiO2, the [BMIM][PF6] ionic liquid, and the [P... 13 [TFSI] Ionic liquid, PVDF-HFP, vinylene carbonate and LiTFSI were first stirred and mixed at 120 r / min for 12 minutes, and then the stirring speed was increased to 250 r / min and stirred and mixed at 90℃ for 5 hours to obtain the film-forming solution.

[0164] S4: Film formation

[0165] The film-forming solution prepared in step S3 was uniformly coated onto a clean glass plate using a blade coating method, with the coating thickness controlled at 40 μm. The glass plate coated with the film-forming solution was placed in a vacuum drying oven and vacuum dried according to the following procedure to form a preliminary composite film: first, the temperature was increased to 45°C at a rate of 5°C / h, and maintained at 45°C and a vacuum of -0.08 MPa for 5 hours; then, the temperature was increased to 60°C at a rate of 5°C / h, and maintained at 60°C and a vacuum of -0.08 MPa for 2 hours; finally, the temperature was increased to 80°C at a rate of 5°C / h, and maintained at 80°C and a vacuum of -0.09 MPa for 2 hours.

[0166] S5: Hot pressing treatment

[0167] The composite membrane obtained in step S4 is placed in a hot press for hot pressing treatment. The hot pressing temperature is set to 130℃, the pressure to 8MPa, and the hot pressing time to 8 minutes.

[0168] S6: Surface finishing

[0169] After hot pressing in step S5, the composite membrane is immersed in a 4wt% silane coupling agent KH550 solution for 1.5 hours. After immersion, it is taken out, rinsed with deionized water, and then dried at 55°C for 2.5 hours to obtain the PE-PBI composite battery separator.

[0170] Example 8

[0171] The only difference between this embodiment and Embodiment 1 is that the vacuum drying procedure in step S4 has been changed; all other raw materials and steps are the same as in Embodiment 1. Specifically, this embodiment prepares the PE-PBI composite battery separator according to the following steps:

[0172] S1: Material preparation

[0173] Weigh the following raw materials according to weight: PE 32 parts, PBI 32 parts, nano SiO2 5 parts, hollow mesoporous SiO2 (average particle size 250nm, average pore size 20nm) 5 parts, graphene oxide 6 parts, [BMIM][PF6] ionic liquid 3 parts, [P 13 [TFSI] ionic liquid 3 parts, PVDF-HFP 6 parts, ethylene carbonate 5 parts, LiTFSI 3 parts.

[0174] S2: Raw material pretreatment

[0175] PE was dried at 55℃ for 4 hours to remove moisture, and then ground to an average particle size of 120μm for later use. PBI was ground to achieve an average particle size of 1.0mm for later use.

[0176] Nano-SiO2 was immersed in a 4wt% silane coupling agent KH560 solution (a mixture of NMP and ethanol with a volume ratio of 7:3) at a mass-to-volume ratio of 1g:15mL. The mixture was stirred at 55℃ for 1.5 hours. After centrifugation to separate the precipitate, it was rinsed with deionized water and dried at 85℃ and a vacuum of -0.095MPa for 3.5 hours. Then, it was added to a 1.5wt% polyethylene glycol (weight-average molecular weight 2000 Da) solution (a mixture of NMP and ethanol with a volume ratio of 7:3) at a mass-to-volume ratio of 1g:20mL. The mixture was reacted at 80℃ for 2 hours. After centrifugation to separate the precipitate, it was washed in stages (a mixture of NMP and ethanol with a volume ratio of 7:3 → ethanol → water). The mixture was dried at 85℃ and a vacuum of -0.095MPa for 4 hours to obtain modified nano-SiO2.

[0177] Graphene oxide was added to an NMP / ethanol mixture (NMP to ethanol volume ratio of 7:3) at a mass-to-volume ratio of 0.6 mg / mL. After ultrasonic dispersion at 400W for 1 hour, a 1.5 mg / mL dopamine hydrochloride aqueous solution (dopamine hydrochloride to graphene oxide mass ratio of 2.5:1) was added dropwise to adjust the pH to 8.0. After the addition was completed, the mixture was ultrasonically stirred for 1.5 hours and then matured at 30℃ for 5 hours to obtain the modified GO dispersion.

[0178] S3: Mixing

[0179] 128 parts of organic solvent NMP were added to the reactor, and the temperature was raised to 100°C. Under a nitrogen atmosphere, the PBI ground in step S2 was added, and the mixture was stirred at 200 r / min for 2 hours until the PBI was completely dissolved to form a homogeneous solution. To the above homogeneous solution, the dried and ground PE from step S2, the modified nano-SiO2 prepared in step S2, the modified GO, the hollow mesoporous SiO2, the [BMIM][PF6] ionic liquid, and the [P... 13 [TFSI] Ionic liquid, PVDF-HFP, ethylene carbonate and LiTFSI were first stirred and mixed at 120 r / min for 12 minutes, and then the stirring speed was increased to 250 r / min and stirred and mixed at 90℃ for 5 hours to obtain the film-forming solution.

[0180] S4: Film formation

[0181] The film-forming solution prepared in step S3 was uniformly coated onto a clean glass plate using a blade coating method, with the coating thickness controlled at 40 μm. The glass plate coated with the film-forming solution was placed in a vacuum drying oven and vacuum dried according to the following procedure to form a preliminary composite film: first, the temperature was increased to 45°C at a rate of 5°C / h, and maintained at 45°C and a vacuum of -0.08 MPa for 5 hours; then, the temperature was increased to 80°C at a rate of 5°C / h, and maintained at 80°C and a vacuum of -0.09 MPa for 4 hours.

[0182] S5: Hot pressing treatment

[0183] The composite membrane obtained in step S4 is placed in a hot press for hot pressing treatment. The hot pressing temperature is set to 130℃, the pressure to 8MPa, and the hot pressing time to 8 minutes.

[0184] S6: Surface finishing

[0185] After hot pressing in step S5, the composite membrane is immersed in a 4wt% silane coupling agent KH550 solution for 1.5 hours. After immersion, it is taken out, rinsed with deionized water, and then dried at 55°C for 2.5 hours to obtain the PE-PBI composite battery separator.

[0186] Comparative Example 1

[0187] The only difference between this comparative example and Example 1 is that the two ionic liquids are replaced with equal masses of ethylene carbonate; all other raw materials and steps are the same as in Example 1. Specifically, this comparative example prepares a PE-PBI composite battery separator according to the following steps:

[0188] S1: Material preparation

[0189] Weigh the following raw materials by weight: 32 parts PE, 32 parts PBI, 5 parts nano SiO2, 5 parts hollow mesoporous SiO2 (average particle size 250nm, average pore size 20nm), 6 parts graphene oxide, 6 parts PVDF-HFP, 11 parts ethylene carbonate, and 3 parts LiTFSI.

[0190] S2: Raw material pretreatment

[0191] PE was dried at 55℃ for 4 hours to remove moisture, and then ground to an average particle size of 120μm for later use. PBI was ground to achieve an average particle size of 1.0mm for later use.

[0192] Nano-SiO2 was immersed in a 4wt% silane coupling agent KH560 solution (a mixture of NMP and ethanol with a volume ratio of 7:3) at a mass-to-volume ratio of 1g:15mL. The mixture was stirred at 55℃ for 1.5 hours. After centrifugation to separate the precipitate, it was rinsed with deionized water and dried at 85℃ and a vacuum of -0.095MPa for 3.5 hours. Then, it was added to a 1.5wt% polyethylene glycol (weight-average molecular weight 2000 Da) solution (a mixture of NMP and ethanol with a volume ratio of 7:3) at a mass-to-volume ratio of 1g:20mL. The mixture was reacted at 80℃ for 2 hours. After centrifugation to separate the precipitate, it was washed in stages (a mixture of NMP and ethanol with a volume ratio of 7:3 → ethanol → water). The mixture was dried at 85℃ and a vacuum of -0.095MPa for 4 hours to obtain modified nano-SiO2.

[0193] Graphene oxide was added to an NMP / ethanol mixture (NMP to ethanol volume ratio of 7:3) at a mass-to-volume ratio of 0.6 mg / mL. After ultrasonic dispersion at 400W for 1 hour, a 1.5 mg / mL dopamine hydrochloride aqueous solution (dopamine hydrochloride to graphene oxide mass ratio of 2.5:1) was added dropwise to adjust the pH to 8.0. After the addition was completed, the mixture was ultrasonically stirred for 1.5 hours and then matured at 30℃ for 5 hours to obtain the modified GO dispersion.

[0194] S3: Mixing

[0195] 128 parts of organic solvent NMP were added to the reactor, and the temperature was raised to 100°C. Under a nitrogen atmosphere, the PBI ground in step S2 was added, and the mixture was stirred at 200 r / min for 2 hours until the PBI was completely dissolved to form a homogeneous solution. To this homogeneous solution, the dried and ground PE from step S2, the modified nano-SiO2 obtained in step S2, modified GO, hollow mesoporous SiO2, PVDF-HFP, ethylene carbonate, and LiTFSI were added. The mixture was first stirred at 120 r / min for 12 minutes, then the stirring speed was increased to 250 r / min, and the mixture was stirred at 90°C for 5 hours to obtain the film-forming solution.

[0196] S4: Film formation

[0197] The film-forming solution prepared in step S3 was uniformly coated onto a clean glass plate using a blade coating method, with the coating thickness controlled at 40 μm. The glass plate coated with the film-forming solution was placed in a vacuum drying oven and vacuum dried according to the following procedure to form a preliminary composite film: first, the temperature was increased to 45°C at a rate of 5°C / h, and maintained at 45°C and a vacuum of -0.08 MPa for 5 hours; then, the temperature was increased to 60°C at a rate of 5°C / h, and maintained at 60°C and a vacuum of -0.08 MPa for 2 hours; finally, the temperature was increased to 80°C at a rate of 5°C / h, and maintained at 80°C and a vacuum of -0.09 MPa for 2 hours.

[0198] S5: Hot pressing treatment

[0199] The composite membrane obtained in step S4 is placed in a hot press for hot pressing treatment. The hot pressing temperature is set to 130℃, the pressure to 8MPa, and the hot pressing time to 8 minutes.

[0200] S6: Surface finishing

[0201] After hot pressing in step S5, the composite membrane is immersed in a 4wt% silane coupling agent KH550 solution for 1.5 hours. After immersion, it is taken out, rinsed with deionized water, and then dried at 55°C for 2.5 hours to obtain the PE-PBI composite battery separator.

[0202] Comparative Example 2

[0203] The only difference between this comparative example and Example 1 is that ethylene carbonate is replaced with an equal mass of ionic liquid; all other raw materials and steps are the same as in Example 1. Specifically, this comparative example prepares a PE-PBI composite battery separator according to the following steps:

[0204] S1: Material preparation

[0205] Weigh the following raw materials by weight: PE 32 parts, PBI 32 parts, nano-SiO2 5 parts, hollow mesoporous SiO2 (average particle size 250nm, average pore size 20nm) 5 parts, graphene oxide 6 parts, [BMIM][PF6] ionic liquid 5.5 parts, [P 13 [TFSI] ionic liquid 5.5 parts, PVDF-HFP 6 parts, LiTFSI 3 parts.

[0206] S2: Raw material pretreatment

[0207] PE was dried at 55℃ for 4 hours to remove moisture, and then ground to an average particle size of 120μm for later use. PBI was ground to achieve an average particle size of 1.0mm for later use.

[0208] Nano-SiO2 was immersed in a 4wt% silane coupling agent KH560 solution (a mixture of NMP and ethanol with a volume ratio of 7:3) at a mass-to-volume ratio of 1g:15mL. The mixture was stirred at 55℃ for 1.5 hours. After centrifugation to separate the precipitate, it was rinsed with deionized water and dried at 85℃ and a vacuum of -0.095MPa for 3.5 hours. Then, it was added to a 1.5wt% polyethylene glycol (weight-average molecular weight 2000 Da) solution (a mixture of NMP and ethanol with a volume ratio of 7:3) at a mass-to-volume ratio of 1g:20mL. The mixture was reacted at 80℃ for 2 hours. After centrifugation to separate the precipitate, it was washed in stages (a mixture of NMP and ethanol with a volume ratio of 7:3 → ethanol → water). The mixture was dried at 85℃ and a vacuum of -0.095MPa for 4 hours to obtain modified nano-SiO2.

[0209] Graphene oxide was added to an NMP / ethanol mixture (NMP to ethanol volume ratio of 7:3) at a mass-to-volume ratio of 0.6 mg / mL. After ultrasonic dispersion at 400W for 1 hour, a 1.5 mg / mL dopamine hydrochloride aqueous solution (dopamine hydrochloride to graphene oxide mass ratio of 2.5:1) was added dropwise to adjust the pH to 8.0. After the addition was completed, the mixture was ultrasonically stirred for 1.5 hours and then matured at 30℃ for 5 hours to obtain the modified GO dispersion.

[0210] S3: Mixing

[0211] 128 parts of organic solvent NMP were added to the reactor, and the temperature was raised to 100°C. Under a nitrogen atmosphere, the PBI ground in step S2 was added, and the mixture was stirred at 200 r / min for 2 hours until the PBI was completely dissolved to form a homogeneous solution. To the above homogeneous solution, the dried and ground PE from step S2, the modified nano-SiO2 prepared in step S2, the modified GO, the hollow mesoporous SiO2, the [BMIM][PF6] ionic liquid, and the [P... 13 [TFSI] ionic liquid, PVDF-HFP and LiTFSI were first stirred and mixed at 120 r / min for 12 minutes, and then the stirring speed was increased to 250 r / min and stirred and mixed at 90℃ for 5 hours to obtain the film-forming solution.

[0212] S4: Film formation

[0213] The film-forming solution prepared in step S3 was uniformly coated onto a clean glass plate using a blade coating method, with the coating thickness controlled at 40 μm. The glass plate coated with the film-forming solution was placed in a vacuum drying oven and vacuum dried according to the following procedure to form a preliminary composite film: first, the temperature was increased to 45°C at a rate of 5°C / h, and maintained at 45°C and a vacuum of -0.08 MPa for 5 hours; then, the temperature was increased to 60°C at a rate of 5°C / h, and maintained at 60°C and a vacuum of -0.08 MPa for 2 hours; finally, the temperature was increased to 80°C at a rate of 5°C / h, and maintained at 80°C and a vacuum of -0.09 MPa for 2 hours.

[0214] S5: Hot pressing treatment

[0215] The composite membrane obtained in step S4 is placed in a hot press for hot pressing treatment. The hot pressing temperature is set to 130℃, the pressure to 8MPa, and the hot pressing time to 8 minutes.

[0216] S6: Surface finishing

[0217] After hot pressing in step S5, the composite membrane is immersed in a 4wt% silane coupling agent KH550 solution for 1.5 hours. After immersion, it is taken out, rinsed with deionized water, and then dried at 55°C for 2.5 hours to obtain the PE-PBI composite battery separator.

[0218] Comparative Example 3

[0219] The only difference between this comparative example and Example 1 is that [P] is used instead of Example 1. 13 The [TFSI] ionic liquid was replaced with an equal mass of [BMIM][PF6] ionic liquid; all other raw materials and steps were the same as in Example 1. Specifically, this comparative example prepared a PE-PBI composite battery separator according to the following steps:

[0220] S1: Material preparation

[0221] Weigh the following raw materials by weight: 32 parts PE, 32 parts PBI, 5 parts nano SiO2, 5 parts hollow mesoporous SiO2 (average particle size 250nm, average pore size 20nm), 6 parts graphene oxide, 6 parts [BMIM][PF6] ionic liquid, 6 parts PVDF-HFP, 5 parts ethylene carbonate, and 3 parts LiTFSI.

[0222] S2: Raw material pretreatment

[0223] PE was dried at 55℃ for 4 hours to remove moisture, and then ground to an average particle size of 120μm for later use. PBI was ground to achieve an average particle size of 1.0mm for later use.

[0224] Nano-SiO2 was immersed in a 4wt% silane coupling agent KH560 solution (a mixture of NMP and ethanol with a volume ratio of 7:3) at a mass-to-volume ratio of 1g:15mL. The mixture was stirred at 55℃ for 1.5 hours. After centrifugation to separate the precipitate, it was rinsed with deionized water and dried at 85℃ and a vacuum of -0.095MPa for 3.5 hours. Then, it was added to a 1.5wt% polyethylene glycol (weight-average molecular weight 2000 Da) solution (a mixture of NMP and ethanol with a volume ratio of 7:3) at a mass-to-volume ratio of 1g:20mL. The mixture was reacted at 80℃ for 2 hours. After centrifugation to separate the precipitate, it was washed in stages (a mixture of NMP and ethanol with a volume ratio of 7:3 → ethanol → water). The mixture was dried at 85℃ and a vacuum of -0.095MPa for 4 hours to obtain modified nano-SiO2.

[0225] Graphene oxide was added to an NMP / ethanol mixture (NMP to ethanol volume ratio of 7:3) at a mass-to-volume ratio of 0.6 mg / mL. After ultrasonic dispersion at 400W for 1 hour, a 1.5 mg / mL dopamine hydrochloride aqueous solution (dopamine hydrochloride to graphene oxide mass ratio of 2.5:1) was added dropwise to adjust the pH to 8.0. After the addition was completed, the mixture was ultrasonically stirred for 1.5 hours and then matured at 30℃ for 5 hours to obtain the modified GO dispersion.

[0226] S3: Mixing

[0227] 128 parts of organic solvent NMP were added to the reactor, and the temperature was raised to 100°C. PBI, which had been ground in step S2, was added under a nitrogen atmosphere. The mixture was stirred at 200 r / min for 2 hours until the PBI was completely dissolved to form a homogeneous solution. To this homogeneous solution, the dried and ground PE from step S2, the modified nano-SiO2 obtained in step S2, modified GO, hollow mesoporous SiO2, [BMIM][PF6] ionic liquid, PVDF-HFP, ethylene carbonate, and LiTFSI were added. The mixture was first stirred at 120 r / min for 12 minutes, then the stirring speed was increased to 250 r / min, and the mixture was stirred at 90°C for 5 hours to obtain the film-forming solution.

[0228] S4: Film formation

[0229] The film-forming solution prepared in step S3 was uniformly coated onto a clean glass plate using a blade coating method, with the coating thickness controlled at 40 μm. The glass plate coated with the film-forming solution was placed in a vacuum drying oven and vacuum dried according to the following procedure to form a preliminary composite film: first, the temperature was increased to 45°C at a rate of 5°C / h, and maintained at 45°C and a vacuum of -0.08 MPa for 5 hours; then, the temperature was increased to 60°C at a rate of 5°C / h, and maintained at 60°C and a vacuum of -0.08 MPa for 2 hours; finally, the temperature was increased to 80°C at a rate of 5°C / h, and maintained at 80°C and a vacuum of -0.09 MPa for 2 hours.

[0230] S5: Hot pressing treatment

[0231] The composite membrane obtained in step S4 is placed in a hot press for hot pressing treatment. The hot pressing temperature is set to 130℃, the pressure to 8MPa, and the hot pressing time to 8 minutes.

[0232] S6: Surface finishing

[0233] After hot pressing in step S5, the composite membrane is immersed in a 4wt% silane coupling agent KH550 solution for 1.5 hours. After immersion, it is taken out, rinsed with deionized water, and then dried at 55°C for 2.5 hours to obtain the PE-PBI composite battery separator.

[0234] Comparative Example 4

[0235] The only difference between this comparative example and Example 1 is that the [BMIM][PF6] ionic liquid is replaced with an equal mass of [P] 13 [TFSI] ionic liquid; all other raw materials and steps are the same as in Example 1. Specifically, this comparative example prepares a PE-PBI composite battery separator according to the following steps:

[0236] S1: Material preparation

[0237] Weigh the following raw materials by weight: PE 32 parts, PBI 32 parts, nano-SiO2 5 parts, hollow mesoporous SiO2 (average particle size 250nm, average pore size 20nm) 5 parts, graphene oxide 6 parts, [P 13 [TFSI] ionic liquid 6 parts, PVDF-HFP 6 parts, ethylene carbonate 5 parts, LiTFSI 3 parts.

[0238] S2: Raw material pretreatment

[0239] PE was dried at 55℃ for 4 hours to remove moisture, and then ground to an average particle size of 120μm for later use. PBI was ground to achieve an average particle size of 1.0mm for later use.

[0240] Nano-SiO2 was immersed in a 4wt% silane coupling agent KH560 solution (a mixture of NMP and ethanol with a volume ratio of 7:3) at a mass-to-volume ratio of 1g:15mL. The mixture was stirred at 55℃ for 1.5 hours. After centrifugation to separate the precipitate, it was rinsed with deionized water and dried at 85℃ and a vacuum of -0.095MPa for 3.5 hours. Then, it was added to a 1.5wt% polyethylene glycol (weight-average molecular weight 2000 Da) solution (a mixture of NMP and ethanol with a volume ratio of 7:3) at a mass-to-volume ratio of 1g:20mL. The mixture was reacted at 80℃ for 2 hours. After centrifugation to separate the precipitate, it was washed in stages (a mixture of NMP and ethanol with a volume ratio of 7:3 → ethanol → water). The mixture was dried at 85℃ and a vacuum of -0.095MPa for 4 hours to obtain modified nano-SiO2.

[0241] Graphene oxide was added to an NMP / ethanol mixture (NMP to ethanol volume ratio of 7:3) at a mass-to-volume ratio of 0.6 mg / mL. After ultrasonic dispersion at 400W for 1 hour, a 1.5 mg / mL dopamine hydrochloride aqueous solution (dopamine hydrochloride to graphene oxide mass ratio of 2.5:1) was added dropwise to adjust the pH to 8.0. After the addition was completed, the mixture was ultrasonically stirred for 1.5 hours and then matured at 30℃ for 5 hours to obtain the modified GO dispersion.

[0242] S3: Mixing

[0243] 128 parts of organic solvent NMP were added to the reactor, and the temperature was raised to 100°C. Under a nitrogen atmosphere, the PBI ground in step S2 was added, and the mixture was stirred at 200 r / min for 2 hours until the PBI was completely dissolved to form a homogeneous solution. To the above homogeneous solution, the dried and ground PE from step S2, the modified nano-SiO2 obtained in step S2, the modified GO, the hollow mesoporous SiO2, and [P...] were added. 13 [TFSI] Ionic liquid, PVDF-HFP, ethylene carbonate and LiTFSI were first stirred and mixed at 120 r / min for 12 minutes, and then the stirring speed was increased to 250 r / min and stirred and mixed at 90℃ for 5 hours to obtain the film-forming solution.

[0244] S4: Film formation

[0245] The film-forming solution prepared in step S3 was uniformly coated onto a clean glass plate using a blade coating method, with the coating thickness controlled at 40 μm. The glass plate coated with the film-forming solution was placed in a vacuum drying oven and vacuum dried according to the following procedure to form a preliminary composite film: first, the temperature was increased to 45°C at a rate of 5°C / h, and maintained at 45°C and a vacuum of -0.08 MPa for 5 hours; then, the temperature was increased to 60°C at a rate of 5°C / h, and maintained at 60°C and a vacuum of -0.08 MPa for 2 hours; finally, the temperature was increased to 80°C at a rate of 5°C / h, and maintained at 80°C and a vacuum of -0.09 MPa for 2 hours.

[0246] S5: Hot pressing treatment

[0247] The composite membrane obtained in step S4 is placed in a hot press for hot pressing treatment. The hot pressing temperature is set to 130℃, the pressure to 8MPa, and the hot pressing time to 8 minutes.

[0248] S6: Surface finishing

[0249] After hot pressing in step S5, the composite membrane is immersed in a 4wt% silane coupling agent KH550 solution for 1.5 hours. After immersion, it is taken out, rinsed with deionized water, and then dried at 55°C for 2.5 hours to obtain the PE-PBI composite battery separator.

[0250] Test case

[0251] The PE-PBI composite battery separators prepared according to the methods in the various embodiments and comparative examples were tested for tensile strength, puncture strength, thermal shrinkage, ionic conductivity, porosity, and electrolyte contact angle. The specific test methods are as follows:

[0252] (1) Testing of tensile strength and puncture strength: The mechanical properties of the diaphragm were tested using a universal electronic testing machine.

[0253] (2) Heat shrinkage test: Refer to GB / T36363-2018 to test the heat shrinkage of the diaphragm after being heated at 200℃ for 1 hour.

[0254] (3) Ionic conductivity test: The ionic conductivity of the composite membrane was measured using an electrochemical workstation.

[0255] (4) Electrolyte contact angle test: Ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) were mixed in a volume ratio of 1:1:1 as the electrolyte and tested using a contact angle measuring instrument.

[0256] (5) Porosity test: The density method is used for testing.

[0257] The test results are shown in Table 1.

[0258] Table 1. Test results of diaphragm performance

[0259]

[0260] Analysis of the membrane performance test results of each embodiment and comparative example shows that:

[0261] (1) Example 1 uses two ionic liquids from this invention combined with ethylene carbonate, Comparative Example 1 uses only ethylene carbonate, and Comparative Example 2 uses only these two ionic liquids. The membrane ionic conductivity of Comparative Example 1 and Comparative Example 2 is significantly lower than that of Example 1, indicating that these two ionic liquids and ethylene carbonate can synergistically improve the membrane ionic conductivity. The reason for this is that [BMIM][PF6] and [P] are... 13 [TFSI] and ethylene carbonate interact with LiTFSI, which can improve the dispersion uniformity of LiTFSI in the composite material; wherein, the imidazole ring and pyrrolidine ring in the two ionic liquids form multi-component coordination with the carbonyl group in ethylene carbonate, and TFSI - PF6 - Anions and Li + The formation of dynamically balanced ion clusters helps to prevent ion aggregation. By adjusting the ratio of ionic liquid to carbonate, the porosity of the separator can be controlled. The synergistic design of the PE-PBI substrate and the porous system ensures a high-porosity macroporous structure while maintaining the separator's excellent mechanical strength and high-temperature resistance. The precise matching of high porosity and ion conduction system results in a significant improvement in the separator's ionic conductivity compared to traditional separators, while also optimizing electrolyte wettability, making it suitable for high-rate and high-energy-density battery applications.

[0262] (2) Examples 1 and 2 use [BMIM][PF6] and [P 13 [TFSI] Two ionic liquids were combined, and Comparative Examples 3 and 4 used only [BMIM] and [PF6], respectively. 13 [TFSI, Examples 3 and 4 differed from Examples 1 and 2 by varying the ratio of the two ionic liquids. Table 1 shows that the membrane ionic conductivity of Examples 1 and 2 was higher than that of Comparative Examples 1 and 2, as well as Examples 3 and 4, indicating that [BMIM][PF6] and [P]... 13 The combination of [TFSI] and [BMIM] can significantly improve the ionic conductivity of the membrane, and the effect is influenced by the ratio between the two components. The reason for this is that the lower viscosity of [BMIM] and [PF6] helps to increase the ion migration rate, and [P]... 13 [TFSI] exhibits good compatibility with LiTFSI, which can reduce the thickness of the lithium-ion solvation layer. Based on this, [BMIM][PF6] and [P]... 13[TFSI] work together to achieve higher ionic conductivity.

[0263] (3) In Example 5, only a silane coupling agent was grafted onto the surface of nano-SiO2. In Example 1, polyethylene glycol was further grafted onto the same surface, and the resulting membrane had a higher ionic conductivity than that of Example 5. The reason for this is that by grafting PEG onto the surface of nano-SiO2, the ether bonds (COC) and terminal hydroxyl groups in the PEG molecular chain can be used to complex with the electrolyte components through dipole interactions and hydrogen bonds, which greatly improves the affinity of the membrane for the electrolyte, allowing the electrolyte to quickly wet and be evenly distributed in the membrane pores.

[0264] (4) Based on Example 6, Example 1 modified graphene oxide with polydopamine, and the mechanical properties and ionic conductivity of the resulting membrane were higher than those of Example 6. The reason is that adding polydopamine to graphene oxide can act as a flexible spacer, and PDA molecular chains can be inserted between GO sheets to fix the interlayer spacing at 20~30nm. This not only solves the problem of decreased porosity caused by conventional GO sheet stacking, but also avoids pore blockage caused by sheet shrinkage during drying or hot pressing, and improves the flexibility of the membrane.

[0265] (5) In Example 7, ethylene carbonate in Example 1 was replaced with another carbonate (ethylene carbonate). The resulting membrane had a lower ionic conductivity than that in Example 1, indicating that the choice of carbonate affects the improvement of membrane ionic conductivity. The reason for this is that ethylene carbonate has moderate ring strain and a high dielectric constant, which can more efficiently dissolve LiTFSI and promote its dissociation, thereby increasing the concentration of free lithium ions. Furthermore, the molecular polarity of ethylene carbonate is moderate and compatible with TFSI in LiTFSI. - Anions, as well as [BMIM][PF6], [P] 13 [TFSI] can form a multi-component composite network, reduce ion aggregation, and lower the resistance to lithium-ion migration.

[0266] (6) Compared with Example 1, Example 8 changed the drying process, and the ionic conductivity of the resulting membrane was lower than that of Example 1. The reason for this is that in the drying process of the present invention, heat treatment at 60~65°C can promote the formation of hydrogen bonds between the imidazole groups in the PBI molecular chain and the terminal hydroxyl groups of PEG, strengthen the interfacial bonding, and at the same time allow the ionic liquid to form preliminary ion channels in the PE-PBI matrix. Through the above methods, this stage helps to improve the effect of polyethylene glycol grafted modified nano-SiO2 and ionic liquid, and form a three-dimensional interconnected pore network in the membrane that is more conducive to ion transport.

Claims

1. A method for preparing a PE-PBI composite battery separator, characterized in that, The process involves mixing all raw materials with an organic solvent, coating the film, and then drying it using the following steps: maintaining the temperature at 40-50°C and a vacuum of -0.08 to -0.09 MPa for 4-6 hours, then maintaining the temperature at 60-65°C and a vacuum of -0.08 to -0.09 MPa for 2-3 hours, and finally maintaining the temperature at 75-80°C and a vacuum of -0.09 to -0.095 MPa for 2-3 hours. The raw materials, by weight, include: 58-70 parts of a membrane substrate, 5-10 parts of an ionic liquid, 5-10 parts of carbonate, and 3-6 parts of lithium bis(trifluoromethanesulfonyl)imide. The membrane substrate comprises polyethylene and polybenzimidazole; the ionic liquid comprises 1-butyl-3-methylimidazolium hexafluorophosphate and N-methyl-N-propylpyrrolidine bis(trifluoromethanesulfonyl)imide; and the carbonate comprises ethylene carbonate and / or vinylene carbonate.

2. The preparation method according to claim 1, characterized in that, The mass ratio of 1-butyl-3-methylimidazolium hexafluorophosphate to N-methyl-N-propylpyrrolidine bis(trifluoromethanesulfonyl)imide salt is 1:1 to 1.

5.

3. The preparation method according to claim 1, characterized in that, The carbonate includes ethylene carbonate.

4. The preparation method according to claim 1, characterized in that, The mass ratio of polyethylene to polybenzimidazole is 32~38:26~32.

5. The preparation method according to claim 1, characterized in that, It also includes the following raw materials in parts by weight: 5-7 parts of nano-SiO2 and / or 5-8 parts of graphene oxide; the nano-SiO2 is pre-grafted with polyethylene glycol before use; the graphene oxide is pre-modified with polydopamine before use.

6. The preparation method according to claim 5, characterized in that, The polyethylene glycol is grafted onto nano-SiO2 using an epoxy silane coupling agent; the weight-average molecular weight of the polyethylene glycol is 2000~2500 Da.

7. The preparation method according to claim 1 or 4, characterized in that, It also includes the following raw materials in parts by weight: 5-8 parts of hollow mesoporous SiO2 and / or 8-12 parts of polyvinylidene fluoride-hexafluoropropylene copolymer; wherein the average particle size of the hollow mesoporous SiO2 is 250-300 nm and the average pore size is 20-30 nm.

8. The preparation method according to claim 1, characterized in that, The PE-PBI composite battery separator is modified with a coupling agent; the coupling agent includes γ-aminopropyltriethoxysilane and / or N-β-aminoethyl-γ-aminopropyltrimethoxysilane.

9. The application of battery separators in lithium-ion batteries, characterized in that, The battery separator is a PE-PBI composite battery separator prepared by the preparation method described in any one of claims 1 to 8.

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