Preparation method and application of electrospun hybrid nanofiber separator

Abstract

The application provides a preparation method and application of an electrospinning hybrid nanofiber diaphragm, and is based on in-situ grafting modification principles of cage-type silsesquioxane; residual functional groups on the cage-type silsesquioxane after grafting are used to react with functional groups of organic ligands in MOF, so that the MOF is successfully grafted onto the nanofiber film; the nanofiber film with enhanced structure is controllably prepared; meanwhile, the nanofiber film has a multi-level pore adjusting structure; the movement of anions and cations in a lithium ion battery is effectively controlled; the lithium ion passing number is enhanced; and the electrochemical performance of the lithium ion battery is improved; the rate performance and the cycle performance can be obviously improved compared with commercial polyolefin diaphragms. Meanwhile, by introducing the MOF structure, the mechanical properties and the thermal stability of the electrospinning nanofiber film are further enhanced, so that the assembled battery has good mechanical properties and flame retardant properties.

Description

Technical Field

[0001] This invention relates to the field of lithium battery separator materials technology, and in particular to a method for preparing an electrospun hybrid nanofiber separator and its application. Background Technology

[0002] Currently, commercially available lithium metal battery separator materials still largely utilize traditional polyolefin stretched separators. Newly developed electrospun fiber membranes, compared to traditional polyolefin stretched separators, offer a wider selection of matrix materials and higher porosity and hydrophilicity. A representative example is polyvinylidene fluoride (PVDF) spun membrane. Metal-organic frameworks (MOFs) are composed of inorganic metal ion portions and organic ligand portions, representing a class of porous coordination polymers with large specific surface areas. MOFs exhibit significant porosity and structural tunability; their introduction into separators can significantly enhance lithium-ion transport and guide their uniform distribution. Furthermore, MOFs possess excellent structural tunability, allowing for the design of different types of organic ligands and metal cluster structures based on the functional requirements of the polymer material. From the perspective of grafted functional groups, cage-type silsesquioxanes, due to their rigid structure similar to silica inorganic molecules, can impart excellent thermal stability and mechanical strength to the diaphragm when introduced into spinning membranes. Furthermore, the R groups (vinyl, phenyl, epoxy, mercapto, amino, acryloyloxy, alkyl, etc.) of cage-type silsesquioxanes can impart specific properties such as high mechanical strength, heat resistance, and flame retardancy to the material according to the design.

[0003] Simultaneously, introducing MOF and cage-type silsesquioxane into the electrospinning membrane through a chemical reaction and adjusting the chemical combination ratio between the two to enhance the physical properties and electrochemical performance of the spun fibers is rarely reported or invented in the currently developed related technologies. Most similar technologies involve physical blending, which makes it difficult to achieve the desired performance.

[0004] For example, Chinese invention patents CN202210452083.2 and CN202210165700.0 describe how porous MOF materials are distributed in a single-layer, tightly packed manner on the surface of a two-dimensional material, forming a multilayer composite fiber membrane with a polymer material that has lithium-ion conductivity; Chinese invention patents CN202111381744.9 and CN202111407834.0 describe how double-bonded cage-like silsesquioxane materials react under the initiation of a photoinitiator to generate a three-dimensional network, which then forms an organic-inorganic hybrid fiber membrane with a porous fiber membrane material; and Chinese invention patent CN202210624551.X describes how a metal-organic framework reference solid electrolyte is prepared by using a commercial separator as a substrate, MOF as a carrier, and depositing metal nanoparticles on the substrate.

[0005] The above technology has the following shortcomings:

[0006] 1) Physical addition of MOF carries the risk of MOF molecules escaping from the matrix, which leads to a decrease in lithium-ion conduction efficiency;

[0007] 2) The cage-like silsesquioxane molecules did not form a chemical complex with the polymer matrix of the separator membrane, and the reinforcing effect on the matrix was not obvious;

[0008] 3) The preparation process of multilayer composite membranes is relatively complex, and the interfacial effects of the physical layered structure bring a lot of uncertainty to the stability and performance of the membrane structure. Summary of the Invention

[0009] To address the technical problems of existing lithium metal battery separator materials, such as low safety, complex manufacturing processes, and inapplicability to large-scale applications of high-energy-density batteries, this invention provides a method for preparing electrospun hybrid nanofiber separators from the perspective of in-situ growth and chemical grafting modification. This method involves electrospinning to prepare polyvinylidene fluoride (PVDF) separators, introducing cage-like silsesquioxanes onto the surface of the spun membrane under ultraviolet light irradiation via electrostatic spraying, immersing the nanofiber membrane in a solution containing MOF precursors, and then using a hydrothermal method to grow MOFs in situ on the surface of the fiber membrane. The invention also includes its application.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0011] A method for preparing an electrospun hybrid nanofiber membrane includes the following steps:

[0012] (1) Preparation of spinning solution: Polyvinylidene fluoride, photoinitiator benzophenone and silsesquioxane are dissolved in a mixed solution of dimethylacetamide and acetone with a volume ratio of 4:6. After stirring thoroughly for 2 hours under light-protected conditions, the solution is allowed to stand to remove bubbles and obtain the spinning solution.

[0013] (2) Preparation of MOF precursor reaction solution: In a mixed solution of Cu(NO3)2·3H2O and 2-aminoterephthalic acid, N,N-dimethylformamide was added and ultrasonically vibrated until completely dissolved. Ceramide nitrate was added to obtain MOF precursor reaction solution.

[0014] (3) Preparation of nanofiber membrane: Under ultraviolet light, the spinning solution obtained in step (1) is added to a syringe, and electrospinning is performed under appropriate voltage and feed rate. The spun membrane is collected and then post-processed to obtain silsesquioxane in-situ grafted modified nanofiber membrane.

[0015] (4) Preparation of electrospun nanofiber membrane: The nanofiber membrane in step (3) is placed in the MOF precursor solution obtained in step (2) and reacted in a high-pressure reactor at 110°C for 24 hours. After the reaction, the fiber membrane is repeatedly washed and dried to obtain the membrane. From the perspective of in-situ growth and chemical grafting modification, polyvinylidene fluoride membrane is prepared by electrospinning. Under ultraviolet light irradiation, cage-type silsesquioxane is introduced into the surface of the spun membrane by electrostatic spraying. The nanofiber membrane is then immersed in a solution containing MOF precursor. The MOF is grown in situ on the surface of the fiber membrane by hydrothermal method to obtain an electrospun nanofiber membrane with enhanced fiber mechanical properties and dimensional stability.

[0016] Preferably, in step (1), the amount of polyvinylidene fluoride added is 10 parts by mass, the amount of benzophenone added is 5 wt.% of the mass of polyvinylidene fluoride, and the mass concentration of the spinning solution is 10 wt.%.

[0017] Preferably, in step (1), the amount of silsesquioxane added is 6 to 12 wt.% of the mass of polyvinylidene fluoride.

[0018] Preferably, in step (2), the molar ratio of Cu(NO3)2·3H2O to 2-aminoterephthalic acid is 1:1.

[0019] Preferably, in step (2), the amount of cerium nitrate added is 5%; the amount of MOF precursor added is 0-200 wt.% of sesquioxane.

[0020] Preferably, in step (3), the irradiance of the ultraviolet light is 100–500 mW / cm². 2 The distance between the electrospinning device, the electro-spraying head, and the receiving plate is 10–15 cm.

[0021] Preferably, in step (3), the voltage of the electrospinning is 12-22kV and the feed rate is 2-6mL / h.

[0022] Preferably, in step (3), the post-treatment method of the spun film is as follows: the spun film is fully immersed in dichloromethane and ultrasonically washed for 30 minutes, repeated more than three times, and then placed in an oven to dry overnight.

[0023] Preferably, in step (4), the solvent used in the washing process is anhydrous N,N-dimethylformamide and anhydrous ethanol.

[0024] Application of electrospun hybrid nanofiber separators prepared by any of the above methods in high-performance lithium metal batteries.

[0025] The principle of this invention is: (1) During the preparation of the diaphragm, a hybrid nano-sized monomer with good thermal and mechanical stability and unique chemical reactivity is introduced to improve the mechanical properties and material size stability of the diaphragm;

[0026] (2) During the electrospinning process, under the condition of ultraviolet irradiation, the polymer chain of polyvinylidene fluoride generates free radical active sites through photoinitiator. At this time, the functional groups on the cage-type silsesquioxane initiate polymerization in situ at the active sites of polyvinylidene fluoride.

[0027] (3) After post-treatment, the fiber membrane prepared above is immersed in a solution containing MOF precursor. The functional groups remaining on the cage-type silsesquioxane react with the organic ligands in the MOF reaction solution under the action of the catalyst. At the same time, metal ions and organic ligands grow in situ, so that MOF is successfully grafted into the electrospun fiber membrane, and an electrospun nanofiber membrane with chemical grafting modification and multi-level pore structure is obtained.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] 1. This application provides a method for preparing an electrospun hybrid nanofiber membrane. Based on the in-situ grafting modification principle of cage-like silsesquioxanes, this invention utilizes the residual functional groups on the grafted cage-like silsesquioxanes to react with the functional groups of organic ligands in the MOF, successfully grafting the MOF onto the nanofiber membrane. This allows for the controlled preparation of a nanofiber membrane with a reinforced structure and a multi-level pore structure, effectively controlling the movement of cations and anions in the lithium-ion battery, enhancing the lithium-ion throughput, and improving the electrochemical performance of the lithium-ion battery. Its rate performance and cycle performance are significantly improved compared to commercial polyolefin membranes. Furthermore, by introducing the MOF structure, the mechanical properties and thermal stability of the electrospun nanofiber membrane are enhanced, endowing the assembled battery with excellent mechanical and flame-retardant properties.

[0030] 2. The electrospun hybrid nanofiber separator provided in this application is used in high-performance lithium metal batteries. The cage-type silsesquioxane and MOF are both prepared in the laboratory with well-defined structures. The chemical structure, mechanical and electrochemical properties of the prepared electrospun nanofiber membrane are controllable. The preparation method is controllable and precise. The implementation process is simple and can be carried out under normal conditions. It has high safety and the post-preparation processing is simple and convenient. The lithium battery assembled using the nanofiber separator of this invention has excellent electrochemical performance, service life and safety. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0032] Figure 1 The infrared spectrum of the MOF-modified hybrid electrospun nanofiber membrane (MOF / silsesquioxane-FM) of Example 1 is shown below.

[0033] Figure 2 The graph shows the cycle performance test results of the battery assembled from the MOF-modified hybrid electrospun nanofiber membrane (MOF / silsesquioxane-FM) of Example 1 and the commercial separator (Celgard).

[0034] Figure 3 The graph shows the rate performance test results of the battery assembled from the MOF-modified hybrid electrospun nanofiber membrane (MOF / silsesquioxane-FM) of Example 1 and the commercial separator (Celgard). Detailed Implementation

[0035] The specific technical solution of the present invention will be described below with reference to specific embodiments 1-12:

[0036] Example 1:

[0037] (1) Add 1.0g polyvinylidene fluoride, 1mg photoinitiator benzophenone and 80mg silsesquioxane to a 20ml serum bottle, add 15.00mL of dimethylacetamide:acetone (4:6) mixed solvent, stir thoroughly for 2h in the dark, and let stand to remove bubbles to obtain a spinning solution with a concentration of 10wt.%. Add 86mg Cu(NO3)2·3H2O and 64mg 2-aminoterephthalic acid to a 20ml serum bottle, add 12ml DMF and sonicate until completely dissolved, add 5mg cerium nitrate to obtain MOF precursor reaction solution;

[0038] (2) The spinning solution obtained in step (1) is added to a 50mL dispensing syringe and clamped into the electrospinning equipment. The distance between the nozzle and the receiving roller is adjusted to 12cm. The receiving roller of the electrospinning is wrapped with aluminum foil, the ultraviolet lamp is turned on, and the irradiation intensity is adjusted to 100-500mW / cm at the roller. 2 Simultaneously, turn on the spinning device of the spinning solution and adjust the spinning parameters as follows: spinning voltage 15kV, spinning solution feed rate 4mL / h; after the spinning solution is completely deposited on the aluminum foil, stop the electrospinning device, peel off the aluminum foil and immerse it in DCM for 30min, and change the solvent three times to remove ungrafted silsesquioxane, and then put it in an oven to dry the solvent to obtain an electrospun nanofiber membrane;

[0039] (3) The electrospun nanofiber membrane obtained in step (2) was placed in the MOF precursor reaction solution and transferred to a high-pressure reactor lined with polytetrafluoroethylene. The reactor was then placed in an oven at 110°C and reacted for 24 hours. After the reaction was completed, the fiber membrane was removed and repeatedly washed with anhydrous DMF and anhydrous ethanol and dried to finally obtain the MOF-modified hybrid composite electrospun nanofiber membrane.

[0040] (4) Using MOF-modified hybrid composite electrospun nanofiber membrane as separator, LFP as positive electrode and lithium metal sheet as negative electrode, CR2032 half cell was assembled in glove box. At the same time, commercial Celgard separator was used as a control and assembled into half cell. After standing for 24 hours, the rate performance and cycle performance of the battery were tested. The test results are shown in Table 1.

[0041] Example 2:

[0042] (1) Add 1.0g polyvinylidene fluoride, 1mg photoinitiator benzophenone and 60mg silsesquioxane to a 20ml serum bottle, add 15.00mL of dimethylacetamide:acetone (4:6) mixed solvent, stir thoroughly in the dark for 2h, and let stand to remove bubbles to obtain a spinning solution with a concentration of 10wt.%; add 35mg Cu(NO3)2·3H2O and 25mg 2-aminoterephthalic acid to a 20ml serum bottle, add 18ml DMF and sonicate until completely dissolved, add 5mg cerium nitrate to obtain MOF precursor reaction solution;

[0043] (2) The spinning solution obtained in step (1) is added to a 20mL dispensing syringe and clamped into the electrospinning equipment. The distance between the nozzle and the receiving roller is adjusted to 10cm. The receiving roller of the electrospinning is wrapped with aluminum foil, the ultraviolet lamp is turned on, and the irradiation intensity is adjusted to 100-500mW / cm at the roller. 2 Simultaneously, turn on the spinning device of the spinning solution and adjust the spinning parameters as follows: spinning voltage 18kV, spinning solution feed rate 2mL / h; after the spinning solution is completely deposited on the aluminum foil, stop the electrospinning device, peel off the aluminum foil and immerse it in DCM dichloromethane for 30min, and change the solvent three times to remove ungrafted silsesquioxane, and then put it in an oven to dry the solvent to obtain an electrospun nanofiber membrane;

[0044] (3) The electrospun nanofiber membrane obtained in step (2) was placed in the MOF precursor reaction solution and transferred to a high-pressure reactor lined with polytetrafluoroethylene. The reactor was then placed in an oven at 110°C and reacted for 24 hours. After the reaction was completed, the fiber membrane was removed and repeatedly washed with anhydrous DMF and anhydrous ethanol and dried to finally obtain the MOF-modified hybrid composite electrospun nanofiber membrane.

[0045] (4) Using MOF-modified hybrid composite electrospun nanofiber membrane as separator, LFP as positive electrode and lithium metal sheet as negative electrode, CR2032 half cell was assembled in glove box. At the same time, commercial Celgard separator was used as a control and assembled into half cell. After standing for 24 hours, the rate performance and cycle performance of the battery were tested. The test results are shown in Table 1.

[0046] Example 3:

[0047] (1) Add 1.0g polyvinylidene fluoride, 1mg photoinitiator benzophenone and 60mg silsesquioxane to a 20ml serum bottle, add 15.00mL of dimethylacetamide:acetone (4:6) mixed solvent, stir thoroughly in the dark for 2h, and let stand to remove bubbles to obtain a spinning solution with a concentration of 10wt.%; add 18mg Cu(NO3)2·3H2O and 12mg 2-aminoterephthalic acid to a 20ml serum bottle, add 12ml DMF and sonicate until completely dissolved, add 5mg cerium nitrate to obtain MOF precursor reaction solution;

[0048] (2) The spinning solution obtained in step (1) is added to a 20mL dispensing syringe and clamped into the electrospinning equipment. The distance between the nozzle and the receiving roller is adjusted to 10cm. The receiving roller of the electrospinning is wrapped with aluminum foil, the ultraviolet lamp is turned on, and the irradiation intensity is adjusted to 100-500mW / cm at the roller. 2 Simultaneously, turn on the spinning device of the spinning solution and adjust the spinning parameters as follows: spinning voltage 12kV, spinning solution feed rate 6mL / h; after the spinning solution is completely deposited on the aluminum foil, stop the electrospinning device, peel off the aluminum foil and immerse it in DCM for 30min, and change the solvent three times to remove ungrafted silsesquioxane, and then put it in an oven to dry the solvent to obtain an electrospun nanofiber membrane;

[0049] (3) The electrospun nanofiber membrane obtained in step (2) was placed in the MOF precursor reaction solution and transferred to a high-pressure reactor lined with polytetrafluoroethylene. The reactor was then placed in an oven at 110°C and reacted for 24 hours. After the reaction was completed, the fiber membrane was removed and repeatedly washed with anhydrous DMF and anhydrous ethanol and dried to finally obtain the MOF-modified hybrid composite electrospun nanofiber membrane.

[0050] (4) Using MOF-modified hybrid composite electrospun nanofiber membrane as separator, LFP as positive electrode and lithium metal sheet as negative electrode, CR2032 half cell was assembled in glove box. At the same time, commercial Celgard separator was used as a control and assembled into half cell. After standing for 24 hours, the rate performance and cycle performance of the battery were tested. The test results are shown in Table 1.

[0051] Example 4:

[0052] (1) Add 1.0g polyvinylidene fluoride, 1mg photoinitiator benzophenone and 60mg silsesquioxane to a 20ml serum bottle, add 15.00mL of dimethylacetamide:acetone (4:6) mixed solvent, stir thoroughly in the dark for 2h, and let stand to remove bubbles to obtain a spinning solution with a concentration of 10wt.%; add 18mg Cu(NO3)2·3H2O and 12mg 2-aminoterephthalic acid to a 20ml serum bottle, add 12ml DMF and sonicate until completely dissolved, add 5mg cerium nitrate to obtain MOF precursor reaction solution;

[0053] (2) The spinning solution obtained in step (1) is added to a 20mL dispensing syringe and clamped into the electrospinning equipment. The distance between the nozzle and the receiving roller is adjusted to 12cm. The receiving roller of the electrospinning is wrapped with aluminum foil, the ultraviolet lamp is turned on, and the irradiation intensity is adjusted to 100-500mW / cm at the roller. 2 Simultaneously, turn on the spinning device of the spinning solution and adjust the spinning parameters as follows: spinning voltage 22kV, spinning solution feed rate 6mL / h; after the spinning solution is completely deposited on the aluminum foil, stop the electrospinning device, peel off the aluminum foil and immerse it in DCM for 30min, and change the solvent three times to remove ungrafted silsesquioxane, and then put it in an oven to dry the solvent to obtain an electrospun nanofiber membrane;

[0054] (3) The electrospun nanofiber membrane obtained in step (2) was placed in the MOF precursor reaction solution and transferred to a high-pressure reactor lined with polytetrafluoroethylene. The reactor was then placed in an oven at 110°C and reacted for 24 hours. After the reaction was completed, the fiber membrane was removed and repeatedly washed with anhydrous DMF and anhydrous ethanol and dried to finally obtain the MOF-modified hybrid composite electrospun nanofiber membrane.

[0055] (4) Using MOF-modified hybrid composite electrospun nanofiber membrane as separator, LFP as positive electrode and lithium metal sheet as negative electrode, CR2032 half cell was assembled in glove box. At the same time, commercial Celgard separator was used as a control and assembled into half cell. After standing for 24 hours, the rate performance and cycle performance of the battery were tested. The test results are shown in Table 1.

[0056] Example 5:

[0057] (1) Add 1.0g polyvinylidene fluoride, 1mg photoinitiator benzophenone and 80mg silsesquioxane to a 20ml serum bottle, add 15.00mL of dimethylacetamide:acetone (4:6) mixed solvent, stir thoroughly in the dark for 2h and let stand to remove bubbles to obtain a spinning solution with a concentration of 10wt.%; add 46mg Cu(NO3)2·3H2O and 34mg 2-aminoterephthalic acid to a 20ml serum bottle, add 15ml DMF and sonicate until completely dissolved, add 5mg cerium nitrate to obtain MOF precursor reaction solution.

[0058] (2) The spinning solution obtained in step (1) is added to a 20mL dispensing syringe and clamped into the electrospinning equipment. The distance between the nozzle and the receiving roller is adjusted to 12cm. The receiving roller of the electrospinning is wrapped with aluminum foil, the ultraviolet lamp is turned on, and the irradiation intensity is adjusted to 100-500mW / cm at the roller. 2Simultaneously, turn on the spinning device of the spinning solution and adjust the spinning parameters as follows: spinning voltage 18kV, spinning solution feed rate 4mL / h; after the spinning solution is completely deposited on the aluminum foil, stop the electrospinning device, peel off the aluminum foil and immerse it in DCM for 30min, and change the solvent three times to remove ungrafted silsesquioxane, and then put it in an oven to dry the solvent to obtain an electrospun nanofiber membrane;

[0059] (3) The electrospun nanofiber membrane obtained in step (2) was placed in the MOF precursor reaction solution and transferred to a high-pressure reactor lined with polytetrafluoroethylene. The reactor was then placed in an oven at 110°C and reacted for 24 hours. After the reaction was completed, the fiber membrane was removed and repeatedly washed with anhydrous DMF and anhydrous ethanol and dried to finally obtain the MOF-modified hybrid composite electrospun nanofiber membrane.

[0060] (4) Using MOF-modified hybrid composite electrospun nanofiber membrane as separator, LFP as positive electrode and lithium metal sheet as negative electrode, CR2032 half cell was assembled in glove box. At the same time, commercial Celgard separator was used as a control and assembled into half cell. After standing for 24 hours, the rate performance and cycle performance of the battery were tested. The test results are shown in Table 1.

[0061] Example 6:

[0062] (1) Add 1.0g polyvinylidene fluoride, 1mg photoinitiator benzophenone and 80mg silsesquioxane to a 20ml serum bottle, add 15.00mL of dimethylacetamide:acetone (4:6) mixed solvent, stir thoroughly in the dark for 2h and let stand to remove bubbles to obtain a spinning solution with a concentration of 10wt.%; add 70mg Cu(NO3)2·3H2O and 50mg 2-aminoterephthalic acid to a 20ml serum bottle, add 15ml DMF and sonicate until completely dissolved, add 5mg cerium nitrate to obtain MOF precursor reaction solution;

[0063] (2) The spinning solution obtained in step (1) is added to a 20mL dispensing syringe and clamped into the electrospinning equipment. The distance between the nozzle and the receiving roller is adjusted to 15cm. The receiving roller of the electrospinning is wrapped with aluminum foil, the ultraviolet lamp is turned on, and the irradiation intensity is adjusted to 100-500mW / cm at the roller. 2 Simultaneously, turn on the spinning device of the spinning solution and adjust the spinning parameters as follows: spinning voltage 22kV, spinning solution feed rate 2mL / h; after the spinning solution is completely deposited on the aluminum foil, stop the electrospinning device, peel off the aluminum foil and immerse it in DCM for 30min, and change the solvent three times to remove ungrafted silsesquioxane, and then put it in an oven to dry the solvent to obtain an electrospun nanofiber membrane;

[0064] (3) The electrospun nanofiber membrane obtained in step (2) was placed in the MOF precursor reaction solution and transferred to a high-pressure reactor lined with polytetrafluoroethylene. The reactor was then placed in an oven at 110°C and reacted for 24 hours. After the reaction was completed, the fiber membrane was removed and repeatedly washed with anhydrous DMF and anhydrous ethanol and dried to finally obtain the MOF-modified hybrid composite electrospun nanofiber membrane.

[0065] (4) Using MOF-modified hybrid composite electrospun nanofiber membrane as separator, LFP as positive electrode and lithium metal sheet as negative electrode, CR2032 half cell was assembled in glove box. At the same time, commercial Celgard separator was used as a control and assembled into half cell. After standing for 24 hours, the rate performance and cycle performance of the battery were tested. The test results are shown in Table 1.

[0066] Example 7:

[0067] (1) Add 1.0g polyvinylidene fluoride, 1mg photoinitiator benzophenone and 80mg silsesquioxane to a 20ml serum bottle, add 15.00mL of dimethylacetamide:acetone (4:6) mixed solvent, stir thoroughly in the dark for 2h and then let stand to remove bubbles to obtain a spinning solution with a concentration of 10wt.%; add 23mg Cu(NO3)2·3H2O and 17mg 2-aminoterephthalic acid to a 20ml serum bottle, add 8ml DMF and sonicate until completely dissolved, add 5mg cerium nitrate to obtain MOF precursor reaction solution;

[0068] (2) The spinning solution obtained in step (1) is added to a 20mL dispensing syringe and clamped into the electrospinning equipment. The distance between the nozzle and the receiving roller is adjusted to 15cm. The receiving roller of the electrospinning is wrapped with aluminum foil, the ultraviolet lamp is turned on, and the irradiation intensity is adjusted to 100-500mW / cm at the roller. 2 Simultaneously, turn on the spinning device of the spinning solution and adjust the spinning parameters as follows: spinning voltage 12kV, spinning solution feed rate 4mL / h; after the spinning solution is completely deposited on the aluminum foil, stop the electrospinning device, peel off the aluminum foil and immerse it in DCM for 30min, and change the solvent three times to remove ungrafted silsesquioxane, and then put it in an oven to dry the solvent to obtain an electrospun nanofiber membrane;

[0069] (3) The electrospun nanofiber membrane obtained in step (2) was placed in the MOF precursor reaction solution and transferred to a high-pressure reactor lined with polytetrafluoroethylene. The reactor was then placed in an oven at 110°C and reacted for 24 hours. After the reaction was completed, the fiber membrane was removed and repeatedly washed with anhydrous DMF and anhydrous ethanol and dried to finally obtain the MOF-modified hybrid composite electrospun nanofiber membrane.

[0070] (4) Using MOF-modified hybrid composite electrospun nanofiber membrane as separator, LFP as positive electrode and lithium metal sheet as negative electrode, CR2032 half cell was assembled in glove box. At the same time, commercial Celgard separator was used as a control and assembled into half cell. After standing for 24 hours, the rate performance and cycle performance of the battery were tested. The test results are shown in Table 1.

[0071] Example 8:

[0072] (1) Add 1.0g polyvinylidene fluoride, 1mg photoinitiator benzophenone and 100mg silsesquioxane to a 20ml serum bottle, add 15.00mL of dimethylacetamide:acetone (4:6) mixed solvent, stir thoroughly in the dark for 2h, and let stand to remove bubbles to obtain a spinning solution with a concentration of 10wt.%; add 60mg Cu(NO3)2·3H2O and 45mg 2-aminoterephthalic acid to a 20mL serum bottle, add 10ml DMF and sonicate until completely dissolved, add 5mg cerium nitrate to obtain MOF precursor reaction solution;

[0073] (2) The spinning solution obtained in step (1) is added to a 20mL dispensing syringe and clamped into the electrospinning equipment. The distance between the nozzle and the receiving roller is adjusted to 12cm. The receiving roller of the electrospinning is wrapped with aluminum foil, the ultraviolet lamp is turned on, and the irradiation intensity is adjusted to 100-500mW / cm at the roller. 2 Simultaneously, turn on the spinning device of the spinning solution and adjust the spinning parameters as follows: spinning voltage 15kV, spinning solution feed rate 4mL / h; after the spinning solution is completely deposited on the aluminum foil, stop the electrospinning device, peel off the aluminum foil and immerse it in DCM for 30min, and change the solvent three times to remove ungrafted silsesquioxane, and then put it in an oven to dry the solvent to obtain an electrospun nanofiber membrane;

[0074] (3) The electrospun nanofiber membrane obtained in step (2) was placed in the MOF precursor reaction solution and transferred to a high-pressure reactor lined with polytetrafluoroethylene. The reactor was then placed in an oven at 110°C and reacted for 24 hours. After the reaction was completed, the fiber membrane was removed and repeatedly washed with anhydrous DMF and anhydrous ethanol and dried to finally obtain the MOF-modified hybrid composite electrospun nanofiber membrane.

[0075] (4) Using MOF-modified hybrid composite electrospun nanofiber membrane as separator, LFP as positive electrode and lithium metal sheet as negative electrode, CR2032 half cell was assembled in glove box. At the same time, commercial Celgard separator was used as a control and assembled into half cell. After standing for 24 hours, the rate performance and cycle performance of the battery were tested. The test results are shown in Table 1.

[0076] Example 9:

[0077] (1) Add 1.0g polyvinylidene fluoride, 1mg photoinitiator benzophenone and 100mg silsesquioxane to a 20ml serum bottle, add 15.00mL of dimethylacetamide:acetone (4:6) mixed solvent, stir thoroughly in the dark for 2h and let stand to remove bubbles to obtain a spinning solution with a concentration of 10wt.%; add 136mg Cu(NO3)2·3H2O and 102mg 2-aminoterephthalic acid to a 20ml serum bottle, add 15ml DMF and sonicate until completely dissolved, add 5mg cerium nitrate to obtain MOF precursor reaction solution;

[0078] (2) The spinning solution obtained in step (1) is added to a 20mL dispensing syringe and clamped into the electrospinning equipment. The distance between the nozzle and the receiving roller is adjusted to 12cm. The receiving roller of the electrospinning is wrapped with aluminum foil, the ultraviolet lamp is turned on, and the irradiation intensity is adjusted to 100-500mW / cm at the roller. 2 Simultaneously, turn on the spinning device of the spinning solution and adjust the spinning parameters as follows: spinning voltage 12kV, spinning solution feed rate 6mL / h; after the spinning solution is completely deposited on the aluminum foil, stop the electrospinning device, peel off the aluminum foil and immerse it in DCM for 30min, and change the solvent three times to remove ungrafted silsesquioxane, and then put it in an oven to dry the solvent to obtain an electrospun nanofiber membrane;

[0079] (3) The electrospun nanofiber membrane obtained in step (2) was placed in the MOF precursor reaction solution and transferred to a high-pressure reactor lined with polytetrafluoroethylene. The reactor was then placed in an oven at 110°C and reacted for 24 hours. After the reaction was completed, the fiber membrane was removed and repeatedly washed with anhydrous DMF and anhydrous ethanol and dried to finally obtain the MOF-modified hybrid composite electrospun nanofiber membrane.

[0080] (4) Using MOF-modified hybrid composite electrospun nanofiber membrane as separator, LFP as positive electrode and lithium metal sheet as negative electrode, CR2032 half cell was assembled in glove box. At the same time, commercial Celgard separator was used as a control and assembled into half cell. After standing for 24 hours, the rate performance and cycle performance of the battery were tested. The test results are shown in Table 1.

[0081] Example 10:

[0082] (1) Add 1.0g polyvinylidene fluoride, 1mg photoinitiator benzophenone and 100mg silsesquioxane to a 20ml serum bottle, add 15.00mL of dimethylacetamide:acetone (4:6) mixed solvent, stir thoroughly in the dark for 2h and let stand to remove bubbles to obtain a spinning solution with a concentration of 10wt.%; add 85mg Cu(NO3)2·3H2O and 64mg 2-aminoterephthalic acid to a 20ml serum bottle, add 15ml DMF and sonicate until completely dissolved, add 5mg cerium nitrate to obtain MOF precursor reaction solution;

[0083] (2) The spinning solution obtained in step (1) is added to a 20mL dispensing syringe and clamped into the electrospinning equipment. The distance between the nozzle and the receiving roller is adjusted to 15cm. The receiving roller of the electrospinning is wrapped with aluminum foil, the ultraviolet lamp is turned on, and the irradiation intensity is adjusted to 100-500mW / cm at the roller. 2 Simultaneously, turn on the spinning device of the spinning solution and adjust the spinning parameters as follows: spinning voltage 18kV, spinning solution feed rate 4mL / h; after the spinning solution is completely deposited on the aluminum foil, stop the electrospinning device, peel off the aluminum foil and immerse it in DCM for 30min, and change the solvent three times to remove ungrafted silsesquioxane, and then put it in an oven to dry the solvent to obtain an electrospun nanofiber membrane;

[0084] (3) The electrospun nanofiber membrane obtained in step (2) was placed in the MOF precursor reaction solution and transferred to a high-pressure reactor lined with polytetrafluoroethylene. The reactor was then placed in an oven at 110°C and reacted for 24 hours. After the reaction was completed, the fiber membrane was removed and repeatedly washed with anhydrous DMF and anhydrous ethanol and dried to finally obtain the MOF-modified hybrid composite electrospun nanofiber membrane.

[0085] (4) Using MOF-modified hybrid composite electrospun nanofiber membrane as separator, LFP as positive electrode and lithium metal sheet as negative electrode, CR2032 half cell was assembled in glove box. At the same time, commercial Celgard separator was used as a control and assembled into half cell. After standing for 24 hours, the rate performance and cycle performance of the battery were tested. The test results are shown in Table 1.

[0086] Example 11:

[0087] (1) Add 1.0g polyvinylidene fluoride, 1mg photoinitiator benzophenone and 120mg silsesquioxane to a 20ml serum bottle, add 15.00mL of dimethylacetamide:acetone (4:6) mixed solvent, stir thoroughly in the dark for 2h and let stand to remove bubbles to obtain a spinning solution with a concentration of 10wt.%; add 136mg Cu(NO3)2·3H2O and 102mg 2-aminoterephthalic acid to a 20ml serum bottle, add 18ml DMF and sonicate until completely dissolved, add 5mg cerium nitrate to obtain MOF precursor reaction solution;

[0088] (2) The spinning solution obtained in step (1) is added to a 20mL dispensing syringe and clamped into the electrospinning equipment. The distance between the nozzle and the receiving roller is adjusted to 10cm. The receiving roller of the electrospinning is wrapped with aluminum foil, the ultraviolet lamp is turned on, and the irradiation intensity is adjusted to 100-500mW / cm at the roller. 2Simultaneously, turn on the spinning device of the spinning solution and adjust the spinning parameters as follows: spinning voltage 15kV, spinning solution feed rate 4mL / h; after the spinning solution is completely deposited on the aluminum foil, stop the electrospinning device, peel off the aluminum foil and immerse it in DCM for 30min, and change the solvent three times to remove ungrafted silsesquioxane, and then put it in an oven to dry the solvent to obtain an electrospun nanofiber membrane;

[0089] (3) The electrospun nanofiber membrane obtained in step (2) was placed in the MOF precursor reaction solution and transferred to a high-pressure reactor lined with polytetrafluoroethylene. The reactor was then placed in an oven at 110°C and reacted for 24 hours. After the reaction was completed, the fiber membrane was removed and repeatedly washed with anhydrous DMF and anhydrous ethanol and dried to finally obtain the MOF-modified hybrid composite electrospun nanofiber membrane.

[0090] (4) Using MOF-modified hybrid composite electrospun nanofiber membrane as separator, LFP as positive electrode and lithium metal sheet as negative electrode, CR2032 half cell was assembled in glove box. At the same time, commercial Celgard separator was used as a control and assembled into half cell. After standing for 24 hours, the rate performance and cycle performance of the battery were tested. The test results are shown in Table 1.

[0091] Example 12:

[0092] (1) Add 1.0g polyvinylidene fluoride, 1mg photoinitiator benzophenone and 120mg silsesquioxane to a 20ml serum bottle, add 15.00mL of dimethylacetamide:acetone (4:6) mixed solvent, stir thoroughly in the dark for 2h and let stand to remove bubbles to obtain a spinning solution with a concentration of 10wt.%; add 68mg Cu(NO3)2·3H2O and 52mg 2-aminoterephthalic acid to a 20ml serum bottle, add 10ml DMF and sonicate until completely dissolved, add 5mg cerium nitrate to obtain MOF precursor reaction solution;

[0093] (2) The spinning solution obtained in step (1) is added to a 20mL dispensing syringe and clamped to the electrospinning device. The distance between the nozzle and the receiving roller is adjusted to 10cm. The receiving roller of the electrospinning device is wrapped with aluminum foil. The ultraviolet lamp is turned on and the irradiation intensity is adjusted to 100-500mW / cm2 at the roller. At the same time, the spinning device of the spinning solution is turned on and the spinning parameters are adjusted as follows: spinning voltage 22kV, spinning solution feed rate 6mL / h; after the spinning solution is completely deposited on the aluminum foil, the electrospinning device is stopped, the aluminum foil is peeled off and immersed in DCM for 30min, and the solvent is changed three times to remove the ungrafted silsesquioxane. Then, the solvent is dried in an oven to obtain an electrospun nanofiber membrane.

[0094] (3) The electrospun nanofiber membrane obtained in step (2) was placed in the MOF precursor reaction solution and transferred to a high-pressure reactor lined with polytetrafluoroethylene. The reactor was then placed in an oven at 110°C and reacted for 24 hours. After the reaction was completed, the fiber membrane was removed and repeatedly washed with anhydrous DMF and anhydrous ethanol and dried to finally obtain the MOF-modified hybrid composite electrospun nanofiber membrane.

[0095] (4) Using MOF-modified hybrid composite electrospun nanofiber membrane as separator, LFP as positive electrode and lithium metal sheet as negative electrode, CR2032 half cell was assembled in glove box. At the same time, commercial Celgard separator was used as a control and assembled into half cell. After standing for 24 hours, the rate performance and cycle performance of the battery were tested. The test results are shown in Table 1.

[0096] Table 1: Comparison of electrochemical data between Examples 1-12 and commercial Celgard membranes

[0097]

[0098]

[0099] As shown in Table 1, this application achieves significantly improved rate performance and cycle performance compared to the commercial Celgard separator. In particular, the battery capacity retention rate is over 99.6% after 50 cycles. Furthermore, its rate performance surpasses the commercial Celgard separator in all aspects at 0.2C, 0.5C, 1C, 2C, and 4C. The battery specific capacity is over 156 mAh / g at 0.2C; over 149 mAh / g at 0.5C; over 140 mAh / g at 1C; over 125 mAh / g at 2C; and over 99 mAh / g at 4C.

[0100] Therefore, this application, based on the principle of in-situ grafting modification of silsesquioxanes, utilizes the residual functional groups on the grafted silsesquioxanes to react with the functional groups of organic ligands in MOFs, enabling successful grafting of MOFs onto nanofiber membranes. This allows for the controlled fabrication of nanofiber membranes with reinforced structures, while also possessing a multi-level pore structure for effective control of the movement of positive and negative ions in lithium-ion batteries, enhancing lithium-ion throughput, and improving the electrochemical performance of lithium-ion batteries. Its rate performance and cycle performance are significantly improved compared to commercial polyolefin separators. Furthermore, the introduction of silsesquioxanes and MOF structures not only enhances the... The mechanical properties, thermal stability, and flame retardant properties of the electrospun nanofiber membrane also endow the assembled battery with excellent electrochemical and safety performance. Both CSQ and MOF used in this invention are prepared in the laboratory with well-defined structures. The chemical structure, mechanical, and electrochemical properties of the prepared electrospun nanofiber membrane are controllable, ensuring the controllability and precision of the preparation method. This invention is simple to implement and can be carried out under normal conditions, offering high safety and convenient post-processing. Lithium batteries assembled using the nanofiber separator of this invention exhibit excellent electrochemical performance, lifespan, and safety.

[0101] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing an electrospun hybrid nanofiber membrane, characterized in that, Includes the following steps: (1) Preparation of spinning solution: Polyvinylidene fluoride, photoinitiator benzophenone and silsesquioxane are dissolved in a mixed solution of dimethylacetamide and acetone with a volume ratio of 4:

6. After stirring thoroughly for 2 h under light-protected conditions, the solution is allowed to stand to remove bubbles and obtain the spinning solution. (2) Preparation of MOF precursor reaction solution: In a mixed solution of Cu(NO3)2·3H2O and 2-aminoterephthalic acid, N,N-dimethylformamide was added and ultrasonically vibrated until completely dissolved. Ceramide nitrate was added to obtain MOF precursor reaction solution. (3) Preparation of nanofiber membrane: Under ultraviolet light, the spinning solution obtained in step (1) is added to a syringe, and electrospinning is performed under appropriate voltage and feed rate. The spun membrane is collected and then post-processed to obtain silsesquioxane in-situ grafted modified nanofiber membrane. (4) Preparation of electrospun nanofiber membrane: The nanofiber membrane in step (3) is placed in the MOF precursor solution obtained in step (2) and reacted in a high-pressure reactor at 110 °C for 24 h. After the reaction is completed, the fiber membrane is repeatedly washed and dried to obtain the final product.

2. The method for preparing the electrospun hybrid nanofiber membrane according to claim 1, characterized in that: In step (1), the amount of polyvinylidene fluoride added is 1g, the amount of benzophenone added is 1mg, and the amount of the mixed solvent of dimethylacetamide and acetone added is 15mL.

3. The method for preparing the electrospun hybrid nanofiber membrane according to claim 1, characterized in that: In step (1), the amount of silsesquioxane added is 6 to 12 wt. of the mass of polyvinylidene fluoride.

4. The method for preparing the electrospun hybrid nanofiber membrane according to claim 1, characterized in that: In step (2), the molar ratio of Cu(NO3)2·3H2O and 2-aminoterephthalic acid is 1:

1.

5. The method for preparing the electrospun hybrid nanofiber membrane according to claim 1, characterized in that: In step (2), the amount of cerium nitrate added is 5 mg; the amount of MOF precursor added is 0-200 wt. of sesquioxane.

6. The method for preparing the electrospun hybrid nanofiber membrane according to claim 1, characterized in that: In step (3), the intensity of the ultraviolet light irradiation is 100–500 mW / cm². 2 The distance from the nozzle to the receiving roller is 10-15cm.

7. The method for preparing the electrospun hybrid nanofiber membrane according to claim 1, characterized in that: In step (3), the voltage of electrospinning is 12-22 kV and the feed rate is 2-6 mL / h.

8. The method for preparing the electrospun hybrid nanofiber membrane according to claim 1, characterized in that: In step (3), the post-treatment method of the spun film is as follows: the spun film is fully immersed in dichloromethane and ultrasonically washed for 30 minutes, repeated more than three times, and then placed in an oven to dry overnight.

9. The method for preparing the electrospun hybrid nanofiber membrane according to claim 1, characterized in that: In step (4), the solvents used in the washing process are anhydrous N,N-dimethylformamide and anhydrous ethanol.

10. The application of the electrospun hybrid nanofiber separator prepared by the preparation method according to any one of claims 1-9 in high-performance lithium metal batteries.

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