Core-shell hierarchical nano-array coated separator and preparation method therefor

Abstract

A core-shell hierarchical nano-array coated separator and a preparation method therefor. The separator comprises a base membrane, a core-shell hierarchical nano-array layer and a binder, wherein the core-shell hierarchical nano-array layer is fixed on the upper end face of the base membrane by means of the binder; and the core-shell hierarchical nano-array layer is in a core-shell hierarchical nano-array form formed with inorganic ceramic particles as a core and a boehmite nano-array as a shell. The core-shell hierarchical nano-array coated separator and the preparation method thereof aim to solve the problems of poor heat resistance and porosity performance of coated separators for lithium batteries.

Description

A core-shell hierarchical nanoarray coated membrane and its preparation method Technical Field

[0001] This invention relates to the field of lithium battery separator technology, specifically to a core-shell hierarchical nanoarray coated separator and its preparation method. Background Technology

[0002] Lithium-ion batteries are hailed as one of the most reliable technologies for solving the energy crisis and alleviating environmental pressure. However, with the expansion of lithium-ion battery applications, the shortcomings of current lithium-ion battery technology have gradually become apparent. Many researchers have begun to optimize lithium-ion batteries by focusing on battery structure. The separator is a crucial part of the battery structure, primarily providing "isolation" and "transmission" functions, and plays a pivotal role in ensuring battery safety. Currently, polyolefin separators such as polyethylene (PE), polypropylene (PP), and PP / PE / PP three-layer separators are widely used in commercial lithium batteries due to their excellent mechanical properties, excellent electrochemical stability, and suitable shut-off temperatures. However, the poor wettability and poor thermal dimensional stability of polyolefin separators to polar liquid electrolytes severely affect the safety performance of lithium batteries at high temperatures.

[0003] Currently, due to the thermal stability, chemical stability, and wettability of inorganic materials, and the mature preparation process of their dispersion slurries, the coating modification of diaphragms with inorganic dispersion slurries is a hot research topic in diaphragm modification. Among them, inorganic ceramics such as Al2O3, ZrO2, and SiO2 have attracted widespread attention due to their advantages of low price and high wettability, making them ideal diaphragm modification materials. Polymers such as polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), and polymethyl methacrylate (PMMA) are typically used as binders for coating diaphragms with inorganic ceramic materials. However, coating modification methods face certain challenges: First, commonly used inorganic particles such as Al2O3 tend to increase the weight of the diaphragm due to their inherent properties; their high hardness can cause wear on coating machines and other mechanical equipment; and the stacking of relatively regular inorganic particles can further increase the diaphragm weight and hinder lithium-ion insertion and extraction. Furthermore, the accumulation of various adhesives is often overlooked, hindering electrolyte penetration. Therefore, designing and developing membrane coatings that combine high heat resistance and high porosity is an urgent problem to be solved in lithium battery coating membranes.

[0004] Therefore, the inventors provide a core-shell hierarchical nanoarray coated diaphragm and its preparation method. Summary of the Invention

[0005] (1) Technical problems to be solved

[0006] This invention provides a core-shell hierarchical nanoarray coated separator and its preparation method, which solves the technical problem of low heat resistance and porosity performance of lithium battery coated separators.

[0007] (2) Technical solution

[0008] The first aspect of the present invention provides a core-shell hierarchical nanoarray coating membrane, comprising a base film, a core-shell hierarchical nanoarray layer and an adhesive, wherein the core-shell hierarchical nanoarray layer is fixed to the upper end face of the base film by the adhesive, and the core-shell hierarchical nanoarray layer is a core-shell hierarchical nanoarray morphology composed of inorganic ceramic particles as the core and boehmite nanoarrays as the shell.

[0009] Furthermore, the binder is in a high-porosity, non-agglomerated form.

[0010] Furthermore, the inorganic ceramic particles are any one of Al2O3, ZrO2, SiO2, TiO2, and ZnO2.

[0011] Furthermore, the particle size of the inorganic ceramic particles is 100–150 nm.

[0012] Furthermore, the adhesive is at least one selected from polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, perfluoropropylene, and polychlorotrifluoroethylene.

[0013] A second aspect of the present invention provides a method for preparing a core-shell hierarchical nanoarray coated membrane, comprising the following steps:

[0014] Inorganic ceramic particles are ground into spherical shapes using a ball mill.

[0015] Surface modification of spherical inorganic ceramic particles;

[0016] Using surface-modified inorganic ceramic particles as the core, boehm nanoarrays were constructed on their surface to obtain core-shell hierarchical nanoarray inorganic ceramic materials.

[0017] Weigh out the core-shell hierarchical nanoarray inorganic ceramic material, binder, salt, deionized water and solvent in proportion, mix them, and disperse them evenly to obtain a coating liquid;

[0018] The coating liquid is applied to the base film, and then subjected to freezing, freeze-drying, deionized water immersion and room temperature drying treatment in sequence to obtain the coated diaphragm.

[0019] Furthermore, the surface modification of the spherical inorganic ceramic particles specifically involves:

[0020] The polished inorganic ceramic particles were continuously stirred in an acetone solution, and then repeatedly washed and dried with deionized water.

[0021] Furthermore, the step of constructing a boehmite nanoarray on the surface of surface-modified inorganic ceramic particles to obtain a core-shell hierarchical nanoarray inorganic ceramic material specifically includes the following steps:

[0022] Emulsion A was obtained by ultrasonic dissolution of inorganic ceramic particles, DL-aspartic acid, and water in a mass ratio of 1.5:1:1.

[0023] Prepare solution B according to the molar ratio of PEG4000 to aluminum nitrate of 5:1;

[0024] Prepare solution C according to the molar ratio of urea to aluminum nitrate of 50:1;

[0025] Add solution B to emulsion A and stir continuously, then add solution C and stir to obtain a mixed solution;

[0026] The mixed solution is transferred to a reflux device and heated from room temperature at a set heating rate until boiling under stirring conditions. The system is kept boiling for a preset time and then heating is stopped.

[0027] After naturally cooling to room temperature, the precipitate is heated to separate it. The precipitate is collected by centrifugation with deionized water and ethanol in sequence and washed repeatedly. Finally, it is dried under vacuum to obtain the core-shell hierarchical nanoarray inorganic ceramic material.

[0028] Furthermore, the volume ratio of the emulsion A:the solution B:the solution C is 9:10:1.

[0029] Further, the steps of weighing the core-shell hierarchical nanoarray inorganic ceramic material, binder, salt, deionized water, and solvent in proportion, mixing them, and dispersing them evenly to obtain a coating solution specifically include the following steps:

[0030] Weigh out the inorganic ceramic material, binder, salt, and deionized water in a weight ratio of 8:1:1:1 and set aside for use.

[0031] The binder was dissolved in N,N-dimethylformamide, and then subjected to high-speed stirring and continuous sonication to form a clear solution.

[0032] The inorganic ceramic material, the salt, and the deionized water are continuously ground, and then the clarified solution is added while continuously stirring to form the coating solution.

[0033] (3) Beneficial effects

[0034] In summary, this invention, by setting an array of nanoscale boehmite on the outer surface of inorganic ceramic particles, ensures that the surface hardness of the shell-shaped boehmite does not easily cause wear on the coating machinery, thus extending the service life of the equipment. The core-shell nanoarray inorganic ceramic material is not prone to stacking and agglomeration, thereby indirectly reducing the weight of the separator, which helps to accelerate electrolyte penetration and lithium ion transport, improve the wettability, porosity and lithium ion penetration ability of the coated separator, and further improve the safety and stability of the lithium battery. Attached Figure Description

[0035] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 is a schematic flowchart of a method for preparing a core-shell hierarchical nanoarray coated membrane according to an embodiment of the present invention;

[0037] Figure 2 is a schematic diagram of a high heat resistance and high porosity coated membrane provided in an embodiment of the present invention.

[0038] Figure 3 is a micron-scale SEM image of a core-shell nanoarray Al2O3@AlOOH inorganic ceramic material provided in Embodiment 1 of the present invention;

[0039] Figure 4 is a nanoscale SEM image of a core-shell nanoarray Al2O3@AlOOH inorganic ceramic material provided in Embodiment 1 of the present invention.

[0040] In the figure: 1-base film; 2-core-shell hierarchical nanoarray layer; 3-binder. Detailed Implementation

[0041] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. The following detailed description of the embodiments and the accompanying drawings are used to illustrate the principles of the present invention by way of example, but should not be used to limit the scope of the present invention, that is, the present invention is not limited to the described embodiments.

[0042] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0043] Figure 1 is a schematic diagram of the structure of a core-shell hierarchical nanoarray coating membrane provided in an embodiment of the present invention. As shown in Figure 1, the membrane may include a base membrane 1, a core-shell hierarchical nanoarray layer 2 and an adhesive 3. The core-shell hierarchical nanoarray layer 2 is fixed to the upper end face of the base membrane 1 by the adhesive 3. The core-shell hierarchical nanoarray layer 2 is a core-shell hierarchical nanoarray with inorganic ceramic particles as the core and boehmite nanoarray as the shell.

[0044] In the above embodiments, by setting an array of nanoscale boehmite on the outer surface of the inorganic ceramic particle material, the surface hardness of the shell-shaped boehmite will not easily cause wear on the coating machinery, which can extend the service life of the machinery. The core-shell nano-array inorganic ceramic material is not easy to stack and agglomerate, which indirectly reduces the weight of the separator, helps to accelerate electrolyte penetration and lithium ion transport, improves the wettability, porosity and lithium ion penetration ability of the coated separator, and further improves the safety and stability of the lithium battery.

[0045] The base membrane 1 is made of polyethylene (PE), polypropylene (PP), or a PP / PE / PP three-layer membrane. The core-shell hierarchical nanoarray layer 2 has a structure similar to that of a sea urchin, with spherical inorganic ceramic particles and nanoscale boehmite arrays distributed on the surface of the spheres. The binder 3 is a high-porosity, non-agglomerated form (i.e., a porous binder), which further enhances the high porosity of the binder 3 to accelerate electrolyte penetration. Specifically, the binder 3 can be at least one of polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, perfluoropropylene, and polychlorotrifluoroethylene.

[0046] As an optional implementation, the inorganic ceramic particles are any one of Al2O3, ZrO2, SiO2, TiO2, and ZnO2, and the particle size of the inorganic ceramic particles is 100–150 nm. The inorganic ceramic particles only need to meet the requirements of inorganic nanoparticles; no specific limitations are imposed.

[0047] Figure 2 is a schematic flowchart of a method for preparing a core-shell hierarchical nanoarray coated membrane according to an embodiment of the present invention. As shown in Figure 2, the method may include the following steps:

[0048] S100. Use a ball mill to grind inorganic ceramic particles into spherical shapes;

[0049] S200, surface modification of spherical inorganic ceramic particles;

[0050] S300: Using surface-modified inorganic ceramic particles as the core, a boehm nanoarray is constructed on its surface to obtain a core-shell hierarchical nanoarray inorganic ceramic material.

[0051] S400: Weigh out the core-shell hierarchical nano-array inorganic ceramic material, binder, salt, deionized water and solvent according to the proportion, mix them, and disperse them evenly to obtain the coating liquid;

[0052] S500: The coating solution is applied to the base membrane, and then subjected to freezing, freeze-drying, deionized water immersion and room temperature drying treatment in sequence to obtain the coated diaphragm.

[0053] In the above embodiment, in step S200, the surface modification of the spherical inorganic ceramic particles is specifically carried out by continuously stirring the polished inorganic ceramic particles in an acetone solution, and repeatedly washing and drying them with deionized water.

[0054] In step S300, using the surface-modified inorganic ceramic particles as the core, a boehmite (AlOOH) nanoarray is constructed on its surface to obtain a core-shell hierarchical nanoarray inorganic ceramic material. This specifically includes the following steps:

[0055] S301. Emulsion A is obtained by ultrasonic dissolution of inorganic ceramic particles, DL-aspartic acid, and water in a mass ratio of 1.5:1:1.

[0056] S302. Prepare solution B according to the molar ratio of PEG4000 to aluminum nitrate of 5:1.

[0057] S303. Prepare solution C according to the molar ratio of urea to aluminum nitrate of 50:1;

[0058] S304. Add solution B to emulsion A and stir continuously, then add solution C and stir to obtain a mixed solution;

[0059] S305. Transfer the mixed solution to a reflux device and heat it from room temperature at a set heating rate until boiling under stirring conditions. Maintain the boiling of the system for a preset time and then stop heating.

[0060] S306. After naturally cooling to room temperature, the precipitate is separated by heating. The precipitate is collected by centrifugation with deionized water and ethanol in sequence and washed repeatedly. Finally, it is dried under vacuum to obtain a core-shell hierarchical nanoarray inorganic ceramic material.

[0061] As an optional implementation, the volume ratio of emulsion A: solution B: solution C is 9:10:1. This volume ratio ensures that the prepared mixed solution can be subjected to subsequent heating, cooling, separation, washing, and drying processes to obtain the corresponding core-shell hierarchical nanoarray inorganic ceramic material.

[0062] In step S400, the core-shell hierarchical nanoarray inorganic ceramic material, binder, salt, deionized water, and solvent are weighed out in proportion and mixed. After being evenly dispersed, a coating liquid is obtained. The specific steps include the following:

[0063] S401. Weigh out the inorganic ceramic material, binder, salt, and deionized water in a weight ratio of 8:1:1:1 and set aside for use.

[0064] S402. Dissolve the binder in N,N-dimethylformamide, and then stir at high speed and sonicate continuously to form a clear solution.

[0065] S403. Inorganic ceramic material, salt and deionized water are continuously ground, then a clear solution is added and continuously stirred to form a coating solution.

[0066] Specifically, brine is introduced into the coated diaphragm as a pore-forming agent and a separating factor between inorganic ceramic materials, with brine molecules and water ice crystals as sacrificial templates, to prepare a diaphragm coating with high heat resistance and high porosity.

[0067] Example 1

[0068] Preparation of Al2O3@AlOOH inorganic ceramic materials:

[0069] (1) Al2O3 inorganic ceramic particles were ground into spherical shape using a ball mill. The particle diameter after grinding was about 100-150 nm.

[0070] (2) Surface modification of the obtained inorganic ceramic particles: First, the polished Al2O3 inorganic ceramic particles are continuously stirred in acetone solution, and then repeatedly washed and dried with deionized water.

[0071] (3) The pretreated Al2O3 particles: DL-aspartic acid: water were ultrasonically dissolved in a mass ratio of 1.5:1:1 to obtain emulsion A; PEG4000 aqueous solution B was prepared in a molar ratio of 5:1; urea: aluminum nitrate aqueous solution C was prepared in a molar ratio of 50:1; wherein the volume ratio of deionized water to emulsion A: solution B: solution C was 9:10:1.

[0072] (4) Slowly add solution B to the obtained emulsion A and stir continuously for 1 hour. Then, continue to slowly add solution C and stir to obtain a mixed solution.

[0073] (5) The obtained mixed solution was transferred to a reflux device and heated slowly from room temperature at a heating rate of 5°C per minute until boiling under slow stirring. The system was kept boiling for a period of time and then the heating was stopped. After naturally cooling to room temperature, the precipitate was separated by heating. The precipitate was collected by centrifugation with deionized water and ethanol in sequence and washed repeatedly three times. Finally, it was vacuum dried at 60°C to obtain the core-shell hierarchical nanoarray structure of Al2O3@AlOOH inorganic ceramic material as shown in Figure 3-4.

[0074] Preparation of high heat-resistant, high-porosity coated membranes:

[0075] (6) Weigh out the inorganic ceramic materials Al2O3@AlOOH according to the weight ratio of PVDF / PAN / PMMA / PFA / FEP: salt: deionized water in 8:1:1:1 and set aside for use;

[0076] (7) Dissolve PVDF / PAN / PMMA / PFA / FEP in an appropriate amount of DMF, and stir and sonicate continuously at high speed to form a clear solution;

[0077] (8) Grind Al2O3@AlOOH inorganic ceramic material, salt and deionized water for 1 hour, then slowly add the clear solution and continue stirring to form a film-forming emulsion with relatively uniform composition. After degassing, it is ready for use.

[0078] (9) Apply the emulsion to one or both sides of the base film and freeze immediately, then freeze dry. The base film used is PE, PP or PP / PE / PP etc.

[0079] (10) The freeze-dried coated membrane was immersed in deionized water for several hours, repeated three times, to remove the precipitated salt crystals, and then dried to obtain the high heat resistance and high porosity coated membrane Example 1.

[0080] Example 2

[0081] Preparation of Al2O3@AlOOH inorganic ceramic materials:

[0082] The specific process is consistent with the proportioning and preparation process of Al2O3@AlOOH inorganic ceramic material in Example 1;

[0083] Preparation of high heat-resistant, high-porosity coated membranes:

[0084] (1) Weigh out the Al2O3@AlOOH inorganic ceramic material according to the weight ratio of Al2O3:PAN:table salt:deionized water as 7:2:1:1 and set aside for use;

[0085] (2) Dissolve PAN in an appropriate amount of DMF, and then stir at high speed and sonicate continuously to form a clear solution;

[0086] (3) Add Al2O3@AlOOH inorganic ceramic material, salt and deionized water to a clear solution and stir continuously to form a film-forming emulsion with relatively uniform composition. After degassing, it is ready for use.

[0087] (4) Apply the emulsion to one or both sides of the base film and freeze it immediately, then freeze-dry it. The base film used is PE, PP or PP / PE / PP etc.

[0088] (5) Immerse the freeze-dried coated membrane in deionized water for several hours, repeating the process three times to remove the precipitated salt crystals, and then dry it to obtain the high heat resistance and high porosity coated membrane Example 2.

[0089] Example 3

[0090] Preparation of Al2O3@AlOOH inorganic ceramic materials:

[0091] The specific process is consistent with the proportioning and preparation process of Al2O3@AlOOH inorganic ceramic material in Example 1;

[0092] Preparation of high heat-resistant, high-porosity coated membranes:

[0093] (1) Weigh out the inorganic ceramic material Al2O3@AlOOH according to the weight ratio of PVDF:PFA:FEP:salt:deionized water as 7:1.5:1:1:1:1 and set aside for use;

[0094] (2) Dissolve PVDF, PFA and FEP in an appropriate amount of DMF, and stir and sonicate at high speed in sequence to form a clear solution;

[0095] (3) Add Al2O3@AlOOH inorganic ceramic material, salt and deionized water to a clear solution and stir continuously to form a film-forming emulsion with relatively uniform composition. After degassing, it is ready for use.

[0096] (4) Apply the emulsion to one or both sides of the base film and freeze it immediately, then freeze-dry it. The base film used is PE, PP or PP / PE / PP etc.

[0097] (5) The freeze-dried coated membrane was immersed in deionized water for several hours, repeated three times, to remove the precipitated salt crystals, and then dried to obtain the high heat resistance and high porosity coated membrane Example 3.

[0098] Example 4

[0099] Preparation of ZrO2@AlOOH inorganic ceramic materials:

[0100] (1) ZrO2 inorganic ceramic particles were ground into spherical shape using a ball mill. The particle diameter after grinding was about 100-150 nm.

[0101] (2) Surface modification of the obtained inorganic ceramic particles: First, the polished ZrO2 inorganic ceramic particles are continuously stirred in acetone solution, and then repeatedly washed and dried with deionized water.

[0102] (3) The pretreated ZrO2 particles: DL-aspartic acid: water were ultrasonically dissolved in a mass ratio of 1.5:1:1 to obtain emulsion A; PEG4000 aqueous solution B was prepared in a molar ratio of 5:1; urea: aluminum nitrate aqueous solution C was prepared in a molar ratio of 50:1; wherein the volume ratio of deionized water to emulsion A: solution B: solution C was 9:10:1.

[0103] (4) Slowly add solution B to the obtained emulsion A and stir continuously for 1 hour. Then, continue to slowly add solution C and stir to obtain a mixed solution.

[0104] (5) The obtained mixed solution was transferred to a reflux device and heated slowly from room temperature at a rate of 5°C per minute until boiling under slow stirring. The system was kept boiling for a period of time and then the heating was stopped. After naturally cooling to room temperature, the precipitate was separated by heating. The precipitate was collected by centrifugation with deionized water and ethanol in sequence and washed repeatedly three times. Finally, it was vacuum dried at 60°C to obtain the ZrO2@AlOOH inorganic ceramic material with a core-shell hierarchical nanoarray structure.

[0105] Preparation of high heat-resistant, high-porosity coated membranes:

[0106] (6) Weigh out the ZrO2@AlOOH inorganic ceramic material according to the weight ratio of PVDF / PAN / PMMA / PFA / FEP: salt: deionized water in 8:1:1:1 and set aside for use;

[0107] (7) Dissolve PVDF / PAN / PMMA / PFA / FEP in an appropriate amount of DMF, and stir and sonicate continuously at high speed to form a clear solution;

[0108] (8) ZrO2@AlOOH inorganic ceramic material, salt and deionized water are continuously ground for 1 hour, then a clear solution is slowly added and continuously stirred to form a film-forming emulsion with relatively uniform composition. After degassing, it is ready for use.

[0109] (9) Apply the emulsion to one or both sides of the base film and freeze immediately, then freeze dry. The base film used is PE, PP or PP / PE / PP etc.

[0110] (10) The freeze-dried coated membrane was immersed in deionized water for several hours, repeated three times, to remove the precipitated salt crystals, and then dried to obtain the high heat resistance and high porosity coated membrane Example 4.

[0111] Example 5

[0112] By replacing the core particles in Example 1 with SiO2 particles, and keeping the other steps the same, the high heat-resistant, high porosity coated membrane Example 5 was obtained.

[0113] Example 6

[0114] By replacing the core particles in Example 1 with TiO2 particles, and keeping the other steps the same, the high heat-resistant, high porosity coated membrane Example 6 was obtained.

[0115] Example 7

[0116] By replacing the core particles in Example 7 with ZnO2 particles, and keeping the other steps the same, the high heat-resistant, high porosity coated membrane Example 7 was obtained.

[0117] Example 8

[0118] (1) Weigh out Al2O3@AlOOH:ZrO2@AlOOH:PVDF / PAN / PMMA / PFA / FEP:salt:deionized water in a weight ratio of 4:4:1:1:1 and set aside. Al2O3@AlOOH and ZrO2@AlOOH are the Al2O3@AlOOH inorganic ceramic materials in Example 1 and ZrO2@AlOOH inorganic ceramic materials in Example 2, respectively.

[0119] (2) Dissolve PVDF in an appropriate amount of DMF, and then stir and sonicate at high speed in sequence to form a clear solution;

[0120] (3) Grind the inorganic ceramic material, salt and deionized water for 1 hour, then slowly add the (2) clear solution and continue stirring to form a film-forming emulsion with relatively uniform composition. After degassing, it is ready for use.

[0121] (4) Apply the emulsion to one or both sides of the base film and freeze immediately, followed by freeze drying. The base film used is PE, PP, or PP / PE / PP, etc.

[0122] (5) The freeze-dried coated membrane was immersed in deionized water for several hours, repeated three times, to remove the precipitated salt crystals, and then dried to obtain the high heat resistance and high porosity coated membrane Example 8.

[0123] Example 9

[0124] Preparation of AlOOH inorganic ceramic materials:

[0125] (1) Degrease a high-purity 0.2mm thick aluminum foil (30mm×20mm) in acetone for 15min, then rinse it with distilled water, immerse the aluminum foil in 1mol / L NaOH solution for 20min to remove the oxide layer, and wash it four times with distilled water.

[0126] (2) In a typical hydrothermal process, 20g of urea and 0.4g of NaOH were dissolved in 100mL of distilled water to obtain a transparent solution. 60mL of the solution was transferred to a Teflon-lined stainless steel autoclave (100mL capacity). The cleaned aluminum foil was immersed in the solution. The autoclave was sealed and kept at 180℃ for 24 hours. Then it was naturally cooled to room temperature. After centrifugation, the product was washed three times with distilled water. The prepared sample was dried in air at 80℃ for 6 hours to prepare AlOOH inorganic ceramic material.

[0127] Preparation of high heat-resistant, high-porosity coated membranes:

[0128] The Al2O3@AlOOH inorganic ceramic particles in "Preparation of High Heat Resistance and High Porosity Coated Separator" in Example 1 were replaced with AlOOH inorganic ceramic materials, and the remaining steps were the same, to obtain the finished product 9 of the high heat resistance and high porosity coated separator example.

[0129] Comparative Example 1

[0130] (1) Weigh Al2O3 (Al2O3 is commercial ceramic particles with an average size of about 0.3 μm) and PVDF at a weight ratio of 8:1 and set aside. Then, dissolve PVDF in an appropriate amount of DMF and stir at high speed and sonicate continuously to form a clear solution. Next, grind Al2O3 continuously for 1 hour, then slowly add the clear solution and stir continuously to form a relatively uniform film-forming emulsion. After degassing, set aside for use.

[0131] (2) Apply the emulsion to one or both sides of the base film and freeze it immediately, then freeze-dry it. The base film used is PE, PP or PP / PE / PP etc.; then, immerse the cold-dried coated diaphragm in deionized water for several hours, repeat three times, and dry it to obtain the comparative product 1.

[0132] Comparative Example 2

[0133] Replace Al2O3 with ZrO2 in Comparative Example 1, while keeping the other materials and steps the same, to obtain Comparative Example 2.

[0134] Comparative Example 3

[0135] By replacing Al2O3 with SiO2 in Comparative Example 1, and keeping the other materials and steps the same, Comparative Example 3 was obtained.

[0136] Comparative Example 4

[0137] In Comparative Example 1, Al2O3 was replaced with TiO2, while the other materials and steps remained the same, resulting in Comparative Example 4.

[0138] Comparative Example 5

[0139] In Comparative Example 1, Al2O3 was replaced with ZnO2, while the other materials and steps remained the same, resulting in Comparative Example 5.

[0140] Product performance testing

[0141] The physicochemical properties of the high heat resistance and high porosity coated membranes prepared in Examples 1-9 and Comparative Examples 1-5 were determined:

[0142] (1) Porosity was determined using a mercury porosimeter, and the test standard was GB / T21650.2-2008;

[0143] (2) Air permeability test: Cut the prepared diaphragm into 3cm*3cm square pieces, put them into the test port of the Gurley tester, measure the air permeability time, and express it as the Gurley value;

[0144] (3) Heat shrinkage rate test: After the coated diaphragm is dried, a film sample of a certain size is cut out, its longitudinal length (MD1) is measured, and it is placed in a precision oven and baked at 120℃ for 2 hours. The diaphragm sample is taken out, cooled to room temperature, and its longitudinal length (MD2) is measured again. The heat shrinkage rate δ=(MD1-MD2) / MD1×100%.

[0145] (4) The tensile strength of the diaphragm was tested according to standard GB / T1040.3-2006;

[0146] (5) The thickness of the lithium battery separator was tested according to the national standard GB / T6672-2001;

[0147] (6) The water contact angle was tested according to the national standard GB / T 30693-2014.

[0148] The test results of the physicochemical properties of the high heat resistance and high porosity coated membranes prepared in Examples 1-9 and Comparative Examples 1-5 are shown in Table 1 below:

[0149] Table 1

[0150] As can be seen from the data in the table above, the core-shell hierarchical nanoarray membrane coating prepared by this invention has superior physicochemical properties such as porosity, heat resistance, and tensile strength.

[0151] It should be noted that the various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. The present invention is not limited to the specific steps and structures described above and shown in the figures. Furthermore, for the sake of brevity, detailed descriptions of known methods and techniques are omitted here.

[0152] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art without departing from the scope of the invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of this application should be included within the scope of the claims of this application.

Claims

1. A core-shell hierarchical nanoarray coated membrane, characterized in that, It includes a base film (1), a core-shell hierarchical nanoarray layer (2) and an adhesive (3). The core-shell hierarchical nanoarray layer (2) is fixed to the upper surface of the base film (1) by the adhesive (3). The core-shell hierarchical nanoarray layer (2) is a core-shell hierarchical nanoarray with inorganic ceramic particles as the core and boehm nanoarray as the shell.

2. The core-shell hierarchical nanoarray coating membrane according to claim 1, characterized in that, The adhesive (3) is a high-porosity, non-agglomerated form.

3. The core-shell hierarchical nanoarray coating membrane according to claim 1, characterized in that, The inorganic ceramic particles are any one of Al2O3, ZrO2, SiO2, TiO2 and ZnO2.

4. The core-shell hierarchical nanoarray coating membrane according to claim 1 or 3, characterized in that, The inorganic ceramic particles have a particle size of 100–150 nm.

5. The core-shell hierarchical nanoarray coating membrane according to claim 1, characterized in that, The adhesive (3) is at least one of polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, perfluoropropylene and polychlorotrifluoroethylene.

6. A method for preparing a core-shell hierarchical nanoarray coated membrane as described in any one of claims 1-5, characterized in that, The method includes the following steps: Inorganic ceramic particles are ground into spherical shapes using a ball mill. Surface modification of spherical inorganic ceramic particles; Using surface-modified inorganic ceramic particles as the core, boehm nanoarrays were constructed on their surface to obtain core-shell hierarchical nanoarray inorganic ceramic materials. Weigh out the core-shell hierarchical nanoarray inorganic ceramic material, binder, salt, deionized water and solvent in proportion, mix them, and disperse them evenly to obtain a coating liquid; The coating liquid is applied to the base film, and then subjected to freezing, freeze-drying, deionized water immersion and room temperature drying treatment in sequence to obtain the coated diaphragm.

7. The method for preparing a core-shell hierarchical nanoarray coated membrane according to claim 6, characterized in that, The surface modification of the spherical inorganic ceramic particles specifically involves: The polished inorganic ceramic particles were continuously stirred in an acetone solution, and then repeatedly washed and dried with deionized water.

8. The method for preparing a core-shell hierarchical nanoarray coated membrane according to claim 6, characterized in that, The process of constructing a boehmite nanoarray on the surface of surface-modified inorganic ceramic particles to obtain a core-shell hierarchical nanoarray inorganic ceramic material specifically includes the following steps: Emulsion A was obtained by ultrasonic dissolution of inorganic ceramic particles, DL-aspartic acid, and water in a mass ratio of 1.5:1:

1. Prepare solution B according to the molar ratio of PEG4000 to aluminum nitrate of 5:1; Prepare solution C according to the molar ratio of urea to aluminum nitrate of 50:1; Add solution B to emulsion A and stir continuously, then add solution C and stir to obtain a mixed solution; The mixed solution is transferred to a reflux device and heated from room temperature at a set heating rate until boiling under stirring conditions. The system is kept boiling for a preset time and then heating is stopped. After naturally cooling to room temperature, the precipitate is heated to separate it. The precipitate is collected by centrifugation with deionized water and ethanol in sequence and washed repeatedly. Finally, it is dried under vacuum to obtain the core-shell hierarchical nanoarray inorganic ceramic material.

9. The method for preparing a core-shell hierarchical nanoarray coated membrane according to claim 8, characterized in that, The volume ratio of emulsion A to solution B to solution C is 9:10:

1.

10. The method for preparing a core-shell hierarchical nanoarray coated membrane according to claim 6, characterized in that, The process of weighing the core-shell hierarchical nanoarray inorganic ceramic material, binder, salt, deionized water, and solvent in proportion, mixing them, and dispersing them evenly to obtain a coating solution specifically includes the following steps: Weigh out the inorganic ceramic material, binder, salt, and deionized water in a weight ratio of 8:1:1:1 and set aside for use. The binder was dissolved in N,N-dimethylformamide, and then subjected to high-speed stirring and continuous sonication to form a clear solution. The inorganic ceramic material, the salt, and the deionized water are continuously ground, then the clarified solution is added, and the mixture is continuously stirred to form the coating solution.

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