A diaphragm, a method for manufacturing the same, a battery, and an electric device

Abstract

The application provides a diaphragm and a preparation method thereof, a battery and an electric device. The diaphragm comprises an aerogel film layer, and the aerogel film layer comprises a high latent heat of phase change material in pores. The aerogel has high porosity, which optimizes the power performance of the battery. Meanwhile, due to the presence of the high latent heat of phase change material, the battery has higher specific heat capacity, and the high-temperature cycle life is therefore better.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a separator, a preparation method thereof, a battery and an electric device. BACKGROUND

[0002] As one of the components of a liquid lithium ion battery, the main function of the separator is to block the electron transmission between the positive and negative materials under the premise of ensuring the normal transmission of ions, thereby completing the charging and discharging process. Therefore, the power performance of the battery can be improved by increasing the porosity of the separator.

[0003] Common separators include polyethylene (PE) separators, polypropylene (PP) separators, etc., or a coating material is coated on the surface of the electrode sheet to replace the separator.

[0004] However, high temperature conditions often occur during the use of the battery. While ensuring the performance of the battery, the high temperature safety of the battery also needs to be ensured, so the high temperature resistance of the separator needs to be improved. SUMMARY

[0005] The present application provides a separator, a preparation method thereof, a battery and an electric device. An aerogel is used as a base material, and a high latent heat of phase change material is added in the pores thereof, so that the specific heat capacity of the separator is improved, and the high temperature safety performance of the battery is improved.

[0006] In a first aspect, the present application provides a separator, which comprises an aerogel film layer, and the pores of the aerogel film layer comprise a high latent heat of phase change material.

[0007] According to an embodiment of the present application, the thickness of the aerogel film layer is 8-15 μm.

[0008] According to an embodiment of the present application, the volume of the high latent heat of phase change material accounts for 10-48% of the pore volume of the aerogel film layer.

[0009] According to an embodiment of the present application, the pore size of the pores of the aerogel film layer is 100-230 nm.

[0010] According to an embodiment of the present application, the aerogel comprises at least one of a polyimide aerogel and a ceramic aerogel.

[0011] According to an embodiment of the present application, the ceramic aerogel comprises an organic silicon source aerogel.

[0012] According to an embodiment of the present application, the high latent heat of phase change material comprises at least one of paraffin, fatty acid or high latent heat of phase change salt material;

[0013] wherein the melting point of the paraffin is ≥50℃;

[0014] and / or, the carbon chain length of the fatty acid is ≥ 12;

[0015] and / or, the high latent heat of phase transition salt material comprises at least one of paraffin, fatty acid, and / or high latent heat of phase transition salt material.

[0016] According to an embodiment of the present application, the separator further comprises a coating layer, the coating layer is located on at least one side of the aerogel film layer.

[0017] The coating layer comprises at least one of polyvinylidene fluoride, acrylic resin, polyurethane resin, aluminum oxide, boehmite, magnesium hydroxide, and silicon oxide.

[0018] According to an embodiment of the present application, the thickness T of the coating layer is 0 < T ≤ 1 μm.

[0019] The second aspect of the present application provides a preparation method of the separator of the first aspect, the preparation method comprising the following steps:

[0020] mixing the initial aerogel film layer with a high latent heat of phase transition material to obtain the separator comprising the aerogel film layer;

[0021] or, mixing the mixed system for preparing aerogel with a high latent heat of phase transition material to obtain the separator comprising the aerogel film layer.

[0022] According to an embodiment of the present application, the high latent heat of phase transition material is paraffin and / or fatty acid, and the preparation method comprises:

[0023] immersing the initial aerogel film layer in a solution comprising the paraffin and / or the fatty acid to obtain the separator.

[0024] According to an embodiment of the present application, the high latent heat of phase transition material is a high latent heat of phase transition salt material, and the preparation method comprises:

[0025] mixing the high latent heat of phase transition salt material with the mixed system for preparing aerogel to obtain a mixture, and forming the mixture into the separator.

[0026] According to an embodiment of the present application, the preparation method further comprises:

[0027] providing a coating layer on at least one side of the initial aerogel film layer to obtain the separator.

[0028] The third aspect of the present application provides a battery, the battery comprising the separator of the first aspect or the separator prepared by the preparation method of the second aspect.

[0029] The fourth aspect of the present application provides an electrical equipment, the electrical equipment comprising the battery of the third aspect.

[0030] The application provides a diaphragm, a preparation method thereof, a battery and an electrical equipment. The diaphragm takes aerogel with high porosity and low density as a matrix, and adds high latent heat of phase change material in the pores of the aerogel. The high latent heat of phase change material can change phase at high temperature, and can absorb heat in the process, so that the change of the ambient temperature is reduced, thereby improving the specific heat capacity of the diaphragm, greatly improving the high-temperature resistance of the diaphragm, and the high porosity of the aerogel can ensure that the ion transmission capacity is not damaged, so that the high-temperature safety of the battery is improved while the power performance of the battery is stable. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 A diaphragm cross-sectional view is provided in the application;

[0032] Figure 2 A diaphragm cross-sectional view with a coating is provided in the application. DETAILED DESCRIPTION

[0033] In order for those skilled in the art to better understand the scheme of the application, the application is further described in detail below. The following specific embodiments are only used to describe the principles and characteristics of the application, and the examples are only used to explain the application, and do not limit the scope of the application. Based on the embodiments of the application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the application.

[0034] The first aspect of the application provides a diaphragm, which comprises an aerogel film layer, and the pores of the aerogel film layer comprise high latent heat of phase change material. The diaphragm cross-sectional view provided by the application, as shown in Figure 1 , comprises aerogel 101 and high latent heat of phase change material 102 distributed in the pores of the aerogel.

[0035] During the use of the battery, a high-temperature environment often occurs. In order to improve the safety of the battery in use, the high-temperature resistance of the diaphragm needs to be improved. Since the diaphragm does not contribute to the charge and discharge capacity in the battery, the mass of the diaphragm will affect the energy density of the battery, so the application selects aerogel with high porosity and low density as a matrix to reduce the mass of the diaphragm to ensure that the energy density of the battery is not affected, and adds high latent heat of phase change material that can change phase and absorb heat at high temperature in the pores of the aerogel, thereby improving the specific heat capacity of the diaphragm, so that the diaphragm has good high-temperature resistance, and the high-temperature cycle capacity retention rate of the battery is improved.

[0036] Therefore, the diaphragm provided by the application takes aerogel with high porosity and low density as a matrix, and adds high latent heat of phase change material in the pores of the aerogel, thereby greatly improving the high-temperature resistance of the diaphragm, and the high porosity of the aerogel can ensure that the ion transmission capability is not destroyed, thereby ensuring the stability of the power performance of the battery while improving the high-temperature safety of the battery.

[0037] In a specific embodiment, the thickness of the aerogel film layer is 8 μm to 15 μm. For example, the thickness of the diaphragm is 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, or a range formed by any two of the above values. The diaphragm itself does not contribute to the charge and discharge capacity, so the thickness of the diaphragm will affect the performance of the battery. Controlling the thickness of the diaphragm within the above range can ensure the stability of the power performance of the battery while improving the high-temperature safety performance of the battery.

[0038] In a specific embodiment, the volume of the high latent heat of phase change material accounts for 10% to 48% of the pore volume of the aerogel film layer. For example, the volume of the high latent heat of phase change material accounts for 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 48% of the pore volume of the aerogel film layer, or a range formed by any two of the above values. The high latent heat of phase change material can form a stable three-dimensional structure in the pores of the aerogel film layer, and the pores of the aerogel film layer are the key to ensuring smooth ion transmission. Therefore, controlling the ratio of the volume of the high latent heat of phase change material to the pore volume of the aerogel film layer within the above range can ensure the power performance of the battery is not affected, and also improve the high-temperature resistance of the battery.

[0039] In a specific embodiment, the pore size of the pores of the aerogel film layer is 100 nm to 230 nm. For example, the pore size of the pores of the aerogel film layer is 100 nm, 120 nm, 140 nm, 160 nm, 180 nm, 200 nm, 210 nm, 230 nm, or a range formed by any two of the above values. The aerogel film layer with a pore size within the above range has certain heat resistance, and it is convenient for the high latent heat of phase change material to stably exist in the pores of the aerogel film layer, which improves the high-temperature resistance of the diaphragm and ensures the stability of the power performance of the battery.

[0040] In a preferred embodiment, the aerogel film layer comprises at least one of polyimide aerogel and ceramic aerogel. The above-mentioned aerogel has high porosity, small contribution to the weight of the battery, and stronger mechanical properties than other aerogels. The diaphragm prepared has excellent lithium dendrite penetration resistance, can significantly improve the energy density of the battery under the premise of ensuring the power performance of the battery, and improves the high-temperature resistance and safety performance.

[0041] In a preferred embodiment, the ceramic aerogel comprises an organosilicon source aerogel. The organosilicon source aerogel refers to a silicon-based aerogel prepared by using an organic compound as the silicon source, and the organosilicon source can be tetramethyl orthosilicate or tetraethyl orthosilicate. Compared with other types of ceramic aerogels, such as inorganic silicon source aerogels and alumina aerogels, the organosilicon source aerogel has a low impurity content and has a smaller impact on the long-term life of the battery.

[0042] In a preferred embodiment, the high latent heat of phase change material comprises at least one of paraffin, fatty acid or high latent heat of phase change salt material; wherein the melting point of the paraffin is ≥ 50℃; and / or, the carbon chain length of the fatty acid is ≥ 12; and / or, the high latent heat of phase change salt material comprises at least one of The phase change temperature and latent heat of high melting point paraffin and long chain fatty acid have obvious advantages over other materials, and are environmentally friendly; the high latent heat of phase change salt material, especially the above-mentioned substances, has excellent heat absorption capacity, and the phase change temperature covers the working temperature range of the battery, which can effectively balance the temperature fluctuation caused by heat generation during the charging and discharging process of the battery, thereby improving the high temperature resistance of the battery.

[0043] In an optional embodiment, the separator further comprises a coating layer, and the coating layer is located on at least one side of the aerogel film layer; the coating layer comprises at least one of polyvinylidene fluoride, acrylic resin, polyurethane resin, alumina, boehmite, magnesium hydroxide and silicon oxide. For example, a cross section of a separator provided with a coating layer according to the present application is shown in Figure 2 As shown in the figure, it comprises an aerogel 201, a high latent heat of phase change material 202 distributed in the pores of the aerogel, and a coating layer 203 coated on the surface of the aerogel. Coating a layer of coating on the surface of the aerogel film layer containing the high latent heat of phase change material can prevent the high latent heat of phase change material from overflowing from the aerogel, so that the high latent heat of phase change material can stably exist in the pores of the aerogel film layer, further improving the high temperature resistance of the separator. Compared with other coating layers, the above-mentioned coating layer has good stability in the battery system, and can improve the wettability between the electrolyte and the separator, which is beneficial to the power performance of the battery cell.

[0044] In a specific embodiment, the thickness T of the coating layer is 0 < T ≤ 1 μm. For example, the thickness T of the coating layer is 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm or a range composed of any two of the above values. The thickness of the separator will affect the power performance of the battery. Controlling the thickness of the coating layer within the above range can ensure that the high latent heat of phase change material does not overflow, and at the same time, the thickness of the separator will not affect the power performance of the battery.

[0045] The second aspect of the present application provides a preparation method of the separator of the first aspect, the preparation method comprising the following steps: mixing an initial aerogel film layer with a high latent heat of phase change material to obtain the separator comprising the aerogel film layer; or mixing a mixed system for preparing the aerogel with the high latent heat of phase change material to obtain the separator comprising the aerogel film layer.

[0046] It should be noted that the preparation method is different when the high latent heat of phase change material is different, which can be determined according to the type of the high latent heat of phase change material.

[0047] The initial aerogel film layer refers to the aerogel film layer without the high latent heat of phase change material.

[0048] The mixed system for preparing the aerogel refers to the composition of the raw materials mixed together during the preparation of the aerogel, which can be a clear liquid, an emulsion, a semi-solid mixture, etc., and is not limited in the embodiment.

[0049] Specifically, the aerogel can be prepared into a film layer first, and then the initial aerogel film layer is placed in the high latent heat of phase change material to obtain the separator provided by the present application; or the high latent heat of phase change material is added to the mixed system for preparing the aerogel during the preparation of the aerogel, and then the aerogel film layer is prepared to obtain the separator provided by the present application. The addition of the high latent heat of phase change material in the aerogel greatly improves the high temperature resistance of the aerogel as the separator, and further improves the high temperature safety of the battery.

[0050] In a specific embodiment, the high latent heat of phase change material is paraffin and / or fatty acid, and the preparation method comprises: soaking the initial aerogel film layer in a solution comprising paraffin and / or fatty acid to obtain the separator. Specifically, when the high latent heat of phase change material is paraffin and / or fatty acid, the aerogel can be prepared into a film layer first, such as polyimide aerogel, which is prepared by dissolving a certain molar ratio of 4,4'-diamino diphenyl ether (ODA) and pyromellitic dianhydride (PMDA) in N-methyl pyrrolidone (NMP) solvent to obtain a polyamic acid (PAA) emulsion, then spraying the PAA emulsion onto a quartz glass carrier, soaking and heating to obtain the initial aerogel film layer; soaking the initial aerogel film layer in a solution of paraffin and / or fatty acid for 24 hours, and drying with a freeze dryer to obtain the separator provided by the present application. Soaking the initial aerogel film layer in the paraffin and / or fatty acid solution can make the paraffin and / or fatty acid stably exist in the pores of the aerogel, thereby improving the specific heat capacity of the separator and having strong high temperature resistance in the battery.

[0051] The molar ratio of ODA and PMDA is 0.98-1.03; the paraffin solution is prepared by dissolving paraffin in petroleum ether, the mass fraction of paraffin is 15%-48%, and the melting point of paraffin is 55-65℃; the fatty acid solution is prepared by dissolving fatty acid in a mixed system of dimethylacetamide and lithium chloride, and the mass fraction ratio of dimethylacetamide, lithium chloride and fatty acid is .

[0052] In a specific embodiment, the high latent heat phase change material is a high latent heat phase change salt material, and the preparation method comprises the following steps: mixing the high latent heat phase change salt material with a mixed system for preparing aerogel to obtain a mixture, and preparing a diaphragm from the mixture.

[0053] Specifically, when the high latent heat phase change material is a high latent heat phase change salt material, the high latent heat phase change salt material is added in the process of preparing aerogel, i.e. the high latent heat phase change salt material is added into a mixed system for preparing aerogel; for example, the polyimide aerogel is prepared by dissolving a certain molar ratio of ODA and PMDA in NMP solvent to obtain a PAA emulsion, at this time, the mixed system for preparing aerogel is the PAA emulsion, and a proper amount of high latent heat phase change salt material is added into the PAA emulsion to obtain a mixture, which is sprayed onto a quartz glass carrier, and after film formation, the organic impurities are removed by immersion, and then heated to obtain a stable aerogel film layer, which is a diaphragm used in the present application. The high latent heat phase change salt material is added in the process of preparing aerogel, so that the high latent heat phase change salt material can stably exist in the pores of the aerogel film layer, thereby improving the specific heat capacity of the diaphragm and improving the high temperature resistance of the diaphragm in the battery.

[0054] The molar ratio of ODA and PMDA is 0.95-1.05; the mass fraction of the high latent heat phase change salt material is 10%-40%.

[0055] Alternatively, the high latent heat phase change salt material can also be added in the process of preparing aerogel, and after the aerogel film layer is prepared, it is immersed in a paraffin solution to obtain a diaphragm in which paraffin and high latent heat phase change salt material exist in the pores.

[0056] In a specific embodiment, the preparation method further comprises: providing a coating layer on at least one side of the aerogel film layer to obtain a diaphragm. Specifically, after the aerogel including the high latent heat phase change material is prepared into a film layer, a coating layer can be coated on at least one side of the film layer by using a spraying process, and the coating layer can be an organic film layer or an inorganic film layer. Coating a coating layer on the aerogel film layer can effectively prevent the high latent heat phase change material from overflowing, and further improve the high temperature resistance of the diaphragm.

[0057] The third aspect of the present application provides a battery comprising the separator of the first aspect or the separator prepared by the method of the second aspect. In addition to the separator, the battery further comprises a positive electrode sheet, a negative electrode sheet and an electrolyte.

[0058] The positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer. The positive electrode current collector can be a conventional positive electrode current collector in the art, such as an aluminum foil. The positive electrode active material layer can be one or more of conventional positive electrode materials in the art, such as lithium iron phosphate, lithium cobaltate and ternary materials, without limitation.

[0059] The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer. The negative electrode current collector can be a conventional negative electrode current collector in the art, such as a copper foil. The negative electrode active material layer can be one or more of conventional negative electrode materials in the art, such as graphite, silicon-oxygen materials, without limitation.

[0060] The electrolyte comprises a lithium salt and a solvent. The lithium salt can be at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium bis-trifluoromethylsulfonylimide (LiTFSI), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiODFB), etc. The solvent can be at least one of ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), 1,2-dimethoxyethane (DME), etc., without limitation.

[0061] In a specific embodiment, the battery of the present application can be prepared by the following method: the positive electrode sheet, the separator and the negative electrode sheet are combined by stacking or winding to form a combination, which can be packaged inside a metal shell or by a composite film. After the packaged battery is dried at 85°C to remove moisture, the electrolyte is injected into the dried battery. After the battery is left to stand, formed and sealed for the second time, the battery of the present application is obtained.

[0062] The metal shell can be aluminum or steel, and the composite film can be aluminum, polypropylene, etc., without limitation.

[0063] The battery of the present application can include a battery monomer, a battery module and a battery pack. In some embodiments, the battery monomer can be assembled into a battery module, and the number of battery monomers contained in the battery module can be one or more, and the specific number can be selected by a person skilled in the art according to the application and capacity of the battery module. In some embodiments, the battery module can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by a person skilled in the art according to the application and capacity of the battery pack.

[0064] The specific type of the battery of the present application is not particularly limited, for example, from the perspective of shape, the battery includes but is not limited to a square shell battery, a soft package battery, a cylindrical battery, and the like, and the present application does not make a special limitation. From the perspective of the pole core structure, the pole core of the battery can be a wound pole core (i.e., a positive plate, a negative plate, and a separator are stacked and then a pole core is made through a winding process), or can be a laminated pole core (i.e., a plurality of positive plates, negative plates, and separators are stacked to form a pole core). The shell can be a hard shell (such as a steel shell, a hard plastic shell, and the like), or can be a soft shell (such as an aluminum plastic film, a bag type soft shell, and the like), and the like. The present application does not make a special limitation.

[0065] The fourth aspect of the present application provides a power consuming device including the battery of the third aspect. The present application does not make a special limitation on the type of the power consuming device, which can be any power consuming device including the battery, including but not limited to a mobile phone, a portable device, a notebook computer, an electric bicycle, an electric vehicle, an electric toy, an energy storage device, and the like.

[0066] The separator and the preparation method thereof, the battery, and the power consuming device provided by the present application will be specifically introduced below through specific examples.

[0067] Unless otherwise specified, the reagents, materials, and instruments used in the following examples are conventional reagents, conventional materials, and conventional instruments in the art, and can be obtained by commercial purchase. The reagents involved can also be obtained by synthesizing through conventional methods in the art.

[0068] Example 1

[0069] Preparation of the separator

[0070] 1) 4,4'-diaminodiphenyl ether (ODA) and pyromellitic dianhydride (PMDA) were dissolved in N-methyl pyrrolidone (NMP) solvent at a molar ratio of 1:1, stirred at 25°C for 30 minutes to obtain a polyamic acid (PAA) emulsion, and the PAA emulsion was sprayed onto a quartz glass carrier at 10 ug / cm ^2 to obtain an initial polyimide aerogel film layer;

[0071] 2) The initial polyimide aerogel film layer was soaked in ethanol for 24 hours, then heated in a 200°C tube furnace for 1.5 hours, and after cooling, the film was soaked in a paraffin solution with a melting point of 70°C for 24 hours, and the mass fraction of paraffin was 33%;

[0072] 3) The above aerogel film layer was taken out, the surface solution was absorbed, and then placed in a -20°C environment box for 30 minutes and then placed in a freeze dryer for 48 hours to obtain a separator.

[0073] Example 2

[0074] 1) 4,4'-diaminodiphenyl ether (ODA) and pyromellitic dianhydride (PMDA) were dissolved in N-methyl pyrrolidone (NMP) solvent at a molar ratio of 1:1, stirred at 25°C for 30 minutes to obtain a polyamic acid (PAA) emulsion;

[0075] 2) 40% by mass of was added to the PAA emulsion, and stirred uniformly to obtain a mixture, which was sprayed onto a quartz glass carrier at 10 ug / cm ^2 to obtain a polyimide aerogel film layer;

[0076] 3) The polyimide aerogel film layer was soaked in ethanol for 24 h, and then heated in a 200°C tube furnace for 1.5 h, and after cooling, a separator was obtained.

[0077] Example 3

[0078] The difference between this example and Example 2 is that in step 2), the is replaced by , with a mass fraction of 38%, and the other conditions are the same as in Example 2.

[0079] Example 4

[0080] The difference between this example and Example 1 is that in step 2), the paraffin solution is replaced by a lauric acid solution, and the mass fraction of lauric acid is 30%, and the other conditions are the same as in Example 1.

[0081] Example 5

[0082] The difference between this example and Example 2 is that in step 2), the mass fraction of NiCl2 is 20%, and after step 3) is completed, the obtained film is soaked in a paraffin solution for 24 h, wherein the mass fraction of paraffin is 17%, and after the above aerogel film layer is taken out and the surface solution is absorbed, it is placed in a -20°C environment box for freezing for 30 minutes and then placed in a freeze dryer for drying for 48 h to obtain a final separator, and the other conditions are the same as in Example 2.

[0083] Example 6

[0084] The difference between this example and Example 1 is that in step 1), the PAA emulsion is sprayed onto the quartz glass carrier at 8 ug / cm ^2 , and the other conditions are the same as in Example 1.

[0085] Example 7

[0086] The difference between this example and Example 1 is that in step 1), the PAA emulsion is sprayed onto the quartz glass carrier at 15 ug / cm ^2 , and the other conditions are the same as in Example 1.

[0087] Example 8

[0088] The difference between this example and Example 1 is that in step 1), the PAA emulsion is sprayed onto the quartz glass carrier at 3 ug / cm ^2 The rest of the conditions are the same as in Example 1.

[0089] Example 9

[0090] The difference between this example and Example 1 is that in step 1), the PAA emulsion is sprayed onto the quartz glass carrier at 20 ug / cm ^2 The rest of the conditions are the same as in Example 1.

[0091] Example 10

[0092] The difference between this example and Example 1 is that in step 2), the mass fraction of paraffin is 15%, and the rest of the conditions are the same as in Example 1.

[0093] Example 11

[0094] The difference between this example and Example 1 is that in step 2), the mass fraction of paraffin is 48%, and the rest of the conditions are the same as in Example 1.

[0095] Example 12

[0096] The difference between this example and Example 1 is that in step 2), the mass fraction of paraffin is 11%, and the rest of the conditions are the same as in Example 1.

[0097] Example 13

[0098] The difference between this example and Example 1 is that in step 2), the mass fraction of paraffin is 58%, and the rest of the conditions are the same as in Example 1.

[0099] Example 14

[0100] The difference between this example and Example 1 is that in step 1), the molar ratio of 4,4'-diamino diphenyl ether (ODA) and pyromellitic dianhydride (PMDA) is 1.12:1, and the rest of the conditions are the same as in Example 1.

[0101] Example 15

[0102] The difference between this example and Example 1 is that in step 1), the molar ratio of 4,4'-diamino diphenyl ether (ODA) and pyromellitic dianhydride (PMDA) is 1.07:1, and the rest of the conditions are the same as in Example 1.

[0103] Example 16

[0104] The difference between this embodiment and embodiment 1 is that in step 1), 4,4'-diaminodiphenyl ether (ODA) and pyromellitic dianhydride (PMDA) are mixed at a molar ratio of 1.03:1, and the rest of the conditions are the same as in embodiment 1.

[0105] Example 17

[0106] The difference between this embodiment and embodiment 1 is that in step 1), 4,4'-diaminodiphenyl ether (ODA) and pyromellitic dianhydride (PMDA) are mixed at a molar ratio of 0.90:1, and the rest of the conditions are the same as in embodiment 1.

[0107] Example 18

[0108] The difference between this embodiment and embodiment 1 is that in step 1), tetraethyl orthosilicate (TEOS): ethanol: water are mixed at a molar ratio of 1:4:8, stirred at 50°C for 2 hours to generate a silicic acid monomer sol; adjust the pH to neutral (pH=6~7), after standing for 8h, the sol is sprayed onto a quartz glass carrier at 10ug / cm ^2 The initial organic silicon source aerogel film layer is obtained, and the rest of the conditions are the same as in embodiment 1.

[0109] Example 19

[0110] The difference between this embodiment and embodiment 1 is that step 4) is added, which sprays a layer of 0.5μm polyvinylidene fluoride (PVDF) coating on the surface of the aerogel film layer obtained after step 3), and the rest of the conditions are the same as in embodiment 1.

[0111] Example 20

[0112] The difference between this embodiment and embodiment 19 is that in step 4), the sprayed layer is aluminum oxide, and the rest of the conditions are the same as in embodiment 19.

[0113] Example 21

[0114] The difference between this embodiment and embodiment 19 is that in step 4), the sprayed layer is 1μm, and the rest of the conditions are the same as in embodiment 19.

[0115] Example 22

[0116] The difference between this embodiment and embodiment 19 is that in step 4), the sprayed layer is 2μm, and the rest of the conditions are the same as in embodiment 19.

[0117] Comparative Example 1

[0118] In this comparative example, polypropylene (PP) is used as the separator.

[0119] Comparative Example 2

[0120] The polyimide aerogel film prepared in step 1) in Example 1 was used as the separator in the present comparative example.

[0121] Comparative Example 3

[0122] The difference between the present comparative example and Example 1 is that the initial polyimide aerogel film layer in step 1) is replaced by a PP film, and the rest of the conditions are the same as in Example 1.

[0123] Test Example

[0124] I. Specific heat capacity test of the separator in the above examples and comparative examples was performed according to the following method:

[0125] The mass of the separator was recorded and the separator was placed in an adiabatic container. The adiabatic container was placed in a constant temperature water bath, and an electric heater was placed in the adiabatic container. The heating power of the electric heater and the initial temperature of the separator were recorded. The temperature change of the separator was observed until the temperature was stable. The electric heater was turned off, and the final temperature and heating time of the separator were recorded. The specific heat capacity was calculated according to the following formula:

[0126] Specific heat capacity = (heating power x heating time) / (mass x temperature difference), wherein the temperature difference is the final temperature - initial temperature.

[0127] II. The separators in the above examples and comparative examples were assembled with positive electrode sheets, negative electrode sheets and electrolyte to obtain lithium ion batteries according to the following method:

[0128] 1) Lithium iron phosphate, carbon black, PVDF and N-methyl pyrrolidone were mixed in a ratio of 100:13.2:2.3:52.5 to obtain a positive electrode slurry. The positive electrode slurry was coated on an aluminum foil current collector, dried, roll-pressed to form a sheet, and a positive electrode sheet was obtained.

[0129] 2) Graphite powder, carbon black, SBR, CMC-Na and deionized water were mixed in a ratio of 100:1.5:3.0:1.2:115. After uniform dispersion, a negative electrode slurry was formed. The negative electrode slurry was coated on a copper foil current collector, dried, roll-pressed to form a sheet, and a negative electrode sheet was obtained.

[0130] 3) The above positive electrode sheet, negative electrode sheet and separator were obtained by lamination or winding process to obtain a battery cell. After baking, the electrolyte was injected. The electrolyte was prepared by mixing ethylene carbonate (EC), dimethyl carbonate (DMC) and methyl ethyl carbonate (EMC) in a volume ratio of 1:1:1, adding 1M LiPF6, and then forming, high temperature aging to obtain a lithium ion battery.

[0131] The lithium ion batteries obtained above were tested for the following performance:

[0132] 1. 50% SOC DCIR at room temperature

[0133] Test method: test the initial capacity of the battery at room temperature, adjust the SOC of the battery to 60%, place the battery in an environmental chamber at 25°C, stand for 12h, discharge at 3C current for 30s, stand for 30min, record the standing voltage V1 before discharging, the discharging voltage V2 after 10s, .

[0134] 2. High-temperature cycle capacity retention rate

[0135] Test method:

[0136] Place the battery in an environmental chamber at 60°C, stand for 6h, charge the single battery at 60°C to the charge termination voltage at 0.5C current, stand for 5min, charge to the charge termination voltage at 0.2C current, stand for 5min, charge to the charge termination voltage at 0.05C current, stand for 30min, discharge the single battery at 60°C to 2.0V at 1C current, stand for 30min, repeat the above steps for a total of 500 times, .

[0137] Table 1

[0138]

[0139]

[0140]

[0141]

[0142]

[0143] As shown in Table 1, comparative examples 1-5 and comparative examples 1-3 can be seen that the diaphragm prepared by adding high latent heat of phase change material to aerogel as a matrix has good specific heat capacity, the high temperature resistance of the battery is significantly improved, the capacity cycle retention rate is greatly increased while the power performance is stable; from the comparison of examples 6-9 and example 1, it can be concluded that when the thickness of the diaphragm is in the range of 8-15 μm, both the stable power performance of the battery and the improved capacity cycle retention rate can be ensured; from the comparison of comparative examples 10-13 and example 1, it can be known that by controlling the volume ratio of high latent heat of phase change material in the pores of aerogel to be 10-48%, the power performance of the battery can be improved while the capacity cycle retention rate is improved; from the comparison of examples 14-17 and example 1, it can be known that when the pores of aerogel are in the range of 100-230 nm, both the power performance and the capacity cycle retention rate of the battery are good; from the comparison of example 18 and example 1, it can be concluded that the diaphragm prepared from organic silicon source aerogel has high specific heat capacity and good battery performance; from the comparison of examples 19-20 and example 1, it can be known that adding a coating layer can avoid the overflow of the coating from the aerogel, thereby improving the capacity cycle retention rate of the battery; from the comparison of examples 21-22 and example 19, it can be known that by controlling the thickness of the coating layer, the capacity cycle retention rate can be improved while the power performance of the battery is stable.

[0144] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A battery separator, characterized in that: The battery separator includes an aerogel film layer, the pores of the aerogel film layer include a high phase change latent heat material, the volume of the high phase change latent heat material accounts for 30% to 48% of the pore volume of the aerogel film layer, and a composite coating of polyvinylidene fluoride and aluminum oxide is provided on both sides of the aerogel film layer. The aerogel film layer is a composite aerogel of polyimide aerogel and silicone source aerogel.

2. The battery separator according to claim 1, characterized in that The thickness of the aerogel film layer is 8 μm to 15 μm.

3. The battery separator according to claim 1 or 2, characterized in that The pores of the aerogel membrane layer have a pore diameter of 100 nm to 230 nm.

4. The battery separator according to claim 1, characterized in that The high phase change latent heat material includes at least one of paraffin, fatty acid or high phase change latent heat salt material; Wherein, the melting point of the paraffin wax is ≥50°C; and / or, the carbon chain length of the fatty acid is ≥12; And / or, the high phase change latent heat salt material includes At least one of .

5. The battery separator according to claim 1, characterized in that The thickness T of the coating is 0<T≤1 μm.

6. A method for preparing a battery separator according to any one of claims 1 to 5, characterized in that: The preparation method comprises the following steps: mixing an initial aerogel film layer with a high phase change latent heat material to obtain an aerogel film layer comprising the high phase change latent heat material, and providing a coating on at least one side of the aerogel film layer to obtain the separator; Alternatively, the mixed system for preparing aerogel is mixed with a high phase change latent heat material to obtain an aerogel film layer including the high phase change latent heat material, and a coating is provided on at least one side of the aerogel film layer to obtain the diaphragm.

7. The preparation method according to claim 6, characterized in that The high phase change latent heat material is paraffin and / or fatty acid, and the preparation method includes: The initial aerogel membrane layer is immersed in a solution including the paraffin wax and / or the fatty acid to obtain the separator.

8. The preparation method according to claim 6, characterized in that The high phase change latent heat material is a high phase change latent heat salt material, and the preparation method includes: The high phase change latent heat salt material is mixed with the mixed system for preparing aerogel to obtain a mixture, and the mixture is made into the diaphragm.

9. A battery, characterized in that: The battery comprises the battery separator according to any one of claims 1 to 5 or the battery separator prepared by the preparation method of the battery separator according to any one of claims 6 to 8.

10. An electrical device, characterized in that: The electric device comprises the battery according to claim 9.

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