Diaphragm and preparation method thereof, battery and electric equipment

Abstract

The embodiment of the invention provides a diaphragm and a preparation method thereof, a battery and electric equipment. The diaphragm comprises an aerogel film layer, and pores of the aerogel film layer comprise a high-phase-change latent heat material. The aerogel has high porosity, so that the power performance of the battery is optimized; meanwhile, due to the existence of the high-phase-change latent heat material, the battery has higher specific heat capacity, and the high-temperature cycle life is longer.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a diaphragm and a preparation method thereof, a battery, and an electrical device. Background Art

[0002] As one of the components of liquid lithium-ion batteries, the main function of the diaphragm is to block the electron transmission between the positive and negative electrode materials while ensuring that ions can pass through normally, thereby completing the charging and discharging process. Therefore, the battery power performance can be improved by increasing the porosity of the diaphragm.

[0003] Common diaphragms include polyethylene (PE) diaphragm, polypropylene (PP) diaphragm, etc., or a dressing can be coated on the surface of the electrode to replace the diaphragm.

[0004] However, batteries often experience high temperatures during use. While ensuring battery performance, high-temperature safety must also be ensured, so the high-temperature resistance of the diaphragm needs to be improved urgently. Summary of the invention

[0005] The present invention provides a diaphragm and a preparation method thereof, a battery and an electrical device. The aerogel is used as a matrix, and a high phase change latent heat material is added into the pores of the aerogel, so that the specific heat capacity of the diaphragm is improved, thereby improving the high temperature safety performance of the battery.

[0006] According to a first aspect of the present invention, a diaphragm is provided. The diaphragm comprises an aerogel film layer, wherein pores of the aerogel film layer comprise a high phase change latent heat material.

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

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

[0009] According to an embodiment of the present invention, the pores of the aerogel film layer have a pore diameter of 100 nm to 230 nm.

[0010] According to an embodiment of the present invention, the aerogel includes at least one of polyimide aerogel and ceramic aerogel.

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

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

[0013] Wherein, the melting point of the paraffin wax is ≥50°C;

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

[0015] And / or, the high phase change latent heat salt material includes At least one of .

[0016] According to one embodiment of the present invention, the diaphragm further comprises a coating, and the coating is located on at least one side of the aerogel film layer;

[0017] The coating 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 invention, the thickness T of the coating is 0<T≤1 μm.

[0019] A second aspect of the present invention provides a method for preparing the diaphragm according to the first aspect, the method comprising the following steps:

[0020] Mixing the initial aerogel film layer with a high phase change latent heat material to obtain the separator including the aerogel film layer;

[0021] Alternatively, the mixed system for preparing aerogel is mixed with a material with high phase change latent heat to obtain the separator including the aerogel film layer.

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

[0023] The initial aerogel film layer is immersed in a solution including the paraffin wax and / or the fatty acid to obtain the separator.

[0024] According to an embodiment of the present invention, the high phase change latent heat material is a high phase change latent heat salt material, and the preparation method includes:

[0025] 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.

[0026] According to one embodiment of the present invention, the preparation method further comprises:

[0027] A coating is provided on at least one side of the initial aerogel film layer to obtain the separator.

[0028] A third aspect of the present invention provides a battery, wherein the battery comprises the diaphragm as described in the first aspect or the diaphragm prepared by the method for preparing the diaphragm as described in the second aspect.

[0029] A fourth aspect of the present invention provides an electrical device, wherein the electrical device comprises the battery as described in the third aspect.

[0030] The present invention provides a diaphragm and a preparation method thereof, a battery, and an electrical device. The diaphragm uses an aerogel with high porosity and low density as a matrix, and a high phase change latent heat material is added to the pores of the aerogel. Since the high phase change latent heat material will undergo a phase change in a high temperature environment, it can absorb heat in this process to reduce the change in ambient temperature, thereby increasing the specific heat capacity of the diaphragm and greatly improving the high temperature resistance of the diaphragm. The high porosity of the aerogel can ensure that the ion transmission capacity is not destroyed, thereby improving the high temperature safety of the battery while ensuring the stability of the battery power performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A schematic diagram of a cross-section of a diaphragm provided in this application;

[0032] Figure 2 A schematic cross-sectional view of a coated diaphragm provided in the present application. DETAILED DESCRIPTION

[0033] In order to enable those skilled in the art to better understand the scheme of the present invention, the present invention is further described in detail below. The specific implementation methods listed below are only for describing the principles and features of the present invention. The examples are only used to explain the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention.

[0034] The first aspect of the present invention provides a diaphragm, which includes an aerogel film layer, and the pores of the aerogel film layer include a high phase change latent heat material. The cross section of the diaphragm provided by the present invention is as follows: Figure 1 As shown, it includes an aerogel 101 and a high phase change latent heat material 102 distributed in the pores of the aerogel.

[0035] During the use of the battery, a high temperature environment usually occurs. In order to improve the safety of the battery, 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 quality of the diaphragm will affect the energy density of the battery. Therefore, the present invention uses aerogel with high porosity and low density as the matrix to reduce the quality of the diaphragm to ensure that the energy density of the battery is not affected, and adds a high phase change latent heat material that will undergo phase change and absorb heat in a high temperature environment to the pores of the aerogel, thereby increasing the specific heat capacity of the diaphragm, making the diaphragm have good high temperature resistance and improving the high temperature cycle capacity retention rate of the battery.

[0036] Therefore, the diaphragm provided by the present invention uses aerogel with high porosity and low density as the matrix, and adds high phase change latent heat material into the pores of the aerogel, which greatly improves the high temperature resistance of the diaphragm. The high porosity of the aerogel can ensure that the ion transmission capacity is not destroyed, thereby improving the high temperature safety of the battery while ensuring the stability of the battery power performance.

[0037] In a specific embodiment, the thickness of the aerogel film layer is 8 μm to 15 μm. Exemplarily, 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 consisting of 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 improve the high temperature safety performance of the battery while ensuring the stability of the battery power performance.

[0038] In a specific embodiment, the volume of the high phase change latent heat material accounts for 10% to 48% of the pore volume of the aerogel film layer. Exemplarily, the volume of the high phase change latent heat material accounts for 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 48% of the pore volume of the aerogel film layer, or a range consisting of any two of the above values. The high phase change latent heat 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 the smooth transmission of ions. Therefore, controlling the ratio of the volume of the high phase change latent heat material to the pore volume of the aerogel film layer within the above range can not only ensure that the power performance of the battery is not affected, but also improve the high temperature resistance of the battery.

[0039] In a specific embodiment, the pores of the aerogel film layer have a pore size of 100 nm to 230 nm. Exemplarily, the pore size 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 consisting of any two of the above values. The aerogel film layer with a pore size within the above range has a certain heat resistance and facilitates the stable existence of high phase change latent heat materials in the pores of the aerogel film layer, which not only improves the high temperature resistance of the diaphragm, but also ensures the stable power performance of the battery.

[0040] In a preferred embodiment, the aerogel film layer includes at least one of polyimide aerogel and ceramic aerogel. The above-mentioned aerogel has a high porosity, contributes little to the weight of the battery cell, and has stronger mechanical properties than other aerogels. The prepared diaphragm has excellent resistance to lithium dendrite penetration, and can significantly improve the energy density of the battery while ensuring that the power performance of the battery is not lost, so as to improve the high temperature resistance and safety performance.

[0041] In a preferred embodiment, the ceramic aerogel includes an organic silicon source aerogel. Organic silicon source aerogel refers to a silicon-based aerogel prepared by providing a silicon source from an organic compound, and the organic silicon source may be methyl orthosilicate or ethyl orthosilicate. Compared with other types of ceramic aerogels, such as inorganic silicon source aerogels and alumina aerogels, organic silicon source aerogels have low impurity content and have little effect on the long-term life of the battery.

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

[0043] In an optional embodiment, the membrane further comprises a coating, which is located on at least one side of the aerogel film layer; the coating comprises at least one of polyvinylidene fluoride, acrylic resin, polyurethane resin, aluminum oxide, boehmite, magnesium hydroxide, and silicon oxide. Exemplarily, the present invention provides a membrane cross section provided with a coating, such as Figure 2 As shown, it includes aerogel 201, high phase change latent heat material 202 distributed in the pores of the aerogel, and a coating 203 coated on the surface of the aerogel. Coating a layer of coating on the surface of the aerogel film layer including the high phase change latent heat material can prevent the high phase change latent heat material from overflowing from the aerogel, so that the high phase change latent heat material can stably exist in the pores of the aerogel film layer, further improving the high temperature resistance of the diaphragm. Compared with other coatings, the above coating has better stability in the battery system, and can improve the wettability between the electrolyte and the diaphragm, which is beneficial to the power performance of the battery cell.

[0044] In a specific embodiment, the thickness T of the coating is 0<T≤1μm. Exemplarily, the thickness T of the coating is 0.1μm, 0.2μm, 0.3μm, 0.4μm, 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1μm or a range consisting of any two of the above values. The thickness of the diaphragm will affect the power performance of the battery. Controlling the coating thickness within the above range ensures that the high phase change latent heat material will not overflow, and the power performance of the battery will not be affected by the thickness of the diaphragm.

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

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

[0047] The initial aerogel film layer refers to an aerogel film layer that does not include a high phase change latent heat material.

[0048] The mixed system for preparing aerogel refers to a composition of raw materials used in preparing aerogel, which may be a clear liquid, an emulsion, a semi-solid mixture, etc., and this embodiment does not limit this.

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

[0050] In a specific embodiment, the high phase change latent heat material is paraffin and / or fatty acid, and the preparation method includes: immersing the initial aerogel film layer in a solution including paraffin and / or fatty acid to obtain a diaphragm. Specifically, when the high phase change latent heat material is paraffin and / or fatty acid, the aerogel can be first prepared into a film layer, such as polyimide aerogel is first dissolved in a certain molar ratio of 4,4'-diaminodiphenyl ether (ODA) and pyromellitic anhydride (PMDA) in N-methylpyrrolidone (NMP) solvent to obtain a polyamic acid (PAA) emulsion, and then the PAA emulsion is sprayed onto a quartz glass carrier, and the initial aerogel film layer is obtained by immersion and heating; the initial aerogel film layer is immersed in a solution of paraffin and / or fatty acid and allowed to stand for 24 hours, and dried using a freeze dryer to obtain the diaphragm provided by the present invention. Immersing the initial aerogel film layer in a paraffin and / or fatty acid solution can allow the paraffin and / or fatty acid to stably exist in the pores of the aerogel, thereby increasing the specific heat capacity of the diaphragm and having a stronger high temperature resistance in the battery.

[0051] The molar ratio of ODA to 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°C-65°C; the fatty acid solution is prepared by dissolving fatty acids in a mixed system of dimethylacetamide and lithium chloride, wherein the mass ratio of dimethylacetamide: lithium chloride: fatty acid is = .

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

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

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

[0055] Optionally, a high phase change latent heat salt material may be added when preparing the aerogel, and after the aerogel film layer is prepared, it is immersed in a paraffin solution to obtain a diaphragm whose pores include both paraffin and the high phase change latent heat salt material.

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

[0057] The third aspect of the present invention provides a battery, comprising the diaphragm of the first aspect or the diaphragm prepared by the diaphragm preparation method of the second aspect. In addition to the diaphragm, the battery also includes a positive electrode sheet, a negative electrode sheet and an electrolyte.

[0058] Among them, the positive electrode sheet includes a positive electrode collector and a positive electrode active material layer. The positive electrode collector can adopt a conventional positive electrode collector in the art, such as aluminum foil; the positive electrode active material layer can adopt a conventional positive electrode material in the art, such as lithium iron phosphate, lithium cobalt oxide and ternary materials, etc. One or more of the above, this embodiment does not limit this.

[0059] Among them, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer. The negative electrode current collector can adopt a conventional negative electrode current collector in the art, such as copper foil; the negative electrode active material layer can adopt one or more conventional negative electrode materials in the art such as graphite, silicon oxide materials, etc., which are not limited in this embodiment.

[0060] The electrolyte comprises a lithium salt and a solvent, and the lithium salt may be lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), lithium bis(oxalatoborate) (LiBOB), lithium difluorooxalatoborate (LiODFB), etc.; the solvent may be at least one of ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), 1,2-dimethoxyethane (DME), etc., which is not limited in this embodiment.

[0061] In a specific embodiment, the battery of the present invention can be prepared by the following method: the positive electrode sheet, the separator and the negative electrode sheet are stacked or wound to form a combination, and the combination can be encapsulated in a metal shell or encapsulated by a composite film. After the encapsulated battery is dried at 85°C, the electrolyte is injected into the dried battery, and the battery is placed, formed and sealed for a second time to obtain the battery of the present invention.

[0062] The metal shell may be made of aluminum or steel, and the composite film may be made of aluminum, polypropylene, etc., which is not limited in this embodiment.

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

[0064] There is no special restriction on the specific type of battery in this application. For example, from the perspective of shape, the battery includes but is not limited to square shell batteries, soft-pack batteries and cylindrical batteries, etc., and this application does not impose any special restrictions. From the perspective of the pole core structure, the pole core of the battery can be a wound pole core (that is, the positive pole sheet, the negative pole sheet and the separator are stacked and arranged, and then the pole core is formed by a winding process), or it can be a laminated pole core (that is, multiple positive pole sheets, negative pole sheets and separators are stacked to form a pole core). The outer shell can be a hard shell (such as a steel shell, a hard plastic shell, etc.), or it can be a soft shell (such as an aluminum-plastic film, a bag-type soft shell, etc.). This application does not impose any special restrictions.

[0065] The fourth aspect of the present invention provides an electrical device, comprising the battery of the third aspect. The present invention does not specifically limit the type of electrical device, and it can be any electrical device including the battery, including but not limited to mobile phones, portable devices, laptop computers, electric bicycles, electric cars, electric toys, energy storage devices, etc.

[0066] The following will introduce the diaphragm and its preparation method, battery and electrical equipment provided by the present invention in detail through specific embodiments.

[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 commercially. The reagents involved can also be synthesized by conventional methods in the art.

[0068] Example 1

[0069] Preparation of diaphragm

[0070] 1) Dissolve 4,4'-diaminodiphenyl ether (ODA) and pyromellitic anhydride (PMDA) in N-methylpyrrolidone (NMP) solvent at a molar ratio of 1:1, and stir at 25°C for 30 minutes to obtain a polyamic acid (PAA) emulsion. ^2 Spraying onto a quartz glass carrier to obtain an initial polyimide aerogel film layer;

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

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

[0073] Example 2

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

[0075] 2) Add 40% by mass of , stir evenly to obtain a mixture, and then add the mixture at 10 ug / cm ^2 Spraying onto a quartz glass carrier to obtain a polyimide aerogel film layer;

[0076] 3) The polyimide aerogel film layer was immersed in ethanol and allowed to stand for 24 hours, then heated in a 200°C tubular furnace for 1.5 hours, and then cooled to obtain a diaphragm.

[0077] Example 3

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

[0079] Example 4

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

[0081] Example 5

[0082] The difference between this embodiment and embodiment 2 is that in step 2), NiCl 2 The mass fraction of is 20%, and after step 3), the obtained film is immersed in a paraffin solution and allowed to stand for 24 hours, wherein the mass fraction of the paraffin is 17%, the above-mentioned aerogel film layer is taken out and the surface solution is dried, and then it is placed in a -20°C environmental box and frozen for 30 minutes, and then placed in a freeze dryer and dried for 48 hours to obtain the final diaphragm, and the other conditions are the same as those in Example 2.

[0083] Example 6

[0084] The difference between this embodiment and embodiment 1 is that in step 1), the PAA emulsion is prepared at 8ug / cm ^2 The reaction mixture was sprayed onto a quartz glass carrier, and the other conditions were the same as those in Example 1.

[0085] Example 7

[0086] The difference between this embodiment and embodiment 1 is that in step 1), the PAA emulsion is prepared at a temperature of 15 ug / cm ^2 The reaction mixture was sprayed onto a quartz glass carrier, and the other conditions were the same as those in Example 1.

[0087] Example 8

[0088] The difference between this embodiment and embodiment 1 is that in step 1), the PAA emulsion is prepared at 3 ug / cm ^2 The reaction mixture was sprayed onto a quartz glass carrier, and the other conditions were the same as those in Example 1.

[0089] Example 9

[0090] The difference between this embodiment and embodiment 1 is that in step 1), the PAA emulsion is prepared at a temperature of 20 ug / cm ^2 The reaction mixture was sprayed onto a quartz glass carrier, and the other conditions were the same as those in Example 1.

[0091] Example 10

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

[0093] Embodiment 11

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

[0095] Example 12

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

[0097] Example 13

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

[0099] Embodiment 14

[0100] The difference between this embodiment and embodiment 1 is that in step 1), the molar ratio of 4,4'-diaminodiphenyl ether (ODA) to pyromellitic dianhydride (PMDA) is 1.12:1, and the other conditions are the same as those in embodiment 1.

[0101] Embodiment 15

[0102] The difference between this embodiment and embodiment 1 is that in step 1), the molar ratio of 4,4'-diaminodiphenyl ether (ODA) to pyromellitic dianhydride (PMDA) is 1.07:1, and the other conditions are the same as those in embodiment 1.

[0103] Example 16

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

[0105] Embodiment 17

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

[0107] Embodiment 18

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

[0109] Embodiment 19

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

[0111] Embodiment 20

[0112] The difference between this embodiment and Embodiment 19 is that the spray coating in step 4) is aluminum oxide, and the other conditions are the same as those in Embodiment 19.

[0113] Embodiment 21

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

[0115] Embodiment 22

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

[0117] Comparative Example 1

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

[0119] Comparative Example 2

[0120] In this comparative example, the polyimide aerogel film prepared in step 1) of Example 1 was used as a separator.

[0121] Comparative Example 3

[0122] The difference between this comparative example and Example 1 is that in step 1), the initial polyimide aerogel film layer is replaced with a PP film, and the other conditions are the same as those in Example 1.

[0123] Test Case

[0124] 1. The specific heat capacity of the diaphragms of the above embodiments and comparative examples was tested, and the specific method is as follows:

[0125] Record the mass of the diaphragm and place the diaphragm in an insulated container. Place the insulated container in a constant temperature water bath. Place the electric heater in the insulated container. Record the heating power of the electric heater and the initial temperature of the diaphragm. Observe the temperature change of the diaphragm until the temperature is stable. Turn off the electric heater. Record the final temperature and heating time of the diaphragm. Calculate the specific heat capacity according to the following formula:

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

[0127] 2. The separators of the above embodiments and comparative examples are assembled with the positive electrode sheet, the negative electrode sheet and the electrolyte according to the following method to obtain a lithium ion battery. The method is as follows:

[0128] 1) Mix lithium iron phosphate with carbon black, PVDF and N-methylpyrrolidone in a ratio of 100:13.2:2.3:52.5 and stir evenly to obtain a positive electrode slurry, apply the positive electrode slurry on an aluminum foil current collector, dry, and roll-press to obtain a positive electrode sheet;

[0129] 2) Graphite powder, carbon black, SBR, CMC-Na and deionized water are mixed evenly in a ratio of 100:1.5:3.0:1.2:115, and dispersed evenly to form a negative electrode slurry, and the negative electrode slurry is coated on a copper foil current collector, dried, and rolled to obtain a negative electrode sheet;

[0130] 3) The positive electrode sheet, negative electrode sheet and separator are stacked or wound to obtain a battery cell, which is baked and then injected with electrolyte. The electrolyte is a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) in a volume ratio of 1:1:1, and 1M LiPF is added. 6 The lithium-ion battery is obtained after formation and high-temperature aging.

[0131] The lithium-ion battery assembled above was subjected to the following performance tests:

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

[0133] Test method: At room temperature, test the initial capacity of the battery, adjust the battery SOC to 60%, place the battery in a 25℃ environmental chamber, leave it for 12 hours, discharge it at 3C current for 30 seconds, leave it for 30 minutes, and record the shelf voltage V before discharge. 1 、Discharge 10s voltage V 2 , .

[0134] 2. High temperature cycle capacity retention rate

[0135] Test method:

[0136] The battery was placed in an environmental chamber at 60°C for 6 hours. At 60°C, the single cell was charged to the charge termination voltage at a current of 0.5C, and left for 5 minutes. The single cell was charged to the charge termination voltage at a current of 0.2C, and left for 5 minutes. The single cell was charged to the charge termination voltage at a current of 0.05C, and left for 30 minutes. At 60°C, the single cell was discharged to 2.0V at a current of 1C, and left for 30 minutes. The above steps were repeated for a total of 500 times. .

[0137] Table 1

[0138]

[0139]

[0140]

[0141]

[0142]

[0143] As shown in Table 1, by comparing Examples 1 to 5 with Comparative Examples 1 to 3, it can be seen that the diaphragm prepared by adding high phase change latent heat material to the matrix of the present invention has good specific heat capacity, and the high temperature resistance of the battery is significantly improved. While ensuring the stability of the power performance, the capacity cycle retention rate is greatly increased; from the comparison of Examples 6 to 9 with Example 1, it can be concluded that when the diaphragm thickness is in the range of 8 μm to 15 μm, it can not only ensure the stability of the battery power performance, but also improve the capacity cycle retention rate; by comparing Examples 10 to 13 with Example 1, it can be seen that by controlling the volume proportion of the high phase change latent heat material in the aerogel pores to 10% to 48%, it can be achieved while improving the high temperature resistance of the battery and the capacity cycle retention rate. The power performance of the battery is maintained without destroying the power performance of the battery; from the comparison of Examples 14 to 17 with Example 1, it can be seen that when the pores of the aerogel are in the range of 100nm to 230nm, the power performance and capacity cycle retention rate of the battery are good; from the comparison of Example 18 with Example 1, it can be concluded that the diaphragm made of silicone source aerogel has a higher specific heat capacity and good battery performance; from the comparison of Examples 19 to 20 with Example 1, it can be seen that adding a coating can prevent the coating from overflowing from the aerogel, thereby improving the capacity cycle retention rate of the battery; from the comparison of Examples 21 to 22 with Example 19, it can be seen that by controlling the thickness of the coating, the battery power performance can be kept stable while the capacity cycle retention rate is improved.

[0144] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A diaphragm, characterized in that: The separator comprises an aerogel film layer, and pores of the aerogel film layer comprise a high phase change latent heat material.

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

3. The diaphragm according to claim 1 or 2, characterized in that: The volume of the high phase change latent heat material accounts for 10% to 48% of the pore volume of the aerogel film layer.

4. The diaphragm according to any one of claims 1 to 3, characterized in that: The pores of the aerogel film layer have a pore size of 100 nm to 230 nm.

5. The diaphragm according to any one of claims 1 to 4, characterized in that: The aerogel film layer includes at least one of polyimide aerogel and ceramic aerogel.

6. The diaphragm according to claim 5, characterized in that The ceramic aerogel includes an organosilicon-derived aerogel.

7. The diaphragm according to any one of claims 1 to 6, 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 .

8. The diaphragm according to any one of claims 1 to 7, characterized in that: The separator further comprises a coating layer, the coating layer being located on at least one side of the aerogel film layer; The coating comprises at least one of polyvinylidene fluoride, acrylic resin, polyurethane resin, aluminum oxide, boehmite, magnesium hydroxide and silicon oxide.

9. The diaphragm according to claim 8, characterized in that The thickness T of the coating is 0<T≤1 μm.

10. A method for preparing a diaphragm according to any one of claims 1 to 9, characterized in that: The preparation method comprises the following steps: Mixing the initial aerogel film layer with a high phase change latent heat material to obtain the separator including the aerogel film layer; Alternatively, the mixed system for preparing aerogel is mixed with a material with high phase change latent heat to obtain the separator including the aerogel film layer.

11. The preparation method according to claim 10, characterized in that: The high phase change latent heat material is paraffin and / or fatty acid, and the preparation method comprises: The initial aerogel film layer is immersed in a solution including the paraffin wax and / or the fatty acid to obtain the separator.

12. The preparation method according to claim 10, characterized in that: The high phase change latent heat material is a high phase change latent heat salt material, and the preparation method comprises: 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.

13. The preparation method according to any one of claims 10 to 12, characterized in that: The preparation method further comprises: The coating layer is disposed on at least one side of the aerogel film layer to obtain the separator.

14. A battery, characterized in that: The battery comprises the diaphragm according to any one of claims 1 to 9 or a diaphragm prepared by the method for preparing the diaphragm according to any one of claims 10 to 13.

15. An electrical equipment, characterized in that: The electrical device comprises the battery according to claim 14.

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