Diaphragm and preparation method thereof, battery and electric equipment

Abstract

The invention relates to the technical field of batteries, in particular to a diaphragm and a preparation method thereof, a battery and electric equipment. The separator includes: a backbone including crosslinked cellulose; the load particles are prepared by modifying a coupling agent; wherein the load particles are dispersed in the framework, and the mass ratio of the framework to the load particles is 100: (5-20); and the contact angle of the diaphragm is not greater than 35 degrees. The diaphragm provided by the invention has high electrolyte absorption rate, wettability, thermal stability and high capacity retention rate.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to a separator and its preparation method, a battery, and an electrical device. Background Technology

[0002] With the widespread application of lithium-ion batteries in electric vehicles, energy storage systems, and portable electronic devices, the requirements for battery performance are increasing. As a key component of lithium-ion batteries, the performance of the separator directly affects battery safety, cycle life, and energy density. Traditional polyolefin separators (such as PE and PP), while possessing good mechanical strength and chemical stability, suffer from poor electrolyte wettability and insufficient thermal stability, leading to severe performance degradation under high-rate charge / discharge or high-temperature environments. In recent years, researchers have focused on developing novel composite separators to overcome these shortcomings. Cellulose acetate, due to its excellent film-forming properties, good electrolyte affinity, and biodegradability, has become a potential candidate material for separators, but its thermal stability and ionic conductivity still need further improvement. Summary of the Invention

[0003] The purpose of this invention is to overcome the aforementioned problems in the prior art and provide a separator, its preparation method, a battery, and an electrical device. This separator exhibits high electrolyte absorption rate, low contact angle, and high ionic conductivity.

[0004] Inorganic materials generally possess high thermal conductivity and thermal stability, but they are difficult to form a continuous membrane structure when used alone. This invention constructs an organic-inorganic composite membrane consisting of loaded particles prepared by coupling agent modification and a cross-linked cellulose acetate skeleton, which maintains the membrane's high electrolyte absorption rate, low contact angle, and high ionic conductivity.

[0005] To achieve the objectives of this invention, a first aspect of this invention provides a diaphragm, comprising:

[0006] The framework includes cross-linked cellulose;

[0007] The supported particles were prepared by modification with a coupling agent.

[0008] The loaded particles are dispersed in the framework, and the mass ratio of the framework to the loaded particles is 100:(5-20).

[0009] The contact angle of the diaphragm is no greater than 35°.

[0010] A second aspect of the present invention provides a method for preparing a diaphragm, the method comprising:

[0011] S1. The suspension containing particles is contacted with the coupling agent hydrolysate, followed by solid-liquid separation, washing, and drying to obtain the loaded particles.

[0012] S2. The cellulose solution is premixed with a monomer containing a cross-linking agent, and then loaded particles are added and mixed to obtain a slurry.

[0013] S3. The slurry is coated and cross-linked to obtain a diaphragm.

[0014] A third aspect of the present invention provides a battery comprising the separator provided in the first aspect of the present invention; or, a separator prepared by the method for preparing the separator described in the second aspect of the present invention.

[0015] A fourth aspect of the present invention provides an electronic device comprising the battery provided in the third aspect of the present invention.

[0016] Through the above technical solution, the present invention uses a composite of loaded particles prepared by cross-linked cellulose skeleton and coupling agent modification. With the bridging effect of the coupling agent, it can ensure that the electrolyte fully wets the separator, which is conducive to the rapid transport of lithium ions and can significantly improve the high temperature resistance of the separator, thereby improving the rate performance of the battery. On the other hand, the introduction of loaded particles provides an additional lithium ion conduction path, further optimizing the kinetic and electrochemical performance of the battery. Detailed Implementation

[0017] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0018] [Septum]

[0019] The first aspect of the present invention provides a diaphragm, comprising:

[0020] The framework includes cross-linked cellulose;

[0021] The supported particles were prepared by modification with a coupling agent.

[0022] The loaded particles are dispersed in the framework, and the mass ratio of the framework to the loaded particles is 100:(5-20).

[0023] The contact angle of the diaphragm is no greater than 35°.

[0024] The present invention includes a skeleton constructed from cross-linked cellulose, and supports modified with coupling agent as a reinforcing phase, which enables the separator to have high lithium-ion conductivity and high temperature resistance. In addition, the battery containing the separator of the present invention has better kinetic and electrochemical performance.

[0025] The contact angle of the diaphragm in this invention refers to the contact angle between the diaphragm and the electrolyte at 25°C not exceeding 35°, for example, 10°, 12°, 15°, 17°, 19°, 23°, 25°, 30°, and 35°. The electrolyte is an organic solvent containing an electrolyte. In some embodiments, the organic solvent is a carbonate, specifically ethylene carbonate (EC) and dimethyl carbonate (DMC) in a mass ratio of 20:55. More specifically, in some embodiments, the electrolyte can be lithium hexafluorophosphate (LiPF6), ethylene carbonate (EC), dimethyl carbonate (DMC), fluoroethylene carbonate (FEC), ethylene sulfate (DTD), and vinylene carbonate (VC) in a mass ratio of 10.0:20.0:55.0:2.0:8.0:5.0. The contact angle of the diaphragm directly reflects the excellent wettability of the electrolyte to the diaphragm. Furthermore, in some embodiments, the diaphragm has a 10°-25° ellipse relative to the electrolyte at 25°C.

[0026] In this invention, controlling the mass ratio of the framework to the loaded particles to be 100:(5-20), for example, 100:5, 100:8, 100:10, 100:12, 100:15, 100:20, or any range of two of the above ratios, can better provide coordination sites for lithium ions, thereby improving lithium ion conduction efficiency and reducing the interface impedance of the battery containing the separator of this invention during cycling. This avoids the defect of local electric field distortion exacerbating lithium ion transport resistance, and thus better increases the battery capacity retention rate. Further, in some embodiments, the preferred mass ratio of the framework to the loaded particles is 100:(5-15).

[0027] According to the present invention, cross-linked cellulose refers to a polymeric material in which cross-linking bonds are introduced between cellulose molecular chains to form a cross-linked three-dimensional network structure. In some embodiments, cross-linked cellulose includes cross-linked cellulose acetate. That is, cross-linking bonds are introduced between cellulose acetate molecular chains to form cross-linked cellulose acetate with a cross-linked three-dimensional network structure.

[0028] The use of cross-linked cellulose acetate in this invention can more effectively increase the lithium-ion conductivity of the separator and the capacity cycle performance of the battery containing the separator of this invention.

[0029] According to some embodiments of the present invention, the crosslinked cellulose contains crosslinked structural units provided by a crosslinking agent and cellulose acetate structural units provided by cellulose acetate. That is, it is capable of crosslinking cellulose acetate.

[0030] The cross-linked cellulose containing the above-mentioned structural units in this invention can better increase the thermal shrinkage rate of the separator at high temperatures, increase the effective pore connectivity and ion transport path of the separator, and thus effectively increase the lithium-ion conductivity of the separator and the capacity cycle performance of the battery containing the separator of this invention.

[0031] According to the present invention, in some embodiments, the mass ratio of crosslinked structural units to cellulose acetate structural units is 1:(5-15), for example 1:5, 1:8, 1:10, 1:12, 1:15, or any range of two of the above ratios, preferably 1:(8-12).

[0032] In this invention, the content of each structural unit in cross-linked cellulose corresponds to the amount of each monomer raw material used in the preparation of cross-linked cellulose.

[0033] This invention reveals that when the number of cross-linking structural units is too low or too high, the ionic conductivity of the separator and the cycle performance of the battery containing the separator deteriorate simultaneously. The reason for this is that when the number of cross-linking structural units is too low, the density of cross-linking points between the cellulose acetate molecular chains is insufficient, leading to a loose three-dimensional network structure. On the one hand, this intensifies molecular chain movement at high temperatures, significantly increasing the thermal shrinkage rate. On the other hand, excessive swelling, while artificially inflating the apparent liquid absorption rate of the separator, reduces the actual effective pore connectivity, resulting in a tortuous ion transport path. When the number of cross-linking structural units is too high, the overly dense cross-linked network severely compresses the pore space, hindering electrolyte wetting and causing a sharp drop in conductivity due to blockage of ion migration channels. Simultaneously, the rigid network is more prone to brittle fracture under thermal stress, leading to an abnormally high shrinkage rate. This invention controls the mass ratio of cross-linking structural units to cellulose acetate structural units within the aforementioned range, especially within the preferred range, to achieve a moderately dense three-dimensional network structure, thereby resulting in superior overall separator performance.

[0034] According to the present invention, in some embodiments, the crosslinking agent comprises a polybasic acid containing at least two carboxyl groups.

[0035] In this invention, a polybasic acid containing at least two carboxyl groups undergoes a condensation and cross-linking reaction with the hydroxyl groups in cellulose acetate to obtain cross-linked cellulose acetate containing cross-linked structural units and cellulose acetate structural units. The membrane obtained using the above-mentioned cross-linking agent in this invention can form a dense cross-linked network, better constructing ion migration channels and thus better increasing lithium-ion conductivity.

[0036] According to the present invention, in some embodiments, the polybasic acid containing two carboxyl groups includes one or more of oxalic acid, malic acid, citric acid, hydroxysuccinic acid, and dihydroxysuccinic acid. Citric acid is used as an example to illustrate the advantages of the present invention, but this does not constitute a limitation thereof.

[0037] According to the present invention, the specific type of cellulose acetate is not particularly limited as long as the purpose of the invention can be achieved. Depending on the degree to which the hydroxyl groups in the cellulose are replaced by acetyl groups, in some embodiments, cellulose acetate includes at least one of cellulose monoacetate, cellulose diacetate, and cellulose triacetate. Cellulose diacetate is used as an example to illustrate the advantages of the invention, but this does not constitute a limitation on the invention.

[0038] According to the present invention, in some embodiments, the cross-linked cellulose further contains imidazole structural units provided by 1-hydroxyethyl-3-methylimidazolium salt.

[0039] In this invention, it was found that when the above-mentioned imidazole structural units are introduced into cross-linked cellulose, i.e. cross-linked cellulose acetate, the cross-linked cellulose acetate and the loaded particles can better increase the lithium-ion conductivity of the separator, as well as the lithium-ion conductivity and other properties of the battery containing the separator of this invention.

[0040] According to the present invention, in some embodiments, the 1-hydroxyethyl-3-methylimidazolium salt preferably includes at least one of 1-hydroxyethyl-3-methylimidazolium chloride, 1-hydroxyethyl-3-methylimidazolium tetrafluoroborate, 1-hydroxyethyl-3-methylimidazolium hexafluorophosphate, 1-hydroxyethyl-3-methylimidazolium trifluoromethanesulfonate, and 1-hydroxyethyl-3-methylimidazolium acetate, and preferably includes 1-hydroxyethyl-3-methylimidazolium trifluoromethanesulfonate and / or 1-hydroxyethyl-3-methylimidazolium hexafluorophosphate.

[0041] In this invention, the imidazole structural unit provided by the above-mentioned 1-hydroxyethyl-3-methylimidazolium salt is present in cross-linked cellulose acetate, which can better increase the lithium-ion conductivity of the separator and the lithium-ion conductivity and other properties of the battery containing the separator of this invention.

[0042] According to the present invention, in some embodiments, the mass ratio of imidazole structural units to crosslinked structural units is preferably 1:(5-8), for example 1:5, 1:6, 1:7, 1:8.

[0043] In this invention, by controlling the mass ratio of imidazole structural units to crosslinked structural units within the above-mentioned range, the lithium-ion conductivity of the separator and the lithium-ion conductivity and other properties of the battery containing the separator of this invention can be better increased.

[0044] According to the present invention, in some embodiments, the coupling agent includes a silane coupling agent.

[0045] The loaded particles prepared by using silane coupling agent modification in this invention can be stably connected with the framework, thereby effectively constructing a stable organic-inorganic three-dimensional network structure and better increasing the stability of the membrane.

[0046] According to the present invention, in some embodiments, the silane coupling agent includes an amino-containing silane coupling agent.

[0047] The study found that the use of amino-containing silane coupling agents in this invention can better increase the lithium-ion conductivity of the membrane. The reason is that the amino groups on the surface of the loaded particles can better provide lithium-ion coordination sites, thereby increasing the ion conduction efficiency.

[0048] According to the present invention, in some embodiments, the general molecular formula of the amino-containing silane coupling agent is (RO)3Si-(CH2)3-NH2, wherein R is a C1-C4 alkyl group (e.g., methyl or ethyl).

[0049] According to the present invention, in some embodiments, the supported particles include hydroxyapatite modified with a coupling agent, that is, hydroxyapatite is prepared by modification with a coupling agent.

[0050] Hydroxyapatite (HA) is a biocompatible inorganic material dispersed in a framework including cross-linked cellulose, which can provide additional lithium-ion conduction pathways, further optimizing the kinetic and electrochemical performance of the battery.

[0051] According to some embodiments of the present invention, the mass content of the coupling agent is 0.5%-5% based on the total mass of the loaded particles, for example, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.5%, 3%, 4%, 5%, or any range of two of the above values.

[0052] According to the present invention, in some embodiments, the Dv50 particle size of the loaded particles is 20nm-100nm, for example, 20nm, 30nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, or any range of two of the above values.

[0053] In this invention, controlling the Dv50 particle size of the loaded particles within the above-mentioned range can better increase the lithium-ion conductivity and cycle stability of the separator.

[0054] According to the present invention, the thickness of the diaphragm can be selected as needed, and in some embodiments, the thickness of the diaphragm is 15μm-50μm.

[0055] The diaphragm in this invention has an excellent electrolyte absorption rate. In some embodiments, the electrolyte absorption rate of the diaphragm is ≥200%, preferably 250%-300%, for example 250%, 280%, 285%, 290%, 295% or 300%.

[0056] The diaphragm in this invention has excellent ionic conductivity. In some embodiments, the lithium-ion conductivity of the diaphragm at 25°C is ≥1.7 mS / cm, preferably 2.5 mS / cm-3.5 mS / cm, for example 2.5 mS / cm, 2.65 mS / cm, 2.7 mS / cm, 2.8 mS / cm, 2.9 mS / cm, 3 mS / cm, 3.25 mS / cm or 3.5 mS / cm.

[0057] The membrane of this invention has excellent heat resistance. In some embodiments, after heat treatment at 180°C for 1 hour, the longitudinal shrinkage rate is ≤3.5% and the transverse shrinkage rate is ≤2.8%.

[0058] [Membrane Preparation Method]

[0059] According to the present invention, the membrane can be prepared by crosslinking a raw material comprising cellulose, a monomer containing a crosslinking agent, and a coupling agent-modified loaded particle in a crosslinking system. As an example, the corresponding membrane can be prepared according to the preparation method provided in the second aspect of the present invention.

[0060] According to some embodiments of the present invention, a second aspect of the present invention provides a method for preparing a diaphragm, the method comprising:

[0061] S1. The suspension containing particles is contacted with the coupling agent hydrolysate, followed by solid-liquid separation, washing, and drying to obtain the loaded particles.

[0062] S2. The cellulose solution is premixed with a monomer containing a cross-linking agent, and then loaded particles are added and mixed to obtain a slurry.

[0063] S3. The slurry is coated and cross-linked to obtain a diaphragm.

[0064] It should be understood that all the features and advantages described above regarding the "diaphragm" also apply to the "method for preparing the diaphragm," and will not be repeated here.

[0065] The membrane prepared by the above-described preparation method of the present invention has excellent ionic conductivity and cycling stability due to the interaction between the cross-linked cellulose backbone and the loaded particles dispersed in the backbone.

[0066] In this invention, the particulate suspension refers to a suspension formed by dispersing particles in a solvent. As long as the purpose of this invention can be achieved, the type of solvent in the suspension is not particularly limited. In some embodiments, the solvent in the particulate suspension includes alcohol solvents, preferably alkyl alcohol solvents. Examples of alkyl alcohol solvents include C1-C4 alkyl alcohol solvents, such as methanol and ethanol. In this invention, ethanol is used as an example to illustrate the advantages of this invention.

[0067] The specific content of particles in the suspension containing particles in this invention is not particularly limited, as long as the coupling agent can better modify the particles. In some embodiments, the mass content of particles in the suspension is 20%-40%.

[0068] According to the present invention, in order to make the particles in the suspension more uniformly dispersed, the particles can be mixed with a corresponding solvent and then ball-milled to obtain a suspension containing particles.

[0069] As an example, hydroxyapatite was mixed with anhydrous ethanol and ball-milled at 200 rpm-500 rpm for 3-5 hours to obtain a suspension containing hydroxyapatite.

[0070] According to the present invention, the coupling agent hydrolysate refers to a solution obtained by hydrolyzing the coupling agent in a solvent including water. In some embodiments, the preparation method of the coupling agent hydrolysate includes: dissolving the coupling agent in a mixed solvent of ethanol and water, and then adjusting the pH of the system to 4-5 using a pH adjuster for hydrolysis; wherein, preferably, the mass of the coupling agent is 1%-10% of the mass of the mixed solvent, and preferably the volume ratio of ethanol to water is (3-6):1; the pH adjuster may be a pH adjuster in the art, including but not limited to acetic acid.

[0071] As an example, the preparation method of the coupling agent hydrolysate includes: dissolving the coupling agent in ethanol and deionized water at a volume ratio of (3-6):1, then adjusting the pH of the system to 4-5 using a pH adjuster, and hydrolyzing for 20-50 minutes.

[0072] According to the present invention, in some embodiments, the particles comprise hydroxyapatite. That is, the loaded particles prepared in step S1 are coupling agent-modified hydroxyapatite.

[0073] According to the present invention, in some embodiments, the Dv50 particle size of the particles is 20nm-100nm.

[0074] According to the present invention, in some embodiments, the coupling agent includes a silane coupling agent, preferably an amino-containing silane coupling agent.

[0075] According to the present invention, in some embodiments, the preferred amino-containing silane coupling agent has the general molecular formula (RO)3Si-(CH2)3-NH2, wherein R is a C1-C4 alkyl group (e.g., methyl or ethyl).

[0076] According to the present invention, in step S1, the mass ratio of the particles in the suspension containing particles to the coupling agent providing the coupling agent hydrolysate is 100:(8-15), for example, 100:8, 100:10, 100:12 or 100:15.

[0077] According to the present invention, in order to enable the coupling agent to fully modify the particles, such as hydroxyapatite, in some embodiments, the contact method in step S1 includes: adding the coupling agent hydrolysate dropwise to the suspension containing the particles, and after the coupling agent hydrolysate is added, continuing the reaction for 1-3 hours to achieve contact. The dropwise addition method is a conventional method in the art and will not be described in detail.

[0078] According to the present invention, in step S1, the solid-liquid separation method can be a conventional method in the art, such as filtration, centrifugation, etc.

[0079] According to the present invention, in step S1, the washing method can be a conventional method in the art, such as washing with ethanol. In some embodiments, the washing endpoint is preferably: the conductivity of the washing liquid is <5 μS / cm.

[0080] According to the present invention, in step S1, the drying method can be a conventional method in the art. Drying can be carried out under normal pressure or under vacuum conditions. In order to dry more thoroughly, vacuum drying can be carried out by using a staged heating method under vacuum conditions. In some embodiments, vacuum drying is carried out at 35-45°C for 1.5h-2.5h, followed by vacuum drying at 55-65°C for 0.5h-1.5h, and finally vacuum drying at 75-85°C for 0.1h-0.5h.

[0081] In some embodiments of the present invention, the cellulose in the cellulose solution includes cellulose acetate.

[0082] According to some embodiments of the present invention, cellulose acetate includes at least one of cellulose monoacetate, cellulose diacetate, and cellulose triacetate.

[0083] According to the present invention, in some embodiments, the crosslinking agent comprises a polybasic acid containing at least two carboxyl groups, preferably including one or more of oxalic acid, malic acid, citric acid, hydroxysuccinic acid, and dihydroxysuccinic acid. To avoid the influence of water on crosslinking, the crosslinking agent is often present in an anhydrous form, such as anhydrous citric acid.

[0084] According to the present invention, in some embodiments, the monomer further includes a 1-hydroxyethyl-3-methylimidazolium salt.

[0085] According to the present invention, in some embodiments, the 1-hydroxyethyl-3-methylimidazolium salt preferably includes at least one of 1-hydroxyethyl-3-methylimidazolium chloride, 1-hydroxyethyl-3-methylimidazolium tetrafluoroborate, 1-hydroxyethyl-3-methylimidazolium hexafluorophosphate, 1-hydroxyethyl-3-methylimidazolium trifluoromethane sulfonate, and 1-hydroxyethyl-3-methylimidazolium acetate.

[0086] According to the present invention, in some embodiments, the mass ratio of 1-hydroxyethyl-3-methylimidazolium salt to crosslinking agent is preferably 1:(5-8).

[0087] According to the present invention, in some embodiments, the mass ratio of crosslinking agent to cellulose (e.g., cellulose acetate) is 1:(5-15), preferably 1:(8-12).

[0088] According to the present invention, in some embodiments, the total mass ratio of the crosslinking agent and cellulose to the mass ratio of the responsible particles is 100:(5-20), preferably 100:(5-15).

[0089] According to the present invention, a cellulose solution refers to a cellulose solution formed by dissolving cellulose in a corresponding solvent, wherein the main function of the solvent is to dissolve cellulose. As long as the purpose of the present invention can be achieved, there is no special limitation on the type of solvent. In some embodiments, it is preferred that in step S2, the solvent in the cellulose solution includes, but is not limited to, at least one of dimethylformamide (DMF), dimethylacetamide, dimethyl sulfoxide (DMSO), and chloroform.

[0090] According to some embodiments of the present invention, the cellulose content in the cellulose solution is 15%-20% by mass.

[0091] In this invention, cellulose is dissolved in a solvent to obtain a cellulose solution. To better form a cellulose solution, the dissolution can be carried out at a certain temperature, for example, at 50-70°C.

[0092] According to the present invention, in order to avoid the influence of air on the aforementioned mixing, the premixing in step S2 can be carried out under the protection of an inert gas (e.g., nitrogen). In some embodiments, the premixing conditions in step S2 include: being carried out under the protection of an inert gas, at a temperature of 50-70°C, and for a time of 20-40 minutes.

[0093] According to the present invention, ultrasonic dispersion can be used to make the load more uniformly dispersed in the system. In some embodiments, in step S2, the mixing conditions include mixing for 15-50 minutes under ultrasonic conditions at a temperature of 50-70°C and a power of 400-800W.

[0094] As an example, cellulose acetate is dissolved in DMF at 50-70°C and stirred for 1-3 hours. Then, a crosslinking agent is added and the mixture is stirred at 50-70°C for 20-40 minutes under nitrogen protection. Finally, hydroxyapatite modified with a coupling agent is added and ultrasonically dispersed at 50-70°C (power 500-800W, 15-50 minutes) to obtain a homogeneous slurry.

[0095] As an example, cellulose acetate is dissolved in DMF at 50-70°C and stirred for 1-3 hours. Then, a crosslinking agent and 1-hydroxyethyl-3-methylimidazolium salt are added. Under nitrogen protection, the mixture is stirred at 50-70°C for 20-40 minutes. The hydroxyapatite modified with the coupling agent is ultrasonically dispersed at 50-70°C (power 500-800W, 15-50 minutes) to obtain a homogeneous slurry.

[0096] According to the present invention, the coating method in step S3 can be a method commonly used in the art, such as using a casting coating method, and the present invention has no special limitation thereto.

[0097] According to some embodiments of the present invention, in step S3, the conditions for the crosslinking reaction include: a temperature of 130-160°C and a time of 20-50 min.

[0098] After the crosslinking reaction is completed in step S3 of this invention, the membrane can be obtained by peeling and winding it up.

[0099] [Battery]

[0100] The separator in this invention can be used in batteries to improve the cycle performance of batteries. Based on this, in some embodiments, the third aspect of this invention provides a battery including the separator provided in the first aspect of this invention; or, the separator prepared by the method for preparing the separator described in the second aspect of this invention.

[0101] The materials and preparation methods of the batteries described in this invention, except for the separator, can all be carried out in accordance with the practices in this field, and can all achieve the effect of improving battery cycle performance.

[0102] According to the present invention, in some embodiments, the battery is preferably a lithium-ion battery; the battery can be a prismatic battery, a pouch battery, a cylindrical battery, etc., and can take different forms such as a battery cell, a battery module, or a battery pack.

[0103] According to some embodiments of the present invention, the N / P ratio of the battery design can be 1.02-1.12.

[0104] According to some embodiments of the present invention, the battery further includes a positive electrode, a negative electrode, and an electrolyte.

[0105] According to the present invention, the positive electrode sheet can be a conventional positive electrode sheet in the art. For example, the positive electrode sheet includes a positive current collector and a positive active material layer coated on one or both surfaces of the positive current collector; wherein, the positive active material layer may include a positive active material, a conductive agent and a binder.

[0106] According to the present invention, in some embodiments, the mass ratio of positive electrode active material, conductive agent and binder in the positive electrode active material layer is (94-96):(1-3):(1-3).

[0107] According to the present invention, in some embodiments, the positive electrode active material includes lithium nickel cobalt aluminum oxide (LiNi). 0.8 Co 0.15 Al 0.05 A composite of O2 and lithium-rich manganese-based material (xLi2MnO3·(1-x)LiMO2), where 0.1≤x≤0.3 and M is two elements from Mn, Ni and Co.

[0108] According to the present invention, in some embodiments, the conductive agent in the positive electrode active material layer may be a combination of carbon nanotubes (CNTs) and Ketjen Black (KB).

[0109] According to the present invention, in some embodiments, the binder in the positive electrode active material layer may be polyvinylidene fluoride (PVDF).

[0110] In this invention, a positive electrode slurry can be made from a positive electrode active material, a conductive agent, a binder, and a solvent. This slurry is then coated onto one or both sides of the positive electrode current collector, and subsequently dried and cold-pressed to obtain a positive electrode sheet.

[0111] According to the present invention, the negative electrode sheet in the battery can be a conventional negative electrode sheet in the art. For example, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on one or both surfaces of the negative electrode current collector. The negative electrode active material layer may include a negative electrode active material, a conductive agent, and a binder.

[0112] According to some embodiments of the present invention, the mass ratio of negative electrode active material, conductive agent, binder and thickener in the negative electrode active material layer is (95-96.5):(1-2):(1-2):(0.5-1.5).

[0113] According to the present invention, in some embodiments, the negative electrode active material includes at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon oxide, pre-lithium silicon oxide, silicon carbon material and deposited silicon carbon.

[0114] According to the present invention, in some embodiments, the conductive agent in the negative electrode active material layer may be carbon nanotubes; in some embodiments, the binder in the negative electrode active material layer may be polyacrylic acid (PAA); in some embodiments, the thickener in the negative electrode active material layer may be sodium carboxymethyl cellulose (CMC).

[0115] In this invention, a positive electrode slurry can be made by mixing a negative electrode active material, a conductive agent, a binder, and a thickener with water. This slurry is then coated onto one or both sides of the negative electrode current collector, and subsequently dried and cold-pressed to obtain a positive electrode sheet.

[0116] According to the present invention, in some embodiments, the electrolyte is a lithium-ion electrolyte.

[0117] According to some embodiments of the present invention, the electrolyte may be lithium hexafluorophosphate (LiPF6), ethylene carbonate (EC), dimethyl carbonate (DMC), fluoroethylene carbonate (FEC), ethylene sulfate (DTD), and vinylene carbonate (VC) in a mass ratio of 10.0:20.0:55.0:2.0:8.0:5.0.

[0118] [Electronic Devices]

[0119] According to some embodiments of the present invention, a fourth aspect of the present invention provides an electronic device including a battery provided by the fourth aspect of the present invention.

[0120] The electronic devices in this invention can be terminal consumer products or 3C electronic products, communication products or consumer electronic products, such as mobile phones, power banks, laptops, tablet computers, e-readers, laptops, digital cameras, in-vehicle equipment, wearable devices, headphones and other devices.

[0121] In the context of this specification, including the following embodiments and comparative examples, tests were conducted as follows:

[0122] During testing, the electrolyte was prepared by mixing lithium hexafluorophosphate (LiPF6), ethylene carbonate (EC), dimethyl carbonate (DMC), fluoroethylene carbonate (FEC), ethylene sulfate (DTD), and vinylene carbonate (VC) in a mass ratio of 10.0:20.0:55.0:2.0:8.0:5.0.

[0123] Method for determining the electrolyte absorption rate of the diaphragm:

[0124] Cut the diaphragm into small circular pieces with a diameter of 14 mm, immerse them in the electrolyte until the mass no longer changes, and measure the mass before and after immersion. The mass before immersion is recorded as M1, and the mass after immersion is recorded as M2. The liquid absorption rate is calculated as (M2-M1) / M1×100%.

[0125] Methods for determining lithium-ion conductivity:

[0126] (1) Sample preparation: Immerse the prepared diaphragm in the electrolyte for at least 12 hours to ensure it is fully wetted.

[0127] (2) Assemble a symmetrical cell: In an inert atmosphere (such as a glove box), two stainless steel electrodes (SS) are sandwiched with a membrane that has been wetted with electrolyte to form an SS|membrane|SS symmetrical structure, which is an impedance testing device with "no active electrode".

[0128] (3) Test equipment and parameters: Use an electrochemical workstation to perform AC impedance testing (EIS). The test conditions are as follows: frequency range: 1MHz~0.1Hz, AC disturbance voltage: 5~10mV, test temperature: 60℃ (temperature can be controlled by a constant temperature chamber).

[0129] Formula for calculating lithium-ion conductivity:

[0130] Where: σ is the ionic conductivity (S / cm), L is the membrane thickness (cm), R is the high-frequency semicircular intercept in the Nyquist plot (Ω), and A is the effective area of ​​the peripheral electrode (cm²). 2 ).

[0131] Method for determining the contact angle of the diaphragm with the electrolyte:

[0132] A micro-electrolyte (EC:DMC = 1:1) of 2-5 μL was dropped onto the treated and cleaned diaphragm surface using a micro-syringe. A side view image of the droplet was taken, and the droplet profile was fitted using software (such as the Young-Laplace equation or ellipse fitting method). The contact angle was calculated after the baseline was automatically detected.

[0133] Method for determining the heat shrinkage rate of diaphragms:

[0134] Cut the diaphragm into rectangular samples of 10mm × 100mm; lay the sample flat between A4 paper to prevent high-temperature curling, place it in an oven with a temperature control accuracy of ±1℃, set the temperature to 180℃, heat for 1 hour without external force, and then cool to room temperature; use a vernier caliper (accuracy 0.01mm) or laser rangefinder to measure the initial length L0 and the length L1 after heating, respectively, and calculate the shrinkage rate according to the formula (L0-L1) / L0×100%. Three samples need to be tested in each direction and the average value is taken. If the deviation exceeds 5%, it needs to be retested.

[0135] Cyclic performance testing methods:

[0136] The lithium-ion battery was placed in a 25°C constant temperature chamber for 6 hours and tested according to the following steps:

[0137] (1) First round of constant current and constant voltage charging: Charge at a constant current of 0.1C to 4.2V, then switch to constant voltage charging until the current drops to 0.1C;

[0138] (2) Let it stand for 30 minutes after charging is complete;

[0139] (3) Perform constant current discharge, discharging to 2.5V at a rate of 0.1C;

[0140] (4) Cyclic charge and discharge process: Charge at a constant current rate of 1.5C to 4.2V. Let stand for 30 minutes again, then discharge at a constant current rate of 5C to 2.5V;

[0141] (5) Repeat the above charging and discharging process for a total of 600 cycles.

[0142] Statistical analysis of the battery discharge capacity Q1 and Q after 1 cycle and 600 cycles. 600 Statistical analysis of battery capacity retention rate: Q 600 / Q1×100%.

[0143] The present invention will be further described in detail below with reference to specific embodiments. These embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0144] Example 1

[0145] Production of positive electrode plates:

[0146] Lithium nickel cobalt aluminum oxide (LiNi) 0.8 Co 0.15 Al 0.05 O2) and lithium-rich manganese-based (0.2Li2MnO3·0.8LiMn) 0.6 Ni 0.3 Co 0.1 O2 was mixed at a mass ratio of 7:3 as the active material, carbon nanotubes (CNTs) and Ketjen black (KB) were mixed at a mass ratio of 2:1 as the conductive agent, and polyvinylidene fluoride (PVDF) was used as the binder. The active material: conductive agent: binder was mixed at a mass ratio of 95.5:2.5:2.0, followed by the addition of N-methylpyrrolidone (NMP), and the mixture was stirred and thoroughly mixed to form a stable positive electrode slurry with a solid content of 70 wt%. The positive electrode slurry was then uniformly coated onto a 12 μm aluminum foil as the positive electrode current collector, and after drying and cold pressing, a positive electrode sheet was obtained with a compaction density of 3.4 g / cm³. 3 .

[0147] Production of negative electrode plates:

[0148] Artificial graphite, silicon carbide material, conductive carbon nanotubes, thickener sodium carboxymethyl cellulose (CMC), and binder polyacrylic acid (PAA) were mixed in a mass ratio of 81:15:1.5:1:1.5. Deionized water was then added and the mixture was stirred to form a uniform and stable negative electrode slurry with a solid content of 40 wt%. The negative electrode slurry was uniformly coated onto an 8 μm thick copper foil as the negative electrode current collector. After drying and cold pressing, the negative electrode sheet was obtained with a compaction density of 1.6 g / cm³. 3 .

[0149] Electrolyte preparation:

[0150] An electrolyte was prepared by mixing lithium hexafluorophosphate (LiPF6), ethylene carbonate (EC), dimethyl carbonate (DMC), fluoroethylene carbonate (FEC), ethylene sulfate (DTD), and vinylene carbonate (VC) in a mass ratio of 10.0:20.0:55.0:2.0:8.0:5.0.

[0151] Preparation of the diaphragm:

[0152] Mix 100g of hydroxyapatite (Dv50=50nm) with 300mL of anhydrous ethanol and ball mill for 4 hours (300rpm) to obtain a suspension.

[0153] 12g of KH-550 coupling agent was dissolved in a solvent (180mL ethanol and 48mL deionized water), then the pH was adjusted to 4.5 with acetic acid, and finally hydrolyzed for 30min to obtain the coupling agent hydrolysate.

[0154] The hydrolysate of the coupling agent was added dropwise to the suspension (stirred at a constant speed at 60°C), and centrifuged after reacting for 2 hours. The solid phase was washed three times with ethanol until the conductivity was <5 μS / cm. Then, it was vacuum dried sequentially at 40°C for 2 hours, at 60°C for 1 hour, and at 80°C for 0.5 hours to obtain the coupling agent-modified hydroxyapatite. The mass content of the coupling agent in the hydroxyapatite was 2.5%.

[0155] At 60°C, cellulose diacetate was dissolved in DMF, with cellulose diacetate accounting for 20 wt% of the solution mass. The mixture was mechanically stirred for 2 hours. Then, 1 / 10 of the mass of cellulose diacetate and dehydrated citric acid were added. The mixture was mixed at 60°C for 30 min under nitrogen protection. Finally, 10% of the total mass of cellulose diacetate and dehydrated citric acid was added. The mixture was ultrasonically dispersed at 60°C (600 W power, 30 min) to obtain a homogeneous slurry.

[0156] The homogeneous slurry was cast and coated (wet film thickness 500 μm), then dried with hot air at 140 °C for 30 min to initiate cross-linking, and finally peeled and wound up to obtain a diaphragm (thickness 25 ± 2 μm).

[0157] Assembly of lithium-ion batteries:

[0158] The positive and negative electrode sheets are rolled and slit separately, and then wound together with the separator to obtain a 21700 cylindrical battery core. The battery core is then welded to the connecting piece and installed into the battery casing. After completing the liquid injection, sealing and formation processes, a lithium-ion battery is obtained. The casing of the lithium-ion battery is cylindrical with dimensions of 21.0 mm in diameter and 70.0 mm in length.

[0159] The electrolyte absorption rate, lithium-ion conductivity, contact angle with electrolyte, longitudinal shrinkage rate, and transverse shrinkage rate of the separator, as well as the capacity retention rate of the lithium-ion battery, are shown in Table 1.

[0160] Example 2

[0161] The method according to Example 1 differs in that:

[0162] Add 1 / 8 of the weight of dehydrated citric acid from cellulose diacetate;

[0163] The rest is the same as in Example 1, and the separator and the corresponding lithium-ion battery are finally prepared.

[0164] The electrolyte absorption rate, lithium-ion conductivity, contact angle with electrolyte, longitudinal shrinkage rate, and transverse shrinkage rate of the separator, as well as the capacity retention rate of the lithium-ion battery, are shown in Table 1.

[0165] Example 3

[0166] The method according to Example 1 differs in that:

[0167] Add 1 / 12 of the weight of dehydrated citric acid from cellulose diacetate;

[0168] The rest is the same as in Example 1, and the separator and the corresponding lithium-ion battery are finally prepared.

[0169] The electrolyte absorption rate, lithium-ion conductivity, contact angle with electrolyte, longitudinal shrinkage rate, and transverse shrinkage rate of the separator, as well as the capacity retention rate of the lithium-ion battery, are shown in Table 1.

[0170] Example 4

[0171] The method according to Example 1 differs in that:

[0172] Hydroxyapatite modified with a coupling agent comprising 5% by weight of cellulose diacetate and dehydrated citric acid crosslinking agent;

[0173] The rest is the same as in Example 1, and the separator and the corresponding lithium-ion battery are finally prepared.

[0174] The electrolyte absorption rate, lithium-ion conductivity, contact angle with electrolyte, longitudinal shrinkage rate, and transverse shrinkage rate of the separator, as well as the capacity retention rate of the lithium-ion battery, are shown in Table 1.

[0175] Example 5

[0176] The method according to Example 1 differs in that:

[0177] Hydroxyapatite modified with a coupling agent comprising 15% by weight of cellulose diacetate and dehydrated citric acid crosslinking agent;

[0178] The rest is the same as in Example 1, and the separator and the corresponding lithium-ion battery are finally prepared.

[0179] The electrolyte absorption rate, lithium-ion conductivity, contact angle with electrolyte, longitudinal shrinkage rate, and transverse shrinkage rate of the separator, as well as the capacity retention rate of the lithium-ion battery, are shown in Table 1.

[0180] Example 6

[0181] The method according to Example 1 differs in that:

[0182] Add dehydrated citric acid at a weight of 1 / 5 that of cellulose diacetate;

[0183] The rest is the same as in Example 1, and the separator and the corresponding lithium-ion battery are finally prepared.

[0184] The electrolyte absorption rate, lithium-ion conductivity, contact angle with electrolyte, longitudinal shrinkage rate, and transverse shrinkage rate of the separator, as well as the capacity retention rate of the lithium-ion battery, are shown in Table 1.

[0185] Example 7

[0186] The method according to Example 1 differs in that:

[0187] Add 1 / 13 of the weight of dehydrated citric acid from cellulose diacetate;

[0188] The rest is the same as in Example 1, and the separator and the corresponding lithium-ion battery are finally prepared.

[0189] The electrolyte absorption rate, lithium-ion conductivity, contact angle with electrolyte, longitudinal shrinkage rate, and transverse shrinkage rate of the separator, as well as the capacity retention rate of the lithium-ion battery, are shown in Table 1.

[0190] Example 8

[0191] The method according to Example 1 differs in that:

[0192] Hydroxyapatite modified with a coupling agent comprising 20% ​​by weight of cellulose diacetate and dehydrated citric acid crosslinking agent;

[0193] The rest is the same as in Example 1, and the separator and the corresponding lithium-ion battery are finally prepared.

[0194] The electrolyte absorption rate, lithium-ion conductivity, contact angle with electrolyte, longitudinal shrinkage rate, and transverse shrinkage rate of the separator, as well as the capacity retention rate of the lithium-ion battery, are shown in Table 1.

[0195] Example 9

[0196] The method according to Example 1 differs in that:

[0197] Replace KH-550 coupling agent with KH-560 coupling agent.

[0198] The rest is the same as in Example 1, and the separator and the corresponding lithium-ion battery are finally prepared.

[0199] The electrolyte absorption rate, lithium-ion conductivity, contact angle with electrolyte, longitudinal shrinkage rate, and transverse shrinkage rate of the separator, as well as the capacity retention rate of the lithium-ion battery, are shown in Table 1.

[0200] Example 10

[0201] The method according to Example 1 differs in that:

[0202] At 60°C, cellulose diacetate was dissolved in DMF, with cellulose diacetate accounting for 20 wt% of the solution mass. The mixture was mechanically stirred for 2 hours. Then, 1 / 10 of the mass of cellulose diacetate, dehydrated citric acid, and 1-hydroxyethyl-3-methylimidazolium trifluoromethane sulfonate (mass ratio of dehydrated citric acid to 1-hydroxyethyl-3-methylimidazolium trifluoromethane sulfonate was added. The mixture was stirred at 60°C for 30 min under nitrogen protection. Finally, 10% of the total mass of cellulose diacetate, dehydrated citric acid, and 1-hydroxyethyl-3-methylimidazolium trifluoromethane sulfonate, modified hydroxyapatite with coupling agent was added. The mixture was ultrasonically dispersed at 60°C (600 W power, 30 min) to obtain a homogeneous slurry.

[0203] The rest is the same as in Example 1, and the separator and the corresponding lithium-ion battery are finally prepared.

[0204] The electrolyte absorption rate, lithium-ion conductivity, contact angle with electrolyte, longitudinal shrinkage rate, and transverse shrinkage rate of the separator, as well as the capacity retention rate of the lithium-ion battery, are shown in Table 1.

[0205] Example 11

[0206] The method according to Example 1 differs in that:

[0207] At 60°C, cellulose diacetate was dissolved in DMF, with cellulose diacetate accounting for 20 wt% of the solution mass. The mixture was mechanically stirred for 2 hours. Then, 1 / 10 of the mass of cellulose diacetate, dehydrated citric acid, and 1-hydroxyethyl-3-methylimidazolium hexafluorophosphate (mass ratio of dehydrated citric acid to 1-hydroxyethyl-3-methylimidazolium hexafluorophosphate was added. The mixture was then mixed at 60°C for 30 min under nitrogen protection. Finally, 10% of the total mass of cellulose diacetate, dehydrated citric acid, and 1-hydroxyethyl-3-methylimidazolium hexafluorophosphate, modified with a coupling agent, was added. The mixture was ultrasonically dispersed at 60°C (600 W power, 30 min) to obtain a homogeneous slurry.

[0208] The rest is the same as in Example 1, and the separator and the corresponding lithium-ion battery are finally prepared.

[0209] The electrolyte absorption rate, lithium-ion conductivity, contact angle with electrolyte, longitudinal shrinkage rate, and transverse shrinkage rate of the separator, as well as the capacity retention rate of the lithium-ion battery, are shown in Table 1.

[0210] Comparative Example 1

[0211] The method according to Example 1 differs in that:

[0212] Preparation of the diaphragm:

[0213] At 60°C, cellulose diacetate was dissolved in DMF, with cellulose diacetate accounting for 20 wt% of the solution mass. The mixture was mechanically stirred for 2 hours, and then 1 / 10 of the mass of dehydrated citric acid was added. Under nitrogen protection, the mixture was mixed at 60°C for 30 min. The mixture was then cast and coated, followed by hot air drying at 140°C for 30 min to initiate cross-linking. Finally, the membrane was peeled off and wound up to obtain a membrane (thickness 25 ± 2 μm).

[0214] The rest is the same as in Example 1, and the separator and the corresponding lithium-ion battery are finally prepared.

[0215] The electrolyte absorption rate, lithium-ion conductivity, contact angle with electrolyte, longitudinal shrinkage rate, and transverse shrinkage rate of the separator, as well as the capacity retention rate of the lithium-ion battery, are shown in Table 1.

[0216] Comparative Example 2

[0217] The method according to Example 1 differs in that:

[0218] At 60°C, cellulose diacetate was dissolved in DMF, with cellulose diacetate accounting for 20 wt% of the solution mass. The mixture was mechanically stirred for 2 hours. Then, 1 / 10 of the mass of dehydrated citric acid was added. The mixture was stirred at 60°C for 30 min under nitrogen protection. Hydroxyapatite (Dv50 = 50 nm) of 10% of the total mass of cellulose diacetate and dehydrated citric acid crosslinking agent was added. The mixture was ultrasonically dispersed at 60°C (600 W power, 30 min) to obtain a homogeneous slurry.

[0219] The homogeneous slurry was cast and coated (wet film thickness 500 μm), then dried with hot air at 140 °C for 30 min to initiate cross-linking, and finally peeled and wound up to obtain a diaphragm (thickness 25 ± 2 μm).

[0220] The rest is the same as in Example 1, and the separator and the corresponding lithium-ion battery are finally prepared.

[0221] The electrolyte absorption rate, lithium-ion conductivity, contact angle with electrolyte, longitudinal shrinkage rate, and transverse shrinkage rate of the separator, as well as the capacity retention rate of the lithium-ion battery, are shown in Table 1.

[0222] Comparative Example 3

[0223] The method according to Example 1 differs in that:

[0224] At 60°C, cellulose diacetate was dissolved in DMF, with cellulose diacetate accounting for 20 wt% of the solution mass. The mixture was mechanically stirred for 2 hours, and then 10% of cellulose diacetate-modified hydroxyapatite was added. The mixture was then ultrasonically dispersed at 60°C (600W power, 30 min) to obtain a homogeneous slurry.

[0225] The rest is the same as in Example 1, and the separator and the corresponding lithium-ion battery are finally prepared.

[0226] The electrolyte absorption rate, lithium-ion conductivity, contact angle with electrolyte, longitudinal shrinkage rate, and transverse shrinkage rate of the separator, as well as the capacity retention rate of the lithium-ion battery, are shown in Table 1.

[0227] Table 1 Test results of separator and lithium-ion battery

[0228]

[0229] As can be seen from the test results in Table 1, the separator in this invention has excellent lithium-ion conductivity, and the battery containing the separator of this invention has excellent capacity retention.

[0230] As can be seen from Examples 1-3 and Examples 6-7, when the content of dehydrated citric acid crosslinking agent is too low, the thermal shrinkage rate of the diaphragm increases, the electrolyte absorption rate is artificially high, and the lithium-ion conductivity and cycle performance gradually deteriorate simultaneously. The reason for this is that the crosslinking point density between cellulose acetate molecular chains is insufficient, resulting in a loose three-dimensional network structure. Conversely, when the crosslinking agent is excessive, the lithium-ion conductivity and cycle performance decrease, and the shrinkage rate increases abnormally. The reason for this is that when the crosslinking agent is excessive, the over-densified crosslinking network severely compresses the pore space, which not only hinders electrolyte wetting but also causes a sharp drop in conductivity due to blockage of ion migration channels. At the same time, the rigid network is more prone to brittle fracture under thermal stress, leading to an abnormal increase in the shrinkage rate.

[0231] As can be seen from Examples 1, 4-5, and 8, the capacity retention rate decreases when the hydroxyapatite content is too high. The reason is that the hydroxyapatite agglomerates in the membrane, which not only blocks the micropore channels and reduces the liquid absorption rate, but also exacerbates the lithium-ion transport resistance due to local electric field distortion. In addition, the detached particles during the cycle can catalyze side reactions, resulting in a decrease in the capacity retention rate.

[0232] As can be seen from Examples 1 and 10-11, when the cross-linked cellulose acetate contains imidazole structural units, the electrolyte absorption rate of the membrane increases, and the lithium-ion conductivity and cycle performance also increase. The reason is that the imidazole structural units in this invention can enhance the "attraction" of the cross-linked cellulose acetate skeleton to the polar electrolyte solvent, and enable lithium ions to have efficient multi-path transport throughout the membrane, thereby effectively reducing the internal resistance of the battery.

[0233] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A diaphragm, characterized in that, include: The framework includes cross-linked cellulose; The supported particles were prepared by modification with a coupling agent. The loaded particles are dispersed in the framework, and the mass ratio of the framework to the loaded particles is 100:(5-20). The contact angle of the diaphragm is no greater than 35°.

2. The diaphragm according to claim 1, wherein, The diaphragm comprises at least one of the following features (1) to (7): (1) The cross-linked cellulose includes cross-linked cellulose acetate; (2) The cross-linked cellulose contains cross-linked structural units provided by a cross-linking agent and cellulose acetate structural units provided by cellulose acetate; (3) The coupling agent includes a silane coupling agent; (4) The loaded particles include hydroxyapatite modified with a coupling agent; (5) The Dv50 of the loaded particles is 20nm-100nm; (6) Based on the total mass of the loaded particles, the mass content of the coupling agent is 0.5%-5%; (7) The mass ratio of the skeleton to the load particles is 100:(5-15).

3. The diaphragm according to claim 2, wherein, The diaphragm comprises at least one of the following features (1) to (5): (1) The mass ratio of the cross-linked structural unit to the cellulose acetate structural unit is 1:(5-15); (2) The crosslinking agent comprises a polybasic acid containing at least two carboxyl groups; (3) The cellulose acetate includes at least one of cellulose monoacetate, cellulose diacetate and cellulose triacetate; (4) The cross-linked cellulose also contains imidazole structural units provided by 1-hydroxyethyl-3-methylimidazolium salt; (5) The silane coupling agent includes an amino-containing silane coupling agent.

4. The diaphragm according to claim 3, wherein, The diaphragm comprises at least one of the following features (1) to (5): (1) The mass ratio of the cross-linked structural unit to the cellulose acetate structural unit is 1:(8-12); (2) The polyacid containing two carboxyl groups includes one or more of oxalic acid, malic acid, citric acid, hydroxysuccinic acid and dihydroxysuccinic acid; (3) The 1-hydroxyethyl-3-methylimidazolium salt includes at least one of 1-hydroxyethyl-3-methylimidazolium chloride, 1-hydroxyethyl-3-methylimidazolium tetrafluoroborate, 1-hydroxyethyl-3-methylimidazolium hexafluorophosphate, 1-hydroxyethyl-3-methylimidazolium trifluoromethane sulfonate and 1-hydroxyethyl-3-methylimidazolium acetate; (4) The mass ratio of the imidazole structural unit to the crosslinking structural unit is 1:(5-8); (5) The general molecular formula of the amino-containing silane coupling agent is (RO)3Si-(CH2)3-NH2, wherein R is a C1-C4 alkyl group.

5. The diaphragm according to any one of claims 1-4, wherein, The diaphragm comprises at least one of the following features (1) to (4): (1) The thickness of the diaphragm is 15μm-50μm; (2) The electrolyte absorption rate of the diaphragm is ≥200%; (3) The lithium-ion conductivity of the diaphragm at 25℃ is ≥1.7mS / cm; (4) After the diaphragm is heat-treated at 180°C for 1 hour, the longitudinal shrinkage rate is ≤3.5% and the transverse shrinkage rate is ≤2.8%.

6. A method for preparing a diaphragm, characterized in that, Includes the following steps: S1. The suspension containing particles is contacted with the coupling agent hydrolysate, followed by solid-liquid separation, washing, and drying to obtain the loaded particles. S2. The cellulose solution is premixed with a monomer containing a cross-linking agent, and then loaded particles are added and mixed to obtain a slurry. S3. The slurry is coated and cross-linked to obtain a diaphragm.

7. The method for preparing the diaphragm according to claim 6, wherein, The method for preparing the diaphragm includes at least one of the following conditions (1) to (8): (1) The particles include hydroxyapatite; (2) The cellulose in the cellulose solution includes cellulose acetate; (3) The solvent in the particulate suspension includes alcohol solvents; (4) The mass content of the particles in the particle-containing suspension is 20%-40%; (5) In step S1, the mass ratio of the particles in the particle-containing suspension to the coupling agent in the coupling agent hydrolysate is 100:(8-15). (6) The monomer further includes 1-hydroxyethyl-3-methylimidazolium salt; (7) In step S2, the solvent in the cellulose solution includes at least one of dimethylformamide, dimethylacetamide, dimethyl sulfoxide and chloroform; (8) The cellulose content in the cellulose solution is 15%-20% by mass.

8. The method for preparing the diaphragm according to claim 6, wherein, The method for preparing the diaphragm includes at least one of the following conditions (1) to (7): (1) In step S1, the contact method includes: adding the coupling agent hydrolysate dropwise to the suspension containing particles, and continuing the reaction for 1-3 hours after the coupling agent hydrolysate dropwise is completely added. (2) In step S1, the preparation method of the coupling agent hydrolysate includes: dissolving the coupling agent in a mixed solvent of B and water, and then using a pH adjuster to adjust the pH of the system to 4-5 for hydrolysis. (3) In step S1, the endpoint of the washing is: the conductivity of the washing liquid is <5μS / cm; (4) In step S1, the drying conditions include: vacuum drying at 35-45℃ for 1.5h-2.5h, followed by vacuum drying at 55-65℃ for 0.5h-1.5h, and finally vacuum drying at 75-85℃ for 0.1h-0.5h. (5) In step S2, the premixing conditions include: being carried out under inert gas protection, at a temperature of 50-70°C, and for a time of 20-40 min; (6) In step S2, the mixing conditions include mixing for 15-50 minutes under ultrasonic conditions with a temperature of 50-70℃ and a power of 400-800W; (7) In step S3, the conditions for the crosslinking reaction include: temperature of 130-160℃ and time of 20min-50min.

9. A battery, characterized in that, The membrane includes the membrane according to any one of claims 1-5; or, the membrane is prepared by the method of preparing the membrane according to any one of claims 6-8.

10. An electronic device, characterized in that, Includes the battery as described in claim 9.

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