Diaphragm and method of making and using same

Abstract

The application discloses a diaphragm and a preparation method and application thereof. The diaphragm comprises palygorskite, polyacrylonitrile oxide and polyvinyl alcohol. The application provides a diaphragm comprising palygorskite, polyacrylonitrile oxide and polyvinyl alcohol, which further improves the thermal stability and ion conductivity of the diaphragm under the premise of ensuring that the diaphragm has good electrolyte adsorption performance, effective diffusion channels, small interface impedance, good heat insulation performance, heat resistance and flame resistance. When the diaphragm is used in a battery, the power performance and safety performance of the battery can be effectively improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of batteries, and particularly relates to a separator and a preparation method and application thereof. BACKGROUND

[0002] As a key component of lithium ion batteries, the separator has two main functions. One is the safety function. The separator prevents the short circuit between the positive and negative electrodes to ensure the safe operation of the battery. The other is the function of ensuring the normal operation of the battery by providing a channel for the transfer of lithium ions during charging and discharging. Therefore, the safety performance and electrical performance of the lithium ion battery are greatly affected by the separator. The material properties and structural properties of the separator greatly determine the safety performance and electrical performance of the battery. The separator of the lithium ion battery should have the following conditions: (1) to prevent short circuit between the positive and negative electrodes, the separator should have good electronic insulation and high lithium ion conductivity; (2) the separator should have a suitable pore size and porosity to ensure the uniformity of lithium ion transmission; (3) the separator should not have a chemical reaction with the organic electrolyte, and should also have good electrolyte wettability and retention rate; (4) the separator should have a certain mechanical strength and a thin thickness; (5) the separator should have good heat resistance and heat shrinkage resistance to ensure the safety performance of the battery.

[0003] The currently used polyolefin separators (such as polypropylene separators, polyethylene separators and composite separators PP / PE / PP) have good mechanical properties and chemical stability. However, the polyolefin separator has poor affinity with the electrolyte, is not easy to be wetted by the electrolyte, is not conducive to the migration of lithium ions, and affects the electrochemical performance of the battery. In addition, the thermal stability of the polyolefin separator is limited. During the use process, when the battery is overcharged or misused, the battery cannot be shut down in time, and the separator itself starts to shrink due to the rapid increase in the temperature of the thermal runaway process, resulting in a large area of contact between the positive and negative electrodes, causing short circuit and even explosion, thereby posing a great threat to the safety of the battery. SUMMARY

[0004] The present application aims to at least solve one of the technical problems in the related art. To this end, the purpose of the present application is to provide a separator and a preparation method and application thereof. The present application provides a separator containing attapulgite, polyacrylonitrile oxide and polyvinyl alcohol, which further improves the thermal stability and ion conductivity of the separator while ensuring that the separator has good electrolyte absorption performance, effective diffusion path, small interface impedance, good thermal insulation performance, heat resistance and flame retardance. When the separator of the present application is used in a battery, the power performance and safety performance of the battery can be effectively improved.

[0005] In one aspect of the present application, a separator is provided. According to embodiments of the present application, the separator comprises:

[0006] attapulgite, polyacrylonitrile oxide and polyvinyl alcohol.

[0007] According to the separator of embodiments of the present application, the present application provides a separator comprising attapulgite, polyacrylonitrile oxide and polyvinyl alcohol, which further improves the thermal stability and ionic conductivity of the separator while ensuring that the separator has good electrolyte adsorption performance, effective diffusion pathways, small interface impedance, good thermal insulation performance, heat resistance and flame retardance. When the separator of the present application is used in a battery, the power performance and safety performance of the battery can be effectively improved.

[0008] In addition, the separator according to the above-mentioned embodiments of the present application can also have the following additional technical features:

[0009] In some embodiments of the present application, the separator comprises 100 parts by weight of attapulgite, 10-60 parts by weight of polyacrylonitrile oxide and 0.1-4 parts by weight of polyvinyl alcohol.

[0010] In some embodiments of the present application, the separator comprises 100 parts by weight of attapulgite, 20-40 parts by weight of polyacrylonitrile oxide and 0.5-2 parts by weight of polyvinyl alcohol.

[0011] In some embodiments of the present application, the lithium ion conductivity of the separator is 3.0-4.7 mS / cm.

[0012] In some embodiments of the present application, the longitudinal thermal shrinkage of the separator is not more than 2.7%; and / or, the transverse thermal shrinkage of the separator is not more than 0.6%.

[0013] In a second aspect of the present application, a method for preparing the above-mentioned separator is provided. According to embodiments of the present application, the method comprises:

[0014] preparing a polyacrylonitrile / polyvinyl alcohol / attapulgite suspension;

[0015] performing solid-liquid separation on the polyacrylonitrile / polyvinyl alcohol / attapulgite suspension to obtain a solid part;

[0016] drying the solid part to obtain a precursor composite material;

[0017] oxidizing the precursor composite material to obtain a separator material;

[0018] preparing the separator material into a separator.

[0019] According to the method for preparing the above-mentioned separator according to the embodiments of the present application, the polyacrylonitrile oxide / polyvinyl alcohol / attapulgite composite separator is obtained through oxidation treatment, which further improves the thermal stability and ion conductivity of the separator under the premise of ensuring that the separator has good electrolyte adsorption performance, effective diffusion path, small interface impedance, good heat insulation performance, heat resistance and flame retardance.

[0020] In addition, the method for preparing the above-mentioned separator according to the above-mentioned embodiments of the present application can further have the following additional technical features:

[0021] In some embodiments of the present application, the preparation of the polyacrylonitrile / polyvinyl alcohol / attapulgite suspension comprises:

[0022] preparing an attapulgite suspension;

[0023] adding a polyvinyl alcohol solution to the attapulgite suspension to obtain a polyvinyl alcohol / attapulgite suspension;

[0024] adding a polyacrylonitrile solution to the polyvinyl alcohol / attapulgite suspension to obtain a polyacrylonitrile / polyvinyl alcohol / attapulgite suspension.

[0025] In some embodiments of the present application, the mass fraction of attapulgite in the attapulgite suspension is 5% to 20%; and / or, the concentration of polyvinyl alcohol in the polyvinyl alcohol solution is 5 g / L to 15 g / L; and / or, the concentration of polyacrylonitrile in the polyacrylonitrile solution is 5 g / L to 15 g / L.

[0026] In some embodiments of the present application, in the polyacrylonitrile / polyvinyl alcohol / attapulgite suspension, the mass ratio of the attapulgite, the polyacrylonitrile and the polyvinyl alcohol is 100:(10-60):(0.1-4); or, in the polyacrylonitrile / polyvinyl alcohol / attapulgite suspension, the mass ratio of the attapulgite, the polyacrylonitrile and the polyvinyl alcohol is 100:(20-40):(0.5-2).

[0027] In some embodiments of the present application, the drying of the solid part comprises: freezing the solid part in an ultra-low temperature environment, and then performing freeze drying; the temperature of the ultra-low temperature environment is-70℃ to-90℃, and the freezing time in the ultra-low temperature environment is 6h to 24h; the temperature of the freeze drying is-30℃ to-50℃, and the vacuum degree of the freeze drying is 5Pa to 20Pa.

[0028] In some embodiments of the present application, the temperature of the oxidation is 280-350℃, the time of the oxidation at the temperature is 20-40min; the heating rate of the precursor composite to the temperature of the oxidation is not more than 5℃ / min.

[0029] In a third aspect of the present application, a battery is provided. According to embodiments of the present application, the battery comprises the separator of the above embodiments or comprises the separator prepared by the method of the above embodiments. Thus, the power performance and the safety performance of the battery can be effectively improved.

[0030] In a fourth aspect of the present application, an electrical equipment is provided. According to embodiments of the present application, the electrical equipment has the battery of the above embodiments. Thus, the electrical equipment has all the advantages of the battery, which are not repeated here.

[0031] Additional aspects and advantages of the present application will be in part apparent and in part pointed out hereinafter. BRIEF DESCRIPTION OF DRAWINGS

[0032] The above and / or additional aspects and advantages of the present application will become apparent and be readily appreciated from the following description, including the appended drawings, wherein:

[0033] Figure 1 Flow chart of the method for preparing the separator of some embodiments of the present application.

[0034] Figure 2 Structural schematic diagram of the polyacrylonitrile / polyvinyl alcohol / attapulgite composite before oxidation.

[0035] Figure 3 Schematic diagram of the oxidation process of Example 1.

[0036] Figure 4 SEM diagram of the separator prepared in Example 1. DETAILED DESCRIPTION

[0037] Embodiments of the present application are described in detail below with reference to the accompanying drawings, in which like reference numerals indicate like elements or elements having the same or similar function throughout the several views. The embodiments described below are examples of the present application, which are intended to explain the present application, and should not be understood as limiting the present application.

[0038] The chemical molecular formula of the attapulgite is (Al2Mg2)Si8O 20(OH)2(OH2)4·4H2O. The microstructure of the attapulgite is composed of continuously reversed arranged silicon-oxygen tetrahedron and discontinuous octahedron, forming a "sandwich" structure unit with two continuous tetrahedrons sandwiching one octahedron. The vertex oxygen of the tetrahedron pointing to the (010) crystal plane is connected with the metal cation (Mg 2+ or Al 3 + ) to form octahedral coordination; while the vertex oxygen of the tetrahedron pointing to the (100) crystal plane is connected with two OH or OH2 groups to complete the remaining octahedral coordination. The one-dimensional nanorods of the attapulgite are randomly stacked and form a porous structure. The diameter of the single crystal structure is 10-50 nm, and the length is 1-2 μm. The morphology of the attapulgite is composed of three parts: one is the basic unit structure, i.e. the one-dimensional rod-like single crystal (referred to as rod crystal); two is the rod crystal beam (referred to as crystal beam) formed by the parallel and close aggregation of the rod-like single crystals; and three is the disordered aggregate formed by the mutual stacking of the rod crystal beams (containing rod crystals). Generally, the attapulgite exists in the form of crystal beam or aggregate. In addition, the natural attapulgite has a high specific surface area (about 130.00 m 2 g -1 ) and a high adsorption capacity (about 132.72 mg g -1 ), and the pore volume is mostly in the range of 0.31-0.58 cm 3 g -1 . However, the crystal beam and aggregate structure of the attapulgite is dense, which makes the nanorod-like structure of the attapulgite easy to agglomerate, resulting in limited ion conductivity and thermal stability of the separator formed by the attapulgite.

[0039] Therefore, in one aspect of the present application, the present application provides a separator comprising attapulgite, polyacrylonitrile oxide and polyvinyl alcohol, which further improves the thermal stability and ion conductivity of the separator while ensuring that the separator has good adsorption of electrolyte, effective diffusion path, small interface impedance, good heat insulation performance, heat resistance and flame retardance. When the separator of the present application is used in a battery, the power performance and safety performance of the battery can be effectively improved.

[0040] The principle of the separator of the present application achieving the above beneficial effects will be described in detail as follows:

[0041] The application provides a new diaphragm, comprising palygorskite, polyacrylonitrile oxide and polyvinyl alcohol. The nanorod structure of the palygorskite has a continuous one-dimensional lithium ion transmission channel and a small interface impedance, and provides an effective diffusion path for lithium ions, so that the lithium ions can be quickly embedded and extracted from the diaphragm, the Li ion channel is not easy to be blocked, and thus the power performance of the battery can be improved. At the same time, the porous structure of the palygorskite can effectively adsorb electrolyte, thereby improving the cycle stability. In addition, the palygorskite can form a stable heat insulation layer at high temperature, which can effectively slow down the speed of flame spread. At the same time, the palygorskite also has good heat resistance, and can maintain its flame retardant performance for a long time, thereby effectively limiting the occurrence and spread of fire. The polyacrylonitrile oxide is obtained by oxidizing polyacrylonitrile. In the oxidation process, the polyacrylonitrile mainly undergoes cyclization, oxidation, dehydrogenation and crosslinking reactions, and the process of changing the carbon-nitrogen triple bond into a carbon-nitrogen double bond. In the process of cyclization and crosslinking, the long straight chain of the polyacrylonitrile becomes a stable and heat-resistant ladder-shaped structure group (i.e. a cyclic structure group). Compared with the long straight chain, the cyclic structure group is more stable and heat-resistant, and thus the thermal stability of the diaphragm is effectively improved. At the same time, the nanorods of the palygorskite and the polyacrylonitrile oxide are adhered, so that the network structure of the palygorskite is more complete, and thus the lithium ion channel is more complete, and the ionic conductivity of the diaphragm is effectively improved.

[0042] In the embodiment of the application, the structural formula of the polyacrylonitrile oxide is:

[0043]

[0044] As can be seen from the structural formula of the polyacrylonitrile oxide, the polyacrylonitrile oxide has a part of aromatic cyclic structure groups. Since the aromatic cyclic structure group is more stable and heat-resistant, the diaphragm has high flame retardancy, excellent thermal stability, no fiber melting, softening and shrinking, and no molten droplets in combustion; and has the advantages of good heat insulation effect, acid and alkali corrosion resistance, chemical environment resistance, and good radiation resistance.

[0045] In some embodiments of the present application, the diaphragm comprises 100 parts by weight of attapulgite, 10-60 parts by weight of polyacrylonitrile oxide and 0.1-4 parts by weight of polyvinyl alcohol. By limiting the content of each component within the above range, good bonding force between the polyacrylonitrile oxide and the attapulgite can be ensured, and the thermal stability and ionic conductivity of the diaphragm can be effectively improved. The inventors have found that if the content of polyacrylonitrile oxide is too low, the thermal stability of the diaphragm cannot be effectively improved, but if the content of polyacrylonitrile oxide is too high, the ionic conductivity of the diaphragm will be affected. At the same time, the inventors have found that if the content of polyvinyl alcohol is too low, the good bonding force between the polyacrylonitrile oxide and the attapulgite cannot be effectively improved, which further leads to the inability to effectively improve the thermal stability and ionic conductivity of the diaphragm; if the content of polyvinyl alcohol is too high, the content of attapulgite and polyacrylonitrile oxide will be reduced, thereby failing to ensure the thermal stability and ionic conductivity of the diaphragm. Preferably, the diaphragm comprises 100 parts by weight of attapulgite, 20-40 parts by weight of polyacrylonitrile oxide and 0.5-2 parts by weight of polyvinyl alcohol.

[0046] In the embodiments of the present application, a diaphragm comprising attapulgite, polyacrylonitrile oxide and polyvinyl alcohol is provided, which further improves the thermal stability and ionic conductivity of the diaphragm while ensuring that the diaphragm has good electrolyte adsorption performance, small interface impedance, good thermal insulation performance, heat resistance and flame retardance.

[0047] In the embodiments of the present application, the lithium ion conductivity of the diaphragm is 3.0 mS / cm-4.7 mS / cm, thereby effectively improving the power performance of the battery. Specifically, the lithium ion conductivity of the diaphragm refers to the lithium ion conductivity of the diaphragm after being soaked in electrolyte. In the embodiments of the present application, the solvent of the electrolyte is EC+EMC+DMC with a mass ratio of 1:1:1, then lithium salt LiPF6 and additive VC are added, wherein the mass ratio of LiPF6 in the electrolyte is 9%, and the mass ratio of VC in the electrolyte is 3%.

[0048] In the embodiments of the present application, the thermal shrinkage rate of the diaphragm in the longitudinal direction is not more than 2.7%, and / or the thermal shrinkage rate of the diaphragm in the transverse direction is not more than 0.6%, thereby effectively avoiding the thermal shrinkage phenomenon of the diaphragm due to thermal runaway and improving the safety performance of the battery. Specifically, the thermal shrinkage rate of the diaphragm in the longitudinal direction refers to the thermal shrinkage rate of the diaphragm in the longitudinal direction MD after being baked at 110°C for 12h, and the thermal shrinkage rate of the diaphragm in the transverse direction refers to the thermal shrinkage rate of the diaphragm in the transverse direction TD after being baked at 110°C for 12h.

[0049] In the embodiments of the present application, the longitudinal direction MD of the diaphragm is the coating direction of the diaphragm, the transverse direction TD of the diaphragm is the width direction of the diaphragm, and the longitudinal direction MD of the diaphragm is perpendicular to the transverse direction TD of the diaphragm.

[0050] In embodiments of the application, the thermal shrinkage refers to the rate of size change of the separator during the heating process, and the thermal shrinkage = (size before heating - size after heating) / size before heating.

[0051] In a second aspect of the application, a method for preparing the above-mentioned separator is provided. According to embodiments of the application, referring to the accompanying drawings, Figure 1 The method comprises:

[0052] S100: preparing a polyacrylonitrile / polyvinyl alcohol / attapulgite suspension;

[0053] In this step, a polyacrylonitrile / polyvinyl alcohol / attapulgite suspension is prepared so as to uniformly mix polyacrylonitrile, polyvinyl alcohol and attapulgite.

[0054] In some embodiments of the application, step S100 further comprises the following steps:

[0055] S110: preparing an attapulgite suspension;

[0056] In this step, the purified attapulgite is mixed with a solvent (e.g. deionized water) to prepare an attapulgite suspension.

[0057] In embodiments of the application, the mass fraction of attapulgite in the attapulgite suspension is not particularly limited as long as the attapulgite can be uniformly dispersed in the solvent. As some specific examples, the mass fraction of attapulgite in the attapulgite suspension can be 5% to 20%.

[0058] As some specific embodiments, the purification process of the above-mentioned attapulgite is as follows:

[0059] The raw attapulgite is sieved using a sieve, the sieved attapulgite is mixed with a diluted hydrochloric acid solution (which can have a concentration of 1% to 10%) and mechanically stirred to obtain an attapulgite suspension. Then, the attapulgite suspension is allowed to stand until a suspended matter appears on the surface of the attapulgite suspension, and the suspended matter is removed. The remaining attapulgite suspension is suction filtered using a Buchner funnel to obtain a solid part, and the solid part is repeatedly washed with deionized water until the pH value of the filtrate reaches neutral. The washed solid part is dispersed in deionized water and mechanically stirred until the suspension is uniformly dispersed. Then, the uniformly dispersed suspension is subjected to ultrasonic treatment, and brown precipitates will be attached to the wall of the container containing the suspension after ultrasonic treatment, and the brown precipitates are removed. The suspension is subjected to ultrasonic treatment for 2 to 3 times to obtain a purified attapulgite suspension, and the solvent in the attapulgite suspension is removed to obtain pure attapulgite.

[0060] S120: adding a polyvinyl alcohol solution to the attapulgite suspension;

[0061] In this step, the polyvinyl alcohol solution is added to the above-mentioned attapulgite suspension to obtain an initial polyvinyl alcohol / attapulgite suspension, so as to uniformly mix the polyvinyl alcohol and the attapulgite. Preferably, the polyvinyl alcohol solution can be added dropwise to the attapulgite suspension. As some specific examples, the concentration of the polyvinyl alcohol in the polyvinyl alcohol solution can be 5 g / L to 15 g / L.

[0062] As still further specific examples, the above-mentioned step can further include: suction filtering the above-mentioned initial polyvinyl alcohol / attapulgite suspension, and eluting with an organic solvent (for example, N,N-dimethylacetamide, abbreviated as DMAc), then dispersing the polyvinyl alcohol / attapulgite solid part in an organic solvent (for example, N,N-dimethylacetamide) and stirring, finally obtaining a polyvinyl alcohol / attapulgite suspension.

[0063] In this process, if the polyvinyl alcohol is not added, due to the weak interaction force between the Si-OH groups in the attapulgite and the CN groups of the polyacrylonitrile, the polyacrylonitrile is prone to be filtered out from the polyvinyl alcohol / attapulgite suspension in the subsequent filtration process, thereby resulting in a low content of polyacrylonitrile oxide in the separator, and thus causing the separator to have poor mechanical strength and the separator to be prone to cracking, pulverization and the like during the charging and discharging process. Therefore, the water-soluble polymer polyvinyl alcohol is introduced into the separator material in the present application. Firstly, the hydroxyl groups of the polyvinyl alcohol can form hydrogen bonds with the Si-OH groups of the attapulgite, as shown in FIG. 1; secondly, the long carbon chain of the polyvinyl alcohol is similar to the carbon chain structure of the polyacrylonitrile, and can intertwine with each other, as shown in FIG. 2, thereby making the polyacrylonitrile oxide have good binding force with the attapulgite. Figure 2 Figure 2

[0064] Further, the interaction force among the polyacrylonitrile / polyvinyl alcohol / attapulgite becomes stronger after suction filtration under a certain pressure, and the structure is more compact and dense.

[0065] S130: adding a polyacrylonitrile solution to the polyvinyl alcohol / attapulgite suspension

[0066] In this step, the polyacrylonitrile solution is added to the polyvinyl alcohol / attapulgite suspension to obtain a polyacrylonitrile / polyvinyl alcohol / attapulgite suspension, so as to uniformly mix the polyacrylonitrile, the polyvinyl alcohol and the attapulgite. Preferably, the polyacrylonitrile solution can be added dropwise to the polyvinyl alcohol / attapulgite suspension. As some specific examples, the concentration of the polyacrylonitrile in the polyacrylonitrile solution can be 5 g / L to 15 g / L.

[0067] ​​According to some specific embodiments of the present application, in the polyacrylonitrile / polyvinyl alcohol / attapulgite suspension prepared in step S100, the mass ratio of attapulgite, polyacrylonitrile and polyvinyl alcohol is 100:(10-60):(0.1-4); by limiting the content of each component within the above range, both good binding force between polyacrylonitrile oxide and attapulgite and effective improvement of the thermal stability and ionic conductivity of the separator can be ensured. Preferably, in the polyacrylonitrile / polyvinyl alcohol / attapulgite suspension, the mass ratio of attapulgite, polyacrylonitrile and polyvinyl alcohol is 100:(20-40):(0.5-2).

[0068] S200: solid-liquid separation of the polyacrylonitrile / polyvinyl alcohol / attapulgite suspension;

[0069] In this step, the polyacrylonitrile / polyvinyl alcohol / attapulgite suspension is subjected to solid-liquid separation to obtain a solid part.

[0070] In the present application, the specific method for solid-liquid separation of the polyacrylonitrile / polyvinyl alcohol / attapulgite suspension is not particularly limited, and as some specific examples, the polyacrylonitrile / polyvinyl alcohol / attapulgite suspension can be subjected to suction filtration to obtain a filter cake.

[0071] S300: drying of the solid part;

[0072] In this step, the solid part is dried to remove the liquid solvent entrapped in the solid part, to obtain a precursor composite material.

[0073] In the present application, the specific method for drying of the solid part is not particularly limited, and as some specific examples, the solid part can be first frozen in an ultra-low temperature environment to form the liquid solvent entrapped in the solid part into a solid state, and then freeze-dried to remove the liquid solvent entrapped in the solid part, to obtain a precursor composite material.

[0074] According to some specific embodiments of the present application, the temperature of the ultra-low temperature environment can be -70℃ to -90℃, and the freezing time in the ultra-low temperature environment can be 6h to 24h, thereby ensuring that the liquid solvent entrapped in the solid part is formed into a solid state.

[0075] According to still some specific embodiments of the present application, the temperature of freeze-drying is -30℃ to -50℃, and the vacuum degree of freeze-drying is 5Pa to 20Pa, thereby ensuring effective removal of the liquid solvent entrapped in the solid part.

[0076] S400: oxidation of the precursor composite material;

[0077] In this step, the precursor composite material is heated, and the precursor composite material is oxidized in the heating process, so that the polyacrylonitrile in the precursor composite material becomes polyacrylonitrile oxide, and finally the separator material is obtained. In the oxidation process, the polyacrylonitrile mainly undergoes cyclization, oxidation, dehydrogenation and crosslinking reactions, and is accompanied by the process of changing the carbon-nitrogen triple bond to carbon-nitrogen double bond. In the process of cyclization and crosslinking, the long straight chain of polyacrylonitrile becomes a stable and heat-resistant ladder structure group (i.e. a ring structure group). Compared with the long straight chain, the ring structure group is more stable and more heat-resistant, so the thermal stability of the separator is effectively improved. At the same time, in the oxidation process of polyacrylonitrile, the nanorod structure of the attapulgite is connected, so that the network structure of the attapulgite is more complete, thereby making the lithium ion path more complete, and thus the ionic conductivity of the separator is effectively improved.

[0078] The oxidation process of polyacrylonitrile is as follows:

[0079]

[0080] The present application uses polyacrylonitrile as a raw material to form a part of aromatic cyclization structure of polyacrylonitrile oxide by air oxidation. Since the aromatic ring structure group is more stable and more heat-resistant, the separator has high flame retardance, excellent thermal stability, and the fibers do not melt, soften and shrink, and no molten droplets are generated in the combustion. In addition, the separator has the advantages of good heat insulation effect, acid and alkali corrosion resistance, chemical environment resistance, and good radiation resistance.

[0081] In the present application, in the oxidation process of polyacrylonitrile, small molecules such as HCN, NH3, H2, etc. are separated from the polyacrylonitrile molecules, and the mass change before and after oxidation is very small, which can be ignored.

[0082] According to some specific embodiments of the present application, the temperature of the above oxidation is 280-350°C, and the oxidation time at the oxidation temperature is 20-40 min, so that the cyclization, oxidation, dehydrogenation and crosslinking reactions of polyacrylonitrile can be further ensured, and the process of changing the carbon-nitrogen triple bond to carbon-nitrogen double bond is accompanied. In the process of cyclization and crosslinking, the long straight chain of polyacrylonitrile becomes a stable and heat-resistant ladder structure, so that the polyacrylonitrile oxide has a ring structure group, thereby effectively improving the thermal stability of the separator. At the same time, the network connection of the nanorod structure of the attapulgite is further ensured in the oxidation process of polyacrylonitrile, thereby effectively improving the ionic conductivity of the separator.

[0083] In the embodiments of the present application, the specific process of heating the precursor composite material to the oxidation temperature is not particularly limited. According to still another specific embodiment of the present application, the heating rate of heating the precursor composite material to the oxidation temperature is not more than 5°C / min, so that the long straight chain in the polyacrylonitrile can be fully cyclized, thereby further improving the thermal stability of the separator.Figure 3 is a specific example of oxidizing the precursor composite material, and the color of the precursor composite material gradually darkens from yellowish brown to dark brown during the heating process.

[0084] S500: preparing the diaphragm material into a diaphragm;

[0085] In this step, the diaphragm material can be prepared into a diaphragm according to the actual needs of the diaphragm, such as thickness, shape, etc.

[0086] The method for preparing the diaphragm according to the embodiments of the present application has at least the following advantages:

[0087] First, the method introduces polyacrylonitrile into the diaphragm raw material, and polyacrylonitrile mainly undergoes cyclization, oxidation, dehydrogenation, and crosslinking reactions during the oxidation process, and is accompanied by the process of changing the carbon-nitrogen triple bond into a carbon-nitrogen double bond. During the cyclization and crosslinking processes, the long straight chain of polyacrylonitrile becomes a stable and heat-resistant ladder-shaped structure group (i.e. a cyclic structure group). Compared with a long straight chain, the cyclic structure group is more stable and more heat-resistant, thus effectively improving the thermal stability of the diaphragm. At the same time, during the oxidation process of polyacrylonitrile, the nanorods of the attapulgite are adhered, making the network structure of the attapulgite more complete, thus making the lithium ion path more complete, and effectively improving the ionic conductivity of the diaphragm.

[0088] Second, the attapulgite hardly changes during the oxidation process, and the nanorod structure of the attapulgite has a continuous one-dimensional lithium ion transmission channel and a small interface impedance, providing an effective diffusion path for lithium ions, so that lithium ions can be quickly embedded and extracted from the diaphragm, the Li ion channel is not easy to be blocked, thereby being able to improve the power performance of the battery. At the same time, the porous structure of the attapulgite can effectively adsorb the electrolyte, thereby improving the cycle stability. In addition, the attapulgite can form a stable heat insulation layer at high temperature, which can effectively slow down the speed of flame spread. At the same time, the attapulgite also has good heat resistance, which can maintain its flame retardant performance for a long time, thereby being able to effectively limit the occurrence and spread of fire.

[0089] Third, the polyacrylonitrile oxide / polyvinyl alcohol / attapulgite composite diaphragm obtained by freeze-drying and low-temperature oxidation treatment further improves the thermal stability and ionic conductivity of the diaphragm on the premise of ensuring that the diaphragm has good adsorption of electrolyte performance, effective diffusion path, small interface impedance, good heat insulation performance, heat resistance and flame retardant performance. The method of freeze-drying and low-temperature oxidation treatment is efficient and green.

[0090] In a third aspect, the present application provides a battery. According to embodiments of the present application, the battery includes the separator of the above embodiments or is prepared by the method of the above embodiments. Thus, the power performance and safety performance of the battery can be effectively improved.

[0091] In embodiments of the present application, the battery can be a lithium ion battery, which includes the separator of the above embodiments or is prepared by the method of the above embodiments. Thus, the power performance and safety performance of the lithium ion battery can be effectively improved.

[0092] In embodiments of the present application, the battery can also be a sodium ion battery, which includes the separator of the above embodiments or is prepared by the method of the above embodiments. Thus, the power performance and safety performance of the sodium ion battery can be effectively improved.

[0093] The following is a specific description of a lithium ion battery as an example, which includes a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte. The separator is arranged between the positive electrode sheet and the negative electrode sheet. During the charging and discharging process of the battery, active ions lithium ions are embedded and extracted between the positive electrode sheet and the negative electrode sheet. The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet, mainly to prevent the short circuit of the positive and negative electrodes, and at the same time to allow the lithium ions to pass through.

[0094] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer arranged on at least one side surface of the positive electrode current collector, and the positive electrode active material layer includes a positive electrode active material. In some embodiments of the present application, the positive electrode active material can use the positive electrode active material commonly known in the art for lithium ion batteries. As an example, the positive electrode active material can include at least one of lithium iron phosphate, lithium nickelate, lithium manganate, lithium cobaltate, lithium manganese phosphate, lithium vanadium phosphate, lithium nickel-cobalt-aluminum oxide, and lithium nickel-cobalt-manganese oxide.

[0095] In some embodiments of the present application, the positive electrode current collector can include a metal foil or a composite positive electrode current collector. For example, the metal foil can use an aluminum foil. The composite positive electrode current collector can include a high polymer material base layer and a metal layer formed on at least one side surface of the high polymer material base layer, for example, the composite negative electrode current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, etc.) on a high polymer material base material (such as a polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc. base material).

[0096] In some embodiments of the present application, the positive electrode active material layer can also optionally include a positive electrode conductive agent. As an example, the positive electrode conductive agent can include at least one of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0097] In some embodiments of the present application, the positive active material layer can further optionally include a positive electrode binder. As an example, the positive electrode binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0098] In some embodiments of the present application, the positive electrode sheet can be prepared by dispersing the above-described components (e.g., positive active material, conductive agent, binder) for preparing the positive electrode sheet in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry, coating the positive electrode slurry on a positive electrode current collector, and then drying, cold-pressing, and the like to obtain the positive electrode sheet.

[0099] The negative electrode sheet includes a negative electrode current collector and a negative active material layer disposed on at least one side surface of the negative electrode current collector, and the negative active material layer includes a negative active material.

[0100] In some embodiments of the present application, the negative electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, a copper foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, etc.) on a polymer material base layer (e.g., a base layer of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc.).

[0101] In some embodiments of the present application, the negative active material can be a negative active material for a battery known in the art. As an example, the negative active material can include at least one of graphite, soft carbon, hard carbon, a silicon-based material, a tin-based material, etc. The silicon-based material can include at least one of elemental silicon, a silicon oxide compound, a silicon-carbon composite, a silicon-nitrogen composite, and a silicon alloy. The tin-based material can include at least one of elemental tin, a tin oxide compound, and a tin alloy.

[0102] In some embodiments of the present application, the negative active material layer can further optionally include a negative electrode binder. The negative electrode binder can include at least one of styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0103] In some embodiments of the present application, the negative active material layer can further optionally comprise a negative conductive agent. The negative conductive agent can comprise at least one of super P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0104] In some embodiments of the present application, the negative active material layer can further optionally comprise other auxiliary agents, such as thickening agents (e.g., sodium carboxymethyl cellulose (CMC-Na)) and the like.

[0105] In some embodiments of the present application, the negative electrode sheet can be prepared by dispersing the above-mentioned components (e.g., negative active material, conductive agent, binder, and any other components) for preparing the negative electrode sheet in a solvent (e.g., deionized water) to form a negative electrode slurry, coating the negative electrode slurry on a negative current collector, and then performing drying, cold pressing, and the like to obtain the negative electrode sheet.

[0106] In the present application, the electrolyte is an organic solvent in which a charge carrier is dissolved. The electrolyte is not limited in the present application and can be self-adjusted according to the actual situation.

[0107] The battery of the present application can include a battery monomer form, a battery module form, and a battery pack form. In some embodiments, the battery monomer can be assembled into a battery module, and the number of battery monomers contained in the battery module can be one or more, and the specific number can be selected by a person skilled in the art according to the application and capacity of the battery module. In some embodiments, the battery module can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by a person skilled in the art according to the application and capacity of the battery pack.

[0108] In a fourth aspect of the present application, a power consuming device is provided. According to embodiments of the present application, the power consuming device comprises the battery as described in the above embodiments. Thus, the power consuming device has all the advantages of the battery, which are not repeated here.

[0109] Specifically, the above-mentioned power consuming device can be, but is not limited to, a mobile phone, a tablet, a notebook computer, an electric toy, an electric tool, an electric car, an electric vehicle, a ship, a spacecraft, and the like. Among them, the electric toy can include a fixed or mobile electric toy, such as a game console, an electric car toy, an electric ship toy, and an electric plane toy, and the like, and the spacecraft can include an airplane, a rocket, a space shuttle, a spacecraft, and the like.

[0110] The following examples of the present application are described in detail. It should be noted that the following examples are illustrative and are intended only to explain the present application and are not to be construed as limiting the present application. In addition, unless otherwise expressly stated, all reagents used in the following examples are commercially available or can be synthesized according to methods described herein or known methods. Reaction conditions not listed are also readily available to those skilled in the art.

[0111] Example 1

[0112] (1) Purification of attapulgite:

[0113] The raw attapulgite soil is sieved through a sieve. The sieved attapulgite is mixed with a 3% hydrochloric acid solution and mechanically stirred to obtain an attapulgite suspension. The attapulgite suspension is then allowed to stand until suspended matter appears on the surface of the attapulgite suspension, which is then removed. The remaining attapulgite suspension is filtered using a Büchner funnel under pressure from a circulating water pump to obtain a solid fraction. The solid fraction is repeatedly rinsed with deionized water until the pH of the filtrate reaches neutral. The rinsed solid fraction is dispersed in deionized water and mechanically stirred until the suspension is uniformly dispersed. The uniformly dispersed suspension is then ultrasonically treated. A brown precipitate will form on the walls of the beaker after ultrasonication, which is removed. The suspension is ultrasonically treated 2-3 times to obtain a purified attapulgite suspension. The solvent in the attapulgite suspension is removed to obtain pure attapulgite.

[0114] (2) Preparation of polyacrylonitrile / polyvinyl alcohol / attapulgite suspension:

[0115] Take 10g of purified attapulgite and mix it in 100mL of deionized water to prepare an attapulgite suspension. -1 The polyvinyl alcohol aqueous solution is gradually added dropwise to the attapulgite suspension and stirred for 6 hours to obtain a polyvinyl alcohol / attapulgite suspension. The prepared polyvinyl alcohol / attapulgite suspension is filtered and rinsed with DMAc, and then the polyvinyl alcohol / attapulgite solid portion is dispersed in 50gDMAc and stirred for 12 hours to obtain a polyvinyl alcohol / attapulgite suspension. 1g of polyacrylonitrile powder (the addition amount is 10wt% of the attapulgite mass) is dissolved in the DMAc solution to obtain a polyacrylonitrile solution with a concentration of 10g / L. The prepared polyacrylonitrile solution is added dropwise to the polyvinyl alcohol / attapulgite suspension and stirred to prepare a polyacrylonitrile / polyvinyl alcohol / attapulgite suspension.

[0116] (3) Preparation of polyacrylonitrile oxide / polyvinyl alcohol / attapulgite composite membrane:

[0117] The polyacrylonitrile / polyvinyl alcohol / attapulgite suspension prepared above was suction filtered and rinsed with deionized water. Then, the solid part was frozen in a ultra-low temperature refrigerator at a temperature of -80℃ for 12h and vacuum dried in a freeze dryer at a temperature of -40℃ to obtain a precursor composite material. The precursor composite material was heated to an oxidation temperature of 300℃ and kept in a tube furnace for 30min to obtain a separator material, and the oxidation process is as shown in Figure 3 The SEM of the polyacrylonitrile oxide / polyvinyl alcohol / attapulgite composite separator is shown in Figure 4 It can be seen from Figure 4 that the one-dimensional nanorods of attapulgite in the composite separator are randomly stacked and stacked to form a porous structure. Finally, the separator material is prepared into a separator, and the attapulgite: polyacrylonitrile oxide: polyvinyl alcohol in the prepared separator is 100:10:1.

[0118] (4) The separator prepared in step (3) is used to prepare a button type all-solid-state battery. The positive electrode uses a lithium iron phosphate positive electrode, and the negative electrode uses a graphite negative electrode. The solvent of the electrolyte is EC+EMC+DMC with a mass ratio of 1:1:1, and then lithium salt LiPF6 and additive VC are added, wherein the mass ratio of LiPF6 in the electrolyte is 9%, and the mass ratio of VC in the electrolyte is 3%.

[0119] Example 2

[0120] The preparation method of Example 2 is basically the same as that of Example 1, except that:

[0121] The addition amount of polyacrylonitrile powder is 20wt% of the mass of attapulgite, and the attapulgite: polyacrylonitrile oxide: polyvinyl alcohol in the prepared separator is 100:20:1.

[0122] Example 3

[0123] The preparation method of Example 3 is basically the same as that of Example 1, except that:

[0124] The addition amount of polyacrylonitrile powder is 30wt% of the mass of attapulgite, and the attapulgite: polyacrylonitrile oxide: polyvinyl alcohol in the prepared separator is 100:30:1.

[0125] Example 4

[0126] The preparation method of Example 4 is basically the same as that of Example 1, except that:

[0127] The addition amount of polyacrylonitrile powder is 40wt% of the mass of attapulgite, and the attapulgite: polyacrylonitrile oxide: polyvinyl alcohol in the prepared separator is 100:40:1.

[0128] Example 5

[0129] The preparation method of Example 5 is substantially the same as that of Example 1, except that:

[0130] The polyacrylonitrile powder is added in an amount of 50 wt% of the mass of the attapulgite, and the prepared separator has attapulgite: polyacrylonitrile oxide: polyvinyl alcohol = 100:50:1.

[0131] Example 6

[0132] The preparation method of Example 6 is substantially the same as that of Example 1, except that:

[0133] The polyacrylonitrile powder is added in an amount of 60 wt% of the mass of the attapulgite, and the prepared separator has attapulgite: polyacrylonitrile oxide: polyvinyl alcohol = 100:60:1.

[0134] Example 7

[0135] The preparation method of Example 7 is substantially the same as that of Example 1, except that:

[0136] The polyacrylonitrile powder is added in an amount of 5 wt% of the mass of the attapulgite, and the prepared separator has attapulgite: polyacrylonitrile oxide: polyvinyl alcohol = 100:5:1.

[0137] Example 8

[0138] The preparation method of Example 8 is substantially the same as that of Example 1, except that:

[0139] The polyacrylonitrile powder is added in an amount of 65 wt% of the mass of the attapulgite, and the prepared separator has attapulgite: polyacrylonitrile oxide: polyvinyl alcohol = 100:65:1.

[0140] Example 9

[0141] The preparation method of Example 9 is substantially the same as that of Example 3, except that:

[0142] The polyvinyl alcohol is added in an amount of 0.1 wt% of the mass of the attapulgite, and the prepared separator has attapulgite: polyacrylonitrile oxide: polyvinyl alcohol = 100:30:0.1.

[0143] Example 10

[0144] The preparation method of Example 10 is substantially the same as that of Example 3, except that:

[0145] The polyvinyl alcohol is added in an amount of 0.5 wt% of the mass of the attapulgite, and the prepared separator has attapulgite: polyacrylonitrile oxide: polyvinyl alcohol = 100:30:0.5.

[0146] Example 11

[0147] The preparation method of Example 11 is substantially the same as that of Example 3, except that:

[0148] The polyvinyl alcohol is added in an amount of 2 wt% of the mass of the attapulgite, and the prepared separator has attapulgite: polyacrylonitrile oxide: polyvinyl alcohol = 100:30:2.

[0149] Example 12

[0150] The preparation method of Example 12 is substantially the same as that of Example 3, except that:

[0151] The polyvinyl alcohol is added in an amount of 4 wt% of the mass of the attapulgite, and the prepared separator has attapulgite: polyacrylonitrile oxide: polyvinyl alcohol = 100:30:4.

[0152] Example 13

[0153] The preparation method of Example 13 is substantially the same as that of Example 3, except that:

[0154] The polyvinyl alcohol is added in an amount of 0.05 wt% of the mass of the attapulgite, and the prepared separator has attapulgite: polyacrylonitrile oxide: polyvinyl alcohol = 100:30:0.05.

[0155] Example 14

[0156] The preparation method of Example 14 is substantially the same as that of Example 3, except that:

[0157] The polyvinyl alcohol is added in an amount of 5 wt% of the mass of the attapulgite, and the prepared separator has attapulgite: polyacrylonitrile oxide: polyvinyl alcohol = 100:30:5.

[0158] Example 15

[0159] The preparation method of Example 15 is substantially the same as that of Example 3, except that:

[0160] The precursor composite material is heated to an oxidation temperature of 250°C and kept in the tube furnace for 40 min.

[0161] Example 16

[0162] The preparation method of Example 16 is substantially the same as that of Example 3, except that:

[0163] The precursor composite material is heated to an oxidation temperature of 280°C and kept in the tube furnace for 40 min.

[0164] Example 17

[0165] The preparation method of Example 17 is substantially the same as that of Example 3, except that:

[0166] The precursor composite material was heated to an oxidation temperature of 290°C and held in the tube furnace for 35 min.

[0167] Example 18

[0168] The preparation method of Example 18 was substantially the same as that of Example 3, except that:

[0169] The precursor composite material was heated to an oxidation temperature of 320°C and held in the tube furnace for 25 min.

[0170] Example 19

[0171] The preparation method of Example 19 was substantially the same as that of Example 3, except that:

[0172] The precursor composite material was heated to an oxidation temperature of 350°C and held in the tube furnace for 20 min.

[0173] Comparative Example 1

[0174] The preparation method of Comparative Example 1 was substantially the same as that of Example 1, except that:

[0175] The amount of polyacrylonitrile powder added was 0 wt%.

[0176] Comparative Example 2

[0177] The preparation method of Comparative Example 2 was substantially the same as that of Example 1, except that:

[0178] The amount of polyacrylonitrile powder added was 0 wt%, and the amount of polyvinyl alcohol added was 0 wt%.

[0179] Comparative Example 3

[0180] The preparation method of Comparative Example 3 was substantially the same as that of Example 1, except that:

[0181] The precursor composite material was not oxidized.

[0182] The button-type all-solid-state batteries of Examples 1-19 and Comparative Examples 1-3 were respectively tested for EIS at room temperature, and the ionic conductivity was calculated according to the formula, and the results are shown in Table 1. The longitudinal thermal shrinkage and transverse thermal shrinkage of the separators of Examples 1-19 and Comparative Examples 1-3 were respectively tested, so as to characterize the thermal stability performance of the separators, and the results are shown in Table 1.

[0183] The ionic conductivity test method was as follows:

[0184] The ionic conductivity of the separator was calculated according to the following formula:

[0185]

[0186] In the formula, L represents the thickness of the separator; R represents the resistance of the separator; and A represents the effective contact area of the test electrode. R is the resistance of the separator disc (19 mm in diameter) impregnated with electrolyte, which is sandwiched between two steel sheets as the working electrode and the reference electrode, respectively, to form a steel sheet / separator / steel sheet system. The impedance of the system is measured by an electrochemical workstation by an alternating current impedance method under the following conditions: the frequency range is set to 100000 Hz-1 Hz; and the amplitude is set to 5 mV.

[0187] The solvent of the above electrolyte is EC+EMC+DMC in a mass ratio of 1:1:1, and then LiPF6 and additive VC are added. The mass ratio of LiPF6 in the electrolyte is 9%, and the mass ratio of VC in the electrolyte is 3%.

[0188] The longitudinal thermal shrinkage and transverse thermal shrinkage test method is as follows:

[0189] Test instrument: image instrument; oven.

[0190] Test method: The size of each separator sample before baking in the MD and TD directions is tested by the image instrument. The separator is clamped with A4 paper and placed in an oven at 110°C for 12 hours. The size of each separator sample in the MD and TD directions after baking is tested by the image instrument, and the MD and TD size change rates before and after baking are calculated.

[0191] Table 1

[0192] Ionic conductivity (mS / cm) Longitudinal heat shrinkage (%) Transverse heat shrinkage (%) Example 1 3.98 2.70 0.59 Example 2 4.67 2.05 0.51 Example 3 4.32 1.64 0.48 Example 4 4.03 0.93 0.36 Example 5 3.64 0.65 0.15 Example 6 3.10 0.54 0.06 Example 7 2.09 2.91 0.66 Example 8 2.64 0.87 0.23 Example 9 3.87 2.81 0.62 Example 10 4.23 2.54 0.49 Example 11 4.30 2.45 0.44 Example 12 3.90 2.86 0.65 Example 13 2.86 2.97 0.64 Example 14 2.94 2.90 0.61 Example 15 4.13 1.73 0.52 Example 16 4.40 1.62 0.46 Example 17 4.48 1.59 0.43 Example 18 4.52 1.55 0.41 Example 19 4.58 1.52 0.39 Comparative Example 1 2.03 3.34 0.75 Comparative Example 2 1.79 3.53 0.80 Comparative Example 3 1.78 3.54 0.81

[0193] As can be seen from Table 1, compared with Comparative Examples 1-3, the ionic conductivity of the separators of Examples 1-19 is obviously improved, and the longitudinal thermal shrinkage and transverse thermal shrinkage of the separators of Examples 1-19 are obviously reduced, i.e., the thermal stability of the separators of Examples 1-19 is obviously improved. It can be seen that the ionic conductivity and thermal stability of the separators can be obviously improved by introducing polyvinyl alcohol and polyacrylonitrile oxide into the attapulgite.

[0194] As can be seen from Table 1, compared with Examples 7 and 8, the comprehensive performance of Examples 1-6 is more excellent. It can be seen that the comprehensive performance of the separators can be improved by limiting the addition amount of the polyacrylonitrile powder to 10wt%-60wt% of the mass of the attapulgite. As can be seen from Table 1, compared with Examples 1 and 5-6, the comprehensive performance of Examples 2-4 is more excellent. It can be seen that the comprehensive performance of the separators can be further improved by limiting the addition amount of the polyacrylonitrile powder to 20wt%-40wt% of the mass of the attapulgite.

[0195] It can be seen from Table 1 that, compared with Example 13, Example 14, the ion conductivity of Example 3, Example 9-12 is improved, and the longitudinal thermal shrinkage and the transverse thermal shrinkage of Example 3, Example 9-12 are reduced. It can be seen that, by limiting the polyvinyl alcohol addition amount in the range of 0.1wt%-4wt% of the mass of the attapulgite, the ion conductivity and thermal stability of the separator can be improved. It can be seen from Table 1 that, compared with Example 9, Example 12, the ion conductivity of Example 3, Example 10-11 is further improved, and the longitudinal thermal shrinkage and the transverse thermal shrinkage of Example 3, Example 10-11 are further reduced. It can be seen that, by limiting the polyvinyl alcohol addition amount in the range of 0.5wt%-2wt% of the mass of the attapulgite, the ion conductivity and thermal stability of the separator can be further improved.

[0196] It can be seen from Table 1 that, compared with Example 15, the ion conductivity of Example 3, Example 16-19 is further improved, and the longitudinal thermal shrinkage and the transverse thermal shrinkage of Example 3, Example 16-19 are further reduced. It can be seen that, by limiting the oxidation temperature in the range of 280℃-350℃, the ion conductivity and thermal stability of the separator can be further improved.

[0197] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, different embodiments or examples described in the present specification and the features of different embodiments or examples can be combined and combined by those skilled in the art without contradiction.

[0198] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application.

Claims

1. A diaphragm, characterized in that: include: 100 parts by weight of attapulgite, 10 to 60 parts by weight of polyacrylonitrile oxide and 0.1 to 4 parts by weight of polyvinyl alcohol, The preparation steps of the diaphragm include: preparing a polyacrylonitrile / polyvinyl alcohol / attapulgite suspension; performing solid-liquid separation on the polyacrylonitrile / polyvinyl alcohol / attapulgite suspension to obtain a solid portion; drying the solid portion to obtain a precursor composite material; oxidizing the precursor composite material to obtain a diaphragm material; The membrane material is prepared into a membrane.

2. The diaphragm according to claim 1, characterized in that include: 100 parts by weight of attapulgite, 20-40 parts by weight of polyacrylonitrile oxide and 0.5-2 parts by weight of polyvinyl alcohol.

3. The diaphragm according to claim 1 or 2, characterized in that The lithium ion conductivity of the separator is 3.0 mS / cm to 4.7 mS / cm.

4. The diaphragm according to claim 1 or 2, characterized in that The longitudinal heat shrinkage rate of the diaphragm does not exceed 2.7%; And / or, the transverse heat shrinkage rate of the diaphragm does not exceed 0.6%.

5. A method for preparing a diaphragm according to any one of claims 1 to 4, characterized in that: include: preparing a polyacrylonitrile / polyvinyl alcohol / attapulgite suspension; performing solid-liquid separation on the polyacrylonitrile / polyvinyl alcohol / attapulgite suspension to obtain a solid portion; drying the solid portion to obtain a precursor composite material; oxidizing the precursor composite material to obtain a diaphragm material; The membrane material is prepared into a membrane.

6. The method for preparing a diaphragm according to claim 5, wherein: The preparation of the polyacrylonitrile / polyvinyl alcohol / attapulgite suspension comprises: preparing an attapulgite suspension; adding the polyvinyl alcohol solution to the attapulgite suspension to obtain a polyvinyl alcohol / attapulgite suspension; The polyacrylonitrile solution is added to the polyvinyl alcohol / attapulgite suspension to obtain the polyacrylonitrile / polyvinyl alcohol / attapulgite suspension.

7. The method for preparing a diaphragm according to claim 6, wherein: The mass fraction of attapulgite in the attapulgite suspension is 5% to 20%; And / or, the concentration of polyvinyl alcohol in the polyvinyl alcohol solution is 5 g / L to 15 g / L; And / or, the concentration of polyacrylonitrile in the polyacrylonitrile solution is 5 g / L to 15 g / L.

8. The method for preparing a diaphragm according to claim 5, wherein: In the polyacrylonitrile / polyvinyl alcohol / attapulgite suspension, the mass ratio of the attapulgite, the polyacrylonitrile and the polyvinyl alcohol is 100:(10-60):(0.1-4).

9. The method for preparing a diaphragm according to claim 5, wherein: In the polyacrylonitrile / polyvinyl alcohol / attapulgite suspension, the mass ratio of the attapulgite, the polyacrylonitrile and the polyvinyl alcohol is 100:(20-40):(0.5-2).

10. The method for preparing a diaphragm according to claim 5, characterized in that: The drying of the solid portion comprises: placing the solid portion in an ultra-low temperature environment for freezing, and then freeze-drying; The temperature of the ultra-low temperature environment is -70°C to -90°C, and the freezing time in the ultra-low temperature environment is 6h to 24h; The freeze-drying temperature is -30°C to -50°C, and the freeze-drying vacuum degree is 5Pa to 20Pa.

11. The method for preparing a diaphragm according to any one of claims 5 to 10, characterized in that: The oxidation temperature is 280°C to 350°C, and the oxidation time at the oxidation temperature is 20min to 40min; The precursor composite material is heated to the oxidation temperature at a heating rate not exceeding 5° C. / min.

12. A battery, characterized in that: A diaphragm according to any one of claims 1 to 4 or a diaphragm prepared by the method for preparing the diaphragm according to any one of claims 5 to 11.

13. An electrical device, characterized in that: Including the battery according to claim 12.

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