Isolation film, battery cell, battery, and power using device

Abstract

The application discloses an isolation film, a battery monomer, a battery and a power utilization device. The isolation film comprises a porous base material and a ferroelectric coating layer on at least one surface of the porous base material, wherein the ferroelectric coating layer comprises a ferroelectric material, the ferroelectric material comprises an inorganic ferroelectric and a ferroelectric polymer, the ferroelectric polymer comprises polyvinylidene fluoride and a copolymer thereof, the ferroelectric polymer comprises beta-phase polyvinylidene fluoride, and the content of the beta-phase polyvinylidene fluoride in the ferroelectric polymer is greater than or equal to 60%. The isolation film can slow down the continuous growth of dendrites in the vertical electrode direction, reduce internal short circuit of the battery, improve the reliability of the battery, and also improve the coulomb efficiency and rate performance of the battery.

Description

Technical Field

[0001] This application relates to a separator, a battery cell, a battery, and an electrical device. Background Technology

[0002] In recent years, batteries have been widely used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, as well as in consumer electronics, power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and many other fields. With the increasing application and promotion of batteries, their reliability has received growing attention. During battery charging and discharging, dendrite growth on the negative electrode is one of the important factors affecting battery reliability and lifespan. How to slow down dendrite growth without affecting battery performance is a pressing technical problem that needs to be solved. The above statements are only for providing background information related to this application and do not necessarily constitute prior art. Summary of the Invention

[0003] This application provides a separator, a battery cell, a battery, and an electrical device. The separator can slow down the continuous growth of dendrites in the direction perpendicular to the electrode, reduce internal short circuits in the battery, improve battery reliability, and also improve the battery's coulombic efficiency and rate performance.

[0004] A first aspect of this application provides a separator membrane comprising a porous substrate and a ferroelectric coating on at least one surface of the porous substrate. The ferroelectric coating comprises a ferroelectric material, which includes inorganic ferroelectrics and ferroelectric polymers. The ferroelectric polymer comprises polyvinylidene fluoride (PVDF) and its copolymers, and includes β-phase PVDF. The content of β-phase PVDF in the ferroelectric polymer is greater than or equal to 60%.

[0005] The ferroelectric polymer provided in this application embodiment can act as a binder and also has a high dielectric constant ε. r This can also slow down the continuous growth of dendrites in the direction perpendicular to the electrode and reduce internal short circuits in the battery. When applied to batteries, it can improve battery reliability, coulombic efficiency and rate performance.

[0006] In any embodiment, the content of β-phase polyvinylidene fluoride in the ferroelectric polymer is greater than or equal to 80%, and optionally greater than or equal to 90%.

[0007] This can further slow down the continuous growth of dendrites in the direction perpendicular to the electrode, reduce internal short circuits in the battery, and improve the battery's coulombic efficiency and rate performance.

[0008] In any embodiment, the dielectric constant ε of the ferroelectric coating r The dielectric constant ε of the inorganic ferroelectric material is greater than that of the inorganic ferroelectric material. r Optionally, the dielectric constant ε of the ferroelectric coating is...r With respect to the dielectric constant ε of the inorganic ferroelectric material r The ratio is greater than or equal to 1.6, and can also be greater than or equal to 2.0.

[0009] This can further slow down the continuous growth of dendrites in the direction perpendicular to the electrode, reduce internal short circuits in the battery, and improve the battery's coulombic efficiency and rate performance.

[0010] In any embodiment, the dielectric constant ε of the inorganic ferroelectric material r The dielectric constant ε of the ferroelectric polymer is greater than that of the ferroelectric polymer. r .

[0011] In any embodiment, the dielectric constant ε of the inorganic ferroelectric material r The range is 200-8000, with an optional range of 2000-6000.

[0012] In any embodiment, the dielectric constant ε of the ferroelectric polymer r The range is 5-100, with an option of 8-70.

[0013] In any embodiment, at least a portion of the ferroelectric polymer is located on at least a portion of the surface of the inorganic ferroelectric.

[0014] When ferroelectric polymers are located on at least a portion of the surface of inorganic ferroelectric materials, the probability of the ferroelectric coating losing its ferroelectricity due to the ferroelectric-paraelectric transition of the inorganic ferroelectric material during separator preparation can be further reduced. This can better slow down the continuous growth of dendrites in the direction perpendicular to the electrode, and also helps to improve the coulombic efficiency of the battery. When ferroelectric polymers are located on at least a portion of the surface of inorganic ferroelectric materials, they also contribute to the dielectric constant ε of the ferroelectric coating. r It is greater than the dielectric constant ε of inorganic ferroelectrics r It is also greater than the dielectric constant ε of ferroelectric polymers. r .

[0015] In any embodiment, the weight content of the inorganic ferroelectric in the ferroelectric material is 80%-99%, and optionally 85%-95%.

[0016] In any embodiment, the weight content of the ferroelectric polymer in the ferroelectric material is 1%-20%, optionally 5%-15%.

[0017] By adjusting the weight content of inorganic ferroelectrics and ferroelectric polymers in the ferroelectric material within the above-mentioned range, the dielectric constant ε of the ferroelectric coating can be increased. r This makes the dielectric constant ε of the ferroelectric coating... r It is greater than the dielectric constant ε of inorganic ferroelectrics r It is also greater than the dielectric constant ε of ferroelectric polymers. rThis can better slow down the continuous growth of dendrites in the direction perpendicular to the electrode, reduce internal short circuits in the battery, and improve the battery's reliability and coulombic efficiency; in addition, it can also increase the adhesion between the ferroelectric coating and the porous structure.

[0018] In any embodiment, the Curie temperature of the ferroelectric polymer is 150℃-250℃, and can be selected as 160℃-200℃.

[0019] In any embodiment, the remanent polarization of the ferroelectric polymer is 10 mC / m. 2 -1000mC / m 2 20mC / m is optional 2 -800mC / m 2 .

[0020] In any embodiment, the weight-average molecular weight of the ferroelectric polymer is 200,000-800,000, and optionally 400,000-650,000.

[0021] When the weight-average molecular weight of the ferroelectric polymer is within the above range, it can give the ferroelectric polymer suitable crystallinity, suitable Curie temperature, and high dielectric constant ε. r It can also give ferroelectric polymers suitable viscosity.

[0022] In any embodiment, the melting temperature of the ferroelectric polymer is 140℃-220℃, and optionally 143℃-200℃.

[0023] The melting point of ferroelectric polymers is within the above range, which allows them to possess suitable crystallinity, suitable Curie temperature, and high dielectric constant ε. r It can also give ferroelectric polymers suitable viscosity.

[0024] In any embodiment, the crystallinity of the ferroelectric polymer is greater than or equal to 45%, and can be selected as 45%-68%. A crystallinity within the above range can reduce the thermal shrinkage rate of the separator and improve its mechanical strength.

[0025] In any embodiment, the Curie point temperature of the inorganic ferroelectric is 110℃-150℃, and can be selected as 120℃-140℃.

[0026] In any embodiment, the ferroelectric polymer includes one or more of polyvinylidene fluoride, copolymers of polyvinylidene fluoride monomer and other monomers.

[0027] Optionally, the other monomers include one or more of trifluoroethylene, trifluorochloroethylene, fluorinated acetylene, and hexafluoropropylene.

[0028] Optionally, the copolymer of the vinylidene fluoride monomer with other monomers includes one or more of the following: vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-trifluoroethylene-trifluorochloroethylene copolymer, vinylidene fluoride-trifluoroethylene-trifluorochloroethylene-fluorinated acetylene copolymer, and vinylidene fluoride-hexafluoropropylene copolymer.

[0029] In any embodiment, the inorganic ferroelectric material includes one or more of the following: perovskite type, tungsten bronze type, bismuth layered type, pyrochlore type, niobate type, and lithium lead barium niobate.

[0030] In any embodiment, the volumetric particle size Dv50 of the inorganic ferroelectric is 0.05μm-5μm, and can be selected as 0.1μm-1μm.

[0031] When the volume distribution particle size Dv50 of inorganic ferroelectrics is within the above range, the ferroelectric coating slurry can have a suitable viscosity, which is convenient for coating and can improve the uniformity and consistency of the ferroelectric coating. It can also increase the adhesion between the ferroelectric coating and the porous structure, reducing the "powdering" phenomenon. In addition, it can reduce the problem of pore blockage and improve the air permeability and ion transport characteristics of the separator.

[0032] In any embodiment, the volumetric particle size Dv50 of the ferroelectric polymer is 10nm-150nm, and can be selected as 15nm-50nm.

[0033] In any embodiment, the thickness of the ferroelectric coating is 1 μm-3.5 μm, optionally 1.5 μm-3 μm. This allows the battery to possess high reliability, high coulombic efficiency, and good rate performance.

[0034] In any embodiment, the areal density of the ferroelectric coating is 2.5 g / m³. 2 -15g / m 2 3g / m 2 -12g / m 2 This allows the battery to possess high reliability, high coulombic efficiency, and good rate performance.

[0035] In any embodiment, the ferroelectric coating further includes a dispersant and / or a thickener.

[0036] In any embodiment, the dispersant comprises one or more of hydrolyzed polymaleic anhydride, polyacrylic acid, acrylic block copolymer, polyester block copolymer, polyethylene glycol polyol, polyethyleneimine, and derivatives thereof.

[0037] In any embodiment, the ratio of the total weight of the ferroelectric material to the weight of the dispersant is 1:(0.01-0.02), and optionally 1:(0.010-0.015).

[0038] An appropriate amount of dispersant can make the ferroelectric coating slurry disperse evenly, which is convenient for coating and also helps to increase the film weight of the ferroelectric coating.

[0039] In any embodiment, the thickener includes one or more of sodium carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, polyacrylate, polyurethane, and polyether.

[0040] In any embodiment, the ratio of the total weight of the ferroelectric material to the weight of the thickener is 1:(0.01-0.02), and optionally 1:(0.010-0.015).

[0041] An appropriate amount of thickener can improve the stability of the ferroelectric coating slurry, facilitate coating, and also help increase the film weight of the ferroelectric coating.

[0042] In any embodiment, the ferroelectric coating is located on one surface of the porous substrate, and a ceramic coating is disposed on the other surface of the porous substrate. When used in a battery, the ferroelectric coating faces the negative electrode, and the ceramic coating faces the positive electrode.

[0043] In any embodiment, the thickness of the porous substrate is 4μm-15μm, and optionally 5μm-10μm.

[0044] In any embodiment, the porous substrate includes one or more of polyolefins, halogenated polyolefins, polyamides, polyesters, and their respective derivatives.

[0045] A second aspect of this application provides a battery cell that includes the separator of the first aspect of this application.

[0046] A third aspect of this application provides a battery comprising the battery cell of the third aspect of this application.

[0047] The fourth aspect of this application provides an electrical device that includes the battery of the third aspect of this application.

[0048] The electrical device of this application includes the battery provided in this application, and therefore has at least the same advantages as the battery. Attached Figure Description

[0049] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly described below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0050] Figure 1 The diagram shows a schematic of a battery cell provided in some embodiments of this application.

[0051] Figure 2 An exploded view of a battery cell provided in some embodiments of this application is shown.

[0052] Figure 3 This document shows schematic diagrams of battery modules provided in some embodiments of this application.

[0053] Figure 4 This illustration shows a schematic diagram of a battery pack provided in some embodiments of this application.

[0054] Figure 5 yes Figure 4 The diagram shown is an exploded view of the battery pack.

[0055] Figure 6 A schematic diagram of the isolation membrane provided in some embodiments of this application is shown.

[0056] Figure 7 A schematic diagram of the isolation membrane provided in some other embodiments of this application is shown.

[0057] Figure 8 This illustration shows a schematic diagram of the isolation membrane provided in some embodiments of this application.

[0058] Figure 9 A schematic diagram of an electrical device provided in some embodiments of this application is shown.

[0059] Figure 10 The image shows a scanning electron microscope (SEM) image of the isolation membrane prepared in Example 1.

[0060] In the accompanying drawings, the figures may not be drawn to scale. The reference numerals are explained as follows: 1 Battery pack, 2 Upper housing, 3 Lower housing, 4 Battery module, 5 Battery, 51 Housing, 52 Electrode assembly, 53 Cover plate, 10 Separator, 101 Porous substrate, 102 Ferroelectric coating, 103 Second coating. Detailed Implementation

[0061] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the separator, battery cell, battery, and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0062] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0063] Unless otherwise specified, all embodiments and optional embodiments of this application may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

[0064] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions, and such technical solutions shall be deemed to be included in the disclosure of this application.

[0065] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0066] In this application, the terms "multiple" or "various" refer to two or more kinds.

[0067] In the description of the embodiments of this application, unless otherwise specified, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0068] Unless otherwise stated, the terms used in this application have the common meanings as commonly understood by those skilled in the art.

[0069] Unless otherwise stated, the values ​​of the parameters mentioned in this application can be determined using various testing methods commonly used in the art, for example, according to the testing methods given in the embodiments of this application. Unless otherwise stated, the test temperature for each parameter is 25°C.

[0070] The Dv50 of a material has a meaning known in the art and can be determined using instruments and methods known in the art. For example, it can be conveniently determined using a laser particle size analyzer (such as the Malvern Mastersizer 3000) in accordance with GB / T 19077-2016. The physical definition of Dv50 is the particle size corresponding to a cumulative volume distribution percentage of 50% for the material.

[0071] The battery mentioned in the embodiments of this application can be a single physical module comprising one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in this application can include battery cells, battery modules, or battery packs.

[0072] A battery cell is the smallest unit that makes up a battery, and it can independently perform the functions of charging and discharging. A battery cell can be cylindrical, cuboid, or other shapes, etc., and the embodiments of this application are not limited in this respect. Figure 1 The example shown is a rectangular battery cell 5.

[0073] When there are multiple battery cells, they are connected in series, parallel, or mixed via a busbar. In some embodiments, the battery can be a battery module; when there are multiple battery cells, they are arranged and fixed to form a battery module. In some embodiments, the battery can be a battery pack, which includes a housing and battery cells, with the battery cells or battery modules housed within the housing. In some embodiments, the housing can be part of the vehicle's chassis structure. For example, a portion of the housing can be at least part of the vehicle's floor, or a portion of the housing can be at least part of the vehicle's crossbeams and longitudinal beams.

[0074] In some embodiments, the battery can be an energy storage device. Energy storage devices include energy storage containers, energy storage cabinets, etc.

[0075] A single battery cell generally includes an electrode assembly and an electrolyte. The electrode assembly can be a wound structure or a stacked structure, and the embodiments of this application are not limited in this regard.

[0076] The battery cell may also include an outer packaging, which can be used to encapsulate the electrode components and electrolyte. The outer packaging can be a rigid shell, such as a hard plastic shell, aluminum shell, or steel shell. The outer packaging can also be a flexible package, such as a pouch-type flexible package. The material of the flexible package can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0077] In some embodiments, such as Figure 2 As shown, the outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates enclosing a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 is used to cover the opening to close the receiving cavity. Electrode assemblies 52 are encapsulated in the receiving cavity. The number of electrode assemblies 52 contained in the battery cell 5 may be one or more, and can be adjusted according to requirements.

[0078] In some embodiments, individual battery cells can be assembled into a battery module, and the number of individual battery cells contained in the battery module can be multiple, the specific number of which can be adjusted according to the application and capacity of the battery module. Figure 3 This is a schematic diagram of battery module 4 as an example. Figure 3 As shown, in battery module 4, multiple battery cells 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple battery cells 5 can be fixed in place using fasteners.

[0079] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0080] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0081] Figure 4 and Figure 5 This is a schematic diagram of battery pack 1 as an example. Figure 4 and Figure 5As shown, the battery pack 1 may include a housing and multiple battery modules 4 disposed within the housing. The housing includes an upper housing 2 and a lower housing 3. The upper housing 2 covers the lower housing 3, forming a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the housing.

[0082] The battery cells provided in the embodiments of this application may include lithium battery cells and sodium battery cells, such as lithium-ion battery cells, lithium metal battery cells, negative electrode-free lithium metal battery cells, sodium-ion battery cells, sodium metal battery cells, negative electrode-free sodium metal battery cells, etc.

[0083] A negative electrode-free battery cell typically refers to a battery cell in which no negative electrode active material layer is actively formed on the negative electrode side during the battery cell manufacturing process. For example, the negative electrode active material layer is not formed at the negative electrode through coating or deposition processes, or it is formed from a carbonaceous active material layer. During the first charge, ions gain electrons on the negative electrode side and deposit metal on the surface of the negative electrode current collector. During discharge, the metal can be converted back into ions and return to the positive electrode, achieving cyclic charging and discharging. Compared to other battery cells, a negative electrode-free battery cell can achieve a higher energy density due to the absence of a negative electrode active material layer. In some embodiments, to improve battery cell performance, some conventional materials that can be used as negative electrode active materials, such as carbon materials, can also be placed on the negative electrode side of the negative electrode-free battery cell. Although these materials have a certain capacity, because their content is small and they are not used as the main negative electrode active material in the battery cell, such a battery cell can still be considered a negative electrode-free battery cell. The Cell Balance (CB) value of a negative electrode-free battery cell is typically very small; for example, in some embodiments, the CB value of a negative electrode-free battery cell can be less than or equal to 0.1. The CB value is the capacity per unit area of ​​the negative electrode divided by the capacity per unit area of ​​the positive electrode in the battery cell. Because a negative electrode-free battery cell contains little or no negative electrode active material, the capacity per unit area of ​​the negative electrode is small, and therefore the CB value is very small, typically less than or equal to 0.1.

[0084] As a crucial component of a battery cell, the separator's performance is vital to the battery's overall performance. Located between the positive and negative electrodes, its primary function is to prevent short circuits. Currently, commercially available batteries typically use porous polyolefin membranes (such as polyethylene and polypropylene). However, these membranes exhibit poor electrolyte wettability and thermal stability. Furthermore, with increasing charge-discharge cycles, dendrites can form at the negative electrode interface. The continued growth of these dendrites can puncture the separator, causing internal short circuits and, in severe cases, even leading to fires or explosions.

[0085] In addition, conventional separators are usually coated with a ceramic coating. However, the ceramic coating usually serves as a physical barrier. As the number of battery charge and discharge cycles increases, there is still a possibility that dendrites will grow along the pores of the ceramic coating and puncture the separator. Therefore, it is not possible to effectively alleviate the dendrite growth problem.

[0086] Therefore, developing a separator with good thermal stability, excellent electrolyte wettability, and the ability to alleviate dendrite growth is a technical problem that urgently needs to be solved in this field.

[0087] Figure 6 A schematic diagram of the isolation membrane provided in some embodiments of this application is shown. Figure 7 A schematic diagram of the isolation membrane provided in some other embodiments of this application is shown. Figure 8 This illustration shows a schematic diagram of the isolation membrane provided in some embodiments of this application.

[0088] like Figures 6 to 8 As shown, the separator 10 includes a porous substrate 101 and a ferroelectric coating 102 located on at least one surface of the porous substrate 101. The ferroelectric coating 102 includes a ferroelectric material, which includes inorganic ferroelectrics and ferroelectric polymers, and the ferroelectric polymer includes polyvinylidene fluoride and copolymers thereof. The ferroelectric polymer includes β-phase polyvinylidene fluoride, and the content of β-phase polyvinylidene fluoride in the ferroelectric polymer is greater than or equal to 60%.

[0089] Porous substrates are highly hydrophobic, while electrolytes typically use polar solvents, resulting in poor electrolyte wettability and high ion transport impedance in porous substrates. The ferroelectric coating introduced in the separator provided in the embodiments of this application includes inorganic ferroelectrics and ferroelectric polymers, which can improve the compatibility between the separator and the electrolyte, enhance the separator's wettability to the electrolyte, and reduce the separator's ion transport impedance, thereby contributing to good cycle performance and rate performance of the battery. Furthermore, the ferroelectric coating introduced in the separator provided in the embodiments of this application can also improve the separator's heat resistance and mechanical strength.

[0090] During the reduction deposition of ions at the negative electrode, stress accumulation occurs due to localized volume expansion. Inorganic ferroelectrics possess high dielectric constants and spontaneous polarization. Under stress and influenced by an electric field, they spontaneously polarize, causing the positive charge centers of the inorganic ferroelectrics to move towards the electron accumulation region of the negative electrode, thus encapsulating the electron accumulation region. Simultaneously, because the positive charge centers of the inorganic ferroelectrics are positively charged, they repel the positively charged ions on the dendrite surface, thereby altering the dendrite growth direction, slowing down dendrite growth perpendicular to the electrode, and reducing internal short circuits in the battery. However, the Curie temperature of inorganic ferroelectrics is typically low. During separator preparation, a ferroelectric-paraelectric transition may occur, causing the ferroelectric coating to lose its ferroelectricity and leading to failure. Furthermore, inorganic ferroelectrics in separator coatings often suffer from uneven distribution and low content.

[0091] Typical representatives of polyvinylidene fluoride (PVDF) are α-phase PVDF and β-phase PVDF. α-phase PVDF is a monoclinic crystal system with a TGTG arrangement, exhibiting zero net dipole moment and no polarity. β-phase PVDF is an orthorhombic crystal system with a TTTT all-inverse arrangement, possessing a large spontaneous polarization intensity and easily polarizing under an external electric field, thus exhibiting excellent dielectric properties. Currently, the binders used in separator coatings are mostly α-phase PVDF, which does not possess ferroelectric properties.

[0092] The ferroelectric polymer in the ferroelectric coating of the separator provided in this application embodiment includes β-phase polyvinylidene fluoride, and the content of β-phase polyvinylidene fluoride in the ferroelectric polymer is greater than or equal to 60%. Therefore, the ferroelectric polymer provided in this application embodiment can act as an adhesive and also has a high dielectric constant ε. r This can also slow down the continuous growth of dendrites in the direction perpendicular to the electrode and reduce short circuits inside the battery.

[0093] By incorporating ferroelectric polymers and inorganic ferroelectric materials into the ferroelectric coating, the probability of the ferroelectric coating losing its ferroelectricity due to the ferroelectric-paraelectric transition of the inorganic ferroelectric material during the preparation of the separator can be reduced. This can effectively slow down the continuous growth of dendrites in the direction perpendicular to the electrode. Furthermore, the dendrite growth process may generate "dead lithium" and "dead sodium," which can significantly reduce the battery's capacity and coulombic efficiency. Therefore, the separator provided in this application embodiment can also improve the battery's coulombic efficiency, especially at high rates.

[0094] Therefore, the separator provided in this application embodiment can slow down dendrite growth and also has good electrolyte wettability, low ion transport impedance, low thermal shrinkage rate and high mechanical strength. When applied to batteries, it can improve the reliability, coulombic efficiency and rate performance of the batteries.

[0095] In some embodiments, the content of β-phase polyvinylidene fluoride in the ferroelectric polymer can be greater than or equal to 80%, and optionally greater than or equal to 90%. This can further slow down the continuous growth of dendrites in the direction perpendicular to the electrode, reduce internal short circuits in the battery, and improve the coulombic efficiency and rate performance of the battery.

[0096] In some embodiments, the ferroelectric polymer may also contain small amounts of α-phase polyvinylidene fluoride and / or γ-phase polyvinylidene fluoride.

[0097] Optionally, the content of α-phase polyvinylidene fluoride in the ferroelectric polymer can be less than or equal to 20%.

[0098] Optionally, the content of γ-phase polyvinylidene fluoride in the ferroelectric polymer can be less than or equal to 10%.

[0099] The contents of β-phase polyvinylidene fluoride, α-phase polyvinylidene fluoride, and γ-phase polyvinylidene fluoride in ferroelectric polymers can be calculated using FTIR infrared absorption spectroscopy.

[0100]

[0101] F a =100% - F (β，γ)

[0102]

[0103]

[0104] F α This indicates the content of the α phase in the ferroelectric polymer.

[0105] F β This indicates the content of the β phase in the ferroelectric polymer.

[0106] F γ This indicates the content of the γ phase in the ferroelectric polymer.

[0107] A m This represents the peak intensity of the absorption peak at different wavelengths m. The peak intensity of each absorption peak can be represented by the integral area of ​​each absorption peak.

[0108] K m This represents the absorption coefficient of the absorption peak at different wavelengths m.

[0109] In some embodiments, the dielectric constant ε of the ferroelectric coating r The dielectric constant ε of inorganic ferroelectrics is greater than that of inorganic ferroelectrics. r .

[0110] Optionally, the dielectric constant ε of the ferroelectric coating r The dielectric constant ε of inorganic ferroelectrics r The ratio can be greater than or equal to 1.6, and can also be greater than or equal to 2.0.

[0111] The dielectric constant ε of the ferroelectric coating of the isolation membrane provided in this application embodiment r The dielectric constant ε of inorganic ferroelectrics is greater than that of inorganic ferroelectrics. r This can further slow down the continuous growth of dendrites in the direction perpendicular to the electrode, reduce internal short circuits in the battery, improve battery reliability, and also improve the battery's coulombic efficiency and rate performance.

[0112] In some embodiments, the dielectric constant ε of inorganic ferroelectrics r The dielectric constant ε of the ferroelectric polymer is greater than that of the polymer. r .

[0113] In some embodiments, the dielectric constant ε of inorganic ferroelectrics r It can range from 200 to 8000, and can be selected from 2000 to 6000.

[0114] In some embodiments, the dielectric constant ε of the ferroelectric polymer r It can be 5-100, or optionally 8-70.

[0115] The dielectric constant ε of the above ferroelectric coating r The dielectric constant ε of inorganic ferroelectrics r The dielectric constant ε of ferroelectric polymers r The following method can be used for testing: At 25℃, take an appropriate amount of sample powder, coat both sides with aluminum foil, place it in a mold, and press it into a disc using a powder tablet press at a pressure of 2 MPa for 2 minutes. After pressing, remove the sample disc and use a precision digital bridge instrument to measure the dielectric constant ε in the frequency range of 20Hz-2MHz. r test.

[0116] The dielectric constant mentioned in this application is the relative dielectric constant ε. r .

[0117] The dielectric constant ε of the ferroelectric coating was tested. r During the preparation of the separator membrane, samples can be taken for analysis, or an appropriate amount of ferroelectric coating powder can be obtained from the dried finished separator membrane. For example, an appropriate amount of ferroelectric coating powder can be obtained by scraping powder samples.

[0118] By adjusting parameters such as the distribution morphology, weight content, particle size, and β-phase content of inorganic ferroelectrics and ferroelectric polymers in the ferroelectric coating, the inorganic ferroelectrics and ferroelectric polymers can exert a synergistic effect, thereby increasing the dielectric constant ε of the ferroelectric coating. r It is greater than the dielectric constant ε of inorganic ferroelectrics r It is also greater than the dielectric constant ε of ferroelectric polymers. r .

[0119] In some embodiments, at least a portion of the ferroelectric polymer in the ferroelectric coating is located on at least a portion of the surface of the inorganic ferroelectric body. When the ferroelectric polymer is located on at least a portion of the surface of the inorganic ferroelectric body, the probability of the ferroelectric coating losing its ferroelectricity due to the ferroelectric-paraelectric transition of the inorganic ferroelectric body during separator preparation can be further reduced. This can better slow down the continuous growth of dendrites in the direction perpendicular to the electrode, and also helps to improve the coulombic efficiency of the battery. When the ferroelectric polymer is located on at least a portion of the surface of the inorganic ferroelectric body, it also contributes to the dielectric constant ε of the ferroelectric coating. r It is greater than the dielectric constant ε of inorganic ferroelectrics r It is also greater than the dielectric constant ε of ferroelectric polymers. r .

[0120] In some embodiments, the weight content of inorganic ferroelectrics in the ferroelectric material can be 80%-99%, and optionally 85%-95%.

[0121] In some embodiments, the weight content of the ferroelectric polymer in the ferroelectric material can be 1%-20%, optionally 5%-15%.

[0122] By adjusting the weight content of inorganic ferroelectrics and ferroelectric polymers in the ferroelectric material within the above-mentioned range, the dielectric constant ε of the ferroelectric coating can be increased. r This makes the dielectric constant ε of the ferroelectric coating... r It is greater than the dielectric constant ε of inorganic ferroelectrics r It is also greater than the dielectric constant ε of ferroelectric polymers. r This can better slow down the continuous growth of dendrites in the direction perpendicular to the electrode, reduce internal short circuits in the battery, and improve the battery's reliability and coulombic efficiency; in addition, it can also increase the adhesion between the ferroelectric coating and the porous structure.

[0123] In some embodiments, the Curie temperature of the ferroelectric polymer can be 150°C-250°C, and optionally 160°C-200°C.

[0124] In some embodiments, the remanent polarization of the ferroelectric polymer can be 10 mC / m. 2 -1000mC / m 2 20mC / m is optional 2 -800mC / m 2 .

[0125] In some embodiments, the weight-average molecular weight of the ferroelectric polymer can be 200,000 to 800,000, and optionally 400,000 to 650,000.

[0126] When the weight-average molecular weight of the ferroelectric polymer is within the above range, it can give the ferroelectric polymer suitable crystallinity, suitable Curie temperature, and high dielectric constant ε. r It can also give ferroelectric polymers suitable viscosity.

[0127] The weight-average molecular weight of ferroelectric polymers has a meaning well-known in the art and can be measured using methods known in the art. For example, it can be tested by gel permeation chromatography (GPC).

[0128] In some embodiments, the melting temperature of the ferroelectric polymer can be 140°C-220°C, and optionally 143°C-200°C.

[0129] The melting point of ferroelectric polymers is within the above range, which allows them to possess suitable crystallinity, suitable Curie temperature, and high dielectric constant ε. rIt can also give ferroelectric polymers suitable viscosity.

[0130] The melting temperature of ferroelectric polymers can be measured using differential scanning calorimetry (DSC). The test temperature range is from 25°C to 400°C, and the heating rate can be 10°C / minute.

[0131] In some embodiments, the crystallinity of the ferroelectric polymer can be greater than or equal to 45%, optionally 45%-68%. A crystallinity within the above range can reduce the thermal shrinkage rate of the separator and improve its mechanical strength.

[0132] In some embodiments, the ferroelectric polymer may include one or more of polyvinylidene fluoride (i.e., polyvinylidene fluoride VDF monomer homopolymer, abbreviated as PVDF), copolymers of polyvinylidene fluoride monomer and other monomers.

[0133] By introducing other monomers into the VDF crystal region, large-sized ferroelectric domains can be segmented into nanoscale domains. These nanoscale ferroelectric domains readily respond to changes in the external electric field, thus exhibiting unique relaxor ferroelectric behavior, which in turn can increase the dielectric constant ε of the ferroelectric polymer. r Further improvements and a further reduction in dielectric loss.

[0134] Alternatively, other monomers may include, but are not limited to, one or more of trifluoroethylene, trifluorochloroethylene, fluorinated acetylene, and hexafluoropropylene.

[0135] Optionally, the copolymer of vinylidene fluoride monomer with other monomers may include, but is not limited to, one or more of the following: vinylidene fluoride-trifluoroethylene copolymer (abbreviated as P(VDF-TrFE)), vinylidene fluoride-trifluoroethylene-trifluorochloroethylene copolymer (abbreviated as P(VDF-TrFE-CFE)), vinylidene fluoride-trifluoroethylene-trifluorochloroethylene-fluorinated acetylene copolymer (abbreviated as P(VDF-TrFE-CFE-FA)), and vinylidene fluoride-hexafluoropropylene copolymer (abbreviated as P(VDF-HFP)).

[0136] In some embodiments, the volumetric particle size Dv50 of the ferroelectric polymer can be 10nm-150nm, and optionally 15nm-50nm.

[0137] In some embodiments, the volumetric particle size Dv50 of the inorganic ferroelectric can be 0.05 μm-5 μm, and optionally 0.1 μm-1 μm. A volumetric particle size Dv50 within the above range allows the ferroelectric coating slurry to have a suitable viscosity, facilitating coating application and improving the uniformity and consistency of the ferroelectric coating. It also increases the adhesion between the ferroelectric coating and the porous structure, reducing powder shedding. Furthermore, it reduces pore clogging and improves the air permeability and ion transport characteristics of the separator.

[0138] In some embodiments, the Curie point temperature of the inorganic ferroelectric can be 110°C - 150°C, and optionally 120°C - 140°C.

[0139] In some embodiments, the inorganic ferroelectric can include, but is not limited to, one or more of perovskite type, tungsten bronze type, bismuth layer type, pyrochlore type, niobate type, and lead barium lithium niobate. Optionally, the inorganic ferroelectric can include the perovskite type.

[0140] Optionally, the perovskite type can have the molecular formula Ba 1-x A x Ti 1-y B y O3. A can include, but is not limited to, a combination of one or more of Bi, Pb, Sr, Ca, K, Na, and Cd, and B can include, but is not limited to, a combination of one or more of Fe, Sn, Hf, Zr, Ce, Nb, and Th, where 0 ≤ x ≤ 1 and 0 ≤ y ≤ 1.

[0141] Optionally, the perovskite type can include, but is not limited to, barium titanate (BaTiO3), Ba 1-x1 Sr x1 TiO3 (0 ≤ x1 ≤ 1), SrTiO3, PbTiO3, BiFeO3, PbZr y1 Ti 1-y1 O3 (0 ≤ y1 ≤ 1), BaZr y2 Ti 1-y2 O3 (0 < y2 < 1), or one or more of them.

[0142] Optionally, the tungsten bronze type can have the molecular formula M z WO3. M can include, but is not limited to, one or more of Na, K, Rb, and Cs, where 0 < z < 1.

[0143] Optionally, the tungsten bronze type can include, but is not limited to, Na z1 WO3 (0 < z1 < 1), K z2 WO3 (0 < z2 < 1), or one or more of them.

[0144] Optionally, the bismuth layer type can have the molecular formula (Bi2O2)(C n-1 D n O 3n+1 ). C can include, but is not limited to, one or more of Na, K, Ba, Sr, Pb, Ca, Ln, and Bi, and D can include, but is not limited to, one or more of Zr, Cr, Nb, Ta, Mo, W, Fe, Ti, and V, where 2 ≤ n ≤ 5.

[0145] Optionally, the bismuth layered form may include, but is not limited to, SrBi₂Nb₂O₉, SrBi₂Ta₂O₉, SrBi₂Nb₂O₉, and Bi₄Ti₃O₉. 12 One or more of them.

[0146] Alternatively, the pyrochlore type may include, but is not limited to, one or more of lead metaniobate (PbNb2O6) and Cd2Nb2O7.

[0147] Alternatively, the niobate type may include, but is not limited to, one or more of LiNbO3, KNbO3, and NaNbO3.

[0148] In some embodiments, the thickness of the ferroelectric coating can be 1 μm-3.5 μm, optionally 1.5 μm-3 μm. This allows the battery to possess high reliability, high coulombic efficiency, and good rate performance.

[0149] In some embodiments, the areal density of the ferroelectric coating may be 2.5 g / m³. 2 -15g / m 2 3g / m 2 -12g / m 2 This allows the battery to possess high reliability, high coulombic efficiency, and good rate performance.

[0150] In some embodiments, the ferroelectric coating may also include a dispersant.

[0151] Optionally, the dispersant may include, but is not limited to, one or more of hydrolyzed polymaleic anhydride, polyacrylic acid, acrylic block copolymers, polyester block copolymers, polyethylene glycol-type polyols, polyethyleneimine, and their respective derivatives. Derivatives generally refer to products derived from the substitution of hydrogen atoms or groups of atoms in a polymer by other atoms or groups of atoms.

[0152] Optionally, the ratio of the total weight of the ferroelectric material to the weight of the dispersant can be 1:(0.01-0.02), or optionally 1:(0.010-0.015).

[0153] An appropriate amount of dispersant can make the ferroelectric coating slurry disperse evenly, which is convenient for coating and also helps to increase the film weight of the ferroelectric coating.

[0154] In some embodiments, the ferroelectric coating may also include a thickener.

[0155] Optionally, the thickener may be one or more of sodium carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, polyacrylate, polyurethane, and polyether.

[0156] Optionally, the ratio of the total weight of the ferroelectric material to the weight of the thickener can be 1:(0.01-0.02), or optionally 1:(0.010-0.015).

[0157] An appropriate amount of thickener can improve the stability of the ferroelectric coating slurry, facilitate coating, and also help increase the film weight of the ferroelectric coating.

[0158] A ferroelectric coating 102 is located on at least one surface of the porous substrate 101. In some embodiments, such as Figure 6 As shown, the ferroelectric coating 102 can be located on one of the surfaces of the porous substrate 101; in some embodiments, such as Figure 7 As shown, the ferroelectric coating 102 can also be located on both surfaces of the porous substrate 101.

[0159] In some embodiments, such as Figure 8 As shown, the ferroelectric coating 102 is located on one surface of the porous substrate 101, and a ceramic coating 103 may also be provided on the other surface of the porous substrate 101. When used in a battery, the ferroelectric coating 102 can face the negative electrode, and the ceramic coating 103 can face the positive electrode.

[0160] In some embodiments, the thickness of the porous substrate can be 4μm-15μm, and optionally 5μm-10μm.

[0161] In some embodiments, the porous substrate may include, but is not limited to, one or more of polyolefins (e.g., polyethylene, polypropylene, etc.), halogenated polyolefins (e.g., polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl chloride, etc.), polyamides, polyesters (e.g., polyethylene terephthalate, etc.), and their respective derivatives. Derivatives generally refer to products derived from the substitution of hydrogen atoms or groups of atoms in a polymer by other atoms or groups of atoms.

[0162] [Preparation method of the separating membrane]

[0163] The embodiments of this application also provide a method for preparing an isolation membrane.

[0164] The preparation method includes the following steps: providing a porous substrate; providing a ferroelectric coating slurry: dispersing ferroelectric materials in a solvent to obtain a ferroelectric coating slurry; coating: coating the ferroelectric coating slurry onto at least one surface of the porous substrate, and drying to obtain a release membrane.

[0165] In some embodiments, the drying temperature of the ferroelectric coating slurry can be 60°C-80°C, and the drying time can be 5 min-30 min.

[0166] In some embodiments, the coating method of the ferroelectric coating slurry may include, but is not limited to, gravure transfer coating, rotary spraying, dip coating, and scraping coating.

[0167] In some embodiments, the solvent in the ferroelectric coating slurry may include, but is not limited to, one or more of deionized water, N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), N,N-dimethylacetamide (DMAC), and tetrahydrofuran (THF).

[0168] In some embodiments, the solid content of the ferroelectric coating slurry can be 25%-45%, optionally 30%-40%. This is beneficial for coating.

[0169] In some embodiments, the ferroelectric coating slurry may further include one or more of a dispersant and a thickener.

[0170] In some embodiments, the step of providing a ferroelectric coating slurry may include the following steps: dispersing the ferroelectric material, dispersant and solvent in a primary dispersion to obtain a primary dispersion solution; adding a thickener to the obtained primary dispersion solution for a secondary dispersion to obtain the ferroelectric coating slurry.

[0171] Optionally, the primary dispersion process can be ultrasonic dispersion, during which stirring can be performed. Optionally, the stirring speed during ultrasonic dispersion can be 700 rpm-1200 rpm, and the ultrasonic dispersion time can be 30 min-60 min.

[0172] Optionally, the secondary dispersion process can be ultrasonic dispersion, during which stirring can be performed. Optionally, the stirring speed during ultrasonic dispersion can be 1000 rpm-1600 rpm, and the ultrasonic dispersion time can be 30 min-90 min.

[0173] In some embodiments, the method for preparing the separator membrane may further include the steps of: providing a ferroelectric material: stirring and dispersing a ferroelectric polymer with a first solvent to obtain a clear solution; adding an inorganic ferroelectric to the obtained clear solution and stirring and dispersing it to obtain a slurry; and drying the obtained slurry to obtain the ferroelectric material.

[0174] Optionally, the first solvent may include anhydrous ethanol, N-methylpyrrolidone (NMP), etc.

[0175] Optionally, after the ferroelectric polymer and the first solvent are stirred evenly, ultrasonic dispersion can be performed. The ultrasonic dispersion time can be 20 min to 60 min.

[0176] Optionally, after adding the inorganic ferroelectric to the obtained clear solution and stirring until homogeneous, ultrasonic dispersion can be performed. The ultrasonic dispersion time can be 30-60 minutes.

[0177] Alternatively, the slurry can be dried in a drying oven at a temperature of 75°C to 95°C.

[0178] Optionally, the method for preparing the separator may also include the step of grinding the obtained ferroelectric material.

[0179] In some embodiments, the method for preparing the separator may further include the steps of: preparing a ceramic coating slurry and applying the ceramic coating slurry to the surface of a porous substrate on which no ferroelectric coating is provided.

[0180] The raw materials and their content parameters used in the preparation method of the separator provided in the embodiments of this application can be referred to the separator provided in the embodiments of this application, and will not be repeated here.

[0181] Unless otherwise specified, all raw materials used in the preparation of the separator membrane can be obtained commercially.

[0182] [Positive electrode plate]

[0183] The structure and composition of the positive electrode can be selected according to the type of battery cell, and the embodiments of this application are not limited in this regard.

[0184] In some embodiments, the positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector and comprising a positive electrode active material. For example, the positive current collector has two surfaces opposite each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0185] When the battery is a lithium-ion battery, the positive electrode active material includes materials capable of extracting and inserting lithium. As examples, the positive electrode active material may include, but is not limited to, one or more of lithium transition metal oxides, metal chalcogenides, lithium-containing phosphates, and their respective modified compounds. Examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxides, lithium nickel oxides, lithium manganese oxides, lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, lithium nickel cobalt aluminum oxides, lithium titanium oxides, and their respective modified compounds. Lithium transition metal oxides may include, but are not limited to, layered structures and spinel structures. Examples of lithium-containing phosphates may include, but are not limited to, lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, lithium iron manganese phosphate and carbon composites, and their respective modified compounds.

[0186] In some embodiments, to further improve the energy density of the battery, the positive electrode active material may include materials with the general formula Li. a Ni b Co c M d O e D fOne or more of lithium transition metal oxides and their modified compounds. 0.8≤a≤1.2, 0.5≤b<1, 0<c<1, 0<d<1, 1≤e≤2, 0≤f≤1, M may include, but is not limited to, one or more of Ge, Mo, Sn, Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and D may include, but is not limited to, one or more of N, F, S and Cl.

[0187] In some embodiments, the positive electrode active material may simultaneously comprise lithium transition metal oxide and lithium phosphate. This is advantageous for obtaining a battery that balances high capacity and high reliability.

[0188] As an example, the positive electrode active material may include, but is not limited to, LiCoO2, LiNiO2, LiMnO2, and LiNi 1 / 2 Mn 1 / 2O2, LiMn2O4, Li 4 / 3 Ti 5 / 3 O4, LiNi 1 / 2 Mn 1 / 2 O2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), LiNi 0.85 Co 0.15 Al 0.05 O2, LiFePO4, LiMnPO4, Li 1.13 Ti 0.57 Fe 0.3 One or more of S2.

[0189] When the battery is a sodium battery, the positive electrode active material includes materials capable of extracting and inserting sodium. As an example, the positive electrode active material may include, but is not limited to, one or more of layered transition metal oxides (including but not limited to P2 type, O3 type, etc.), polyanionic materials (such as phosphates, fluorophosphates, pyrophosphates, sulfates, etc.), and Prussian materials.

[0190] In some embodiments, as an example, the positive electrode active material may include, but is not limited to, NaFeO2, NaCoO2, NaCrO2, NaMnO2, NaNiO2, Na0.67 MO2 (M includes at least two of Fe, Co, Cr, Mn, Ni, V, Ti, and Mo), NaMO2 (M includes at least two of Fe, Co, Ni, V, Ti, and Mo), NaFePO4, NaMnPO4, NaCoPO4, Na4Fe3(PO4)2O7, Na3V2(PO4)2F3, Na3V2(PO4)3, Prussian blue, Prussian white, and one or more of their respective modified compounds.

[0191] The modified compounds for the above-mentioned positive electrode active materials can be obtained by doping and / or surface coating of the positive electrode active materials.

[0192] In some embodiments, the positive electrode film may optionally include a positive electrode conductive agent. As an example, the positive electrode conductive agent may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0193] In some embodiments, the positive electrode film layer may optionally include a positive electrode binder. As an example, the positive electrode binder may include, but is not limited to, one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene-propylene terpolymer, ethylene-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resins, styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0194] In some embodiments, the positive current collector may be a metal foil or a composite current collector. An example of a metal foil is aluminum foil. The composite current collector may include a polymeric material substrate and a metal material layer formed on at least one surface of the polymeric material substrate. As an example, the metal material may include, but is not limited to, one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymeric material substrate may include, but is not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0195] The positive electrode film is typically formed by coating a positive electrode slurry onto a positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is usually formed by dispersing positive electrode active materials, optional positive electrode conductive agents, optional positive electrode binders, and any other components in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP), but is not limited to it.

[0196] [Negative electrode plate]

[0197] Each battery cell includes a negative electrode. The structure and composition of the negative electrode can be selected according to the type of battery cell, and the embodiments of this application are not limited in this regard.

[0198] In some embodiments, the negative electrode sheet may include a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector and comprising a negative electrode active material. For example, the negative current collector has two surfaces opposite each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative current collector.

[0199] The negative electrode active material may be any material known in the art. As an example, the negative electrode active material may include, but is not limited to, one or more of carbon-based materials, silicon-based materials, tin-based materials, and lithium titanate. Carbon-based materials may include, but are not limited to, one or more of natural graphite, artificial graphite, soft carbon, hard carbon, pyrolytic carbon, coke, glassy carbon, sintered organic polymers, and mesophase carbon microspheres. Silicon-based materials may include, but are not limited to, one or more of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include, but are not limited to, one or more of elemental tin, tin oxides, and tin alloys.

[0200] In some embodiments, the negative electrode film layer may optionally include a negative electrode conductive agent. As an example, the negative electrode conductive agent may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0201] In some embodiments, the negative electrode film layer may optionally include a negative electrode binder. As an example, the negative electrode binder may include, but is not limited to, one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0202] In some embodiments, the negative electrode film layer may optionally include other additives. As an example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc.

[0203] The negative electrode film is typically formed by coating a negative electrode slurry onto a negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry is usually formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional additives in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0204] The negative electrode sheet does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode sheet may also include a conductive undercoat layer (e.g., composed of a conductive agent and an adhesive) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector; in some embodiments, the negative electrode sheet may also include a protective layer covering the surface of the negative electrode film layer.

[0205] In some embodiments, the negative electrode sheet may include a negative current collector and a metal layer disposed on at least one surface of the negative current collector. The metal material in the metal layer may include, but is not limited to, one or more of elemental lithium, lithium alloy, elemental sodium, and sodium alloy.

[0206] Lithium alloys can be alloys formed from metallic lithium with other metallic or non-metallic elements. For example, other metallic elements in lithium alloys may include, but are not limited to, one or more elements selected from tin, zinc, aluminum, magnesium, silver, gold, gallium, indium, and platinum, while non-metallic elements in lithium alloys may include one or more elements selected from boron, carbon, and silicon.

[0207] Sodium alloys can be alloys formed by metallic sodium with other metallic or non-metallic elements. For example, other metallic elements in sodium alloys may include, but are not limited to, one or more of tin, zinc, aluminum, magnesium, silver, gold, gallium, indium, and platinum, while non-metallic elements in sodium alloys may include one or more of boron, carbon, and silicon.

[0208] In some embodiments, the negative electrode sheet may be a lithium sheet (foil), a lithium alloy sheet (foil), a sodium sheet (foil), or a sodium alloy sheet (foil).

[0209] In some embodiments, the negative electrode may include a negative current collector to assemble a negative electrode-free battery cell.

[0210] In some embodiments, the negative electrode current collector may include, but is not limited to, one or more of the following: metal foil, metal foam current collector, metal mesh current collector, carbon felt current collector, carbon cloth current collector, carbon paper current collector, and composite current collector.

[0211] Examples of metal foil materials include copper foil, copper alloy foil, nickel foil, nickel alloy foil, aluminum foil, and aluminum alloy foil. Examples of metal foam current collectors include copper foam, nickel foam, and aluminum foam. Examples of metal mesh current collectors include copper mesh, nickel mesh, and aluminum mesh.

[0212] The composite current collector may include a polymeric material substrate and a metallic material layer formed on at least one surface of the polymeric material substrate. As an example, the metallic material may include, but is not limited to, one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, aluminum, aluminum alloys, silver, and silver alloys. As an example, the polymeric material substrate may include, but is not limited to, one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0213] [Electrolytes]

[0214] A single battery cell includes an electrolyte. This application does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte may include one or more selected from solid electrolytes and liquid electrolytes (i.e., electrolyte solutions).

[0215] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and an organic solvent.

[0216] Electrolyte salts can include phosphates, perchlorates, organoboronates, fluorine-containing organic salts, imide salts, etc.

[0217] When the battery is a lithium battery, as an example, the electrolyte salt may include, but is not limited to, one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0218] When the battery is a sodium battery, as an example, the electrolyte salt may include, but is not limited to, sodium hexafluorophosphate (NaPF6), sodium tetrafluoroborate (NaBF4), sodium perchlorate (NaClO4), sodium hexafluoroarsenate (NaAsF6), sodium bis(fluorosulfonyl)imide (NaFSI), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), sodium trifluoromethanesulfonate (NaTFS), sodium difluorooxalate borate (NaDFOB), sodium di(oxalate borate) (NaBOB), sodium difluorophosphate (NaPO2F2), sodium di(oxalate phosphate) (NaDFOP), and sodium tetrafluorooxalate phosphate.

[0219] In some embodiments, the concentration of the electrolyte salt may be 0.3 mol / L or higher, optionally 0.7 mol / L or higher, and the concentration of the electrolyte salt may further be 4 mol / L or lower, optionally 2.5 mol / L or lower, or 1.7 mol / L or lower.

[0220] Organic solvents may include, but are not limited to, one or more of esters, ethers, sulfones, and nitriles. Esters may include, but are not limited to, one or more of carbonates, phosphate esters, carboxylic esters, sulfate esters, and sulfonates. Carbonates may include cyclic carbonates and / or chain carbonates. Chain carbonates may include low-viscosity polar chain carbonates, aliphatic branched carbonates, etc.

[0221] As an example, organic solvents may include, but are not limited to, ethylene carbonate (EC), propylene carbonate (PC), butene carbonate, ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), diethyl sulfone (ESE), dimethyl ether tetraethylene glycol (TEGDME), ethylene glycol dimethyl ether (DME), 1,3-dioxolane (DOL), trimethyl phosphate, 3-methoxypropionitrile, H(CF2)2OCH3, C4F9O CH3, H(CF2)2OCH2CH3, H(CF2)2OCH2CF3, H(CF2)2CH2O(CF2)2H, CF3CHFCF2OCH3, CF3CHFCF2OCH2CH3, 2-trifluoromethylhexafluoropropyl methyl ether, 2-trifluoromethylhexafluoropropyl ethyl ether, 2-trifluoromethylhexafluoropropyl propyl ether, 3-trifluoromethyloctafluorobutyl methyl ether, 3-trifluoromethyloctafluorobutyl ethyl ether, 3-trifluoromethyloctafluorobutyl propyl ether, 4-trifluoromethyl One or more of the following: decafluoropentyl methyl ether, 4-trifluoromethyl decafluoropentyl ethyl ether, 4-trifluoromethyl decafluoropentyl propyl ether, 5-trifluoromethyl dodecylfluorohexyl methyl ether, 5-trifluoromethyl dodecylfluorohexyl ethyl ether, 5-trifluoromethyl dodecylfluorohexyl propyl ether, 6-trifluoromethyl tetradecafluoroheptyl methyl ether, 6-trifluoromethyl tetradecafluoroheptyl ethyl ether, 6-trifluoromethyl tetradecafluoroheptyl propyl ether, 7-trifluoromethyl hexadecylfluorooctyl methyl ether, 7-trifluoromethyl hexadecylfluorooctyl ethyl ether, and 7-trifluoromethyl hexadecylfluorooctyl propyl ether.

[0222] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, additives that improve battery low-temperature power performance, etc.

[0223] Methods for preparing battery cells are well known. In some embodiments, a positive electrode, a separator, a negative electrode, and an electrolyte can be assembled to form a battery cell. As an example, the positive electrode, separator, and negative electrode can be formed into an electrode assembly through a winding process and / or a stacking process. The electrode assembly is placed in an outer packaging, dried, and then injected with the aforementioned electrolyte. After vacuum sealing, settling, and formation processes, a battery cell is obtained. Multiple battery cells can further be connected in series, parallel, or a combination thereof to form a battery module. Multiple battery modules can also be connected in series, parallel, or a combination thereof to form a battery pack. In some embodiments, multiple battery cells can also be directly assembled into a battery pack.

[0224] This application also provides an electrical device, which includes the battery provided in this application embodiment. The battery can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device can be, but is not limited to, mobile devices (such as mobile phones, tablets, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0225] Electrical devices can choose the type of battery according to their usage needs, such as individual battery cells, battery modules, or battery packs.

[0226] Figure 9 This is a schematic diagram of an example electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the device's requirements for high power and high energy density, a battery pack or battery module can be used.

[0227] Another example of an electrical device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0228] Example

[0229] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on weight, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0230] Example 1

[0231] Weigh barium titanate (BaTiO3) powder and ferroelectric polymer powder in a weight ratio of 90:10. The barium titanate powder is tetragonal with a volume distribution particle size Dv50 of 0.3 μm and a dielectric constant ε. r The value is 5460. The PVDF is a ferroelectric polymer with a β phase content of 90%, a crystallinity of 65%, and a dielectric constant ε. r It has a strength of 9.6, a melting temperature of 150℃, and a weight-average molecular weight of 540,000.

[0232] Ferroelectric polymer powder was mixed with anhydrous ethanol and stirred until homogeneous. The mixture was then ultrasonically dispersed in an ultrasonic machine for 35-45 minutes to obtain a clear solution. Barium titanate powder was added to the clear solution and stirred until homogeneous. The mixture was then ultrasonically dispersed in an ultrasonic machine for 45-50 minutes to obtain a slurry. The slurry was dried in a drying oven at 90°C. The dried powder was then ground into a fine powder using a mortar and pestle to obtain ferroelectric material powder.

[0233] The obtained ferroelectric material powder was uniformly dispersed in NMP, and hydrolyzed polymaleic anhydride was added for ultrasonic dispersion. After ultrasonic dispersion for 2 hours, sodium carboxymethyl cellulose was added for secondary dispersion to obtain a ferroelectric coating slurry with a solid content of approximately 35%. In the ferroelectric coating slurry, the weight ratio of ferroelectric material, hydrolyzed polymaleic anhydride, and sodium carboxymethyl cellulose was 1:0.01:0.01.

[0234] The obtained ferroelectric coating slurry was coated onto one surface of a porous PE substrate with a porosity of 50% and a thickness of 9 μm using gravure transfer coating. The coating was then vacuum-dried at 60°C to obtain a release film. The ferroelectric coating had a thickness of 3 μm and an areal density of 6 g / m³. 2 .

[0235] Examples 2 to 5

[0236] The preparation method of the separator is similar to that in Example 1, except that the β phase content in the ferroelectric polymer used is different. For specific parameters, please refer to Table 1.

[0237] Comparative Example 1

[0238] Alumina powder and polyacrylic acid were uniformly dispersed in NMP at a weight ratio of 90:10 to obtain a ceramic coating slurry. The obtained ceramic coating slurry was then coated onto one surface of a PE porous substrate with a porosity of 50% and a thickness of 9 μm using gravure transfer coating. The substrate was then vacuum dried at 60°C to obtain a release film. The ceramic coating thickness was 3 μm.

[0239] Comparative Example 2

[0240] The preparation method of the separator is similar to that of Example 1, except that instead of using ferroelectric polymer, α-phase polyvinylidene fluoride is used, wherein the α-phase content is above 75%.

[0241] Comparative Example 3

[0242] The preparation method of the separator is similar to that in Example 1, except that the β phase content in the ferroelectric polymer used is 30%, and the specific parameters are detailed in Table 1.

[0243] Example 6

[0244] The preparation method of the separator is similar to that in Example 1, except that the weight ratio of barium titanate powder to ferroelectric polymer powder is 99.5:0.5.

[0245] Example 7

[0246] The preparation method of the separator is similar to that in Example 1, except that the weight ratio of barium titanate powder to ferroelectric polymer powder is 99:1.

[0247] Example 8

[0248] The preparation method of the separator is similar to that in Example 1, except that the weight ratio of barium titanate powder to ferroelectric polymer powder is 95:5.

[0249] Example 9

[0250] The preparation method of the separator is similar to that in Example 1, except that the weight ratio of barium titanate powder to ferroelectric polymer powder is 85:15.

[0251] Example 10

[0252] The preparation method of the separator is similar to that in Example 1, except that the weight ratio of barium titanate powder to ferroelectric polymer powder is 80:20.

[0253] Example 11

[0254] The preparation method of the separator is similar to that in Example 1, except that the weight ratio of barium titanate powder to ferroelectric polymer powder is 75:25.

[0255] Example 12

[0256] The preparation method of the isolation membrane is similar to that in Example 1, except that the volume distribution particle size Dv50 of the barium titanate powder is 5 μm.

[0257] Example 13

[0258] The preparation method of the isolation membrane is similar to that in Example 1, except that the volume distribution particle size Dv50 of the barium titanate powder is 3 μm.

[0259] Example 14

[0260] The preparation method of the isolation membrane is similar to that in Example 1, except that the volume distribution particle size Dv50 of the barium titanate powder is 1 μm.

[0261] Example 15

[0262] The preparation method of the isolation membrane is similar to that in Example 1, except that the volume distribution particle size Dv50 of the barium titanate powder is 0.5 μm.

[0263] Example 16

[0264] The preparation method of the isolation membrane is similar to that in Example 1, except that the volume distribution particle size Dv50 of the barium titanate powder is 0.1 μm.

[0265] Example 17

[0266] The preparation method of the isolation membrane is similar to that in Example 1, except that the volume distribution particle size Dv50 of the barium titanate powder is 0.05 μm.

[0267] Example 18

[0268] The preparation method of the isolation membrane is similar to that in Example 1, except that the thickness of the ferroelectric coating is 1 μm.

[0269] Example 19

[0270] The preparation method of the isolation membrane is similar to that in Example 1, except that the thickness of the ferroelectric coating is 1.5 μm.

[0271] Example 20

[0272] The preparation method of the isolation membrane is similar to that in Example 1, except that the thickness of the ferroelectric coating is 3.5 μm.

[0273] Examples 21 to 26

[0274] The preparation method of the isolation membrane is similar to that in Example 1, except that the types of inorganic ferroelectrics or ferroelectric polymers in the ferroelectric coating are different. For specific parameters, please refer to Table 2.

[0275] The inorganic ferroelectric and ferroelectric polymer materials used in the above embodiments and comparative examples are all commercially available.

[0276] Performance testing

[0277] (1) Puncture strength test of the isolation membrane

[0278] The puncture strength of the isolation membrane was tested according to GB / T36363-2018.

[0279] Cut the separator membrane into samples 10mm wide and 150mm long, then lay them flat in a fixture and clamp them. Perform a puncture test using a steel needle at a rate of 100mm / min. After the test, remove the sample and perform thickness tests at four points around the needle hole according to GB / T6672-2001. Take the average value and calculate the puncture strength. The diameter of the steel needle can be 1mm, and the radius of the spherical tip can be 0.5mm. The surface of the steel needle should be smooth and free of rust, oxide layer, and oil. More than six separator membrane samples can be tested, and the average value of the test results should be taken.

[0280] (2) Tensile strength test of the separator

[0281] The tensile strength of the separator in the transverse (TD) and longitudinal (MD) directions was tested according to GB / T36363-2018.

[0282] The release liner is cut into samples 10 mm wide and 150 mm long (length direction parallel to the transverse direction of the release liner) for testing to obtain the tensile strength in the transverse (TD) direction. A universal tensile testing machine can be used, with a tensile rate of 50 mm / min. More than six release liner samples can be tested, and the average value of the results is taken.

[0283] The release liner is cut into samples 10 mm wide and 150 mm long (length direction parallel to the longitudinal direction of the release liner) for testing to obtain the tensile strength in the longitudinal (TD) direction. A universal tensile testing machine can be used, with a tensile rate of 50 mm / min. More than six release liner samples can be tested, and the average value of the results is taken.

[0284] (3) Thermal shrinkage rate test of the separator film

[0285] According to GB / T36363-2018, the thermal shrinkage rate of the separator in the transverse (TD) and longitudinal (MD) directions was tested.

[0286] The separator sample was 50 mm wide and 100 mm long. The heat treatment chamber temperature was 105℃ and the heat treatment time was 60 min. After the treatment, the length and width of the separator were measured and the values ​​were marked as a and b, respectively.

[0287] Longitudinal (MD) heat shrinkage rate = [(100-a) / 100] × 100%, Transverse (TD) heat shrinkage rate = [(50-b) / 50] × 100%. During testing, the number of separator samples can be more than 6, and the average value of the test results is taken.

[0288] (4) Air permeability test of the separator membrane

[0289] The air permeability of the separator was tested according to GB / T36363-2018.

[0290] The air permeability of the separator is defined as the time required for 100 mL of air to pass through it. A higher air permeability indicates poorer air permeability. More than six separator samples can be tested, and the average result is taken. A Kumagai KRK air permeability tester can be used.

[0291] (5) Dielectric constant ε of ferroelectric material powder r test

[0292] At 25℃, a suitable amount of ferroelectric material powder was coated with aluminum foil on both sides, placed in a mold, and pressed into a disc using a powder press at a pressure of 2 MPa for 2 minutes. After pressing, the sample disc was removed, and its dielectric constant ε was measured using a precision digital bridge instrument in the frequency range of 20 Hz-2 MHz. r Testing. During testing, the number of samples can be 6 or more, and the average value of the test results is taken.

[0293] Next, the separator was assembled into a button cell and its rate performance was tested.

[0294] Button cells can be prepared according to the following method.

[0295] Lithium iron phosphate, conductive carbon black (Super P), and binder polyvinylidene fluoride (PVDF) were mixed uniformly in an appropriate amount of solvent N-methylpyrrolidone (NMP) at a weight ratio of 8:1:1 to obtain a positive electrode slurry. The positive electrode slurry was coated onto a positive electrode current collector aluminum foil and dried to obtain a positive electrode sheet. In an argon-protected glove box, the positive electrode sheet, separator, and lithium sheet were assembled into a CR2430 coin cell. The electrolyte salt was LiFSI with a concentration of 1 mol / L, and the solvent was ethylene glycol dimethyl ether.

[0296] The ferroelectric coatings of the separators in Examples 1 to 26 and Comparative Examples 1 to 3 are all oriented towards the lithium wafer.

[0297] At 25°C, the coin cell battery was charged at a constant current of 0.1C to 3.65V, and then charged at a constant voltage of 3.65V to 0.05C. After the coin cell battery was left to stand for 10 minutes, it was discharged at a constant current of 0.1C to 2.5V. After cycling the coin cell battery twice according to the above method, the following cycle performance test was performed.

[0298] The coin cell was charged to 3.65V at constant current rates of 0.5C, 1C, and 2C, respectively, and then charged to 0.05C at a constant voltage of 3.65V. After resting for 10 minutes, the coin cell was discharged to 2.5V at a constant current rate of 0.2C. The coin cell was then cycled 100 times using the above method to obtain the charging capacity and discharging capacity of the 100th cycle. The coulombic efficiency of the coin cell after 100 cycles = discharging capacity of the 100th cycle / charging capacity of the 100th cycle.

[0299] During testing, the number of button cell samples can be more than 6, and the average value of the test results is taken.

[0300] The test results are shown in Table 3.

[0301] Table 1

[0302]

[0303] Table 2

[0304]

[0305] Table 3

[0306]

[0307]

[0308] As can be seen from the test results of Examples 1 to 26 and Comparative Examples 1 to 3, by making the ferroelectric coating of the separator include inorganic ferroelectrics and ferroelectric polymers, and the content of β-phase polyvinylidene fluoride in the ferroelectric polymer is greater than or equal to 60%, the coulombic efficiency and rate performance of the battery can be improved without affecting the air permeability, thermal shrinkage rate and mechanical strength of the separator. Figure 10 A scanning electron microscope (SEM) image of the isolation membrane prepared in Example 1 is shown. Figure 10 It can be seen that some ferroelectric polymers are dispersed on the surface of inorganic ferroelectrics.

[0309] The test results from Examples 1 to 5 also show that by further adjusting the content of β-phase polyvinylidene fluoride in the ferroelectric polymer, the dielectric constant ε of the ferroelectric material can be further improved. r This can further improve the air permeability, thermal shrinkage rate and mechanical strength of the separator, and can also further improve the coulombic efficiency and rate performance of the battery.

[0310] The test results from Examples 6 to 11 also show that by further adjusting the weight ratio of inorganic ferroelectric material to ferroelectric polymer, the dielectric constant ε of the ferroelectric material can be further increased. r This can further improve the air permeability, thermal shrinkage rate and mechanical strength of the separator, and can also further improve the coulombic efficiency and rate performance of the battery.

[0311] The test results from Examples 12 to 17 also show that by further adjusting the particle size of the inorganic ferroelectric material, the dielectric constant ε of the ferroelectric material can be further increased. r This can further improve the air permeability, thermal shrinkage rate and mechanical strength of the separator, and can also further improve the coulombic efficiency and rate performance of the battery.

[0312] The test results from Examples 21 to 26 also show that the dielectric constant ε of ferroelectric materials varies depending on the type of inorganic ferroelectric material and / or ferroelectric polymer. r There will be differences, and the effects on improving battery coulombic efficiency and rate performance will also differ.

[0313] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A separating membrane, comprising a porous substrate and a ferroelectric coating on at least one surface of the porous substrate, characterized in that, The ferroelectric coating comprises a ferroelectric material, which includes an inorganic ferroelectric body and a ferroelectric polymer, wherein the dielectric constant ε of the inorganic ferroelectric body is... r The dielectric constant ε of the ferroelectric polymer is greater than that of the ferroelectric polymer. r At least a portion of the ferroelectric polymer is located on at least a portion of the surface of the inorganic ferroelectric material. The ferroelectric polymer includes polyvinylidene fluoride and its copolymers, and the ferroelectric polymer includes β-phase polyvinylidene fluoride, wherein the content of β-phase polyvinylidene fluoride in the ferroelectric polymer is greater than or equal to 60%. Furthermore, the dielectric constant ε of the ferroelectric coating r The dielectric constant ε of the inorganic ferroelectric material is greater than that of the inorganic ferroelectric material. r .

2. The separator membrane according to claim 1, characterized in that, The ferroelectric polymer contains 80% or more of the β-phase polyvinylidene fluoride.

3. The separator membrane according to claim 2, characterized in that, The content of β-phase polyvinylidene fluoride in the ferroelectric polymer is greater than or equal to 90%.

4. The separator according to claim 1, characterized in that, The dielectric constant ε of the ferroelectric coating r With respect to the dielectric constant ε of the inorganic ferroelectric material r The ratio is greater than or equal to 1.

6.

5. The separator according to claim 4, characterized in that, The dielectric constant ε of the ferroelectric coating r With respect to the dielectric constant ε of the inorganic ferroelectric material r The ratio is greater than or equal to 2.

0.

6. The separator according to claim 1, characterized in that, The dielectric constant ε of the inorganic ferroelectric material r For 200-8000; and / or, The dielectric constant ε of the ferroelectric polymer r It ranges from 5 to 100.

7. The separator membrane according to claim 6, characterized in that, The dielectric constant ε of the inorganic ferroelectric material r For 2000-6000; and / or, The dielectric constant ε of the ferroelectric polymer r It ranges from 8 to 70.

8. The separator membrane according to claim 1, characterized in that, The inorganic ferroelectric content in the ferroelectric material is 80%-99% by weight; and / or, The ferroelectric polymer in the ferroelectric material has a weight content of 1%-20%.

9. The separator according to claim 8, characterized in that, The inorganic ferroelectric content in the ferroelectric material is 85%-95% by weight; and / or, The ferroelectric polymer in the ferroelectric material has a weight content of 5%-15%.

10. The separator membrane according to claim 1, characterized in that, The ferroelectric polymer satisfies at least one of the following conditions (1) to (5): (1) The Curie point temperature of the ferroelectric polymer is 150℃-250℃; (2) The remanent polarization of the ferroelectric polymer is 10 mC / m 2 -1000mC / m 2 ; (3) The weight-average molecular weight of the ferroelectric polymer is 200,000 to 800,000; (4) The melting temperature of the ferroelectric polymer is 140℃-220℃; (5) The crystallinity of the ferroelectric polymer is greater than or equal to 45%.

11. The separator membrane according to claim 10, characterized in that, The ferroelectric polymer satisfies at least one of the following conditions (1) to (5): (1) The Curie point temperature of the ferroelectric polymer is 160℃-200℃; (2) The remanent polarization of the ferroelectric polymer is 20 mC / m 2 -800mC / m 2 ; (3) The weight-average molecular weight of the ferroelectric polymer is 400,000 to 650,000; (4) The melting temperature of the ferroelectric polymer is 143℃-200℃; (5) The crystallinity of the ferroelectric polymer is 45%-68%.

12. The separator according to claim 1, characterized in that, The Curie point temperature of the inorganic ferroelectric is 110℃-150℃.

13. The separator membrane according to claim 12, characterized in that, The Curie point temperature of the inorganic ferroelectric is 120℃-140℃.

14. The separator according to claim 1, characterized in that, The ferroelectric polymer includes one or more of polyvinylidene fluoride, copolymers of polyvinylidene fluoride monomer and other monomers.

15. The separator membrane according to claim 14, characterized in that, The other monomers include one or more of trifluoroethylene, trifluorochloroethylene, fluorinated acetylene, and hexafluoropropylene.

16. The separator membrane according to claim 14, characterized in that, The copolymers of the vinylidene fluoride monomer with other monomers include one or more of the following: vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-trifluoroethylene-trifluorochloroethylene copolymer, vinylidene fluoride-trifluoroethylene-trifluorochloroethylene-fluorinated acetylene copolymer, and vinylidene fluoride-hexafluoropropylene copolymer.

17. The separator according to claim 1, characterized in that, The inorganic ferroelectric material includes one or more of the following: perovskite type, tungsten bronze type, bismuth layered type, pyrochlore type, niobate type, and lithium lead barium niobate.

18. The separator membrane according to claim 1, characterized in that, The volumetric particle size distribution Dv50 of the inorganic ferroelectric is 0.05 μm-5 μm; and / or, The volumetric particle size distribution (Dv50) of the ferroelectric polymer is 10 nm to 150 nm.

19. The separator according to claim 18, characterized in that, The volumetric particle size distribution Dv50 of the inorganic ferroelectric is 0.1 μm-1 μm; and / or, The volumetric particle size distribution (Dv50) of the ferroelectric polymer is 15 nm to 50 nm.

20. The separator membrane according to claim 1, characterized in that, The thickness of the ferroelectric coating is 1 μm-3.5 μm; and / or, The areal density of the ferroelectric coating is 2.5 g / m³. 2 -15g / m 2 .

21. The separator according to claim 20, characterized in that, The thickness of the ferroelectric coating is 1.5 μm-3 μm; and / or, The areal density of the ferroelectric coating is 3 g / m³. 2 -12g / m 2 .

22. The separator according to claim 1, characterized in that, The ferroelectric coating also includes a dispersant and / or a thickener.

23. The separator according to claim 22, characterized in that, The dispersant includes one or more of hydrolyzed polymaleic anhydride, polyacrylic acid, acrylic block copolymer, polyester block copolymer, polyethylene glycol polyol, polyethyleneimine, and their respective derivatives.

24. The separator according to claim 22, characterized in that, The ratio of the total weight of the ferroelectric material to the weight of the dispersant is 1:(0.01-0.02).

25. The separator according to claim 24, characterized in that, The ratio of the total weight of the ferroelectric material to the weight of the dispersant is 1:(0.010-0.015).

26. The separator according to claim 22, characterized in that, The thickener includes one or more of sodium hydroxymethylcellulose, methylcellulose, hydroxyethylcellulose, hydroxypropyl methylcellulose, polyacrylate, polyurethane, and polyether.

27. The separator according to claim 22, characterized in that, The ratio of the total weight of the ferroelectric material to the weight of the thickener is 1:(0.01-0.02).

28. The separator according to claim 27, characterized in that, The ratio of the total weight of the ferroelectric material to the weight of the thickener is 1:(0.010-0.015).

29. The separator according to claim 1, characterized in that, The ferroelectric coating is located on one surface of the porous substrate, and a ceramic coating is disposed on the other surface of the porous substrate. When used in a battery, the ferroelectric coating faces the negative electrode, and the ceramic coating faces the positive electrode.

30. The separator according to claim 1, characterized in that, The thickness of the porous substrate is 4μm-15μm; and / or, The porous substrate includes one or more of polyolefins, halogenated polyolefins, polyamides, polyesters, and their respective derivatives.

31. The separator according to claim 30, characterized in that, The thickness of the porous substrate is 5μm-10μm.

32. A single battery cell, characterized in that, Includes the separator membrane according to any one of claims 1-31.

33. A battery, characterized in that, Includes the battery cell as described in claim 32.

34. An electrical appliance, characterized in that, Includes the battery as described in claim 33.

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