Battery cell, battery device, and electric device

Abstract

The application relates to a cyclic phosphazene compound, a separator film and a preparation method, a battery monomer, a battery device and a power utilization device. The battery monomer comprises a separator film, the separator film comprises a polymer base film and a cyclic phosphazene compound, the polymer base film has a porous structure; the cyclic phosphazene compound is dispersed in the polymer base film, the cyclic phosphazene compound comprises a cyclic phosphazene ring group and a functional group connected to the cyclic phosphazene ring group, and the functional group comprises at least one of a fluoroalkyl group and a fluorosilane group. The application can improve the use reliability of the battery monomer.

Description

Technical Field

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

[0002] Battery cells have high capacity and are therefore widely used in electronic devices such as mobile phones, laptops, electric vehicles, electric cars, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes, and power tools.

[0003] However, the reliability of individual battery cells needs further improvement. Summary of the Invention

[0004] This application provides a battery cell, a battery device, and an electrical device. The embodiments of this application can improve the reliability of the battery cell.

[0005] In a first aspect, embodiments of this application provide a battery cell, the battery cell including a separator, the separator including a polymer base film and a cyclophosphonitrile compound, the polymer base film having a porous structure; the cyclophosphonitrile compound is dispersed in the polymer base film, the cyclophosphonitrile compound including cyclophosphonitrile cyclic groups and functional groups attached to the cyclophosphonitrile cyclic groups, the functional groups including at least one of fluoroalkyl and fluorosilyl groups.

[0006] The separator in this application contains cyclophosphonitrile compounds. At high temperatures, these compounds can be released into the electrolyte system, capturing free radicals, blocking thermal runaway reactions, and undergoing endothermic molecular decomposition, which further provides physical cooling and improves the reliability of the battery cell. Since the cyclophosphonitrile compounds are located in the separator, they have virtually no adverse effect on interfacial film formation during the cyclic charging and discharging of the battery cell, and therefore do not significantly degrade the cycle performance of the battery cell.

[0007] In some embodiments, the cyclophosphonitrile compound includes at least one of the compounds shown in Formula I and Formula II. Formula I, Formula II, In formula I, R1, R2, and R3 each independently include a hydrogen atom or a fluorosilyl group; Q1, Q2, and Q3 each independently include a hydrogen atom or a fluoroalkyl group. At least one of R1, R2, R3, Q1, Q2, and Q3 includes a fluorosilyl group or a fluoroalkyl group; In formula II, R4, R5, R6, and R7 each independently include a hydrogen atom or a fluorosilyl group; Q4, Q5, Q6, and Q7 each independently include a hydrogen atom or a fluoroalkyl group. At least one of R4, R5, R6, R7, Q4, Q5, Q6, and Q7 includes a fluorosilyl or fluoroalkyl group.

[0008] The aforementioned materials have good flame retardant properties, which can improve the reliability of battery cells.

[0009] In some embodiments, R1, R2, and R3 each independently comprise a fluorosilyl group. The aforementioned materials exhibit good flame retardancy, thereby improving the reliability of the battery cell.

[0010] In some embodiments, Q1, Q2, and Q3 each independently comprise a fluoroalkyl group. The aforementioned materials exhibit good flame retardancy, thereby improving the reliability of the battery cell.

[0011] In some embodiments, R4, R5, R6, and R7 each independently comprise a fluorosilyl group. The aforementioned materials exhibit good flame retardancy, which improves the reliability of the battery cell.

[0012] In some embodiments, Q4, Q5, Q6, and Q7 each independently comprise a fluoroalkyl group. The aforementioned materials exhibit good flame retardancy, which improves the reliability of the battery cell.

[0013] In some embodiments, the fluoroalkyl group includes C1 to C5 fluoroalkyl groups, optionally C2 to C4 fluoroalkyl groups. The above-mentioned material exhibits good flame retardant properties, which can improve the reliability of the battery cell.

[0014] In some embodiments, the cyclophosphonitrile compounds include at least one of the compounds shown in Formula I-1 to Formula I-3. The aforementioned materials have good flame retardant properties, which can improve the reliability of battery cells.

[0015] In some embodiments, the cyclophosphonitrile compound includes at least one of the compounds shown in Formula II-1 to Formula II-3. The aforementioned materials have good flame retardant properties, which can improve the reliability of battery cells.

[0016] In some embodiments, the mass content of cyclophosphonitrile compounds in the separator is 1% to 10%, optionally 2% to 5%. When the mass content of cyclophosphonitrile compounds in the separator meets the above conditions, when the internal temperature of the battery cell rises, the cyclophosphonitrile compounds are released from the separator into the electrolyte, which can quickly interrupt the reaction chain and improve the reliability of the battery cell.

[0017] In some embodiments, the longitudinal thermal shrinkage rate of the separator after heat treatment at 45°C for 2 hours is 1.5% to 5.0%. When the longitudinal thermal shrinkage rate of the separator is within the above range, the mechanical properties of the separator are stable during battery cell cycling, which can improve the cycle performance of the battery cells.

[0018] In some embodiments, the lateral thermal shrinkage rate of the separator after heat treatment at 45°C for 2 hours is 1.0% to 4.0%. When the longitudinal thermal shrinkage rate of the separator is within the above range, the mechanical properties of the separator are stable during battery cell cycling, which can improve the cycle performance of the battery cells.

[0019] In some embodiments, the elongation of the separator is 10% to 20%. When the elongation of the separator is within this range, the separator exhibits excellent flexibility and ductility, maintains structural stability during cycling, and is less prone to structural fracture during thermal runaway. In some embodiments, the polymer base film includes at least one of polyolefin, polyamide, polyimide, and polyethylene terephthalate. These materials exhibit excellent thermal stability and stability during the cyclic charge-discharge process of the battery cell. Furthermore, they facilitate the uniform dispersion of cyclophosphonitrile compounds within the polymer base film, enabling the rapid release of cyclophosphonitrile compounds when the battery cell experiences a temperature rise, thereby interrupting the reaction chain and improving the reliability of the battery cell.

[0020] In some embodiments, the polyolefin includes at least one of polyethylene, polypropylene, and polyvinylidene fluoride.

[0021] In some embodiments, the polyamide includes at least one of poly(m-phenylene isophthalamide) (or meta-aramid) and polycaprolactam.

[0022] Secondly, this application proposes a battery device comprising a battery cell as described in any embodiment of the first aspect of this application.

[0023] Thirdly, this application proposes an electrical device including a battery device as described in any embodiment of the second aspect.

[0024] Fourthly, this application proposes a separator membrane comprising a polymer base membrane and a cyclophosphonitrile compound. The polymer base membrane has a porous structure. The cyclophosphonitrile compound is dispersed in the polymer base membrane and includes cyclophosphonitrile cyclic groups and functional groups attached to the cyclophosphonitrile cyclic groups. The functional groups include at least one of fluoroalkyl and fluorosilyl groups. The above-mentioned separator membrane exhibits excellent flame retardant properties, which, when applied to battery cells, helps improve the reliability of the battery cells.

[0025] Fifthly, this application proposes a cyclophosphonitrile compound, which includes a cyclophosphonitrile cyclic group and a functional group attached to the cyclophosphonitrile cyclic group, wherein the functional group includes at least one of fluoroalkyl and fluorosilyl groups. The above-mentioned material exhibits excellent flame retardant properties, which, when applied to battery cells, helps improve the reliability of the battery cells.

[0026] Sixthly, this application proposes a method for preparing a separating membrane, comprising: The organic polymer and functional material are mixed. The functional material includes a cyclophosphonitrile compound, which includes a cyclophosphonitrile cyclic group and a functional group attached to the cyclophosphonitrile cyclic group. The functional group includes at least one of fluoroalkyl and fluorosilyl groups. Heat-treating organic polymers causes them to melt, and functional materials are dispersed within the organic polymers to form heat-treated structures. The structure is subjected to pressure treatment and heat treatment to form an isolation membrane.

[0027] The separator prepared according to the embodiments of this application has excellent flame retardant effect, which is beneficial to improving the reliability of battery cells when applied to them. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some implementation methods of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0029] Figure 1 A schematic diagram of the vehicle structure provided for some embodiments of this application.

[0030] Figure 2 This is an exploded schematic diagram of a battery pack provided for some embodiments of this application.

[0031] Figure 3 for Figure 2 The diagram shows the structure of the battery module.

[0032] Figure 4 This is a schematic diagram of the structure of a battery cell provided for some embodiments of this application.

[0033] Figure 5 This is an exploded schematic diagram of a battery cell provided for some embodiments of this application.

[0034] The accompanying drawings may not be drawn to scale.

[0035] The annotations in the attached figures are explained as follows: 1. Vehicle, 2. Battery pack, 3. Controller, 4. Motor, 5. Housing, 5a. First housing section, 5b. Second housing section, 5c. Housing space, 6. Battery module, 7. Battery cell, 10. Electrode assembly, 20. Housing assembly. Detailed Implementation

[0036] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the dispersant, positive electrode slurry, positive electrode sheet, battery, and power 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 to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0037] 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.

[0038] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0039] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0040] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means 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.

[0041] A single battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode, a negative electrode, and a separator. The separator is located between the positive and negative electrode to isolate them.

[0042] Electrolytes contain organic solvents, which are flammable under overheating conditions, causing reliability issues for individual battery cells. In related technologies, flame retardants are added to the electrolyte to inhibit combustion and improve the reliability of the battery cells. However, flame retardants may affect the solvation structure and interfacial film formation, thereby deteriorating the cycle performance of the battery cells.

[0043] In view of this, the present application provides a battery cell including a separator containing a cyclophosphonitrile compound. At high temperatures, the cyclophosphonitrile compound can be released into the electrolyte system, which can capture combustion oxidation free radicals, block thermal runaway reactions, and the molecular decomposition endothermics, which can further play a role in physical cooling and improve the reliability of the battery cell. Since the cyclophosphonitrile compound is located in the separator, during the cyclic charging and discharging process of the battery cell, the cyclophosphonitrile compound will not have an adverse effect on the interfacial film formation and will not have a deterioration on the cycle performance of the battery cell.

[0044] The battery cells described in this application are applicable to battery devices and electrical devices that use battery devices.

[0045] Electrical devices can include vehicles, mobile phones, portable devices, laptops, ships, spacecraft, electric toys, and power tools, etc. Vehicles can be gasoline-powered cars, natural gas-powered cars, or new energy vehicles; new energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. The embodiments of this application do not impose special limitations on the above-mentioned electrical devices.

[0046] For ease of explanation, the following implementation method uses a vehicle as an example of an electrical device.

[0047] Figure 1 A schematic diagram of the vehicle structure provided for some embodiments of this application.

[0048] like Figure 1 As shown, a battery pack 2 is installed inside the vehicle 1. The battery pack 2 can be located at the bottom, front, or rear of the vehicle 1. The battery pack 2 can be used to power the vehicle 1; for example, the battery pack 2 can serve as the operating power source for the vehicle 1.

[0049] Vehicle 1 may also include controller 3 and motor 4. Controller 3 is used to control battery pack 2 to supply power to motor 4, for example, for the power needs of vehicle 1 during start-up, navigation and driving.

[0050] In some embodiments of this application, the battery pack 2 can not only serve as the operating power source for the vehicle 1, but also as the driving power source for the vehicle 1, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1.

[0051] Figure 2 This is an exploded view of a battery pack provided for some embodiments of this application. For example... Figure 2 As shown, the battery pack 2 includes a housing 5 and individual battery cells 7. Figure 2 (Not shown), the battery cell 7 is housed inside the casing 5.

[0052] The housing 5 is used to house the battery cell 7, and the housing 5 can have various structures. In some embodiments, the housing 5 may include a first housing portion 5a and a second housing portion 5b, which overlap each other, and together define a housing space 5c for housing the battery cell 7. The second housing portion 5b may be a hollow structure with one end open, and the first housing portion 5a may be a plate-like structure, with the first housing portion 5a covering the open side of the second housing portion 5b to form a housing 5 with the housing space 5c; alternatively, both the first housing portion 5a and the second housing portion 5b may be hollow structures with one side open, with the open side of the first housing portion 5a covering the open side of the second housing portion 5b to form a housing 5 with the housing space 5c. Of course, the first housing portion 5a and the second housing portion 5b can be various shapes, such as cylinders, cuboids, etc.

[0053] To improve the sealing performance after the first housing part 5a and the second housing part 5b are connected, a sealing element, such as sealant or sealing ring, can also be provided between the first housing part 5a and the second housing part 5b.

[0054] Assuming that the first box section 5a covers the top of the second box section 5b, the first box section 5a can also be called the upper box cover, and the second box section 5b can also be called the lower box.

[0055] In battery pack 2, there can be one or more battery cells 7. If there are multiple battery cells 7, they can be connected in series, parallel, or in a mixed manner. A mixed connection means that multiple battery cells 7 are connected in both series and parallel. Multiple battery cells 7 can be directly connected in series, parallel, or in a mixed manner, and then the whole assembly of multiple battery cells 7 is housed in the housing 5. Alternatively, multiple battery cells 7 can first be connected in series, parallel, or in a mixed manner to form battery modules 6, and then multiple battery modules 6 can be connected in series, parallel, or in a mixed manner to form a whole assembly, which is then housed in the housing 5 to form a battery device.

[0056] The battery cell 7 can be the smallest unit that makes up the battery device.

[0057] Figure 3 for Figure 2 The diagram shows the structure of the battery module.

[0058] In some implementations, such as Figure 3 As shown, there are multiple battery cells 7, which are first connected in series, parallel, or a combination of both to form a battery module 6. These battery modules 6 are then connected in series, parallel, or a combination of both to form a whole, which is housed within the casing.

[0059] Multiple battery cells 7 in battery module 6 can be electrically connected through a busbar to achieve parallel, series, or mixed connection of multiple battery cells 7 in battery module 6. There can be one or more busbars, each used to electrically connect at least two battery cells 7.

[0060] Figure 4 This is a schematic diagram of the structure of a battery cell 7 provided in some embodiments of this application; Figure 5 This is an exploded schematic diagram of a battery cell provided for some embodiments of this application.

[0061] like Figure 4 and Figure 5 As shown, in some embodiments, the battery cell 7 includes an electrode assembly 10 and a housing 20, with the electrode assembly 10 housed within the housing 20.

[0062] The internal cavity formed by the outer casing 20 can be used to accommodate the electrode assembly 10, the electrolyte, and other components. The outer casing 20 can be of various shapes, such as a cylinder or a cuboid. The shape of the outer casing 20 can be determined according to the specific shape of the electrode assembly 10. For example, if the electrode assembly 10 has a cylindrical structure, the outer casing 20 can be a cylindrical structure. If the electrode assembly 10 has a cuboid structure, the outer casing 20 can be a cuboid structure.

[0063] The outer shell 20 can be made of various materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, etc. This application does not impose any special restrictions on this.

[0064] The electrode assembly 10 housed within the housing 20 may be one or more. In this embodiment, the electrode assembly 10 may be a wound structure or a stacked structure, and may be a stacked structure.

[0065] The electrode assembly 10 includes a positive electrode and a negative electrode. During the charging and discharging process of the battery cell 7, active ions (such as lithium ions) repeatedly insert and extract between the positive and negative electrodes. Optionally, the electrode assembly 10 also includes a separator disposed between the positive and negative electrodes, which can reduce the risk of short circuit between the positive and negative electrodes while allowing active ions to pass through.

[0066] In some embodiments, the positive electrode can be a positive electrode sheet, which can include a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including a positive electrode active material.

[0067] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0068] As an example, the positive electrode current collector can be a metal foil or a composite current collector. For example, as a metal foil, stainless steel, copper, aluminum, nickel, carbon electrodes, carbon, nickel, titanium, silver-surfaced aluminum, or stainless steel can be used. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0069] As an example, when the battery cell 7 in this embodiment is a lithium-ion battery or a lithium metal battery, the positive electrode active material may include one or more of the following materials: phosphates, layered transition metal oxides, and their respective modified compounds; optionally, the positive electrode active material may include layered transition metal oxides and their respective modified compounds, which is beneficial to improving the energy density of the battery cell 7. However, this application is not limited to these materials, and other conventional materials that can be used as the positive electrode film layer of a battery may also be used. These positive electrode active materials may be used alone or in combination of two or more.

[0070] Examples of phosphates may include, but are not limited to, one or more of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0071] Layered transition metal oxides include those with the general formula Li a Ni b Co c M d O e A f One or more of the compounds and their modified compounds. 0.8≤a≤1.2, 0.3≤b<1, 0<c<1, 0<d<1, 1≤e≤2, 0≤f≤1, M includes one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and A includes one or more of N, F, S and Cl.

[0072] Examples of layered transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.80 Co 0.15 Al 0.05 One or more of O2 and its modified compounds.

[0073] When the battery cell 7 in the embodiments of this application is a sodium-ion battery or a sodium metal battery, the positive electrode active material may include, but is not limited to, one or more of sodium-containing transition metal oxides, polyanionic materials (such as phosphates, fluorophosphates, pyrophosphates, sulfates, etc.), and Prussian blue materials.

[0074] As an example, positive electrode active materials for sodium-ion batteries may include NaFeO2, NaCoO2, NaCrO2, NaMnO2, NaNiO2, and NaNi 1 / 2 Ti 1 / 2 O2, NaNi 1 / 2 Mn 1 / 2 O2, Na 2 / 3 Fe 1 / 3 Mn 2 / 3 O2, NaNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, NaFePO4, NaMnPO4, NaCoPO4, Prussian blue materials, with the general formula X p M' q (PO4) r O x Y 3-x One or more of the materials. In general formula X p M' q (PO4) r O x Y 3-x In the given condition, 0 < p ≤ 4, 0 < q ≤ 2, 1 ≤ r ≤ 3, 0 ≤ x ≤ 2, and X includes H. + Li + Na + K + and NH4 + One or more of the following, M' is a transition metal cation, optionally one or more of V, Ti, Mn, Fe, Co, Ni, Cu and Zn, and Y is a halide anion, optionally one or more of F, Cl and Br.

[0075] In the embodiments of this application, the modified compounds of the above-mentioned positive electrode active materials can be doped and / or surface coated to modify the positive electrode active materials, such as carbon coating modification, fast ion conductor coating modification, etc.

[0076] During the charging and discharging process, the battery cell 7 undergoes the insertion and extraction of active ions such as Li, resulting in a different molar content of Li in the battery cell 7 at different discharge states. In the examples of positive electrode active materials in this application, the molar content of Li refers to the initial state of the material, i.e., the state before feeding. When the positive electrode active material is applied to the battery system, the molar content of Li may change after charge-discharge cycles.

[0077] In the embodiments of this application, the molar content of oxygen (O) in the positive electrode active materials is only a theoretical value. Oxygen release from the crystal lattice will cause the molar content of oxygen (O) to change. In reality, the molar content of oxygen (O) will fluctuate.

[0078] In some embodiments, the positive electrode can be a foamed metal. The foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloy, or foamed carbon, etc. When foamed metal is used as the positive electrode, a positive electrode film layer may or may not be provided on the surface of the foamed metal. As an example, lithium source material, potassium metal, or sodium metal may also be filled and / or deposited within the foamed metal, where the lithium source material is lithium metal and / or a lithium-rich material.

[0079] In some embodiments, the positive electrode film layer may optionally include a positive electrode conductive agent. This application does not impose particular limitations on the type of positive electrode conductive agent. As an example, the positive electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage of the positive electrode conductive agent in the positive electrode film layer is ≤5 wt%.

[0080] In some embodiments, the positive electrode film layer may optionally include a positive electrode binder. This application does not impose particular limitations on the type of positive electrode binder. As an example, the positive electrode binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene-propylene terpolymer, ethylene-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins. In some embodiments, the mass percentage of the positive electrode binder in the positive electrode film layer is ≤5 wt%.

[0081] 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 the positive electrode active material, optional conductive agent, optional binder, and any other components in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP), but is not limited to this.

[0082] In some embodiments, the battery cell 7 is an ion-type battery, such as a lithium-ion battery, or a metal-type battery, such as a lithium metal battery.

[0083] In some implementations, the negative electrode can be a negative electrode sheet, which may include a negative current collector.

[0084] As an example, the negative electrode current collector may include a metal foil, a foamed metal, or a composite current collector. For example, as a metal foil, it may be aluminum or stainless steel with a silver surface treatment, stainless steel, copper, aluminum, nickel, carbon electrode, carbon, nickel, or titanium, etc. The foamed metal may be foamed nickel, foamed copper, foamed aluminum, foamed alloy, or foamed carbon, etc. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0085] Optionally, the negative electrode current collector may also include a lithium layer, for example, the lithium layer is disposed on at least one side of the metal foil.

[0086] Optionally, the negative electrode sheet may further include a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the negative electrode film layer comprising a negative electrode active material.

[0087] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0088] As an example, the negative electrode active material may be a negative electrode active material known in the art for use in battery cell 7. As an example, the negative electrode active material may include one or more of the following materials: carbon materials (e.g., carbon materials include one or more of artificial graphite, natural graphite, soft carbon, and hard carbon), silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may include one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as battery negative electrode films may also be used. These negative electrode films may be used alone or in combination of two or more.

[0089] In some embodiments, the negative electrode film layer may optionally include a negative electrode conductive agent. This application does not impose particular limitations on the type of negative electrode conductive agent. As an example, the negative electrode conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon fibers. In some embodiments, the mass percentage of the negative electrode conductive agent in the negative electrode film layer is ≤5 wt%.

[0090] In some embodiments, the negative electrode film layer may optionally include a negative electrode binder. This application does not impose particular limitations on the type of negative electrode binder. As an example, the negative electrode binder may include one or more of the following: 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). In some embodiments, the mass percentage of the negative electrode binder in the negative electrode film layer is ≤5 wt%.

[0091] In some embodiments, the negative electrode film may optionally include other additives. As an example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc. In some embodiments, the mass percentage of other additives in the negative electrode film is ≤2 wt%.

[0092] In some embodiments, the battery cell 7 also includes an electrolyte. During the charging and discharging process of the battery cell 7, active ions repeatedly insert and extract between the positive and negative electrode plates, and the electrolyte acts as a conductor for these active ions between the positive and negative electrode plates. The embodiments of this application do not impose any particular limitation on the type of electrolyte, and it can be selected according to actual needs.

[0093] This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. The electrolyte can be liquid, gel, or solid.

[0094] Liquid electrolytes include electrolyte salts and solvents.

[0095] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0096] In some embodiments, the solvent may be selected from at least one of 1,2-dimethoxyethane, ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone. The solvent may also be an ether solvent. Ether solvents may include one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyl tetrahydrofuran, diphenyl ether, and crown ethers.

[0097] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain properties of the battery cell, such as additives that improve the overcharge / fast charge performance of the battery cell, additives that improve the high-temperature performance of the battery cell, and additives that improve the low-temperature performance of the battery cell.

[0098] The gel electrolyte includes a polymer as a backbone network and can be used in conjunction with an ionic liquid-lithium salt.

[0099] Solid electrolytes include polymer solid electrolytes, inorganic solid electrolytes, and composite solid electrolytes.

[0100] As an example, the polymers of polymeric solid electrolytes may include polyethers (polyoxyethylene), polysiloxanes, polycarbonates, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, monoionic polymers, polyionic liquids, cellulose, etc.

[0101] As an example, inorganic solid electrolytes can be one or more of the following: oxide solid electrolytes (crystalline perovskite, sodium superconducting ion conductors, garnet, amorphous LiPON thin films), sulfide solid electrolytes (crystalline lithium superconducting ion conductors (lithium-germanium-phosphorus-sulfur, sulfosilium-germanium), amorphous sulfides), halide solid electrolytes, nitride solid electrolytes, and hydride solid electrolytes.

[0102] As an example, composite solid electrolytes are formed by adding inorganic solid electrolyte fillers to polymer solid electrolytes.

[0103] In some embodiments, the separator comprises a polymer base membrane and a cyclophosphonitrile compound, the polymer base membrane having a porous structure; the cyclophosphonitrile compound is dispersed in the polymer base membrane, the cyclophosphonitrile compound comprising cyclophosphonitrile cyclic groups and functional groups attached to the cyclophosphonitrile cyclic groups, the functional groups comprising at least one of fluoroalkyl and fluorosilyl groups.

[0104] When a battery cell experiences a short circuit, the temperature within the system rises, which may cause the electrolyte, the solid electrolyte interphase (SEI) membrane, and the positive electrode active material to decompose, generating heat and free radicals. These free radicals can react with other substances inside the battery cell, exacerbating the reaction.

[0105] The separator in this application contains cyclophosphonitrile compounds. At high temperatures, these compounds can be released into the electrolyte system, capturing free radicals, blocking thermal runaway reactions, and undergoing endothermic molecular decomposition, which further provides physical cooling and improves the reliability of the battery cell. Since the cyclophosphonitrile compounds are located in the separator, they have virtually no adverse effect on interfacial film formation during the cyclic charging and discharging of the battery cell, and therefore do not significantly degrade the cycle performance of the battery cell.

[0106] Cyclophosphazene ring structures can be either a type of ring structure formed by alternating phosphorus and nitrogen atoms (referred to as the first type of ring structure), or a type of ring structure formed by connecting the first type of ring structure with oxygen atoms (referred to as the second type of ring structure).

[0107] The functional group is mainly connected to the phosphorus atom of the cyclic phosphazene group, which can be understood as the functional group replacing the hydrogen atom that was originally connected to the phosphorus atom.

[0108] Cyclophosphazene compounds include cyclic phosphazene groups. These cyclic phosphazene groups, as the skeleton of cyclophosphazene, can capture oxidative free radicals. When decomposed by heat, they can isolate air and prevent combustion, thus blocking the combustion reaction chain. The functional groups of cyclophosphonitrile compounds include at least one of fluoroalkyl and fluorosilyl groups, which can block combustion and further interrupt the chemical reaction chain.

[0109] Elements such as phosphorus, fluorine, and silicon have a synergistic flame-retardant effect, which can improve the flame-retardant properties of materials and reduce their dosage. For example, when phosphorus burns, it releases acidic gases, which can combine with silicon to form silicates, thereby further promoting the formation of phosphoric acid compounds, forming a more complete protective film, and improving the flame-retardant performance of the material.

[0110] In some embodiments, the cyclophosphonitrile compounds include those represented by Formula I. Formula I, In formula I, R1, R2, and R3 each independently include a hydrogen atom or a fluorosilyl group; Q1, Q2, and Q3 each independently include a hydrogen atom or a fluoroalkyl group. Among them, R1, R2, R3, Q1, Q2, and Q3 do not all contain hydrogen atoms.

[0111] The cyclic groups in Formula I are examples of cyclic phosphazene groups.

[0112] R1, R2, R3, Q1, Q2, and Q3 do not all simultaneously include hydrogen atoms. This can be understood as at least one of R1, R2, R3, Q1, Q2, and Q3 including a fluorosilyl or fluoroalkyl group. For example, if at least one of R1, R2, and R3 includes a fluorosilyl group, then Q1, Q2, and Q3 each independently include either a hydrogen atom or a fluoroalkyl group. Another example is that if at least one of Q1, Q2, and Q3 includes a fluoroalkyl group, then R1, R2, and R3 each independently include either a hydrogen atom or a fluorosilyl group.

[0113] Optionally, the fluorosilyl group can be trifluorosilyl, which increases the number of fluorine atoms, further enhancing the flame retardant effect and improving the reliability of the battery cell.

[0114] Optionally, the fluoroalkyl group includes C1 to C5 fluoroalkyl groups. For example, fluoroalkyl groups may include fluoromethyl, fluoroethyl, fluoropropyl, fluorobutyl, or fluoropentyl. An increase in the number of carbon atoms results in a higher relative molecular mass and a higher boiling point for cyclophosphonitrile compounds. During normal charge-discharge cycles of a battery cell, cyclophosphonitrile compounds exhibit greater stability and are less likely to be released from the separator, thus having minimal adverse impact on cycle performance. However, an excessively large number of carbon atoms increases the difficulty of releasing cyclophosphonitrile compounds during thermal runaway, potentially delaying the flame-retardant effect. Therefore, optionally, the fluoroalkyl group includes C2 to C4 fluoroalkyl groups.

[0115] Optionally, the fluoroalkyl group can be a perfluoroalkyl group, which increases the number of fluorine atoms, further enhancing the flame retardant effect and improving the reliability of the battery cell.

[0116] For example, cyclophosphonitrile compounds include at least one of the compounds shown in Formula I-1 to Formula I-3. In some embodiments, the cyclophosphonitrile compounds include those represented by Formula II. Formula II, In formula II, R4, R5, R6, and R7 each independently include a hydrogen atom or a fluorosilyl group; Q4, Q5, Q6, and Q7 each independently include a hydrogen atom or a fluoroalkyl group. R4, R5, R6, R7, Q4, Q5, Q6, and Q7 do not all contain hydrogen atoms.

[0117] The cyclic group in Formula II is an example of a cyclic phosphazene group.

[0118] R4, R5, R6, R7, Q4, Q5, Q6, and Q7 do not all simultaneously include hydrogen atoms. This can be understood as at least one of R4, R5, R6, R7, Q4, Q5, Q6, and Q7 including a fluorosilyl or fluoroalkyl group. For example, if at least one of R4, R5, R6, and R7 includes a fluorosilyl group, then Q4, Q5, Q6, and Q7 each independently include a hydrogen atom or a fluoroalkyl group. Another example is that if at least one of Q4, Q5, Q6, and Q7 includes a fluoroalkyl group, then R4, R5, R6, and R7 each independently include a hydrogen atom or a fluorosilyl group.

[0119] Optionally, the fluorosilyl group can be trifluorosilyl, which increases the number of fluorine atoms, further enhancing the flame retardant effect and improving the reliability of the battery cell.

[0120] Optionally, the fluoroalkyl group includes C1 to C5 fluoroalkyl groups. For example, fluoroalkyl groups may include fluoromethyl, fluoroethyl, fluoropropyl, fluorobutyl, or fluoropentyl. An increase in the number of carbon atoms results in a higher relative molecular mass and a higher boiling point for cyclophosphonitrile compounds. During normal charge-discharge cycles of a battery cell, cyclophosphonitrile compounds exhibit greater stability and are less likely to be released from the separator, thus having minimal adverse impact on cycle performance. However, an excessively large number of carbon atoms increases the difficulty of releasing cyclophosphonitrile compounds during thermal runaway, potentially delaying the flame-retardant effect. Therefore, optionally, the fluoroalkyl group includes C2 to C4 fluoroalkyl groups.

[0121] Optionally, the fluoroalkyl group can be a perfluoroalkyl group, which increases the number of fluorine atoms, further enhancing the flame retardant effect and improving the reliability of the battery cell.

[0122] By way of example, cyclophosphonitrile compounds include at least one of the compounds shown in Formula II-1 to Formula II-3. In some embodiments, the cyclophosphonitrile compound in the separator membrane is 1% to 10% by mass, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%. Optionally, the cyclophosphonitrile compound in the separator membrane is 2% to 5% by mass.

[0123] When the mass content of cyclophosphonitrile compounds in the separator meets the above conditions, the cyclophosphonitrile compounds are released from the separator into the electrolyte when the internal temperature of the battery cell rises. This can quickly block the reaction chain and improve the reliability of the battery cell.

[0124] In some embodiments, the longitudinal thermal shrinkage rate of the separator after heat treatment at 45°C for 2 hours is 1.5% to 5.0%.

[0125] For example, the longitudinal heat shrinkage rate of the separator after heat treatment at 45°C for 2 hours is 1.5%, 2.0%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5.0%, or any combination of two of the above values.

[0126] When the longitudinal thermal shrinkage rate of the separator is within the above range, the separator shrinks less at 45°C. During the cycle of the battery cell, the mechanical properties of the separator are stable, which can improve the cycle performance of the battery cell.

[0127] In some embodiments, the transverse thermal shrinkage rate of the separator after heat treatment at 45°C for 2 hours is 1.0% to 4.0%.

[0128] For example, the transverse heat shrinkage rate of the separator after heat treatment at 45°C for 2 hours is 1.0%, 1.5%, 2.0%, 2.5%, 3%, 3.5%, 4.0%, or any range of two of the above values.

[0129] When the longitudinal thermal shrinkage rate of the separator is within the above range, the separator shrinks less at 45°C. During the cycle of the battery cell, the mechanical properties of the separator are stable, which can improve the cycle performance of the battery cell.

[0130] In some embodiments, the elongation of the separator is 10% to 20%, for example 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, or any combination of two of the above values.

[0131] When the elongation of the separator is within the above range, the separator exhibits excellent flexibility and ductility, maintains structural stability during cycling, and is less prone to structural breakage during thermal runaway.

[0132] In the embodiments of this application, the heat shrinkage rate and elongation rate of the separator are known in the art and can be tested using equipment and methods known in the art, such as according to the standard GB / T 36363-2018 Polyolefin separator for lithium-ion batteries.

[0133] In some embodiments, the average pore size of the porous structure is from 0.1 μm to 1 μm, for example, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm or any combination of two of the above values.

[0134] When the average pore size of the porous structure is within the above range, it is beneficial for the release of lithium ions in the battery cells during cyclic charging and discharging, and it also prevents the impedance of the separator from being too high.

[0135] When the average pore size of the porous structure is within the aforementioned range, cyclophosphonitrile compounds can be released from the pore structure at high temperatures. This facilitates the rapid release of large amounts of cyclophosphonitrile compounds under short-circuit conditions, interrupting the reaction chain and improving the reliability of the battery cell. Furthermore, an average pore size within this range promotes lithium-ion migration, improving the cycle performance of the battery cell and preventing excessively high impedance in the separator.

[0136] In some embodiments, the polymer base film includes at least one of polyolefin, polyamide, polyimide, and polyethylene terephthalate. These materials exhibit excellent thermal stability and stability during the cyclic charge-discharge process of the battery cell. Furthermore, they facilitate the uniform dispersion of cyclophosphonitrile compounds within the polymer base film, enabling the rapid release of cyclophosphonitrile compounds when the battery cell experiences a temperature rise, thereby interrupting the reaction chain and improving the reliability of the battery cell.

[0137] Optionally, the weight-average molecular weight of the polymer base film can be between 1 million and 1.6 million. When the weight-average molecular weight of the polymer base film is within the above range, it is beneficial to improve the thermal stability and mechanical properties of the polymer base film.

[0138] For example, the polyolefin includes at least one of polyethylene, polypropylene and polyvinylidene fluoride.

[0139] For example, the polyamide includes at least one of poly(m-phenylene isophthalamide) (or meta-aramid) and polycaprolactam.

[0140] This application also provides a method for preparing a separating membrane, comprising: Step S100: Mix the organic polymer and the functional material, the functional material including cyclophosphonitrile compounds; Step S200: Heat-treat the organic polymer to make the organic polymer melt, and disperse the functional material in the organic polymer to form a heat-treated structure; Step S300: Apply pressure to heat-treated structure to form an isolation membrane.

[0141] The preparation method provided in this application involves a molten organic polymer that is fluid, allowing it to flow to the cyclophosphonitrile compound and disperse the compound within it. The molten organic polymer is then pressurized to form a polymer-based film, further dispersing the cyclophosphonitrile compound within the film and forming a separator. In the event of a short circuit in a battery cell, the system temperature rises, allowing the cyclophosphonitrile compound to be released into the electrolyte, thus blocking the reaction chain and improving the reliability of the battery cell.

[0142] Step S100 is a mixing step, in which the components are mixed evenly to prepare for subsequent steps.

[0143] In some embodiments, the organic polymer includes at least one of polyolefins, polyamides, polyimides, and polyethylene terephthalate. This material facilitates the uniform dispersion of cyclophosphonitrile compounds within the polymer base film, enabling the rapid release of cyclophosphonitrile compounds when the battery cell experiences temperature increases, thereby interrupting the reaction chain and improving the reliability of the battery cell.

[0144] For example, the polyolefin includes at least one of polyethylene, polypropylene and polyvinylidene fluoride.

[0145] For example, the polyamide includes at least one of poly(m-phenylene isophthalamide) (or meta-aramid) and polycaprolactam.

[0146] In some embodiments, the functional material also includes a plasticizer that facilitates the formation of a stable film layer from the organic polymer, and the plasticizer can be eluted in subsequent steps, enabling the formation of a porous structure inside the polymer-based film.

[0147] Optionally, the plasticizer includes at least one of paraffin wax, dimethyl tetraethanolamine, and dioctyl phthalate.

[0148] Optionally, the mass content of the plasticizer is 1% to 3%, depending on the mass of the organic polymer, cyclophosphonitrile compound, and plasticizer. When the mass content of the plasticizer is within the above range, it is beneficial to construct a porous structure.

[0149] Step S200, heat treatment step, to melt the organic polymer.

[0150] The heat treatment temperature is above the melting point of the organic polymer, causing the organic polymer to melt and become fluid, which is beneficial for the uniform dispersion of cyclophosphamide compounds in the organic polymer.

[0151] Step S300, film formation step.

[0152] The molten heat-treated structure is pressed under pressure to form a film layer.

[0153] In some implementations, the pressure for pressurization is 10 MPa to 30 MPa.

[0154] In some implementations, step S300 may further include: Step S310: Heat treatment is performed on the heat-treated structure to form an initial film layer; Step S320: Remove the thickener from the initial membrane layer to form a porous structure inside the initial membrane layer, thereby preparing the isolation membrane.

[0155] Thickeners in the initial film layer can be removed by solvent elution, for example, by placing the initial film layer in dichloromethane or trichloroethylene solvent to extract the thickener from the initial film layer, thereby forming a porous structure inside the initial film layer.

[0156] Example The following embodiments describe the contents disclosed in 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 the embodiments of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, 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.

[0157] Example: Preparation of cyclophosphonitrile compounds Preparation of the compound shown in Example I-1 .

[0158] The preparation method of this compound is as follows: Mix 10g of trifluoroiodosilane with 10g of... FeSO4 and H2O2 were added to dimethyl sulfoxide (DMSO) solvent, and the mixture was reacted at 55°C for 2 hours. The product was then separated.

[0159] Preparation of the compound shown in Example I-2 .

[0160] The preparation method of this compound is as follows: 10g of cyclotriphosphazene 15g of trifluoroiodosilane and 20g of pentafluoroiodoethane were added to dimethyl sulfoxide (DMSO) solvent, along with ferrous sulfate (Fe(II)) and H2O2. The mixture was reacted at 100℃ for 8 hours, and the product was then separated.

[0161] Preparation of compounds shown in Formula I-3 in Examples .

[0162] 10g of cyclotriphosphazene 15g of trifluoroiodosilane and 35g of heptafluoro-1-iodopropane were added to dimethyl sulfoxide (DMSO) solvent, along with Fe(II) and H2O2. The mixture was reacted at 100℃ for 8 hours, and the product was then separated.

[0163] Preparation of the compound shown in Example II-1 .

[0164] 10g of cyclotriphosphazene 15g of trifluoroiodomethane and 15g of trifluoroiodosilane were reacted in dimethyl sulfoxide (DMSO) solvent with Fe(II) and H2O2 at 80-120℃ for 8 hours, and the intermediate product was obtained by separation. The intermediate product was mixed with oxygen difluoride at 100°C for 6 hours, and the product was obtained by separation.

[0165] Preparation of the compound shown in Example II-2 .

[0166] 10g of cyclotriphosphazene 15g of pentafluoroiodoethane and 15g of trifluoroiodosilane were reacted with Fe(II) and H2O2 in dimethyl sulfoxide (DMSO) solvent at 100℃ for 8 hours, and the intermediate product was obtained by separation. The intermediate product was mixed with oxygen difluoride at 100°C for 6 hours, and the product was obtained by separation.

[0167] Preparation of the compound shown in Example II-3 .

[0168] 10g of cyclotriphosphazene 15g of pentafluoroiodoethane and 15g of heptafluoro-1-iodopropane were reacted in dimethyl sulfoxide (DMSO) solvent with Fe(II) and H2O2 at 100℃ for 8 hours, and the intermediate product was obtained by separation. The intermediate product was mixed with oxygen difluoride at 100°C for 6 hours, and the product was obtained by separation.

[0169] Example: Preparation of battery cells Example 1 1. Preparation of positive electrode sheet Aluminum foil with a thickness of 12μm was used as the positive electrode current collector.

[0170] Lithium nickel cobalt manganese oxide (LiNi) is used as the positive electrode active material. 0.8 Co 0.1 Mn 0.1O2 (NCM811), conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 98:1:1 and thoroughly stirred in an appropriate amount of solvent N-methylpyrrolidone (NMP) to form a uniform positive electrode slurry.

[0171] The positive electrode slurry is uniformly coated onto both sides of the positive electrode current collector aluminum foil. After drying and cold pressing, a positive electrode film layer is formed on the positive electrode current collector, thus obtaining the positive electrode sheet. The loading of the positive electrode film layer is 25 mg / cm³. 2 .

[0172] 2. Preparation of negative electrode sheet A 50 μm lithium foil is rolled onto a 12 μm copper foil to form a negative electrode.

[0173] 3. Separating membrane An organic polymer, a plasticizer (paraffin wax), and a cyclophosphamide compound are mixed; the plasticizer content in the organic polymer, plasticizer (paraffin wax), and cyclophosphamide compound is 2% by mass. The organic polymer is heat-treated to melt it, and the functional material is dispersed in the organic polymer to form a heat-treated structure; the heat treatment temperature is 120℃. The initial film layer is formed by pressurizing and heat-treating the structure; the pressure is 0.5 MPa. The plasticizer in the initial membrane layer was extracted with dichloromethane, forming a porous structure in the initial membrane layer, and a separation membrane was prepared. The average pore size of the porous structure of the separation membrane was 0.05 μm.

[0174] 4. Preparation of electrolyte An electrolyte was prepared by adding 4 mol / L of lithium bisfluorosulfonylimide (LiFSI) to the organic solvent 1,2-dimethoxyethane (DME).

[0175] 5. Preparation of battery cells The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. The electrode assembly is then wound up to obtain an electrode assembly. The electrode assembly is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a battery cell is obtained, which is a lithium metal battery.

[0176] Comparative Example 1 A lithium-ion battery was prepared using a method similar to that of Example 1, except that a polyethylene film was used as the separator.

[0177] Examples 2 to 6 Lithium-ion batteries were prepared using a method similar to that of Example 1, except that the material of the cyclophosphonitrile compound in the separator was adjusted.

[0178] Examples 7 to 9 Lithium-ion batteries were prepared using a method similar to that in Example 1, except that the mass content of cyclophosphonitrile compounds in the separator was adjusted.

[0179] Examples 10 and 11 A lithium-ion battery was prepared using a method similar to that of Example 1, except that the material of the polymer base film of the separator was adjusted.

[0180] Examples 12 and 13 A lithium-ion battery was prepared using a method similar to that in Example 1, except that the molecular weight of the polymer base film of the separator was adjusted.

[0181] Performance testing 1. Cyclic testing of individual battery cells At 25℃, a single battery cell is charged at a constant current of 0.2C to 4.3V, then charged at a constant voltage of 4.3V to a current of 0.05C, and then discharged at a constant current of 1C to 2.8V. This constitutes one charge-discharge cycle. Taking the initial discharge capacity as 100%, calculate the number of cycles required to achieve an 80% capacity retention rate for the single battery cell. The capacity retention rate (%) after n cycles = (Discharge capacity of the nth cycle / Initial discharge capacity) × 100%.

[0182] 2. Thermal runaway test of individual battery cells Hot-box tests were conducted on the battery cells of each embodiment and comparative example, referring to GB / 38031-2020 Safety Requirements for Power Batteries for Electric Vehicles; specifically: Discharge the individual battery cells to 2.8V at a current of 0.33C and let them rest for 1 hour; Charge the battery cells to 4.3V at a current of 0.2C, then charge them to 0.05C at a constant voltage, and let them rest for 1 hour. The battery cells were placed in a hot box and heated from the ambient temperature to 130±2℃ at a rate of 10℃ / min, and held at that temperature for 30min. The process is terminated when thermal runaway occurs in a single battery cell. The temperature monitored by the thermal chamber at the time of thermal runaway in the battery cell is recorded as the thermal runaway temperature.

[0183] Battery cells with a thermal runaway temperature below 220°C are considered runaway-prone batteries. A battery cell with a thermal runaway temperature greater than or equal to 220°C is considered an acceptable battery.

[0184] Test Results The test results are shown in Table 1.

[0185] Table 1 As can be seen from Table 1, The separator in Comparative Example 1 is a polyethylene film layer with a cycle count of 582 cycles, which is relatively good. However, its flame retardant performance is poor, the thermal runaway temperature of the battery cell is relatively low, the risk of thermal runaway is high, and the reliability of the battery cell is relatively poor.

[0186] In this embodiment, cyclophosphonitrile compounds are added to the separator. At high temperatures, these compounds can be released into the electrolyte system, capturing combustion free radicals, blocking thermal runaway reactions, and absorbing heat during molecular decomposition, thus further achieving physical cooling and improving the reliability of the battery cell. Since the cyclophosphonitrile compounds are located in the separator, they have virtually no adverse effect on interfacial film formation during the cyclic charging and discharging of the battery cell. For example, the cycle count in Example 1 is 587 cycles, resulting in good cycle performance of the battery cell and improved reliability based on excellent cycle performance.

[0187] Cyclophosphazene compounds, when modified for different materials, can improve reliability while maintaining excellent cycling performance.

[0188] As the number of fluorine atoms in cyclophosphonitrile compounds increases, the flame retardant effect improves, the thermal runaway temperature is increased, and the reliability of battery cells is enhanced.

[0189] As the mass content of cyclophosphonitrile compounds increases, the flame retardant effect improves, which can raise the thermal runaway temperature and enhance the reliability of battery cells. However, once the mass content of cyclophosphonitrile compounds increases to a certain level, such as 5% or higher, the increase in flame retardant effect no longer becomes significant.

[0190] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the present application, and that changes, substitutions and modifications can be made to the embodiments without departing from the spirit, principles and scope of the present application.

Claims

1. A battery cell, comprising a separator, said separator comprising: Polymer-based membrane with a porous structure; A cyclophosphonitrile compound is dispersed in the polymer-based film. The cyclophosphonitrile compound comprises a cyclophosphonitrile cyclic group and a functional group attached to the cyclophosphonitrile cyclic group. The functional group includes at least one of fluoroalkyl and fluorosilyl groups. The cyclophosphonitrile compounds include at least one of the compounds shown in Formula I-1, Formula I-2, Formula I-3, and Formula II. Formula I-1, Formula I-2, Formula I-3, Formula II, In Formula II, R4, R5, R6 and R7 each independently include a hydrogen atom or a fluorosilyl group; Q4, Q5, Q6, and Q7 each independently include a hydrogen atom or a fluoroalkyl group. At least one of R4, R5, R6, R7, Q4, Q5, Q6 and Q7 includes a fluorosilyl or a fluoroalkyl group; The cyclophosphonitrile compound has a mass content of 1% to 10% in the separator.

2. The battery cell according to claim 1, wherein, R4, R5, R6 and R7 each independently include a fluorosilyl group; and / or Q4, Q5, Q6 and Q7 each independently include a fluorosilyl group.

3. The battery cell according to claim 1, wherein, The fluoroalkyl group includes C1 to C5 fluoroalkyl groups.

4. The battery cell according to claim 3, wherein, The fluoroalkyl group includes C2 to C4 fluoroalkyl groups.

5. The battery cell according to claim 1, wherein, The cyclophosphonitrile compounds include at least one of the compounds shown in Formula II-1 to Formula II-3.

6. The battery cell according to claim 1, wherein, The cyclophosphonitrile compound has a mass content of 2% to 5% in the separator.

7. The battery cell according to claim 1, wherein, The longitudinal heat shrinkage rate of the separator membrane after heat treatment at 45°C for 2 hours is 1.5% to 5.0%; and / or The transverse heat shrinkage rate of the separator membrane after heat treatment at 45°C for 2 hours is 1.0% to 4.0%; and / or The elongation of the separator is 10% to 20%.

8. The battery cell according to claim 1, wherein, The polymer-based film includes at least one of polyolefin, polyamide, polyimide and polyethylene terephthalate.

9. The battery cell according to claim 8, wherein, The polyolefin includes at least one of polyethylene, polypropylene, and polyvinylidene fluoride; and / or The polyamide includes at least one of poly(m-phenylene isophthalamide) and polycaprolactam.

10. A battery device comprising a battery cell as claimed in any one of claims 1 to 9.

11. An electrical device comprising the battery device as described in claim 10.

12. A separating membrane, comprising: Polymer-based membrane with a porous structure; A cyclophosphonitrile compound is dispersed in the polymer-based film. The cyclophosphonitrile compound includes a cyclophosphonitrile cyclic group and a functional group attached to the cyclophosphonitrile cyclic group. The functional group includes at least one of fluoroalkyl and fluorosilyl groups. The cyclophosphonitrile compounds include at least one of the compounds shown in Formula I-1, Formula I-2, Formula I-3, and Formula II. Equation I-1, Equation I-2, Formula I-3, Formula II, In Formula II, R4, R5, R6 and R7 each independently include a hydrogen atom or a fluorosilyl group; Q4, Q5, Q6, and Q7 each independently include a hydrogen atom or a fluoroalkyl group. At least one of R4, R5, R6, R7, Q4, Q5, Q6 and Q7 includes a fluorosilyl or a fluoroalkyl group; The cyclophosphonitrile compound has a mass content of 1% to 10% in the separator.

13. A cyclophosphonitrile compound for use in a separator membrane, comprising a cyclophosphonitrile cyclic group and a functional group attached to the cyclophosphonitrile cyclic group, wherein the functional group comprises at least one of fluoroalkyl and fluorosilyl groups; The cyclophosphonitrile compounds include at least one of the compounds shown in Formula I-1, Formula I-2, Formula I-3, and Formula II. Equation I-1, Equation I-2, Formula I-3, Formula II, In Formula II, R4, R5, R6 and R7 each independently include a hydrogen atom or a fluorosilyl group; Q4, Q5, Q6, and Q7 each independently include a hydrogen atom or a fluoroalkyl group. At least one of R4, R5, R6, R7, Q4, Q5, Q6, and Q7 includes a fluorosilyl or fluoroalkyl group.

14. A method for preparing a separating membrane, comprising: An organic polymer and a functional material are mixed, wherein the functional material includes a cyclophosphonitrile compound, the cyclophosphonitrile compound includes a cyclophosphonitrile cyclic group and a functional group attached to the cyclophosphonitrile cyclic group, and the functional group includes at least one of fluoroalkyl and fluorosilyl groups; The organic polymer is heat-treated to make it thermally melted, and the functional material is dispersed in the organic polymer to form a heat-treated structure. The heat-treated structure is pressurized to form an isolation membrane. The cyclophosphonitrile compounds include at least one of the compounds shown in Formula I-1, Formula I-2, Formula I-3, and Formula II. Formula I-1, Formula I-2, Formula I-3, Formula II, In Formula II, R4, R5, R6 and R7 each independently include a hydrogen atom or a fluorosilyl group; Q4, Q5, Q6, and Q7 each independently include a hydrogen atom or a fluoroalkyl group. At least one of R4, R5, R6, R7, Q4, Q5, Q6 and Q7 includes a fluorosilyl or a fluoroalkyl group; The cyclophosphonitrile compound has a mass content of 1% to 10% in the separator.

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