Separator, secondary battery, and electric device

Abstract

The utility model relates to an isolating membrane, a secondary battery and an electric device, and the isolating membrane comprises a base membrane, a first coating and a second coating, the first coating is arranged on at least one side of the base film; the second coating is arranged on at least one side of a composite film layer formed by the base film and the first coating; the first coating comprises heat-resistant particles; the second coating includes a coolant. The secondary battery using the isolating membrane provided by the utility model has excellent safety performance.

Description

Technical Field

[0001] The present application relates to the technical field of batteries, and particularly to separator membranes, secondary batteries, and electrical devices. Background Art

[0002] In recent years, with the development of secondary battery technology, secondary batteries have been widely used in energy storage power systems such as hydraulic, thermal, wind, and solar power stations, as well as in multiple fields such as power tools, electric bicycles, electric motorcycles, electric vehicles, and aerospace.

[0003] With the increasing demand for secondary batteries, the safety issue of batteries has gradually become one of the most concerned issues in battery design. Summary of the Utility Model

[0004] The present application is made in view of the above problems, and its purpose is to provide a separator membrane, a secondary battery, and an electrical device, and the secondary battery using the above separator membrane has excellent safety performance.

[0005] To achieve the above object, a first aspect of the present application provides a separator membrane, including: a base film, a first coating, and a second coating; the first coating is disposed on at least one side of the base film; the second coating is disposed on at least one side of the composite film layer formed by the base film and the first coating; the first coating includes heat-resistant particles; the second coating includes a coolant.

[0006] In the present application, the separator membrane includes a first coating containing heat-resistant particles on at least one side of the base film. Coating the first coating on the base film helps to improve the rigidity of the separator membrane. Therefore, the first coating can provide a supporting effect on the base film, control the shrinkage of the base film when heated, and is beneficial to improving the safety performance of the secondary battery. On this basis, by providing a second coating in the separator membrane, cooling and extinguishing can be carried out when the internal temperature of the battery is high and a fire occurs, which further contributes to the safety performance of the secondary battery.

[0007] In some embodiments, the thickness of the first coating is 0.5 μm to 1.5 μm. Thereby, while controlling the shrinkage of the base film, the transmission of active ions is not affected, that is, the safety performance and power performance of the secondary battery are taken into account.

[0008] In some embodiments, the heat-resistant particles include inorganic materials; the inorganic materials include at least one of boehmite, aluminum oxide, silicon dioxide, zirconium oxide, and titanium dioxide. The above inorganic materials are used as the main heat-resistant materials of the first coating, and have the advantages of good thermal stability and flame retardancy. On the one hand, they can provide support for the base film and control the shrinkage of the base film, and on the other hand, they can achieve flame retardancy, which is beneficial to the safety performance of the secondary battery.

[0009] In some embodiments, the thickness of the second coating is 0.5 μm to 1.5 μm. Thus, while achieving the fire extinguishing function, the transmission of active ions is not affected, that is, the safety performance and power performance of the secondary battery are taken into account.

[0010] In some embodiments, the coolant includes a housing and a coolant located inside the housing; the boiling point of the coolant is less than the boiling point of the housing. Since the boiling point of the coolant is less than that of the housing, when heat is generated inside the battery, the coolant will vaporize preferentially and break through the housing to be released, thus achieving the effects of cooling and fire extinguishing, which is beneficial to the safety performance of the secondary battery.

[0011] In some embodiments, the coolant includes at least one of perfluorocyclopentane, bromotrifluoropropene, tetrafluorodibromoethane, trifluorodichloroethane, and dibromomethane. Using the above materials as the coolant has the advantages of high fire extinguishing efficiency and fast speed.

[0012] In some embodiments, the material of the housing includes at least one of polyamide, urea formaldehyde resin, amino resin, epoxy resin, and alkyd resin. The above materials can be obtained by emulsion polymerization through liquid-phase interfacial reaction. As the housing material of the coolant, it has the advantage of simple preparation method.

[0013] In some embodiments, the particle size of the coolant is 0.5 to 5 μm. When the particle size of the coolant is within the above range, it is beneficial to control the thickness of the second coating within a suitable range, taking into account the safety performance and power performance of the battery.

[0014] In some embodiments, the first coating is disposed on both sides of the base film, and the second coating is disposed on both sides of the composite film layer.

[0015] In some embodiments, the thickness of the base film is 5 μm to 9 μm. When the thickness of the base film is within the above range, on the basis of meeting the isolation performance of the separator, the diffusion difficulty of active ions can be reduced, which is beneficial to the safety performance and power performance of the secondary battery.

[0016] In some embodiments, the material of the base film includes at least one of polyolefin, polyether, polyether ether ketone, polyimide, polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polyvinylidene chloride, polyethylene-propylene copolymer, and copolymer containing carbon-fluorine bond. Since the above materials have good mechanical properties and excellent electrical insulation properties, using these materials as the base film can effectively play the supporting role of the base film and the electrical isolation role of the separator, which is beneficial to improving the safety performance and power performance of the battery cell.

[0017] The second aspect of the present application further provides a secondary battery, including the separator of the first aspect of the present application.

[0018] The third aspect of the present application further provides an electrical device, including the secondary battery of the second aspect of the present application. Description of the Drawings

[0019] Figure 1 It is a schematic structural view of a separator of an embodiment of the present application Figure 1 ;

[0020] Figure 2 It is a schematic structural view of a separator of an embodiment of the present application Figure 2 ;

[0021] Figure 3 It is a schematic structural view of a separator of an embodiment of the present application Figure 3 ;

[0022] Figure 4 It is a schematic structural view of a separator of an embodiment of the present application Figure 4 ;

[0023] Figure 5 It is a schematic structural view of a separator of an embodiment of the present application Figure 5 ;

[0024] Figure 6 It is a schematic view of a battery cell of an embodiment of the present application;

[0025] Figure 7 It is Figure 6 an exploded view of the battery cell of an embodiment of the present application shown;

[0026] Figure 8 It is a schematic view of a battery module of an embodiment of the present application;

[0027] Figure 9 It is a schematic view of a battery pack of an embodiment of the present application;

[0028] Figure 10 It is Figure 9 an exploded view of the battery pack of an embodiment of the present application shown;

[0029] Figure 11 It is a schematic view of an electrical device powered by a secondary battery of an embodiment of the present application.

[0030] Description of the Reference Numerals:

[0031] 1 Battery pack; 2 Upper box body; 3 Lower box body; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 53 Top cover assembly. Detailed Embodiments

[0032] Hereinafter, embodiments of the separator, secondary battery, and electrical device of the present application will be specifically described in detail. However, there may be cases where unnecessary details are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually identical structures are omitted. This is to prevent the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the accompanying drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter recited in the claims.

[0033] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a particular range. The range defined in this way can include the end values or not include the end values, and can be combined arbitrarily, 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, ranges of 60 - 110 and 80 - 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5. In the present application, unless otherwise specified, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" are fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0034] If there is no special instruction, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0035] If there is no special instruction, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0036] If there is no special instruction, all steps of the present application can be carried out in sequence or randomly, preferably in sequence. For example, the method includes steps (a) and (b), which means that the method can include steps (a) and (b) carried out in sequence, or can also include steps (b) and (a) carried out in sequence. For example, when it is mentioned that the method may further include step (c), it means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or can also include steps (a), (c), and (b), or can also include steps (c), (a), and (b), etc.

[0037] Unless otherwise specified, the terms used in this application have the well-known meanings commonly understood by those skilled in the art.

[0038] Unless otherwise specified, the values of the various parameters mentioned in this application can be measured by various commonly used testing methods in the art. For example, they can be measured according to the testing methods given in this application.

[0039] Unless otherwise specified, in this application, the term "active ion" refers to an ion that can intercalate and deintercalate between the positive and negative electrodes of a secondary battery, including but not limited to lithium ions.

[0040] As the requirements for secondary batteries are getting higher and higher, the safety issue of batteries has gradually become one of the most concerned issues in battery design. As a core material inside secondary batteries, polymer polyolefin separators have strong flammability and very strong thermal shrinkage properties. Once heat is generated inside the battery, serious safety problems will occur. However, it is difficult to directly develop a separator substrate with flame retardant function. Therefore, on the basis of the current technology, it is necessary to compound a functional coating on the surface of the base film to achieve flame retardancy and fire extinguishing of the separator and improve the safety performance of the battery.

[0041] Based on this, this application proposes a separator, a secondary battery, and an electrical device. The secondary battery using the separator provided in this application has excellent safety performance.

[0042] Separator

[0043] A first aspect of an embodiment of this application provides a separator, including a base film, a first coating, and a second coating; the first coating is disposed on at least one side of the base film; the second coating is disposed on at least one side of the composite film layer formed by the base film and the first coating; the first coating includes heat-resistant particles; the second coating includes a coolant.

[0044] In this application, the separator includes a first coating located on at least one side of the base film and containing heat-resistant particles. Coating the first coating on the base film helps to improve the rigidity of the separator. Therefore, the first coating can provide a supporting effect on the base film, control the shrinkage of the base film when heated, and is beneficial to improving the safety performance of the secondary battery. On this basis, by providing a second coating in the separator, it can be cooled and extinguished when the temperature inside the battery is high and a fire breaks out, further contributing to the safety performance of the secondary battery.

[0045] The base film is the main component of the separator, which provides the basic structure and support for the entire separator. The material selection of the base film has an important impact on the performance of the separator. Common base film materials are polymers.

[0046] In some embodiments, the first coating is disposed on one side of the base film, and the second coating is located on one side of the first coating in the composite film layer formed by the base film and the first coating. Thus, the shrinkage of the base film when heated can be controlled by the first coating, reducing the short-circuit probability of the secondary battery, and the second coating can cool and extinguish the fire when the secondary battery catches fire, which is beneficial to the safety performance of the secondary battery.

[0047] Figure 1 is a schematic structural diagram of a separator of an embodiment of the present application Figure 1 , such as Figure 1 shown, the separator 100 includes a base film 10, a first coating 20, and a second coating 30. The first coating 20 is disposed on one side of the base film 10, and the second coating 30 is disposed on one side of the first coating 20 in the composite film layer 40 formed by the base film 10 and the first coating 20.

[0048] In some embodiments, the first coating is disposed on one side of the base film, and the second coating is located on one side of the base film in the composite film layer formed by the base film and the first coating. In this way, the shrinkage of the base film when heated can be controlled by the first coating, reducing the short-circuit probability of the secondary battery, and the second coating can extinguish the fire when the secondary battery catches fire, which is beneficial to the safety performance of the secondary battery.

[0049] Figure 2 is a schematic structural diagram of a separator of an embodiment of the present application Figure 2 , such as Figure 2 shown, the separator 100 includes a base film 10, a first coating 20, and a second coating 30. The first coating 20 is disposed on the surface of one side of the base film 10, and the second coating 30 is disposed on the surface of the base film 10 in the composite film layer 40 formed by the base film 10 and the first coating 20.

[0050] In some embodiments, the first coating is disposed on the surface of one side of the base film, and the second coating is located on both surfaces of the composite film layer formed by the base film and the first coating.

[0051] Figure 3 is a schematic structural diagram of a separator of an embodiment of the present application Figure 3 , such as Figure 1 shown, the separator 100 includes a base film 10, a first coating 20, and a second coating 30. The first coating 20 is disposed on the surface of one side of the base film 10, and the second coating 30 is disposed on both sides of the composite film layer 40 formed by the base film 10 and the first coating 20, that is, the second coating is located on the surfaces of the base film 10 and the first coating 20 in the composite film layer 40.

[0052] In some embodiments, the first coating is disposed on the surfaces of both sides of the base film, and the second coating is located on one surface of the composite film layer formed by the base film and the first coating. Thus, the shrinkage of the base film when heated can be controlled by the first coating, reducing the short-circuit probability of the secondary battery, and the second coating can cool and extinguish the fire when the secondary battery catches fire, which is beneficial to the safety performance of the secondary battery.

[0053] Figure 4 is a schematic structural view of a separator according to an embodiment of the present application Figure 4 , such as Figure 4 shown, the separator 100 includes a base film 10, a first coating 20, and a second coating 30. The first coating 20 is disposed on the surfaces of both sides of the base film 10, and the second coating 30 is disposed on one surface of the composite film layer 40 formed by the base film 10 and the first coating 20, that is, the second coating 30 is located on the surface of one of the first coatings 20 in the composite film layer 40.

[0054] In some embodiments, the first coating is disposed on both sides of the base film, and the second coating is disposed on both sides of the composite film layer. Thus, the shrinkage of the base film when heated can be controlled by the first coating, reducing the short-circuit probability of the secondary battery, and the second coating can cool and extinguish the fire when the secondary battery catches fire, which is beneficial to the safety performance of the secondary battery.

[0055] Figure 5 is a schematic structural view of a separator according to an embodiment of the present application Figure 5 , such as Figure 5 shown, the separator 100 includes a base film 10, a first coating 20, and a second coating 30. The first coating 20 is disposed on both sides of the base film 10, and the second coating 30 is disposed on both sides of the composite film layer 40 formed by the base film 10 and the first coating 20, that is, the second coating 30 is located on the surfaces of the two first coatings 20 in the composite film layer 40.

[0056] In some embodiments, the thickness of the first coating is 0.5 μm to 1.5 μm. Optionally, the thickness of the first coating is 1 μm. When the thickness of the first coating is set within the above range, it can control the shrinkage of the base film while not affecting the transmission of active ions, that is, taking into account the safety performance and power performance of the secondary battery.

[0057] In some embodiments, the first coating further includes a first dispersant and a first binder, and the mass ratio of the heat-resistant particles, the first dispersant, and the first binder in the first coating is (6-8):(1-2):(1-2). When the mass ratio of the heat-resistant particles, the first dispersant, and the first binder in the first coating is within the above range, the first coating has good uniformity and stability, can realize its function of controlling the shrinkage of the base film, and is beneficial to the safety performance of the secondary battery.

[0058] In some embodiments, the first dispersant may be, for example, one or more of polyethylene glycol (PEG), polyvinyl pyrrolidone (PVP), sodium polyacrylate, and sodium carboxymethyl cellulose.

[0059] In some embodiments, the first binder can be, for example, polyvinylidene fluoride (PVDF), poly N-vinyl pyrrolidone (PVP), polyacrylic acid (PAA), sodium carboxymethyl cellulose, polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethyl methacrylate, polyacrylonitrile, polyvinyl acetate, polyethylene-co-vinyl acetate, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, acrylonitrile-styrene-butadiene copolymer, and one or more of polyimide.

[0060] In some embodiments, the heat-resistant particles comprise an inorganic material; the inorganic material comprises at least one of boehmite, aluminum oxide, silicon dioxide, zirconium oxide, and titanium dioxide, and optionally, boehmite. These inorganic materials, as the primary material for the first coating layer, offer advantages such as excellent thermal stability and flame retardancy. They provide excellent support for the base film and control its shrinkage, while also being flame-retardant, contributing to the safety of the secondary battery.

[0061] In some embodiments, the inorganic materials may further include SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, Y2O3, SiC, BaTiO3, Pb(Zr,Ti)O3, Pb(Mg3Nb 2 / 3 )O3-PbTiO3, HfO2, lithium phosphate (Li3PO4), lithium titanium phosphate (Li x Ti y (PO4)3,0 <x<2,0<y<3)、磷酸钛铝锂(Li x Al y Ti z (PO4)3,0 <x<2,0<y<1,0<z<3)、(LiAlTiP) x O y Type glass(0 <x<4,0<y<13)、钛酸镧锂(Li x La y TiO3,0 <x<2,0<y<3)、硫代磷酸锗锂(Li x Ge y P z S w , 0 <x<4,0<y<1,0<z<1,0<w<5)、氮化锂(Li x Ny (where 0 < x < 4, 0 < y < 2), SiS₂ type glass (Li x Si y S z (where 0 < x < 3, 0 < y < 2, 0 < z < 4), and P₂S₅ type glass (Li x P y S z (where 0 < x < 3, 0 < y < 3, 0 < z < 7), etc., or one or more of them.

[0062] In some embodiments, the above heat-resistant particles may further include an organic material, which may be, for example, one or more of polyimide, polyvinylidene fluoride, and polyetherimide.

[0063] In some embodiments, the thickness of the second coating is 0.5 μm to 1.5 μm. Optionally, the thickness of the second coating is 1 μm. Setting the thickness of the second coating within the above range can achieve the fire extinguishing function while not affecting the transport of active ions, that is, taking into account the safety performance and power performance of the secondary battery.

[0064] In some embodiments, the coolant includes a housing and a coolant located inside the housing; the boiling point of the coolant is less than the boiling point of the housing. Since the boiling point of the coolant is less than the boiling point of the housing, when heat is generated inside the battery, the coolant will vaporize preferentially and break through the housing to be released, thereby achieving the effects of cooling and fire extinguishing, which is beneficial to the safety performance of the secondary battery.

[0065] In some embodiments, the coolant includes at least one of perfluorocyclopentane, bromotrifluoropropene, 1,2-dibromo-1,1,2,2-tetrafluoroethane, 1,1-dichloro-1,2,2,2-tetrafluoroethane, and dibromomethane. Using the above materials as the coolant has the advantages of high fire extinguishing efficiency and fast speed.

[0066] In some embodiments, the material of the housing includes at least one of polyamide, urea-formaldehyde resin, amino resin, epoxy resin, and alkyd resin. The above materials can be obtained by emulsion polymerization through a liquid-phase interfacial reaction. Using the housing material of the coolant has the advantage of simple preparation method.

[0067] In some embodiments, the particle size of the coolant is 0.5 μm to 5 μm. Optionally, the particle size of the coolant is 0.5 μm to 1 μm. When the particle size of the coolant is within the above range, it is beneficial to control the thickness of the second coating within a suitable range, taking into account the safety performance and power performance of the battery.

[0068] In some embodiments, the second coating comprises a second binder and a second dispersant; the mass ratio of the coolant, the second dispersant, and the second binder in the second coating is (6 - 8):(1 - 2):(1 - 2). The mass ratio of the coolant, the second dispersant, and the second binder in the second coating within the above range enables the second coating to have good uniformity and stability, capable of achieving the fire extinguishing function and being beneficial to the safety performance of the secondary battery.

[0069] In some embodiments, the second dispersant can be, for example, one or more of polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), sodium polyacrylate, and sodium carboxymethyl cellulose.

[0070] In some embodiments, the second binder can be, for example, one or more of polyvinylidene fluoride (PVDF), poly-N-vinylpyrrolidone (PVP), polyacrylic acid (PAA), polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethyl methacrylate, polyacrylonitrile, polyvinyl acetate, polyethylene-co-vinyl acetate, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylated amylose, cyanoethylated polyvinyl alcohol, cyanoethylated cellulose, cyanoethylated sucrose, amylose, carboxymethyl cellulose, acrylonitrile-butadiene-styrene copolymer, and polyimide.

[0071] In some embodiments, the thickness of the base film is 5 μm to 9 μm, optionally, the thickness of the base film is 7 μm. The thickness of the base film within the above range can reduce the diffusion difficulty of active ions on the basis of meeting the isolation performance of the separator, which is beneficial to balancing the safety performance and power performance of the secondary battery.

[0072] In some embodiments, the material of the base film includes polyolefin, polyether, polyether ether ketone, polyimide, polytetrafluoroethylene, polyvinyl fluoride, and polyvinylidene fluoride. Since polyolefin, polyether, polyether ether ketone, polyimide, polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polyvinylidene chloride, polyethylene-propylene copolymer, copolymers containing carbon-fluorine bonds, etc. have good mechanical properties and excellent electrical insulation properties, using these materials as the base film can effectively play the supporting role of the base film and the electrical isolation role of the separator, which is beneficial to improving the safety performance and power performance of the battery cell.

[0073] In some embodiments, the separator is applied to a secondary battery and is disposed between the positive electrode plate and the negative electrode plate of the secondary battery, mainly serving to prevent short circuit between the positive and negative electrodes and allowing ions to pass through simultaneously.

[0074] In some embodiments, the separator is applied to a secondary battery. Exemplarily, the secondary battery may include a lithium-ion battery, a lithium-sulfur battery, or a lithium-metal battery.

[0075] Secondary battery

[0076] The term "secondary battery" mentioned herein refers to a battery cell, a battery module, or a battery pack.

[0077] Generally, a secondary battery includes a positive electrode plate, a negative electrode plate, an electrolyte, and the separator described in the first aspect above. During the charging and discharging process of the battery, active ions are intercalated and deintercalated back and forth between the positive electrode plate and the negative electrode plate. The electrolyte plays a role in conducting ions between the positive electrode plate and the negative electrode plate.

[0078] [Positive Electrode Plate]

[0079] The positive electrode plate includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material.

[0080] As an example, the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode film layer is provided on either one or both of the two opposite surfaces of the positive electrode current collector.

[0081] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be formed by forming a metal material (such as 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 (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0082] In some embodiments, when the battery cell is a lithium-ion battery, the positive electrode active material may be a positive electrode active material known in the art for lithium-ion batteries. As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi1 / 3 Co 1 / 3Mn 1 / 3 O2 (which can also be abbreviated as NCM 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O2 (which can also be abbreviated as NCM 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O2 (which can also be abbreviated as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O2 (which can also be abbreviated as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O2 (which can also be abbreviated as NCM 811 )、lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.1 Al 0.05 O2) and at least one of its modified compounds, etc. Examples of olivine-structured lithium-containing phosphates may include but are not limited to lithium iron phosphate (such as LiFePO4 (which can also be abbreviated as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon.

[0083] During the charge and discharge process of the battery, the deintercalation and consumption of Li will occur, and the molar content of Li is different when the battery is discharged to different states. In the listing of the positive electrode active materials in this application, the molar content of Li is the initial state of the material, that is, the state before feeding. When the positive electrode active material is applied to the battery system and undergoes charge and discharge cycles, the molar content of Li will change.

[0084] In the listing of the positive electrode active materials in this application, the molar content of O is only the theoretical state value, and the release of oxygen from the lattice will cause the molar content of oxygen to change, and the actual molar content of O will show fluctuations.

[0085] In some embodiments, the positive electrode film layer may also optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0086] In some embodiments, the positive electrode film layer may further optionally include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0087] In some embodiments, the positive electrode plate can be prepared by the following method: dispersing the components for preparing the positive electrode plate, such as the positive electrode active material, conductive agent, binder, and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on the positive electrode current collector, and after processes such as drying and cold pressing, the positive electrode plate can be obtained.

[0088] [Negative electrode plate]

[0089] The negative electrode plate includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material.

[0090] As an example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode film layer is provided on any one or both of the two opposite surfaces of the negative electrode current collector.

[0091] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, copper foil can be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (such as 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 (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0092] In some embodiments, the negative electrode active material can be a negative electrode active material for a battery well-known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material can be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material can be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as the negative electrode active material of the battery can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0093] In some embodiments, the negative electrode film layer may further optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0094] In some embodiments, the negative electrode film layer may further optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0095] In some embodiments, the negative electrode film layer may further optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)), etc.

[0096] In some embodiments, the negative electrode plate can be prepared in the following manner: dispersing the components for preparing the negative electrode plate described above, such as the negative electrode active material, conductive agent, binder, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry on the negative electrode current collector, and after processes such as drying and cold pressing, the negative electrode plate can be obtained.

[0097] [Electrolyte]

[0098] The electrolyte plays a role in conducting ions between the positive electrode plate and the negative electrode plate. There is no specific limitation on the type of the electrolyte in this application, and it can be selected according to requirements.

[0099] In some embodiments, the electrolyte uses an electrolytic solution. The electrolytic solution includes an electrolyte salt and a solvent.

[0100] 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 bis(oxalato)borate, lithium difluoro bis(oxalato)phosphate, and lithium tetrafluorooxalate phosphate.

[0101] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene 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.

[0102] In some embodiments, the electrolyte may optionally further include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performances, such as additives for improving the overcharge performance of the battery, additives for improving the high-temperature or low-temperature performance of the battery, etc.

[0103] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be made into an electrode assembly through a winding process or a stacking process.

[0104] In some embodiments, the battery cell may include an outer package. The outer package can be used to encapsulate the above-mentioned electrode assembly and electrolyte.

[0105] In some embodiments, the outer package of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the battery cell can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic. As plastics, polypropylene, polybutylene terephthalate, and polybutylene succinate, etc. can be enumerated.

[0106] This application does not particularly limit the shape of the battery cell, and it can be cylindrical, square, or any other arbitrary shape. For example, Figure 6 is a battery cell 5 with a square structure as an example.

[0107] In some embodiments, referring to Figure 7 , the outer package may include a housing 51 and a top cover assembly 53. Among them, the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the top cover assembly 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet, and the separator can form an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte infiltrates in the electrode assembly 52. The number of electrode assemblies 52 included in the battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0108] In some embodiments, the battery cells can be assembled into a battery module. The number of battery cells included in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0109] Figure 8 is a battery module 4 as an example. Referring to Figure 8 , in the battery module 4, a plurality of battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other arbitrary manner. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0110] Optionally, the battery module 4 may further include a housing having an accommodation space, and a plurality of battery cells 5 are accommodated in the accommodation space.

[0111] In some embodiments, the above battery modules may also be assembled into a battery pack. The number of battery modules included in the battery pack may be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery pack.

[0112] Figure 9 and Figure 10 is a battery pack 1 as an example. Refer to Figure 9 and Figure 10 , in the battery pack 1, a battery box and a plurality of battery modules 4 disposed in the battery box may be included. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0113] Electric device

[0114] The present application also provides an electrical device, and the electrical device includes the secondary battery provided by the present application. The secondary 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 may include mobile devices (such as mobile phones, laptop computers, 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, satellites, energy storage systems, etc., but is not limited thereto.

[0115] As the electrical device, battery cells, battery modules or battery packs can be selected according to its usage requirements.

[0116] Figure 11 is an electrical device as an example. The electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the electrical device for the secondary battery, a battery pack or a battery module can be adopted.

[0117] Another example of the device may be a mobile phone, a tablet computer, a laptop computer, etc. This device usually requires being thin and light, and battery cells can be used as the power source.

[0118] Embodiment

[0119] The embodiments of the present application will be described below. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as a limitation to the present application. For those without specific technologies or conditions noted in the embodiments, the technologies or conditions described in the literature in the field or according to the product specifications are followed. For the reagents or instruments without the manufacturer noted, they are all conventional products that can be obtained through commercial purchase.

[0120] Example 1

[0121] Preparation of the positive electrode sheet: The positive electrode active material LiNi 0.8 Co 0.01 Mn 0.01 O2, the binder polyvinylidene fluoride, and the conductive agent Super P are mixed in a mass ratio of 97:2:1, and an appropriate amount of the solvent N-methylpyrrolidone (NMP) is added and stirred evenly to obtain the positive electrode slurry. The positive electrode slurry is coated on both surfaces of the positive electrode current collector aluminum foil, and after drying and cold pressing, the positive electrode sheet is obtained.

[0122] Preparation of the negative electrode sheet: The negative electrode active material artificial graphite, the conductive agent Super P, the binder styrene-butadiene rubber, and the thickener sodium carboxymethyl cellulose are fully stirred and mixed in a mass ratio of 96.2:0.6:1.3:1.9 in an appropriate amount of the solvent deionized water to obtain the negative electrode slurry. The negative electrode slurry is coated on both surfaces of the negative electrode current collector copper foil, and after drying and cold pressing, the negative electrode sheet is obtained.

[0123] Separator: The base film is coated with a first coating and a second coating on one side in sequence. Among them, the first coating includes the inorganic material boehmite, the first dispersant PVP, and the first binder PVDF. Among them, the mass ratio of boehmite, PVP, PVDF, and deionized water in the slurry of the first coating is 2:0.5:0.5:7. The second coating includes a coolant (polyamide shell + perfluoromethylcyclohexanone coolant), the second dispersant PVP, and the second binder PVDF. Among them, the mass ratio of the coolant, PVP, PVDF, and deionized water in the slurry of the second coating is 2:0.5:0.5:7. The thickness of the base film is 7 μm, the thickness of the first coating is 1 μm, and the thickness of the second coating is 1 μm.

[0124] Electrolyte: Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain a solvent, and then LiPF6 is dissolved in the above solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0125] Place the prepared positive electrode sheet and negative electrode sheet in order, with the separator membrane in the middle of the positive electrode sheet and the negative electrode sheet to play a separating role, and then wind them to obtain an electrode assembly; place the electrode assembly in an outer package, inject electrolyte after drying, and go through processes such as vacuum packaging, standing, formation, and aging to obtain a secondary battery.

[0126] Example 2

[0127] Assemble the secondary battery in the same manner as in Example 1, except that the structure of the separator membrane used is that the base film is coated with a first coating and a second coating on both sides respectively, and the compositions of the first coating and the second coating are the same as those in Example 1.

[0128] Example 3

[0129] Assemble the secondary battery in the same manner as in Example 1, except that the structure of the separator membrane used is that the base film is coated with a first coating and a second coating on both sides respectively, and the second coating is coated on the surface of the first coating away from the base film, and the compositions of the first coating and the second coating are the same as those in Example 1.

[0130] Example 4

[0131] Assemble the secondary battery in the same manner as in Example 1, except that the structure of the separator membrane used is that the base film is coated with a first coating and a second coating in sequence on both sides, and the compositions of the first coating and the second coating are the same as those in Example 1.

[0132] Comparative Example 1

[0133] Assemble the secondary battery in the same manner as in Example 1, except that the structure of the separator membrane used is that the base film is coated with a first coating on one side only, and the composition of the first coating is the same as that in Example 1.

[0134] Comparative Example 2

[0135] Assemble the secondary battery in the same manner as in Example 1, except that the structure of the separator membrane used is that the base film is coated with a second coating on one side only, and the composition of the second coating is the same as that in Example 1.

[0136] Comparative Example 3

[0137] Assemble the secondary battery in the same manner as in Example 1, except that the structure of the separator membrane used is that the base film is coated with a second coating and a first coating in sequence on one side only, and the compositions of the first coating and the second coating are both the same as those in Example 1.

[0138] Performance Test of Secondary Battery

[0139] 1) Power Performance Test

[0140] At 25°C, the secondary battery is charged at a constant current of 1C with constant voltage up to the upper cut-off voltage of 4.25V, and then charged at constant voltage until the current reaches 0.05C; after standing for 5 minutes, the secondary battery is discharged at 1C for 30 minutes to adjust the SOC to 50%, the voltage U1 is recorded, and then discharged at a constant current of 3C for 30 seconds, and the voltage U2 is recorded. The power of the secondary battery = lower cut-off voltage × (U1 - lower cut-off voltage) / (U1 - U2) / 3C. Among them, the lower cut-off voltage is 2.8V.

[0141] 2) Safety performance test

[0142] At 25°C, the secondary battery is charged at a constant current of 0.33C with constant voltage up to the upper cut-off voltage of 4.25V, and then charged at constant voltage until the current reaches 0.05C. At this time, the secondary battery is in a fully charged state; the fully charged secondary battery is fixed on the fixture, the positive and negative electrodes of the secondary battery are connected to the voltage detection line, and the temperature sensing line is arranged on the surface of the secondary battery. A high-temperature resistant steel needle with a diameter of 5mm is vertically passed through the large surface of the secondary battery at a speed of 25mm / s, and the change of the voltage of the secondary battery with time is recorded after standing for 1 hour. If any of the conditions that the secondary battery smokes, catches fire after the nail penetration or the voltage drop of the secondary battery is greater than 0.5V after standing for 1 hour after the nail penetration occurs, it is determined that the secondary battery fails the nail penetration test. The number of secondary battery samples for this test is 10, and the passing rate of the nail penetration test of the battery monomers is statistically calculated.

[0143] Table 1 below shows the separator film parameters and the secondary battery performance test results of Examples 1-4 and Comparative Examples 1-3.

[0144] Table 1:

[0145]

[0146] It can be seen from Table 1 that compared with Comparative Example 1 (only the first coating is provided), Comparative Example 2 (only the second coating is provided), and Comparative Example 3 (the first coating is not in contact with the base film), by setting the first coating in contact with the base film and setting the second coating in Examples 1 to 4, the passing rate of the nail penetration test of the secondary battery can be significantly improved, that is, the safety performance of the secondary battery is significantly improved.

[0147] Examples 5-7

[0148] The secondary battery is assembled in the same manner as in Example 4, except that the thicknesses of the first coating and the second coating in the separator film used are different. For details, please refer to Table 2 below.

[0149] Table 2 below shows the separator film parameters and the secondary battery performance test results of Examples 5-7. In addition, for the convenience of comparison, the data in Example 4 are also shown here.

[0150] Table 2:

[0151]

[0152] As can be seen from Table 2, when the thickness of the first coating is 0.5 μm to 1.5 μm and the thickness of the second coating is 0.5 μm to 1.5 μm, it is beneficial to balance the safety performance and power performance of the secondary battery.

[0153] It should be noted that this application is not limited to the above embodiments. The above embodiments are only examples, and embodiments having the same structure in essence as the technical idea and achieving the same effects within the technical scope of this application are all included in the technical scope of this application. In addition, within the scope of not departing from the gist of this application, various modifications that can be conceived by those skilled in the art to the embodiments and other ways constructed by combining some of the constituent elements of the embodiments are also included in the scope of this application.

Claims

1. A separator membrane, characterized in that, Comprising: A base film, a first coating, and a second coating; The first coating is disposed on one side of the base film, and the second coating is disposed on one side of the first coating in the composite film layer composed of the base film and the first coating; or, The first coating is disposed on one side of the base film, and the second coating is disposed on both sides of the composite film layer composed of the base film and the first coating; or, The first coating is disposed on both sides of the base film, and the second coating is disposed on at least one side of the composite film layer composed of the base film and the first coating; The first coating includes heat-resistant particles; the second coating includes a coolant.

2. The separator membrane according to claim 1, wherein The thickness of the first coating is 0.5 μm to 1.5 μm.

3. The separator film according to claim 1 or 2, characterized in that, The heat-resistant particles include inorganic materials.

4. The separator film according to claim 3, characterized in that, The inorganic materials include one of boehmite, aluminum oxide, silicon dioxide, zirconium oxide, and titanium dioxide.

5. The separator film according to any one of claims 1 to 4, characterized in that, The thickness of the second coating is 0.5 μm to 1.5 μm.

6. The separator film according to any one of claims 1 to 5, characterized in that, The coolant includes a housing and a coolant located inside the housing; the boiling point of the coolant is less than the boiling point of the housing.

7. The separator film according to claim 6, wherein The coolant includes one of heptafluorocyclopentane, bromotrifluoropropene, 1,2-dibromo-1,1,2,2-tetrafluoroethane, 1,1-dichloro-1,2,2-trifluoroethane, and dibromomethane.

8. The separator film according to claim 6 or 7, characterized in that, The material of the housing includes one of polyamide, urea-formaldehyde resin, amino resin, epoxy resin, and alkyd resin.

9. The separator film according to any one of claims 1 to 8, characterized in that, The particle size of the coolant is 0.5 to 5 μm.

10. The separator film according to any one of claims 1 to 9, characterized in that, The first coating is disposed on both sides of the base film, and the second coating is disposed on both sides of the composite film layer.

11. The separator film according to any one of claims 1 to 10, characterized in that, The thickness of the base film is 5 μm to 9 μm.

12. The separator film according to any one of claims 1 to 11, characterized in that, The material of the base film includes one of polyolefin, polyether, polyether ether ketone, polyimide, polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polyvinylidene chloride, polyethylene-propylene copolymer, and copolymer containing carbon-fluorine bond.

13. A secondary battery, characterized in that, Including the separator film according to any one of claims 1 to 12.

14. An electrical device, characterized in that, Including the secondary battery according to claim 13.

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