Isolation film, secondary battery containing the same, and electrical device

Abstract

The present application provides an isolation film, comprising a substrate; a coating, wherein the coating comprises an organic-inorganic hybrid layered silicate; the organic part of the layered silicate comprises one or more of alkylammonium, quaternary ammonium salt, octadecylamine and organosilicon; the inorganic part of the layered silicate comprises a compound shown in Formula 1, M 2 (Al 2‑x Mg x )[Si 4 O 10 ](OH) 2 Formula 1, in which M includes one or more of Na, Li, K, and Ca, and X is 0-2.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to an isolation membrane, a secondary battery containing the isolation membrane, and an electrical device. Background Art

[0002] In recent years, the application scope of secondary batteries has become increasingly wide. They are widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.

[0003] The safety performance of secondary batteries has always been highly valued in the industry. Therefore, how to improve the safety performance of batteries remains an urgent problem to be solved. Summary of the invention

[0004] In order to achieve the above-mentioned object, the first aspect of the present application provides an isolation film, comprising: a substrate; a coating, wherein the coating comprises an organic-inorganic hybrid layered silicate; the organic part of the layered silicate comprises one or more of alkylammonium, quaternary ammonium salt, octadecylamine and organosilicon; the inorganic part of the layered silicate comprises a compound represented by formula 1, M2(Al 2-x Mg x )[Si4O 10 ](OH)2 Formula 1, in which M includes one or more of Na, Li, K, and Ca, and X has a value of 0-2.

[0005] Therefore, the present application adds layered silicate with a specific structure into the isolation film coating slurry, swells and disperses it into a colloid in a solvent, and at the same time, after drying, the layered silicate can adhere to the surface of the isolation film, thereby enhancing the mechanical strength of the isolation film.

[0006] In any embodiment, the organic part of the layered silicate includes one or more of the compounds represented by Formula 2A or Formula 2B;

[0007]

[0008] In Formula 2A, R 11 -R 14 At least three of them are independently selected from C1-C 25 The alkyl group;

[0009] In Formula 2B, R 21 Selected from C1-C 25 of alkyl.

[0010] In any embodiment, R 11 -R 14 At least one of the following is selected from C 10 -C 25and / or, R 21 Selected from C 10 -C 25 of alkyl.

[0011] In any embodiment, the mass proportion of the layered silicate in the coating is 50%-80%, and optionally 60%-70%.

[0012] In any embodiment, the thickness of the coating is less than or equal to 3 μm; optionally, it can be 0.5 μm-3 μm.

[0013] In any embodiment, the longitudinal tensile strength of the separator is 3000 kgf / cm 2 -3500kgf / cm 2 .

[0014] In any embodiment, the longitudinal heat shrinkage of the separator at 150° C. is 3.5% to 5%.

[0015] The second aspect of the present application also provides a method for preparing an isolation film, which comprises the following steps:

[0016] Step S1: providing a substrate;

[0017] Step S2: providing a slurry, the slurry comprising an organic-inorganic hybrid layered silicate; the organic part of the layered silicate comprises one or more of alkylammonium, quaternary ammonium salt, octadecylamine and organosilicon; the inorganic part of the layered silicate comprises a compound represented by Formula 1, M2 (Al 2-x Mg x )[Si4O 10 ](OH)2 Formula 1, in which M includes one or more of Na, Li, K, and Ca, and X is 0-2;

[0018] Step S3: coating the slurry on at least one surface of the substrate to form a coating.

[0019] Layered silicates are composed of a composite of an organic part and an inorganic part, and optionally, the organic part is intercalated or exfoliated between layers of the inorganic part.

[0020] Therefore, in the isolation membrane prepared by the method of the present application, layered silicate is added to the coating slurry to play a role in dispersion and thickening. At the same time, after drying, the layered silicate can adhere to the surface of the isolation membrane to enhance the mechanical strength of the isolation membrane.

[0021] A third aspect of the present application provides a secondary battery, comprising the isolation membrane of the first aspect of the present application or the isolation membrane prepared according to the method of the second aspect of the present application.

[0022] A fourth aspect of the present application provides a battery module, comprising the secondary battery of the third aspect of the present application.

[0023] A fifth aspect of the present application provides a battery pack comprising the battery module of the fourth aspect of the present application.

[0024] The sixth aspect of the present application provides an electrical device comprising at least one selected from the secondary battery of the third aspect of the present application, the battery module of the fourth aspect of the present application, or the battery pack of the fifth aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a schematic diagram of a secondary battery according to one embodiment of the present application.

[0026] Figure 2 yes Figure 1 An exploded view of a secondary battery according to an embodiment of the present application is shown.

[0027] Figure 3 is a schematic diagram of a battery module according to an embodiment of the present application.

[0028] Figure 4 It is a schematic diagram of a battery pack according to one embodiment of the present application.

[0029] Figure 5 yes Figure 4 An exploded view of a battery pack according to an embodiment of the present application is shown.

[0030] Figure 6 FIG. 1 is a schematic diagram of an electric device using a secondary battery according to an embodiment of the present application as a power source.

[0031] Description of reference numerals:

[0032] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 secondary battery; 51 shell; 52 electrode assembly; 53 top cover assembly. DETAILED DESCRIPTION

[0033] Below, the embodiments of the separator, positive electrode sheet, negative electrode sheet, electrolyte, secondary battery, battery module, battery pack and power device of the present application are specifically disclosed with appropriate reference to the accompanying drawings. However, there are cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0034] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0035] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0036] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0037] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which 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 may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0038] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0039] If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0040] [Secondary battery]

[0041] Secondary batteries, also known as rechargeable batteries or storage batteries, refer to batteries that can be recharged to activate active materials and continue to be used after the battery is discharged. Usually, secondary batteries include positive electrode sheets, negative electrode sheets, separators and electrolytes. During the battery charging and discharging process, active ions (such as lithium ions) are embedded and released back and forth between the positive electrode sheets and the negative electrode sheets. The separator is arranged between the positive electrode sheets and the negative electrode sheets, and its main function is to prevent the positive and negative electrodes from short-circuiting, while allowing active ions to pass through. The electrolyte is between the positive electrode sheets and the negative electrode sheets, and its main function is to conduct active ions.

[0042] [Isolation film]

[0043] One embodiment of the present application provides an isolation film, comprising: a substrate; a coating, wherein the coating comprises an organic-inorganic hybrid layered silicate; the organic part of the layered silicate comprises one or more of alkylammonium, quaternary ammonium salt, octadecylamine and organosilicon; the inorganic part of the layered silicate comprises a compound represented by formula 1, M2(Al 2-x Mg x )[Si4O 10 ](OH)2 Formula 1, in which M includes one or more of Na, Li, K, and Ca, and X has a value of 0-2.

[0044] The present application has no particular limitation on the type of substrate, and any known porous structure substrate with good chemical stability and mechanical stability can be selected.

[0045] In some embodiments, the substrate may be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride.

[0046] The present invention adds a layered inorganic substance of a specific composition to the separator coating slurry, wherein the chain-like organic substance is intercalated or peeled between the inorganic sheets to achieve compounding. The obtained separator coating can not only enhance the mechanical properties of the separator, but also has good dispersibility and is easy to coat. The secondary battery containing the separator coating has the characteristics of high safety, high capacity and long life.

[0047] In some embodiments, the organic portion of the organic-inorganic hybrid material includes one or more of the compounds shown in Formula 2A or Formula 2B,

[0048]

[0049] In Formula 2A, R 11 -R 14 At least three of them are independently selected from C1-C 25 The alkyl group;

[0050] In Formula 2B, R 21 Selected from C1-C 25 of alkyl.

[0051] Organic-inorganic hybrids are well known in the art, and are generally composite materials of inorganic and organic materials bonded at the nanoscale by intermolecular forces, hydrogen bonds or covalent bonds. The various materials complement each other in terms of performance, produce synergistic effects, and form materials with new properties on a macro scale. Common methods include sol-gel methods, etc. For example, the inorganic part of the present application (e.g., Na 0.5 (Al 1.5 Mg 0.5 )[Si4O 10 ](OH)2) can be modified on the surface of the organic part (such as organic ammonium salt), and is made by high-speed stirring at a certain temperature in a dispersion medium containing an initiator and an antioxidant, and then drying and crushing the medium after distillation to remove the medium.

[0052] In some embodiments, R 11 -R 14 At least one of the following is selected from C 10 -C 25 and / or, said R 21 Selected from C 10 -C 25 of alkyl.

[0053] The longer molecular chain of the organic part is conducive to the exfoliation of layered silicates on a microscopic scale, and is easy to prepare in a composite when modifying silicates. The layered silicate structure formed is highly stable. It has a high affinity for organic solvent systems. At the same time, the organic matter itself acts as a surfactant, and the organically modified silicate formed after compounding with silicates can have a better dispersion effect in the preparation process of the coating slurry.

[0054] In some embodiments, the mass proportion of the layered silicate in the coating is 50%-80%, and can be 60%-70%. The mass proportion of the layered silicate will affect the physical properties of the separator and the bonding stability of the coating. When the content is controlled within this range, it can ensure a large bonding force and a good coating effect, and at the same time, the strength of the separator is high, which has a better effect on enhancing the safety performance of the secondary battery.

[0055] In some embodiments, the thickness of the coating is less than or equal to 3 μm, and can be optionally 0.5 μm-3 μm. When the thickness of the isolation film coating meets this range, the isolation film has a more obvious effect of enhancing safety performance, while the increase in the internal resistance of the battery cell is small, and the impact on the initial efficiency is small.

[0056] In some embodiments, the longitudinal tensile strength is 3000 kgf / cm 2 -3500kgf / cm 2 .

[0057] In some embodiments, the heat shrinkage rate in the longitudinal direction at 150° C. is 3.5% to 5%.

[0058] [Isolation film preparation method]

[0059] One embodiment of the present application provides a method for preparing an isolation film, which comprises the following steps:

[0060] Step S1: providing a substrate;

[0061] Step S2: providing a slurry, wherein the slurry includes a layered silicate, and the layered silicate includes an organic-inorganic hybrid material with the layered silicate as a main body;

[0062] The organic matter is one or more of alkylammonium, quaternary ammonium salt, octadecylamine and organosilicon;

[0063] The general formula of layered silicate is shown in Formula 1,

[0064] M x (Al 2-x Mg x )[Si4O 10 ](OH)2 Formula 1,

[0065] In Formula 1, M includes one or more of Na, Li, and K, and X is 0-2;

[0066] Step S3: coating the slurry on at least one surface of the substrate to obtain an isolation film.

[0067] Layered silicates are composed of organic and inorganic parts. Optionally, organic matter is intercalated or exfoliated between the layered silicate sheets.

[0068] The coating slurry has the characteristics of simple composition, good dispersibility and high leveling property. At the same time, the slurry is easy to apply while ensuring that the types of materials are reduced as much as possible, and can adapt to various types of current coating methods. This type of material is easily soluble in hydrocarbon solvents. Adding a small amount of polar solvents such as methanol, ethanol, acetone, etc. can bridge the quaternary ammonium hydrocarbon chains between the layered silicate layers through hydrogen bonds to obtain effective solvation, thereby expanding and dispersing the layers, and forming a thixotropic gel with a card-layer structure to prevent the precipitation of inorganic fillers. The main purpose of using it in the coating slurry is to obtain a stable and easy-to-apply slurry, while realizing the film formation of silicate on the isolation membrane and enhancing the mechanical strength of the isolation membrane.

[0069] In some embodiments, the preparation method S2 further comprises the following steps:

[0070] The organic-inorganic hybrid material and the binder are mixed and stirred to obtain mixed solid phase particles; and an alcohol solvent is added to the mixed solid phase particles.

[0071] In some embodiments, the binder includes one or more of polyvinylidene fluoride, polyacrylic acid, and polyacrylate. The selection of the binder will affect the bonding effect of the coating on the surface of the isolation membrane, and polyvinylidene fluoride has a better dispersion effect in the organic slurry.

[0072] In some embodiments, the alcohol solvent includes one or more of methanol, ethanol, ethylene glycol, and propanol. The alcohol solvent plays a role in enhancing the dispersion effect of the slurry, among which ethanol is easier to disperse.

[0073] In some embodiments, the mass fraction ω1 of the layered silicate in the mixed solid phase particles is 50%-80%, and the mass fraction ω2 of the binder in the mixed solid phase particles is 20%-50%. Optionally, ω1 / ω2 satisfies 1≤ω1 / ω2≤4.

[0074] In some embodiments, the alcohol solvent accounts for 5%-20% of the total solvent by weight.

[0075] In some embodiments, the slurry includes a lithium supplement, optionally, one or more of lithium powder or lithium oxide. In some embodiments, the slurry coating method includes any one of transfer coating, spray coating, extrusion coating, gravure coating or blade coating, or a combination of at least two thereof.

[0076] [Positive electrode]

[0077] The positive electrode sheet generally includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes a positive electrode active material.

[0078] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0079] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may 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 (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0080] In some embodiments, the positive electrode active material may adopt a positive electrode active material for a battery that is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: a lithium-containing phosphate with an olivine structure, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries 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 LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05O2) and its modified compounds, etc. Examples of lithium-containing phosphates with an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to 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 iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0081] 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 fluorine-containing acrylate resin.

[0082] In some embodiments, the positive electrode film layer may further include a conductive agent, for 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.

[0083] In some embodiments, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0084] [Negative electrode]

[0085] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0086] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0087] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, a copper 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 substrate. The composite current collector may 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 (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0088] In some embodiments, the negative electrode active material may adopt the negative electrode active material for the battery 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, lithium titanate, etc. The silicon-based material may 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 may 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 traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0089] In some embodiments, the negative electrode film layer may further include a binder. As an example, 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).

[0090] In some embodiments, the negative electrode film layer may further include a conductive agent. As an example, 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.

[0091] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0092] In some embodiments, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0093] [Electrolytes]

[0094] The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or all-solid.

[0095] In some embodiments, the electrolyte is liquid and includes an electrolyte salt and a solvent.

[0096] In some embodiments, the electrolyte salt can 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 difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0097] In some embodiments, the solvent can 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, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0098] In some embodiments, the electrolyte may further include additives. As examples, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.

[0099] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

[0100] In some embodiments, the secondary battery may include an outer package, which may be used to encapsulate the electrode assembly and the electrolyte.

[0101] In some embodiments, the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0102] The present application has no particular limitation on the shape of the secondary battery, which may be cylindrical, square or any other shape. Figure 1 The secondary battery 5 is a square structure as an example.

[0103] In some embodiments, reference Figure 2 , the outer packaging may include a shell 51 and a cover plate 53. Among them, the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0104] In some embodiments, secondary batteries may be assembled into a battery module. The number of secondary batteries contained in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.

[0105] Figure 3 4 is an example of a battery module. Figure 3 In the battery module 4, the plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of secondary batteries 5 may be fixed by fasteners.

[0106] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of secondary batteries 5 are received in the receiving space.

[0107] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

[0108] Figure 4 and Figure 5 1 is a battery pack 1 as an example. Figure 4 and Figure 5 The battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. 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.

[0109] In addition, the present application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.

[0110] As the electrical device, a secondary battery, a battery module or a battery pack may be selected according to its usage requirements.

[0111] Figure 6The power consumption device is taken as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the high power and high energy density requirements of the power consumption device for the secondary battery, a battery pack or a battery module can be used.

[0112] [Example]

[0113] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0114] Example 1

[0115] Preparation of positive electrode

[0116] The positive electrode active material NCM523, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) are dissolved in the solvent N-methylpyrrolidone (NMP) in a weight ratio of 96.5:1.5:2, and the positive electrode slurry is obtained after being fully stirred and mixed; then the positive electrode slurry is evenly coated on the positive electrode collector, and then dried, cold pressed, and cut to obtain the positive electrode sheet.

[0117] Preparation of negative electrode

[0118] The active material artificial graphite, the conductive agent acetylene black, the binder styrene-butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC) are dissolved in the solvent deionized water at a weight ratio of 95:2:2:1 and evenly mixed with the solvent deionized water to prepare a negative electrode slurry; then the negative electrode slurry is evenly coated on the negative electrode current collector copper foil, and the negative electrode film is obtained after drying, and then the negative electrode sheet is obtained by cold pressing and slitting.

[0119] Isolation film

[0120] Slurry preparation: Na 0.5 (Al 1.5 Mg 0.5 )[Si4O 10 ](OH)2 and octadecyltrimethylammonium bromide are compounded by a sol-gel method, and the layered silicate and the binder polyvinylidene fluoride are dry-mixed in a ratio of 40:60 to obtain mixed solid phase particles; the mixed solid phase particles are added to N-methylpyrrolidone, and 8% ethanol is added as a solvent, and the mixture is fully stirred in a stirring tank; the atmosphere of the stirring tank is adjusted to a nitrogen atmosphere, and the slurry is obtained after continuing to stir;

[0121] Preparation of isolation film: PE substrate was used and gravure coating was used to apply the above slurry on both sides of the substrate to form a coating. The thickness of the single-sided coating was 2 μm.

[0122] Preparation of electrolyte

[0123] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1, and then LiPF6 is uniformly dissolved in the above solution to obtain an electrolyte. In the electrolyte, the concentration of LiPF6 is 1 mol / L.

[0124] Preparation of secondary batteries

[0125] The positive electrode sheet, separator, and negative electrode sheet are stacked and wound in order to obtain an electrode assembly; the electrode assembly is placed in an outer package, and the prepared electrolyte is added. After packaging, standing, forming, aging and other processes, a secondary battery is obtained.

[0126] The secondary battery preparation methods of Examples 2-12 and Comparative Examples 1-4 are similar to those of Example 1, but the composition and product parameters of the layered silicate are adjusted. The different preparation parameters are detailed in Table 1.

[0127] Table 1: Preparation parameters of Examples 1-12 and Comparative Examples 1-3

[0128]

[0129] Isolation film test

[0130] (1) Coating material testing

[0131] The materials used in the coating can be distinguished by simple physical property characterization, including conventional material analysis methods such as XRD crystal form confirmation, ICP elemental analysis and infrared organic functional group confirmation.

[0132] (2) Puncture strength test

[0133] 1) Test equipment: High-speed rail servo-controlled desktop tensile testing machine (AI-3000); Test environment: room temperature, relative humidity 45%-55%.

[0134] 2) Ensure that the sample isolation film has no defects on its surface, and use scissors to cut the isolation film into strips, wherein the width of the strip isolation film is greater than 100 mm.

[0135] 3) Install a test piece with a width of 100 mm on the sample film fixing clamp ring, and then use a steel needle with a diameter of 1.0 mm and a top radius of 0.5 mm to puncture it at a speed of (50±5) mm / min. Read the maximum load of the steel needle penetrating the test piece as the puncture strength of the sample isolation membrane.

[0136] (3) Tensile strength test

[0137] 1) Test equipment: High-speed rail servo-controlled desktop tensile testing machine (AI-3000); Test environment: room temperature, relative humidity 45%-55%.

[0138] 2) Make sure that the sample isolation film has no defects on its surface and cut the isolation film into strips of 100 mm x 15 mm using scissors.

[0139] 3) Use a tensile testing machine to fix the isolation membrane and stretch it along the length direction of the sample isolation membrane until it breaks. The maximum load is recorded as the tensile strength of the isolation membrane.

[0140] (4) Thermal shrinkage test

[0141] 1) Test equipment: high temperature oven; test environment: relative humidity 45%-55%.

[0142] 2) Ensure that the surface of the sample isolation film is flawless, cut the isolation film into 10 cm × 10 cm square pieces with scissors, clamp them between two glass plates and put them into the oven.

[0143] 3) Heat the oven to 150°C at a rate of 5°C / min and keep warm for 1 hour.

[0144] 4) Take out the isolation film and measure the length and width shrinkage of the isolation film after cooling. The ratio of the length shrinkage to the value before heating is the thermal shrinkage rate.

[0145] Battery Test

[0146] (1) DC resistance test

[0147] The test was carried out at room temperature 25°C.

[0148] 1) Charge the cell to the nominal voltage at 1 / 3C (nominal capacity), then charge at constant voltage until the current is ≤ 0.05C, and record the capacity as 100% SOC; leave for 5 minutes.

[0149] 2) Discharge the battery to 50% SOC at a constant current of 1 / 3C rate. After the adjustment is completed, test the voltage of the secondary battery and record it as V1.

[0150] 3) Discharge continuously at a constant current of 4C rate (corresponding to current I) for 10 seconds. After the discharge, test the voltage of the lithium-ion battery and record it as V2.

[0151] 4) Use the formula to calculate the DC resistance R: R = (V1-V2) / I.

[0152] (2) Secondary battery thermal failure temperature test

[0153] 1) After the battery cell is fully charged to the nominal voltage, a temperature sensing wire is installed and the battery cell is placed in a heating furnace.

[0154] 2) Heat at a rate of 5°C / min until the battery cell catches fire and fails.

[0155] 3) Record the furnace temperature at the time of failure as the thermal failure temperature of the battery cell.

[0156] Table 2: Performance test results of Examples 1-12 and Comparative Examples 1-3

[0157]

[0158] According to the above results, Examples 1-12 added layered silicate to the isolation membrane coating, which achieved good results in terms of isolation membrane performance. The isolation membrane had high puncture strength and tensile strength while having a small thermal shrinkage rate. In terms of battery performance, while increasing the thermal failure temperature, it also had a small DC resistance, thereby enhancing the safety performance of the battery.

[0159] In contrast, in Comparative Examples 1-3, the isolation membrane strength and puncture strength are poor and the heat shrinkage rate is high, and the overall performance of the isolation membrane is poor; in terms of battery performance, the DC resistance is high and the thermal failure temperature is low, and the safety performance is poor.

[0160] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for preparing an isolation film, wherein: The steps include: Step S1: providing a substrate; Step S2: providing a slurry, wherein the slurry comprises an organic-inorganic hybrid layered silicate and an alcohol solvent; The organic part in the layered silicate includes one or more of alkylammonium, quaternary ammonium salt, octadecylamine and organosilicon; The inorganic part of the layered silicate comprises a compound represented by Formula 1, M2(Al 2-x Mg x )[Si4O 10 (OH)2 formula 1, In Formula 1, M includes one or more of Na, Li, K, and Ca, and X is 0-2; Step S3: coating the slurry on at least one surface of the substrate to form a coating, wherein the coating includes the organic-inorganic hybrid layered silicate; The mass fraction ω1 of the layered silicate in the coating is 50%-80%.

2. The preparation method according to claim 1, wherein The step S2 further comprises: The layered silicate and the binder are mixed and stirred to obtain mixed solid phase particles; a solvent is added to the mixed solid phase particles, and the solvent includes the alcohol solvent.

3. The preparation method according to claim 2, wherein The binder includes one or more of polyvinylidene fluoride, polyacrylic acid, and polyacrylate.

4. The preparation method according to any one of claims 1 to 3, wherein The alcohol solvent includes one or more of methanol, ethanol, ethylene glycol and propanol.

5. The preparation method according to claim 4, wherein The mass fraction ω1 of the layered silicate in the coating is 60%-70%.

6. The preparation method according to claim 2 or 3, wherein: The mass fraction ω2 of the binder in the coating is 20%-50%.

7. The preparation method according to claim 6, wherein: 1≤ω1 / ω2≤4; ω1 is the mass fraction of the layered silicate in the coating; ω2 is the mass fraction of the binder in the coating.

8. The preparation method according to claim 2 or 3, wherein: The alcohol solvent accounts for 5%-20% by mass of the solvent.

9. The preparation method according to claim 1, wherein The organic part of the layered silicate includes one or more of the compounds shown in Formula 2A or Formula 2B, In Formula 2A, R 11 -R 14 At least three of them are independently selected from C1-C 25 The alkyl group; In Formula 2B, R 21 Selected from C1-C 25 of alkyl.

10. The preparation method according to claim 9, wherein: The R 11 -R 14 At least one of C 10 -C 25 and / or, said R 21 Selected from C 10 -C 25 of alkyl.

11. The preparation method according to claim 1, wherein: The thickness of the coating is less than or equal to 3 μm.

12. The preparation method according to claim 11, wherein The coating has a thickness of 0.5 μm-3 μm.

13. The preparation method according to claim 1, wherein: The longitudinal tensile strength of the isolation film is 3000 kgf / cm 2 -3500kgf / cm 2 .

14. The preparation method according to claim 1, wherein: The longitudinal heat shrinkage rate of the isolation film at 150° C. is 3.5%-5%.

15. A secondary battery comprising a separator prepared by the method according to any one of claims 1 to 14.

16. An electrical device comprising the secondary battery according to claim 15.

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