Battery isolating membrane and preparation method thereof, battery monomer, battery and electric equipment

Abstract

The invention discloses a battery isolating membrane and a preparation method thereof, a battery monomer, a battery and electric equipment, the battery isolating membrane comprises a base membrane and a thermal protection layer, the thermal protection layer is arranged on at least one side of the base membrane, and the thermal protection layer comprises an organic thermal expansion material and inorganic particles. The thermal protection layer is arranged on at least one side of the base membrane, when abnormal temperature rise occurs in the battery monomer, the organic thermal expansion material is heated to generate volume expansion, the expanded material can block holes of the base membrane and hinder migration of active ions, thermal runaway of the battery monomer at a high temperature is reduced, and the service life of the battery monomer is prolonged. And the safe use performance of the battery monomer is improved. And the inorganic particles can reduce the condition of shrinkage of the battery isolating membrane caused by thermal stress and the condition of short circuit caused by direct contact of the positive electrode and the negative electrode due to size shrinkage of the battery isolating membrane, so that the safe use performance of the battery monomer is further improved.

Description

Technical Field

[0001] The present invention relates to the field of batteries, and in particular to a battery separator and a preparation method thereof, a battery cell, a battery, and electrical equipment. Background Art

[0002] This section merely provides background information related to the present application and is not necessarily prior art.

[0003] As a new generation of green energy storage and conversion devices, batteries have been widely used in portable electronic devices, power vehicles and other fields. With the rapid development of battery technology, the research and development of power batteries with high power output and fast charging and discharging has become a development trend, which also puts higher requirements on the safety performance of batteries. The safety performance of batteries is related to the thermal runaway of batteries caused by abnormal internal temperature rise. Among them, the isolation membrane is an important component of the battery cell. When the temperature inside the battery rises abnormally, it is easy to shrink or melt due to heat, which further aggravates the occurrence of thermal runaway of the battery. Therefore, improving the thermal stability and safety performance of the isolation membrane is particularly important for improving the safety performance of the battery. Summary of the invention

[0004] The main technical problem solved by this application is to improve the safety performance of the battery.

[0005] In a first aspect, an embodiment of the present application provides a battery isolation film, comprising: Basement membrane; The heat protection layer is arranged on at least one side of the base film, and comprises an organic thermal expansion material and inorganic particles.

[0006] In the embodiment of the present application, a heat protection layer is provided on at least one side of the base film, and the heat protection layer includes an organic heat expansion material and inorganic particles; when the temperature inside the battery cell rises abnormally, the organic heat expansion material can expand in volume when heated, and the expanded material can block the pores of the base film, reduce the pore size for the free migration of active ions, hinder the migration of active ions, and quickly reduce the migration of current between the positive and negative electrodes, reduce the thermal runaway of the battery cell at high temperature, reduce the deterioration of life characteristics, and improve the safe use performance of the battery cell. In addition, the inorganic particles have a high tolerance temperature, and still have good dimensional temperature properties when heated within the melting point range. In the case of abnormal temperature rise inside the battery cell, the inorganic particles can reduce the shrinkage of the battery separator caused by thermal stress, reduce the short circuit caused by direct contact between the positive and negative electrodes due to the shrinkage of the battery separator size, improve the thermal stability of the battery cell, and further improve the safe use performance of the battery cell.

[0007] In some embodiments, the weight ratio of the organic thermal expansion material to the inorganic particles is 1:0.5-1:5.

[0008] In any embodiment, the weight ratio of the organic thermal expansion material to the inorganic particles can be 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2, 1:2.1, 1:2.2, 1:2.3, 1:2.4, 1:2.5, 1:2.6, 1:2.7, 1:2.8, 1:2.9, 1:3, 1:3.1, 1:3.2, 1:3.3, 1:3.4, 1:3.5, 1:3.6, 1:3.7, 1:3.8, 1:3.9, 1:4, 1:4.1, 1:4.2, 1:4.3, 1:4.4, 1:4.5, 1:4.6, 1:4.7, 1:4.8, 1:4.9, 1:5, or a range consisting of any two of the above values. For example, the weight ratio of the organic thermal expansion material to the inorganic particles can be 1:0.5-1.5, 1:1.5-3, or 1:4-5. The weight ratio of the organic thermal expansion material to the inorganic particles is 1:0.5-1:5. On the one hand, it can expand due to heat and hinder the migration of active ions, reducing the thermal runaway of the battery monomer at high temperature. On the other hand, it can improve the thermal stability of the battery monomer to reduce the shrinkage problem of the battery isolation film 2310 caused by thermal stress.

[0009] In some embodiments, the heat protection layer is a single layer structure in which an organic heat expandable material and inorganic particles are mixed.

[0010] Among them, inorganic particles are distributed in the organic thermal expansion material, and the two are mixed to form a single-layer structure. The setting of the single-layer structure is conducive to reducing the thickness of the thermal protection layer, reducing the internal resistance of the battery isolation membrane, and increasing the internal current of the battery cell. In addition, the setting of the single-layer structure allows the thermal protection layer to be formed in one step, which is conducive to simplifying the process of the thermal protection layer and reducing the difficulty of the process.

[0011] In some embodiments, the heat protection layer includes an inorganic particle layer and a heat expansion layer which are stacked, the inorganic particle layer is closer to the base film than the heat expansion layer, and the heat expansion layer includes an organic heat expansion material.

[0012] Among them, the organic thermal expansion material and the inorganic particles are arranged in layers, the film layer where the inorganic particles are located is closer to the base film, and the film layer where the organic thermal expansion material is located is arranged on the side of the film layer where the inorganic particles are located away from the base film. When the temperature inside the battery cell rises abnormally, the film layer where the organic thermal expansion material is located is first exposed to heat, and in a relatively short period of time, the film layer material can be expanded by heat, the pores of the base film can be blocked, and the migration of active ions can be hindered. At the same time, the inorganic particle layer close to the base film can block heat transfer, further protecting the isolation membrane from thermal breakdown.

[0013] In some embodiments, the heat transition temperature of the organic thermally expandable material is in the range of 110°C to 130°C.

[0014] The thermal transition temperature of the organic thermal expansion material refers to the starting temperature at which the volume expansion of the organic thermal expansion material occurs when heated. The starting temperature has a direct impact on the protective effect of the thermal protection layer. For example, if the starting temperature is low, the volume expansion of the organic thermal expansion material occurs at a lower temperature, so that the base film has blocked pores at a lower temperature. The battery cell can hinder the migration of current at a lower temperature, which is beneficial to reduce the thermal runaway of the battery cell and improve the safety performance of the battery cell. On the contrary, if the starting temperature is high, it is not conducive to controlling the thermal runaway of the battery cell.

[0015] In some embodiments, the organic thermal expansion material includes one or more of polyamide, polyvinyl chloride, polyoxymethylene, polycarbonate, polyvinylidene chloride, and polymethyl methacrylate.

[0016] The organic thermal expansion material can be one of the above materials or a combination of the above materials. The selection of the above materials can make the organic thermal expansion material have a suitable thermal transition temperature and expand in volume when heated, so that the thermal protection layer can protect the base film at a lower temperature, which is conducive to making the battery monomer have good safety performance.

[0017] In some embodiments, the organic thermal expansion material includes one or more of polyamide, polyvinyl chloride, and polymethyl methacrylate; optionally, there are at least two organic thermal expansion materials, and the mass ratio of the two organic thermal expansion materials is (0.3-5):(0.3-5).

[0018] The organic thermal expansion material can be one of the above materials or a combination of the above materials. The selection of the above materials enables the thermal protection layer to play a good protective role on the base film, which is beneficial to improving the safety performance of the battery cell.

[0019] In some embodiments, the volume average particle size Dv of the inorganic particles is 50 It is 10nm-30nm, and can be optionally 10nm-20nm.

[0020] In any embodiment, the volume average particle size of the inorganic particles can be 10nm, 15nm, 20nm, 25nm, 30nm, or a range consisting of any two of the above values. For example, the volume average particle size of the inorganic particles can be 10nm-20nm, 15nm-25nm or 20nm-30nm, etc. The volume average particle size of the inorganic particles within the above range is conducive to improving the dispersion of the inorganic particles in the thermal protection layer, blocking the pores of the base film, and reducing the thickness of the thermal protection layer.

[0021] In some embodiments, the inorganic particles include one or more of SiO2, TiO2, Al2O3, CaCO3, ZrO2, MgO, ThO2, BeO, Mg2SiO4, MgSiO3, MgAl2O4, BeAl2O4, and AlN.

[0022] The inorganic particles may be one of the above materials or a combination of the above materials. The selection of the above materials can make the inorganic particles have good dimensional stability for the base film, which is beneficial to improving the safety performance of the battery cell.

[0023] In some embodiments, the thickness of the thermal protection layer is 2 μm-8 μm, and optionally 3 μm-5 μm.

[0024] Among them, the thermal protection layer needs to have a certain thickness to achieve the thermal protection effect on the base film. In addition, the thickness needs to be within a certain range to reduce the impact of the introduction of the thermal protection layer on the internal resistance of the battery isolation membrane. In any embodiment, the thickness of the thermal protection layer 2312 can be 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, or a range composed of any two of the above values. For example, the thickness of the thermal protection layer 2312 can be 2μm-4μm, 3μm-5μm or 6μm-8μm, etc. Within the above range, a smaller thickness makes the thermal protection layer have less impact on the internal resistance of the battery isolation membrane, and a larger thickness is conducive to improving the thermal protection effect of the thermal protection layer on the base film.

[0025] In some embodiments, the heat protection layer includes an inorganic particle layer and a heat expansion layer which are stacked, and the thickness of the inorganic particle layer is 3 μm-5 μm, and can be 3.5 μm-4.5 μm.

[0026] Among them, the inorganic particle layer needs to have a certain thickness to achieve its role in improving the dimensional stability of the base film. In addition, the thickness needs to be within a certain range to reduce the impact of the introduction of the inorganic particle layer on the internal resistance of the battery separator. In any embodiment, the thickness of the inorganic particle layer can be 3μm, 3.5μm, 4μm, 4.5μm, 5μm, or a range consisting of any two of the above values. For example, the thickness of the inorganic particle layer can be 3μm-4μm, 3.5μm-4.5μm, 4μm-5μm, etc. Within the above range, a smaller thickness makes the inorganic particle layer have less impact on the internal resistance of the battery separator, and a larger thickness is conducive to improving the effect of the inorganic particle layer on the dimensional stability of the base film.

[0027] In some embodiments, the thermal protection layer further includes a binder, and the binder includes one or more of polyvinylidene fluoride, polyurethane, polyacrylate, polyacrylamide, and cyclodextrin; the mass proportion of the binder in the thermal protection layer is 0.5%-2%.

[0028] The binder is used to bond the inorganic particles and / or the organic thermal expansion material. The binder can be one of the above materials or a combination of the above materials. The selection of the above materials can bond the inorganic particles and the organic thermal expansion material together to form a thermal protection layer, and the thermal protection layer can be bonded to at least one side of the base film.

[0029] In some embodiments, the battery separator further comprises a bonding layer disposed on at least one side of the base film; Optionally, the adhesive layer is disposed on a side of the heat protection layer away from the base film; Optionally, the thickness of the bonding layer is 5 μm-15 μm; Optionally, the adhesive layer includes one or more of polyvinylidene fluoride, polyurethane, polyacrylate, polyacrylamide, and cyclodextrin.

[0030] Among them, the bonding layer allows the battery separator to be arranged between the positive and negative electrodes, and to bond with the positive and negative electrodes respectively, thereby improving the shaping effect of the battery cell and reducing the fluffy phenomenon between the layers of the battery cell. The bonding layer is arranged on the side of the thermal protection layer away from the base film. In some embodiments, the bonding layer is arranged on the surface of the thermal protection layer away from the base film. In any embodiment, the thickness of the bonding layer can be 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, or a range composed of any two of the above values. For example, the thickness of the bonding layer can be 5μm-8μm, 7μm-10μm or 11μm-15μm, etc. The thickness of the bonding layer is within the above range, which can improve the shaping effect of the battery cell, reduce the fluffy phenomenon between the layers of the battery cell, and control its influence on the internal resistance of the battery separator within a controllable range. The bonding layer can be one of the above materials or a combination of the above materials. The selection of the above materials enables the adhesive layer to improve the shaping effect of the battery monomer, reduce the fluffy phenomenon between the layers of the battery monomer, and control its influence on the internal resistance of the battery separator within a controllable range.

[0031] In some embodiments, the battery isolation film further includes an isolation layer, which is closer to the base film than the thermal protection layer, and the isolation layer includes inorganic particles; optionally, the thickness of the isolation layer is 3 μm-5 μm, and optionally 3.5 μm-4.5 μm.

[0032] In any embodiment, the thickness of the isolation layer may be 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, or a range of any two of the above values, for example, the thickness of the isolation layer may be 3 μm-4 μm, 3.5 μm-4.5 μm, 4 μm-5 μm, etc. Within the above range, a smaller thickness makes the isolation layer have less influence on the internal resistance of the battery isolation film, and a larger thickness is conducive to improving the effect of the isolation layer on the dimensional stability of the base film.

[0033] In some embodiments, the porosity of the base film is 30%-70%, optionally 50%; the thickness of the base film is 5μm-10μm, optionally 6μm-8μm; the base film includes one or more of polyethylene, polypropylene, polyethylene terephthalate, polyvinyl alcohol, polyimide, polyamide, polyacrylonitrile, polyethylene oxide, polyvinyl chloride, polyvinylidene chloride, and polyvinylidene fluoride, optionally polyvinyl chloride and polyimide.

[0034] Among them, the base film needs to have a certain porosity to realize its function of realizing active ion migration, and the porosity needs to be within a certain range so that the base film has a certain mechanical strength. In any embodiment, the porosity of the base film can be 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or a range composed of any two of the above values, for example, the porosity of the base film can be 30%-40%, 45%-65% or 60%-70%, etc. Within the above range, a smaller porosity is conducive to the base film having a greater mechanical strength, and a larger porosity is conducive to the base film having a better level of active ion migration. The thickness of the base film needs to be within a certain range so that the internal resistance of the base film is in a smaller range. In any embodiment, the thickness of the base film can be 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, or a range composed of any two of the above values, for example, the thickness of the base film can be 6μm-8μm or 8μm-10μm, etc. Within the above range, a smaller thickness is conducive to reducing the internal resistance of the base film, and a larger thickness is conducive to improving the mechanical strength of the base film and the safety performance of the battery cell. The base film can be one of the above materials or a combination of the above materials. The selection of the above materials can make the base film have good ion migration performance and mechanical properties.

[0035] In a second aspect, an embodiment of the present application provides a method for preparing any battery separator provided in the first aspect, comprising: providing a basement membrane; A heat protection layer is formed on at least one side of the base film, the heat protection layer including an organic thermal expansion material and inorganic particles.

[0036] In the embodiments of the present application, a battery isolation membrane including a thermal protection layer is prepared to reduce thermal runaway of battery cells at high temperatures and improve the safe use performance of the battery cells.

[0037] In some embodiments, forming a thermal protection layer on at least one side of a base film comprises: Coating a precursor on at least one side of the base film; the precursor includes an organic thermal expansion material, inorganic particles and a solvent; The base film coated with the precursor is dried.

[0038] The embodiments of the present application enable the heat protection layer to be uniformly formed on at least one side of the base film by coating, which is beneficial for the heat protection layer to have good uniform distribution and performance stability.

[0039] In some embodiments, the process parameters of the drying treatment include: a drying temperature of 60°C-100°C, optionally 80°C-90°C; a drying time of 2h-24h, optionally 6h-12h.

[0040] Wherein, in any embodiment, the drying temperature can be 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, or a range consisting of any two of the above values, for example, the drying temperature can be 60°C-70°C, 70°C-80°C, 80°C-90°C, 90°C-100°C, etc. In any embodiment, the drying time can be 2h, 4h, 6h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h, 24h, or a range consisting of any two of the above values, for example, the drying time can be 2h-6h, 6h-12h, 12h-18h, 18h-24h, etc.

[0041] In some embodiments, the mass concentration of the organic thermal expansion material is 2%-25%; the weight ratio of the organic thermal expansion material to the inorganic particles is 1:0.5-1:5.

[0042] In any embodiment, the mass concentration of the organic thermal expansion material can be 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, or a range consisting of any two of the above values. For example, the mass concentration of the organic thermal expansion material can be 2%-10%, 5%-15% or 15%-25%, etc. In any embodiment, the weight ratio of the organic thermal expansion material to the inorganic particles may be 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2, 1:2.1, 1:2.2, 1:2.3, 1:2.4, 1:2.5, 1:2.6, 1:2.7, 1:2.8, 1:2.9, 1:3, 1:3. .1, 1:3.2, 1:3.3, 1:3.4, 1:3.5, 1:3.6, 1:3.7, 1:3.8, 1:3.9, 1:4, 1:4.1, 1:4.2, 1:4.3, 1:4.4, 1:4.5, 1:4.6, 1:4.7, 1:4.8, 1:4.9, 1:5, or a range consisting of any two of the above values. For example, the weight ratio of the organic thermal expansion material to the inorganic particles can be 1:0.5-1:1.5, 1:1.5-1:3 or 1:4-1:5, etc.

[0043] In a third aspect, an embodiment of the present application provides a battery cell, including: Positive electrode; Negative electrode; A battery separator, disposed between the positive electrode sheet and the negative electrode sheet; The battery separator includes any battery separator provided in the first aspect, or a battery separator prepared by any preparation method provided in the second aspect. When a battery cell adopts the given battery separator, the safety performance of the battery cell can be improved.

[0044] In a fourth aspect, an embodiment of the present application provides a battery, comprising the battery cell provided in the third aspect. When the battery adopts the given battery cell, the safety performance of the battery can be effectively improved.

[0045] In a fifth aspect, an embodiment of the present application provides an electric device, comprising the battery provided in the fourth aspect. When the electric device uses the given battery, it has at least the same advantages as the battery, and can improve the reliability of the electric device.

[0046] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0048] Figure 1 is a schematic diagram of an exploded structure of a battery according to one or more embodiments; Figure 2 is a schematic diagram of an exploded structure of a battery cell according to one or more embodiments; Figure 3 is a schematic structural diagram of a vehicle according to one or more embodiments; Figure 4 is a schematic structural diagram of a battery isolation membrane provided in an embodiment of the present application; Figure 5 is another structural schematic diagram of a battery isolation membrane provided by an embodiment of the present application; Figure 6 It is another structural schematic diagram of the battery isolation membrane provided in the embodiment of the present application.

[0049] Description of Figure Numbers: 1000-vehicle, 100-battery, 200-controller, 300-motor, 10-casing, 20-battery cell, 11-first part, 12-second part, 21-end cover, 22-shell, 23-electrode assembly, 21a-electrode terminal, 23a-ear, 2310-battery isolation film, 2311-base film, 2312-thermal protection layer, 2313-adhesive layer, 2314-isolation layer, 2312a-inorganic particle layer, 2312b-thermal expansion layer. DETAILED DESCRIPTION

[0050] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0051] The terms "first", "second" and "third" in this application are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Thus, the features defined as "first", "second" and "third" can explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined. All directional indications (such as up, down, left, right, front, back...) in the embodiments of this application are only used to explain the relative position relationship, movement, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication also changes accordingly. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally also includes steps or units that are not listed, or optionally also includes other steps or units inherent to these processes, methods, products or devices.

[0052] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0053] Secondary batteries may experience abnormal temperature rise when overcharged, impacted, or heated. Active ions migrate back and forth through the pores of the battery separator, and the internal current further worsens the abnormal temperature rise of the battery, exacerbating the thermal runaway of the battery cells at high temperatures. In addition, the battery separator is prone to shrinkage or melting after being heated, causing a short circuit between the charged positive and negative electrode materials, further out of control of the heat inside the battery, and prone to serious safety accidents such as fire or explosion. Therefore, it is particularly important to improve the thermal stability and safety performance of the separator to reduce the occurrence of safety accidents.

[0054] In order to solve the above technical problems, the embodiment of the present application provides a laminated structure isolation membrane, and a heat protection layer is formed on at least one side of the isolation membrane base membrane. The heat protection layer includes an organic heat expansion material and inorganic particles. The organic heat expansion material can expand in volume when heated. The expanded material can block the pores of the base membrane, reduce the pore size for the free migration of active ions, hinder the migration of active ions, and quickly reduce the migration of current between the positive and negative electrodes, reduce the thermal runaway of the battery cell at high temperature, reduce the deterioration of life characteristics, and improve the safe use performance of the battery cell. In addition, the inorganic particles have a high tolerance temperature and still have good dimensional temperature properties when heated within their melting point range. In the case of abnormal temperature rise inside the battery cell, the inorganic particles can reduce the shrinkage of the battery isolation membrane caused by thermal stress, reduce the short circuit caused by direct contact between the positive and negative electrodes due to the shrinkage of the battery isolation membrane size, improve the thermal stability of the battery cell, and further improve the safe use performance of the battery cell.

[0055] The technical solutions described in the embodiments of this application are applicable to battery separators and preparation methods, battery cells, batteries, and electrical equipment. The battery separators and preparation methods, battery cells, batteries, and electrical equipment disclosed in this application can be used in the field of lithium-ion secondary batteries, and can also be used in the field of sodium-ion secondary batteries, potassium-ion secondary batteries, etc., and can be specifically configured according to needs.

[0056] The present application is described in detail below with reference to the accompanying drawings and embodiments.

[0057] Please refer to Figure 1 , Figure 1 1 is a schematic diagram of the exploded structure of a battery according to one or more embodiments. The battery 100 includes a box body 10 and a battery cell 20, and the battery cell 20 is accommodated in the box body 10. Among them, the box body 10 is used to provide a storage space for the battery cell 20, and the box body 10 can adopt a variety of structures. In some embodiments, the box body 10 may include a first part 11 and a second part 12, and the first part 11 and the second part 12 cover each other, and the first part 11 and the second part 12 jointly define a storage space for accommodating the battery cell 20. The second part 12 may be a hollow structure with one end open, and the first part 11 may be a plate-like structure, and the first part 11 covers the open side of the second part 12, so that the first part 11 and the second part 12 jointly define a storage space; the first part 11 and the second part 12 may also be hollow structures with one side open, and the open side of the first part 11 covers the open side of the second part 12. Of course, the box body 10 formed by the first part 11 and the second part 12 may be in a variety of shapes, such as a cylinder, a cuboid, etc.

[0058] In the battery 100, there may be multiple battery cells 20, and the multiple battery cells 20 may be connected in series, in parallel, or in a mixed connection. A mixed connection means that the multiple battery cells 20 are both connected in series and in parallel. Multiple battery cells 20 may be directly connected in series, in parallel, or in a mixed connection, and then the whole formed by the multiple battery cells 20 is accommodated in the box 10; of course, the battery 100 may also be a battery module in which multiple battery cells 20 are first connected in series, in parallel, or in a mixed connection, and then the multiple battery modules are connected in series, in parallel, or in a mixed connection to form a whole, and accommodated in the box 10. The battery 100 may also include other structures. For example, the battery 100 may also include a confluence component for realizing electrical connection between multiple battery cells 20. Each battery cell 20 may be a secondary battery or a primary battery; it may be a sodium ion battery, but is not limited thereto. The battery cell 20 may be cylindrical, flat, rectangular, or in other shapes.

[0059] Please refer to Figure 2 , Figure 2 2 is a schematic diagram of the exploded structure of a battery cell according to one or more embodiments. A battery cell 20 refers to the smallest unit that constitutes a battery. Figure 2 The battery cell 20 includes an end cover 21, a shell 22, an electrode assembly 23 and other functional components.

[0060] The end cap 21 refers to a component that covers the opening of the shell 22 to isolate the internal environment of the battery cell 20 from the external environment. Without limitation, the shape of the end cap 21 can be adapted to the shape of the shell 22 to match the shell 22. Optionally, the end cap 21 can be made of a material with a certain hardness and strength (such as aluminum alloy), so that the end cap 21 is not easily deformed when squeezed and collided, so that the battery cell 20 can have a higher structural strength and the safety performance can also be improved. Functional components such as electrode terminals 21a can be provided on the end cap 21. The electrode terminal 21a can be used to electrically connect with the electrode assembly 23 for outputting or inputting electrical energy of the battery cell 20. In some embodiments, the end cap 21 can also be provided with a pressure relief mechanism for releasing the internal pressure when the internal pressure or temperature of the battery cell 20 reaches a threshold. The material of the end cap 21 can also be a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiments of the present application do not impose special restrictions on this. In some embodiments, an insulating member may be provided inside the end cap 21, and the insulating member may be used to isolate the electrical connection components in the housing 22 from the end cap 21 to reduce the risk of short circuit. For example, the insulating member may be plastic, rubber, or the like.

[0061] The shell 22 is a component used to cooperate with the end cap 21 to form the internal environment of the battery cell 20, wherein the formed internal environment can be used to accommodate the electrode assembly 23, the electrolyte and other components. The shell 22 and the end cap 21 can be independent components, and an opening can be set on the shell 22, and the internal environment of the battery cell 20 is formed by covering the opening with the end cap 21 at the opening. Without limitation, the end cap 21 and the shell 22 can also be integrated. Specifically, the end cap 21 and the shell 22 can form a common connection surface before other components are put into the shell, and when the interior of the shell 22 needs to be encapsulated, the end cap 21 covers the shell 22. The shell 22 can be of various shapes and sizes, such as a rectangular parallelepiped, a cylindrical shape, a hexagonal prism, etc. Specifically, the shape of the shell 22 can be determined according to the specific shape and size of the electrode assembly 23. The material of the shell 22 can be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiment of the present application does not impose any special restrictions on this.

[0062] The electrode assembly 23 is a component in the battery cell 100 where electrochemical reactions occur. One or more electrode assemblies 23 may be included in the housing 22. The electrode assembly 23 is mainly formed by winding or stacking positive and negative electrode sheets, and a separator is usually provided between the positive and negative electrode sheets. The parts of the positive and negative electrode sheets with active materials constitute the main body of the electrode assembly, and the parts of the positive and negative electrode sheets without active materials each constitute a tab 23a. The positive tab and the negative tab may be located together at one end of the main body or at both ends of the main body, respectively. During the charge and discharge process of the battery 100, the positive active material and the negative active material react with the electrolyte, and the tab 23a connects the electrode terminals to form a current loop.

[0063] In some embodiments, the negative electrode plate includes a current collector and a negative electrode active material layer disposed on the current collector. The specific types of negative electrode active materials are not subject to specific restrictions and can be selected according to needs. For example, the negative electrode active material is selected from one or more of natural graphite, artificial graphite, mesophase microcarbon beads (abbreviated as MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2.

[0064] The negative electrode plate may also include a binder, a conductive agent and other optional additives. As an example, the conductive agent may be one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, Super P (SP), graphene and carbon nanofibers. As an example, the binder may be one or more of styrene-butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA) and polyvinyl butyral (PVB). As an example, other optional additives may be thickeners and dispersants (such as sodium carboxymethyl cellulose CMC-Na), PTC thermistor materials.

[0065] In some embodiments, the electrolyte solvent of the electrolyte includes one or more of fluorinated carbonates, fluorinated carboxylates, sulfones, and fluorinated ethers, and fluorinated ethers may be selected. The selected electrolyte is a high-voltage resistant electrolyte, which has reduced acidity under high voltage, can significantly reduce surface side reactions, and improve battery stability.

[0066] In some embodiments, the purpose of the electrochemical device of the present application is not particularly limited, and it can be used for any electronic device known in the prior art. The battery disclosed in the embodiment of the present application can be used for various energy storage systems using batteries as power supplies or using batteries as energy storage elements. That is, a kind of electrical equipment is provided. In some embodiments, the electrochemical device of the present application can be used for, but not limited to, notebook computers, pen-input computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini-discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles, bicycles, ships, spacecraft, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries and sodium ion capacitors, etc.

[0067] The device can select battery cells, battery modules or battery packs according to its usage requirements.

[0068] Please refer to Figure 3 , Figure 3: is a schematic diagram of the structure of a vehicle according to one or more embodiments. The vehicle 1000 may be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A battery 100 is provided inside the vehicle 1000, and the battery 100 may be provided at the bottom, the head or the tail of the vehicle 1000. The battery 100 may be used to power the vehicle 1000, for example, the battery 100 may be used as an operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300, and the controller 200 is used to control the battery 100 to power the motor 300, for example, for the starting, navigation and working power requirements of the vehicle 1000 during driving.

[0069] In some embodiments of the present application, the battery 100 can not only serve as an operating power source for the vehicle 1000, but also serve as a driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0070] Please refer to Figure 4 , Figure 4 2 is a schematic diagram of the structure of a battery isolation membrane provided by an embodiment of the present application. The embodiment of the present application provides a battery isolation membrane 2310, including a base membrane 2311 and a thermal protection layer 2312. The thermal protection layer 2312 is provided on at least one side of the base membrane 2311. The thermal protection layer 2312 includes an organic thermal expansion material and inorganic particles.

[0071] Among them, the battery separator 2310 is used to separate the positive and negative electrodes of the battery cell to prevent the two electrodes from contacting and short-circuiting. In addition, it has the function of allowing electrolyte ions to pass through and blocking electrons from passing through. The base film 2311 is a thin film structure, and the base film 2311 has two opposite surfaces arranged along its thickness direction. The thermal protection layer 2312 can be arranged only on one side of the base film 2311, or it can be arranged on both sides of the base film 2311. It should be noted that "the thermal protection layer 2312 is arranged on at least one side of the base film 2311" can be the surface of the thermal protection layer 2312 directly contacting the base film 2311, or there can be other functional layers between the thermal protection layer 2312 and the base film 2311. Organic thermal expansion material refers to an organic material that expands in volume when heated, and inorganic particles refer to inorganic non-metallic particles. The heat protection layer 2312 includes organic heat expansion materials and inorganic particles, wherein the organic heat expansion materials can expand in volume when heated, and the expanded materials can block the pores of the base film 2311, reduce the pore size for the free migration of active ions, hinder the migration of active ions, and thus reduce the migration of current; the inorganic particles can improve the thermal stability of the battery cell, reduce the shrinkage of the battery isolation film 2310 caused by thermal stress, and reduce the occurrence of side reactions such as direct contact between the positive and negative electrodes caused by the size shrinkage of the battery isolation film 2310. In the heat protection layer 2312, if the content of organic heat expansion materials or inorganic particles is too much, the internal resistance of the battery isolation film 2310 will increase, and if the content is too little, it is difficult to play a role in thermal protection of the base film 2311.

[0072] In the embodiment of the present application, a heat protection layer 2312 is provided on at least one side of the base film 2311, and the heat protection layer 2312 includes an organic heat expansion material and inorganic particles; when the temperature inside the battery cell rises abnormally, the organic heat expansion material can expand in volume when heated, and the expanded material can block the pores of the base film 2311, so that the aperture of the active ions can be reduced, and the migration of the active ions can be hindered, which can quickly reduce the migration of the current between the positive and negative electrodes, reduce the thermal runaway of the battery cell at high temperature, reduce the deterioration of the life characteristics, and improve the safe use performance of the battery cell. In addition, the inorganic particles have a high tolerance temperature, and still have good dimensional temperature properties when heated within the melting point range. In the case of abnormal temperature rise inside the battery cell, the inorganic particles can reduce the shrinkage of the battery isolation film 2310 caused by thermal stress, reduce the short circuit caused by direct contact between the positive and negative electrodes due to the shrinkage of the battery isolation film 2310, improve the thermal stability of the battery cell, and further improve the safe use performance of the battery cell.

[0073] In some embodiments, the weight ratio of the organic thermal expansion material to the inorganic particles is 1:0.5-1:5.

[0074] In any embodiment, the weight ratio of the organic thermal expansion material to the inorganic particles can be 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2, 1:2.1, 1:2.2, 1:2.3, 1:2.4, 1:2.5, 1:2.6, 1:2.7, 1:2.8, 1:2.9, 1:3, 1:3.1, 1:3.2, 1:3.3, 1:3.4, 1:3.5, 1:3.6, 1:3.7, 1:3.8, 1:3.9, 1:4, 1:4.1, 1:4.2, 1:4.3, 1:4.4, 1:4.5, 1:4.6, 1:4.7, 1:4.8, 1:4.9, 1:5, or a range consisting of any two of the above values. For example, the weight ratio of the organic thermal expansion material to the inorganic particles can be 1:0.5-1.5, 1:1.5-3, or 1:4-5. The weight ratio of the organic thermal expansion material to the inorganic particles is 1:0.5-1:5. On the one hand, it can expand due to heat and hinder the migration of active ions, reducing the thermal runaway of the battery monomer at high temperature. On the other hand, it can improve the thermal stability of the battery monomer to reduce the shrinkage problem of the battery isolation film 2310 caused by thermal stress.

[0075] In some embodiments, the thermal protection layer 2312 is a single-layer structure in which an organic thermal expansion material and inorganic particles are mixed.

[0076] Among them, the inorganic particles are distributed in the organic thermal expansion material, and the two are mixed to form a single-layer structure. The setting of the single-layer structure is conducive to reducing the thickness of the thermal protection layer 2312, reducing the internal resistance of the battery isolation film 2310, and increasing the internal current of the battery cell. In addition, the setting of the single-layer structure allows the thermal protection layer 2312 to be formed in one step, which is conducive to simplifying the process of the thermal protection layer 2312 and reducing the difficulty of the process. In some embodiments, the thermal protection layer 2312 also includes a binder for bonding the inorganic particles and / or the organic thermal expansion material.

[0077] In some embodiments, please refer to Figure 5 , Figure 5 It is another structural schematic diagram of the battery isolation membrane provided by an embodiment of the present application. The thermal protection layer 2312 includes a stacked inorganic particle layer 2312a and a thermal expansion layer 2312b. The inorganic particle layer 2312a is closer to the base film 2311 than the thermal expansion layer 2312b, and the thermal expansion layer includes an organic thermal expansion material.

[0078] Among them, the organic thermal expansion material and the inorganic particles are arranged in layers, the film layer where the inorganic particles are located is closer to the base film 2311, and the film layer where the organic thermal expansion material is located is arranged on the side of the film layer where the inorganic particles are located away from the base film 2311. When the temperature inside the battery cell rises abnormally, the film layer where the organic thermal expansion material is located first contacts the heat, and in a relatively short time, the film layer material can be expanded by heat, block the pores of the base film 2311, and hinder the migration of active ions. At the same time, the inorganic particle layer close to the base film can block heat transfer and further protect the isolation film from thermal breakdown. If the film layer where the inorganic particles are located is located on the side of the film layer where the organic thermal expansion material is located away from the base film 2311, when the temperature inside the battery cell rises abnormally, due to the heat insulation of the inorganic particles, the time for the organic thermal expansion material to receive heat will be delayed, so that the thermal protection effect of the organic thermal expansion material on the base film 2311 is delayed, and the risk of thermal runaway of the battery cell is relatively high, which has an adverse effect on the safety performance of the battery cell.

[0079] In some embodiments, the heat transition temperature of the organic thermally expandable material is in the range of 110°C to 130°C.

[0080] The thermal transition temperature of the organic thermal expansion material refers to the starting temperature at which the volume of the organic thermal expansion material expands when heated, and the starting temperature has a direct impact on the protective effect of the thermal protection layer 2312. For example, if the starting temperature is low, the volume of the organic thermal expansion material expands at a lower temperature, so that the aperture of the base film 2311 is blocked at a lower temperature, and the battery cell can hinder the migration of current at a lower temperature, which is beneficial to reduce the thermal runaway of the battery cell and improve the safety performance of the battery cell. On the contrary, if the starting temperature is high, it is not conducive to controlling the thermal runaway of the battery cell.

[0081] In any embodiment, the heat transition temperature of the organic thermal expansion material can be 110°C, 112°C, 114°C, 116°C, 118°C, 120°C, 122°C, 124°C, 126°C, 128°C, 130°C, or a range consisting of any two of the above values. For example, the heat transition temperature of the organic thermal expansion material can be 110°C-120°C, 115°C-125°C or 120°C-130°C, etc.

[0082] In some embodiments, the organic thermal expansion material includes one or more of polyamide (PA), polyvinyl chloride (PVC), polyoxymethylene (POM), polycarbonate (PC), polyvinylidene chloride (PVDC), and polymethyl methacrylate (PMMA).

[0083] The organic thermal expansion material can be one of the above materials or a combination of the above materials. The selection of the above materials can make the organic thermal expansion material have a suitable thermal transition temperature and expand in volume when heated, so that the thermal protection layer 2312 can protect the base film 2311 at a relatively low temperature, which is conducive to making the battery cell have good safety performance.

[0084] In some embodiments, the organic thermal expansion material includes one or more of polyamide, polyvinyl chloride, and polymethyl methacrylate; optionally, there are at least two organic thermal expansion materials, and the mass ratio of the two organic thermal expansion materials is (0.3-5):(0.3-5).

[0085] The organic thermal expansion material can be one of the above materials or a combination of the above materials. The selection of the above materials enables the thermal protection layer 2312 to play a good protective role on the base film 2311, which is beneficial to improving the safety performance of the battery cell.

[0086] In any embodiment, when there are at least two organic thermal expansion materials, the mass ratio of the two organic thermal expansion materials can be 0.3:0.3, 0.3:0.5, 0.3:1, 0.3:1.5, 0.3:2, 0.3:2.5, 0.3:3, 0.3:3.5, 0.3:4, 0.3:4.5, 0.3:5, 1:0.3, 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1 :4.5, 1:5, 2:0.3, 2:1, 2:3, 2:5, 3:0.3, 3:1, 3:2, 3:4, 3:5, 4:0.3, 4:1, 4:3, 4:5, 5:0.3, 5:1, 5:2, 5:3, 5:4, 5:5, or a range consisting of any two of the above values. For example, the mass ratio of the two organic thermal expansion materials can be (0.5-5):(0.5-5), (1-5):(1-5) or (1-3):(1-3), etc.

[0087] In some embodiments, the volume average particle size Dv of the inorganic particles is 50 It is 10nm-30nm, and can be optionally 10nm-20nm.

[0088] Among them, the volume average particle size Dv 50It refers to the particle size that reaches 50% of the volume accumulation measured from the small particle size in the volume-based particle size distribution. In any embodiment, the volume average particle size of the inorganic particles can be 10nm, 15nm, 20nm, 25nm, 30nm, or a range consisting of any two of the above values. For example, the volume average particle size of the inorganic particles can be 10nm-20nm, 15nm-25nm or 20nm-30nm, etc. The volume average particle size of the inorganic particles within the above range is beneficial to improving the dispersion of the inorganic particles in the thermal protection layer 2312, to blocking the pores of the base film 2311, and to reducing the thickness of the thermal protection layer 2312. Volume average particle size Dv 50 The test refers to the laser particle size analyzer diffraction method of GB / T19077-2016. Take a clean beaker, add an appropriate amount of the sample to be tested, add a surfactant and then a dispersant. After sufficient dispersion, use a laser particle size analyzer to measure the particle size distribution characteristics (shading degree: 8-12%).

[0089] In some embodiments, the inorganic particles include one or more of SiO2, TiO2, Al2O3, CaCO3, ZrO2, MgO, ThO2, BeO, Mg2SiO4, MgSiO3, MgAl2O4, BeAl2O4, and AlN.

[0090] The inorganic particles may be one of the above materials or a combination of the above materials. The selection of the above materials can make the inorganic particles have good dimensional stability for the base film 2311, which is beneficial to improving the safety performance of the battery cell.

[0091] In some embodiments, the thickness of the thermal protection layer 2312 is 2 μm-8 μm, and may be 3 μm-5 μm.

[0092] The thermal protection layer 2312 needs to have a certain thickness to achieve the thermal protection effect on the base film 2311. In addition, the thickness needs to be within a certain range to reduce the effect of the introduction of the thermal protection layer 2312 on the internal resistance of the battery isolation film 2310. In any embodiment, the thickness of the thermal protection layer 2312 can be 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, or a range consisting of any two of the above values. For example, the thickness of the thermal protection layer 2312 can be 2μm-4μm, 3μm-5μm or 6μm-8μm, etc. Within the above range, a smaller thickness makes the thermal protection layer 2312 have less effect on the internal resistance of the battery isolation film 2310, and a larger thickness is conducive to improving the thermal protection effect of the thermal protection layer 2312 on the base film 2311.

[0093] In some embodiments, the thermal protection layer 2312 also includes a binder, which includes one or more of polyvinylidene fluoride, polyurethane, polyacrylate, polyacrylamide, and cyclodextrin; the mass proportion of the binder in the thermal protection layer 2312 is 0.5%-2%.

[0094] In any embodiment, the mass proportion of the adhesive in the thermal protection layer 2312 can be 0.5%, 1%, 1.5%, 2%, or a range consisting of any two of the above values. For example, the mass proportion of the adhesive in the thermal protection layer 2312 can be 0.5%-1%, 1%-1.5% or 1.5%-2%, etc.

[0095] The binder is used to bond the inorganic particles and / or the organic thermal expansion material. The binder can be one of the above materials or a combination of the above materials. The selection of the above materials can bond the inorganic particles and the organic thermal expansion material together to form the thermal protection layer 2312, and can make the thermal protection layer 2312 bonded to at least one side of the base film 2311.

[0096] In some embodiments, the battery isolation film 2310 further includes an adhesive layer 2313 disposed on at least one side of the base film 2311; Optionally, the adhesive layer 2313 is disposed on a side of the heat protection layer 2312 away from the base film 2311; Optionally, the thickness of the adhesive layer 2313 is 5 μm-15 μm; Optionally, the adhesive layer 2313 includes one or more of polyvinylidene fluoride, polyurethane, polyacrylate, polyacrylamide, and cyclodextrin.

[0097] Among them, the adhesive layer 2313 allows the battery isolation film 2310 to be arranged between the positive and negative electrodes, and to be bonded to the positive and negative electrodes respectively, thereby improving the shaping effect of the battery cell and reducing the fluffy phenomenon between the layers of the battery cell. The adhesive layer 2313 is arranged on the side of the thermal protection layer 2312 away from the base film 2311. In some embodiments, the adhesive layer 2313 is arranged on the surface of the thermal protection layer 2312 away from the base film 2311. In any embodiment, the thickness of the adhesive layer 2313 can be 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, or a range consisting of any two of the above values. For example, the thickness of the adhesive layer 2313 can be 5μm-8μm, 7μm-10μm or 11μm-15μm, etc. The thickness of the adhesive layer 2313 is within the above range, which can improve the shaping effect of the battery cell, reduce the fluffy phenomenon between the layers of the battery cell, and control its influence on the internal resistance of the battery isolation membrane 2310 within a controllable range. The adhesive layer 2313 can be one of the above materials, or a combination of the above materials. The selection of the above materials can enable the adhesive layer 2313 to improve the shaping effect of the battery cell, reduce the fluffy phenomenon between the layers of the battery cell, and control its influence on the internal resistance of the battery isolation membrane within a controllable range.

[0098] In some embodiments, please refer to Figure 6 , Figure 6 23 is another structural schematic diagram of a battery isolation film provided by an embodiment of the present application, wherein the battery isolation film 2310 further includes an isolation layer 2314, which is closer to the base film 2311 than the thermal protection layer 2312, and the isolation layer 2314 includes inorganic particles. Optionally, the thickness of the isolation layer 2314 is 3 μm-5 μm, and can be 3.5 μm-4.5 μm.

[0099] In any embodiment, the thickness of the isolation layer 2314 can be 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, or a range consisting of any two of the above values. For example, the thickness of the isolation layer 2314 can be 3 μm-4 μm, 3.5 μm-4.5 μm, 4 μm-5 μm, etc. Within the above range, a smaller thickness makes the isolation layer 2314 have less influence on the internal resistance of the battery isolation film 2310, and a larger thickness is conducive to improving the effect of the isolation layer 2314 on the dimensional stability of the base film 2311.

[0100] In some embodiments, the porosity of the base film 2311 is 30%-70%, and can be 50%; the thickness of the base film 2311 is 5μm-10μm, and can be 6μm-8μm; the base film 2311 includes one or more of polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyvinyl alcohol (PVA), polyimide (PI), polyamide (PA), polyacrylonitrile (PAN), polyethylene oxide (PEO), polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), and polyvinylidene fluoride (PVDF). Polyvinyl chloride (PVC) and polyimide (PI) can be selected.

[0101] Among them, the base film 2311 needs to have a certain porosity to achieve its function of realizing active ion migration, and the porosity needs to be within a certain range so that the base film 2311 has a certain mechanical strength. In any embodiment, the porosity of the base film 2311 can be 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or a range composed of any two of the above values. For example, the porosity of the base film 2311 can be 30%-40%, 45%-65% or 60%-70%, etc. Within the above range, a smaller porosity is conducive to the base film 2311 having a greater mechanical strength, and a larger porosity is conducive to the base film 2311 having a better level of active ion migration. The thickness of the base film 2311 needs to be within a certain range so that the internal resistance of the base film 2311 is in a smaller range. In any embodiment, the thickness of the base film 2311 can be 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, or a range consisting of any two of the above values. For example, the thickness of the base film 2311 can be 6μm-8μm or 8μm-10μm, etc. Within the above range, a smaller thickness is beneficial to reducing the internal resistance of the base film 2311, and a larger thickness is beneficial to improving the mechanical strength of the base film 2311 and the safety performance of the battery cell. The base film 2311 can be one of the above materials or a combination of the above materials. The selection of the above materials can enable the base film 2311 to have good ion migration performance and mechanical properties.

[0102] An embodiment of the present application provides a method for preparing any battery isolation film 2310 provided in the first aspect, comprising: Providing a base film 2311; A heat protection layer 2312 is formed on at least one side of the base film 2311 , and the heat protection layer 2312 includes an organic thermal expansion material and inorganic particles.

[0103] In the embodiment of the present application, by preparing a battery isolation film 2310 including a thermal protection layer 2312, the thermal runaway of the battery monomer at high temperature is reduced, and the safe use performance of the battery monomer is improved.

[0104] In some embodiments, a heat protection layer 2312 is formed on at least one side of the base film 2311, including: A precursor is coated on at least one side of the base film 2311; the precursor includes an organic thermal expansion material, inorganic particles and a solvent; The base film 2311 coated with the precursor is dried.

[0105] Coating refers to using a mechanical method to widely and continuously cover at least one side of the base film 2311 with a precursor. In some embodiments, coating includes spraying, which refers to a coating method that disperses the precursor into uniform and fine droplets by pressure or centrifugal force and applies it to the surface of the coated object. Precursor refers to the raw material for forming the thermal protection layer 2312. Drying refers to the operation of using heat energy to vaporize and separate the moisture (water or other solvent) in the wet material, thereby obtaining a material with low water content.

[0106] The embodiment of the present application enables the heat protection layer 2312 to be uniformly formed on at least one side of the base film 2311 by coating, which is beneficial for the heat protection layer 2312 to have good uniform distribution and performance stability.

[0107] In some embodiments, the process parameters of the drying treatment include: a drying temperature of 60°C-100°C, optionally 80°C-90°C; a drying time of 2h-24h, optionally 6h-12h.

[0108] Wherein, in any embodiment, the drying temperature can be 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, or a range consisting of any two of the above values, for example, the drying temperature can be 60°C-70°C, 70°C-80°C, 80°C-90°C, 90°C-100°C, etc. In any embodiment, the drying time can be 2h, 4h, 6h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h, 24h, or a range consisting of any two of the above values, for example, the drying time can be 2h-6h, 6h-12h, 12h-18h, 18h-24h, etc.

[0109] In some embodiments, the mass concentration of the organic thermal expansion material is 2%-25%; the weight ratio of the organic thermal expansion material to the inorganic particles is 1:0.5-1:5.

[0110] In any embodiment, the mass concentration of the organic thermal expansion material can be 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, or a range consisting of any two of the above values. For example, the mass concentration of the organic thermal expansion material can be 2%-10%, 5%-15% or 15%-25%, etc. In any embodiment, the weight ratio of the organic thermal expansion material to the inorganic particles may be 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2, 1:2.1, 1:2.2, 1:2.3, 1:2.4, 1:2.5, 1:2.6, 1:2.7, 1:2.8, 1:2.9, 1:3, 1:3. .1, 1:3.2, 1:3.3, 1:3.4, 1:3.5, 1:3.6, 1:3.7, 1:3.8, 1:3.9, 1:4, 1:4.1, 1:4.2, 1:4.3, 1:4.4, 1:4.5, 1:4.6, 1:4.7, 1:4.8, 1:4.9, 1:5, or a range consisting of any two of the above values. For example, the weight ratio of the organic thermal expansion material to the inorganic particles can be 1:0.5-1:1.5, 1:1.5-1:3 or 1:4-1:5, etc.

[0111] The beneficial effects of the present application are further illustrated below in conjunction with embodiments.

[0112] In order to make the technical problems, technical solutions and beneficial effects solved by the embodiments of the present application clearer, the following will be further described in detail with reference to the embodiments and the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present application and its applications. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0113] Embodiment 1: 1. Prepare battery isolation film 2310: Mix polyamide, SiO2 particles and solvent in a weight ratio of 1:0.5:20 to form a precursor, spray it on the base film 2311 to form a single-layer thermal protection layer 2312; the base film 2311 is made of polyimide; polyurethane is coated on the surface of the thermal protection layer 2312 away from the base film 2311 to form a bonding layer 2313, and its coating weight is 0.75mg / 5000mm 2; The above structure is transferred to an oven and dried at a temperature of 80°C to obtain a battery isolation film 2310. The battery isolation film 2310 has a base film 2311 with a thickness of 7μm, a thermal protection layer 2312 with a thickness of 2μm, and an adhesive layer 2313 with a thickness of 10μm.

[0114] 2. Prepare the negative electrode sheet and the positive electrode sheet separately, using graphite as the active material of the negative electrode sheet and lithium nickel cobalt manganese oxide Li(NiCoMn)O2 as the active material of the positive electrode sheet; stack the positive electrode sheet, the battery separator 2310 and the negative electrode sheet, and inject the electrolyte to form a battery cell.

[0115] 3. Volume average particle size Dv 50 The test refers to the laser particle size analyzer diffraction method of GB / T19077-2016. Take a clean beaker, add an appropriate amount of the sample to be tested, add a surfactant and then a dispersant. After sufficient dispersion, use a laser particle size analyzer to measure the particle size distribution characteristics (shading degree: 8-12%).

[0116] 4. At 25°C, charge the assembled battery cells at 4C to 4.4V, leave them for 10 minutes, discharge them at 1C to 2.5V, then charge them at 0.33C constant current to 4.4V, and then charge them at 0.05C constant voltage to 4.4V; perform static tests on the battery cells at different high temperatures, and pass the test if the battery cells do not explode, catch fire, or smoke. Test 5 battery cells in each group, and calculate the pass rate of the battery test in the harsh environment of high temperature when the battery cells are continuously left at different high temperatures for different periods of time (for example, if 4 batteries pass the test, it is expressed as 4 / 5). See Table 1 for data.

[0117] Table 1 Battery parameters and performance of various embodiments and comparative examples Note: Dv in Table 1 50 Refers to the volume average particle size of inorganic particles.

[0118] The results show that the thermal protection layers 2312 of comparative examples 1-2 are all made of a single material. Compared with comparative examples 1-2, the thermal protection layers 2312 of the embodiments of the present application use materials including organic thermal expansion materials and inorganic particles, and the battery test has a higher pass rate, which is beneficial to reduce the thermal runaway of the battery cell at high temperature and improve the safe use performance of the battery cell.

[0119] From the examples 1-2, when the organic thermal expansion material of the thermal protection layer 2312 is a single material or multiple materials, the pass rates of the battery tests are not much different, and the battery tests all have a high pass rate.

[0120] From Examples 2-7, it can be seen that when the proportion of inorganic particulate materials in the thermal protection layer 2312 increases, the pass rate of the battery test decreases. Therefore, the weight ratio of the organic thermal expansion material to the inorganic particulate material in the thermal protection layer 2312 has a certain influence on the pass rate of the battery test. The weight ratio of the organic thermal expansion material to the inorganic particulate material in the thermal protection layer 2312 should be adjusted to increase the pass rate of the battery test to a greater extent.

[0121] From Examples 8 to 10, it can be seen that the pass rates of the battery tests using different types of organic thermal expansion materials are not much different, and the battery tests all have a high pass rate.

[0122] From Examples 11-16, the particle size of the inorganic granular material is different and the thickness of the thermal protection layer 2312 is different, and the pass rate of the battery test fluctuates to a certain extent. Therefore, the thickness of the thermal protection layer 2312 and the particle size of the inorganic granular material included have a certain influence on the use effect of the thermal protection layer 2312. The thickness of the thermal protection layer 2312 and the particle size of the inorganic granular material included should be regulated to increase the pass rate of the battery test to a greater extent and enhance the safe use performance of the battery cells.

[0123] From Example 17, a thermal protection layer 2312 is provided on one side of the isolation layer 2314, and the battery test also has a high pass rate.

[0124] In the several embodiments provided in the present application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of units is only a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.

[0125] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0126] The above description is only an implementation method of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly used in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A battery separator, characterized in that: include: Basement membrane; The heat protection layer is disposed on at least one side of the base film, and the heat protection layer comprises an organic thermal expansion material and inorganic particles.

2. The battery separator according to claim 1, characterized in that: The weight ratio of the organic thermal expansion material to the inorganic particles is 1:0.5-1:

5.

3. The battery separator according to claim 1 or 2, characterized in that: The heat protection layer is a single-layer structure in which an organic heat expansion material and inorganic particles are mixed.

4. The battery separator according to any one of claims 1 to 3, characterized in that: The heat protection layer includes an inorganic particle layer and a heat expansion layer which are stacked, the inorganic particle layer is closer to the base film than the heat expansion layer, and the heat expansion layer includes an organic heat expansion material.

5. The battery separator according to any one of claims 1 to 4, characterized in that: The thermal expansion temperature of the organic thermal expansion material is in the range of 110°C to 130°C.

6. The battery separator according to any one of claims 1 to 5, characterized in that: The organic thermal expansion material includes one or more of polyamide, polyvinyl chloride, polyoxymethylene, polycarbonate, polyvinylidene chloride, and polymethyl methacrylate.

7. The battery separator according to any one of claims 1 to 6, characterized in that: The organic thermal expansion material includes one or more of polyamide, polyvinyl chloride, and polymethyl methacrylate; optionally, the organic thermal expansion materials are at least two, and the mass ratio of the two organic thermal expansion materials is (0.3-5):(0.3-5).

8. The battery separator according to any one of claims 1 to 7, characterized in that: The volume average particle size Dv of the inorganic particles 50 It is 10nm-30nm, and can be optionally 10nm-20nm.

9. The battery separator according to any one of claims 1 to 8, characterized in that: The inorganic particles include one or more of SiO2, TiO2, Al2O3, CaCO3, ZrO2, MgO, ThO2, BeO, Mg2SiO4, MgSiO3, MgAl2O4, BeAl2O4, and AlN.

10. The battery separator according to any one of claims 1 to 9, characterized in that: The thickness of the thermal protection layer is 2 μm-8 μm, and can be 3 μm-5 μm.

11. The battery separator according to any one of claims 1 to 10, characterized in that: The thermal protection layer further includes a binder, which includes one or more of polyvinylidene fluoride, polyurethane, polyacrylate, polyacrylamide, and cyclodextrin; the mass proportion of the binder in the thermal protection layer is 0.5%-2%.

12. The battery separator according to any one of claims 1 to 11, characterized in that: The battery separator further comprises a bonding layer disposed on at least one side of the base film; Optionally, the adhesive layer is disposed on a side of the heat protection layer away from the base film; Optionally, the thickness of the bonding layer is 5 μm-15 μm; Optionally, the adhesive layer includes one or more of polyvinylidene fluoride, polyurethane, polyacrylate, polyacrylamide, and cyclodextrin.

13. The battery separator according to any one of claims 1 to 12, characterized in that: The battery isolation film further comprises an isolation layer, the isolation layer is closer to the base film than the heat protection layer, and the isolation layer comprises inorganic particles; Optionally, the thickness of the isolation layer is 3 μm-5 μm, and optionally 3.5 μm-4.5 μm.

14. The battery separator according to any one of claims 1 to 13, characterized in that: The porosity of the base film is 30%-70%, and can be optionally 50%; the thickness of the base film is 5μm-10μm, and can be optionally 6μm-8μm; the base film includes one or more of polyethylene, polypropylene, polyethylene terephthalate, polyvinyl alcohol, polyimide, polyamide, polyacrylonitrile, polyethylene oxide, polyvinyl chloride, polyvinylidene chloride, and polyvinylidene fluoride, and can be optionally polyvinyl chloride and polyimide.

15. A method for preparing a battery separator according to any one of claims 1 to 14, characterized in that: include: providing a basement membrane; A heat protection layer is formed on at least one side of the base film, the heat protection layer including an organic thermal expansion material and inorganic particles.

16. The method for preparing a battery separator according to claim 15, characterized in that: The step of forming a heat protection layer on at least one side of the base film comprises: coating a precursor on at least one side of the base film, the precursor comprising an organic thermal expansion material, inorganic particles and a solvent; The base film coated with the precursor is dried.

17. The method for preparing a battery separator according to claim 16, characterized in that: The process parameters of the drying treatment include: a drying temperature of 60°C-100°C, optionally 80°C-90°C; a drying time of 2h-24h, optionally 6h-12h.

18. The method for preparing a battery separator according to claim 16 or 17, characterized in that: The mass concentration of the organic thermal expansion material is 2%-25%; the weight ratio of the organic thermal expansion material to the inorganic particles is 1:0.5-1:

5.

19. A battery cell, characterized in that: include: Positive electrode; Negative electrode; A battery separator, disposed between the positive electrode sheet and the negative electrode sheet; Wherein, the battery separator comprises the battery separator according to any one of claims 1 to 14, or the battery separator prepared by the preparation method according to any one of claims 15 to 18.

20. A battery, characterized in that: Comprising the battery cell as claimed in claim 19.

21. An electrical equipment, characterized in that: Comprising a battery as claimed in claim 20.

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