Separating membrane, secondary battery, battery pack and electric device

Abstract

The invention belongs to the technical field of batteries, and particularly discloses an isolating membrane, a secondary battery, a battery pack and an electric device. The secondary battery provided by the invention comprises a positive pole piece, an isolating membrane and a negative pole piece, and the isolating membrane comprises a base membrane and a coating located on at least one side surface of the base membrane; the coating comprises a first adsorbent and a second adsorbent; the first adsorbent comprises any one or more of super absorbent resin, silica gel and a modified compound thereof, and an aluminophosphate molecular sieve; the second adsorbent comprises any one or more of alkali metal salts or alkaline earth metal salts; at least part of the second adsorbent is located on the surface and inside of the first adsorbent. The first adsorbent can be loaded on the second adsorbent to form a material with stable physicochemical properties, the material can adsorb free moisture, acid and the like in the battery, damage of the substances to a solid electrolyte interface of the battery is reduced, and the secondary battery can simultaneously take cycle stability and storage stability into consideration.

Description

Technical Field

[0001] This application relates to the field of batteries, specifically to a separator, a secondary battery, a battery pack, and an electrical device. Background Technology

[0002] Secondary batteries are widely used in various consumer electronics and electric vehicles due to their outstanding characteristics such as light weight, no pollution, and no memory effect. Among them, lithium-ion batteries have a very wide range of applications in portable electronic devices and electric vehicles.

[0003] As the application of rechargeable batteries becomes more and more widespread, the requirements for battery performance are also becoming higher and higher. Summary of the Invention

[0004] In view of the above problems, this application provides a separator, a secondary battery, a battery pack, and an electrical device, which are beneficial to improving the cycle stability and storage stability of the battery.

[0005] The first aspect of this application is to provide a secondary battery, including a positive electrode, a separator and a negative electrode stacked together;

[0006] The separator membrane comprises a base membrane and a coating located on at least one surface of the base membrane;

[0007] The coating comprises a first adsorbent and a second adsorbent;

[0008] The first adsorbent comprises any one or more of the following: superabsorbent resin, silica gel and its modified compounds, and aluminum phosphate molecular sieve.

[0009] The second adsorbent comprises any one or more of alkali metal salts or alkaline earth metal salts.

[0010] At least a portion of the second adsorbent is located on the surface and inside the first adsorbent.

[0011] The first adsorbent of this application can support a second adsorbent to form a material with stable physicochemical properties. Specifically, the first adsorbent acts as the host and the second adsorbent acts as the guest. The host and guest are combined through various means such as physical adsorption and chemical bonding to form a material with stable physicochemical properties. This material can further adsorb free water and acids (such as hydrofluoric acid) inside the battery through various means such as physical adsorption and chemical bonding, reducing the damage of these substances to the solid electrolyte interface (SEI film) of the battery, so that the secondary battery can simultaneously achieve cycle stability and storage stability.

[0012] In some embodiments of this application, the mass of the second adsorbent is 10% to 30% of the mass of the first adsorbent.

[0013] The second adsorbent in this application has a mass of 10% to 30% of the mass of the first adsorbent, so that the second adsorbent is fully loaded on the surface and inside of the first adsorbent, thereby improving the structural stability of the combined material and facilitating its adsorption characteristics for free water, acidic substances (such as hydrofluoric acid), and gas molecules inside the battery.

[0014] In some embodiments of this application, the weight-average molecular weight of the superabsorbent resin is 100,000 to 500,000.

[0015] The superabsorbent resin in this application refers to a polymer with a certain degree of cross-linking. This polymer can quickly absorb hundreds of times its own weight in water to form a gel, which can retain moisture under certain pressure without separating. In this application, a superabsorbent resin with a weight-average molecular weight of 100,000 to 500,000 is selected, which is beneficial for forming a material with stable physicochemical properties through various means such as physical adsorption and chemical bonding with the second adsorbent.

[0016] In some embodiments of this application, the superabsorbent resin includes one or more of polyacrylate and its modified compounds, starch-acrylate polymers and their derivatives, starch-acrylonitrile polymers and their derivatives, starch-acrylamide polymers and their derivatives, and acrylamide-acrylonitrile-acrylic acid terpolymers and their derivatives.

[0017] The superabsorbent resins listed in this application possess a cross-linked structure with an internal three-dimensional network structure. Numerous ionic groups are distributed within this network. Water molecules enter this network structure and are adsorbed and fixed within the network by bonding with these ions. Due to the elasticity of the network, it can accommodate a large number of water molecules. When the cross-linking density is high, the extension of the resin molecular chains is restricted, leading to a decrease in water absorption. To control the cross-linking density, this application selects to control the weight-average molecular weight of the superabsorbent resin.

[0018] In some embodiments of this application, the volumetric particle size distribution Dv50 of silica gel and its modified compounds is 1.0 μm to 2.7 μm;

[0019] and / or;

[0020] The average pore size of silica gel and its modified compounds is 6 nm to 15 nm;

[0021] and / or;

[0022] The specific surface area (BET) of silica gel and its modified compounds is 200 m². 2 / g~700m 2 / g;

[0023] and / or;

[0024] The pore volume of silica gel and its modified compounds is 1.05 cm³. 3 / g~2.0cm 3 / g.

[0025] The silica gel and its modified compounds in this application possess a porous structure. Generally, mesopores have a pore size between 2 nm and 50 nm. The average pore size of the silica gel and its modified compounds in this application is 6 nm to 15 nm, therefore it can be inferred that their interior is mainly composed of mesopores. Under this porous structure and volumetric particle size distribution, the specific surface area (BET) of the silica gel and its modified compounds is 200 m². 2 / g~700m 2 / g, pore volume 1.05cm 3 / g~2.0cm 3 / g, which is beneficial for exerting its own adsorption of water molecules and gases, and also beneficial for loading a second adsorbent to exert the adsorption of the combined material with stable physicochemical properties.

[0026] In some embodiments of this application, the average pore size of the aluminum phosphate molecular sieve is 0.2 nm to 2 nm;

[0027] and / or;

[0028] The specific surface area (BET) of aluminum phosphate molecular sieve is 100 m². 2 / g~300m 2 / g;

[0029] and / or;

[0030] The pore volume of the aluminum phosphate molecular sieve is 0.026 cm³. 3 / g~0.09cm 3 / g.

[0031] The aluminum phosphate molecular sieve in this application has a porous structure, primarily composed of micropores. With this porous structure and particle size distribution, the specific surface area (BET) of the aluminum phosphate molecular sieve is 100 m². 2 / g~300m 2 / g, pore volume is 0.026cm 3 / g~0.09cm 3 / g, which is beneficial for exerting its own adsorption of water molecules and gases, and also beneficial for loading a second adsorbent to exert the adsorption of the combined material with stable physicochemical properties.

[0032] In some embodiments of this application, the alkali metal salt comprises any one or more of alkali metal chlorides and fluorides;

[0033] Alkaline earth metal salts include any one or more of the chlorides and fluorides of alkaline earth metals.

[0034] In some embodiments of this application, the second adsorbent comprises any one or more of lithium chloride, sodium chloride, potassium chloride, lithium fluoride, sodium fluoride, potassium fluoride, calcium fluoride, and calcium chloride.

[0035] The types listed in these embodiments are for illustrative purposes only. In fact, when the superabsorbent resin, silica gel and its modified compounds, and aluminum phosphate molecular sieve listed in this application are used as the first adsorbent, the first adsorbent has a porous three-dimensional network structure. Many ionic groups are distributed in this three-dimensional network. These ionic groups can adsorb ions in alkali metal salts or alkaline earth metal salts through physical adsorption or chemical bonding to form a stable material. The ions in this material are combined with water molecules and acid molecules due to ionic bonding. At the same time, the pores of the three-dimensional network structure can also adsorb gas molecules. With the help of the elasticity of the three-dimensional network, water molecules, acid molecules, and gas molecules are stably present inside. Even under certain pressure, they can be maintained without separating out the water, acidic substances, and gases.

[0036] In some embodiments of this application, the porosity of the coating is greater than that of the base film.

[0037] The porosity of the coating in this application is greater than that of the base film. On the one hand, this facilitates the adsorption of free moisture, acidic substances (such as hydrofluoric acid), and gas molecules inside the battery, reducing the damage of these substances to the solid electrolyte interface (SEI film) and enabling the secondary battery to simultaneously achieve cycle stability and storage stability. On the other hand, it also helps improve the wetting of the separator with the electrolyte, thereby further improving the cycle life of the secondary battery.

[0038] In some embodiments of this application, the porosity of the coating is 70% to 85%;

[0039] and / or;

[0040] The porosity of the base membrane is 30%–45%.

[0041] In some embodiments of this application, the coating is formed on the entire surface of the base film.

[0042] In some embodiments of this application, the coating is formed on a portion of the surface of the base film;

[0043] The release membrane includes the coated area where the coating is applied and the uncoated area where no coating is applied.

[0044] The coated area and blank area are alternately distributed along the first or second direction;

[0045] The first direction is different from the second direction, and they are both perpendicular to the thickness direction of the separator.

[0046] This application selects to form the coating on a portion of the base film surface. Compared to full coating, partial coating can achieve essentially the same adsorption effect.

[0047] In some embodiments of this application, the thickness of the coating is 2% to 50% of the thickness of the base film.

[0048] In some embodiments of this application, the coating further includes a binder, the mass of which is 3% to 10% of the mass of the first adsorbent;

[0049] and / or;

[0050] The binder includes any one or more of lithium metasilicate, organoboronic acid, polyvinyl alcohol, styrene-butadiene rubber, carboxymethyl cellulose, polyacrylic acid, polyacrylonitrile, polyacrylate, and polyvinylidene fluoride.

[0051] In addition to the adsorbent, the coating of this application also contains a binder, which helps to better load the adsorbent onto the base film. Since the superabsorbent resin in the first adsorbent of this application has a certain degree of adhesiveness, compared with the case where the first adsorbent does not contain superabsorbent resin, the amount of binder used in the coating will be relatively less when the first adsorbent contains superabsorbent resin. The specific usage needs to be discussed based on the actual bonding situation.

[0052] In some embodiments of this application, an insulating layer is further provided between the coating and the base film.

[0053] This application provides an insulating layer between the coating and the base film to reduce the electron conduction capability of the separator and to improve the heat shrinkage resistance and enhance the needle punching strength of the separator.

[0054] In some embodiments of this application, the positive electrode sheet includes a positive current collector and a positive electrode film layer located on either side of the surface of the positive current collector. The positive electrode film layer includes a positive electrode active material, and the volumetric particle size distribution of the positive electrode active material is Dv50 < 1.6 μm. In some embodiments of this application, it is disclosed that the volumetric particle size distribution of the positive electrode active material satisfies: 1.0 μm ≤ Dv50 < 1.6 μm.

[0055] and / or;

[0056] The compaction density of the positive electrode film is >2.5 g / cm³. 3 The preferred value is 2.5 g / cm³. 3 < Compacted density ≤ 3.4 g / cm³ 3 ;

[0057] As those skilled in the art know, materials with smaller particle sizes generally have stronger water absorption. This application discloses in these embodiments that the volumetric particle size distribution (Dv50) of the positive electrode active material is less than 1.6 μm, and can even be at the nanometer scale. For example, for lithium iron phosphate positive electrode active materials, the particle size is generally at the micrometer or nanometer scale, which will not be elaborated upon in this application. The design method provided in this application is beneficial for improving the moisture content in positive electrode active materials with smaller particle sizes.

[0058] In some embodiments of this application, the negative electrode sheet includes a negative current collector and a negative electrode film layer located on either side of the surface of the negative current collector, wherein the compaction density of the negative electrode film layer is >1.65 g / cm³. 3 The preferred value is 1.65 g / cm³. 3 < Compacted density ≤ 2.0 g / cm³ 3 .

[0059] In some embodiments of this application, the battery further includes an electrolyte, which includes one or more of carboxylic acid ester compounds and ether compounds.

[0060] A second aspect of this application is to provide a separating membrane comprising a base membrane and a coating located on at least one side surface of the base membrane. The coating comprises a first adsorbent and a second adsorbent. The first adsorbent comprises one or more of a superabsorbent resin, silica gel and its modified compounds, and aluminum phosphate molecular sieve. The second adsorbent comprises one or more of an alkali metal salt or an alkaline earth metal salt. At least a portion of the second adsorbent is located on the surface and inside the first adsorbent.

[0061] In some embodiments of this application, the mass of the second adsorbent is 10% to 30% of the mass of the first adsorbent.

[0062] A third aspect of this application is to provide a battery pack, including the secondary battery described in the first aspect or the separator described in the second aspect.

[0063] A fourth aspect of this application is to provide an electrical device comprising the secondary battery described in the first aspect, the separator described in the second aspect, or the battery pack described in the third aspect.

[0064] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0065] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0066] Figure 1 This is a schematic diagram of the battery structure of some embodiments of this application;

[0067] Figure 2 This is an exploded structural diagram of a battery according to some embodiments of this application;

[0068] Figure 3 This is a schematic diagram of the vehicle structure according to some embodiments of this application;

[0069] Figure 4 This is a schematic diagram of the battery pack structure according to some embodiments of this application;

[0070] Figure 5 This is a schematic diagram of the structure of a secondary battery according to some embodiments of this application;

[0071] Figure 6a This is a schematic diagram of the structure of the isolation membrane according to some embodiments of this application;

[0072] Figure 6b This is a top view of 6a;

[0073] Figure 7a This is a schematic diagram of another structure of the separator membrane according to some embodiments of this application;

[0074] Figure 7b This is a top view of 7a;

[0075] Figure 8 This is a schematic diagram of another structure of the separator membrane according to some embodiments of this application.

[0076] The reference numerals in the detailed embodiments are as follows:

[0077] 10000, vehicles;

[0078] 1000, Battery; 2000, Controller; 3000, Motor;

[0079] 100. Battery cell;

[0080] 200. Box body; 210. First part; 220. Second part;

[0081] 10. Secondary batteries;

[0082] 101. Housing; 102. Electrode assembly; 103. Cover plate;

[0083] 1. Negative electrode plate;

[0084] 2. Positive electrode plate;

[0085] 3. Separating membrane; 31. Base film; 32. Coating; 32a. Coated area; 32b. Blank area;

[0086] 33. Insulation layer.

[0087] First direction: the y-axis direction;

[0088] Second direction: z-axis direction;

[0089] The third direction: the x-axis of the coordinate system, or the thickness direction of the separator. Detailed Implementation

[0090] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the separator, secondary battery, battery pack, and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0091] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60–120 and 80–110 are listed for a specific parameter, it is also expected that ranges of 60–110 and 80–120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0092] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0093] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0094] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0095] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0096] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: 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).

[0097] Unless otherwise specified, in this application, the terms "first," "second," etc., are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features.

[0098] Unless otherwise specified, in this application, the term "multiple" means two or more (including two), similarly, "multiple sets" means two or more (including two sets), and "multiple pieces" means two or more (including two pieces).

[0099] Unless otherwise specified, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0100] Due to their advantages such as high energy density, long cycle life, and safety and reliability, secondary batteries have been widely used in various products. In recent years, with the significant increase in demand for secondary batteries as an energy source, higher requirements have been placed on their performance, such as kinetic performance.

[0101] Trace amounts of moisture are unavoidable in secondary batteries. Some of this moisture comes from water vapor adsorbed from the air by the raw materials, while another part may originate from solvents introduced during the manufacturing process. Moisture in the battery can react with lithium salts, undergoing hydrolysis to form acid. This acid, during long-term battery cycling, easily reacts with the oxide cathode material to further generate water. This repeated process can damage the structure of the cathode material, leading to reduced cycle life and long-term performance degradation.

[0102] Existing technologies typically control the moisture content of the positive and negative electrode sheets, separator, and electrolyte in lithium-ion batteries by drying them before electrolyte filling. However, these methods may carry the risk of incomplete drying. Existing technologies also disclose adding dehydrating agents to the electrolyte. While this can effectively reduce the moisture content, many dehydrating agents are insoluble in electrolyte. If simply dispersed in the electrolyte, side reactions can easily occur during long-term storage, affecting the stability of the electrolyte.

[0103] If the separator can be improved to increase its ability to absorb and retain moisture inside the battery, the cycle stability and storage stability of the battery can be improved while reducing the impact on the electrolyte.

[0104] Based on the above considerations, in order to reduce the moisture content inside the secondary battery, a separator, a secondary battery, a battery pack, and an electrical device were obtained by conducting relevant experimental research based on the above design concept.

[0105] First, this application discloses a secondary battery, which includes a positive electrode, a separator, and a negative electrode, wherein the positive electrode, separator, and negative electrode are sequentially stacked to form a wound cell or a stacked cell. Meanwhile, the separator includes a base film and a coating on at least one surface of the base film; the coating includes a first adsorbent and a second adsorbent; the first adsorbent includes one or more of a superabsorbent resin, silica gel and its modified compounds, and aluminum phosphate molecular sieve; the second adsorbent includes one or more of an alkali metal salt or an alkaline earth metal salt; at least a portion of the second adsorbent is located on the surface and inside the first adsorbent.

[0106] The first adsorbent of this application can load the second adsorbent to form a material with stable physicochemical properties. This material can adsorb free water and acids (such as hydrofluoric acid) inside the battery through various means such as physical adsorption and chemical bonding, thereby reducing the damage of these substances to the solid electrolyte interface (SEI film) of the battery and enabling the secondary battery to simultaneously achieve cycle stability and storage stability.

[0107] Therefore, the secondary battery provided in this application improves battery storage and cycle life without affecting energy density, thereby enhancing user experience. The secondary battery may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte composed of the aforementioned secondary battery. The outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, aluminum shell, or steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic, including but not limited to polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0108] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 This is an example of a square-structured secondary battery 10.

[0109] According to some embodiments of this application, reference is made to Figure 2 The outer packaging may include a housing 101 and a cover plate 103. The housing 101 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates forming a receiving cavity. The housing 101 has an opening communicating with the receiving cavity, and the cover plate 103 can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and separator may be formed into an electrode assembly 102 by a winding process or a stacking process. The electrode assembly 102 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 102. The secondary battery 10 may contain one or more electrode assemblies 102, which can be selected by those skilled in the art according to specific practical needs.

[0110] The electrode assembly 102 provided in this application is beneficial to improving the performance of a secondary battery when applied in a secondary battery. The secondary battery can be a power source for an electrical device or an energy storage unit for an electrical device. The electrical device is applied in the power field, such as mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., 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 is not limited to the above fields.

[0111] For ease of explanation, some embodiments of this application are illustrated using a vehicle as an example of an electrical device.

[0112] Please refer to Figure 3 , Figure 3 This is a schematic diagram of the structure of a vehicle 10000 provided in some embodiments of this application. The vehicle 10000 can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. A battery 1000 is disposed inside the vehicle 10000, and the battery 10000 can be located at the bottom, front, or rear of the vehicle 10000. The battery 10000 can be used to power the vehicle 10000; for example, the battery 10000 can serve as the operating power source for the vehicle 10000. The vehicle 10000 may also include a controller 2000 and a motor 3000. The controller 2000 is used to control the battery 10000 to supply power to the motor 3000, for example, to meet the power needs of the vehicle 10000 during startup, navigation, and driving.

[0113] In some embodiments of this application, the battery 1000 can not only serve as the operating power source for the vehicle 10000, but also as the driving power source for the vehicle 10000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 10000.

[0114] Please refer to Figure 4 , Figure 4 This is an exploded view of a battery 1000 provided in some embodiments of this application. The battery 1000 includes a housing 200 and a battery cell 100. A conventional battery cell includes a primary battery or a secondary battery. This application specifically protects a secondary battery 10. The battery cell 100 is housed within the housing 200. The housing 200 provides space for the battery cell 100, and the housing 200 can adopt various structures.

[0115] In some embodiments, the housing 200 may include a first portion 210 and a second portion 220, which overlap each other, and together define a receiving space for accommodating the secondary battery 100. The second portion 220 may be a hollow structure with one open end, and the first portion 210 may be a plate-like structure, with the first portion 210 covering the open side of the second portion 220 so that the first portion 210 and the second portion 220 together define the receiving space; alternatively, the first portion 210 and the second portion 220 may both be hollow structures with one open side, with the open side of the first portion 210 covering the open side of the second portion 220. Of course, the housing 200 formed by the first portion 210 and the second portion 220 may be of various shapes, such as a cylinder, a cuboid, etc.

[0116] In battery 1000, there can be multiple battery cells 100, which can be connected in series, parallel, or in a mixed manner. A mixed connection means that multiple battery cells 100 are connected in both series and parallel configurations. Multiple battery cells 100 can be directly connected in series, parallel, or in a mixed manner, and then the entire assembly of the multiple battery cells 100 is housed within housing 200. Alternatively, battery 1000 can also be composed of multiple battery cells 100 first connected in series, parallel, or in a mixed manner to form battery modules, and then these modules are connected in series, parallel, or in a mixed manner to form a whole, which is also housed within housing 200. Battery 1000 may also include other structures; for example, it may include a busbar component for electrical connection between the multiple battery cells 100.

[0117] Secondary batteries

[0118] This application discloses a secondary battery in some embodiments, comprising a positive electrode, a separator, and a negative electrode, wherein the positive electrode, separator, and negative electrode are sequentially stacked together to form the secondary battery using a winding or stacking process. Meanwhile, the separator comprises a base film and a coating located on at least one surface of the base film; the coating comprises a first adsorbent and a second adsorbent; the first adsorbent comprises one or more of a superabsorbent resin, silica gel and its modified compounds, and aluminum phosphate molecular sieve; the second adsorbent comprises one or more of an alkali metal salt or an alkaline earth metal salt; at least a portion of the second adsorbent is located on the surface and inside the first adsorbent.

[0119] The positive electrode, separator, and negative electrode of this application can be formed into a secondary battery using winding or stacking processes. Specifically, this application... Figure 5 The diagram illustrates a secondary battery 10 formed using a stacking method, combined with... Figure 5It is known that a negative electrode 1 or a positive electrode 2 is placed between two adjacent separators 3, and the negative electrode 1 and the positive electrode 2 are alternately arranged along the stacking direction (coordinate axis x direction). The number and size of the negative electrode 1 and / or the positive electrode 2 can be selected according to the actual situation, and will not be elaborated in this application. Furthermore, this application... Figure 5 The image only illustrates one type of lamination method; other lamination or winding methods are within the scope of protection of this application.

[0120] like Figure 6a The separator 3 illustrates that it includes a base film 31 and a coating 32 located on at least one surface of the base film 31. Here, "at least one side" can refer to either one surface or both surfaces. Figure 6a The diagram only shows a coating 32 disposed on one side of the base film 31, and the base film 31 and the coating 32 can be in direct contact, meaning the coating 32 is directly disposed on the surface of the base film 31. Figure 6a Illustration. This application also includes the provision of other film layers between the base film 31 and the coating 32, which will be described in detail later. Meanwhile, the coating 32 of this application is formed on the surface of the base film 31 in any manner conventional in the art, such as coating, deposition, etc.

[0121] The coating 32 of this application includes a first adsorbent and a second adsorbent. Clearly, both the first and second adsorbents serve the technical purpose of absorbing free moisture inside the battery. Specifically, the first adsorbent comprises one or more of a superabsorbent resin, silica gel and its modified compounds, and aluminum phosphate molecular sieves; the second adsorbent comprises a chloride.

[0122] The superabsorbent resin of this application refers to a polymer with a certain degree of cross-linking. This polymer can quickly absorb water hundreds of times its own weight to form a gel. This gel can retain moisture and not separate under certain pressure.

[0123] The silica gel and its modified compounds in this application refer to inorganic silica gel or modified inorganic silica gel. Inorganic silica gel has the chemical formula xSiO2·yH2O and possesses strong adsorption capacity. Since the surface of inorganic silica gel contains a large number of active silanol functional groups, it can be modified using modifiers such as silane coupling agents, organochlorosilanes, alcohols, amino compounds, sulfur-containing compounds, and phosphorus-containing compounds. Modification also includes using heavy metal ions to chelate with it, thereby improving the adsorption properties of inorganic silica gel.

[0124] The aluminum phosphate molecular sieve of this application is a material with sieving properties. Its structure consists of an interconnected framework of aluminum, oxygen, and phosphorus ions. In addition to oxygen tetrahedral coordination, the aluminum ions also possess oxygen pentacoordinates and oxygen hexacoordinates, thus forming a framework structure that cannot be achieved by silicon-aluminum molecular sieves. The material possesses a regular and uniform pore structure, which is used to adsorb gas or liquid molecules.

[0125] In the field of inorganic chemistry, the alkali metal salts or alkaline earth metal salts of this application refer to salt compounds formed by the combination of positively charged alkali metal ions or alkaline earth metal ions with conventional acid radical anions. Alkali metal ions include, but are not limited to, lithium ions, sodium ions, potassium ions, cesium ions, etc., while alkaline earth metal ions include, but are not limited to, magnesium ions, calcium ions, etc. Acid radical anions include, but are not limited to, chloride ions, phosphate ions, fluoride ions, etc. The second adsorbent itself possesses a certain degree of water absorption. Furthermore, the second adsorbent is easily loaded onto the surface and interior of the first adsorbent. The first adsorbent acts as the host, and the second adsorbent as the guest. The host and guest combine through various mechanisms such as physical adsorption and chemical bonding to form a physicochemically stable material. This material can adsorb free water, acidic substances (such as hydrofluoric acid), and gas molecules inside the battery, reducing the damage of these substances to the battery's solid electrolyte interface (SEI film), enabling the secondary battery to simultaneously achieve cycle stability and storage stability.

[0126] In some embodiments of this application, the mass of the second adsorbent is 10% to 30% of the mass of the first adsorbent.

[0127] The method for measuring the mass of the second adsorbent and the mass of the first adsorbent in this application includes obtaining a cross-sectional sample of the isolation membrane, distinguishing the base membrane and the coating based on the porosity, obtaining the elemental distribution in the coating using a scanning electron microscope (SEM) and an energy-dispersive X-ray spectroscopy (EDS), further calculating the mass of the first adsorbent and the mass of the second adsorbent, and then calculating the percentage of the mass of the second adsorbent to the mass of the first adsorbent.

[0128] The second adsorbent in this application has a mass of 10% to 30% of the first adsorbent, which allows the first adsorbent to be fully loaded on the surface and inside of the first adsorbent, thereby improving the structural stability of the combined material and facilitating its adsorption characteristics for free water, acidic substances (such as hydrofluoric acid), and gas molecules inside the battery.

[0129] In these embodiments, this application discloses that the mass of the second adsorbent is any one of 10%–30%, 11%–30%, 12%–30%, 13%–30%, 14%–30%, 15%–30%, 16%–30%, 17%–30%, 18%–30%, 19%–30%, 20%–30%, 21%–30%, 22%–30%, 23%–30%, 24%–30%, 25%–30%, 26%–30%, 27%–30%, 28%–30%, 29%–30%, 10%–20%, 10%–25%, or 20%–30% of the mass of the first adsorbent.

[0130] In these embodiments, this application discloses that the mass of the second adsorbent is any one of 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, or 30% of the mass of the first adsorbent, or any one of the ranges described above.

[0131] In some embodiments of this application, the weight-average molecular weight of the superabsorbent resin is 100,000 to 500,000.

[0132] The superabsorbent resin in this application refers to a polymer with a certain degree of cross-linking, which can quickly absorb hundreds of times its own weight in water to form a gel. This gel can retain water under certain pressure without separating. Weight-average molecular weight includes any meaning conventional in the art, primarily referring to the average molecular weight obtained statistically based on mass. Methods for measuring weight-average molecular weight include direct measurement using experimental techniques such as gel permeation chromatography (GPC) or physical methods such as light scattering.

[0133] In this application, a highly absorbent resin with a weight-average molecular weight of 100,000 to 500,000 is selected, which is beneficial for forming a material with stable physicochemical properties through various means such as physical adsorption and chemical bonding with the second adsorbent.

[0134] In some embodiments of this application, the weight-average molecular weight of the superabsorbent resin is 100,000, 100,500, 101,000, 102,000, 103,000, 104,000, 105,000, 106,000, 107,000, 108,000, 109,000, 110,000, 120,000, 130,000, 140,000, 150,000, 160,000, 170 The value is any one of the following: 000, 180000, 190000, 200000, 220000, 240000, 260000, 280000, 300000, 320000, 340000, 360000, 380000, 400000, 420000, 440000, 460000, 480000, 500000, or any one of the values ​​in the above range.

[0135] In some embodiments of this application, the superabsorbent resin includes any one or more of polyacrylate and its modified compounds, starch-acrylate polymers and their derivatives, starch-acrylonitrile polymers and their derivatives, starch-acrylamide polymers and their derivatives, and acrylamide-acrylonitrile-acrylic acid terpolymers and their derivatives.

[0136] The polyacrylates and their modified compounds in this application include one or both of polyacrylates and polyacrylate superabsorbent resins; wherein, the polyacrylate includes any one or more of the ammonium, potassium, and sodium salts of one or two polymers of acrylic acid and / or methacrylic acid; the polyacrylate superabsorbent resin includes a polymer formed from acrylic acid and a vinyl compound; the vinyl compound includes compounds having one or more vinyl functional groups, including but not limited to ethylene, vinyl chloride, styrene, etc. The amount of acrylic acid and the vinyl compound used includes any content relationship conventional in the art. For example, the mass percentage of acrylic acid in the polymer is any one of 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 99%, or any value within the above range.

[0137] The starch-acrylate polymers and their derivatives in this application include products obtained by polymerizing starch with partially neutralized acrylic acid. Starch is the most abundant naturally occurring high-molecular-weight carbohydrate in nature. Industrially, it is mainly produced from cereal crops (such as corn and wheat) and tuber crops (such as potatoes and cassava). If the obtained starch product is not modified, its chemical structure and properties remain the same as when it exists in the raw material, and it does not change during the production process; this is called native starch. Based on the molecular structure, starch includes amylose and amylopectin; starch molecules have numerous hydroxyl groups and are highly hydrophilic. Polymerization is performed using polysaccharides in starch with one or more of acrylic acid and / or methacrylic acid to form any one or more of ammonium salts, potassium salts, and sodium salts. The amount of starch and acrylic acid used includes any content relationship conventional in the art. For example, the mass percentage of acrylic acid in the polymer can be any of 1%, 2%, 3%, 4%, 5%, 10%, 20%, 30%, 40%, or 50%, or any value within the above range.

[0138] The starch-acrylonitrile polymers and their derivatives in this application include copolymers of starch grafted with acrylonitrile formed by ionic or free radical grafting. Since the nitrile groups are hydrophobic, subsequent saponification and hydrolysis with an alkaline aqueous solution forms hydrophilic groups such as amides, carboxylic acids, or carboxylates to generate derivatives. The amounts of starch and acrylonitrile used include any content relationship conventional in the art. For example, the mass percentage of acrylonitrile in the polymer can be any of 1%, 2%, 3%, 4%, 5%, 10%, 20%, or 30%, or any value within the aforementioned range.

[0139] The starch-acrylamide polymer and its derivatives in this application are formed in a similar manner to starch-acrylate polymers. These starch-acrylamide polymers and their derivatives involve polymerizing polysaccharides from starch with one or both of acrylic acid and / or methacrylic acid, without the need for alkali neutralization or saponification. The amount of starch to acrylamide includes any content relationship conventional in the art. For example, acrylamide may be present in any of the following mass percentages of the polymer: 1%, 2%, 3%, 4%, 5%, 10%, 20%, 30%, 40%, 50%, or any value within the aforementioned range.

[0140] The acrylamide-acrylonitrile-acrylic acid terpolymer and its derivatives in this application comprise copolymers formed by the polymerization of acrylic acid and / or methacrylic acid, acrylamide, and acrylonitrile under the action of a crosslinking agent. The amounts of the three monomers used include any content relationship conventional in the art. For example, the molar ratio between acrylic acid and / or methacrylic acid, acrylamide, and acrylonitrile is (10–20):(3–5):(5–8).

[0141] The superabsorbent resins listed in this application possess a cross-linked structure with an internal three-dimensional network structure. Numerous ionic groups are distributed within this network. Water molecules enter this network structure and are adsorbed and fixed within the network by bonding with these ions. Due to the elasticity of the network, it can accommodate a large number of water molecules. When the cross-linking density is high, the extension of the resin molecular chains is restricted, leading to a decrease in water absorption. To control the cross-linking density, this application selects to control the weight-average molecular weight of the superabsorbent resin.

[0142] In some embodiments of this application, the volumetric particle size distribution Dv50 of silica gel and its modified compounds is 1.0 μm to 2.7 μm.

[0143] The silica gel and its modified compounds in this application include inorganic silica gel and compounds obtained by modifying inorganic silica gel. The chemical formula of inorganic silica gel is xSiO2·yH2O, which has a strong adsorption capacity. Since the surface of inorganic silica gel contains a large number of active silanol functional groups, it can be modified by using modifiers such as silane coupling agents, organochlorosilanes, alcohols, amino compounds, sulfur-containing compounds, and phosphorus-containing compounds. Modification also includes using heavy metal ions to chelate with it, thereby improving the adsorption properties of inorganic silica gel.

[0144] The volumetric particle size distribution Dv50 in this application includes particles larger than its diameter accounting for 50% of the total volume, and particles smaller than its diameter also accounting for 50% of the total volume. Also known as the median diameter, it is typically used to represent the average particle size. It can be measured using conventional methods in the art, such as using a particle size analyzer to determine the particle size distribution and then obtaining the result statistically. In these embodiments, this application selects to measure it using laser diffraction particle size analysis, specifically referring to standard GB / T19077-2016 to obtain the particle size distribution map, and then calculating the result.

[0145] The silica gel and its modified compounds used in this application have an average particle size in the micrometer range and strong water absorption.

[0146] In these embodiments, this application discloses that the average particle size of silica gel and its modified compounds satisfies any one of 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, and 2.7 μm, or any one of the above range values.

[0147] In some embodiments of this application, the average pore size of silica gel and its modified compounds is 6 nm to 15 nm.

[0148] The silica gel and its modified compounds in this application possess a porous structure. Generally, the pore size of mesopores is between 2 nm and 50 nm. The average pore size of the silica gel and its modified compounds in this application is 6 nm to 15 nm, thus it can be inferred that their interior is mainly composed of mesopores. The average pore size of this porous structure can be measured using any method conventional in the art. For example, the distribution of each pore can be measured using conventional testing instruments in the art, and the number of each pore can be obtained statistically. Then, the average pore size can be calculated using mathematical functions. The pore volume and specific surface area of ​​silica gel and its modified compounds can also be obtained by using adsorption and desorption isotherms. Based on the relevant pore model, the average pore diameter is obtained by dividing the pore volume by the specific surface area and multiplying by the model coefficient. For example, using an ASAP2460 physical adsorption analyzer, the dried and degassed silica gel and its modified compounds samples are placed in liquid nitrogen. Different test pressures are adjusted to measure the amount of nitrogen adsorbed, and adsorption and desorption isotherms are plotted. Then, the pore volume and specific surface area of ​​silica gel and its modified compounds are obtained from the adsorption and desorption isotherms, and the average pore diameter of silica gel and its modified compounds is calculated.

[0149] In these embodiments, this application discloses that the average pore size of silica gel and its modified compounds is any one of 6nm, 6.5nm, 7nm, 7.5nm, 8nm, 8.5nm, 9nm, 9.5nm, 10nm, 10.5nm, 11nm, 11.5nm, 12nm, 12.5nm, 13nm, 13.5nm, 14nm, 14.5nm, and 15nm, or any one of the above range values.

[0150] In some embodiments of this application, the specific surface area (BET) of silica gel and its modified compounds is 200 m². 2 / g~700m 2 / g.

[0151] As described above, the specific surface area (BET) of silica gel and its modified compounds can be obtained using adsorption and desorption isotherms. For example, using an ASAP2460 physical adsorption analyzer, according to GB / T19587-2017: place the dried and degassed silica gel and its modified compounds samples in liquid nitrogen, adjust different test pressures, measure the amount of nitrogen adsorbed, and plot the adsorption and desorption isotherms. The specific surface area (BET) of silica gel and its modified compounds can be calculated based on these adsorption and desorption isotherms.

[0152] This application discloses in these embodiments that the specific surface area (BET) of silica gel and its modified compounds is 200 m². 2 / g、220m 2 / g、250m 2 / g、280m 2 / g、300m 2 / g、320m 2 / g, 350m 2 / g、380m 2 / g、400m 2 / g、420m 2 / g、450m 2 / g、480m 2 / g、500m 2 / g、520m 2 / g、550m 2 / g、580m 2 / g、600m 2 / g、620m 2 / g、650m 2 / g、680m 2 / g、700m 2 Any one of / g or any one of the above range values.

[0153] In some embodiments of this application, the pore volume of silica gel and its modified compounds is 1.05 cm³. 3 / g~2.0cm 3 / g.

[0154] In this application, pore volume refers to pore size. As mentioned above, the pore volume of silica gel and its modified compounds can be obtained using adsorption and desorption isotherms. For example, using an ASAP2460 physical adsorption analyzer, according to GB / T19587-2017: place the dried and degassed silica gel and its modified compounds samples in liquid nitrogen, adjust different test pressures, measure the amount of nitrogen adsorbed, and plot the adsorption and desorption isotherms. The pore volume of silica gel and its modified compounds can be calculated based on these adsorption and desorption isotherms.

[0155] This application discloses in these embodiments that the pore volume of silica gel and its modified compounds is 1.05 cm³. 3 / g, 1.1cm 3 / g, 1.15cm 3 / g, 1.2cm 3 / g, 1.25cm 3 / g, 1.3cm 3 / g, 1.35cm 3 / g, 1.4cm 3 / g, 1.45cm 3 / g, 1.5cm 3 / g, 1.55cm 3 / g, 1.6cm 3 / g, 1.65cm 3 / g, 1.7cm 3 / g, 1.75cm3 / g, 1.8cm 3 / g, 1.85cm 3 / g, 1.9cm 3 / g, 1.95cm 3 / g, 2.0cm 3 Any one of / g or any one of the above range values.

[0156] This application discloses in these embodiments that the volumetric particle size distribution (Dv50) of silica gel and its modified compounds is 1.0 μm to 2.7 μm, the average pore size is 6 nm to 15 nm, and the specific surface area (BET) is 200 m². 2 / g~700m 2 / g, pore volume 1.05cm 3 / g~2.0cm 3 / g, to better utilize the water absorption properties of silica gel and its modified compounds.

[0157] In some embodiments of this application, the average pore size of the aluminum phosphate molecular sieve is 0.2 nm to 2 nm.

[0158] As described above, the aluminum phosphate molecular sieve of this application is a material with sieving properties. Its structure consists of an interconnected framework of aluminum, oxygen, and phosphorus ions. In addition to oxygen tetrahedral coordination, the aluminum ions also possess oxygen pentacoordinates and oxygen hexacoordinates, thus forming a framework structure that cannot be achieved by silicon-aluminum molecular sieves. The material possesses a regular and uniform pore structure, which is used to adsorb gas or liquid molecules.

[0159] The aluminum phosphate molecular sieve in this application has a porous structure. Generally, the pore size of mesopores is between 2 nm and 50 nm, while the pore size of micropores is smaller than that of mesopores. The average pore size of the aluminum phosphate molecular sieve in this application is 0.2 nm to 2 nm, so it can be inferred that its interior is mainly composed of micropores. The method for measuring the average pore size of this porous structure is the same as that for silica gel and its modified compounds mentioned above, and will not be elaborated here.

[0160] In some embodiments, this application discloses that the average pore size of the aluminum phosphate molecular sieve is any one of 0.2nm, 0.3nm, 0.4nm, 0.5nm, 0.6nm, 0.7nm, 0.8nm, 0.9nm, 1.0nm, 1.1nm, 1.2nm, 1.3nm, 1.4nm, 1.5nm, 1.6nm, 1.7nm, 1.8nm, 1.9nm, and 2.0nm, or any one of the above range values.

[0161] In some embodiments of this application, the specific surface area (BET) of the aluminum phosphate molecular sieve is 100 m². 2 / g~300m 2 / g.

[0162] As mentioned above, the specific surface area BET of the aluminum phosphate molecular sieve of this application can be obtained by adsorption and desorption isotherms, as detailed in the description of silica gel and its modified compounds, which will not be repeated here.

[0163] This application discloses in these embodiments that the specific surface area (BET) of the aluminum phosphate molecular sieve is 100 m². 2 / g、120m 2 / g, 140m 2 / g、160m 2 / g、180m 2 / g、200m 2 / g、220m 2 / g、240m 2 / g、260m 2 / g、280m 2 / g、300m 2 Any one of / g or any one of the above range values.

[0164] In some embodiments of this application, the pore volume of the aluminum phosphate molecular sieve is 0.026 cm³. 3 / g~0.09cm 3 / g.

[0165] In this application, pore volume refers to the pore volume, and the specific testing method is as described above for silica gel and its modified compounds, which will not be repeated here.

[0166] The pore volume of the aluminum phosphate molecular sieve in this application is 0.026 cm³. 3 / g, 0.027cm 3 / g, 0.03cm 3 / g, 0.032cm 3 / g, 0.034cm 3 / g, 0.036cm 3 / g, 0.038cm 3 / g, 0.040cm 3 / g, 0.042cm 3 / g, 0.044cm 3 / g, 0.046cm 3 / g, 0.05cm 3 / g, 0.055cm 3 / g, 0.06cm 3 / g, 0.065cm 3 / g, 0.07cm 3 / g, 0.075cm 3 / g, 0.08cm 3 / g, 0.085cm3 / g, 0.09cm 3 Any one of / g or any one of the above range values.

[0167] The method for preparing aluminum phosphate molecular sieves provided in this application includes: selecting an organic quaternary ammonium base as a template agent, and then synthesizing it using a phosphorus source and an aluminum source at a certain temperature. This application may also include the use of other template agents. The aluminum source includes, but is not limited to, aluminum salts such as alkyl alumina, aluminum nitrate, aluminum trichloride, aluminum oxide, and aluminum hydroxide. The phosphorus source includes, but is not limited to, organic phosphorus sources and phosphorous acid.

[0168] In some embodiments of this application, the alkali metal salt comprises any one or more of alkali metal chlorides and fluorides; the alkaline earth metal salt comprises any one or more of alkaline earth metal chlorides and fluorides.

[0169] As described above, in the field of inorganic chemistry, alkali metal salts or alkaline earth metal salts refer to salt compounds formed by the combination of positively charged alkali metal ions or alkaline earth metal ions with conventional acid radical anions. Alkali metal ions include, but are not limited to, lithium ions, sodium ions, potassium ions, cesium ions, etc., while alkaline earth metal ions include, but are not limited to, magnesium ions, calcium ions, etc. Acid radical anions include, but are not limited to, chloride ions, phosphate ions, fluoride ions, etc. In some embodiments of this application, it is preferred that the alkali metal salt comprises any one or more of alkali metal chlorides and fluorides; and the alkaline earth metal salt comprises any one or more of alkaline earth metal chlorides and fluorides.

[0170] In some embodiments of this application, the second adsorbent comprises any one or more of lithium chloride (LiCl), sodium chloride (NaCl), potassium chloride (KCl), lithium fluoride (LiF), sodium fluoride (NaF), potassium fluoride (KF), calcium fluoride (CaF), and calcium chloride (CaCl2).

[0171] The types listed in these embodiments are for illustrative purposes only. In fact, when the superabsorbent resin, silica gel and its modified compounds, and aluminum phosphate molecular sieve listed in this application are used as the first adsorbent, the first adsorbent has a porous three-dimensional network structure. Many ionic groups are distributed in this three-dimensional network. These ionic groups can adsorb ions in alkali metal salts or alkaline earth metal salts through physical adsorption or chemical bonding to form a stable material. The ions in this material are combined with water molecules and acid molecules due to ionic bonding. At the same time, the pores of the three-dimensional network structure can also adsorb gas molecules. With the help of the elasticity of the three-dimensional network, water molecules, acid molecules, and gas molecules are stably present inside. Even under certain pressure, they can be maintained without separating out the water, acidic substances, and gases.

[0172] In some embodiments of this application, the porosity of the coating is greater than that of the base film.

[0173] The definition of porosity in this application includes conventional definitions in the field of materials, such as using the number of pores to represent porosity, and the porosity can be calculated using the following test methods, or it can be measured or calculated using other methods conventional in the field;

[0174] For example, after drying, the coated sample is cut into a square specimen of approximately 20mm × 20mm. The thickness and actual side length are measured using a digital micrometer and vernier calipers, and its volume is calculated as V. Its weight is then measured as M0. The square specimen is then immersed in the electrolyte and soaked for 2 hours at room temperature and in air. After soaking, the electrolyte liquid adsorbed on the surface is removed, and its weight is measured as M. t The porosity of the coating then satisfies the following mathematical relationship:

[0175] Porosity = (M) t -M0) / ρ×V×100%;

[0176] In the above mathematical formula, ρ represents the density of the electrolyte, with units of mm. 3 / g, V is the volume of the square sample of the coating, in mm. 3 Weights M0 and M t The unit is g, and the weight measuring instrument is a 0.1 / 1000 balance. The models of the 0.1 / 1000 balance, digital micrometer, and vernier caliper include, but are not limited to, any conventional models in this field.

[0177] The porosity of the coating in this application is greater than that of the base film. On the one hand, this facilitates the adsorption of free moisture, acidic substances (such as hydrofluoric acid), and gas molecules inside the battery, reducing the damage of these substances to the solid electrolyte interface (SEI film) and enabling the secondary battery to simultaneously achieve cycle stability and storage stability. On the other hand, it also helps improve the wetting of the separator with the electrolyte, thereby further improving the cycle life of the secondary battery.

[0178] In some embodiments of this application, the porosity of the coating is 70% to 85%; and / or the porosity of the base film is 30% to 45%.

[0179] In these embodiments, this application provides a coating porosity of any one of 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, or any one of the above ranges.

[0180] In these embodiments, this application provides a base membrane porosity of any one of 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, or any one of the above ranges.

[0181] In some embodiments of this application, the coating is formed on the entire surface of the base film.

[0182] Combination Figure 6a , 6b It is known that the coating 32 is formed on the entire surface of the base film 31, that is, the entire surface of at least one side of the base film 31 is covered with the coating 32.

[0183] In some embodiments of this application, the coating is formed on a portion of the surface of the base film.

[0184] Combination Figure 7a , 7b and Figure 8 As can be seen, coating 32 is formed on a portion of the surface of the base film 31, as illustrated in 7a and 7b. One side surface of the separator film 3 includes a coating area 32a where coating 32 is formed and a blank area 32b where no coating 32 is provided. Along the first direction (the y-axis), the coating area 32a and the blank area 32b are alternately distributed. Figure 8 The diagram illustrates that one side surface of the isolation membrane 3 includes a coating area 32a formed by the coating 32 and a blank area 32b without the coating 32. Along the second direction (the z-axis), the coating area 32a and the blank area 32b are alternately distributed. Figure 7b Only one alternating distribution method is illustrated; other alternating distribution designs are also available in the art. Meanwhile, the orthographic projection shape of the coating area 32a and / or the blank area 32b onto the base film 31 can be a regular shape or an irregular shape, such as a square, circle, or ring.

[0185] In some embodiments of this application, the thickness of the coating is 2% to 50% of the thickness of the base film.

[0186] This application is in Figure 6a The diagram illustrates the thickness direction of the coating, specifically the third direction, the x-axis. The coating thickness includes the distance between the two end faces of the coating along the thickness direction. The specific measurement method involves taking different points at different locations on the separator sample and measuring the distance between the two end faces at each point using a measuring instrument such as a vernier caliper. The average of these distance values ​​is the coating thickness. Similarly, the thickness of the base film includes the distance between the two end faces of the base film along the thickness direction. The specific measurement method is the same as for the coating, and will not be elaborated upon here.

[0187] In some embodiments, this application discloses that the thickness of the coating is any one of 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, or 50% of the thickness of the base film, or any one of the values ​​within the range described above.

[0188] In some embodiments of this application, the coating further comprises a binder, the mass of which is 3% to 10% of the mass of the first adsorbent; and / or the binder comprises any one or more of lithium metasilicate, organoboronic acid, polyvinyl alcohol, styrene-butadiene rubber, carboxymethyl cellulose, polyacrylic acid, polyacrylic acid, polyacrylonitrile, polyacrylate, and polyvinylidene fluoride (PVDF).

[0189] In addition to the adsorbent, the coating of this application also contains a binder, which helps to better load the adsorbent onto the base film. Since the superabsorbent resin in the first adsorbent of this application has a certain degree of adhesiveness, compared with the case where the first adsorbent does not contain superabsorbent resin, the amount of binder used in the coating will be relatively less when the first adsorbent contains superabsorbent resin. The specific usage needs to be discussed based on the actual bonding situation.

[0190] In these embodiments, this application discloses that the mass of the binder is any one of 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, or 10% of the mass of the first adsorbent, or any one of the above range values.

[0191] In some embodiments of this application, an insulating layer is also provided between the coating and the base film.

[0192] This application provides an insulating layer between the coating and the base film to reduce the electron conduction capability of the separator and to improve the heat shrinkage resistance and enhance the needle punching strength of the separator.

[0193] This application discloses in these embodiments an insulating layer comprising functional fillers and / or high-temperature resistant organic polymer fibers and binders. The functional fillers comprise one or more of inorganic fillers and polymeric fillers. Inorganic fillers include any one or more of alumina, silica, silicon suboxide, titanium dioxide, zinc oxide, zirconium oxide, cerium oxide, vanadium pentoxide, ferrous oxide, boehmite, hydrotalcite, and metal salts. Polymer fillers include one or more of polytetrafluoroethylene particles, polyethylene microspheres, polystyrene microspheres, and polyurethane microspheres. The high-temperature resistant organic polymer fibers include one or more of aramid fibers, polyacrylonitrile fibers, polyimide fibers, polycarbonate fibers, polyphenylene sulfide fibers, polyetheretherketone fibers, polysulfone fibers, and polyarylate fibers.

[0194] The adhesive in the insulating layer of this application includes at least one of polyvinylidene fluoride (PVDF), polyamide, polyacrylic acid, polyacrylonitrile, sodium polymethyl cellulose, rubber, polyurethane, polyvinyl acetate, epoxy resin, polyimide, phenolic resin, acrylate, polyisobutylene, polyethylene ether, polybutadiene, polyisobutylene, cyanate ester, starch, bismaleimide, polystyrene propylene, isooctyl acrylate, butyl acrylate, methyl methacrylate, and hydroxypropyl methacrylate, wherein the rubber can be natural rubber and / or artificial rubber, such as styrene-butadiene rubber (SBR).

[0195] In some embodiments of this application, the positive electrode sheet includes a positive current collector and a positive electrode film layer located on either side of the surface of the positive current collector. The positive electrode film layer includes a positive electrode active material, and the volumetric particle size distribution Dv50 of the positive electrode active material is < 1.6 μm; and / or the compaction density of the positive electrode film layer is > 2.5 g / cm³. 3 .

[0196] The positive electrode film layer of this application is located on one or both surfaces of the positive electrode current collector. Generally, the positive electrode film layer is located on both surfaces of the positive electrode current collector, and the formation method includes coating or deposition. This application will use both sides as examples in the following sections. The meaning and measurement method of the volumetric particle size distribution Dv50 of the positive electrode active material are the same as those of the aforementioned silica gel and its modified compounds, and will not be repeated here. In these embodiments, this application provides a volumetric particle size distribution Dv50 of the positive electrode active material < 1.6 μm; as those skilled in the art know, materials with smaller particle sizes generally have stronger water absorption. In these embodiments, this application discloses that the volumetric particle size distribution Dv50 of the positive electrode active material is less than 1.6 μm, and can even be at the nanometer scale. For example, for lithium iron phosphate positive electrode active materials, the particle size is generally at the micrometer or nanometer scale, and will not be repeated here. Furthermore, the lower limit value of the volumetric particle size distribution Dv50 of the positive electrode active material is a conventional value in the art, and will not be repeated here. The design method provided in this application is beneficial for improving the moisture content in positive electrode active materials with smaller particle sizes.

[0197] In this application, the compaction density of the positive electrode film can be used to characterize the energy density of the material; however, the compaction density of the positive electrode film is used to evaluate the overall compaction density of the positive electrode sheet. The compaction density of the positive electrode film = areal density of the positive electrode film / thickness of the positive electrode film. The thickness of the positive electrode film includes the distance between the two end faces of the positive electrode film along the thickness direction. The areal density of the positive electrode film = weight of a single side of the positive electrode film / area of ​​a single side of the positive electrode film. The weight of a single side of the positive electrode film can be obtained by weighing, and the area of ​​a single side of the positive electrode film can be obtained using the area calculation formula based on the shape of the film. In these embodiments, this application lists a compaction density of the positive electrode film > 2.5 g / cm³. 3 The upper limit of the compaction density of the positive electrode film is a conventional value in the art, and will not be elaborated upon in this application.

[0198] In some embodiments of this application, the volumetric particle size distribution of the positive electrode active material satisfies: 1.0 μm ≤ Dv50 < 1.6 μm.

[0199] In some embodiments of this application, the compaction density of the positive electrode film layer satisfies: 2.5 g / cm³. 3 < Compacted density ≤ 3.4 g / cm³ 3 .

[0200] In some embodiments of this application, the negative electrode sheet includes a negative current collector and a negative electrode film layer located on either side of the surface of the negative current collector, wherein the compaction density of the negative electrode film layer is >1.65 g / cm³. 3 .

[0201] Similar to the above description of the positive electrode film, the compaction density of the negative electrode film can be used to characterize the energy density of the material. The meaning and measurement method of the compaction density of the negative electrode film are the same as those for the positive electrode film. In these embodiments, this application lists a negative electrode film with a compaction density > 1.65 g / cm³. 3 The upper limit of the compaction density of the negative electrode film is a conventional value in the art, and will not be elaborated upon in this application.

[0202] In some embodiments of this application, the compaction density of the negative electrode film layer satisfies: 1.65 g / cm³ 3 < Compacted density ≤ 2.0 g / cm³ 3 .

[0203] In some embodiments of this application, the battery further includes an electrolyte, which includes one or more of carboxylic acid ester compounds and ether compounds.

[0204] The carboxylic acid ester compounds of this application include one or more of ethyl acetate (EA), methyl acetate (MA), ethyl propionate (EP), propyl acetate (PA), methyl propionate (MP), methyl butyrate (MB), ethyl butyrate (EB), and 1,4-butyrolactone (GBL).

[0205] The ether compounds of this application include at least one of tetrahydrofuran, dimethyltetrahydrofuran, tetrahydropyran, dimethyltetrahydropyran, 1,2-dimethoxyethane, dipropylene glycol dimethyl ether, or dimethyl phthalate.

[0206] Separating membrane

[0207] This application provides a separation membrane comprising a base membrane and a coating located on at least one side surface of the base membrane; the coating comprises a first adsorbent and a second adsorbent; the first adsorbent comprises one or more of a superabsorbent resin, silica gel and its modified compounds, and aluminum phosphate molecular sieve; the second adsorbent comprises one or more of an alkali metal salt or an alkaline earth metal salt; at least a portion of the second adsorbent is located on the surface and inside of the first adsorbent.

[0208] The separator of this application comprises a base film and a coating located on at least one surface of the base film. "At least one side" can refer to either one surface or both surfaces. This application also includes the provision of other film layers between the base film and the coating, which will be described in detail later. Meanwhile, the coating on the surface of the base film can be formed using any method conventional in the art, such as coating or deposition. Specifically, a first adsorbent and a second adsorbent are dispersed in a non-aqueous organic solvent, such as N-methylpyrrolidone, to form a uniformly dispersed slurry. This slurry is then coated onto both surfaces of the base film, and after drying, the coating is obtained.

[0209] The coating of this application includes a first adsorbent and a second adsorbent. Clearly, both the first and second adsorbents serve the technical purpose of absorbing free moisture inside the battery. Specifically, the first adsorbent comprises one or more of a superabsorbent resin, silica gel and its modified compounds, and aluminum phosphate molecular sieves; the second adsorbent comprises a chloride.

[0210] The superabsorbent resin of this application refers to a polymer with a certain degree of cross-linking. This polymer can quickly absorb water hundreds of times its own weight to form a gel. This gel can retain moisture and not separate under certain pressure.

[0211] The silica gel and its modified compounds in this application refer to inorganic silica gel or modified inorganic silica gel. Inorganic silica gel has the chemical formula xSiO2·yH2O and possesses strong adsorption capacity. Since the surface of inorganic silica gel contains a large number of active silanol functional groups, it can be modified using modifiers such as silane coupling agents, organochlorosilanes, alcohols, amino compounds, sulfur-containing compounds, and phosphorus-containing compounds. Modification also includes using heavy metal ions to chelate with it, thereby improving the adsorption properties of inorganic silica gel.

[0212] The aluminum phosphate molecular sieve of this application is a material with sieving properties. Its structure consists of an interconnected framework of aluminum, oxygen, and phosphorus ions. In addition to oxygen tetrahedral coordination, the aluminum ions also possess oxygen pentacoordinates and oxygen hexacoordinates, thus forming a framework structure that cannot be achieved by silicon-aluminum molecular sieves. The material possesses a regular and uniform pore structure, which is used to adsorb gas or liquid molecules.

[0213] In the field of inorganic chemistry, the alkali metal salts or alkaline earth metal salts of this application refer to salt compounds formed by the combination of positively charged alkali metal ions or alkaline earth metal ions with conventional acid radical anions. Alkali metal ions include, but are not limited to, lithium ions, sodium ions, potassium ions, cesium ions, etc., while alkaline earth metal ions include, but are not limited to, magnesium ions, calcium ions, etc. Acid radical anions include, but are not limited to, chloride ions, phosphate ions, fluoride ions, etc. The second adsorbent itself possesses a certain degree of water absorption. Furthermore, the second adsorbent is easily loaded onto the surface and interior of the first adsorbent. The first adsorbent acts as the host, and the second adsorbent as the guest. The host and guest combine through various mechanisms such as physical adsorption and chemical bonding to form a physicochemically stable material. This material can adsorb free water, acidic substances (such as hydrofluoric acid), and gas molecules inside the battery, reducing the damage of these substances to the battery's solid electrolyte interface (SEI film), enabling the secondary battery to simultaneously achieve cycle stability and storage stability.

[0214] In some embodiments of this application, the mass of the second adsorbent is 10% to 30% of the mass of the first adsorbent.

[0215] The method for measuring the mass of the second adsorbent and the mass of the first adsorbent in this application includes obtaining a cross-sectional sample of the isolation membrane, distinguishing the base membrane and the coating based on the porosity, obtaining the elemental distribution in the coating using a scanning electron microscope (SEM) and an energy-dispersive X-ray spectroscopy (EDS), and then calculating the mass of the first adsorbent and the mass of the second adsorbent, and then calculating the percentage of the mass of the second adsorbent to the mass of the first adsorbent.

[0216] The second adsorbent in this application has a mass of 10% to 30% of the first adsorbent, which allows the first adsorbent to be fully loaded on the surface and inside of the first adsorbent, thereby improving the structural stability of the combined material and facilitating its adsorption characteristics for free water, acidic substances (such as hydrofluoric acid), and gas molecules inside the battery.

[0217] In these embodiments, this application discloses that the mass of the second adsorbent is any one of 10%–30%, 11%–30%, 12%–30%, 13%–30%, 14%–30%, 15%–30%, 16%–30%, 17%–30%, 18%–30%, 19%–30%, 20%–30%, 21%–30%, 22%–30%, 23%–30%, 24%–30%, 25%–30%, 26%–30%, 27%–30%, 28%–30%, 29%–30%, 10%–20%, 10%–25%, or 20%–30% of the mass of the first adsorbent.

[0218] In these embodiments, this application discloses that the mass of the second adsorbent is any one of 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, or 30% of the mass of the first adsorbent, or any one of the ranges described above.

[0219] In some embodiments of this application, the weight-average molecular weight of the superabsorbent resin is 100,000 to 500,000.

[0220] The superabsorbent resin in this application refers to a polymer with a certain degree of cross-linking, which can quickly absorb hundreds of times its own weight in water to form a gel. This gel can retain water under certain pressure without separating. Weight-average molecular weight includes any meaning conventional in the art, primarily referring to the average molecular weight obtained statistically based on mass. Methods for measuring weight-average molecular weight include direct measurement using experimental techniques such as gel permeation chromatography (GPC) or physical methods such as light scattering.

[0221] In this application, a highly absorbent resin with a weight-average molecular weight of 100,000 to 500,000 is selected, which is beneficial for forming a material with stable physicochemical properties through various means such as physical adsorption and chemical bonding with the second adsorbent.

[0222] In some embodiments of this application, the weight-average molecular weight of the superabsorbent resin is 100,000, 100,500, 101,000, 102,000, 103,000, 104,000, 105,000, 106,000, 107,000, 108,000, 109,000, 110,000, 120,000, 130,000, 140,000, 150,000, 160,000, 170 The value is any one of the following: 000, 180000, 190000, 200000, 220000, 240000, 260000, 280000, 300000, 320000, 340000, 360000, 380000, 400000, 420000, 440000, 460000, 480000, 500000, or any one of the values ​​in the above range.

[0223] In some embodiments of this application, the superabsorbent resin includes any one or more of polyacrylate and its modified compounds, starch-acrylate polymers and their derivatives, starch-acrylonitrile polymers and their derivatives, starch-acrylamide polymers and their derivatives, and acrylamide-acrylonitrile-acrylic acid terpolymers and their derivatives.

[0224] The polyacrylates and their modified compounds in this application include one or both of polyacrylates and polyacrylate superabsorbent resins; wherein, the polyacrylate includes any one or more of the ammonium, potassium, and sodium salts of one or two polymers of acrylic acid and / or methacrylic acid; the polyacrylate superabsorbent resin includes a polymer formed from acrylic acid and a vinyl compound; the vinyl compound includes compounds having one or more vinyl functional groups, including but not limited to ethylene, vinyl chloride, styrene, etc. The amount of acrylic acid and the vinyl compound used includes any content relationship conventional in the art. For example, the mass percentage of acrylic acid in the polymer is any one of 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 99%, or any value within the above range.

[0225] The starch-acrylate polymers and their derivatives in this application include products obtained by polymerizing starch with partially neutralized acrylic acid. Starch is the most abundant naturally occurring high-molecular-weight carbohydrate in nature. Industrially, it is mainly produced from cereal crops (such as corn and wheat) and tuber crops (such as potatoes and cassava). If the obtained starch product has not undergone denaturation treatment, its chemical structure and properties remain the same as when it existed in the raw material, and it has not changed during the production process; this is called native starch. Based on the molecular structure, starch includes amylose and amylopectin; starch molecules have numerous hydroxyl groups and are highly hydrophilic. Polymerization is performed using polysaccharides in starch with one or more of acrylic acid and / or methacrylic acid to form any one or more of ammonium salts, potassium salts, and sodium salts. The amount of starch and acrylic acid used includes any content relationship conventional in the art. For example, the mass percentage of acrylic acid in the polymer can be any of 1%, 2%, 3%, 4%, 5%, 10%, 20%, 30%, 40%, or 50%, or any value within the above range.

[0226] The starch-acrylonitrile polymers and their derivatives in this application include copolymers of starch grafted with acrylonitrile formed by ionic or free radical grafting. Since the nitrile groups are hydrophobic, subsequent saponification and hydrolysis with an alkaline aqueous solution forms hydrophilic groups such as amides, carboxylic acids, or carboxylates to generate derivatives. The amounts of starch and acrylonitrile used include any content relationship conventional in the art. For example, the mass percentage of acrylonitrile in the polymer can be any of 1%, 2%, 3%, 4%, 5%, 10%, 20%, or 30%, or any value within the aforementioned range.

[0227] The starch-acrylamide polymer and its derivatives in this application are formed in a similar manner to starch-acrylate polymers. These starch-acrylamide polymers and their derivatives involve polymerizing polysaccharides from starch with one or both of acrylic acid and / or methacrylic acid, without the need for alkali neutralization or saponification. The amount of starch to acrylamide includes any content relationship conventional in the art. For example, acrylamide may be present in any of the following mass percentages of the polymer: 1%, 2%, 3%, 4%, 5%, 10%, 20%, 30%, 40%, 50%, or any value within the aforementioned range.

[0228] The acrylamide-acrylonitrile-acrylic acid terpolymer and its derivatives in this application comprise copolymers formed by the polymerization of acrylic acid and / or methacrylic acid, acrylamide, and acrylonitrile under the action of a crosslinking agent. The amounts of the three monomers used include any content relationship conventional in the art. For example, the molar ratio between acrylic acid and / or methacrylic acid, acrylamide, and acrylonitrile is (10–20):(3–5):(5–8).

[0229] The superabsorbent resins listed in this application possess a cross-linked structure with an internal three-dimensional network structure. Numerous ionic groups are distributed within this network. Water molecules enter this network structure and are adsorbed and fixed within the network by bonding with these ions. Due to the elasticity of the network, it can accommodate a large number of water molecules. When the cross-linking density is high, the extension of the resin molecular chains is restricted, leading to a decrease in water absorption. To control the cross-linking density, this application selects to control the weight-average molecular weight of the superabsorbent resin.

[0230] In some embodiments of this application, the volumetric particle size distribution Dv50 of silica gel and its modified compounds is 1.0 μm to 2.7 μm.

[0231] The silica gel and its modified compounds in this application include inorganic silica gel and compounds obtained by modifying inorganic silica gel. The chemical formula of inorganic silica gel is xSiO2·yH2O, which has a strong adsorption capacity. Since the surface of inorganic silica gel contains a large number of active silanol functional groups, it can be modified by using modifiers such as silane coupling agents, organochlorosilanes, alcohols, amino compounds, sulfur-containing compounds, and phosphorus-containing compounds. Modification also includes using heavy metal ions to chelate with it, thereby improving the adsorption properties of inorganic silica gel.

[0232] The volumetric particle size distribution Dv50 in this application includes particles larger than its diameter accounting for 50% of the total volume, and particles smaller than its diameter also accounting for 50% of the total volume. Also known as the median diameter, it is typically used to represent the average particle size. It can be measured using conventional methods in the art, such as using a particle size analyzer to determine the particle size distribution and then obtaining the result statistically. In these embodiments, this application selects to measure it using laser diffraction particle size analysis, specifically referring to standard GB / T19077-2016 to obtain the particle size distribution map, and then calculating the result.

[0233] The silica gel and its modified compounds used in this application have an average particle size in the micrometer range and strong water absorption.

[0234] In these embodiments, this application discloses that the average particle size of silica gel and its modified compounds satisfies any one of 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, and 2.7 μm, or any one of the above range values.

[0235] In some embodiments of this application, the average pore size of silica gel and its modified compounds is 6 nm to 15 nm.

[0236] The silica gel and its modified compounds in this application possess a porous structure. Generally, the pore size of mesopores is between 2 nm and 50 nm. The average pore size of the silica gel and its modified compounds in this application is 6 nm to 15 nm, thus it can be inferred that their interior is mainly composed of mesopores. The average pore size of this porous structure can be measured using any method conventional in the art. For example, the distribution of each pore can be measured using conventional testing instruments in the art, and the number of each pore can be obtained statistically. Then, the average pore size can be calculated using mathematical functions. The pore volume and specific surface area of ​​silica gel and its modified compounds can also be obtained by using adsorption and desorption isotherms. Based on the relevant pore model, the average pore diameter is obtained by dividing the pore volume by the specific surface area and multiplying by the model coefficient. For example, using an ASAP2460 physical adsorption analyzer, the dried and degassed silica gel and its modified compounds samples are placed in liquid nitrogen. Different test pressures are adjusted to measure the amount of nitrogen adsorbed, and adsorption and desorption isotherms are plotted. Then, the pore volume and specific surface area of ​​silica gel and its modified compounds are obtained from the adsorption and desorption isotherms, and the average pore diameter of silica gel and its modified compounds is calculated.

[0237] In these embodiments, this application discloses that the average pore size of silica gel and its modified compounds is any one of 6nm, 6.5nm, 7nm, 7.5nm, 8nm, 8.5nm, 9nm, 9.5nm, 10nm, 10.5nm, 11nm, 11.5nm, 12nm, 12.5nm, 13nm, 13.5nm, 14nm, 14.5nm, and 15nm, or any one of the above range values.

[0238] In some embodiments of this application, the specific surface area (BET) of silica gel and its modified compounds is 200 m². 2 / g~700m 2 / g.

[0239] As described above, the specific surface area (BET) of silica gel and its modified compounds can be obtained using adsorption and desorption isotherms. For example, using an ASAP2460 physical adsorption analyzer, according to GB / T19587-2017: place the dried and degassed silica gel and its modified compounds samples in liquid nitrogen, adjust different test pressures, measure the amount of nitrogen adsorbed, and plot the adsorption and desorption isotherms. The specific surface area (BET) of silica gel and its modified compounds can be calculated based on these adsorption and desorption isotherms.

[0240] This application discloses in these embodiments that the specific surface area (BET) of silica gel and its modified compounds is 200 m². 2 / g、220m 2 / g、250m 2 / g、280m 2 / g、300m 2 / g、320m 2 / g, 350m 2 / g、380m 2 / g、400m 2 / g、420m 2 / g、450m 2 / g、480m 2 / g、500m 2 / g、520m 2 / g、550m 2 / g、580m 2 / g、600m 2 / g、620m 2 / g、650m 2 / g、680m 2 / g、700m 2 Any one of / g or any one of the above range values.

[0241] In some embodiments of this application, the pore volume of silica gel and its modified compounds is 1.05 cm³. 3 / g~2.0cm 3 / g.

[0242] In this application, pore volume refers to pore size. As mentioned above, the pore volume of silica gel and its modified compounds can be obtained using adsorption and desorption isotherms. For example, using an ASAP2460 physical adsorption analyzer, according to GB / T19587-2017: place the dried and degassed silica gel and its modified compounds samples in liquid nitrogen, adjust different test pressures, measure the amount of nitrogen adsorbed, and plot the adsorption and desorption isotherms. The pore volume of silica gel and its modified compounds can be calculated based on these adsorption and desorption isotherms.

[0243] This application discloses in these embodiments that the pore volume of silica gel and its modified compounds is 1.05 cm³. 3 / g, 1.1cm 3 / g, 1.15cm 3 / g, 1.2cm 3 / g, 1.25cm 3 / g, 1.3cm 3 / g, 1.35cm 3 / g, 1.4cm 3 / g, 1.45cm 3 / g, 1.5cm 3 / g, 1.55cm 3 / g, 1.6cm 3 / g, 1.65cm 3 / g, 1.7cm 3 / g, 1.75cm3 / g, 1.8cm 3 / g, 1.85cm 3 / g, 1.9cm 3 / g, 1.95cm 3 / g, 2.0cm 3 Any one of / g or any one of the above range values.

[0244] This application discloses in these embodiments that the volumetric particle size distribution (Dv50) of silica gel and its modified compounds is 1.0 μm to 2.7 μm, the average pore size is 6 nm to 15 nm, and the specific surface area (BET) is 200 m². 2 / g~700m 2 / g, pore volume 1.05cm 3 / g~2.0cm 3 / g, to better utilize the water absorption properties of silica gel and its modified compounds.

[0245] In some embodiments of this application, the average pore size of the aluminum phosphate molecular sieve is 0.2 nm to 2 nm.

[0246] As described above, the aluminum phosphate molecular sieve of this application is a material with sieving properties. Its structure consists of an interconnected framework of aluminum, oxygen, and phosphorus ions. In addition to oxygen tetrahedral coordination, the aluminum ions also possess oxygen pentacoordinates and oxygen hexacoordinates, thus forming a framework structure that cannot be achieved by silicon-aluminum molecular sieves. The material possesses a regular and uniform pore structure, which is used to adsorb gas or liquid molecules.

[0247] The aluminum phosphate molecular sieve in this application has a porous structure. Generally, the pore size of mesopores is between 2 nm and 50 nm, while the pore size of micropores is smaller than that of mesopores. The average pore size of the aluminum phosphate molecular sieve in this application is 0.2 nm to 2 nm, so it can be inferred that its interior is mainly composed of micropores. The method for measuring the average pore size of this porous structure is the same as that for silica gel and its modified compounds mentioned above, and will not be elaborated here.

[0248] In some embodiments, this application discloses that the average pore size of the aluminum phosphate molecular sieve is any one of 0.2nm, 0.3nm, 0.4nm, 0.5nm, 0.6nm, 0.7nm, 0.8nm, 0.9nm, 1.0nm, 1.1nm, 1.2nm, 1.3nm, 1.4nm, 1.5nm, 1.6nm, 1.7nm, 1.8nm, 1.9nm, and 2.0nm, or any one of the above range values.

[0249] In some embodiments of this application, the specific surface area (BET) of the aluminum phosphate molecular sieve is 100 m². 2 / g~300m 2 / g.

[0250] As mentioned above, the specific surface area BET of the aluminum phosphate molecular sieve of this application can be obtained by adsorption and desorption isotherms, as detailed in the description of silica gel and its modified compounds, which will not be repeated here.

[0251] This application discloses in these embodiments that the specific surface area (BET) of the aluminum phosphate molecular sieve is 100 m². 2 / g、120m 2 / g, 140m 2 / g、160m 2 / g、180m 2 / g、200m 2 / g、220m 2 / g、240m 2 / g、260m 2 / g、280m 2 / g、300m 2 Any one of / g or any one of the above range values.

[0252] In some embodiments of this application, the pore volume of the aluminum phosphate molecular sieve is 0.046 cm³. 3 / g~0.09cm 3 / g.

[0253] In this application, pore volume refers to the pore volume, and the specific testing method is as described above for silica gel and its modified compounds, which will not be repeated here.

[0254] The pore volume of the aluminum phosphate molecular sieve in this application is 0.046 cm³. 3 / g, 0.05cm 3 / g, 0.055cm 3 / g, 0.06cm 3 / g, 0.065cm 3 / g, 0.07cm 3 / g, 0.075cm 3 / g, 0.08cm 3 / g, 0.085cm 3 / g, 0.09cm 3 Any one of / g or any one of the above range values.

[0255] In some embodiments of this application, the alkali metal salt comprises any one or more of alkali metal chlorides and fluorides; the alkaline earth metal salt comprises any one or more of alkaline earth metal chlorides and fluorides.

[0256] As described above, in the field of inorganic chemistry, alkali metal salts or alkaline earth metal salts refer to salt compounds formed by the combination of positively charged alkali metal ions or alkaline earth metal ions with conventional acid radical anions. Alkali metal ions include, but are not limited to, lithium ions, sodium ions, potassium ions, cesium ions, etc., while alkaline earth metal ions include, but are not limited to, magnesium ions, calcium ions, etc. Acid radical anions include, but are not limited to, chloride ions, phosphate ions, fluoride ions, etc. In some embodiments of this application, it is preferred that the alkali metal salt comprises any one or more of alkali metal chlorides and fluorides; and the alkaline earth metal salt comprises any one or more of alkaline earth metal chlorides and fluorides.

[0257] In some embodiments of this application, the second adsorbent comprises any one or more of lithium chloride (LiCl), sodium chloride (NaCl), potassium chloride (KCl), lithium fluoride (LiF), sodium fluoride (NaF), potassium fluoride (KF), calcium fluoride (CaF), and calcium chloride (CaCl2).

[0258] The types listed in these embodiments are for illustrative purposes only. In fact, when the superabsorbent resin, silica gel and its modified compounds, and aluminum phosphate molecular sieve listed in this application are used as the first adsorbent, the first adsorbent has a porous three-dimensional network structure. Many ionic groups are distributed in this three-dimensional network. These ionic groups can adsorb ions in alkali metal salts or alkaline earth metal salts through physical adsorption or chemical bonding to form a stable material. The ions in this material are combined with water molecules and acid molecules due to ionic bonding. At the same time, the pores of the three-dimensional network structure can also adsorb gas molecules. With the help of the elasticity of the three-dimensional network, water molecules, acid molecules, and gas molecules are stably present inside. Even under certain pressure, they can be maintained without separating out the water, acidic substances, and gases.

[0259] In some embodiments of this application, the porosity of the coating is greater than that of the base film.

[0260] The definition of porosity in this application includes conventional definitions in the field of materials, such as using the number of pores to represent porosity, and the porosity can be calculated using the following test methods, or it can be measured or calculated using other methods conventional in the field;

[0261] For example, after drying, the coated sample is cut into a square specimen of approximately 20mm × 20mm. The thickness and actual side length are measured using a digital micrometer and vernier calipers, and its volume is calculated as V. Its weight is then measured as M0. The square specimen is then immersed in the electrolyte and soaked for 2 hours at room temperature and in air. After soaking, the electrolyte liquid adsorbed on the surface is removed, and its weight is measured as M. t The porosity of the coating then satisfies the following mathematical relationship:

[0262] Porosity = (M) t -M0) / ρ×V×100%;

[0263] In the above mathematical formula, ρ represents the density of the electrolyte, with units of mm. 3 / g, V is the volume of the square sample of the coating, in mm. 3 Weights M0 and M t The unit is g, and the weight measuring instrument is a 0.1 / 1000 balance. The models of the 0.1 / 1000 balance, digital micrometer, and vernier caliper include, but are not limited to, any conventional models in this field.

[0264] The porosity of the coating in this application is greater than that of the base film. On the one hand, this facilitates the adsorption of free moisture, acidic substances (such as hydrofluoric acid), and gas molecules inside the battery, reducing the damage of these substances to the solid electrolyte interface (SEI film) and enabling the secondary battery to simultaneously achieve cycle stability and storage stability. On the other hand, it also helps improve the wetting of the separator with the electrolyte, thereby further improving the cycle life of the secondary battery.

[0265] In some embodiments of this application, the porosity of the coating is 70% to 85%; and / or the porosity of the base film is 30% to 45%.

[0266] In these embodiments, this application provides a coating porosity of any one of 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, or any one of the above ranges.

[0267] In these embodiments, this application provides a base membrane porosity of any one of 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, or any one of the above ranges.

[0268] In some embodiments of this application, the coating is formed on the entire surface of the base film.

[0269] Combination Figure 6a , 6b It is known that the coating 32 is formed on the entire surface of the base film 31, that is, the entire surface of at least one side of the base film 31 is covered with the coating 32.

[0270] In some embodiments of this application, the coating is formed on a portion of the surface of the base film.

[0271] Combination Figure 7a , 7b and Figure 8As can be seen, coating 32 is formed on a portion of the surface of the base film 31, as illustrated in 7a and 7b. One side surface of the separator film 3 includes a coating area 32a where coating 32 is formed and a blank area 32b where no coating 32 is provided. Along the first direction (the y-axis), the coating area 32a and the blank area 32b are alternately distributed. Figure 8 The diagram illustrates that one surface of the isolation membrane 3 includes a coated area 32a formed by the coating 32 and a blank area 32b without the coating 32. Along the second direction (the z-axis), the coated area 32a and the blank area 32b are alternately distributed. Figure 7b Only one alternating distribution method is illustrated; other alternating distribution designs are also available in the art. Meanwhile, the orthographic projection shape of the coating area 32a and / or the blank area 32b onto the base film 31 can be a regular shape or an irregular shape, such as a square, circle, or ring.

[0272] In some embodiments of this application, the thickness of the coating is 2% to 50% of the thickness of the base film.

[0273] This application is in Figure 6a The diagram illustrates the thickness direction of the coating, specifically the third direction, the x-axis. The coating thickness includes the distance between the two end faces of the coating along the thickness direction. The specific measurement method involves taking different points at different locations on the separator sample and measuring the distance between the two end faces at each point using a measuring instrument such as a vernier caliper. The average of these distance values ​​is the coating thickness. Similarly, the thickness of the base film includes the distance between the two end faces of the base film along the thickness direction. The specific measurement method is the same as for the coating, and will not be elaborated upon here.

[0274] In some embodiments, this application discloses that the thickness of the coating is any one of 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, or 50% of the thickness of the base film, or any one of the values ​​within the range described above.

[0275] In some embodiments of this application, the coating further comprises a binder, the mass of which is 3% to 10% of the mass of the first adsorbent; and / or the binder comprises any one or more of lithium metasilicate, organoboronic acid, polyvinyl alcohol, styrene-butadiene rubber, carboxymethyl cellulose, polyacrylic acid, polyacrylic acid, polyacrylonitrile, polyacrylate, and polyvinylidene fluoride (PVDF).

[0276] In addition to the adsorbent, the coating in this application also contains a binder, which helps to better load the adsorbent onto the base film. Since the superabsorbent resin in the first adsorbent of this application has certain adhesive properties, compared to the case where the first adsorbent does not contain superabsorbent resin, the amount of binder used in the coating will be relatively less when the first adsorbent contains superabsorbent resin. Specific usage needs to be discussed based on the actual bonding situation.

[0277] In these embodiments, this application discloses that the mass of the binder is any one of 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, or 10% of the mass of the first adsorbent, or any one of the above range values.

[0278] In some embodiments of this application, an insulating layer is also provided between the coating and the base film.

[0279] This application provides an insulating layer between the coating and the base film to reduce the electron conduction capability of the separator and to improve the heat shrinkage resistance and enhance the needle punching strength of the separator.

[0280] This application discloses in these embodiments an insulating layer comprising functional fillers and / or high-temperature resistant organic polymer fibers and binders. The functional fillers comprise one or more of inorganic fillers and polymeric fillers. Inorganic fillers include any one or more of alumina, silica, silicon suboxide, titanium dioxide, zinc oxide, zirconium oxide, cerium oxide, vanadium pentoxide, ferrous oxide, boehmite, hydrotalcite, and metal salts. Polymer fillers include one or more of polytetrafluoroethylene particles, polyethylene microspheres, polystyrene microspheres, and polyurethane microspheres. The high-temperature resistant organic polymer fibers include one or more of aramid fibers, polyacrylonitrile fibers, polyimide fibers, polycarbonate fibers, polyphenylene sulfide fibers, polyetheretherketone fibers, polysulfone fibers, and polyarylate fibers.

[0281] The adhesive in the insulating layer of this application includes at least one of polyvinylidene fluoride (PVDF), polyamide, polyacrylic acid, polyacrylonitrile, sodium polymethyl cellulose, rubber, polyurethane, polyvinyl acetate, epoxy resin, polyimide, phenolic resin, acrylate, polyisobutylene, polyethylene ether, polybutadiene, polyisobutylene, cyanate ester, starch, bismaleimide, polystyrene propylene, isooctyl acrylate, butyl acrylate, methyl methacrylate, and hydroxypropyl methacrylate, wherein the rubber can be natural rubber and / or artificial rubber, such as styrene-butadiene rubber (SBR).

[0282] In some embodiments, the base film of this application is made from a matrix material, including one or more of polyethylene, polypropylene, poly(p-phenylene terephthalamide), polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, and polyamide. The base film can be a single-layer film or a multilayer composite film, without particular limitation. When the base film is a multilayer composite film, the materials of each layer can be the same or different, without particular limitation. The base film provided in this application has good lithium-ion permeability, which is beneficial to lithium-ion migration.

[0283] [Positive electrode plate]

[0284] According to some embodiments of this application, as described above, the positive electrode sheet includes a positive current collector and a positive electrode film layer located on at least one side surface of the positive current collector. The positive electrode film layer contains a positive electrode active material. The volumetric particle size distribution Dv50 of the positive electrode active material and the compaction density of the positive electrode film layer are as described in the above description of the secondary battery.

[0285] According to some embodiments of this application, when the positive electrode sheet is applied to a lithium-ion battery, the positive electrode active material includes, but is not limited to, one or more combinations of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and lithium olivine-structured lithium phosphate; wherein, the structural formula of the olivine-structured lithium phosphate is: LiFe 1-x-y Mn x M y PO4, 0≤x≤1, 0≤y<1, 0≤x+y≤1, M contains one or more transition metal elements or non-transition metal elements other than Fe and Mn, and M preferably contains one or more of Cr, Mg, Ti, Al, Zn, W, Nb, and Zr. This application specifically includes, but is not limited to, LiCoO2, LiNiO2, LiMnO2, LiMn2O4, and LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM111), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523), LiNi 0.6 CO 0.2 Mn 0.2 O2(NCM622), LiNi 0.8 CO 0.1 Mn 0.1 O2(NCM811), LiNi 0.85 CO 0.15 Al 0.05 One or more of O2, LiFePO4 (LFP), and LiMnPO4.

[0286] According to some embodiments of this application, when the positive electrode sheet is applied to a sodium-ion battery, the positive electrode active material includes, but is not limited to, at least one of sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds. Specifically, in the sodium transition metal oxide, the transition metal can be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, and the sodium transition metal oxide is, for example, Na. x MO2, where M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr, and Cu, and 0 < x ≤ 1. Polyanionic compounds include sodium vanadium trifluorophosphate (Na3V2(PO4)2F3), sodium vanadium fluorophosphate (NaVPO4F), sodium vanadium phosphate (Na3V2(PO4)3), Na4Fe3(PO4)2P2O7, NaFePO4, and one or more of these. Prussian blue compounds are Na... x M1M2(CN)6, wherein M1 and M2 are one or more of Fe, Mn, Co, Ni, Cu, Zn, Cr, Ti, V, Zr, and Ce, and 0 < x ≤ 2.

[0287] According to some embodiments of this application, the positive electrode film layer also includes conductive agents, binders, etc. Conductive agents include, but are not limited to, one or more combinations of graphite, superconducting carbon, carbon black (such as acetylene black, Ketjen black, Super P, etc.), carbon dots, carbon nanotubes, graphene, and carbon nanofibers. Binders include, but are not limited to, one or more combinations of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, sodium alginate, polymethacrylic acid, carboxymethyl chitosan, etc. The positive electrode current collector in this application can be a metal foil or a composite current collector. The metal foil can be an aluminum foil, and the composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. Composite current collectors can be formed by forming metallic materials, such as aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, on polymer substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0288] The method for forming the positive electrode film in this application includes mixing the above-mentioned raw materials with a solvent (such as N-methylpyrrolidone) in a certain mass ratio to form a positive electrode slurry, and uniformly coating the positive electrode slurry onto both sides of the positive electrode current collector; controlling the coating weight on one side to be 0.25g~0.50g / 1540.25mm.2 After drying, it is then compacted to a certain compaction density (2.5 g / cm³) using a cold press. 3 < Compacted density ≤ 3.4 g / cm³ 3 This yields a positive electrode sheet containing a positive electrode film.

[0289] [Negative electrode plate]

[0290] According to some embodiments of this application, as described above, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer located on at least one side surface of the negative electrode current collector. The negative electrode film layer contains a negative electrode active material. The compaction density of the negative electrode active material is as described in the above description of the secondary battery.

[0291] The negative electrode active material in this application comprises carbonaceous materials, including one or more combinations of artificial graphite, natural graphite, soft carbon, and hard carbon. Among these, artificial graphite, natural graphite, soft carbon, and hard carbon encompass any form of material conventional in the art, and include any manufacturer and model conventional in the art. Simultaneously, the negative electrode active material may also comprise silicon-based materials, including one or two of silicon-oxygen materials or silicon-carbon materials. In addition, the negative electrode active material may also comprise silicon-carbon composites, Li-Sn alloys, Li-Sn-O alloys, Sn, SnO, SnO2, TiO2-Li4Ti5O 12 Li-Al alloys are used. However, this application is not limited to these materials; other conventional materials that can be used as negative electrode active materials for lithium-ion or sodium-ion batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0292] The method for preparing artificial graphite in this application includes: providing raw materials, crushing and shaping → granulation → graphitization treatment → surface roughening treatment to obtain artificial graphite material. The raw materials in these embodiments of this application can be one or more of raw coke and calcined coke; preferably, the raw materials include one or more of needle-shaped raw petroleum coke, non-needle-shaped raw petroleum coke, needle-shaped coal-based raw coke, non-needle-shaped coal-based raw coke, calcined needle-shaped coke, and calcined petroleum coke. The crushing in this application can be performed using devices and methods known in the art, such as air jet mills, mechanical mills, or roller mills. During the crushing process, a large number of excessively small particles are usually generated, and sometimes excessively large particles are also generated. Therefore, after crushing, grading can be performed as needed to remove excessively small and excessively large particles from the crushed powder. Grading can obtain granular products with a better particle size distribution, which is beneficial for subsequent molding and / or granulation processes. Grading can be performed using devices and methods known in the art, such as grading sieves, gravity classifiers, or centrifugal classifiers. The shaping in this application can be performed using equipment (e.g., molding machines or other molding equipment) and methods known in the art. For example, polishing the edges of the resulting granular product facilitates subsequent operations and improves the stability of the product. The granulation process in this application includes using equipment known in the art, such as a granulator. A granulator typically includes a stirred reactor and a reactor temperature control module. Furthermore, the median particle size of the resulting product can be controlled by adjusting process conditions during granulation, such as stirring speed, heating rate, granulation temperature, and cooling rate. The graphitization process in this application includes high-temperature graphitization and low-temperature graphitization. In some embodiments, one or both of high-temperature and low-temperature graphitization can be appropriately selected for treatment according to specific needs. Alternatively, high-temperature and / or low-temperature graphitization can be repeated. High-temperature graphitization can yield graphite with an appropriate degree of graphitization and interlayer spacing. Graphite prepared at an appropriate graphitization temperature can achieve an appropriate degree of graphitization and interlayer spacing, thereby enabling the composite artificial graphite to obtain high structural stability and specific capacity. The surface roughening process in this application includes using conventional methods in the art, such as physical methods.

[0293] In addition to the negative electrode active material, the negative electrode film layer of this application also includes binders, conductive agents, dispersants, etc. The binders include, but are not limited to, polyvinyl alcohol, polyethylene glycol, sodium carboxymethyl cellulose, polyethylene oxide, polyacrylic acid, polyacrylamide, sodium alginate, styrene-butadiene rubber (SBR), etc. The conductive agents include any type conventional in the art, such as graphite, superconducting carbon, carbon black (e.g., acetylene black, Ketjen black, Super P, etc.), carbon dots, carbon nanotubes, graphene, and carbon nanofibers, or a combination of two or more of these. The dispersants also include any type conventional in the art, such as cellulose and its salts, specifically including, but not limited to, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, etc.

[0294] The method for forming the negative electrode film in this application includes mixing the above-mentioned raw materials with a solvent (such as deionized water) in a certain mass ratio to form a negative electrode slurry, defoaming the negative electrode slurry, and then uniformly coating the negative electrode slurry onto both sides of the negative electrode current collector; controlling the single-sided coating weight to be 0.13g~0.25g / 1540.25mm. 2 Drying, followed by compaction using a cold press to a specific compaction density (1.65 g / cm³). 3 < Compacted density ≤ 2.0 g / cm³ 3 This yields a negative electrode sheet containing a negative electrode film.

[0295] Electrolyte

[0296] Some embodiments of this application disclose an electrolyte comprising an electrolyte salt and an organic solvent. The electrolyte salt includes any type conventional in the art, such as, but not limited to, inorganic metal salts like RClO4, RAsF6, RPF6, RBF4, RSbF6, RSO3F, RN(FSO2)2, etc.; and fluorine-containing organometallic salts such as RCF3SO3, RN(FSO2)(CF3SO2), RN(CF3SO2)2, RN(C2F5SO2)2, cyclic 1,3-hexafluoropropanedisulfonylimide lithium / sodium, cyclic 1,2-tetrafluoroethanedisulfonylimide lithium / sodium, and RN(CF3SO2)(C4F9SO2). Examples of lithium salts containing dicarboxylic acid complexes include: RC(CF3SO2)3, RPF4(CF3)2, RPF4(C2F5)2, RPF4(CF3SO2)2, RPF4(C2F5SO2)2, RBF2(CF3)2, RBF2(C2F5)2, RBF2(CF3SO2)2, RBF2(C2F5SO2)2, etc.; and metal salts containing dicarboxylic acid complexes, such as lithium / sodium bis(oxalate)borate, lithium / sodium difluorooxalate borate, lithium / sodium tri(oxalate)phosphate, lithium / sodium difluorobis(oxalate)phosphate, lithium / sodium tetrafluoro(oxalate)phosphate, etc. Here, both the metal and R contain one or a combination of lithium ions and sodium ions.

[0297] According to some embodiments of this application, the concentration of the electrolyte salt in the electrolyte is...

[0298] The concentrations of the electrolyte salts disclosed in these embodiments are any one of 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L, 2 mol / L, 2.2 mol / L, 2.5 mol / L, 2.8 mol / L, 3 mol / L, 3.2 mol / L, 3.5 mol / L, 3.8 mol / L, and 4 mol / L, or any one of the above ranges.

[0299] As described above, the organic solvent comprises one or more of carboxylic acid esters and ethers. The carboxylic acid esters comprise one or more of ethyl acetate (EA), methyl acetate (MA), ethyl propionate (EP), propyl acetate (PA), methyl propionate (MP), methyl butyrate (MB), ethyl butyrate (EB), and 1,4-butyrolactone (GBL); the ethers comprise at least one of tetrahydrofuran, dimethyltetrahydrofuran, tetrahydropyran, dimethyltetrahydropyran, 1,2-dimethoxyethane, dipropylene glycol dimethyl ether, or dimethyl phthalate. The organic solvents of this application further include one or two of carbonates, nitrile solvents, and sulfone solvents. The carbonates include one or more of ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl ethyl carbonate (EMC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl carbonate (BC), and fluoroethylene carbonate (FEC). The nitrile solvents include one or more of acetonitrile (AN), glutaronitrile (GLN), and adiponitrile (ADN). The sulfone solvents include at least one or a combination of two of sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0300] According to some embodiments of this application, the electrolyte further comprises a film-forming stabilizer, which includes a positive electrode film-forming stabilizer and a negative electrode film-forming stabilizer. The positive electrode film-forming stabilizer comprises carbonate additives and / or sulfate additives. The carbonate additives include one or more of vinylene carbonate (VC), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), vinyl ethylene carbonate (VEC), and dioctyl carbonate (CC). The sulfate additives include cyclic sulfonate additives and / or sulfated hydrocarbon ester additives; further, the cyclic sulfonate additives include one or more of 1,3-propanesulfonate lactone (PS), propenesulfonate lactone (PES), and 3-fluoro-1,3-propanesulfonate lactone (FPS); the sulfated hydrocarbon ester additives include one or more of vinyl sulfate (DTD), diethyl sulfate (DES), and dimethyl sulfate (DMS). The negative electrode film-forming stabilizer includes one or more of boron lithium salts, phosphorus-containing lithium salts, and sulfur-containing lithium salts; boron-containing lithium salts include one or more of lithium tetrafluoroborate (LiBF4), lithium bis(oxalate)borate (LiBOB), and lithium bis(oxalate)borate (LiDFOB); phosphorus-containing lithium salts include one or more of lithium difluorophosphate (LiPO2F2), lithium fluorophosphate (Li2PO3F), and lithium phosphate (Li3PO4). Sulfur-containing lithium salts include one or more of lithium fluorosulfonate (LiFSO3), lithium sulfate (Li2SO4), and lithium aminosulfonate (LiSO3NH2).

[0301] The secondary battery of this application will be described in detail below with reference to specific embodiments.

[0302] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods.

[0303] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0304] This application may employ conventional inorganic chemistry techniques within the art. In the following examples, efforts have been made to ensure the accuracy of the figures used (including quantities, temperatures, reaction times, etc.), but some experimental errors and biases should be considered. Temperatures (in degrees Celsius) used in the following examples are expressed in °C, and pressures are at or near atmospheric pressure. All reagents were purchased from AR-grade suppliers, and all reactions were carried out under argon protection. Unless otherwise stated, all reagents were obtained commercially.

[0305] Experimental materials:

[0306] 1. Graphite: The artificial graphite was prepared by the above method and the particle size of the artificial graphite met the following requirements: Dv50 is 18.5μm, Dv10 is 3.5μm and Dv90 is 30μm.

[0307] 2. Superabsorbent resin: weight average molecular weight is 100,000 to 550,000.

[0308] 3. Silica gel and its modified compounds: Silicon-based 100 was used as the inorganic silica gel raw material;

[0309] Inorganic silica gel raw materials are reacted with silane coupling agents to undergo amino modification, and then the amino functional groups are amide-bonded with the carboxyl functional groups of nitric acid to form microporous carboxylated silica gel with a surface rich in amino and carboxyl groups.

[0310] 4. Aluminum phosphate molecular sieve; average pore size 0.2nm~2nm; specific surface area BET 100m² 2 / g~300m 2 / g; pore volume is 0.026cm³ 3 / g~0.09cm 3 / g.

[0311] 5. The purity of alkali metal salts or alkaline earth metal salts is analytical grade.

[0312] Among them, particle size testing:

[0313] Referring to standard GB / T19077-2016: Obtain the volumetric particle size distribution curve of the first or second adsorbent. Take the particle size corresponding to a cumulative volumetric distribution percentage of 50% as the average particle size Dv50, the particle size corresponding to a cumulative volumetric distribution percentage of 90% as the average particle size Dv90, and the particle size corresponding to a cumulative volumetric distribution percentage of 10% as the average particle size Dv10. The testing instrument can be a Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.

[0314] Specific surface area test:

[0315] Referring to standard GB / T19587-2017: the obtained first or second adsorbent is tested using the nitrogen adsorption specific surface area analysis method, and the specific surface area is calculated using the BET (Brunauer Emmett Teller) method. The testing instrument can be a TRISTAR II 3020 specific surface area and porosity analyzer from Micromeritics, USA.

[0316] Test of orifice capacity:

[0317] The obtained first or second adsorbent should be tested according to the test method in GB / T21650.2-2008. The testing instrument can be a TRISTAR II 3020 specific surface area and porosity analyzer from Micromeritics, USA.

[0318] Test of average pore size:

[0319] In the above specific surface area test, the pore size distribution curve of each pore is obtained, the specific surface area is obtained, the pore volume is obtained, and based on the relevant pore model of the porous structure, the pore volume is divided by the specific surface area and multiplied by the model coefficient to obtain the average pore size.

[0320] Example 1-1

[0321] A secondary battery is provided, comprising a positive electrode, a separator and a negative electrode stacked in sequence, and an electrolyte.

[0322] Preparation of the separating membrane:

[0323] A starch-acrylate polymer (mainly sodium salt) with a weight-average molecular weight of 300,000 was mixed and dispersed with lithium chloride and polyvinylidene fluoride binder in N-methylpyrrolidone to form a slurry. The mass of the starch-acrylate polymer was m0 (kg), the mass of lithium chloride was 20% × m0, and the mass of polyvinylidene fluoride binder was 5% × m0. The slurry was uniformly coated on both sides of a porous polyethylene substrate (thickness of 9 μm, porosity of 40%, air permeability of 130 seconds / 100 mL) and dried to form a release film.

[0324] Preparation of negative electrode sheet:

[0325] Artificial graphite, conductive carbon black (a conductive agent), sodium carboxymethyl cellulose (a stabilizer), and SBR (a binder) were dispersed in deionized water at a mass ratio of 95:1.0:1.5:2.5 to form a negative electrode slurry. The negative electrode slurry was then uniformly coated onto both sides of the copper foil used as the negative electrode current collector, with a coating width of 75 mm and a coating surface density of 11 mg / cm³. 2 The film was dried using a nine-section drying oven with sequential temperature settings of 100℃ / 100℃ / 95℃ / 85℃ / 85℃ / 80℃ / 80℃ / 80℃ / 60℃, followed by compaction using a cold press to achieve a single-sided coating weight of 0.15g / 1540.25mm for the negative electrode film. 2 The compaction density of the negative electrode film is 1.72 g / cm³. 3 .

[0326] Preparation of electrolyte:

[0327] In an environment with a water content of less than 10 ppm, non-aqueous organic solvents ethylene carbonate and diethyl carbonate are mixed at a volume ratio of 3:7 to obtain a first solvent, and ethyl acetate and propyl acetate are mixed at a volume ratio of 2:1 to obtain a second solvent. The first solvent and the second solvent are mixed at a certain usage amount (volume ratio 1:2) to form a non-aqueous solvent. Lithium hexafluorophosphate is added to the non-aqueous solvent, and then a film-forming stabilizer (lithium fluorosulfonate and lithium difluorophosphate in a molar ratio of 1:1) is added to prepare an electrolyte with a lithium hexafluorophosphate concentration of 1 mol / L. The amount of film-forming stabilizer added is 0.01 wt% (based on the total mass of the electrolyte).

[0328] Preparation of positive electrode sheet:

[0329] Ternary material LiNi0.8Co0.1Mn0.1O2 (NCM811, Ni:Co:Mn = 8:1:1, Dv50 = 1.55μm), conductive carbon black, carbon nanotubes, and PVDF were mixed together in a ratio of 96.5:2:0.5:1. After adding N-methylpyrrolidone solvent and stirring, a positive electrode slurry with a solid content of 60% was formed. This slurry was then coated onto both surfaces of the positive electrode current collector aluminum foil, with a coating width of 70mm and a coating surface density of 19mg / cm³. 2 The material is heated and dried using a multi-section drying oven with temperatures set sequentially at 120℃, 100℃, and 90℃. Then, it is compacted using a cold press to obtain a positive electrode sheet with a compacted density of 2.7 g / cm³. 3 The positive electrode sheet has a single-sided coating weight of 0.34g / 1540.25mm. 2 The compaction density of the positive electrode film is 2.8 g / cm³. 3 .

[0330] Preparation of secondary batteries:

[0331] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. Three copper wires are added for the electrodes, and the tabs are welded together to form a stacked battery cell. The stacked battery cell is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained.

[0332] Examples 1-2 to 1-7 provide a secondary battery:

[0333] Examples 1-2 to 1-7 provide a secondary battery, which differs from Example 1-1 in that the type of the first adsorbent is different, as shown in Table 2.

[0334] Example 2 provides a secondary battery:

[0335] Example 2 provides a secondary battery, which differs from Examples 1-1 in that an insulating layer (approximately 2 μm thick) is provided between the base film and the coating of the separator. The method for preparing this insulating layer is as follows:

[0336] Silica, polyacrylonitrile fiber, and polyvinylidene fluoride binder are mixed in a mass ratio of 1:1:0.02 and dispersed in N-methylpyrrolidone to form a dispersion slurry. The dispersion slurry is coated on both sides of the base film and dried to form an insulating layer. Then, a coating is formed by coating according to the method listed in Examples 1-1. The coating thickness varies depending on the type of the second adsorbent in the coating.

[0337] Examples 3-1 to 3-2 provide a secondary battery:

[0338] Examples 3-1 to 3-2 provide a secondary battery, which differs from Example 1-1 in that the content ratio of the second adsorbent and the binder in the first adsorbent is different, as detailed in Table 2.

[0339] Example 4 provides a secondary battery:

[0340] Example 4 provides a secondary battery that differs from Examples 1-1 in that it uses a different electrolyte. The electrolyte preparation method in Example 4 is as follows:

[0341] In an environment with a water content of less than 10 ppm, non-aqueous organic solvents ethylene carbonate and diethyl carbonate are mixed at a volume ratio of 3:7 to obtain a first solvent. Tetrahydrofuran is used as a second solvent. The first solvent and the second solvent are mixed at a certain usage amount (volume ratio 1:2) to form a non-aqueous solvent. Lithium hexafluorophosphate is added to the non-aqueous solvent, and then a film-forming stabilizer (lithium fluorosulfonate and lithium difluorophosphate in a molar ratio of 1:1) is added to prepare an electrolyte with a lithium hexafluorophosphate concentration of 1 mol / L. The amount of film-forming stabilizer added is 0.01 wt% (based on the total mass of the electrolyte).

[0342] Example 5 provides a secondary battery:

[0343] In the above embodiments, the coating is formed entirely on both sides of the base film, and the coating method is as follows: Figure 6b Illustration. However, this embodiment 5 adopts... Figure 7b The coating method is illustrated, and all other aspects are the same as in Example 1-1.

[0344] Examples 6-1 to 6-2 provide a secondary battery:

[0345] Examples 6-1 and 6-2 provide a secondary battery that differs from Example 1 in that the particle size of the positive electrode active material and the compaction density of the positive electrode film are different. Specifically, the positive electrode active material in Example 6-1 has a Dv50 of 1.3 μm, and the compaction density of the positive electrode film is 2.65 g / cm³. 3 The positive electrode active material Dv50 in Example 6-2 is 1.1 μm, and the compaction density of the positive electrode film is 2.52 g / cm³. 3 .

[0346] Comparative Example 1

[0347] A secondary battery is provided, which differs from Embodiment 1-1 in that the separator does not contain a coating.

[0348] Comparative Example 2

[0349] A secondary battery is provided, which differs from Example 1-1 in that the coating of the separator does not contain a second adsorbent.

[0350] Table 1-1 Raw Material List

[0351]

[0352] Table 1-2 Raw Material List

[0353]

[0354] Table 1-3 Raw Material List

[0355]

[0356] [Performance Testing]

[0357] ① Measurement of gas adsorption capacity of the isolation membrane: Cut the isolation membrane into a square sample with sides of 1cm × 1cm, dry it, weigh it, and give it a mass of m0. Then place it in a BET measuring device, such as the NOVA4200e fully automatic specific surface area analyzer of the American CANTA Instruments Company (nitrogen adsorption, temperature 77K). Determine its nitrogen adsorption capacity according to the BET measurement method, which is L0. The formula for calculating the gas adsorption capacity is: L0 / m0. Repeat the operation 5 times and take the average value.

[0358] ② Measurement of the liquid absorption rate of the separator: The weight difference between the material after saturation with electrolyte (electrolyte in Example 1-1) and the material before adsorption was calculated by gravimetric method, and the liquid absorption rate was calculated according to the following formula:

[0359] η: η=[(W1-W0) / W0]×100%;

[0360] In the formula, η is the liquid absorption rate (%); W0 is the weight of the material before adsorption (g); and W1 is the weight of the material after adsorption.

[0361] ③ Measurement of the porosity of the base membrane of the separating membrane:

[0362] Take a base film sample that has not undergone the coating treatment of this application, cut it into a square sample of approximately 20mm × 20mm, measure the thickness and actual side length using a digital micrometer and vernier calipers, calculate its volume as V, and weigh it as M0. Then immerse the square sample in the electrolyte (the electrolyte of Example 1-1) and soak it for 2 hours at room temperature and in air atmosphere. After soaking, remove it, absorb the electrolyte liquid adsorbed on the surface, and then weigh it as M. t The porosity of the coating then satisfies the following mathematical relationship:

[0363] Porosity = (M) t -M0) / ρ×V×100%;

[0364] In the above mathematical formula, ρ represents the density of the electrolyte, with units of mm. 3 / g, V is the volume of the square sample of the coating, in mm. 3 Weights M0 and M t The unit is g.

[0365] ④ Measurement of the porosity of the membrane coating:

[0366] Take the isolation membrane prepared in this application, scrape off a portion of the coating sample with a doctor blade, and then measure the porosity of the coating according to the method for measuring the porosity of the base membrane described above.

[0367] ⑤ Measurement of the heat shrinkage rate of the release liner at 150°C: The method for measuring the heat shrinkage rate of the release liners manufactured in the examples and comparative examples at 150°C was as follows: the release liner was cut into an equilateral triangle shape with sides of 10 cm to create a sample, and then the area of ​​the sample before the experiment was measured and recorded using a camera. Five sheets of paper were placed above and below the sample to ensure that the sample was centered, and the four sides of the paper were fixed with clips.

[0368] The paper-wrapped sample was placed in a hot air drying oven at 150°C for 1 hour. After the drying period, the sample was removed, the area of ​​the diaphragm was measured with a camera, and the shrinkage rate was calculated using the following formula.

[0369] Shrinkage rate (%) = (Area before heating, area after heating) × 100 / Area before heating

[0370] ⑥ Measurement of puncture strength (pin punch strength): The method for measuring the puncture strength of the separator is according to ASTM D376302 standard; cut 3 test samples from the separator sample, with each test sample having a length and width of not less than 5cm*5cm, fix the test samples on the sample stage, and use a puncture needle with a diameter of 1.65mm and a needle tip (SR) of 0.5mm, and an electronic puncture strength testing machine (such as XJ-830 needle strength tester) to measure it. After the test is completed, take the average of the 3 sets of test results, which is the measured needle punch strength of the separator sample.

[0371] ⑦ Measurement of battery high-temperature storage performance:

[0372] A lithium-ion battery is fully charged at 1C to a voltage of 4.3V, then fully discharged at 0.33C to a cutoff voltage of 2.5V to obtain the initial capacity. It is then fully charged again at 0.33C (100% SOC) to a voltage of 4.3V. After storage at 60℃ for 120 days, it is removed and fully discharged at 0.33C to a cutoff voltage of 2.5V to obtain the capacity after storage. The calculation formula is: Capacity after storage / Initial capacity × 100%. Here, SOC (State of Charge) includes the ratio of the battery's usable capacity to its total capacity, reflecting the amount of remaining battery power.

[0373] ⑧ Battery cycle performance testing:

[0374] The lithium-ion battery was charged and discharged at 1C at 25℃, with a charging cutoff voltage of 4.3V and a discharging cutoff voltage of 2.5V. The capacity retention rate of the lithium-ion battery after 1000 cycles was recorded. The capacity retention rate of the secondary battery after 1000 cycles at 25℃ (%) = discharge capacity of the 1000th cycle / discharge capacity of the 1st cycle × 100%.

[0375] Table 2 List of Separating Membranes

[0376]

[0377]

[0378] Table 3 Battery Performance List

[0379]

[0380]

[0381] As can be seen from the list, this application investigated the effects of different types of first adsorbents and first adsorbents with different physicochemical parameters on battery performance in Examples 1-1 to 1-7. The investigation showed that when the first adsorbent included superabsorbent resin or aluminum phosphate molecular sieve, the adsorption performance, mechanical properties, and heat resistance of the separator were all relatively ideal. Furthermore, the starch-acrylate polymer among the superabsorbent resins exhibited more ideal adsorption properties compared to other types of superabsorbent resins.

[0382] In Example 5, this application provides a partial coating method, which can achieve the same adsorption effect as the full coating in Example 1.

[0383] Therefore, the separator provided in this application can adsorb free water and acids (such as hydrofluoric acid) inside the battery, reducing the damage of these substances to the solid electrolyte interface (SEI film) of the battery, so that the secondary battery can simultaneously achieve cycle stability and storage stability.

[0384] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A secondary battery, characterized in that, It includes a positive electrode, a separator, and a negative electrode stacked together; The isolation membrane includes a base membrane and a coating located on at least one surface of the base membrane; The coating comprises a first adsorbent and a second adsorbent; The first adsorbent comprises any one or more of the following: superabsorbent resin, silica gel and its modified compounds, and aluminum phosphate molecular sieve. The second adsorbent comprises any one or more of alkali metal salts or alkaline earth metal salts; At least a portion of the second adsorbent is located on the surface and inside the first adsorbent.

2. The secondary battery according to claim 1, characterized in that, The mass of the second adsorbent is 10% to 30% of the mass of the first adsorbent.

3. The secondary battery according to claim 1 or 2, characterized in that, The weight-average molecular weight of the superabsorbent resin is 100,000 to 500,000. and / or; The superabsorbent resin includes any one or more of the following: polyacrylate and its modified compounds, starch-acrylate polymer and its derivatives, starch-acrylonitrile polymer and its derivatives, starch-acrylamide polymer and its derivatives, and acrylamide-acrylonitrile-acrylic acid terpolymer and its derivatives.

4. The secondary battery according to any one of claims 1 to 3, characterized in that, The volumetric particle size distribution Dv50 of the silica gel and its modified compounds is 1.0 μm to 2.7 μm; and / or; The average pore size of the silica gel and its modified compounds is 6 nm to 15 nm; and / or; The specific surface area (BET) of the silica gel and its modified compounds is 200 m². 2 / g~700m 2 / g; and / or; The silica gel and its modified compounds have a pore volume of 1.05 cm³. 3 / g~2.0cm 3 / g.

5. The secondary battery according to any one of claims 1 to 4, characterized in that, The average pore size of the aluminum phosphate molecular sieve is 0.2 nm to 2 nm; and / or; The specific surface area (BET) of the aluminum phosphate molecular sieve is 100 m². 2 / g~300m 2 / g; and / or; The pore volume of the aluminum phosphate molecular sieve is 0.026 cm³. 3 / g~0.09cm 3 / g.

6. The secondary battery according to any one of claims 1 to 5, characterized in that, The alkali metal salt comprises any one or more of alkali metal chlorides and fluorides; The alkaline earth metal salt includes any one or more of the chlorides and fluorides of alkaline earth metals.

7. The secondary battery according to any one of claims 1 to 6, characterized in that, The second adsorbent comprises any one or more of lithium chloride, sodium chloride, potassium chloride, lithium fluoride, sodium fluoride, potassium fluoride, calcium fluoride, and calcium chloride.

8. The secondary battery according to any one of claims 1 to 7, characterized in that, The porosity of the coating is greater than that of the base film.

9. The secondary battery according to any one of claims 1 to 8, characterized in that, The porosity of the coating is 70% to 85%; and / or; The porosity of the base membrane is 30% to 45%.

10. The secondary battery according to any one of claims 1 to 9, characterized in that, The coating is formed on the entire surface of the base film.

11. The secondary battery according to any one of claims 1 to 9, characterized in that, The coating is formed on a portion of the surface of the base film; The isolation membrane includes the coated area formed by the coating and the blank area without the coating. The coated area and the blank area are alternately distributed along a first direction or a second direction; The first direction is different from the second direction, and both are perpendicular to the thickness direction of the separator.

12. The secondary battery according to any one of claims 1 to 11, characterized in that, The thickness of the coating is 2% to 50% of the thickness of the base film.

13. The secondary battery according to any one of claims 1 to 12, characterized in that, The coating also includes a binder, the mass of which is 3% to 10% of the mass of the first adsorbent; and / or; The adhesive includes any one or more of lithium metasilicate, organoboronic acid, polyvinyl alcohol, styrene-butadiene rubber, carboxymethyl cellulose, polyacrylic acid, polyacrylonitrile, polyacrylate, and polyvinylidene fluoride.

14. The secondary battery according to any one of claims 1 to 13, characterized in that, An insulating layer is also provided between the coating and the base film.

15. The secondary battery according to any one of claims 1 to 14, characterized in that, The positive electrode sheet includes a positive current collector and a positive electrode film layer located on either side of the surface of the positive current collector. The positive electrode film layer includes a positive electrode active material, and the volumetric particle size distribution of the positive electrode active material is Dv50 < 1.6 μm; preferably 1.0 μm ≤ Dv50 < 1.6 μm. and / or; The compaction density of the positive electrode film layer is >2.5 g / cm³. 3 The preferred value is 2.5 g / cm³. 3 < Compacted density ≤ 3.4 g / cm³ 3 ; and / or; The negative electrode sheet comprises a negative current collector and a negative electrode film layer located on either side of the surface of the negative current collector, wherein the compaction density of the negative electrode film layer is >1.65 g / cm³. 3 The preferred value is 1.65 g / cm³. 3 < Compacted density ≤ 2.0 g / cm³ 3 .

16. The secondary battery according to any one of claims 1 to 15, characterized in that, The battery also includes an electrolyte, which comprises one or more of carboxylic acid esters and ethers.

17. A separating membrane, characterized in that: The coating comprises a base membrane and a coating located on at least one side surface of the base membrane. The coating comprises a first adsorbent and a second adsorbent. The first adsorbent comprises one or more of a superabsorbent resin, silica gel and its modified compounds, and aluminum phosphate molecular sieve. The second adsorbent comprises one or more of an alkali metal salt or an alkaline earth metal salt. At least a portion of the second adsorbent is located on the surface and inside the first adsorbent.

18. The separator membrane according to claim 17, characterized in that: The mass of the second adsorbent is 10% to 30% of the mass of the first adsorbent.

19. A battery pack, characterized in that, It includes the secondary battery according to any one of claims 1 to 16 or the separator according to any one of claims 17 to 18.

20. An electrical device, characterized in that, It includes the secondary battery according to any one of claims 1 to 16, the separator according to any one of claims 17 to 18, or the battery pack according to claim 19.

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