Secondary battery and preparation method therefor, and electrical device

Abstract

Provided are a secondary battery and a preparation method therefor, and an electrical device. The secondary battery comprises a positive electrode sheet, a negative electrode sheet, and a separator disposed between the positive electrode sheet and the negative electrode sheet. The separator comprises a base film and a functional layer disposed on the surface of at least one side of the base film. The functional layer comprises an acid scavenger, and the acid scavenger comprises a phosphate. Hence, hydrofluoric acid-induced electrolyte decomposition and damage to the SEI and CEI films can be reduced, thereby reducing loss of active lithium and improving the storage life of the secondary battery.

Description

Secondary batteries, their preparation methods, and electrical devices

[0001] Related applications

[0002] This application claims priority to Chinese patent application No. 202510360568.2, filed on March 25, 2025, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of battery technology, and in particular to a secondary battery, its preparation method, and an electrical device thereof. Background Technology

[0004] During long-term charge-discharge cycles, bound water in the electrode plates of a secondary battery will gradually be released and enter the electrolyte. The water will react with the electrolyte to produce hydrofluoric acid, which will damage the CEI and SEI films of the lithium battery, resulting in a reduction in the storage life of the secondary battery. Summary of the Invention

[0005] In view of the above problems, this application provides a secondary battery and its preparation method and power device, aiming to improve the storage life of the secondary battery while maintaining its dynamic performance.

[0006] In a first aspect, this application provides a secondary battery, including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode. The separator includes a base film and a functional layer disposed on at least one surface of the base film. The functional layer includes an acid remover, which includes phosphate.

[0007] In the technical solution of this application embodiment, phosphate can remove hydrofluoric acid from the secondary battery, thereby reducing electrolyte decomposition and damage to the SEI and CEI films caused by hydrofluoric acid. Furthermore, improved stability of the CEI film reduces the dissolution of transition metal elements in the positive electrode active material, thus reducing the loss of active lithium. Therefore, the addition of an acid remover can improve the storage life of the secondary battery. Additionally, placing the acid remover in the functional layer of the separator allows for effective contact between the acid remover and hydrofluoric acid, contributing to improved acid removal efficiency. Moreover, compared to adding the acid remover to the electrolyte, it reduces the impact on the electrolyte's kinetic properties, thereby helping to maintain the kinetic performance of the secondary battery.

[0008] In some embodiments, the phosphate includes at least one of sodium pyrophosphate, lithium phosphate, and hydroxyapatite.

[0009] In the technical solution of this application embodiment, sodium pyrophosphate is a weak acid salt, and hydrofluoric acid is a weak acid. When the two react, the acidity of hydrofluoric acid neutralizes the alkalinity of sodium pyrophosphate, while the F in hydrofluoric acid... - Ions may react with Na+ Or pyrophosphate (P2O7) 4- The metal ions in the solution undergo complexation, promoting the reaction. The reaction between lithium phosphate and hydrofluoric acid is based on the interaction between ions. Through metathesis and ion exchange processes, more stable products lithium fluoride and phosphoric acid are generated, thus driving the reaction. Hydroxyapatite is alkaline and can be neutralized by acid-base neutralization. In addition, hydroxyapatite has a porous structure and can also remove acid by adsorbing acidic molecules.

[0010] In some embodiments, the acid remover further includes at least one of polyethyleneimine and polyimide.

[0011] In the technical solution of this application embodiment, the molecular structure of polyethyleneimine contains amine groups, which can remove acid through a neutralization reaction. Polyimide can provide abundant HF coordination sites and form -COOH-F hydrogen bonds, effectively anchoring free HF molecules in the electrolyte.

[0012] In some embodiments, the deacidifying agent accounts for 1%-20% of the mass of the functional layer.

[0013] In the technical solution of this application embodiment, when the mass ratio of the deacidifying agent is 1%-20%, the deacidification effect of the separator is significant.

[0014] In some embodiments, the functional layer further includes inorganic particles, which include at least one of alumina and boehmite.

[0015] In the technical solution of this application embodiment, the functional layer includes inorganic particles, which can improve the thermal stability of the separator and reduce problems such as deformation of the separator due to temperature rise during battery charging and discharging, thus helping to improve the thermal stability of the battery. In addition, inorganic particles can enhance the mechanical strength of the separator and improve its puncture resistance and tear resistance.

[0016] In some embodiments, the inorganic particles account for 50%-95.8% of the mass of the functional layer.

[0017] In the technical solution of this application embodiment, when the mass ratio of inorganic particles in the functional layer is between 50% and 95.8%, an effective network structure can be formed in the separator, which can significantly improve the heat resistance and mechanical properties of the separator and reduce the impact on ion conduction.

[0018] In some embodiments, the particle size D of the inorganic particles V 50 is 0.2μm-0.6μm.

[0019] In the technical solution of this application embodiment, the particle size D of the inorganic particles VWhen the thickness of the membrane is between 0.2μm and 0.6μm, the mechanical strength and ionic conductivity of the membrane can be balanced.

[0020] In some embodiments, the functional layer further includes an adhesive, which includes a polyacrylic adhesive.

[0021] In the technical solution of this application embodiment, the polyacrylic acid adhesive contains polar groups such as carboxyl groups, which can firmly bond with the hydroxyl groups on the surface of inorganic particles through hydrogen bonds, chemical bonds, and other interactions, making the inorganic particles less prone to detachment. Furthermore, the polyacrylic acid adhesive has good chemical stability and can resist the erosion of the electrolyte.

[0022] In some embodiments, the adhesive accounts for 3%-8% of the mass of the functional layer.

[0023] In the technical solution of this application embodiment, when the mass ratio of the adhesive in the functional layer is between 3% and 8%, it can provide the required adhesive force, which helps to distribute the particles evenly, thereby helping to improve the uniformity and consistency of the functional layer.

[0024] In some embodiments, the functional layer further includes a dispersant, the dispersant comprising carboxymethyl cellulose.

[0025] In the technical solution of this application embodiment, carboxymethyl fiber has good dispersibility, which helps to uniformly disperse particles; in addition, the molecular chain of carboxymethyl fiber contains a large number of hydrophilic groups (hydroxyl, carboxyl, etc.), which can form hydrogen bonds or chemical bonds with inorganic particles and groups on the surface of the base film, which can firmly connect particles and base film, and help improve the adhesion between functional layer and base film.

[0026] In some embodiments, the dispersant accounts for 0.2%-0.8% of the mass of the functional layer.

[0027] In the technical solution of this application embodiment, when the mass ratio of dispersant in the functional layer is 0.2%-0.8%, carboxymethyl fiber can prevent the agglomeration between particles through steric hindrance and electrostatic repulsion, so that the particles are uniformly dispersed and the situation of excessively high or low local concentration is reduced.

[0028] In some embodiments, the thickness of the functional layer is 0.5 μm-3.0 μm.

[0029] In the technical solution of this application embodiment, when the thickness of the functional layer is between 0.5μm and 3.0μm, it can effectively remove acid and reduce the impact on battery energy density.

[0030] In some embodiments, the air permeability of the isolation membrane is 200 secs / 100cc to 300 secs / 100cc.

[0031] Secondly, this application provides a method for preparing a secondary battery, comprising:

[0032] A separator is provided, the separator comprising a base film and a functional layer disposed on at least one side surface of the base film, the functional layer comprising an acid remover, the acid remover comprising phosphate; a positive electrode, a negative electrode, and an electrolyte are provided; the positive electrode, the negative electrode, and the separator are assembled into an electrode assembly; the electrode assembly is placed in an outer packaging, injected with the electrolyte, and then sealed to obtain a secondary battery.

[0033] In some embodiments, the step of providing the insulating membrane includes:

[0034] An acid remover, inorganic particles, a binder, a dispersant, and a base film are provided; the acid remover, inorganic particles, binder, and dispersant are added to a solvent and stirred evenly to obtain a functional slurry; the functional slurry is coated on at least one side surface of the base film and dried to obtain a release film.

[0035] In some embodiments, the step of adding the deacidifying agent, inorganic particles, binder, and dispersant to a solvent and stirring until homogeneous to obtain a functional slurry includes:

[0036] First, add the dispersant to the solvent and stir for 10-30 minutes. Then, add the deacidifying agent and stir for 20-60 minutes. Next, add the inorganic particles and stir for 20-60 minutes. Finally, add the binder and stir for 30-60 minutes to obtain the functional slurry.

[0037] In the technical solution of this application embodiment, the dispersant, deacidifying agent, inorganic particles and binder are added sequentially and stepwise, which helps to promote particle dispersion, enhance the bonding effect and improve the stability of the slurry.

[0038] Thirdly, this application provides an electrical device, including any of the above-mentioned secondary batteries or secondary batteries prepared by any of the above-mentioned methods.

[0039] 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, specific embodiments of this application are given below. Attached Figure Description

[0040] Figure 1 is a schematic diagram of the vehicle structure in some embodiments of this application;

[0041] Figure 2 is a schematic diagram of the exploded structure of a sodium metal secondary battery in some embodiments of this application;

[0042] Figure 3 is a schematic diagram of the exploded structure of a single battery cell in some embodiments of this application;

[0043] Figure 4 is a cross-sectional schematic diagram of the isolation membrane in some embodiments of this application.

[0044] Explanation of reference numerals in the attached drawings: Vehicle 1000; Secondary battery 100, Controller 200, Motor 300; Housing 10, First part 11, Second part 12; Battery cell 20, End cap 21, Housing 22, Electrode assembly 23, Separator 231, Base film 2311, Functional layer 2312. Detailed Implementation

[0045] The following embodiments are only used to illustrate the technical solutions of this application more clearly, and are therefore only examples and should not be used to limit the scope of protection of this application.

[0046] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0047] In the description of the embodiments of this application, technical terms such as "first" and "second" 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. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0048] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0049] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0050] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces). The term "at least one" refers to one or more.

[0051] Water readily reacts with fluorinated electrolyte salts in the electrolyte to produce HF. HF not only induces the decomposition of organic solvents in the electrolyte but also damages the protective films (CEI and SEI) on the surfaces of the positive and negative electrode active materials. In particular, when HF damages the protective film on the surface of the positive electrode active material, transition metal ions in the crystal structure of the positive electrode active material dissolve out, resulting in the loss of active lithium and thus reducing the storage life of the secondary battery.

[0052] In some embodiments, a weakly alkaline additive is added to the electrolyte to neutralize the generated HF, or an electrolyte stabilizer is added to improve the stability of the electrolyte salt, thereby reducing the decomposition of the electrolyte salt and lowering the HF level. However, when the amount of additive added is small, the acid removal effect is not significant, while when the amount added is large, it can easily change the kinetic properties of the electrolyte and affect the kinetic performance of the secondary battery.

[0053] Since the separator is an inert component in the battery and has ample room for maneuver, it can be considered as a carrier to load the deacidification material. This can reduce the impact on the battery's dynamic performance while achieving the deacidification effect.

[0054] Based on the above considerations, this application discloses a secondary battery, the separator of which includes a base film and a functional layer disposed on at least one side of the base film. The functional layer includes an acid remover, which includes phosphate.

[0055] In such secondary batteries, phosphate-based acid removers can remove hydrofluoric acid, thereby reducing electrolyte decomposition and damage to the SEI and CEI films caused by hydrofluoric acid. Furthermore, improved CEI film stability reduces the dissolution of transition metals from the positive electrode active material, decreasing active lithium loss. Therefore, the inclusion of an acid remover can improve the storage life of the secondary battery. Additionally, placing the acid remover in the functional layer of the separator, compared to adding it to the electrolyte, reduces its impact on electrolyte kinetics, thus helping to maintain the kinetic performance of the secondary battery.

[0056] The secondary batteries disclosed in this application can be used, but are not limited to, in electrical devices such as vehicles, ships, or aircraft. A power system for such an electrical device can also be composed of the secondary batteries disclosed in this application.

[0057] This application provides an electrical device that uses a secondary battery as a power source. The secondary battery can be, but is not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0058] For ease of explanation, the following embodiments will be described using a vehicle 1000 as an example of an electrical device according to an embodiment of this application.

[0059] Referring to Figure 1, vehicle 1000 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 secondary battery 100 is installed inside vehicle 1000, which can be located at the bottom, front, or rear of vehicle 1000. The secondary battery 100 can be used to power vehicle 1000; for example, it can serve as the operating power source for vehicle 1000. Vehicle 1000 may also include a controller 200 and a motor 300. The controller 200 controls the secondary battery 100 to supply power to the motor 300, for example, to meet the power needs of vehicle 1000 during startup, navigation, and driving.

[0060] In some embodiments of this application, the secondary battery 100 can not only serve as the operating power source for the vehicle 1000, but also as the driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0061] In some embodiments of this application, the secondary battery 100 can be a single battery cell, a group of battery cells, or a battery pack. Referring to FIG2, taking the secondary battery 100 as a battery pack as an example, the secondary battery 100 can include a housing 10 and a single battery cell 20, with the single battery cell 20 housed within the housing 10. The housing 10 provides a space for the single battery cell 20 and can adopt various structures. In some embodiments, the housing 10 can include a first portion 11 and a second portion 12, which overlap each other, jointly defining a space for accommodating the single battery cell 20. The second portion 12 can be a hollow structure with one open end, and the first portion 11 can be a plate-like structure, covering the open side of the second portion 12 so that the first portion 11 and the second portion 12 jointly define the space. Alternatively, the first portion 11 and the second portion 12 can both be hollow structures with one open side, with the open side of the first portion 11 covering the open side of the second portion 12. Of course, the box 10 formed by the first part 11 and the second part 12 can be of various shapes, such as a cylinder, a cuboid, etc.

[0062] In the secondary battery 100, there can be multiple battery cells 20, which can be connected in series, parallel, or in a mixed manner. A mixed connection means that multiple battery cells 20 are connected in both series and parallel configurations. Multiple battery cells 20 can be directly connected in series, parallel, or in a mixed manner, and then the entire assembly of the multiple battery cells 20 is housed within the casing 10. Alternatively, the secondary battery 100 can also consist of multiple battery cells 20 first connected in series, parallel, or in a mixed manner to form a battery module, and then these battery modules are connected in series, parallel, or in a mixed manner to form a whole, which is also housed within the casing 10. The secondary battery 100 may also include other structures; for example, it may include a busbar component for electrical connection between the multiple battery cells 20.

[0063] Among them, the battery cell 20 can be in the form of a cylinder, a flat shape, a cuboid, or other shapes.

[0064] Referring to Figure 3, the battery cell 20 refers to the smallest unit that makes up the battery. The battery cell 20 includes an end cap 21, a housing 22, an electrode assembly 23, and other functional components.

[0065] End cap 21 refers to a component that covers the opening of housing 22 to isolate the internal environment of battery cell 20 from the external environment. The shape of end cap 21 can be adapted to the shape of housing 22 to fit it. Optionally, end cap 21 can be made of a material with certain hardness and strength (such as aluminum alloy), so that end cap 21 is not easily deformed under pressure or impact, allowing battery cell 20 to have higher structural strength. Functional components such as electrode terminals can be provided on end cap 21. Electrode terminals can be used for electrical connection with electrode assembly 23 for outputting or inputting electrical energy into battery cell 20. In some embodiments, end cap 21 can also be provided with a pressure relief mechanism for releasing internal pressure when the internal pressure or temperature of battery cell 20 reaches a threshold. The material of end cap 21 can also be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and this application embodiment does not impose any special limitations on this. In some embodiments, an insulating element may be provided on the inner side of the end cap 21. The insulating element can be used to isolate the electrical connecting pieces inside the housing 22 from the end cap 21 to reduce the risk of short circuit. For example, the insulating element may be made of plastic, rubber, etc.

[0066] The housing 22 is a component used to cooperate with the end cap 21 to form the internal environment of the battery cell 20. This internal environment can accommodate the electrode assembly 23, electrolyte, and other components. The housing 22 and the end cap 21 can be independent components. An opening can be provided on the housing 22, and the end cap 21 can be used to close the opening to form the internal environment of the battery cell 20. Alternatively, the end cap 21 and the housing 22 can be integrated. Specifically, the end cap 21 and the housing 22 can form a common connecting surface before other components are inserted into the housing. When it is necessary to encapsulate the interior of the housing 22, the end cap 21 closes the housing 22. The housing 22 can be of various shapes and sizes, such as cuboid, cylindrical, hexagonal prism, etc. Specifically, the shape of the housing 22 can be determined according to the specific shape and size of the electrode assembly 23. The material of the housing 22 can be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc. This application embodiment does not impose any special limitations on this.

[0067] Electrode assembly 23 is the component in the battery cell 20 where electrochemical reactions occur. The casing 22 may contain one or more electrode assemblies 23. The electrode assembly 23 is mainly formed by winding or stacking positive and negative electrode sheets, and typically a separator is provided between the positive and negative electrode sheets. The portions of the positive and negative electrode sheets containing active material constitute the main body of the electrode assembly, while the portions without active material each constitute a tab. The positive and negative tabs may be located together at one end of the main body or separately at both ends. During the charging and discharging process of the battery, the positive and negative active materials react with the electrolyte, and the tabs connect to the electrode terminals to form a current loop.

[0068] Of course, in some other embodiments, the secondary battery 100 may also be integrated with the chassis / body.

[0069] According to some embodiments of this application, this application provides a secondary battery, including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode. Referring to FIG4, the separator 231 includes a base film 2311 and a functional layer 2312 disposed on at least one side surface of the base film 2311. The functional layer 2312 includes an acid remover, which includes phosphate.

[0070] The base membrane 2311 can be any known porous membrane with good chemical and mechanical stability. In some embodiments, the material of the base membrane 2311 can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The base membrane 2311 can be a single-layer film or a multilayer composite film. When the base membrane 2311 is a multilayer composite film, the materials of each layer can be the same or different. In some embodiments, the porosity of the base membrane is 20%-40%.

[0071] The functional layer 2312 refers to a functional coating disposed on at least one side of the surface of the base film 2311. Disposing the functional layer 2312, which includes the acid remover, on at least one side of the base film 2311 means that the functional layer 2312 serves as the surface layer of the separator 231. This allows the acid remover to effectively contact hydrofluoric acid, improving the acid removal effect and saving space within the battery. Furthermore, by disposing the acid remover in the functional layer 2312 of the separator 231, compared to adding the acid remover to the electrolyte, the impact on the electrolyte's kinetic properties is reduced, thereby helping to maintain the kinetic performance of the secondary battery.

[0072] Phosphates are compounds containing phosphate ions, generally formed by the chemical reaction of phosphoric acid with metal ions, ammonium ions, etc. In some embodiments, phosphates include at least one of orthophosphates, hydrogen phosphates, dihydrogen phosphates, and polyphosphates. Orthophosphates are compounds composed of phosphate ions and metal ions or ammonium ions; for example, orthophosphates include potassium phosphate, calcium phosphate, and lithium phosphate. Hydrogen phosphates are compounds formed when two hydrogen atoms in the phosphate group are replaced by metal ions or other cations; for example, hydrogen phosphates include disodium hydrogen phosphate and diammonium hydrogen phosphate. Dihydrogen phosphates are compounds formed when one hydrogen atom in phosphoric acid is replaced by a metal ion or other cation; for example, dihydrogen phosphates include potassium dihydrogen phosphate and calcium dihydrogen phosphate. Polyphosphates are compounds composed of multiple phosphate ions linked by oxygen atoms; for example, polyphosphates include sodium pyrophosphate and sodium tripolyphosphate. Phosphates can remove hydrofluoric acid from secondary batteries, thereby reducing electrolyte decomposition and damage to the SEI and CEI films caused by hydrofluoric acid. In addition, the improved stability of the CEI film can reduce the dissolution of transition metal elements in the positive electrode active material and reduce the loss of active lithium. Therefore, the addition of acid removers can improve the storage life of secondary batteries.

[0073] In some embodiments, phosphate can be detected by: disassembling the battery, removing the separator, dissolving the separator coating in water, and performing nuclear magnetic resonance (NMR) on the solution. 31 P NMR) test, in which pyrophosphate (P2O7) 4- The chemical shift is ~-6 ppm, and other phosphates (such as PO4) 3- The chemical shift of ) is ~0 ppm.

[0074] According to some embodiments of this application, the phosphate includes at least one of sodium pyrophosphate, lithium phosphate, and hydroxyapatite.

[0075] Sodium pyrophosphate (Na₄P₂O₇) is a weak acid salt, and hydrofluoric acid (HF) is a weak acid. When they react, the acidity of the hydrofluoric acid neutralizes the basicity of the sodium pyrophosphate. Specifically, sodium pyrophosphate dissociates in water to form Na₂O₇. + and P2O7 4- HF dissociates into H + and F - H + With P2O7 4- The reaction produces pyrophosphoric acid (H4P2O7). Additionally, the F in hydrofluoric acid... - The ion has a strong coordination ability and may interact with Na. + Or pyrophosphate (P2O7) 4- The metal ions in the mixture undergo complexation, promoting the reaction.

[0076] The reaction of lithium phosphate (Li3PO4) with hydrofluoric acid is based on interionic interactions. Through metathesis and ion exchange processes, more stable products, lithium fluoride and phosphoric acid, are generated, thus driving the reaction. Specifically, the lithium ions in lithium phosphate (Li3PO4)... + ) and fluoride ions (F) in hydrofluoric acid - The hydrogen ions (H+) in hydrofluoric acid combine to form lithium fluoride (LiF), which is produced by the combination of these two compounds. + ) and phosphate ions (PO4) in lithium phosphate 3- They combine to form phosphoric acid (H3PO4).

[0077] Hydroxyapatite (Ca 10 (PO4)6(OH)2) is alkaline, and its Ca 2+ and OH - It can neutralize H in acidic environments. + Hydroxyapatite can adsorb acidic anions, thereby achieving an acid removal effect. It also has a porous structure, allowing it to remove acid by adsorbing acidic molecules. Furthermore, hydroxyapatite is an inorganic material with high thermal stability, maintaining structural stability at high temperatures. It also effectively minimizes the risk of shrinkage or melting of the separator 231 at high temperatures, contributing to improved thermal stability. The excellent hardness and mechanical properties of hydroxyapatite significantly improve the puncture resistance and tensile strength of the separator 231.

[0078] According to some embodiments of this application, the acid remover also includes at least one of polyethyleneimine and polyimide.

[0079] Polyethyleneimine (PEI) molecules contain a large number of amine groups (-NH2), which can neutralize H+ in acidic environments through protonation. + Ions. Furthermore, as a cationic polymer, polyvinyl ether can adsorb free acid or byproducts from acidic electrolytes through electrostatic interactions.

[0080] Polyimide can provide abundant HF coordination sites and form -COOH-F hydrogen bonds, which effectively anchor free HF molecules in the electrolyte.

[0081] According to some embodiments of this application, the deacidifying agent accounts for 1%-20% of the mass of the functional layer.

[0082] The mass percentage of the deacidifying agent in the functional layer 2312 refers to the mass percentage of the deacidifying agent in the total solid matter mass of the functional layer after drying. For example, the mass percentage of the deacidifying agent in the functional layer can be 1%, 3%, 5%, 7%, 10%, 12%, 14%, 16%, 18%, or 20%. When the mass percentage of the deacidifying agent is between 1% and 20%, the deacidification effect of the separator is significant.

[0083] According to some embodiments of this application, the functional layer 2312 further includes inorganic particles, which include at least one of alumina and boehmite.

[0084] The inclusion of inorganic particles in the functional layer 2312 means that the solid material of the functional layer 2312 includes inorganic particles. Inorganic particles are tiny particulate materials composed of inorganic compounds with a certain particle size and shape, and typically possess good chemical stability and excellent mechanical properties. The inclusion of inorganic particles in the functional layer 2312 can improve the thermal stability of the separator 231, reducing problems such as deformation of the separator 231 due to temperature increases during battery charging and discharging, thus contributing to improved battery thermal stability. Furthermore, inorganic particles can enhance the mechanical strength of the separator 231, improving its puncture resistance and tear resistance.

[0085] Alumina (Al₂O₃) possesses excellent high-temperature resistance, allowing the separator to maintain its integrity at high temperatures. It also exhibits superior mechanical strength, enhancing the puncture resistance of the separator and enabling it to withstand internal battery stress and external impacts. In addition to improving the thermal stability and mechanical properties of the separator, alumina can neutralize free hydrofluoric acid in the electrolyte, further reducing its damage to the SEI and CEI films.

[0086] Boehmite, with the chemical formula AlO(OH), exhibits excellent thermal stability. When the functional layer 2312 includes boehmite, it effectively improves the high-temperature resistance of the separator 231, reducing the risk of shrinkage, melting, or cracking at high temperatures. Boehmite also possesses a certain degree of mechanical strength, contributing to improved mechanical properties of the separator. Furthermore, boehmite has a low density, allowing for the coating of a larger area than alumina with the same mass, and its bonding with the base film is more robust.

[0087] According to some embodiments of this application, the inorganic particles account for 50%-95.8% of the mass of the functional layer 2312.

[0088] The mass percentage of inorganic particles in functional layer 2312 refers to the mass percentage of inorganic particles in the solid material of functional layer 2312. For example, the mass percentage of inorganic particles in functional layer 2312 can be 50%, 55%, 60%, 62%, 65%, 68%, 70%, 72%, 75%, 77%, 80%, 85%, 90%, or 95.8%. When the mass percentage of inorganic particles in functional layer 2312 is between 50% and 95.8%, an effective network structure can be formed in the separator 231, which can significantly improve the heat resistance and mechanical properties of separator 231 and reduce the impact on ion conduction.

[0089] According to some embodiments of this application, the particle size D of the inorganic particles is...V 50 is 0.2μm-0.6μm.

[0090] For example, the particle size D of the inorganic particles V 50 can be 0.2μm, 0.3μm, 0.4μm, 0.5μm, or 0.6μm, the particle size D of the inorganic particles. V When the particle size is between 0.2μm and 0.6μm, it is close to the pore size of the base film (0.1μm-1μm), which can form a uniform microporous structure and can balance the mechanical strength and ionic conductivity of the separator 231.

[0091] According to some embodiments of this application, functional layer 2312 further includes an adhesive, including polyacrylic adhesives.

[0092] Polyacrylic acid adhesives refer to a class of adhesives whose main component is polyacrylic acid or its derivatives. They can be obtained by homopolymerization of one of the acrylic acid or its derivatives, or by copolymerization of acrylic acid and its derivatives. The derivatives include acrylates, acrylamide, acrylonitrile, etc. In some embodiments, acrylates include at least one of methyl acrylate, ethyl acrylate, butyl acrylate, isooctyl acrylate, methyl methacrylate, ethyl methacrylate, and butyl methacrylate.

[0093] Polyacrylic acid adhesives contain polar groups such as carboxyl groups, which can firmly bond with hydroxyl groups and other groups on the surface of inorganic particles through hydrogen bonds and chemical bonds, making the inorganic particles less prone to detachment. Furthermore, polyacrylic acid adhesives have good chemical stability and can resist the corrosion of electrolytes.

[0094] According to some embodiments of this application, the adhesive accounts for 3%-8% of the mass of the functional layer 2312.

[0095] The mass percentage of the adhesive in the functional layer 2312 refers to the mass percentage of the adhesive in the solid material of the functional layer 2312. For example, the mass percentage of the adhesive in the functional layer 2312 can be 3%, 4%, 5%, 6%, 7%, or 8%. When the mass percentage of the adhesive in the functional layer is between 3% and 8%, it can provide the required adhesive force, which helps to distribute the particles evenly, thereby helping to improve the uniformity and consistency of the functional layer 2312.

[0096] According to some embodiments of this application, functional layer 2312 further includes a dispersant, which includes carboxymethyl cellulose.

[0097] Carboxymethyl cellulose has good dispersibility, which helps to uniformly disperse particles. In addition, the molecular chain of carboxymethyl cellulose contains a large number of hydrophilic groups (hydroxyl, carboxyl, etc.), which can form hydrogen bonds or chemical bonds with inorganic particles and groups on the surface of base film 2311, which can firmly connect particles to base film 2311 and help improve the adhesion between functional layer 2312 and base film 2311.

[0098] According to some embodiments of this application, the dispersant accounts for 0.2%-0.8% of the mass of the functional layer 2312.

[0099] The mass percentage of the dispersant in the functional layer 2312 refers to the mass percentage of the dispersant in the solid material of the functional layer 2312. For example, the mass percentage of the dispersant in the functional layer 2312 can be 0.2%, 0.25%, 0.33%, 0.35%, 0.4%, 0.5%, 0.6%, 0.7%, or 0.8%. When the mass percentage of the dispersant in the functional layer 2312 is between 0.2% and 0.8%, the carboxymethyl fiber can effectively prevent the agglomeration of particles through steric hindrance and electrostatic repulsion, so that the particles are uniformly dispersed and the occurrence of local concentrations that are too high or too low is reduced.

[0100] According to some embodiments of this application, the thickness of the functional layer 2312 is 0.5μm-3.0μm.

[0101] For example, the thickness of the functional layer 2312 can be 0.5μm, 0.8μm, 1.0μm, 1.2μm, 1.5μm, 2.0μm, 2.5μm or 3.0μm. When the thickness of the functional layer is between 0.5μm and 3.0μm, it can effectively remove acid and reduce the impact on the battery energy density.

[0102] According to some embodiments of this application, the air permeability of the separator 231 is 200 secs / 100cc-300 secs / 100cc.

[0103] The permeability of a separator membrane refers to the ability or speed at which gas passes through the membrane under certain conditions. In some embodiments, the permeability of the separator membrane can be expressed as the time required for gas to pass through a 100 cubic centimeter sample of the separator membrane under certain test conditions. For example, the permeability of separator membrane 231 can be 200 secs / 100cc, 210 secs / 100cc, 22 secs / 100cc, 230 secs / 100cc, 240 secs / 100cc, 250 secs / 100cc, 260 secs / 100cc, 270 secs / 100cc, 280 secs / 100cc, 290 secs / 100cc, or 300 secs / 100cc.

[0104] According to some embodiments of this application, this application also provides a method for preparing a secondary battery, comprising: providing a separator, the separator comprising a base film and a functional layer disposed on at least one side surface of the base film, the functional layer comprising an acid remover, the acid remover comprising phosphate; providing a positive electrode, a negative electrode and an electrolyte; assembling the positive electrode, the negative electrode and the separator into an electrode assembly; placing the electrode assembly into an outer packaging, injecting electrolyte and then encapsulating it to obtain a secondary battery.

[0105] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector. In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0106] The positive electrode film layer includes a positive electrode active material. When the secondary battery is a lithium-ion battery, the positive electrode active material can be a positive electrode active material known in the art for lithium-ion batteries. Exemplarily, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM)622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0107] In some embodiments, the positive electrode film layer may optionally include a binder. Exemplarily, the binder includes at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0108] In some embodiments, the positive electrode film may optionally include a conductive agent. Exemplarily, the conductive agent includes at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0109] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0110] The negative electrode includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector. In some embodiments, the negative current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0111] The negative electrode film layer includes a negative electrode active material, which may be a negative electrode active material known in the art for use in batteries. Exemplarily, the negative electrode active material includes at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys.

[0112] In some embodiments, the negative electrode film layer may optionally include an adhesive. The adhesive may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0113] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0114] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0115] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0116] The electrolyte comprises an electrolyte salt and a solvent. In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0117] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0118] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0119] The electrode assembly can be formed by winding positive electrode, negative electrode and separator, or by stacking.

[0120] The outer packaging is used to encapsulate the electrode components and electrolyte. The outer packaging can be a hard shell, such as a hard plastic shell, aluminum shell, or steel shell. The outer packaging of a secondary battery can also be a soft pack, such as a pouch. The soft pack can be made of plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0121] According to some embodiments of this application, the step of providing a separator membrane includes: providing an acid remover, inorganic particles, a binder, a dispersant, and a base membrane; adding the acid remover, inorganic particles, binder, and dispersant to a solvent and stirring until homogeneous to obtain a functional slurry; coating the functional slurry onto at least one surface of the base membrane and drying to obtain a separator membrane. In some embodiments, the solvent may be water.

[0122] According to some embodiments of this application, the step of adding an acid remover, inorganic particles, binder, and dispersant to a solvent and stirring evenly to obtain a functional slurry includes: first adding the dispersant to the solvent and stirring for 10 min-30 min, then adding the acid remover and stirring for 20 min-60 min, then adding the inorganic particles and stirring for 20 min-60 min, and finally adding the binder and stirring for 30 min-60 min to obtain the functional slurry.

[0123] During the above stirring process, the stirring speed is not specifically limited. In some embodiments, the stirring speed can be 500 rpm, 800 rpm, 1000 rpm, 1200 rpm, or 1500 rpm. This application adds the dispersant, deacidifying agent, inorganic particles, and binder sequentially in steps, which helps to promote particle dispersion, enhance the bonding effect, and improve the stability of the slurry.

[0124] According to some embodiments of this application, this application also provides an electrical device, including any of the above-described secondary batteries or secondary batteries prepared by any of the above-described methods.

[0125] Example

[0126] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0127] Example 1

[0128] [Positive electrode plate]

[0129] Boehmite and polyacrylate were mixed in N-methylpyrrolidone at a ratio of 7.8:1 to obtain a ceramic slurry with a solid content of 10% and a viscosity of 800 mPa·s.

[0130] Lithium iron phosphate, conductive carbon black, and polyvinylidene fluoride were mixed in N-methylpyrrolidone (NMP) at a mass ratio of 8:1:1 to obtain a positive electrode slurry. The positive electrode slurry was then evenly coated on both sides of an aluminum foil, and the positive electrode sheet was obtained after cold pressing and cutting.

[0131] The positive electrode sheet is rolled into a film roll, and a ceramic slurry is coated on the cut surface of the film roll. The coating thickness of the ceramic slurry is 2μm.

[0132] [Negative electrode plate]

[0133] Artificial graphite, conductive carbon black, and carboxymethyl cellulose were mixed in water at a ratio of 95:2:3 and rolled evenly to obtain a negative electrode slurry with a solid content of 50%. The negative electrode slurry was evenly coated on both sides of a copper foil, and after cold pressing and cutting, a negative electrode sheet was obtained.

[0134] [Isolation membrane]

[0135] A polyethylene film with a thickness of 7 μm was used as the base film, and the porosity of the base film was 33%.

[0136] Carboxymethyl cellulose was added to water and stirred at 500 rpm for 20 minutes. Sodium pyrophosphate was then added and stirring continued at 1000 rpm for 40 minutes. Finally, alumina (particle size D) was added. V The mixture (50 μm) was stirred at 1000 rpm for 30 min, and then polyacrylate binder was added and stirred at 1000 rpm for another 40 min to obtain the functional layer slurry. The functional layer slurry had a solid content of 35% and a viscosity of 150 mPa·s. The mass ratio of sodium pyrophosphate, alumina, polyacrylate, and carboxymethyl cellulose was 3.5:29.575:1.75:0.175.

[0137] The functional layer slurry was uniformly coated on both sides of the base film, with a single-sided coating thickness of 2 μm. After drying, a release membrane was obtained. The dried functional layer contained 10% sodium pyrophosphate, 84.5% alumina, 5% polyacrylate, and 0.5% carboxymethyl cellulose by mass.

[0138] Electrolyte

[0139] Ethylene carbonate, diethyl carbonate, and dimethyl carbonate were mixed in a volume ratio of 1:1:1. LiPF6 was then dissolved in the mixture to obtain an electrolyte with a concentration of 1 mol / L of LiPF6.

[0140] [Assemble]

[0141] The electrodes are arranged in the order of "separator - negative electrode - separator - positive electrode". One end of the positive electrode, negative electrode, and two separators is fixed to the discharge roller, and the other end is stacked together and fixed to the winding shaft. A motor is used to rotate the winding shaft to wind the positive electrode, negative electrode, and two separators, thus obtaining a wound electrode assembly. The electrode assembly is then placed in an outer packaging for sealing, electrolyte is injected, and formation and degassing processes are performed to obtain a secondary battery.

[0142] Example 2

[0143] Unlike Example 1, in this example, the mass ratio of sodium pyrophosphate, alumina, polyacrylate, and carboxymethyl cellulose is 5.25:27.825:1.75:0.175, that is, sodium pyrophosphate accounts for 15% of the mass of the functional layer after drying, and alumina accounts for 79.5% of the mass of the functional layer after drying.

[0144] Example 3

[0145] Unlike Example 1, in this example, the mass ratio of sodium pyrophosphate, alumina, polyacrylate, and carboxymethyl cellulose is 7:26.075:1.75:0.175, that is, the mass percentage of sodium pyrophosphate in the solid matter is 20%, and the mass percentage of alumina in the solid matter is 74.5%.

[0146] Example 4

[0147] Unlike Example 1, in this example, the mass ratio of sodium pyrophosphate, alumina, polyacrylate, and carboxymethyl cellulose is 0.35:32.725:1.75:0.175, that is, the mass percentage of sodium pyrophosphate in the dried functional layer is 1%, and the mass percentage of alumina in the dried functional layer is 93.5%.

[0148] Example 5

[0149] Unlike Example 1, the coating thickness of the functional layer slurry in this example is 3 μm.

[0150] Example 6

[0151] Unlike Example 1, the coating thickness of the functional layer slurry in this example is 0.5 μm.

[0152] Example 7

[0153] Unlike Example 1, the deacidifying agent in this example is lithium phosphate.

[0154] Example 8

[0155] Unlike Example 1, the deacidifying agent in this example also includes polyethyleneimine, and the mass ratio of sodium pyrophosphate and poly(II)imine is 8:2.

[0156] Comparative Example 1

[0157] Unlike Example 1, this comparative example does not include the deacidifying agent sodium pyrophosphate, and the mass percentage of alumina in the functional layer is 94.5%.

[0158] Comparative Example 2

[0159] Unlike Example 1, the isolation membrane in this comparative example consists of two base films and a functional layer disposed between the two base films. The composition of the functional layer is the same as that in Example 1.

[0160] Performance testing

[0161] Air permeability of the separator: The separator was cut into 10cm×5cm pieces and the air permeability of the separator was tested using a Japanese KRK Kumagai Oken digital air permeability tester 0518-P.

[0162] Acid removal test of the separator: The separator was cut into 100mm×100mm shapes and then placed in an oven at 105℃ for 12 hours. After the heating was completed, the separator was removed and placed in 10g of electrolyte (1mol / L LiPF6 electrolyte, solvent system EC:DEC:DMC=1:1:1 (volume ratio)). After storage at 60℃ for 2 days, the supernatant of the electrolyte was taken and sent to test the hydrofluoric acid content.

[0163] Storage performance test: 1. Conduct initial charge and discharge energy experiment of battery; 2. Initial charge of single cell at rated power; 3. Adjust the test sample to 50% SOC; 4. Place the battery cell at 60℃ for 30 days; 5. Place at 25℃ for 5 hours; 6. At 25℃, discharge the battery at a constant power of 1Prd to the battery's discharge cutoff voltage, and let it stand for 10 minutes; 7. At 25℃, charge the battery at a constant power of 1Prc to the battery cell's charging cutoff voltage, and let it stand for 10 minutes; 8. At 25℃, charge the battery at a constant power of 1Prc to the battery's charging cutoff voltage, and let it stand for 10 minutes; 9. Calculate the charging energy recovery rate of the test sample using the initial charging energy in step 1 and the charging energy in step 7; 10. Calculate the discharge energy recovery rate of the test sample using the initial discharge energy in step 1 and the discharge energy in step 8. The capacity retention rate is the value obtained in step 10.

[0164] Test Results

[0165] The test results of Examples 1-8 and Comparative Examples 1-2 are shown in Table 1.

[0166] Table 1. Test results from Examples 1-8 and Comparative Examples 1-2

[0167] As shown in Table 1, the hydrofluoric acid content in the electrolyte of the batteries in this application embodiment ranged from a minimum of 57 ppm to a maximum of 480 ppm after storage at 60°C for 2 days. This is lower than the 530 ppm content in Comparative Example 1 without the addition of an acid remover, indicating that the addition of a phosphate acid remover to the separator in this application can effectively remove acid. Furthermore, the capacity retention rate of the batteries in this application embodiment is higher than that of Comparative Example 1, indicating that removing hydrofluoric acid from the batteries helps improve their cycle performance.

[0168] Comparing Example 1 and Comparative Example 2, it can be seen that the present application provides functional layers containing deacidifying agents on both sides of the base film, which can improve the deacidification effect compared to providing a functional layer containing deacidifying agents between two base films.

[0169] 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, comprising a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, wherein, The isolation membrane includes a base membrane and a functional layer disposed on at least one side of the base membrane. The functional layer includes an acid remover, which includes phosphate.

2. The secondary battery as described in claim 1, wherein, The phosphate includes at least one of sodium pyrophosphate, lithium phosphate, and hydroxyapatite.

3. The secondary battery as described in claim 1 or 2, wherein, The deacidifying agent also includes at least one of polyethyleneimine and polyimide.

4. The secondary battery according to any one of claims 1 to 3, wherein, The deacidifying agent accounts for 1%-20% of the mass of the functional layer.

5. The secondary battery according to any one of claims 1 to 4, wherein, The functional layer also includes inorganic particles, which include at least one of alumina and boehmite.

6. The secondary battery as described in claim 5, wherein, The inorganic particles constitute 50%-95.8% of the mass of the functional layer.

7. The secondary battery as described in claim 5, wherein, The particle size D of the inorganic particles V 50 is 0.2μm-0.6μm.

8. The secondary battery according to any one of claims 5 to 7, wherein, The functional layer also includes an adhesive, which includes polyacrylic adhesives.

9. The secondary battery as described in claim 8, wherein, The adhesive accounts for 3%-8% of the mass of the functional layer.

10. The secondary battery as described in claim 8 or 9, wherein, The functional layer also includes a dispersant, which includes carboxymethyl cellulose.

11. The secondary battery as claimed in claim 10, wherein, The dispersant accounts for 0.2%-0.8% of the mass of the functional layer.

12. The secondary battery according to any one of claims 1 to 11, wherein, The thickness of the functional layer is 0.5μm-3.0μm.

13. The secondary battery according to any one of claims 1 to 11, wherein, The air permeability of the isolation membrane is 200secs / 100cc-300secs / 100cc.

14. A method for preparing a secondary battery, wherein, include: A separating membrane is provided, the separating membrane comprising a base membrane and a functional layer disposed on at least one surface of the base membrane, the functional layer comprising an acid remover comprising a phosphate; We provide positive electrode plates, negative electrode plates, and electrolytes; The positive electrode, negative electrode, and separator are assembled into an electrode assembly; The electrode assembly is placed in the outer packaging, the electrolyte is injected, and then the battery is sealed to obtain a secondary battery.

15. The method for preparing a secondary battery as described in claim 14, wherein, The step of providing the isolation membrane includes: We provide deacidifying agents, inorganic particles, binders, dispersants, and base films; The deacidifying agent, inorganic particles, binder, and dispersant are added to a solvent and stirred until homogeneous to obtain a functional slurry. The functional slurry is coated onto at least one side of the base film and dried to obtain a release film.

16. The method for preparing a secondary battery as described in claim 15, wherein, The step of adding the deacidifying agent, inorganic particles, binder, and dispersant to a solvent and stirring until homogeneous to obtain the functional slurry includes: First, add the dispersant to the solvent and stir for 10-30 minutes. Then, add the deacidifying agent and stir for 20-60 minutes. Next, add the inorganic particles and stir for 20-60 minutes. Finally, add the binder and stir for 30-60 minutes to obtain the functional slurry.

17. An electrical appliance, wherein, This includes the secondary battery as described in any one of claims 1 to 13 or the secondary battery prepared by the preparation method described in any one of claims 14 to 16.

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