WO2024145894A1

WO2024145894A1 - Separator and preparation method therefor, battery, and electric device

Info

Publication number: WO2024145894A1
Application number: PCT/CN2023/070858
Authority: WO
Inventors: 吉星; 李婷; 郭满毅; 胡海; 钟华
Original assignee: 宁德时代新能源科技股份有限公司
Priority date: 2023-01-06
Filing date: 2023-01-06
Publication date: 2024-07-11
Also published as: CN119487691A

Abstract

Disclosed in the present application are a separator and a preparation method therefor, a battery, and an electric device. The separator of the present application comprises a base film and a coating disposed on at least one surface of the base film, wherein the coating contains polymer particles, and the polymer particles have a melting point of 90-120°C. The separator of the embodiments of the present application comprises the coating, which can be molten at the melting temperature of the polymer particles and seal pores contained in the base film, thereby reducing the risk of thermal runaway of a battery and improving the safety performance of the battery. The preparation method for the separator can ensure the stability of the separator structure and other performances. The battery comprises the separator of the present application.

Description

Diaphragm and preparation method thereof, battery and electrical device

Technical Field

The present application relates to the field of battery technology, and in particular to a diaphragm and a preparation method thereof, a battery, and an electrical device.

Background technique

In the context of energy conservation and emission reduction, new energy technologies are developing rapidly, among which the research breakthroughs and applications of battery technology are the most significant, and lithium-ion batteries are the batteries with the most prominent development momentum.

As battery applications become more and more extensive, especially in recent years with the rapid development of electric vehicles, power batteries have developed rapidly and the demand has increased dramatically. However, the safety performance of batteries has also received more and more attention, and the safety performance of batteries has become one of the important factors restricting the expansion of battery applications.

Among the safety issues of batteries, the most prominent one is the runaway exothermic reaction inside the battery. The specific reasons include at least: lithium dendrites are generated on the surface of the negative electrode, which pierce the diaphragm and cause the battery to short-circuit, or the battery is short-circuited when it is damaged by external forces; the electrolyte will undergo oxidation and decomposition under high temperature and high pressure to release a large amount of heat, thereby causing thermal runaway. These exothermic reactions will cause the temperature and pressure inside the battery to increase sharply. If they cannot be released in time, thermal runaway can easily occur, causing the battery to burn or even explode.

Summary of the invention

In view of the above problems, the embodiments of the present application provide a diaphragm and a method for preparing the same, a battery, and an electrical device to improve the electrochemical performance and safety performance of the diaphragm in battery production or operation.

In a first aspect, the present invention provides a separator, which comprises a base film and a coating disposed on at least one surface of the base film, wherein the coating contains polymer particles, and the melting point of the polymer particles is 90°C to 120°C, and optionally 100°C to 115°C.

The coating of the separator of the embodiment of the present application contains polymer particles in the melting point range, which can melt when the melting point temperature is reached, thereby closing the pores contained in the base film, preventing or reducing chemical reactions inside the battery, including the crosstalk reaction between the positive and negative electrodes of the battery, thereby reducing the risk of thermal runaway of the battery and improving the safety performance of the battery. On this basis, the polymer particles can give the separator good air permeability in an environment below the melting point temperature, and can effectively ensure the transfer of lithium ions between the positive and negative electrodes of the battery during normal operation, thereby significantly improving the electrochemical performance and safety performance of the battery.

In some embodiments, the polymer particles satisfy at least one of the following conditions (1) to (5):

(1) The volume distribution particle size D _v 50 of the polymer particles is 0.1 μm to 5 μm, and can be 0.3 μm to 3 μm;

(2) The morphology of the polymer particles includes at least one of chain, spherical, quasi-spherical, fibrous, tubular, rod-shaped, amorphous, and pyramidal;

(3) The polymer material of the polymer particles contains non-ionic groups, and optionally, the non-ionic groups include at least one of ethoxy, hydroxyl, and carboxylate groups;

(4) The weight average molecular weight of the polymer of the polymer particles is 1000 to 10000, and can be 1500 to 8000;

(5) The polymer of the polymer particles includes at least one of polystyrene, polyolefin, polyimide, melamine resin, phenol resin, cellulose, polyester, polyphenylene sulfide, polyaromatic amide, polyamideimide, copolymer of butyl acrylate and ethyl methacrylate, and their respective modified polymers.

The polymer particles have any of the above characteristics, which improves the dispersibility of the polymer particles, and in a temperature environment below the melting point of the polymer particles, can improve the air permeability of the coating, thereby improving the air permeability of the diaphragm; in an environment at the melting point of the polymer particles, the melting response of the abnormal increase in the temperature of the diaphragm is improved. Among them, when the polymer material of the polymer particles contains non-ionic groups, it can improve the dispersibility of the polymer particles in the coating, improve the uniformity of the coating, and thus improve the overall air permeability of the diaphragm.

In some embodiments, the coating layer further comprises an inorganic particle filler. The presence of the inorganic particle filler can improve the air permeability and stability of the diaphragm, and at the same time can improve the mechanical properties of the diaphragm such as heat shrinkage resistance.

In some embodiments, the inorganic particle filler satisfies at least one of the following conditions:

The dry weight ratio of the inorganic particle filler to the polymer particles is (15 to 25): (25 to 35);

The volume distribution particle size D _v 50 of the inorganic particle filler is 1 μm to 1.5 μm;

The inorganic particle filler includes at least one of inorganic particles having a dielectric constant of 5 or more, inorganic particles having ion conductivity but not storing ions, and inorganic particles capable of electrochemical reaction.

The inorganic particle filler has any of the above characteristics and can further improve the air permeability and mechanical properties of the diaphragm, such as heat shrinkage resistance.

In an exemplary embodiment, the polymer contained in the polymer particles is low-density polyethylene. In an exemplary embodiment, the low-density polyethylene is non-ionic low-density polyethylene.

The low-density polyethylene particles or further nonionic low-density polyethylene particles can further improve the synergistic effect of the air permeability between the polymer particles and the inorganic particles as shown above, and can also improve the liquid absorption and storage capacity of the membrane.

In some embodiments, the coating layer further comprises a binder. By adding a binder to the coating layer, the mechanical strength of the diaphragm can be improved, and the air permeability and stability of the diaphragm can be adjusted.

In the embodiment, the binder satisfies at least one of the following conditions:

The dry weight ratio of the binder to the polymer particles is (15 to 25): (25 to 35);

The binder is a water-based binder;

The thermal decomposition temperature of the binder is higher than 160°C;

The binder includes at least one of polyvinyl alcohol, polyacrylic acid-polyacrylonitrile copolymer, polyacrylate-polyacrylonitrile copolymer, polyether acrylate, polyurethane, polyacrylate, polycarbonate, polyethylene oxide, rubber, polyacrylic acid, polyacrylonitrile, gelatin, chitosan, sodium alginate, cyanoacrylate, polymerized cyclic ether derivatives, and hydroxyl derivatives of cyclodextrin.

The adhesive has any of the above characteristics, and can further enhance the mechanical properties of the coating contained in the diaphragm and the base film, thereby improving the air permeability and stability of the diaphragm.

In some embodiments, the coating has a thickness of 2 μm to 5 μm.

In some embodiments, the coating is disposed on one surface of the base film.

By adjusting the coating thickness and the position on the base film, the coating (i.e. the diaphragm) air permeability and the electrolyte wettability and storage capacity can be improved, thereby reducing the risk of thermal runaway of the battery.

In some embodiments, the base film satisfies at least one of the following conditions:

The thickness of the base film is 4 μm to 7 μm;

The air permeability of the base film is 180s/100cc to 240s/100cc;

The material of the base film includes at least one of non-woven fabric, polyolefin, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene ether, polyphenylene sulfide, and polyethylene naphthalene.

The base film with these characteristics can fully exert the role of battery separator and improve the mechanical properties such as compression resistance and air permeability of the separator.

In a second aspect, an embodiment of the present application provides a method for preparing a diaphragm. The method for preparing a diaphragm in an embodiment of the present application comprises the following steps:

providing a basement membrane;

Providing a coating slurry, wherein the coating slurry contains polymer particles, and the melting point of the polymer particles is 90° C. to 120° C., and optionally 100° C. to 115° C.;

The coating slurry is coated on at least one surface of the base film, and dried to form a coating to obtain a separator.

The diaphragm prepared by the diaphragm preparation method of the embodiment of the present application has the good air permeability and stability as the diaphragm of the embodiment of the above text application, and at the same time effectively reduces the risk of thermal runaway of the battery and improves the electrochemical performance and safety performance of the battery.

In some embodiments, the coating slurry is formed by mixing polymer particles, inorganic particle fillers and binders in a solvent; wherein the mass ratio of the polymer particles, inorganic particle fillers and binders in the coating slurry is (25 to 35):(15 to 25):(15 to 25).

In some embodiments, the solid content of the coating slurry is 30 wt % to 40 wt %.

In some embodiments, the coating slurry has a viscosity of 100 mPa·s to 1000 mPa·s at 25°C.

The coating slurry having the above characteristics can improve the film-forming quality, the quality of the coating and the properties such as air permeability.

In some embodiments, when the polymer particles are polymer particles containing nonionic groups, the polymer particles are prepared by a method comprising the following steps:

The polymer precursor particles, the ethoxy-containing polymer and the initiator are mixed and reacted to obtain polymer particles containing nonionic groups;

The polymer particles containing nonionic groups are emulsified with a nonionic surfactant to obtain a nonionic polymer emulsion.

By using ethoxylated polymers to carry out polymerization reactions with polymer precursor particles, the nonionic groups contained in the polymer particles can be increased, especially the processing performance of the polymer particles can be improved, thereby improving the dispersibility of the polymer particles in the coating slurry, thereby improving the film-forming quality of the coating slurry, and improving the air permeability and other properties of the coating.

In some embodiments, the polymer precursor particles, the ethoxy-containing polymer and the initiator are mixed in a mass ratio of (300 to 400):(90 to 125):(20 to 100).

In some embodiments, the material of the polymer precursor particles includes at least one of polystyrene, polyolefin, polyimide, melamine resin, phenol resin, cellulose, polyester, polyphenylene sulfide, polyaromatic amide, polyamideimide, and a copolymer of butyl acrylate and ethyl methacrylate.

In some embodiments, the ethoxy-containing polymer includes at least one of allyl polyethylene glycol and bisallyl polyether.

In some embodiments, the initiator includes at least one of di-tert-butyl peroxide and diisopropylbenzene peroxide.

In some embodiments, the reaction temperature may be 130°C to 160°C.

In some embodiments, the polymer particles and the nonionic surfactant are emulsified in a mass ratio of (4 to 6):1.

The above-mentioned reactant types, mixing ratios and reaction conditions can increase the non-ionic group grafting rate and content of the polymer particles, improve the processing performance and dispersibility of the polymer particles, thereby improving the film-forming quality of the coating slurry and the air permeability of the formed coating.

In the embodiment, the nonionic polymer emulsion satisfies at least any one of the following conditions (1) to (4):

(1) The viscosity of the nonionic polymer emulsion at 25° C. is 10 mPa·s to 100 mPa·s;

(2) The solid content of the nonionic polymer emulsion is 35wt% to 40wt%;

(3) The pH value of the nonionic polymer emulsion is 5 to 6;

(4) The nonionic surfactant includes a molecular structure of

Wherein, _R1 is a carbon chain alkyl group, _R2 is a hydrophilic group, and n is a positive integer from 3 to 20.

In an exemplary embodiment, the carbon chain alkyl group is a long carbon chain alkyl group of C12 to C18.

In the exemplary embodiment, the R ₂ is at least one of a carboxyl group, an amine group, an aldehyde group, an alcohol group, an amino group, and an amide group.

In the exemplary embodiment, the nonionic surfactant includes at least one of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, fatty acid polyoxyethylene ester, castor oil polyoxyethylene ether, fatty amine polyoxyethylene ether, sorbitan fatty acid ester, and polyoxyethylene sorbitan fatty acid ester.

By selecting the type of nonionic surfactant, the stability of the nonionic polymer emulsion can be improved, and its dispersibility in the coating slurry and the stability of the coating slurry can be improved, thereby improving the quality and air permeability of the formed coating.

In some embodiments, the binder is added in the form of a binder aqueous solution, and the binder aqueous solution has at least one of the following conditions:

The viscosity of the binder aqueous solution is 3000mPa·s to 10000mPa·s;

The solid content of the binder aqueous solution is 40 wt % to 50 wt %.

In some embodiments, the coating slurry is applied at a rate of 50 m/min to 100 m/min; and/or

The drying temperature is 60°C to 70°C; and/or

The drying time is 1 min to 3 min.

By adjusting the coating process conditions, the film quality, thickness and air permeability can be adjusted and optimized.

In a third aspect, an embodiment of the present application provides a battery. The battery of the embodiment of the present application includes a positive electrode, a negative electrode, and a separator stacked between the positive electrode and the negative electrode, wherein the separator is the separator described in the embodiment of the present application or a separator prepared by the separator preparation method of the embodiment of the present application. Since the embodiment of the present application contains the separator of the embodiment of the present application, the battery has high safety and good electrochemical properties such as capacity retention rate.

In an embodiment, the coating is disposed on one surface of the separator, and the coating faces the negative electrode. By only combining the coating on one surface of the separator, the overall thickness of the separator can be effectively reduced, thereby increasing the energy density of the battery.

In a fourth aspect, an embodiment of the present application provides an electric device, wherein the electric device comprises a battery according to an embodiment of the present application, and the battery is used to provide electric energy. The safety of the electric device according to an embodiment of the present application is significantly improved.

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

BRIEF DESCRIPTION OF THE DRAWINGS

Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the drawings:

FIG1 is a schematic flow chart of a method for preparing a diaphragm according to an embodiment of the present application;

FIG2 is a schematic structural diagram of an implementation of a secondary battery in an embodiment of the present application;

FIG3 is an exploded schematic diagram of the secondary battery shown in FIG2 ;

FIG4 is a schematic structural diagram of an implementation scheme of a battery module according to an embodiment of the present application;

FIG5 is a schematic structural diagram of an implementation scheme of a battery pack according to an embodiment of the present application;

FIG6 is a schematic diagram of the exploded structure of the battery pack shown in FIG5 ;

FIG7 is a schematic diagram of an embodiment of an electric device including a secondary battery according to an embodiment of the present application as a power source;

FIG8 is a scanning electron microscope (SEM) image of the diaphragm in Example A1 of the present application; wherein FIGa is a SEM image of the diaphragm at room temperature, and FIGb is a SEM image of the diaphragm after being heated at 130° C. for 15 minutes;

Figure 9 is a scanning electron microscope (SEM) image of the diaphragm in comparative example A1 of the present application; wherein, Figure a is a SEM image of the diaphragm at room temperature, and Figure b is a SEM image of the diaphragm after being heated at 130°C for 15 minutes.

The reference numerals in the specific implementation manner are as follows:

10. secondary battery cell, 11. housing, 12. electrode assembly, 13. cover plate;

20. Battery module;

30. battery pack, 31. box body, 32. lower box body.

Detailed ways

The following embodiments of the technical solution of the present application will be described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

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

In the description of the embodiments of the present application, the term "and/or" is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and/or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character "/" in this article generally indicates that the associated objects before and after are in an "or" relationship.

In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present application.

In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

In ion batteries such as lithium-ion batteries, the separator is one of the important components. It is set between the positive and negative pole pieces to separate the positive and negative electrodes of the battery, prevent the two poles from contacting and short-circuiting, and pass the function of Li ⁺ . Therefore, in addition to having good electrolyte wettability, liquid retention, and mechanical strength, the separator also needs to have more and more performance such as thermal stability, which has an important impact on battery safety, as more and more attention is paid to battery safety performance.

Currently, the method of improving the thermal stability and other properties of the diaphragm is to modify the diaphragm, such as doping or coating modifiers such as flame retardant additives, fiber-like materials, electrochemically inert ceramics, etc. during the preparation of the diaphragm, in order to achieve the purpose of improving the thermal stability and other properties of the diaphragm and thus improving battery safety.

Although current methods such as doping or coating can improve the thermal stability and other properties of the diaphragm to a certain extent, the inventors found in their research that when the exothermic reaction inside the battery accumulates to a certain extent, the modified diaphragm cannot block the continued reaction inside the battery in time, making it difficult to delay the exothermic reaction inside the battery and reduce the possibility of internal short circuit or even thermal runaway. Therefore, it is not ideal for improving the safety of battery thermal runaway.

In order to improve the effect of the diaphragm to inhibit thermal runaway of the battery, the surface of the diaphragm is currently modified, such as adding a modified coating. However, the inventors found in their research that adding a modified coating on the diaphragm has an adverse effect on the air permeability of the diaphragm, and when the battery is under pressure during assembly and normal operation, the modified coating reduces the air permeability of the diaphragm and thus reduces the permeability of the diaphragm to the electrolyte, further reducing the electrochemical properties of the battery such as cycle performance, affecting the normal operation of the battery and the performance of the normal performance of the battery.

Therefore, in order to reduce the risk of thermal runaway of the battery, improve the safety performance of the battery, and improve the air permeability and stability of the diaphragm, the inventors found through research that adding a coating containing polymer particles to the diaphragm ensures good air permeability of the diaphragm and ensures good air permeability and stability during normal production and use of the battery; when overheating occurs inside the battery, the coating can also melt and seal the pores of the diaphragm in time to form a sealing barrier layer, reducing or completely blocking the reaction inside the battery, thereby reducing the risk of thermal runaway of the battery and improving the safety performance of the battery.

Diaphragm

In a first aspect, an embodiment of the present application provides a separator. The separator of the embodiment of the present application comprises a base film and a coating disposed on at least one surface of the base film. The coating contains polymer particles, and the melting point of the polymer particles is 90°C to 120°C.

In the diaphragm of the embodiment of the present application, the base film contained therein constitutes the matrix of the diaphragm of the embodiment of the present application and plays the usual role of the diaphragm. The coating is arranged on the base film, which plays a modifying role on the base film, i.e., the diaphragm matrix. For example, when the temperature reaches the range of 90°C to 120°C, the polymer particles melt and close the pores contained in the base film.

The melting point of the polymer particles contained in the coating of the diaphragm of the embodiment of the present application is 90°C to 120°C. When the temperature inside the battery rises abnormally to the melting point of the polymer particles, the polymer particles can melt in time and close the pores contained in the base film. When the polymer particles melt and close the pores contained in the base film, the diaphragm plays a barrier role, thereby effectively reducing or preventing the chemical reactions inside the battery, including the chemical reactions in the electrolyte, the migration of metal ions, and the crosstalk reaction between the positive and negative electrodes, etc., to alleviate or terminate thermal runaway and improve the safety performance of the battery. Among them, the migration of metal ions includes lithium ions and metal precipitation from active materials, etc., to prevent them from passing through the diaphragm and depositing on the surface of the electrode, especially the negative electrode, or further forming dendrites. The crosstalk reaction between the positive and negative electrodes refers to the release of oxygen when the active material of the positive electrode of the battery undergoes a phase change at high temperature. The oxygen can diffuse to the negative electrode through the diaphragm and react with the negative electrode, etc., and release a large amount of heat; it also includes the hydrogen released from the negative electrode at high temperature, which diffuses to the positive electrode through the diaphragm, reacts with the positive electrode, etc., and releases a large amount of heat.

At the same time, since the polymer particles with the melting point range exist in particle morphology, the coating, i.e., the separator, has good air permeability. Moreover, during the normal production and use of the battery, the separator ensures good transfer of lithium ions in the electrolyte between the positive and negative electrodes, thereby improving the electrochemical properties of the battery such as charge and discharge and cycle performance.

Therefore, the polymer particles having a melting point of 90°C to 120°C, optionally 100°C to 115°C, and in the exemplary embodiment, typical but non-limiting melting points such as 90°C, 92°C, 94°C, 96°C, 98°C, 100°C, 102°C, 104°C, 106°C, 108°C, 110°C, 112°C, 115°C, 117°C, 120°C, etc., have a coating with good air permeability, and can ensure the good air permeability of the diaphragm in battery production and normal operation, and ensure the normal electrochemical performance of the battery. The inventors have found that if the melting point is too low, such as below 90°C, or the melting point is too high, such as above 120°C, the coating formed by the polymer particles will reduce the air permeability of the diaphragm, thereby reducing the air permeability of the diaphragm in the battery production process or normal operation, thereby reducing the electrochemical performance of the battery under normal operation. Moreover, when the melting point is lower than 90°C, the polymer particles will melt during normal operation of the battery, thus affecting the electrochemical performance of the battery; or when the melting point of the polymer particles is too high, such as higher than 120°C, the thermal sensitivity of the coating will decrease or even fail, resulting in the inability to melt in time to seal the pores of the base membrane when the battery experiences thermal runaway.

In some embodiments, the morphology of the polymer particles contained in the coating may include at least one of chain, spherical, quasi-spherical, fibrous, tubular, rod-shaped, amorphous, and pyramidal. The polymer particles with these morphologies can improve the good air permeability of the coating, i.e., the diaphragm, during normal operation of the battery, and improve the electrochemical performance of the battery; when the temperature inside the battery abnormally rises to the melting point of the polymer particles, the polymer particles with these morphologies can increase the melting rate to accelerate the closure of the base film pores. Therefore, the polymer particles with this morphology can further reduce the risk of thermal runaway of the battery and improve the safety performance of the battery.

In some embodiments, the volume distribution particle size D _v 50 of the polymer particles contained in the coating may be 0.1 μm to 5 μm, and may be 0.3 μm to 3 μm. In exemplary embodiments, the particle size may be 0.1 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, etc. Typical but non-limiting particle sizes. By controlling the particle size of the polymer particles, such as controlling it within this range, the uniformity of the distribution of the polymer particles in the coating can be improved, the air permeability of the diaphragm can be improved, and the hot melt response rate of the coating can also be improved.

In some embodiments, the polymer material of the polymer particles in the above embodiments contains non-ionic groups. In the exemplary embodiments, the non-ionic group may include at least one of ethoxy, hydroxyl, and carboxylate groups. The material of the polymer particles contains non-ionic groups, such as these types of non-ionic groups, which can improve the hydrophilicity and dispersibility of the polymer particles, thereby improving the uniformity of the polymer particles in the coating, thereby further improving the air permeability of the coating, thereby improving the good air permeability of the diaphragm during battery production and normal operation, and improving the transferability of lithium ions between the positive and negative electrodes, so as to improve the volatilization effect of the above-mentioned effects of the diaphragm in the embodiment of the present application. In the embodiment, the non-ionic group can be a grafted side chain of the polymer, or it can be connected to the main chain of the polymer.

In some embodiments, the polymer material of the polymer particles in the above embodiments may be a polymer with a weight average molecular weight of 1000 to 10000, optionally 1500 to 8000. In the exemplary embodiment, the polymer may include at least one of polystyrene, polyolefin, polyimide, melamine resin, phenolic resin, cellulose, polyester, polyphenylene sulfide, polyaromatic amide, polyamide-imide, copolymer of butyl acrylate and ethyl methacrylate and their respective modified polymers. By selecting the polymer material of the polymer particles, such as selecting these polymers, the melting point of the polymer particles in the above embodiments can be effectively controlled in the range of 90°C to 120°C, and the hot melt response rate of the polymer particles can be further increased. On this basis, the air permeability of the coating can be further improved, thereby improving the air permeability and stability of the diaphragm, thereby improving the volatilization effect of the above-mentioned effect of the diaphragm in the embodiment of the present application.

In addition, the polymer particles in the above embodiments can be solid particles, and of course can also be hollow particles. In the embodiments of the present application, solid particles can improve the stability of the polymer particle morphology relative to hollow particles, thereby improving the stability of the diaphragm during battery production and normal operation, including the air permeability, such as the polymer particles will not be deformed due to the extrusion force during battery production or use, thereby causing the basement membrane to block the pores. Therefore, in the embodiments of the present application, solid polymer particles are relatively preferred relative to hollow polymer particles.

In some embodiments, the coating contained in the separator of each embodiment further contains an inorganic particle filler. By adding the inorganic particle filler to the coating, on the one hand, the air permeability and stability of the coating can be improved, thereby improving the air permeability and stability of the separator in battery production and normal operation; on the other hand, it can play a synergistic role with the above polymer particles, improving the liquid storage capacity and mechanical properties such as heat shrinkage resistance of the separator. In addition, the inorganic particle filler is ideally formed into a mixture with the above polymer particles in the coating.

In the embodiment, the content of the inorganic particle filler in the coating layer can be controlled to be a dry weight ratio of the inorganic particle filler to the polymer particles of (15 to 25): (25 to 35). By controlling the content ratio of the inorganic particle filler and the polymer particles in the coating layer, the synergistic effect between the two can be improved on the basis of fully volatilizing the effects of the two as described above, thereby ensuring that the diaphragm has good air permeability, thermal stability and liquid storage capacity.

In the embodiment, the volume distribution particle size D _v 50 of the inorganic particle filler is 1 μm to 1.5 μm, and in the exemplary embodiment, it can be 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm and other typical but non-limiting particle sizes. By adjusting the inorganic particle filler, it is compounded with the polymer particle size, such as controlling the D _v 50 to be in the range of 1 μm to 1.5 μm, and acting together with the polymer particles in the above particle size range to improve the air permeability of the diaphragm. For example, after testing, the air permeability of the diaphragm can reach the air permeability shown in Table 1 below. Moreover, when the battery is abnormally heated to the melting point temperature of the polymer particles, the inorganic particle filler in this particle range can fully play the role of the skeleton to improve the melting of the polymer particles and close the pores of the base film, and at the same time, play the role of isolating the positive and negative electrodes together with the base film, thereby reducing the risk of short-circuit thermal runaway.

In an embodiment, the above inorganic particle filler may include at least one of inorganic particles having a dielectric constant of 5 or more, inorganic particles having ion conductivity but not storing ions, and inorganic particles capable of electrochemical reaction.

In an exemplary embodiment, the inorganic material of the inorganic particles having a dielectric constant of 5 or more includes at least one of boehmite, aluminum oxide, zinc oxide, silicon oxide, titanium oxide, zirconium oxide, barium oxide, calcium oxide, magnesium oxide, nickel oxide, tin oxide, cerium oxide, yttrium oxide, hafnium oxide, aluminum hydroxide, magnesium hydroxide, silicon carbide, boron carbide, aluminum nitride, silicon nitride, boron nitride, magnesium fluoride, calcium fluoride, barium fluoride, barium sulfate, magnesium aluminum silicate, lithium magnesium silicate, sodium magnesium silicate, bentonite, hectorite, zirconium titanate, barium _titanate , Pb(Zr, _Ti ) _O3 , _Pb1 _- mLamZr1-nTinO3, Pb( _Mg3Nb2 _/ ₃ ) _O3 -PbTiO3, and modified inorganic particles thereof, 0＜m＜1, 0＜n＜1.

In the exemplary embodiments, the inorganic material of the inorganic particles having ion conductivity but not storing ions includes _Li3PO4 _, lithium titanium phosphate _Lix1Tiy1 ( _PO4 ) ₃ , lithium aluminum titanium _phosphate _Lix2Aly2Tiz1 ( _PO4 ₎ ₃ , (LiAlTiP) _x3Oy3 type glass, _lithium _lanthanum _titanate _Lix4Lay4TiO3 , _lithium _germanium _{thiophosphate} _{Lix5Gey5Pz2Sw} _, _lithium _nitride _Lix6Ny6 _, _SiS2 type glass _Lix7Siy7Sz3 _and _P2S5 type glass _Lix8Py8Sz _. At least one of _z4 , 0＜x1＜2, 0＜y1＜3, 0＜x2＜2, 0＜y2＜1, 0＜z1＜3, 0＜x3＜4, 0＜y3＜13, 0＜x4＜2, 0＜y4＜3, 0＜x5＜4, 0＜y5＜1, 0＜z2＜1, 0＜w＜5, 0＜x6＜4, 0＜y6＜2, 0＜x7＜3, 0＜y7＜2, 0＜z3＜4, 0＜x8＜3, 0＜y8＜3, 0＜z4＜7;

In an exemplary embodiment, the inorganic material of the electrochemically reactive inorganic particles includes at least one of lithium-containing transition metal oxides, lithium-containing phosphates, carbon-based materials, silicon-based materials, tin-based materials, and lithium-titanium compounds.

By selecting the material type of the inorganic particle filler, the above-mentioned effect of the inorganic particle filler is improved, and the synergistic effect between the inorganic particle filler and the polymer particles is further improved, the air permeability and stability of the diaphragm of the embodiment of the present application are improved, and the electrochemical performance and safety performance of the battery are improved. Among them, the inorganic particle filler of some of the above-mentioned inorganic materials also has good liquid absorption and storage capacity, thereby improving the liquid absorption and storage capacity of the diaphragm.

Based on the above polymer particles and inorganic particle fillers, in the exemplary embodiment, the polymer contained in the polymer particles contained in the coating is low-density polyethylene, specifically low-density polyethylene particles, and further can be non-ionic low-density polyethylene containing non-ionic groups. Among them, low-density polyethylene refers to high-pressure polyethylene (LDPE), specifically polyethylene with a molecular weight of less than 10,000.

The above-mentioned inorganic particles are compounded with the low-density polyethylene particles to enhance the above-mentioned synergistic effect between the polymer particles and the inorganic particles, thereby improving the air permeability and liquid storage capacity of the coating of the embodiment of the present application, that is, the diaphragm, while increasing the hot melt response rate of the diaphragm, thereby improving the electrochemical performance and safety performance of the battery.

In some embodiments, the coating contained in the above-mentioned diaphragms further contains a cured binder. By adding a binder to the coating, the bonding force between the polymer particles or the inorganic particle filler can be effectively enhanced, thereby improving the mechanical properties of the coating, and enhancing the bonding force between the coating and the base film, thereby improving the stability of the coating, i.e., the diaphragm, including air permeability.

In the embodiment, the dry weight ratio of the solidified binder to the polymer particles is (15 to 25): (25 to 35). By controlling the content of the binder in the coating, the mechanical properties of the coating and the bonding force with the base film can be further enhanced to further adjust the air permeability of the coating, i.e., the diaphragm.

In the embodiment, the thermal decomposition temperature of the cured binder is higher than 160° C. By selecting the decomposition temperature characteristics of the binder, the diaphragm has good thermal stability. When the internal temperature of the battery abnormally rises to the melting point of the polymer particles, the barrier effect of the diaphragm is improved, and the risk of thermal runaway of the battery is reduced.

In the embodiment, the binder can be selected from water-based binders. Among them, the water-based binder can be a water-soluble binder or an emulsion binder, etc. In the exemplary embodiment, the binder can include polyvinyl alcohol, polyacrylic acid-polyacrylonitrile copolymer, polyacrylate-polyacrylonitrile copolymer, polyether acrylate, polyurethane, polyacrylate, polycarbonate, polyethylene oxide, rubber, polyacrylic acid, polyacrylonitrile, gelatin, chitosan, sodium alginate, cyanoacrylate, polymerized cyclic ether derivatives, and at least one of hydroxyl derivatives of cyclodextrin. These binders can enhance the bonding force between polymer particles or further inorganic particle fillers, thereby improving the mechanical properties of the coating and enhancing the bonding force between the coating and the base film. Further adjust the air permeability of the diaphragm, improve the role of the polymer particles melting and closing the base film pores when the temperature inside the battery abnormally rises to the melting point of the polymer particles, so as to improve the electrochemical performance and safety performance of the battery.

In the embodiment, when the coating contains both the above inorganic particle filler and the binder, in the coating, the dry weight ratio of the above polymer particles, inorganic particle filler and binder can be (25 to 35): (15 to 25): (15 to 25). By controlling the content ratio of the three components in the coating, the above effects of each component and the synergistic effect between the three components are further improved, thereby further improving the uniformity of the coating, improving the air permeability and air permeability uniformity of the diaphragm, and improving the mechanical properties.

Based on the coating schemes in the above embodiments, in some embodiments, the coating thickness can be 2 to 5 μm. In the exemplary examples, the coating thickness can be 2 μm, 3 μm, 4 μm, 5 μm, and other typical but non-limiting thicknesses. By controlling the coating thickness, the content of components such as polymer particles can be controlled, thereby adjusting and improving the polymer particles to fully play the role described above, further improving the permeability, stability and liquid storage capacity of the diaphragm, and at the same time improving the polymer particles contained in the coating when the battery is abnormally heated. Melt and effectively close the pores of the base film, reducing or preventing the risk of thermal runaway.

In addition, the coating contained in the separator of each embodiment above can be arranged on one surface of the base film, or on two opposite surfaces of the base film. Based on the battery energy density and dendrite formation characteristics, in the embodiment, the coating is arranged on one surface of the base film, that is, the coating is not arranged on the other opposite surface of the base film.

The base film contained in the separator of each embodiment above can be selected from the organic separator of the battery. For example, in the embodiment, the thickness of the base film can be 4μm to 7μm. In other embodiments, the air permeability of the base film can be 180s/100cc to 240s/100cc. In the exemplary embodiment, the material of the base film includes at least one of non-woven fabrics, polyolefins, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene ether, polyphenylene sulfide, and polyethylene naphthalene. The base films with these characteristics and materials can be combined with the above coating and play a synergistic role on the basis of giving full play to the role of the battery separator, so that the separator has good air permeability and stability, and improves the electrochemical performance and safety performance of the battery.

In some embodiments, the above-mentioned base membrane can also be a modified base membrane, such as a base membrane modified with at least one modifier such as flame retardants, fiber-like materials, electrochemically inert ceramics, etc., to improve the thermal stability of the base membrane, so as to cooperate with the above-mentioned coating to further improve the mechanical properties and safety performance of the diaphragm of the embodiment of the present application.

Preparation method of diaphragm

In a second aspect, the present invention provides a method for preparing a diaphragm. The process flow of the method for preparing a diaphragm in the present invention is shown in FIG1 . The method for preparing a diaphragm in the present invention may include the following steps:

S01: providing a basement membrane;

S02: providing coating slurry;

S03: coating the coating slurry on at least one surface of the base film, and forming a coating after drying to obtain a separator.

In the preparation method of the diaphragm of the embodiment of the present application, after the coating slurry forms a coating on the surface of the base film, the coating is bonded to the surface of the base film. Since the preparation method of the diaphragm according to the embodiment of the present application is to prepare the diaphragm of the embodiment of the present application, the formed coating contains polymer particles, and the melting point of the polymer particles is 90°C to 120°C, and can be 100°C to 115°C.

The diaphragm preparation method of the embodiment of the present application directly forms a film on the base film with a slurry containing polymer particles with a melting point of 90°C to 120°C, so that the prepared diaphragm is combined with a coating on at least one surface to achieve the coating's modification effect on the base film. Then the coating is the coating contained in the diaphragm of the above text application embodiment. Therefore, the diaphragm prepared by the diaphragm preparation method of the embodiment of the present application has the good air permeability and stability of the diaphragm of the above text application embodiment, or further has good liquid storage capacity, and can also effectively reduce the risk of thermal runaway of the battery and improve the electrochemical performance and safety performance of the battery. In addition, the process parameters of the diaphragm preparation method of the embodiment of the present application are controllable, and the quality and electrochemical performance of the prepared diaphragm are stable.

Step S01:

The base film in step S01 may be the base film contained in the diaphragm of the above text application embodiment, and therefore, the base film may be the base film contained in the diaphragm of the above text application embodiment. As in the embodiment, the thickness of the provided base film may be 4 μm to 7 μm, and its air permeability may be 180 s/100 cc to 240 s/100 cc, and its material may include at least one of non-woven fabric, polyolefin, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene ether, polyphenylene sulfide, and polyethylene naphthalene.

Step S02:

Since the coating slurry in step S02 is a slurry for forming the coating contained in the above text application embodiment diaphragm, the slurry must contain polymer particles and solvents. In the embodiment, it may further contain inorganic particle fillers and binders. Therefore, the polymer particles contained in the coating slurry, or the material types and content ratios of the inorganic particle fillers and binders further contained therein are the types and content ratios of the polymer particles, inorganic particle fillers and binders contained in the coating of the above text application embodiment diaphragm. Therefore, in order to save space, the types, content ratios, etc. of polymer particles, inorganic particle fillers and binders are no longer described here.

In order to improve the film-forming quality of the coating slurry, improve the quality of the coating and improve properties such as air permeability, in one embodiment, the solid content of the coating slurry can be 30wt% to 40wt%; in other embodiments, the viscosity of the coating slurry is 100mPa·s to 1000mPa·s.

In some embodiments, when the coating slurry in step S02 is formed by mixing polymer particles with inorganic particle fillers and binders in a solvent; then the mass ratio of polymer particles, inorganic particle fillers, binders and water in the coating slurry can be (25 to 35): (15 to 25): (15 to 25): (20 to 30). This ratio refers to the mixing ratio of the binder to the polymer particles and inorganic particle fillers before curing. By adjusting the ratio of the three, the film-forming quality of the coating slurry is improved, the quality of the formed coating is improved, and the air permeability and stability of the diaphragm are improved, reducing the risk of thermal runaway of the battery.

Among them, the adhesive should be an adhesive before curing, such as the aqueous adhesive before curing described above. In the exemplary embodiment, it can be an adhesive before curing including polyvinyl alcohol, polyacrylic acid-polyacrylonitrile copolymer, polyacrylate-polyacrylonitrile copolymer, polyether acrylate, polyurethane, polyacrylate, polycarbonate, polyethylene oxide, rubber, polyacrylic acid, polyacrylonitrile, gelatin, chitosan, sodium alginate, cyanoacrylate, polymerized cyclic ether derivatives, and at least one hydroxyl derivative of cyclodextrin.

For example, in the embodiment, the binder is added in the form of a binder aqueous solution to effectively adjust the viscosity of the coating slurry, improve the dispersion uniformity and stability of the coating slurry components, and improve the film-forming quality of the coating slurry. When the binder is added in the form of a binder aqueous solution, in the embodiment, the viscosity of the binder aqueous solution at 25°C can be 3000mPa·s to 10000mPa·s; in other embodiments, the solid content of the binder aqueous solution is 40wt% to 50wt%. By controlling and adjusting the viscosity of the binder aqueous solution or the solid content at the same time, the positive effect of the binder on the coating slurry can be further improved, including the slurry stability and dispersibility, and the uniformity of the coating can be improved.

In the embodiment, when the polymer particles contained in the coating slurry are polymer particles containing non-ionic groups, the polymer particles can be prepared according to a method comprising the following steps:

Step S021: mixing and reacting the polymer precursor particles, the ethoxy-containing polymer and the initiator to obtain polymer particles containing nonionic groups;

Step S022: emulsifying the polymer particles containing nonionic groups with a nonionic surfactant to obtain a nonionic polymer emulsion.

In the reaction process of step S021, the polymer precursor particles and the ethoxy-containing polymer undergo a polymerization reaction under the action of an initiator, so that the ethoxy-containing group is grafted onto the polymer particles.

In the embodiment, the polymer precursor particles, the ethoxy-containing polymer and the initiator are mixed in a mass ratio of (300 to 400):(90 to 125):(20 to 100).

In the embodiment, the reaction temperature in step S021 can be 130 to 160° C., and the reaction time should be sufficient, such as 2.5 to 3.5 hours at 130 to 160° C. Meanwhile, during the reaction, the molten reactants are stirred to improve the efficiency and uniformity of the reaction.

By controlling and adjusting the mixing ratio of the reactants in step S021, or further controlling the reaction conditions, the content of non-ionic groups such as ethoxy groups grafted onto the polymer particles can be increased on the basis of improving the polymer reaction efficiency, thereby improving the non-ionic group modification effect of the polymer particles, thereby improving the above effects of the polymer particles, especially improving the surface properties of the polymer particles, improving the dispersibility and dispersion stability of the polymer particles in the coating slurry, thereby improving the diaphragm quality of the coating slurry to improve the air permeability and stability of the coating, that is, the diaphragm.

In an exemplary embodiment, the material of the polymer precursor particles may include at least one of polystyrene, polyolefin, polyimide, melamine resin, phenol resin, cellulose, polyester, polyphenylene sulfide, polyaromatic amide, polyamideimide, and a copolymer of butyl acrylate and ethyl methacrylate.

The ethoxy-containing polymer may include at least one of allyl polyethylene glycol and bisallyl polyether.

The initiator may include at least one of di-tert-butyl peroxide and dicumyl peroxide.

The polymer precursor particles, ethoxylated polymer and initiator can undergo a polymer reaction in step S021 to improve the efficiency of graft modification. Among them, the ethoxylated polymer can effectively provide ethoxylated nonionic groups to achieve graft modification of the ethoxylated nonionic groups of the polymer precursor particles.

In step S022, during the emulsification process, the nonionic surfactant and the polymer particles containing nonionic groups form an emulsion in a solvent, wherein the solvent should be water.

In addition, the mixing ratio of the nonionic surfactant and the polymer particles containing nonionic groups, as well as the amount of added water solvent, can be controlled to adjust and control the relevant properties of the nonionic polymer emulsion, such as viscosity, solid content, pH value, etc., so as to improve the dispersion uniformity and stability of the polymer particles in the coating slurry, thereby improving the above-mentioned effect of forming the coating and improving the electrochemical performance and safety performance of the prepared diaphragm. For example, in the embodiment, by controlling and conditioning the conditions of the emulsification treatment in step S022, the nonionic polymer emulsion has at least one of the following properties:

(2) the solid content of the nonionic polymer emulsion is 35 wt % to 40 wt %;

(3) The pH value of the nonionic polymer emulsion is 5 to 6.

In an embodiment, the polymer particles and the non-ionic surfactant can be mixed and emulsified in a mass ratio of (4 to 6):1, and a demonstration example can be 4.5:1, which can effectively adjust the viscosity and solid content of the non-ionic polymer emulsion, thereby improving the dispersibility of the polymer particles and improving the uniformity and stability of the coating slurry.

In some embodiments, the nonionic surfactant may include a molecular structure of

Wherein, _R1 is a carbon chain alkyl group. In the exemplary embodiment, when it is a carbon chain alkyl group, _R1 is a long carbon chain alkyl group of C12 to C18.

R ₂ is a hydrophilic group. In the exemplary embodiment, R ₂ is at least one of a carboxyl group, an amine group, an aldehyde group, an alcohol group, an amino group, and an amide group.

n is a positive integer from 3 to 20. In the examples, n can be a typical but non-limiting positive integer such as 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, etc.

By selecting the type of nonionic surfactant, the stability of the nonionic polymer emulsion can be improved, and its dispersibility in the coating slurry can be improved, thereby improving the dispersion uniformity and stability of the polymer particles.

In addition, there is no chronological order between step S01 and step S02 above, and the order can be adjusted according to actual production, or they can be performed simultaneously.

Step S03:

The purpose of coating the coating slurry on the base film in step S02 is to form a wet film on the base film, that is, the above coating before drying. The coating method may be unlimited, and any method that can form a film of the coating slurry on the base film is within the scope disclosed in the embodiments of the present application, such as but not limited to brushing, roller coating, spraying, etc. In addition, the coating process conditions may be further adjusted to adjust and optimize the film quality, thickness, air permeability, etc.

As in the embodiment, the coating slurry in step S02 can be coated at a rate of 50 m/min to 100 m/min. This coating rate can improve the quality of the coating, adjust the air permeability and thickness, etc.

In the drying process, the main purpose is to remove the solvent in the wet film. Based on the melting temperature range characteristics of the polymer particles contained in the coating slurry, the drying process should be lower than the melting temperature of the polymer particles, and should ensure the quality and stability of the coating. For example, in the embodiment, the drying temperature can be 60°C to 70°C. In the exemplary embodiment, it can be but not limited to typical but non-limiting temperatures such as 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C, and 70°C. In the drying temperature range, the drying time should be sufficient, such as the drying time of 1 min to 3 min.

Battery

In a third aspect, the present application provides a battery, which includes a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, wherein the separator is the separator of the above-mentioned application embodiment.

In the embodiment, the diaphragm is combined with a coating only on one surface, and the surface of the diaphragm containing the coating faces the negative electrode. By facing the coating toward the negative electrode, the diaphragm can fully exert the role described in the diaphragm of the embodiment of the above application, and the deposition and formation of metal dendrites on the negative electrode can be further reduced, thereby improving the safety of the battery. At the same time, only combining the coating on one surface of the diaphragm can effectively reduce the overall thickness of the diaphragm and improve the energy density of the battery.

In the exemplary embodiment, the battery of the present application can be a secondary battery. When the battery of the present application is a secondary battery, it includes a positive electrode, a separator and a negative electrode. That is, the negative electrode contained in the secondary battery is the negative electrode of the above-mentioned application embodiment, that is, the negative electrode contains the modified artificial graphite of the above-mentioned application embodiment.

In this way, the battery of the embodiment of the present application, such as a secondary battery, has a high energy density, a high rate capability and good cycle stability.

In an embodiment, the secondary battery of the present application may include any one of a battery cell, a battery module, and a battery pack.

The battery cell refers to a battery housing and a battery cell encapsulated in the battery housing. The shape of the battery cell is not particularly limited, and it can be cylindrical, square or any other shape. A square battery cell 10 is shown in FIG. 2 .

In some embodiments, as shown in FIG3 , the outer packaging of the battery cell 10 may include a shell 11 and a cover plate 13. The shell 11 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 11 has an opening connected to the receiving cavity, and the cover plate 13 is used to cover the opening to close the receiving cavity. The positive electrode, the separator and the negative electrode contained in the secondary battery of the embodiment of the present application can form an electrode assembly 12 through a winding process and/or a lamination process. The electrode assembly 12 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 12. The number of electrode assemblies 12 contained in the battery cell 10 may be one or more, which can be adjusted according to actual needs.

The preparation method of the battery cell 10 is well known. In some embodiments, the positive electrode, the separator, the negative electrode and the electrolyte can be assembled to form the battery cell 10. As an example, the positive electrode, the separator and the negative electrode can be formed into the electrode assembly 12 through a winding process or a lamination process, and the electrode assembly 12 is placed in an outer package, dried and injected with electrolyte, and then vacuum packaged, left to stand, formed, shaped and other processes are performed to obtain the battery cell 10.

The battery module is assembled from the battery cells 10 , that is, it may contain a plurality of the battery cells 10 , and the specific number can be adjusted according to the application and capacity of the battery module.

In some embodiments, FIG. 4 is a schematic diagram of a battery module 20 as an example. As shown in FIG. 4 , in the battery module 20, a plurality of battery cells 10 may be arranged in sequence along the length direction of the battery module 20. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells 10 may be fixed by fasteners.

Optionally, the battery module 20 may further include a housing having an accommodation space, and the plurality of battery cells 10 may be accommodated in the accommodation space.

A battery pack is composed of the above-mentioned battery cells 10, that is, it may contain multiple battery cells 10, wherein multiple battery cells 10 may be assembled into the above-mentioned battery module 20. The specific number of battery cells 10 or battery modules 20 contained in the battery pack may be adjusted according to the application and capacity of the battery pack.

As shown in the embodiment, FIG. 5 and FIG. 6 are schematic diagrams of a battery pack 30 as an example. The battery pack 30 may include a battery box and a plurality of battery modules 20 disposed in the battery box. The battery box includes an upper box body 31 and a lower box body 32, and the upper box body 31 is used to cover the lower box body 32 and form a closed space for accommodating the battery module 20. The plurality of battery modules 20 may be arranged in the battery box in any manner.

Electrical devices

In a sixth aspect, the present application also provides an electric device, which includes the battery of the above-mentioned embodiment of the present application, and further can be a secondary battery. The battery can be used as a power source for the electric device, and can also be used as an energy storage unit for the electric device. Therefore, the electric device of the present application embodiment has a long standby or battery life.

The electric device may be, but is not limited to, a mobile device (such as a mobile phone, a laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, a satellite, an energy storage system, etc. The electric device may select a secondary battery, a battery module, or a battery pack according to its use requirements.

Fig. 7 is a schematic diagram of an electric device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirements of the electric device for high power and high energy density, a battery pack or a battery module may be used.

As another example, the electric device may be a mobile phone, a tablet computer, a notebook computer, etc. The electric device is usually required to be light and thin, and a secondary battery may be used as a power source.

Example

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

1. Diaphragm and its preparation method embodiment

Example A1

The present embodiment provides a diaphragm and a method for preparing the same. The diaphragm of the present embodiment includes a PE base film and a coating bonded to one surface of the PE base film. The thickness of the PE base film is 7 μm; the thickness of the coating is 2 μm. The coating contains nonionic polyethylene wax particles, and the polymer particles contain ethoxy groups. After testing, the melting point of the polymer particles is as shown in Table 1 below.

The diaphragm preparation method of this embodiment includes the following steps:

S1. Preparation of coating slurry:

S11. Preparation of polymer particles:

a. According to the mass ratio of polyethylene wax: allyl polyethylene glycol: initiator = 300:100:20, polyethylene wax, allyl polyethylene glycol, and di-tert-butyl peroxide initiator were mixed and heated to melt and stirred uniformly, and the intermediate product was obtained after constant temperature at 160°C and 3h;

b. Mix the intermediate product and the nonionic emulsifier in a mixing ratio of 4.5:1, heat to melt, stir to form a uniform emulsion, add water to adjust the viscosity to a suitable range of 10mPa·s to 100mPa·s, and a solid content of 35% to 40% to obtain a nonionic polyethylene wax emulsion;

S12. Preparation of coating slurry:

According to the weight ratio of polymer particles: polymethyl methacrylate: boehmite: water = 25%: 25%: 20%: 30%, non-ionic polyethylene wax emulsion, polymethyl methacrylate, boehmite and water are mixed, all materials are added into a double planetary stirring tank, and then stirred for 3 hours at a revolution of 30 rpm and a rotation of 2000 rpm, and vacuum defoaming is carried out throughout the process; the viscosity of the coating slurry is controlled at 500 mPa·s to 800 mPa·s.

S2. Film formation of coating slurry on the surface of base film:

The coating slurry in step S1 is coated on one side of a 7 μm PE base film to form a wet film, and then dried to form a 2 μm coating on one side of the PE base film; wherein the coating slurry coating speed is 80 m/min, the oven temperature is 65° C., and the total drying time is 2 min.

Example A2

This embodiment provides a diaphragm and a method for preparing the same. The diaphragm of this embodiment is identical to the diaphragm in embodiment A1 except that the melting point of the polymer particles contained in the coating is different. The melting point of the polymer particles contained in the coating of the diaphragm of this embodiment is 100° C. as shown in Table 1.

The preparation method of the diaphragm in this embodiment is prepared by referring to the preparation method of the diaphragm in Example A1.

Example A3

This embodiment provides a membrane and a method for preparing the same. The membrane in this embodiment is identical to the membrane in embodiment A1 except that the melting point of the polymer particles contained in the coating is different. The melting point of the polymer particles in this embodiment is 120° C. as shown in Table 1.

Example A4

This embodiment provides a diaphragm and a method for preparing the same. The diaphragm in this embodiment is identical to the diaphragm in embodiment A1 except that the polymer particles contained in the coating have different materials and melting points. Specifically, the polymer particles in this embodiment are made of low-melting-point polyester, and the melting point is 90° C. as shown in Table 1.

Example A5

This embodiment provides a diaphragm and a method for preparing the same. The diaphragm of this embodiment is identical to the diaphragm in Embodiment A1 except that the coating does not contain inorganic particles. The diaphragm coating is formed by coating slurry with a mass ratio of polymer particles: polymethyl methacrylate: boehmite: water = 45%: 25%: 0%: 30% according to the coating method in Embodiment A1.

Example A6

This embodiment provides a diaphragm and a method for preparing the same. The diaphragm in this embodiment is identical to the diaphragm in embodiment A1 except that the polymer particles contained in the coating are different. Specifically, the polymer particles in this embodiment are polyethylene wax particles with a melting point of 100° C. as shown in Table 1.

Example A7

This embodiment provides a diaphragm and a method for preparing the same. The diaphragm of this embodiment is identical to the diaphragm in embodiment A1 except for the thickness of the coating. Specifically, the thickness of the coating of the diaphragm of this embodiment is 5 μm.

Comparative Example A1

This comparative example provides a separator, which is different from the separator in Example A1 in that the separator coating does not contain polymer particles. The other features are exactly the same.

The preparation method of the diaphragm in this comparative example refers to the preparation method of the diaphragm in Example A1, and the difference from the preparation method in Example A1 is that when preparing the coating slurry, the components of the coating slurry are mixed according to the mass ratio of polymer particles: polymethyl methacrylate: boehmite: water = 0%: 25%: 45%: 30%. The steps and process conditions are the same.

Comparative Example A2

This comparative example provides a separator. Compared with the separator in Example A1, the separator in this comparative example has the same characteristics except that the polymer particles contained in the coating are different. Specifically, the material of the polymer particles in this comparative example is low-melting-point polyester, and the melting point is 85° C. as shown in Table 1. There is no need to perform the S11 modification step, and the S12 coating slurry configuration is directly performed.

Comparative Example A3

This comparative example provides a diaphragm. Compared with the diaphragm in Example A1, the diaphragm in this comparative example has the same characteristics except that the polymer particles contained in the coating are different. Specifically, the material of the polymer particles in this comparative example is polyphenylene sulfide, and the melting point is 125° C. as shown in Table 1. There is no need to perform the S11 modification step, and the S12 coating slurry configuration is directly performed.

Comparative Example A4

This comparative example provides a separator and a preparation method thereof. The separator in this comparative example has the same characteristics as the separator in Example A1 except that the melting point of the polymer particles contained in the coating is different. Specifically, the melting point is 125° C. as shown in Table 1.

2. Secondary battery cell example

Example B1 to Example B7 and Comparative Example B1 to Comparative Example B4;

The present embodiment B1 to embodiment B7 and comparative examples B1 to comparative examples B4 respectively provide a secondary battery monomer, each of which includes a battery cell formed by a positive electrode, a separator and a negative electrode, and also includes an electrolyte. Among them, the separators provided in embodiments A1 to embodiment A7 and comparative examples A1 to comparative examples A4 are the separators of secondary battery embodiments B1 to embodiment B7 and comparative examples B1 to comparative examples B4, respectively. Among them, the separator in the above embodiment A1 is used as the separator in the battery cell of the secondary battery embodiment B1, the separator in the embodiment A2 is used as the separator in the battery cell of the secondary battery embodiment B2, and so on, and the separator in comparative example A4 is used as the separator in the battery cell of the battery comparative example B4.

The positive electrode was prepared as follows:

Using methyl pyrrolidone (NMP) as solvent, LiNi _0.8 Co _0.1 Mn _0.1 O ₂ , carbon nanotubes (CNT) and binder (PVDF) are mixed in a mass ratio of 97:2:1 to prepare a positive electrode slurry with a solid content of 80%. The positive electrode slurry is evenly coated on an aluminum foil for double-sided coating, wherein the surface density of each single side is 0.131 g/1540.25 mm ² , and after sufficient drying, cold pressing and slitting, a positive electrode sheet is obtained as a positive electrode.

Negative electrode: artificial graphite, conductive agent SP, dispersant (CMC), and binder (SBR) are mixed in a mass ratio of 96:1:1:2 with water as solvent to prepare a negative electrode slurry with a solid content of 58%; the positive electrode slurry is evenly coated on aluminum foil for double-sided coating, wherein the surface density of each single side is 0.065g/ ^1540.25mm2 , and after sufficient drying, cold pressing, and slitting, a negative electrode sheet is obtained as the negative electrode.

Electrolyte: At room temperature, ethylene carbonate (EC)/diethyl carbonate (DEC) were mixed in a volume ratio of 1:1, and LiPF ₆ was added to the mixed solution to obtain a solution with a concentration of 1 mol/L as the electrolyte;

Secondary battery assembly: In a low-humidity constant temperature room, the positive and negative electrode plates prepared as above are stacked and wound in the order of "positive electrode-separator-negative electrode" to form a bare cell, and then filled with electrolyte to assemble into a lithium-ion secondary battery.

Separator and secondary battery monomer related performance tests

The separators and secondary battery cells provided in the above embodiments and comparative examples were tested respectively.

1. Diaphragm performance test:

1.1 The membranes in the above-mentioned Examples A1 to A7 and Comparative Examples A1 to A4 were respectively subjected to the relevant performance tests in Table 1. Among them, all test methods are in accordance with the national standard (if there is no national standard, the test is conducted according to the industry standard method). For example, the air permeability is tested using a membrane air permeability tester in accordance with the reference standard GB/T 36363-2018; the melting point can be obtained by testing with a universal differential scanning calorimeter (DSC) method with reference to the standard ISO 11357-3-2018; the molecular weight is tested using gel chromatography (GPC) and with reference to the GBT27843-2011 chemical polymer low molecular weight component content detection method; unless otherwise specified, in this application, the volume distribution particle size Dv50 of the organic particles is determined by a particle size analyzer-laser diffraction method. Specifically, the standard GB/T 19077-2016 can be referred to, and the laser diffraction scattering particle size analyzer (Mastersizer3000 laser particle size analyzer) can be used for measurement according to the manufacturer's instructions.

The measured results are shown in Table 1 below.

1.2 The membranes in the above-mentioned Examples A1 to A7 and Comparative Examples A1 to A4 were subjected to scanning electron microscopy (SEM) analysis after being heated at room temperature of 25°C and at 120°C for 15 minutes. Among them, the SEM photos of the membrane in Example A1 after being heated at room temperature and 120°C for 15 minutes are shown in Figures a and b in Figure 8, respectively, and the SEM photos of the membrane in Comparative Example A1 after being heated at room temperature and 130°C for 15 minutes are shown in Figures a and b in Figure 9, respectively.

Table 1

In combination with Figures 8 and 9, it can be seen from the performance data of the diaphragm in Table 1, and by comparing the air permeability of Examples A1 to A7 and Comparative Example A1 in Table 1 at room temperature and 120°C after heating for 15 minutes, it can be seen that when the ambient temperature of the diaphragm in the embodiment of the present application is lower than the melting point of the polymer particles contained in the coating, the diaphragm has good air permeability. When the ambient temperature is higher than the melting point of the polymer particles contained in the coating, the polymer particles contained in the diaphragm coating can melt and close the pores of the base film, causing the diaphragm to lose its air permeability, thereby effectively terminating the metal ion migration or positive and negative electrode crosstalk reactions in the battery, thereby improving the battery safety performance.

Comparing the uniformity of the coating slurry of Examples A2 and A6 in Table 1, it can be seen that the introduction of non-ionic groups can improve the dispersion ability of polymer particles when making coating slurry, so that the coating slurry has better uniformity and no agglomeration. Because the slurry of A6 is agglomerated, the air permeability of different positions after heating at 120°C for 15 minutes after the diaphragm is made is different. When making the battery of Example B6, it is necessary to select the position where the coating is uniform.

2. Secondary battery monomer performance test:

2.1 Hot box test of secondary battery cells

The secondary battery cells in the above-mentioned Examples B1 to B7 and Comparative Examples B1, B3, and B4 were fully charged and subjected to hot box tests at different temperatures in Table 2 for 30 minutes at 100% SOC. After the test, the negative electrode sheet was disassembled and the metal element content on the negative electrode sheet was tested using ICP. The test results of the total metal content (excluding lithium) are shown in Table 2 below.

Table 2

It can be seen from Examples B1 to B4 and Comparative Example B1 in Table 2 that the separator of the examples of the present application can effectively stop the migration of metal ions in the battery after it becomes effective.

It can be seen from Examples B1 to B4 and Comparative Example B4 in Table 2 that if the melting point of the polymer particles is too high, the diaphragm will take effect later and will not be able to terminate the metal ion migration or positive and negative electrode crosstalk reactions in the battery in time at the early stage of battery thermal runaway.

2.2 Permeability of diaphragm after secondary battery monomer injection

After the secondary battery cells in the above-mentioned Examples B1 to B7 and Comparative Examples B1 to B4 were injected and formed under the same injection and formation conditions, the batteries were disassembled to obtain various diaphragms, and the air permeability of each diaphragm was tested according to the diaphragm permeability method in Section 1.1 above. The measured results are shown in "After battery injection and high temperature (85°C) aging" in Table 1.

By comparing the air permeability of Example A4 and Comparative Example A2 after injection aging in Table 1, it can be seen that if the melting point of the polymer particles is close to the aging temperature, the diaphragm will be airtight during the normal battery manufacturing process, and the battery cannot be manufactured normally.

2.3 Secondary battery cell cycle test

The secondary battery cells in the above-mentioned Examples B1 to B7 and Comparative Example B1 were subjected to cycle tests at 25° C. and 1C/1C conditions, and the test results are shown in Table 3.

table 3

It can be seen from Examples B1 to B5 and B7 and Comparative Example B1 in Table 3 that the diaphragm of the present application can maintain good air permeability during battery production and normal use, and does not affect the charge and discharge cycle performance of the battery.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

A diaphragm, characterized in that it includes a base film and a coating arranged on at least one surface of the base film, wherein the coating contains polymer particles, and the melting point of the polymer particles is 90°C to 120°C, and can be optionally 100°C to 115°C.
The diaphragm according to claim 1, characterized in that the polymer particles satisfy at least any one of the following conditions (1) to (5):

(1) The volume distribution particle size D v 50 of the polymer particles is 0.1 μm to 5 μm, and can be 0.3 μm to 3 μm;

(2) The morphology of the polymer particles includes at least one of chain, spherical, quasi-spherical, fibrous, tubular, rod-shaped, amorphous, and pyramidal;

(3) The polymer of the polymer particles contains a nonionic group, and optionally, the nonionic group includes at least one of an ethoxy group, a hydroxyl group, and a carboxylate group;

(4) The weight average molecular weight of the polymer material of the polymer particles is 1000 to 10000, and can be optionally 1500 to 8000;

(5) The polymer includes at least one of polystyrene, polyolefin, polyimide, melamine resin, phenol resin, cellulose, polyester, polyphenylene sulfide, polyaromatic amide, polyamideimide, copolymer of butyl acrylate and ethyl methacrylate and their respective modified polymers.
The diaphragm according to any one of claims 1 to 2 is characterized in that the coating further comprises an inorganic particle filler.
The diaphragm according to claim 3, characterized in that the inorganic particle filler satisfies at least one of the following conditions:

The dry weight ratio of the inorganic particle filler to the polymer particles is (15 to 25): (25 to 35);

The volume distribution particle size D v 50 of the inorganic particle filler is 1 μm to 1.5 μm;

The inorganic particle filler includes at least one of inorganic particles having a dielectric constant of 5 or more, inorganic particles having ion conductivity but not storing ions, and inorganic particles capable of electrochemical reaction.
The diaphragm according to claim 4 is characterized in that the polymer contained in the polymer particles is low-density polyethylene, which can be non-ionic low-density polyethylene.
The diaphragm according to any one of claims 1 to 5, characterized in that the coating further comprises a binder.
The diaphragm according to claim 6, characterized in that the binder satisfies at least one of the following conditions:

The dry weight ratio of the binder to the polymer particles is (15 to 25): (25 to 35);

The binder is a water-based binder;

The thermal decomposition temperature of the binder is higher than 160°C;

The binder includes at least one of polyvinyl alcohol, polyacrylic acid-polyacrylonitrile copolymer, polyacrylate-polyacrylonitrile copolymer, polyether acrylate, polyurethane, polyacrylate, polycarbonate, polyethylene oxide, rubber, polyacrylic acid, polyacrylonitrile, gelatin, chitosan, sodium alginate, cyanoacrylate, polymerized cyclic ether derivatives, and hydroxyl derivatives of cyclodextrin.
The diaphragm according to any one of claims 1 to 7, characterized in that the coating thickness is 2 μm to 5 μm; and/or

The coating layer is disposed on one surface of the base film.
The diaphragm according to any one of claims 1 to 8, characterized in that the base film satisfies at least one of the following conditions:

The thickness of the base film is 4 μm to 7 μm;

The air permeability of the base film is 180s/100cc to 240s/100cc;

The material of the base film includes at least one of non-woven fabric, polyolefin, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene ether, polyphenylene sulfide, and polyethylene naphthalene.
A method for preparing a diaphragm, characterized in that it comprises the following steps:

providing a basement membrane;

Providing a coating slurry, wherein the coating slurry contains polymer particles, and the melting point of the polymer particles is 90° C. to 120° C., and optionally 100° C. to 115° C.;

The coating slurry is coated on at least one surface of the base film, and dried to form a coating to obtain a separator.
The preparation method according to claim 10 is characterized in that: the coating slurry is formed by mixing polymer particles, inorganic particle fillers and binders in a solvent; wherein the mass ratio of the polymer particles, inorganic particle fillers and binders in the coating slurry is (25 to 35): (15 to 25): (15 to 25); and/or

The solid content of the coating slurry is 30wt% to 40wt%; and/or

The coating slurry has a viscosity of 100 mPa·s to 1000 mPa·s at 25°C.
The preparation method according to claim 10 or 11, characterized in that when the polymer particles are polymer particles containing non-ionic groups, the polymer particles are prepared by a method comprising the following steps:

The polymer precursor particles, the ethoxy-containing polymer and the initiator are mixed and reacted to obtain polymer particles containing nonionic groups;

The polymer particles containing nonionic groups are emulsified with a nonionic surfactant to obtain a nonionic polymer emulsion.
The preparation method according to claim 12, characterized in that the polymer precursor particles, the ethoxy-containing polymer and the initiator are mixed in a mass ratio of (300 to 400): (90 to 125): (20 to 100); and/or

The material of the polymer precursor particles includes at least one of polystyrene, polyolefin, polyimide, melamine resin, phenol resin, cellulose, polyester, polyphenylene sulfide, polyaramid, polyamideimide, and copolymer of butyl acrylate and ethyl methacrylate; and/or

The ethoxy-containing polymer comprises at least one of allyl polyethylene glycol and bisallyl polyether; and/or

The initiator comprises at least one of di-tert-butyl peroxide and dicumyl peroxide; and/or

The reaction temperature is 130°C to 160°C; and/or

The polymer particles and the nonionic surfactant are emulsified in a mass ratio of (4 to 6):1.
The preparation method according to claim 12 or 13, characterized in that the nonionic polymer emulsion satisfies at least any one of the following conditions (1) to (4):

(1) The viscosity of the nonionic polymer emulsion at 25° C. is 10 mPa·s to 100 mPa·s;

(2) The solid content of the nonionic polymer emulsion is 35wt% to 40wt%;

(3) The pH value of the nonionic polymer emulsion is 5 to 6;

(4) The nonionic surfactant includes a molecular structure of
Wherein, R1 is a carbon chain alkyl group, R2 is a hydrophilic group, and n is a positive integer from 3 to 20.
The preparation method according to claim 14, characterized in that the carbon chain alkyl is a long carbon chain alkyl of C12 to C18; and/or

The R2 is at least one of a carboxyl group, an amine group, an aldehyde group, an alcohol group, an amino group, and an amide group.
The preparation method according to any one of claims 12 to 15, characterized in that the nonionic surfactant comprises at least one of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, fatty acid polyoxyethylene ester, castor oil polyoxyethylene ether, fatty amine polyoxyethylene ether, sorbitan fatty acid ester, and polyoxyethylene sorbitan fatty acid ester.
The preparation method according to any one of claims 11 to 16, characterized in that the binder is added in the form of a binder aqueous solution, and the binder aqueous solution has at least one of the following conditions:

The viscosity of the binder aqueous solution at 25° C. is 3000 mPa·s to 10000 mPa·s;

The solid content of the binder aqueous solution is 40 wt % to 50 wt %.
The preparation method according to any one of claims 10 to 17, characterized in that the coating slurry is applied at a rate of 50 m/min to 100 m/min; and/or

The drying temperature is 60°C to 70°C; and/or

The drying time is 1 min to 3 min.
A battery, characterized in that it comprises a positive electrode, a negative electrode and a separator stacked between the positive electrode and the negative electrode, wherein the separator is the separator according to any one of claims 1 to 9 or the separator prepared by the preparation method according to any one of claims 10 to 18.
The battery according to claim 19, characterized in that the coating is provided on one surface of the separator, and the coating faces the negative electrode.
An electrical device, characterized in that the electrical device comprises a battery as described in claim 19 or 20, and the battery is used to provide electrical energy.