Composite diaphragm, preparation method thereof, battery and electric device

Abstract

The invention discloses a composite diaphragm and a preparation method thereof, a battery and an electric device. The composite diaphragm comprises a base membrane, the base membrane is provided with a first surface and a second surface which are oppositely arranged, the first surface of the base membrane is provided with a non-woven fabric layer, the non-woven fabric layer comprises a non-woven fabric material formed by polymer fibers, and the porosity of the non-woven fabric layer is at least 40%; the composite diaphragm is used in a battery, and the non-woven fabric layer is adjacent to a negative pole piece of the battery. The non-woven fabric formed by the base membrane and the organic polymer fibers is compounded to form the composite diaphragm, and when the composite diaphragm is used in the battery, the non-woven fabric layer is close to one side of the negative pole piece, so that the cycle stability, the cycle life and the safety of the battery are improved on the basis of the characteristics of the non-woven fabric layer in the composite diaphragm.

Description

Technical Field

[0001] This application belongs to the technical field of battery materials, and particularly relates to a composite separator, a preparation method thereof, a battery, and an electrical device. Background Art

[0002] A battery separator film (BSF), also known as a battery separator, is one of the core materials in a battery. The separator is located between the positive electrode plate and the negative electrode plate of the battery. Its main function is to separate the positive active material and the negative active material of the battery to reduce the risk of short circuit due to contact between the two electrode plates. At the same time, it allows carrier ions to pass through to form a charge and discharge circuit, and it has an important impact on the safety and cost of the battery.

[0003] During the charge and discharge process of a secondary battery, there is a risk of dendrites on the negative electrode. For example, the dendrite growth of a metal negative electrode is likely to pierce the separator, thereby affecting the performance and life of the battery. Summary of the Invention

[0004] In view of the above problems, this application provides a composite separator, a preparation method thereof, a battery, and an electrical device, aiming to solve the technical problem of the risk of dendrite growth on the negative electrode of the battery.

[0005] In a first aspect, an embodiment of this application provides a composite separator, including a base film. The base film has a first surface and a second surface that are oppositely arranged. A non-woven fabric layer is provided on the first surface of the base film. The non-woven fabric layer includes a non-woven fabric material formed by organic polymer fibers, and the porosity of the non-woven fabric layer is at least 40%; the composite separator is used in a battery, and the non-woven fabric layer is adjacent to the negative electrode plate of the battery.

[0006] By compounding the base film and the non-woven fabric formed by organic polymer fibers to form a composite separator, when the composite separator is used in a battery, the non-woven fabric layer is on the side close to the negative electrode plate. In this way, when dendrite growth occurs on the negative electrode plate, the non-woven fabric based on organic polymer fibers has a three-dimensional network fiber structure, which can provide a certain pre-growth space for the dendrite growth on the negative electrode plate. At the same time, the three-dimensional network fiber structure of the non-woven fabric can disperse the metal deposition growth stress on the negative electrode plate in all directions, thereby changing the state of perpendicular growth of the dendrite from the surface of the negative electrode plate, that is, by controlling the metal deposition behavior, a uniform and dense deposition layer is formed on the surface of the negative electrode plate, so that the risk of the composite separator being pierced by continuous dendrite growth can be significantly reduced. In addition, the non-woven fabric material of the organic polymer fibers itself not only has good stability and is not prone to thermal runaway, but also has good air permeability and large pores, which is beneficial to the infiltration of the electrolyte and promotes ion transport. Therefore, the composite separator of the embodiment of this application is beneficial to improving the cycle stability, cycle life, and safety of the battery when used in the battery.

[0007] In some embodiments, the porosity of the non-woven fabric layer is 47% - 70%.

[0008] The non-woven fabric layer with a porosity of 47% to 70% can provide sufficient pre-growth space for dendritic growth, and at the same time can reduce the barrier for ions to pass through the non-woven fabric, thereby promoting ion transport.

[0009] In some embodiments, the thickness of the non-woven fabric layer is 10 μm to 35 μm; and / or,

[0010] the thickness of the base film is 5 μm to 20 μm.

[0011] By selecting the thickness of the non-woven fabric layer and the base film, the composite separator formed by laminating the non-woven fabric layer and the base film can have good mechanical properties, and at the same time can reduce the risk of dendritic growth on the negative electrode of the battery.

[0012] In some embodiments, the organic polymer fibers include at least one of viscose fiber, acetate fiber, polyester fiber, polypropylene fiber, and polyimide fiber; and / or,

[0013] the material of the base film includes polyolefin.

[0014] The composite separator formed by the above-mentioned organic polymer fibers and polyolefin is used in the battery. The side of the non-woven fabric layer close to the negative electrode can improve the cycle stability, cycle life and safety of the battery.

[0015] In some embodiments, a first coating is provided between the first surface of the base film and the non-woven fabric layer and / or a second coating is provided on the second surface of the base film. The first coating and the second coating independently include at least one of organic nanomaterials, inorganic nanomaterials, and organic-inorganic composite nanomaterials.

[0016] Coating a coating containing nanomaterials on one or both sides of the base film can enhance the overall mechanical strength of the composite separator. Therefore, based on the increase in the mechanical properties of the composite separator, the risk of dendrites growing through the composite separator can be reduced, and at the same time, the electrolyte wettability can be improved. Further, especially the first coating between the base film and the non-woven fabric layer can also increase the bonding stability between the base film and the non-woven fabric layer. At the same time, the nanomaterial structure of the first coating can provide secondary protection against dendrites, and in combination with the non-woven fabric layer, it can further change the deposition morphology of dendrites, enabling the metal to deposit uniformly at the interface, and further significantly reducing the risk of internal short circuit in the battery.

[0017] In some embodiments, the materials of the first coating and the second coating have one or more of the following (1) to (3):

[0018] (1) The organic nanomaterials include at least one of aromatic ring polymers, heteroaromatic ring polymers, aramid fibers, and polyurethane fibers;

[0019] (2) The inorganic nanomaterials include at least one of tin dioxide nanoparticles, silicon dioxide nanoparticles, and silver nanoparticles;

[0020] (3) The organic-inorganic composite nanomaterials include at least one of silicon-polyacrylic acid composite materials, silicon-polyacrylonitrile composite materials, tin-polyacrylic acid composite materials, and tin-polyacrylonitrile composite materials.

[0021] On the basis that the first coating and the second coating enhance the mechanical strength of the composite separator and reduce the risk of dendrite growth piercing the composite separator, by further selecting the types of organic nanomaterials, inorganic nanomaterials, and organic-inorganic composite nanomaterials in the coating, the coating can better modify the base film.

[0022] In some embodiments, the first coating is provided on the first surface of the base film, the second coating is provided on the second surface of the base film, the first coating includes the organic nanomaterials, and the second coating includes the inorganic nanomaterials.

[0023] A first coating containing organic nanomaterials is provided on the first surface of the base film close to the non-woven fabric layer, and a second coating containing inorganic nanomaterials is provided on the second surface of the base film far from the non-woven fabric layer. On the one hand, due to the good adhesion of the organic nanomaterials, the non-woven fabric layer can be more stably bonded to the base film and is not easily detached. On the other hand, due to the good hardness and wear resistance of the inorganic nanomaterials, the mechanical strength of the composite separator can be better. Therefore, through the combination of the above first coating and second coating, the composite separator has both a stable ability to prevent dendrite piercing risk.

[0024] In some embodiments, the pore size of the first coating is 0.2 - 2 μm; and / or

[0025] The pore size of the second coating is 0.2 - 2 μm.

[0026] By selecting the pore sizes of the first coating and the second coating, the composite separator can have good electrolyte wettability and at the same time improve the ion transport efficiency.

[0027] In some embodiments, the porosity of the base film and the whole of the first coating and the second coating is 28% - 46%; and / or,

[0028] The thickness of the base film and the whole of the first coating and the second coating is 7 μm - 25 μm.

[0029] The coating is combined on the surface of the base film to form a whole. By regulating the porosity and thickness of the whole of the base film and the coating, the composite separator has good mechanical properties and is beneficial to ion transport.

[0030] In some embodiments, the composite separator has one or more of the following (1) to (5):

[0031] (1) The porosity of the composite separator is 38% to 55%;

[0032] (2) The Young's modulus of the composite separator in the length direction is 8 MPa to 15 MPa;

[0033] (3) The Young's modulus of the composite separator in the width direction is 6 MPa to 15 MPa;

[0034] (4) The thickness of the composite separator is 15 μm to 55 μm;

[0035] (5) The air permeability of the composite separator is 260 s / 100CC to 390 s / 100CC.

[0036] By selecting the porosity, Young's modulus, air permeability and thickness of the whole composite separator, the composite separator can be better used in the battery to improve the cycle stability, cycle life and safety of the battery.

[0037] In a second aspect, an embodiment of the present application provides a method for preparing the above composite separator, including the following steps:

[0038] Bond the first surface of the base film with the non-woven fabric layer to obtain the composite separator.

[0039] In the present application, the composite separator is obtained by bonding the base film and the non-woven fabric. Not only is the process simple, but the prepared composite separator has good stability, is beneficial to ion transport. When used in the battery, the non-woven fabric layer close to the negative electrode can significantly reduce the risk of the dendrites on the negative electrode continuously growing and piercing the composite separator. Therefore, the composite separator prepared in this way can improve the cycle stability, cycle life and safety of the battery.

[0040] In some embodiments, before bonding the first surface of the base film with the non-woven fabric layer, it further includes: coating a first slurry containing at least one of organic nanomaterials, inorganic nanomaterials and organic-inorganic composite nanomaterials on the first surface of the base film to obtain a first coating; and / or,

[0041] Before or after bonding the first surface of the base film with the non-woven fabric layer, it further includes: coating a second slurry containing at least one of organic nanomaterials, inorganic nanomaterials and organic-inorganic composite nanomaterials on the second surface of the base film to obtain a second coating.

[0042] By preparing coatings on at least one surface of the base film, the mechanical strength of the composite separator can be enhanced, and the risk of dendrites growing and piercing the composite separator can be further reduced.

[0043] In a third aspect, an embodiment of the present application provides a battery, including a positive electrode plate, a negative electrode plate, and a separator disposed between the positive electrode plate and the negative electrode plate. The separator includes the composite separator provided in the first aspect of the embodiment of the present application and / or the composite separator prepared by the preparation method provided in the second aspect of the embodiment of the present application, and the non-woven fabric layer in the composite separator is located between the base film and the negative electrode plate.

[0044] By using the composite separator provided in the first aspect of the embodiment of the present application and / or the composite separator prepared by the preparation method provided in the second aspect of the embodiment of the present application in the battery, based on the good stability of the composite separator, favorable for ion transport, and significantly reducing the risk of the dendrites on the negative electrode plate continuously growing and piercing the composite separator, the battery can have good cycle stability, cycle life, and safety.

[0045] In some embodiments, the negative electrode plate is a plate without negative electrode active material.

[0046] The battery corresponding to the plate without negative electrode active material is the so-called non-aqueous metal battery, in which metal deposition occurs on the negative electrode current collector. Due to the high reactivity of the metal, it is easy to deposit unevenly, resulting in too large local current density and promoting dendrite growth. However, based on the composite separator of the embodiment of the present application, the risk of the dendrites growing on the surface of the plate without negative electrode active material piercing can be well prevented. Therefore, such a battery has the characteristics of high energy density, good cycle performance, and long service life.

[0047] In some embodiments, the battery includes at least two electrode assemblies, and there is no buffer pad between adjacent electrode assemblies.

[0048] In the initial stage of charge and discharge of the battery, due to metal deposition, it is easy to cause extrusion of the electrode assemblies. Therefore, a buffer pad with compressibility is generally required to prevent short circuit inside the battery caused by the extrusion of adjacent electrode assemblies. However, based on the addition of non-woven fabric in the composite separator of the embodiment of the present application, which has a certain stress buffering effect, the buffer pad can be not set and still have good safety performance, thus further reducing the battery cost.

[0049] In a fourth aspect, an embodiment of the present application provides an electrical device, including the battery provided in the third aspect of the present application.

[0050] By adopting the battery provided in the third aspect of the embodiment of the present application, such an electrical device has good cycle performance and service life and can work for a longer time.

[0051] The above description is only an overview of the technical solution of the present application. In order to better understand the technical means of the present application, it can be implemented according to the content of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and understandable, the following specific embodiments of the present application are given. Description of the Drawings

[0052] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of illustrating the preferred embodiments and are not considered to be a limitation of the present application. Moreover, in all the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0053] Figure 1 is a schematic structural diagram of a composite diaphragm according to an embodiment of the present application;

[0054] Figure 2 is a schematic structural diagram of a composite diaphragm according to another embodiment of the present application;

[0055] Figure 3 is a schematic structural diagram of a composite diaphragm according to yet another embodiment of the present application;

[0056] Figure 4 is a schematic structural diagram of a composite diaphragm according to still another embodiment of the present application;

[0057] Figure 5 is an SEM image of a composite diaphragm prepared according to an embodiment of the present application;

[0058] Figure 6 is a schematic structural diagram of an embodiment of a secondary battery according to an embodiment of the present application;

[0059] Figure 7 is Figure 6 a disassembled schematic diagram of the secondary battery shown;

[0060] Figure 8 is a schematic structural diagram of an embodiment of a battery module according to an embodiment of the present application;

[0061] Figure 9 is a schematic structural diagram of an embodiment of a battery pack according to an embodiment of the present application;

[0062] Figure 10 is Figure 9 a disassembled structural diagram of the battery pack shown;

[0063] Figure 11 is a schematic diagram of an embodiment of an electrical device including the battery according to an embodiment of the present application as a power source.

[0064] Description of the Reference Numerals:

[0065] 11 - Base film; 12 - Non - woven fabric layer; 13 - First coating; 14 - Second coating;

[0066] 20 - Battery cell; 21 - Housing; 22 - Top cover assembly; 23 - Electrode assembly; 30 - Battery module; 40 - Battery pack; 41 - Upper box body; 42 - Lower box body. Detailed implementation manners

[0067] The embodiments of the technical solutions of the present application will be described in detail below with reference to the accompanying drawings. The following embodiments are only used to illustrate the technical solutions of the present application more clearly, so they are only examples and cannot be used to limit the protection scope of the present application.

[0068] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill 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" and any variations thereof in the specification and claims of this application and the above - mentioned drawings are intended to cover non - exclusive inclusion.

[0069] In the description of the embodiments of this application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order or primary - secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "a plurality" is more than two, unless otherwise specifically defined.

[0070] Referring to "embodiments" herein means that the specific features, structures or characteristics described in connection with the embodiments can be included in at least one embodiment of this application. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0071] In the description of the embodiments of this application, the term "and / or" is only a description of the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this article generally represents an "or" relationship between the associated objects before and after.

[0072] In the description of the embodiments of this application, the term "a plurality" 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). "At least one kind" refers to more than one kind (including one kind, two kinds, three kinds, etc.).

[0073] In the description of the embodiments of the present application, the orientation or positional relationship indicated by technical terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the embodiments of the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the embodiments of the present application.

[0074] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installation", "connection", "connection", "fixation", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can also be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside 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 specific circumstances.

[0075] In the context of the era of energy conservation and emission reduction, new energy technologies have developed rapidly, among which the research breakthroughs and applications of battery technologies are the most remarkable. The separator is one of the core materials in the battery. The separator is located between the positive electrode plate and the negative electrode plate of the battery. Its main function is to separate the positive active material and the negative active material of the battery to reduce the risk of short circuit due to contact between the two electrode plates, and at the same time allow the passage of carrier ions to form a charge and discharge circuit, which has an important impact on the safety and cost of the battery.

[0076] A secondary battery (Rechargeable battery), also known as a rechargeable battery, refers to a battery that can activate the active material by charging after discharging. During the charge and discharge process of a secondary battery, there is a risk of dendrite growth at the negative electrode. For example, in a metal battery (also known as a non-negative electrode metal battery), metal deposition occurs on the metal sheet acting as the negative electrode. Due to the high reactivity of the metal, it is easy to deposit unevenly, resulting in an excessive local current density. Therefore, the "tip effect" promotes the growth of dendrites. If the dendrite growth is allowed to continue, the dendrites will eventually pierce the separator and cause a short circuit, rendering the battery ineffective. Therefore, it is necessary to improve the dendrite growth state to reduce or even eliminate the risks brought by dendrite growth.

[0077] The structure of the separator base film materials commonly used in current batteries on the market is single. For example, polyolefin-based films such as commonly used polymer substrates like polyethylene (PE) and polypropylene (PP) are affected by the synthesis process, and their structures show single transverse or longitudinal stretching. Such base films are prone to short circuits when used in metal batteries, so generally their surfaces need to be coated and modified. Although non-woven fabrics have a three-dimensional network structure, due to the large porosity of non-woven fabrics, a single organic non-woven fabric material cannot effectively prevent dendrite piercing as a separator, so it is difficult to be used alone in metal batteries and generally needs to be modified with inorganic fillers. Based on the fact that a single separator base film material is prone to short circuits in batteries and a single organic non-woven fabric material is also prone to short circuits, and the material processes of the two are different and generally modified by coatings, it is difficult for people to think of compounding the base film material with the organic non-woven fabric material into a composite separator.

[0078] Currently, there is a method of modifying the separator by coating and modification. For example, a coating modification layer is coated on the surface of the above-mentioned commonly used separator base film or commonly used non-woven fabric as a composite separator. Although it can enhance the mechanical properties of the composite separator, its ability to change or control the dendrite growth state is limited, and generally the modified coating is relatively thick, which instead reduces the energy density of the battery.

[0079] Based on the above considerations, in order to reduce the risk brought by dendrite growth, the embodiments of this application design a composite separator, that is, the current base film and organic non-woven fabric are laminated and compounded to form a composite separator. When in use, the non-woven fabric layer of the composite separator is close to the negative electrode plate side of the battery. In this way, when dendrite growth occurs on the negative electrode plate, based on the physical and chemical properties of the non-woven fabric, the composite separator formed by compounding with the base film can significantly reduce the risk brought by the continuous growth of dendrites. Thus, the following technical solutions are proposed.

[0080] Composite Separator and Its Preparation Method

[0081] In the first aspect, the embodiments of this application provide a composite separator. As some embodiments of this application are summarized, as Figures 1 - 4 shown, the composite separator includes a base film 11 and a non-woven fabric layer 12: the base film 11 has a first surface and a second surface arranged oppositely, and the non-woven fabric layer 12 is arranged on the first surface of the base film 11 and combined with the base film 11. When the composite separator of the embodiments of this application is used in a battery, the non-woven fabric layer 12 on the first surface of the base film 11 is close to the negative electrode plate side.

[0082] The base film 11 refers to the base film made of the separator substrate, which is a porous film formed by the polymer substrate. The base film made of the polymer substrate with a porous structure can meet the mechanical properties required by the battery separator and the function of allowing ions to pass through.

[0083] The non-woven fabric layer 12 is a non-woven fabric material formed by organic polymer fibers. The non-woven fabric is also known as non-woven cloth or needle-punched cotton, and is generally made through a needle-punching process. On the one hand, the non-woven fabric has a three-dimensional network fiber structure, with large pores and good air permeability, and has good wettability to the electrolyte. When it is compounded with the base film 11, it will not affect the ion transport efficiency between the positive and negative electrode plates of the battery. On the other hand, the non-woven fabric has good thermal stability and mechanical stability, and is not prone to high-temperature failure. At the same time, the porosity of the non-woven fabric layer 12 is at least 40%. The non-woven fabric can provide space for metal deposition during initial charging and change the growth direction of dendrites through steric hindrance, thereby reducing the risk of dendrite growth on the negative electrode plate.

[0084] Based on this, in the embodiment of the present application, a composite separator is formed by compounding the base film 11 and the non-woven fabric layer 12 of organic polymer fibers. When used in a battery, the non-woven fabric layer 12 is on the side close to the negative electrode plate of the battery. When dendrite growth occurs on the negative electrode plate, due to the three-dimensional network fiber structure of the non-woven fabric layer 12 with a certain porosity, it provides a "pre-growth" space for dendrites. After nucleation and deposition on the electrode plate of the negative electrode plate, the dendrites gradually grow away from the electrode plate substrate and enter the three-dimensional network framework of the non-woven fabric. The initial growth stress of the metal is relatively large, and the non-woven fabric provides a "pre-growth" space for the metal. At the same time, the base film of the composite separator has certain mechanical properties, so that the composite separator can allow dendrites to grow while avoiding the risk that the continuous growth of dendrites may cause the dendrite tip to pierce the separator. Moreover, the mesh pores of the non-woven fabric change the vertical growth state of the dendrites, control the metal deposition behavior, disperse the growth stress in all directions, shape the deposition morphology, and finally form a blocky, uniform and dense deposition layer. At the same time, due to the good stability of the organic non-woven fabric material itself, it is beneficial to the infiltration and ion transport of the electrolyte. Therefore, the composite separator in the embodiment of the present application is beneficial to improving the cycle stability, cycle life and safety of the battery when used in the battery.

[0085] In some embodiments, the porosity of the non-woven fabric layer 12 is 47% to 70%. Exemplarily, it can be 48%, 50%, 55%, 58%, 60%, 62%, 67%, 68%, 70%, etc. Porosity refers to the percentage of the pore volume in a porous material to the total volume of the material in its natural state. The ratio of the total volume of the interconnected tiny voids in a porous material to the outer surface volume of the porous material is called the effective porosity. The ratio of the total volume of all the interconnected and non-interconnected tiny voids in a porous material to the outer surface volume of the porous medium is called the absolute porosity or total porosity. The embodiments of the present application may refer to the effective porosity. The measurement of porosity can refer to the national standard "GB / T 24586-2009". If the porosity of the non-woven fabric layer 12 is too small, it will increase the barrier for ions to pass through the non-woven fabric, thus increasing the difficulty of ion transport. If the porosity is too large, it will reduce the "anchoring" effect of the network structure of the non-woven fabric layer 12 on the deposited metal and it is difficult to provide sufficient metal "pre-growth" space. The non-woven fabric layer 12 with a porosity of 40% to 70% can provide sufficient pre-growth space for dendrite growth on the negative electrode plate, and at the same time can better reduce the barrier for ions to pass through the non-woven fabric, thereby promoting ion transport. Specifically, the porosity of the non-woven fabric layer 12 can be 48% to 56%.

[0086] In some embodiments, the thickness of the non-woven fabric layer 12 is 10 μm to 35 μm. Exemplarily, it can be 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 22 μm, 15 μm, 28 μm, 30 μm, 32 μm, 35 μm, etc. If the thickness of the non-woven fabric layer 12 is too large, it will increase the barrier for ions to pass through the non-woven fabric, thus increasing the degree of difficulty of ion transport. If the thickness is too small, it will reduce the "anchoring" effect of the network structure of the non-woven fabric layer 12 on the deposited metal and it is difficult to provide sufficient metal "pre-growth" space. The non-woven fabric layer 12 with a thickness of 10 μm to 35 μm can provide sufficient pre-growth space for dendrite growth on the negative electrode plate, and at the same time can better reduce the barrier for ions to pass through the non-woven fabric, thereby promoting ion transport. Specifically, the thickness of the non-woven fabric layer 12 can be 15 μm to 18 μm.

[0087] In some embodiments, the air permeability of the non-woven fabric layer 12 is 5 s / 100 CC to 16 s / 100 CC. Exemplarily, it can be 5 s / 100 CC, 8 s / 100 CC, 10 s / 100 CC, 12 s / 100 CC, 14 s / 100 CC, 16 s / 100 CC, etc. The air permeability refers to the degree to which an object or medium allows gas to pass through under certain conditions. In the embodiments of the present application, the measurement of the air permeability refers to the international standard "GB / T458 - 2008". The non-woven fabric layer 12 that meets the above air permeability can well achieve the reduction of the risk of the dendrite continuous growth piercing the composite separator in the embodiments of the present application. Specifically, the air permeability of the non-woven fabric layer 12 can be 6 s / 100 CC to 10 s / 100 CC.

[0088] In some embodiments, the non-woven fabric material of the non-woven fabric layer 12 is an organic polymer fiber, which includes at least one of viscose fiber, acetate fiber, polyester fiber, polypropylene fiber, and polyimide fiber. The above non-woven fabric materials can well form the non-woven fabric layer 12 required in the embodiments of the present application. Specifically, the non-woven fabric material of the non-woven fabric layer 12 includes polyester fiber. Polyester fiber not only has excellent mechanical properties, thermal stability, and electrical insulation, which promotes the efficient and stable migration of ions, but also the R-COO-R group in the polyester fiber has higher compatibility with the electrolyte, further improving the liquid retention ability. Exemplarily, the polyester fiber can be polyethylene terephthalate.

[0089] In some embodiments, the non-woven fabric material of the non-woven fabric layer 12 is polyester fiber, and the porosity of the non-woven fabric layer 12 is 48 - 56%, the air permeability is 6 s / 100 CC to 10 s / 100 CC, and the thickness is 15 μm to 18 μm. The composite separator formed under this condition has better comprehensive effects.

[0090] In some embodiments, a coating containing nano-materials is provided on the surface of the base film 11. Specifically, as Figure 2 shown, a first coating 13 is provided on the first surface of the base film 11 close to the non-woven fabric layer 12. Or, as Figure 3 shown, a second coating 14 is provided on the second surface of the base film 11 away from the non-woven fabric layer 12. Or, as Figure 4 shown, a first coating 13 is provided on the first surface of the base film 11 close to the non-woven fabric layer 12, and a second coating 14 is provided on the second surface of the base film 11 away from the non-woven fabric layer 12. By coating a coating containing nano-materials on one or both sides of the base film 11, the overall mechanical strength of the composite separator can be enhanced, thereby increasing the mechanical properties of the composite separator and further reducing the risk of dendrite growth piercing the composite separator. At the same time, the first coating 13 and the second coating 14 are coatings containing nano-materials and have certain pores, so it is beneficial to improve the electrolyte wettability.

[0091] Among them, the first coating 13 includes at least one of organic nanomaterials, inorganic nanomaterials, and organic-inorganic composite nanomaterials, and the second coating 14 includes at least one of organic nanomaterials, inorganic nanomaterials, and organic-inorganic composite nanomaterials. By selecting the types of organic nanomaterials, inorganic nanomaterials, and organic-inorganic composite nanomaterials in the coating, the coating can better modify the base film 11.

[0092] Taking the first coating 13 as an example, the first coating 13 between the base film 11 and the non-woven fabric layer 12 can increase the bonding stability between the base film 11 and the non-woven fabric layer 12. At the same time, the nanomaterial structure of the first coating 13 can play a secondary protection role against dendrites. Combining with the non-woven fabric layer 12 can further change the deposition morphology of dendrites, which is beneficial for the first coating 13 to construct a suitable SEI layer to inhibit dendrite growth or eliminate dendrites, form a uniform deposition interface, further prevent dendrites from piercing the composite separator, and significantly reduce the risk of internal short circuit of the battery.

[0093] In some embodiments, the organic nanomaterials include at least one of aromatic ring polymers, heteroaromatic ring polymers, aramid fibers, and polyurethane fibers. Exemplarily, the aromatic ring polymer may include at least one of polyethylene terephthalate or polybutylene terephthalate. The heteroaromatic ring polymer may include at least one of polyaniline, polyimide, polybenzophenone tetracarboximide, or biphenyltetracarboxylic dianhydride. The aramid fibers may include at least one of polyphenylene sulfide fibers, polyether ketone ketone fibers, or poly(p-phenylene terephthalamide) fibers. The polyurethane fibers may include polyurethane. Specifically, the organic nanomaterials include aramid fibers, which have good heat resistance and adhesiveness, improve the stability and strength of the composite separator, enhance the liquid absorption capacity of the composite separator, improve the wettability and conductivity, and the combination of its nanoporous structure and the non-woven fabric layer 12 can better play a secondary protection role against dendrites and improve the "shuttle effect" of metals.

[0094] In some embodiments, the inorganic nanomaterials include at least one of tin dioxide nanoparticles, silica nanoparticles, and silver nanoparticles. Specifically, the inorganic nanomaterials include silica nanoparticles; silica not only has good thermal stability, but also can increase the wettability and liquid retention of the separator. At the same time, it forms an interconnected surface structure with the base film 11, which can make the base film 11 and the coating more stable, thereby better improving the overall mechanical properties of the composite separator. In addition, the inorganic nanomaterials can react with metals to form alloys, such as reacting with Na metal to form Na x Sn y / Na x Si y , which can effectively distribute the ion flux, enhance the electrolyte wettability, and make the sodium ions uniformly distributed and nucleated.

[0095] In some embodiments, the organic-inorganic composite nanomaterials include at least one of silicon-polyacrylic acid (Si-PAA) composite materials, silicon-polyacrylonitrile (Si-PAN) composite materials, tin-polyacrylic acid (Sn-PAA) composite materials, and tin-polyacrylonitrile (Sn-PAN) composite materials. The above-mentioned types of organic-inorganic composite nanomaterials can also react with metals to form ion conductors. For example, reacting with Na metal forms Na x Sn y / Na x Si y and NaPAA / NaPAN ion conductors, which can effectively distribute the ion flux, enhance the electrolyte wettability, and make the sodium ions uniformly distributed and nucleated. Specifically, the organic-inorganic composite nanomaterials include tin-polyacrylonitrile composite materials. Sn has strong reactivity with Na metal, and at the same time, PAN can better enhance the wettability of the electrolyte.

[0096] Among them, the materials and related parameters of the first coating 13 and the second coating 14 can be the same or different.

[0097] In some embodiments, a first coating 13 is disposed on the first surface of the base film 11 close to the non-woven fabric layer 12, and a second coating 14 is disposed on the second surface of the base film 11 away from the non-woven fabric layer 12. The first coating 13 includes the above-mentioned organic nanomaterials, and the second coating 14 includes the above-mentioned inorganic nanomaterials or organic-inorganic composite nanomaterials. On the one hand, based on the good adhesiveness of the organic nanomaterials in the first coating 13, the non-woven fabric layer 12 can be more stably bonded to the base film 11 and is not easily detached. Moreover, the strength of the cross-linked structure and the nano-pore size of the organic nanomaterials can block the dendrite growth and more easily change the original vertically growing state of the dendrites to a horizontally growing state. On the other hand, based on the good hardness and wear resistance of the inorganic nanomaterials in the second coating 14, the mechanical strength of the composite separator can be better. At the same time, the inorganic nanomaterials or organic-inorganic composite nanomaterials react with metals such as sodium or potassium to play the role of "eating sodium" and "eating potassium", effectively distributing the ion flux. Therefore, through the combination of the above-mentioned first coating 13 and second coating 14, the composite separator has both a stable ability to prevent dendrite piercing risks.

[0098] In some embodiments, the pore size of the first coating 13 is 0.2 - 2 μm. In another embodiment, the pore size of the second coating 14 is 0.2 - 2 μm. The pore size of the coating refers to the size of the pores formed by the interlacing of the material fibers or particles in the coating, which can also be called the pore throat. Exemplarily, the pore size of the first coating 13 can be 0.2 μm, 0.4 μm, 0.6 μm, 0.8 μm, 1 μm, 1.2 μm, 1.4 μm, 1.8 μm, 2.0 μm; the pore size of the second coating 14 can be 0.2 μm, 0.4 μm, 0.6 μm, 0.8 μm, 1 μm, 1.2 μm, 1.4 μm, 1.8 μm, 2.0 μm.

[0099] The first coating 13 and the second coating 14 are nano - material coatings. After the nano - materials form the coatings, pores, that is, the gaps of the pores, exist on the surface, which can also be called the pore throat. By selecting the pore sizes of the first coating 13 and the second coating 14, the composite separator can have good electrolyte wettability and at the same time improve the ion transport efficiency. Specifically, the pore size of the first coating is 0.2 - 1 μm, and the pore size of the second coating is 0.2 - 1 μm.

[0100] In some embodiments, the material of the base film 11 includes polyolefin, such as one or several of PE, PP, and PP / PE / PP multi - layer microporous separators. The thickness of the base film 11 can be 5 - 20 μm. The thickness of each of the first coating 13 and the second coating 14 can be 1 - 2 μm, and the overall thickness of the base film 11, the first coating 13, and the second coating 14 is 7 μm - 25 μm, for example, 7 μm - 16 μm.

[0101] In some embodiments, taking the base film 11, the first coating 13, and the second coating 14 as a whole, the porosity is 28% - 46%. When there is a coating on only one surface of the base film, that is, the overall porosity of the base film and the coating on one surface is 28% - 46%. When there are coatings on both surfaces of the base film, that is, the overall porosity of the base film and the coatings on two opposite surfaces is 28% - 46%. Exemplarily, it can be 28%, 30%, 34%, 38%, 40%, 42%, 45%, etc. The base film 11 modified under this condition has good mechanical properties and is also conducive to ion transport.

[0102] In some embodiments, for the whole of the base film 11, the first coating 13, and the second coating 14, the air permeability is 245 s / 100CC - 270 s / 100CC. Exemplarily, it can be 245 s / 100CC, 8 s / 100CC, 250 s / 100CC, 257 s / 100CC, 260 s / 100CC, 265 s / 100CC, 270 s / 100CC, etc. The base film 11 modified under this condition meets the requirements of the composite separator in the battery.

[0103] In some embodiments, the base film 11, the first coating 13 and the second coating 14 as a whole have a porosity of 35% to 40%, an air permeability of 255 s / 100CC to 260 s / 100CC, and a thickness of 15 μm to 16 μm. The coating is combined on the surface of the base film 11 to form a whole. By regulating the porosity, air permeability and thickness of the base film 11 and the coating as a whole, the composite separator formed with the non-woven fabric laminated thereto has good mechanical properties and is also conducive to ion transport.

[0104] In some embodiments, the porosity of the base film 11, the first coating 13 and the second coating 14 as a whole is less than that of the non-woven fabric layer 12. For example, the porosity of the base film 11, the first coating 13 and the second coating 14 as a whole is 32% to 46%, and the porosity of the non-woven fabric layer 12 is 48% to 56%. The non-woven fabric layer 13 is closer to the negative electrode side of the battery and has a larger porosity, providing a larger space for the initial massive metal. The porosity of the base film closer to the positive electrode side of the battery is smaller, which can regulate the state and direction of the growth of tip dendrites. Since the tip dendrites are softer, the dense network structure is more likely to disperse the stress of the vertical growth of the crystal branches, so that the dendrites grow in the horizontal direction.

[0105] In the embodiments of the present application, by regulating the material types, porosity and thickness of the non-woven fabric layer 12 and the coating (including the first coating 13 and / or the second coating 14), the growth state of dendrites in the metal battery can be improved, the risk of battery short circuit caused by dendrite tips can be reduced, and excellent cycle stability, cycle life and safety can be achieved.

[0106] In some embodiments, the porosity of the composite separator is 38% to 55%. Exemplarily, it can be 38%, 40%, 42%, 45%, 48%, 50%, 55%, etc. The composite separator with the above porosity is very conducive to ion transport.

[0107] In some embodiments, the Young's modulus in the length direction of the composite separator is 8 MPa to 15 MPa. For example, it can be 8 MPa, 10 MPa, 12 MPa, 15 MPa, etc.; the Young's modulus in the width direction of the composite separator is 6 MPa to 15 MP. For example, it can be 6 MPa, 8 MPa, 10 MPa, 12 MPa, 15 MPa, etc. The Young's modulus is a physical quantity that describes the ability of a solid material to resist deformation. The Young's modulus is also called the tensile modulus and is the most common type of elastic modulus. The test method for the Young's modulus of the composite separator in the embodiments of the present application refers to the national standard "GB / T7757-2009". The composite separator formed by the above Young's modulus parameters shows that it has good mechanical properties and can be well used in batteries.

[0108] In some embodiments, the thickness of the composite separator is 15 μm to 55 μm, for example, it can be 15 μm, 18 μm, 20 μm, 22 μm, 24 μm, 25 μm, 28 μm, 30 μm, 32 μm, 34 μm, 35 μm, 38 μm, 40 μm, 42 μm, 45 μm, 48 μm, 50 μm, 52 μm, 55 μm, etc. The total thickness of the composite separator is formed by the thickness of the base film 11 (or combined coatings, such as the first coating 13 and / or the second coating 14) and the non-woven fabric layer 12, which has little impact on the energy density of the battery, and at the same time can significantly reduce the risk brought by the continuous growth of dendrites on the negative electrode sheet.

[0109] In some embodiments, the porosity of the composite separator is 40% to 45%, the Young's modulus in the length direction is 9.5 MPa to 14 MPa, the Young's modulus in the width direction is 7.5 MPa to 14 MPa, and the total thickness is 25 μm to 34 μm. Specifically, the total air permeability of the composite separator can be 260 s / 100CC to 390 s / 100CC.

[0110] In some embodiments, according to the needs of the battery, on the basis of setting the non-woven fabric layer on the first surface of the base film, the same or different non-woven fabric layers can also be set on the second surface of the base film, and the specific material, thickness, and porosity selection of the non-woven fabric layer on the second surface can refer to the non-woven fabric layer on the first surface. When there is no second coating on the second surface of the base film, the non-woven fabric layer is directly added to the second surface of the base film. When there is a second coating on the second surface of the base film, the non-woven fabric layer is added on the second coating. The situation of setting the non-woven fabric layer on the second surface of the base film is also within the protection scope of the technical solution of the present application.

[0111] In the second aspect, the embodiments of the present application provide a preparation method of the above composite separator, including the following steps:

[0112] The first surface of the base film 11 is bonded to the non-woven fabric layer 12 to obtain a composite separator.

[0113] In the embodiments of the present application, the composite separator is obtained by bonding the base film 11 and the non-woven fabric layer 12. Not only is the process simple, but the prepared composite separator has good stability, is beneficial to ion transport, and using the non-woven fabric layer close to the negative electrode sheet side in the battery can significantly reduce the risk that the dendrites on the negative electrode sheet continuously grow and pierce the composite separator. Therefore, the composite separator prepared in this way can improve the cycle stability, cycle life, and safety of the battery.

[0114] In some embodiments, before laminating the first surface of the base film 11 with the non-woven fabric layer 12, it further includes: coating a first slurry containing at least one of organic nano-materials, inorganic nano-materials, and organic-inorganic composite nano-materials on the first surface of the base film 11 close to the non-woven fabric layer 12 to obtain a first coating 13. That is, preparing the aforementioned first coating 13 on the first surface of the base film 11.

[0115] Alternatively, before or after laminating the first surface of the base film 11 with the non-woven fabric layer 12, it further includes: coating a second slurry containing at least one of organic nano-materials, inorganic nano-materials, and organic-inorganic composite nano-materials on the second surface of the base film 11 away from the non-woven fabric layer 12 to obtain a second coating 14. That is, preparing the aforementioned second coating 14 on the second surface of the base film 11.

[0116] Alternatively, coating a first slurry containing at least one of organic nano-materials, inorganic nano-materials, and organic-inorganic composite nano-materials on the first surface of the base film 11 close to the non-woven fabric layer 12 to obtain a first coating 13, and coating a second slurry containing at least one of organic nano-materials, inorganic nano-materials, and organic-inorganic composite nano-materials on the second surface of the base film 11 away from the non-woven fabric layer 12 to obtain a second coating 14. That is, preparing the aforementioned first coating 13 and second coating 14 on both surfaces of the base film 11.

[0117] By preparing a coating on at least one surface of the base film, the mechanical strength of the composite separator can be enhanced, and the risk of dendrite growth piercing the composite separator can be further reduced. For the specific material selection and formation parameters of the first coating 13 and the second coating 14, refer to the above text.

[0118] Figure 5 It is the SEM image of the composite separator prepared in the embodiment, and a non-woven fabric layer material with a three-dimensional network fiber structure is bonded to the surface of the base film.

[0119] In some embodiments, the laminating treatment includes roll laminating treatment, and the coating method can be spraying.

[0120] Battery

[0121] In a third aspect, an embodiment of the present application provides a battery, including a positive electrode plate, a negative electrode plate, and a separator disposed between the positive electrode plate and the negative electrode plate. The separator is the composite separator provided in the first aspect of the embodiments of the present application and / or the composite separator prepared by the preparation method provided in the second aspect of the embodiments of the present application.

[0122] By using the composite separator provided in the first aspect of the embodiments of the present application and / or the composite separator prepared by the preparation method provided in the second aspect of the embodiments of the present application in a battery, the non-woven fabric layer 12 in the composite separator is located between the base film 11 and the negative electrode sheet. Based on the good stability of the composite separator, which is conducive to ion transport and significantly reduces the risk of the negative electrode sheet dendrites continuously growing and piercing the composite separator, the battery can have good cycle stability, cycle life and safety.

[0123] In some embodiments, the battery is a secondary battery. In exemplary embodiments, the secondary battery can be a lithium metal battery or a sodium metal battery, etc. The secondary battery of the embodiments of the present application has a high energy density and good cycle stability, and based on the advantages of the composite separator of the embodiments of the present application, such a secondary battery can be well used as a power battery or a power source for an energy storage system.

[0124] In some embodiments, the battery includes a plurality of electrode assemblies, for example, at least two electrode assemblies. An electrode assembly includes a stacked positive electrode sheet, a composite separator, and a negative electrode sheet. There is no buffer pad between adjacent electrode assemblies. Specifically, for a battery without a negative electrode, metal is deposited on the negative electrode sheet, resulting in a large rebound of the negative electrode sheet. Therefore, a certain metal deposition space is generally reserved to prevent the rebound. However, if a large gap is directly left inside the battery cell during the production of the battery cell, the initial deposition process is not stressed until the battery cell expands to a certain extent and presses against the top shell of the battery cell, which is likely to cause internal short circuit. The function of adding a buffer pad (with a certain compression amount) is to receive a smaller shaping force during the initial deposition, so that the dendrite growth is not out of control and pierces the separator. The internal space of the non-woven fabric here can replace the buffer pad. Based on the addition of the non-woven fabric in the composite separator of the embodiments of the present application, which has a certain stress buffering effect, the buffer pad can be not set and the battery still has good safety performance, thus further reducing the battery cost.

[0125] In some embodiments, the negative electrode sheet is a negative electrode sheet without negative electrode active material, and the corresponding battery is a non-negative metal battery, in which metal deposition occurs on the negative electrode current collector. Due to the high reactivity of the metal, the deposition is likely to be uneven, resulting in an excessive local current density. Based on the composite separator of the embodiments of the present application, the risk of dendrites piercing the surface of the negative electrode sheet without negative active material can be well prevented. Therefore, such a battery has the characteristics of high energy density, good cycle performance and long service life.

[0126] The negative electrode sheet without negative electrode active material can be the negative electrode current collector as the negative electrode sheet. For example, a metal foil or a composite current collector can be used. For example, as the metal foil, aluminum foil or copper foil can be used.

[0127] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode active layer bonded to the positive electrode current collector. Among them, the positive electrode active layer contains a positive electrode active material. When the secondary battery is a lithium metal battery, the positive electrode active material is a lithium-containing material. When the secondary battery is a sodium metal battery, the positive electrode active material is a sodium-containing material.

[0128] In some embodiments, the current collector of the positive electrode sheet, also known as the positive electrode current collector, can be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymer material substrate such as polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, and polyethylene.

[0129] In some embodiments, the secondary battery of the embodiments of the present application can include any one of a battery cell, a battery module, and a battery pack.

[0130] Among them, a battery cell refers to a battery housing and an electrode assembly 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. As Figure 6 shown, the square-shaped battery cell 20.

[0131] In some embodiments, as Figure 7 shown, the outer package of the battery cell 20 can include a housing 21 and a top cover assembly 22. The housing 21 can include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity. The housing 21 has an opening communicating with the receiving cavity, and the top cover assembly 22 is used to cover the opening to close the receiving cavity. The positive electrode sheet, the separator, and the negative electrode sheet contained in the secondary battery of the embodiments of the present application can form an electrode assembly 23 through a winding process and / or a stacking process. The electrode assembly 23 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 23. The number of the electrode assemblies 23 contained in the battery cell 20 can be one or more, and can be adjusted according to actual needs.

[0132] The preparation method of the battery cell 20 is well-known. In some embodiments, the positive electrode sheet, the separator, the negative electrode sheet, and the electrolyte can be assembled to form the battery cell 20. As an example, the positive electrode sheet, the separator, and the negative electrode sheet can be formed into an electrode assembly 23 through a winding process or a stacking process, the electrode assembly 23 is placed in the outer package, dried, and then injected with electrolyte, and after processes such as vacuum packaging, standing, forming, and shaping, the battery cell 20 is obtained.

[0133] The battery module refers to being assembled by the battery cells 20, that is, it can contain multiple battery cells 20, and the specific quantity can be adjusted according to the application and capacity of the battery module.

[0134] In some embodiments, Figure 8 is a schematic diagram of a battery module 30 as an example. In the battery module 30, multiple battery cells 20 can be arranged in sequence along the length direction of the battery module 30. Of course, they can also be arranged in any other way. Further, the multiple battery cells 20 can be fixed by fasteners.

[0135] Optionally, the battery module 30 can further include a housing with an accommodation space, and multiple battery cells 20 are accommodated in the accommodation space.

[0136] The battery pack refers to being assembled by the battery cells 20 above, that is, it can contain multiple battery cells 20, and among them, multiple battery cells 20 can be assembled into the battery module 30 above. The specific quantity of the battery cells 20 or battery modules 30 contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0137] As in the embodiment, Figure 9 and Figure 10 is a schematic diagram of a battery pack 40 as an example. The battery pack 40 can include a battery box and multiple battery modules 30 arranged in the battery box. The battery box includes an upper box body 41 and a lower box body 42. The upper box body 41 is used to cover the lower box body 42 and form a closed space for accommodating the battery modules 30. The multiple battery modules 30 can be arranged in the battery box in any way.

[0138] Power-consuming device

[0139] In a fourth aspect, the embodiments of the present application further provide a power-consuming device. The power-consuming device includes the battery in the embodiments of the present application above. The battery can be used as the power source of the power-consuming device or as the energy storage unit of the power-consuming device. Based on the advantages of the battery in the embodiments of the present application, the power-consuming device in the embodiments of the present application has good cycle performance and safety.

[0140] The power-consuming device can be, but is not limited to, mobile devices (such as mobile phones, laptop computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc. The power-consuming device can select secondary batteries, battery modules or battery packs according to its usage requirements.

[0141] Figure 11It is a schematic diagram of an electrical device as an example. The electrical device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. To meet the requirements of the electrical device for high power and high energy density, a battery pack or a battery module can be adopted.

[0142] As another example, the electrical device can be a mobile phone, a tablet computer, a laptop computer, etc. The electrical device usually requires being thin and light, and a secondary battery can be adopted as the power source.

[0143] Embodiment

[0144] Hereinafter, 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 a limitation to the present application. For those not specified in the embodiments regarding specific technologies or conditions, they shall be carried out according to the technologies or conditions described in the literature in this field or according to the product specifications. For reagents or instruments not specified with the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0145] Embodiment 1

[0146] A composite separator includes a base film and a non-woven fabric layer bonded to the first surface of the base film. The material of the base film is polyethylene (PE) with a thickness of 20 μm; the non-woven fabric material of the non-woven fabric layer is polyester fiber non-woven fabric with a thickness of 10 μm; for details, refer to Table 1.

[0147] The preparation method of the composite separator includes: bonding and laminating the above-mentioned base film and non-woven fabric material to obtain the composite separator.

[0148] Embodiment 2

[0149] A composite separator includes a base film and a non-woven fabric layer bonded to the first surface of the base film, and a first coating is provided between the base film and the non-woven fabric layer. The material of the base film is polyethylene (PE) with a thickness of 20 μm; the non-woven fabric material of the non-woven fabric layer is polyester fiber non-woven fabric with a thickness of 10 μm; the material of the first coating is an organic nano material: aramid fiber (polyphenylene sulfide fiber) with a thickness of 1 μm; for details, refer to Table 1.

[0150] The preparation method of the composite separator includes: spraying aramid fiber nano material on the surface of the above-mentioned base film to form a first coating, and laminating the non-woven fabric layer material on the first coating to obtain the composite separator.

[0151] Embodiment 3

[0152] A composite separator, comprising a base film and a non-woven fabric layer bonded to the first surface of the base film. A first coating is provided between the base film and the non-woven fabric layer, and a second coating is provided on the second surface of the base film away from the non-woven fabric layer. The material of the base film is polyethylene (PE) with a thickness of 20 μm; the non-woven fabric material of the non-woven fabric layer is polyester fiber non-woven fabric with a thickness of 10 μm; the materials of the first coating and the second coating are both organic nano-materials: aramid fiber (polyphenylene sulfide fiber) with a thickness of 1 μm each; for details, see Table 1.

[0153] The preparation method of the composite separator includes: spraying aramid fiber nano-materials on both surfaces of the above-mentioned base film to form the first coating and the second coating, and laminating the non-woven fabric layer material on the first coating to obtain the composite separator.

[0154] Examples 4 - 20: For details, see Table 1.

[0155] Comparative Example 1

[0156] A composite separator, comprising a laminated polyethylene layer and polypropylene layer, with the polyethylene layer having a thickness of 20 μm and the polypropylene layer having a thickness of 15 μm.

[0157] Comparative Example 2

[0158] A composite separator, comprising a laminated polyethylene layer and a first coating, with the material of the first coating being an organic nano-material: aramid fiber, having a thickness of 15 μm and the polyethylene layer having a thickness of 20 μm.

[0159] Comparative Example 3

[0160] A composite separator, comprising a laminated base film and a first coating, with the material of the first coating being an inorganic nano-material: silica, having a thickness of 15 μm and the base film being a polyethylene layer with a thickness of 20 μm.

[0161] Comparative Example 4

[0162] A composite separator, comprising a laminated base film and a first coating, with the material of the first coating being an organic nano-material: aramid fiber, having a thickness of 15 μm and the base film being a polyester fiber non-woven fabric with a thickness of 20 μm.

[0163] Performance Test

[0164] (1) Performance of the composite separator

[0165] 1.1 Young's modulus: Refer to GB / T7757 - 2009. Test method: Cut the composite separator into test samples with a length of 50 mm and a width of 20 mm, and test the elastic modulus through a universal testing machine, with a tensile distance of 50 mm and a test speed of 20 mm / min.

[0166] 1.2 Porosity: Refer to GB / T 24586-2009. Test principle: Using the replacement method of inert gas (helium) with small molecular diameter, combined with Archimedes' principle and Boyle's law (PV=nRT), accurately measure the true volume of the material to be tested, so as to obtain the porosity of the composite separator sample to be tested.

[0167] Calculation formula: Apparent volume V2 = S * H * A; Porosity P = (V2 - V1) / V2 * 100%

[0168] In the formula: S - area, cm 2 ; H - thickness, cm; A - number of samples, EA; V1 - true volume of the sample, cm 3 ; V2 - apparent volume of the sample, cm 3 ; P - porosity of the sample, %.

[0169] 1.3 Thickness: Use a micrometer or microscopic interface thickness measurement method

[0170] 1.4 Air permeability: Gurley method air permeability analysis, refer to GB / T 458-2008. Test principle: The time (s) required for 100 CC of air to pass through a sample with a certain area.

[0171] 1.5 Coating pore size: Estimate the approximate pore size range through the SEM microscopic structure.

[0172] Table 1 shows the material composition and test parameters of the composite separators in the examples and comparative examples.

[0173] (2) Secondary battery single cell test

[0174] Secondary battery single cell, that is, sodium ion full battery assembly:

[0175]

Positive electrode plate

[0176] Mix the positive electrode active material, SuperP and PVDF in a mass ratio of 90:5:5 in sequence, and then obtain the positive electrode plate through homogenization, coating, drying and cold pressing.

[0177]

Negative electrode plate

[0178] Cut the aluminum foil and use it as the negative electrode plate.

[0179]

Separator

[0180] Composite separators of examples and comparative examples.

[0181]

Electrolyte

[0182] Weigh 0.6122 g of sodium perchlorate and add it to 10 ml of propylene carbonate solvent. Stir until the sodium perchlorate is completely dissolved, then add 3% by mass of vinylene carbonate fluoride as an additive. After stirring well, it is used as the electrolyte.

[0183]

Sodium-ion full battery

[0184] In a glove box protected by inert gas, stack the prepared negative electrode sheet, composite separator, and positive electrode sheet (the non-woven fabric layer in the composite separator is close to the negative electrode sheet) tightly in sequence. Drop the electrolyte to completely wet the separator, and then encapsulate the above stacked part into a button cell case to complete the battery assembly, obtaining a sodium-ion full battery.

[0185] Full battery charge-discharge test:

[0186] 2.1 Capacity test of the battery

[0187] At 25 °C, first charge the prepared battery at a constant current of 1C to 3.65V, then charge it at a constant voltage until the current is 0.05C, and then discharge the battery at a constant current of 1C to 1.5V. This is a charge-discharge cycle process, and the discharge capacity this time is used as the battery capacity.

[0188] 2.2 Cycle performance test of the battery

[0189] At 25 °C, first charge the prepared battery at a constant current of 1C to 3.65V, then charge it at a constant voltage until the current is 0.05C, and then discharge the battery at a constant current of 1C to 1.5V. This is a charge-discharge cycle process, and the discharge capacity this time is the discharge capacity of the first cycle. The battery is cycled for charge-discharge test in the above manner. When the discharge capacity of the battery decays to 80% of the discharge capacity of the first cycle, stop the test and record the number of cycles of the battery.

[0190] 2.3 Internal resistance of the battery: DCR = ▲U / I; where, ▲U: voltage change within 30 s of discharge; I: discharge current, and the results are shown in Table 2. Table 2 shows the test results of the batteries assembled with the composite separators of the examples and comparative examples.

[0191] Table 1

[0192]

[0193]

[0194] Table 2

[0195] Case Cycle life DCR (mΩ) Example 1 900cls@80%SOH 9.5 Example 2 980cls@80%SOH 9.2 Example 3 1300cls@80%SOH 7.2 Example 4 730cls@80%SOH 10.6 Example 5 750cls@80%SOH 10.4 Example 6 880cls@80%SOH 9.6 Example 7 850cls@80%SOH 9.7 Example 8 800cls@80%SOH 10.1 Example 9 780cls@80%SOH 10.3 Example 10 952cls@80%SOH 9.5 Example 11 950cls@80%SOH 9.7 Example 12 920cls@80%SOH 10.1 Example 13 970cls@80%SOH 9.2 Example 14 1020cls@80%SOH 8.9 Example 15 1100cls@80%SOH 8.4 Example 16 1200cls@80%SOH 8.0 Example 17 1080cls@80%SOH 8.7 Example 18 1220cls@80%SOH 7.6 Example 19 870cls@80%SOH 9.6 Example 20 800cls@80%SOH 10.1 Comparative Example 1 700cls@80%SOH 10.7 Comparative Example 2 690cls@80%SOH 11 Comparative Example 3 600cls@80%SOH 11.4 Comparative Example 4 500cls@80%SOH 13

[0196] As can be seen from the data in Table 2 above: Due to the use of the unique composite separator in the embodiments of the present application, the battery in the embodiments of the present application has a smaller DCR internal resistance and a better cycle life compared to the comparative examples. Among them, the data of Embodiment 1 and Embodiments 4-9 show that better effects are achieved when the non-woven fabric layer uses polyester fiber and has a thickness of 10-18 μm. By optimizing the material and thickness of the non-woven fabric layer in the composite separator of the embodiments of the present application, and further adding a first coating and a second coating on both surfaces of the base film, the battery performance can be further improved. In Embodiment 3, a non-woven fabric layer with a thickness of 15 μm made of polyester fiber is used, and both the first coating and the second coating use aramid fiber with a thickness of 1 μm, corresponding to better battery effects.

[0197] 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 foregoing embodiments, those of ordinary skill in the art should understand that: They can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; 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 covered within the scope of the claims and the description of the present application. In particular, as long as there is no structural conflict, the technical features mentioned in each embodiment can be combined in any way. The present application is not limited to the specific embodiments disclosed in the text, but includes all technical solutions falling within the scope of the claims.

Claims

1. A composite separator, characterized in that, It includes a base film which has a first surface and a second surface arranged oppositely. The first surface of the base film is provided with a non-woven fabric layer which includes a non-woven fabric material formed by organic polymer fibers, and the porosity of the non-woven fabric layer is at least 40%. The composite separator is used in a battery, and the non-woven fabric layer is adjacent to the negative electrode plate of the battery.

2. The composite separator according to claim 1, wherein, The porosity of the non-woven fabric layer is 47% - 70%.

3. The composite separator according to claim 1 or 2, characterized in that, The thickness of the non-woven fabric layer is 10μm - 35μm; and / or, The thickness of the base film is 5μm - 20μm.

4. The composite separator according to any one of claims 1-3, characterized in that, The organic polymer fibers include at least one of viscose fiber, acetate fiber, polyester fiber, polypropylene fiber, and polyimide fiber; and / or, The material of the base film includes polyolefin.

5. The composite separator according to any one of claims 1-4, characterized in that A first coating is provided between the first surface of the base film and the non-woven fabric layer and / or a second coating is provided on the second surface of the base film. The first coating and the second coating independently include at least one of organic nano-materials, inorganic nano-materials, and organic-inorganic composite nano-materials.

6. The composite separator according to claim 5, wherein The materials of the first coating and the second coating have one or more of the following (1) - (3): (1) The organic nano-materials include at least one of aromatic ring polymers, heteroaromatic ring polymers, aramid fibers, and polyurethane fibers; (2) The inorganic nano-materials include at least one of tin dioxide nano-particles, silicon dioxide nano-particles, and silver nano-particles; (3) The organic-inorganic composite nano-materials include at least one of silicon-polyacrylic acid composite materials, silicon-polyacrylonitrile composite materials, tin-polyacrylic acid composite materials, and tin-polyacrylonitrile composite materials.

7. The composite separator according to claim 5 or 6, characterized in that, The first coating is provided on the first surface of the base film, the second coating is provided on the second surface of the base film, and the first coating includes the organic nano-materials, and the second coating includes the inorganic nano-materials or the organic-inorganic composite nano-materials.

8. The composite separator according to any one of claims 5-7, characterized in that, The pore size of the first coating is 0.2 - 2μm; and / or, The pore size of the second coating is 0.2 - 2μm.

9. The composite separator according to any one of claims 5-8, characterized by The overall porosity of the base film and the first coating and the second coating is 28% - 46%; and / or, The overall thickness of the base film and the first coating and the second coating is 7μm - 25μm.

10. The composite separator according to any one of claims 1-9, characterized in that, The composite separator has one or more of the following (1) - (5): (1) The porosity of the composite separator is 38% - 55%; (2) The Young's modulus in the length direction of the composite separator is 8MPa - 15MPa; (3) The Young's modulus in the width direction of the composite separator is 6MPa - 15MPa; (4) The thickness of the composite separator is 15μm - 55μm; (5) The air permeability of the composite separator is 260s / 100CC - 390s / 100CC.

11. A method for preparing a composite separator according to any one of claims 1-10, characterized in that, It includes the following steps: Bond the first surface of the base film with the non-woven fabric layer to obtain the composite separator.

12. The preparation method according to claim 11, characterized in that, Before laminating the first surface of the base film with the non-woven fabric layer, it further includes: coating a first slurry containing at least one of organic nanomaterials, inorganic nanomaterials, and organic-inorganic composite nanomaterials on the first surface of the base film to obtain a first coating; and / or, Before or after laminating the first surface of the base film with the non-woven fabric layer, it further includes: coating a second slurry containing at least one of organic nanomaterials, inorganic nanomaterials, and organic-inorganic composite nanomaterials on the second surface of the base film to obtain a second coating.

13. A battery, characterized in that, It includes a positive electrode sheet, a negative electrode sheet, and a separator disposed between the positive electrode sheet and the negative electrode sheet. The separator includes the composite separator according to any one of claims 1 to 10 or the composite separator prepared by the preparation method according to any one of claims 11 to 12, and the non-woven fabric layer in the composite separator is located between the base film and the negative electrode sheet.

14. The battery according to claim 13, characterized in that, The negative electrode sheet is a sheet without negative electrode active material.

15. The battery according to claim 13 or 14, characterized in that, The battery includes at least two electrode assemblies, and there is no buffer pad between adjacent electrode assemblies.

16. An electrical device, characterized in that, The electrical device includes the battery according to any one of claims 13 to 15.

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