Diaphragm, secondary battery

Abstract

The application discloses a diaphragm and a secondary battery, and belongs to the technical field of batteries.The diaphragm comprises a base film, an insulating layer arranged on at least one surface of the base film, and a plurality of protruding parts arranged on the surface of the insulating layer away from the base film.The diaphragm is provided with an insulating layer on at least one surface, and a plurality of protruding parts are arranged on the surface of the insulating layer away from the base film, so that a gap is reserved between the diaphragm and a pole piece (a positive pole piece and / or a negative pole piece), a buffer space is provided for the expansion of the pole piece during the use of the secondary battery, the expansion stress on the pole piece is reduced, the pole piece is effectively prevented from being broken, the arrangement of the insulating layer and the protruding parts can improve the structural stability and ionic conductivity of the diaphragm, the deintercalation of lithium ions is promoted, the lithium precipitation phenomenon is avoided, and the safety performance and cycle performance of the secondary battery are effectively improved.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to a separator and a secondary battery. Background Technology

[0002] The electrode assembly of a secondary battery includes a positive electrode, a negative electrode, and a separator that separates the positive and negative electrodes. Typically, the positive electrode, negative electrode, and separator are wound together to form a rolled electrode assembly.

[0003] During the charging and discharging process of a secondary battery, the electrodes expand in volume due to the delithiation or lithium insertion of the active materials. This expansion inevitably generates expansion stress between the electrode and the separator. The expansion deformation gradually accumulates from the inside out, resulting in excessive expansion stress on the outer electrode layer of the electrode assembly. If this expansion stress is not effectively released, when the secondary battery reaches a certain cycle length, it will cause the outer electrode layer to break, triggering a chain reaction of deterioration in the battery's electrochemical performance and shortening the battery's lifespan.

[0004] Therefore, this application is submitted. Utility Model Content

[0005] The purpose of this application is to overcome the shortcomings of the existing technology and provide a separator and a secondary battery. The separator of this application can effectively improve the safety performance and cycle performance of the secondary battery.

[0006] To achieve the above objectives, in a first aspect of this application, a diaphragm is provided, including a base membrane and an insulating layer disposed on at least one surface of the base membrane, wherein the insulating layer has a plurality of protrusions on the surface away from the base membrane.

[0007] As an embodiment of this application, the plurality of protrusions are spaced apart from each other, and the distance between adjacent protrusions is a, which satisfies: 0.1mm≤a≤10mm.

[0008] As an embodiment of this application, the protrusion is circular, elliptical, square, trapezoidal or rhomboid in shape.

[0009] In one embodiment of this application, the height of the protrusion is b, which satisfies: 0.2mm≤b≤4.8mm.

[0010] As an embodiment of this application, the thickness of the insulating layer is d1, which satisfies: 0.2≤b / d1≤0.8.

[0011] As an embodiment of this application, the thickness d1 of the insulating layer satisfies: 1mm≤d1≤6mm.

[0012] As an embodiment of this application, the thickness of the base film is d2, which satisfies: 0.2≤b / d2≤0.48.

[0013] As an embodiment of this application, the thickness d2 of the base film satisfies: 3mm≤d2≤10mm.

[0014] As an embodiment of this application, the distance between the leftmost end and the rightmost end of the protrusion is c, which satisfies: 0.1mm≤c≤10mm.

[0015] In a second aspect of this application, a secondary battery is provided, comprising a positive electrode, a negative electrode, and a separator, wherein the separator is disposed between the positive electrode and the negative electrode, and there is a gap between the separator and the positive electrode and / or between the separator and the negative electrode, wherein the separator comprises the separator described above.

[0016] The beneficial effects of this application are as follows: By providing an insulating layer on at least one surface of the separator and providing multiple protrusions on the surface of the insulating layer away from the base film, and leaving a gap between the separator and the electrode (positive electrode and / or negative electrode), this application provides buffer space for the expansion of the electrode during the use of the secondary battery, reduces the expansion stress on the electrode, and effectively prevents the electrode from breaking. At the same time, the provision of the insulating layer and the protrusions can improve the structural stability and ionic conductivity of the separator, promote the intercalation and deintercalation of lithium ions, avoid lithium plating, and effectively improve the safety performance and cycle performance of the secondary battery. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the diaphragm structure of this application in one embodiment.

[0018] Figure 2 This is a schematic diagram of the diaphragm structure in another embodiment of the present application.

[0019] Figure 3 This is a schematic diagram of the diaphragm structure in another embodiment of the present application.

[0020] Figure 4 This is a schematic diagram of the structure of the secondary battery of this application in one embodiment.

[0021] Reference numerals: 1. Base film; 2. Insulating layer; 3. Protrusion; 4. Positive electrode; 5. Negative electrode. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0023] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0024] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0025] In the description of this utility model, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this utility model. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0026] Unless otherwise specified, all components, raw materials, or instruments used in the embodiments and comparative examples of this utility model are commercially available.

[0027] like Figures 1-2 As shown, an embodiment of this application provides a diaphragm, including a base film 1 and an insulating layer 2 disposed on at least one surface of the base film 1, wherein the insulating layer 2 has a plurality of protrusions 3 on the surface away from the base film 1.

[0028] This application provides an insulating layer 2 on at least one surface of the separator and a plurality of protrusions 3 on the surface of the insulating layer 2 away from the base film 1. A gap is reserved between the separator and the electrode (positive electrode 4 and / or negative electrode 5). During the use of the secondary battery, this provides a buffer space for the expansion of the electrode, reduces the expansion stress on the electrode, and effectively prevents the electrode from breaking. At the same time, the insulating layer 2 and the protrusions 3 can improve the structural stability and ionic conductivity of the separator, promote the intercalation and deintercalation of lithium ions, avoid lithium plating, and effectively improve the safety and cycle performance of the secondary battery.

[0029] In this embodiment, the plurality of protrusions 3 are spaced apart from each other, and the distance between adjacent protrusions 3 is a, which satisfies: 0.1mm≤a≤10mm. For example, it can be 0.1mm, 0.2mm, 0.4mm, 0.5mm, 0.8mm, 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm or any two of these values. By controlling the distance between adjacent protrusions 3 within this range, the structural stability of the separator can be effectively improved, the lithium ion insertion / extraction can be promoted, sufficient buffer space can be provided for the expansion of the electrode, the expansion stress on the electrode can be reduced more effectively, the wetting effect of the electrolyte on the separator can be improved, and the safety performance and cycle performance of the secondary battery can be effectively improved.

[0030] In this embodiment, the protrusion 3 is circular in shape.

[0031] In this embodiment, the height of the protrusion 3 is b, which satisfies: 0.2mm≤b≤4.8mm. For example, it can be 0.2mm, 0.4mm, 0.5mm, 0.8mm, 1mm, 2mm, 3mm, 4mm, 4.5mm, 4.8mm or any two of these values. By controlling the height of the protrusion 3 within this range, the diffusion distance of lithium ions can be shortened, the lithium ion transport efficiency can be improved, sufficient expansion buffer space can be provided, the influence of the height of the protrusion 3 on the membrane thickness can be reduced, and the capacity of the secondary battery can be improved.

[0032] In this embodiment, the thickness of the insulating layer 2 is d1, which satisfies: 0.2≤b / d1≤0.8. For example, it can be 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or any two of these values. By controlling the ratio of the height of the insulating layer 2 to the height of the protrusion 3 within this range, the structural stability of the separator can be improved, the ionic conductivity of the separator can be increased, and the impact of the height of the protrusion 3 on the capacity of the secondary battery can be reduced while meeting the insulation performance requirements. At the same time, it provides a buffer space for electrode expansion, prevents electrode breakage, avoids lithium plating, and effectively improves the safety and cycle performance of the secondary battery.

[0033] In this embodiment, the thickness d1 of the insulating layer 2 satisfies: 1mm≤d1≤6mm, for example, it can be 1mm, 2mm, 3mm, 4mm, 5mm, 6mm or any two of these values.

[0034] In this embodiment, the thickness of the base film 1 is d2, which satisfies: 0.2≤b / d2≤0.48. For example, it can be 0.2, 0.3, 0.4, 0.5, 0.6, 0.8, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 4.8 or any two of these values. By controlling the ratio of the thickness of the base film 1 to the height of the protrusion 3 within this range, the structural stability of the separator can be improved, the thermal stability and puncture strength of the separator can be improved, the formation of lithium dendrites can be suppressed during the charging process (room temperature charging process, low temperature charging process, or high rate charging process), sufficient buffer space can be provided for the expansion of the electrode, the expansion stress on the electrode can be reduced more effectively, the wetting effect of the electrolyte on the separator can be improved, and the safety performance and cycle performance of the secondary battery can be effectively improved.

[0035] In this embodiment, the thickness d2 of the base film 1 satisfies: 3mm≤d2≤10mm, for example, it can be 3mm, 3.5mm, 4mm, 4.5mm, 5mm, 5.5mm, 6mm, 6.5mm, 7mm, 7.5mm, 8mm, 8.5mm, 9mm, 9.5mm, 10mm or any two of these values.

[0036] In this embodiment, the distance between the leftmost and rightmost ends of the protrusion 3 is c, which satisfies: 0.1mm ≤ c ≤ 10mm. For example, it can be 0.1mm, 0.2mm, 0.4mm, 0.5mm, 0.8mm, 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, or any two of these values. By controlling the distance between the leftmost and rightmost ends of the protrusion 3 within this range, the structural stability of the separator can be effectively improved, the lithium ion insertion / extraction can be promoted, sufficient buffer space can be provided for the expansion of the electrode, the expansion stress on the electrode can be reduced more effectively, the wetting effect of the electrolyte on the separator can be improved, and the safety and cycle performance of the secondary battery can be effectively improved.

[0037] The type of base film 1 in this application is not particularly limited and can be selected according to actual needs. Base film 1 can be a polypropylene film, polyethylene film, polyvinylidene fluoride, spandex film, aramid film, or a multilayer composite film modified by coating.

[0038] The insulating layer comprises insulating powder, binder, and dispersant.

[0039] In some embodiments, the mass ratio of the insulating powder, binder, and dispersant is 1:(0.35-0.45):(0.005-0.01).

[0040] In some embodiments, the insulating powder includes at least one of alumina, boehmite, and silicon dioxide.

[0041] In some embodiments, the adhesive includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene-ethylene copolymer, ethylene-vinyl acetate copolymer, and acrylate.

[0042] In some embodiments, the dispersant comprises an ammonium polyacrylate dispersant.

[0043] like Figure 3 As shown, this embodiment provides a diaphragm, including a base film 1 and an insulating layer 2 disposed on at least one surface of the base film 1. The insulating layer 2 has a plurality of protrusions 3 on the surface away from the base film 1, and the protrusions 3 are square in shape.

[0044] like Figure 4 As shown, this embodiment provides a secondary battery, including a positive electrode 4, a negative electrode 5, and a separator. The separator is disposed between the positive electrode 4 and the negative electrode 5, and there is a gap between the separator and the positive electrode 4 and / or between the separator and the negative electrode 5. The separator includes the separator described above.

[0045] In some embodiments, the positive electrode 4 includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, the positive active material layer including a positive active material.

[0046] In some embodiments, the positive electrode active material may be a known positive electrode active material for secondary batteries. As a non-limiting example, the positive electrode active material may include lithium phosphate, lithium transition metal oxide, and their respective modified compounds. However, this application is not limited to these materials or substances, and other conventional materials or substances that can be used as positive electrode active materials for secondary batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Non-limiting examples of lithium transition metal oxides include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds.

[0047] In some embodiments, the type of positive current collector is not particularly limited, and it may be any material known to be suitable for use as a positive current collector.

[0048] In some embodiments, the positive current collector includes metallic materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum, as well as carbon materials such as carbon cloth and carbon paper.

[0049] There are no particular restrictions on the form of the positive electrode current collector. When the positive electrode current collector is a metallic material, it can be in the form of metal foil, metal cylinder, metal strip, metal plate, metal foil, metal mesh, stamped metal, foamed metal, etc. When the positive electrode current collector is a carbon material, it can be in the form of carbon plate, carbon film, carbon cylinder, etc.

[0050] In some embodiments, the positive electrode active material layer further includes a conductive agent and a positive electrode binder.

[0051] In some embodiments, the secondary battery further includes a negative electrode 5, which includes a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector, the negative active material layer including a negative active material.

[0052] In this application, there are no particular restrictions on the negative electrode current collector, as long as it can achieve the purpose of this application. For example, it can be copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, foamed nickel, foamed copper, or composite current collector, etc.

[0053] In some embodiments, the negative electrode active material includes at least one of graphite, silicon-based materials, mesophase microcarbon spheres (MCMB), hard carbon, soft carbon, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, Li-Al alloy, and metallic lithium.

[0054] In some embodiments, the negative electrode active material layer further includes a conductive agent and a negative electrode binder.

[0055] In some embodiments, the types of conductive agents mentioned in this application are not limited, and known conductive agents can be used.

[0056] In some embodiments, the conductive agent includes at least one of carbon materials such as acetylene black, needle coke, carbon nanotubes, and graphene.

[0057] In some embodiments, the type of adhesive mentioned in this application is not limited, and known adhesives can be used.

[0058] In some embodiments, the positive electrode binder and negative electrode binder mentioned each independently include at least one of polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, nitrocellulose, styrene-butadiene rubber, nitrile rubber, fluororubber, isoprene rubber, polybutadiene rubber, ethylene-propylene rubber, polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene-ethylene copolymer.

[0059] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and electrolyte described above.

[0060] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The soft pack can be made of plastic, and examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0061] This application does not impose any particular restrictions on the shape of the secondary battery; it can be cylindrical, square, or other shapes.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit the scope of protection of this application. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the substance and scope of the technical solutions of this application.

Claims

1. A diaphragm, characterized in that, It includes a base film and an insulating layer disposed on at least one surface of the base film, wherein the insulating layer has a plurality of protrusions on the surface away from the base film; The height of the protrusion is b, which satisfies: 0.2mm≤b≤4.8mm; The thickness of the insulating layer is d1, which satisfies: 0.2≤b / d1≤0.8; The thickness of the base film is d2, which satisfies: 0.2≤b / d2≤0.

48.

2. The diaphragm according to claim 1, characterized in that, The multiple protrusions are spaced apart from each other, and the distance between adjacent protrusions is a, which satisfies: 0.1mm≤a≤10mm.

3. The diaphragm according to claim 1, characterized in that, The protrusion can be circular, elliptical, square, trapezoidal, or rhomboid in shape.

4. The diaphragm according to claim 1, characterized in that, The thickness d1 of the insulating layer satisfies: 1mm≤d1≤6mm.

5. The diaphragm according to claim 1, characterized in that, The thickness d2 of the base film satisfies: 3mm≤d2≤10mm.

6. The diaphragm according to claim 1, characterized in that, The distance between the leftmost end and the rightmost end of the protrusion is c, which satisfies: 0.1mm≤c≤10mm.

7. A secondary battery, comprising a positive electrode, a negative electrode, and a separator, wherein the separator is disposed between the positive electrode and the negative electrode, characterized in that, The separator has a gap between itself and the positive electrode and / or the separator has a gap between itself and the negative electrode; the separator includes the separator according to any one of claims 1 to 6.

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