Secondary battery diaphragm, secondary battery and electric device

Abstract

The utility model discloses a secondary battery diaphragm, a secondary battery and an electric device, and relates to the field of battery materials. The diaphragm comprises a base membrane, a heat-resistant ceramic layer and stripe layers, the heat-resistant ceramic layer is arranged on a single face or double faces of the base membrane, the stripe layers are arranged on the double faces of the base membrane, and the heat-resistant ceramic layer is located between the base membrane and the stripe layers; the stripe layer comprises a stripe zone and a spacer zone; the stripe zone comprises stripe belts A and stripe belts B which are crossed with each other, and the spacer zone is formed by a gap between two adjacent stripe belts A and two adjacent stripe belts B; the area of the stripe zone and the area of the spacer zone meet the condition that S1 / S2 is larger than or equal to 10% and smaller than 100%, S1 is the area of the spacer zone, and S2 is the area of the stripe zone. According to the diaphragm, the woven grid-shaped stripe layers are coated on the two surfaces of the diaphragm, and the gaps are formed in the spacer regions which are not coated with stripe bands, so that the electrolyte absorption rate of the diaphragm is favorably improved, the electrolyte retention capacity of the electrolyte is improved, the charge-discharge cycle stability is improved, and the lithium precipitation phenomenon is reduced.

Description

Technical Field

[0001] This utility model relates to the field of battery materials, and in particular to a secondary battery separator, a secondary battery, and an electrical device. Background Technology

[0002] With the increasing severity of global warming and environmental pollution, changing the energy structure and developing new energy sources are crucial strategies for addressing these issues. In recent years, lithium-ion batteries have been widely used in consumer electronics, electric vehicles, and large-scale electric equipment such as electric bicycles due to their advantages including high voltage, high cycle life, and long storage time. Therefore, future development of lithium-ion batteries inevitably requires a comprehensive improvement in energy density, cycle life, and safety performance, which necessitates the development of higher-performance separators to match these requirements.

[0003] Currently, separators are mainly coated with organic and / or ceramic coatings to improve performance such as cycle life, energy density, and mechanical strength. However, separator coatings are usually fully coated with high surface density and 100% coverage, resulting in strong adhesion to the electrodes. However, this coating is prone to pore blockage, which is detrimental to lithium-ion transport. As a result, the kinetic performance of the battery decreases after assembly, and the coating has weak electrolyte storage capacity, making it prone to lithium plating during cycling. Utility Model Content

[0004] This invention provides a secondary battery separator, a secondary battery, and an electrical device. By coating the separator with a cross-shaped stripe layer, the electrolyte absorption rate and storage capacity of the separator can be improved, effectively reducing lithium plating during charge-discharge cycles.

[0005] To solve the above-mentioned technical problems, one of the objectives of this utility model is to provide a secondary battery separator, including a base film, a heat-resistant ceramic layer and a stripe layer, wherein the heat-resistant ceramic layer is disposed on one or both sides of the base film, the stripe layer is disposed on both sides of the base film, and the heat-resistant ceramic layer is located between the base film and the stripe layer.

[0006] The stripe layer includes stripe band areas and interval areas;

[0007] The striped area includes striped stripes A and striped stripes B that are arranged intersecting each other. Each striped stripe A and striped stripe B is independent and has at least two of each. There is a gap between adjacent striped stripes A or adjacent striped stripes B and they are parallel to each other.

[0008] The interval region is formed by the interval between two adjacent stripe bands A and two adjacent stripe bands B;

[0009] The areas of the striped band regions and the spacer regions in the striped layer satisfy the following relationship:

[0010] 10%≤S1 / S2<100%;

[0011] In the formula, S1 is the area of ​​the interval region and S2 is the area of ​​the stripe region.

[0012] This application involves coating a striped layer on both sides of the separator. The striped layer can be arranged in a woven mesh pattern. The intersecting stripes form several uncoated meshes in the interstices, which facilitates the penetration of electrolyte into the separator and increases the electrolyte absorption rate of the separator. Furthermore, the interstices without stripes are conducive to electrolyte storage. By controlling the ratio of the interstices area to the stripe area, the electrolyte retention during cyclic charging and discharging can be effectively increased, reducing lithium plating and especially avoiding electrolyte depletion at the corners of the cell.

[0013] As a preferred embodiment, the areas of the striped band region and the interval region in the striped layer satisfy the following relationship: 20%≤S1 / S2≤50%.

[0014] As a preferred embodiment, the areas of the striped band region and the interval region in the striped layer satisfy the following relationship: S1 / S2=30%.

[0015] As a preferred embodiment, the included angle formed by the intersection of the stripe A and stripe B is 90°, which can form a square grid on the surface of the diaphragm, which is beneficial to improving the absorption and storage of electrolyte by the diaphragm. At this time, the diaphragm has the best ability to absorb and retain electrolyte.

[0016] As a preferred embodiment, stripe A and stripe B are each independent and have an angle greater than 0° and less than 90° with one of the sides of the base film.

[0017] As a preferred embodiment, the angle between stripe A and stripe B and one of the sides of the base membrane is 30°-60°, preferably 45°. Stripe A and stripe B can intersect with the sides of the base membrane to form an angle to store electrolyte. In this case, the membrane has the best ability to absorb and retain electrolyte.

[0018] As a preferred embodiment, the thickness of stripe A and stripe B is independently 0.5-5 μm.

[0019] As a preferred embodiment, the thickness of stripe A and stripe B are each independently within the range of any one or any two of the following: 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, and 5 μm.

[0020] As a preferred embodiment, the thickness of stripe A and stripe B is independently 1-3 μm.

[0021] As a preferred embodiment, the vertical height difference between the stripe band area and the interval area in the stripe layer is 0.5-10 μm.

[0022] As a preferred embodiment, the vertical height difference between the stripe band area and the interval area in the stripe layer is 1-6 μm.

[0023] As a preferred embodiment, the ratio of the width of a single stripe A to the width of the interval between two adjacent stripe A in the stripe layer is 1-10, preferably 4-6. In this case, the interval area on the diaphragm can effectively store and retain electrolyte, thereby improving the liquid absorption and retention capacity.

[0024] As a preferred embodiment, the ratio of the width of a single stripe B in the stripe layer to the width of the interval between two adjacent stripe B is 1-10, preferably 4-6. In this case, the interval area on the diaphragm can effectively store and retain electrolyte, thereby improving the liquid absorption and retention capacity.

[0025] As a preferred embodiment, the widths of stripe A and stripe B are each independently 1.0-3.0 mm.

[0026] As a preferred embodiment, the spacing between two adjacent stripes A is 0.3-1.0 mm, and the spacing between two adjacent stripes B is 0.3-1.0 mm.

[0027] As a preferred embodiment, the stripe layer is a coating of polyvinylidene fluoride and / or its copolymer derivatives.

[0028] As a preferred embodiment, the polyvinylidene fluoride copolymer derivative is at least one of the following: vinylidene fluoride-trifluorochloroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether copolymer, vinylidene fluoride-vinylidene fluoride-propylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene difluoride-hexafluoropropylene copolymer, and vinylidene difluoride-tetrafluoroethylene copolymer.

[0029] As a preferred embodiment, the stripe layer is a polyvinylidene fluoride coating.

[0030] As a preferred embodiment, the heat-resistant ceramic layer is at least one of silicon dioxide, aluminum oxide, silicon oxide, calcium oxide, magnesium oxide, ZnO, TiO2, boehmite, and ceramic fiber.

[0031] As a preferred embodiment, the heat-resistant ceramic layer is alumina.

[0032] This application provides a heat-resistant ceramic layer on one or both sides of the separator. The ceramic can improve the high temperature resistance of the separator, improve the thermal stability and safety of the battery, and enhance the mechanical strength of the separator. It also avoids the contact of the positive and negative large areas caused by the shrinkage of the separator. The porosity of the heat-resistant ceramic layer is usually larger than that of the base film, which can increase the wettability of the electrolyte to the separator and further improve the electrolyte retention of the separator.

[0033] As a preferred embodiment, the base membrane is any one of polyethylene microporous membrane, polypropylene microporous membrane, polyethylene-polypropylene composite microporous membrane, polyethylene terephthalate microporous membrane, and polyimide microporous membrane.

[0034] As a preferred embodiment, the base membrane is a polypropylene microporous membrane.

[0035] As a preferred embodiment, the thickness of the heat-resistant ceramic layer is 0.5-2.0 μm.

[0036] As a preferred embodiment, the thickness of the base film is 3-16 μm.

[0037] To solve the above-mentioned technical problems, the second objective of this utility model is to provide a secondary battery, which includes the aforementioned secondary battery separator.

[0038] To solve the above-mentioned technical problems, the third objective of this utility model is to provide an electrical device, including the aforementioned secondary battery.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] 1. This application uses a grid-like stripe coating on both sides of the separator, with the stripe not coated in the spacer area of ​​the stripe layer. This facilitates the permeation of electrolyte into the separator, increases the electrolyte absorption rate of the separator, and allows a large amount of electrolyte to be stored in the spacer area of ​​the stripe layer. This effectively increases the electrolyte retention during cyclic charging and discharging, reduces lithium plating, and especially avoids electrolyte depletion at the corners of the battery cell.

[0041] 2. This application provides a heat-resistant ceramic layer on one or both sides of the separator. The ceramic can improve the high temperature resistance of the separator, improve the thermal stability and safety of the battery, and enhance the mechanical strength of the separator. The porosity of the heat-resistant ceramic layer is usually larger than that of the base membrane, which can increase the wettability of the electrolyte to the separator and further improve the electrolyte retention of the separator. Attached Figure Description

[0042] Figure 1 This is a cross-sectional structural diagram of a secondary battery separator in an embodiment of this utility model.

[0043] Figure 2 This is a schematic diagram of the front structure of the striped layer of a secondary battery separator in an embodiment of this utility model.

[0044] The reference numerals in the accompanying drawings are as follows: 1. Base film; 2. Heat-resistant ceramic layer; 3. Striped layer; 31. Striped band area; 32. Spacing area. Detailed Implementation

[0045] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0046] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, regarding numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included within this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0047] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0048] As used in this article:

[0049] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0050] In the description of this utility model, it should be understood that the terms "upper", "lower", "left", "right", "top", "bottom", etc., indicating the orientation or positional relationship, are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0051] To further illustrate this utility model, the following detailed description is provided in conjunction with embodiments, but these descriptions should not be construed as limiting the scope of protection of this utility model. Unless otherwise specified, the raw materials used in the following embodiments and comparative examples are commercially available, and the same raw materials were used in parallel experiments.

[0052] Example 1

[0053] A secondary battery separator, such as Figure 1 As shown, the structure includes a base membrane 1, a heat-resistant ceramic layer 2, and a stripe layer 3. The base membrane 1 can be a polyethylene microporous membrane (PE), a polypropylene microporous membrane (PP), a polyethylene-polypropylene composite microporous membrane (PE-PP), a polyethylene terephthalate microporous membrane (PET), or a polyimide microporous membrane (PI), with a thickness of 3-16 μm. In this embodiment, the base membrane 1 is specifically a polypropylene microporous membrane with a thickness of 10 μm. The heat-resistant ceramic layer is coated on one or both sides of the base membrane. In this embodiment, the heat-resistant ceramic layer 2 is specifically coated on the side of the base membrane facing the positive electrode. The heat-resistant ceramic layer 2 can be at least one of silicon dioxide, alumina, silicon oxide, calcium oxide, magnesium oxide, ZnO, TiO2, boehmite, and ceramic fiber, with a thickness of 0.5-2 μm. In this embodiment, the heat-resistant ceramic layer 2 is specifically alumina with a thickness of 1 μm. Two stripe layers 3 are provided, respectively coated on both sides of the base film, and the heat-resistant ceramic layer 2 is located between the base film 1 and the stripe layer 3. The stripe layer 3 can be polyvinylidene fluoride or its copolymer derivative. The polyvinylidene fluoride copolymer derivative can be at least one of the following: vinylidene fluoride-trifluorochloroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether copolymer, vinylidene fluoride-vinylidene fluoride copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene difluoride-hexafluoropropylene copolymer, and vinylidene difluoride-tetrafluoroethylene copolymer. In this embodiment, the stripe layer 3 is specifically a polyvinylidene fluoride coating.

[0054] Specifically, the front side of stripe layer 3 is as follows: Figure 2As shown, the striped layer 3 includes striped band regions 31 and spacer regions 32. Striped band regions 31 include intersecting striped bands A and B, with at least two of each. Adjacent striped bands A and B are spaced apart and parallel to each other, and adjacent striped bands B are also spaced apart and parallel to each other. Spacer regions 32 are formed by the gaps between adjacent striped bands A and B. Striped bands A and B are independent and form an angle greater than 0° and less than 90° with any side of the base membrane 1. In this embodiment, striped bands A and B are arranged perpendicularly to each other to form a woven mesh. The areas where the stripes intersect are square-shaped, and the angle between striped bands A and B and any side of the base membrane 1 is 45°. At this angle, the membrane's ability to absorb and retain electrolyte is optimal.

[0055] Specifically, the thickness of stripe A and stripe B can be 0.5-5 μm, preferably 1-3 μm. The vertical height difference h between the interval region 32 and the stripe region 31 of stripe layer 3 is 0.5≤h≤10 μm, preferably 1≤h≤6 μm. The vertical height difference h between the interval region 32 and the intersection region of stripe A and stripe B is 1≤h≤10 μm, preferably 2≤h≤6 μm. In this embodiment, the thickness of stripe A and stripe B is specifically 1 μm, the vertical height difference h between the interval region 32 and the stripe region 31 of stripe layer 3 is 1≤h≤2 μm, and the vertical height difference h between the interval region 32 and the intersection region of stripe A and stripe B is 2 μm.

[0056] Specifically, the area of ​​the interval region 32 of the striped layer 3 is set to S1, and the area of ​​the striped band region 31 is set to S2. The area ratio of the interval region 32 and the striped band region 31 of the striped layer 3 is 10%≤S1 / S2<100%, preferably 20%≤S1 / S2<50%. In this embodiment, the area ratio of the interval region 32 and the striped band region 31 of the striped layer 3 is specifically 30%.

[0057] Specifically, the widths of stripe A and stripe B are independent and can be 1.0-3.0 mm, or the interval between two adjacent stripe A stripes can be 0.3-1.0 mm, and the interval between two adjacent stripe B stripes can be 0.3-1.0 mm. In this embodiment, the width of both stripe A and stripe B is 1.0 mm.

[0058] Example 2

[0059] A secondary battery separator includes a base membrane 1, a heat-resistant ceramic layer 2, and a stripe layer 3. The base membrane 1 is specifically a polypropylene microporous membrane with a thickness of 10 μm. The heat-resistant ceramic layer 2 is specifically coated on one side of the base membrane 1, and is specifically made of alumina with a thickness of 1 μm. Two stripe layers 3 are provided, coated on both sides of the base membrane 1 respectively, with the heat-resistant ceramic layer 2 located between the base membrane 1 and the stripe layer 3. The stripe layer 3 is specifically a polyvinylidene fluoride coating.

[0060] Specifically, the striped layer 3 includes striped band regions 31 and spacer regions 32. Striped band regions 31 include intersecting stripes A and B, with at least two of each. Adjacent stripes A are spaced apart and parallel to each other, as are adjacent stripes B. Spacer regions 32 are formed by the gaps between adjacent stripes A and B. Stripes A and B are arranged perpendicularly to each other, forming a woven mesh. The areas where the stripes intersect are square in shape, and the angle between stripes A and B and one of the sides of the base film 1 is 45°.

[0061] Specifically, the thickness of stripe A and stripe B is 2 μm. The vertical height difference h between the spacer region 32 and the stripe region 31 of stripe layer 3 is 2 ≤ h ≤ 4 μm. The vertical height difference h between the spacer region 32 of stripe layer 3 and the intersection area of ​​stripe A and stripe B in the diaphragm is 4 μm. The area ratio of the spacer region 32 and the stripe region 31 of stripe layer 3 is 30%. The width of stripe A and stripe B is 1.0 mm.

[0062] Example 3

[0063] A secondary battery separator includes a base membrane 1, a heat-resistant ceramic layer 2, and a stripe layer 3. The base membrane 1 is specifically a polypropylene microporous membrane with a thickness of 10 μm. The heat-resistant ceramic layer 2 is specifically coated on one side of the base membrane 1, and is specifically made of alumina with a thickness of 1 μm. Two stripe layers 3 are provided, coated on both sides of the base membrane 1 respectively, with the heat-resistant ceramic layer 2 located between the base membrane 1 and the stripe layer 3. The stripe layer 3 is specifically a polyvinylidene fluoride coating.

[0064] Specifically, the striped layer 3 includes striped band regions 31 and spacer regions 32. Striped band regions 31 include intersecting stripes A and B, with at least two of each. Adjacent stripes A are spaced apart and parallel to each other, as are adjacent stripes B. Spacer regions 32 are formed by the gaps between adjacent stripes A and B. Stripes A and B are arranged perpendicularly to each other, forming a woven mesh. The areas where the stripes intersect are square in shape, and the angle between stripes A and B and one of the sides of the base film 1 is 45°.

[0065] Specifically, the thickness of stripe A and stripe B is 0.5 μm. The vertical height difference h between the spacer region 32 and the stripe region 31 of stripe layer 3 is 0.5 ≤ h ≤ 1 μm. The vertical height difference h between the spacer region 32 and the intersection region of stripe A and stripe B is 1 μm. The area ratio of the spacer region 32 and the stripe region 31 of stripe layer 3 is 30%. The width of stripe A and stripe B is 1.0 mm.

[0066] Example 4

[0067] A secondary battery separator includes a base membrane 1, a heat-resistant ceramic layer 2, and a stripe layer 3. The base membrane 1 is specifically a polypropylene microporous membrane with a thickness of 10 μm. The heat-resistant ceramic layer 2 is specifically coated on one side of the base membrane 1, and is specifically made of alumina with a thickness of 1 μm. Two stripe layers 3 are provided, coated on both sides of the base membrane 1 respectively, with the heat-resistant ceramic layer 2 located between the base membrane 1 and the stripe layer 3. The stripe layer 3 is specifically a polyvinylidene fluoride coating.

[0068] Specifically, the striped layer 3 includes striped band regions 31 and spacer regions 32. Striped band regions 31 include intersecting stripes A and B, with at least two of each. Adjacent stripes A are spaced apart and parallel to each other, as are adjacent stripes B. Spacer regions 32 are formed by the gaps between adjacent stripes A and B. Stripes A and B are arranged perpendicularly to each other, forming a woven mesh. The areas where the stripes intersect are square in shape, and the angle between stripes A and B and one of the sides of the base film 1 is 45°.

[0069] Specifically, the thickness of stripe A and stripe B is 1 μm; the vertical height difference h between the spacer region 32 and the stripe region 31 of stripe layer 3 is 1 ≤ h ≤ 2 μm; and the vertical height difference h between the spacer region 32 and the intersection region of stripe A and stripe B is 2 μm. The area ratio of the spacer region 32 and the stripe region 31 of stripe layer 3 is 20%. The width of stripe A and stripe B is 2.0 mm.

[0070] Example 5

[0071] A secondary battery separator includes a base membrane 1, a heat-resistant ceramic layer 2, and a stripe layer 3. The base membrane 1 is specifically a polypropylene microporous membrane with a thickness of 10 μm. The heat-resistant ceramic layer 2 is specifically coated on one side of the base membrane 1, and is specifically made of alumina with a thickness of 1 μm. Two stripe layers 3 are provided, coated on both sides of the base membrane 1 respectively, with the heat-resistant ceramic layer 2 located between the base membrane 1 and the stripe layer 3. The stripe layer 3 is specifically a polyvinylidene fluoride coating.

[0072] Specifically, the striped layer 3 includes striped band regions 31 and spacer regions 32. Striped band regions 31 include intersecting stripes A and B, with at least two of each. Adjacent stripes A are spaced apart and parallel to each other, as are adjacent stripes B. Spacer regions 32 are formed by the gaps between adjacent stripes A and B. Stripes A and B are arranged perpendicularly to each other, forming a woven mesh. The areas where the stripes intersect are square in shape, and the angle between stripes A and B and one of the sides of the base film 1 is 45°.

[0073] Specifically, the thickness of stripe A and stripe B is 1 μm. The vertical height difference h between the spacer region 32 and the stripe region 31 of stripe layer 3 is 1 ≤ h ≤ 2 μm. The vertical height difference h between the spacer region 32 and the intersection region of stripe A and stripe B is 2 μm. The area ratio of the spacer region 32 and the stripe region 31 of stripe layer 3 is 50%. The width of stripe A and stripe B is 2 mm.

[0074] Comparative Example 1

[0075] A secondary battery separator includes a base membrane 1, a heat-resistant ceramic layer 2, and a stripe layer 3. The base membrane 1 is specifically a polypropylene microporous membrane with a thickness of 10 μm. The heat-resistant ceramic layer 2 is specifically coated on one side of the base membrane 1, and is specifically made of alumina with a thickness of 1 μm. Two stripe layers 3 are provided, coated on both sides of the base membrane 1 respectively, with the heat-resistant ceramic layer 2 located between the base membrane 1 and the stripe layer 3. The stripe layer 3 is specifically a polyvinylidene fluoride coating.

[0076] Specifically, the striped layer 3 includes striped band regions 31 and spacer regions 32. Striped band regions 31 include intersecting stripes A and B, with at least two of each. Adjacent stripes A are spaced apart and parallel to each other, as are adjacent stripes B. Spacer regions 32 are formed by the gaps between adjacent stripes A and B. Stripes A and B are arranged perpendicularly to each other, forming a woven mesh. The areas where the stripes intersect are square in shape, and the angle between stripes A and B and one of the sides of the base film 1 is 45°.

[0077] Specifically, the thickness of stripe A and stripe B is 1 μm; the vertical height difference h between the spacer region 32 and the stripe region 31 of stripe layer 3 is 1 ≤ h ≤ 2 μm; and the vertical height difference h between the spacer region 32 and the intersection region of stripe A and stripe B is 2 μm. The area ratio of the spacer region 32 and the stripe region 31 of stripe layer 3 is 5%. The width of stripe A and stripe B is 1.0 mm.

[0078] Comparative Example 2

[0079] A secondary battery separator includes a base membrane 1, a heat-resistant ceramic layer 2, and a stripe layer 3. The base membrane 1 is specifically a polypropylene microporous membrane with a thickness of 10 μm. The heat-resistant ceramic layer 2 is specifically coated on one side of the base membrane 1, and is specifically made of alumina with a thickness of 1 μm. Two stripe layers 3 are provided, coated on both sides of the base membrane 1 respectively, with the heat-resistant ceramic layer 2 located between the base membrane 1 and the stripe layers 3. The stripe layer 3 is specifically a polyvinylidene fluoride coating. The coating thickness of the stripe layer 3 is specifically 1 μm, and the uncoated area of ​​the stripe layer 3 on the separator is 0, i.e., the stripe layer 3 is fully coated.

[0080] Comparative Example 3

[0081] A secondary battery separator includes a base membrane 1, a heat-resistant ceramic layer 2, and a stripe layer 3. The base membrane 1 is specifically a polypropylene microporous membrane with a thickness of 10 μm. The heat-resistant ceramic layer 2 is specifically coated on one side of the base membrane 1, and is specifically made of alumina with a thickness of 1 μm. Two stripe layers 3 are provided, coated on both sides of the base membrane 1 respectively, with the heat-resistant ceramic layer 2 located between the base membrane 1 and the stripe layer 3. The stripe layer 3 is specifically a polyvinylidene fluoride coating.

[0082] Specifically, the striped layer 3 includes a striped band region 31 and a spacer region 32. The striped band region 31 includes stripes A, with at least two stripes A arranged parallel to each other and spaced apart from adjacent stripes A. The spacer region 32 is formed by the gap between two adjacent stripes A. One of the angles between the stripe A and any side of the base film 1 is 90°. The width of the stripe A is 1.0 mm.

[0083] Specifically, the thickness of stripe A is 1 μm, and the area ratio of the spacer region to the stripe region in stripe layer 3 is 30%.

[0084] Comparative Example 4

[0085] A secondary battery separator includes a base membrane 1 and a heat-resistant ceramic layer 2. The base membrane 1 is specifically a polypropylene microporous membrane with a thickness of 10 μm. The heat-resistant ceramic layer 2 is specifically coated on one side of the base membrane 1 and is specifically alumina with a thickness of 1 μm.

[0086] Performance testing

[0087] 1. Battery capacity retention: At 25 °C, the separators prepared in the examples and comparative examples were assembled into lithium-ion batteries. The batteries were charged at a constant current of 3 C to 4.35 V, then charged at a constant current and voltage of 1.8 C to 4.48 V, with a cutoff current of 0.05 C, and then discharged at 0.7 C to 3.0 V. Following the above charge-discharge cycle, the lithium-ion batteries were subjected to 800 cycles. The capacity retention rate after the 800th cycle was recorded. The test results are shown in Table 2 below.

[0088] 2. Lithium plating interface evaluation: The battery after 800 cycles was fully charged, then disassembled, and the state of the negative electrode was recorded by taking pictures. The area of ​​lithium plating in the black spots on the interface was counted, and the lithium plating level was evaluated according to the standard in Table 1. The evaluation results are shown in Table 2 below.

[0089] Table 1 - Evaluation Criteria for Lithium Plaque Grade of Negative Electrode Sheets After Charge and Discharge of Lithium-ion Batteries

[0090]

[0091] Table 2 - Lithium plating evaluation results of the membrane-assembled batteries in the embodiments and comparative examples of this application.

[0092]

[0093] As shown in Table 2, this application coats a woven mesh-like striped layer on both sides of the separator. The square mesh formed by the spacers promotes electrolyte penetration into the separator, increasing the electrolyte storage capacity. In Example 1, the ratio of the spacer area to the striped stripe area is controlled at 30%, which effectively improves the electrolyte retention during charge-discharge cycles, eliminates lithium plating, and enhances the battery's long-cycle capacity retention. In contrast, in Comparative Example 1, the ratio of the spacer area to the striped stripe area is 5%, resulting in excessive stripe coating area. In Comparative Example 2, the striped layer is fully coated, leading to low electrolyte absorption rate and low storage capacity on the separator. This results in severe lithium plating during long-term charge-discharge cycles and a decrease in capacity retention.

[0094] Compared to Example 1, the striped layer of Comparative Example 3 is arranged with parallel stripes spaced apart. The amount of electrolyte stored in the separator is reduced compared to Example 1, which leads to lithium plating during the charge-discharge cycle of the battery. The electrolyte retention energy of the separator decreases, and the capacity retention rate decreases.

[0095] Compared to Example 1, the separator in Comparative Example 4 did not have a striped layer coated on both sides, which greatly reduced the separator's ability to store electrolyte and resulted in severe lithium plating. Furthermore, the weak adhesion between the separator and the electrode was detrimental to the later cycle performance of the battery, leading to poorer battery cycle performance.

[0096] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this utility model. It should be understood that the above descriptions are merely specific embodiments of this utility model and are not intended to limit the scope of protection of this utility model. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model by those skilled in the art should be included within the scope of protection of this utility model.

Claims

1. A secondary battery separator, characterized by, The strip layer (3) comprises a strip zone (31) and a spacing zone (32). The strip zone (31) comprises strip A and strip B which are arranged in cross. The spacing zone (32) is formed by the spacing between the adjacent two strip A and the adjacent two strip B. The area of the strip zone (31) and the spacing zone (32) in the strip layer (3) satisfies the following relationship: 10%≤S1 / S2<100%; The angle between the strip A and strip B and the side of the base film (1) is 30°-60°. The thickness of the strip A and strip B is independently 0.5-5 μm.

2. The secondary battery separator of claim 1, wherein The vertical height difference between the strip zone (31) and the spacing zone (32) in the strip layer (3) is 0.5-10 μm.

3. The secondary battery separator of claim 1, wherein The ratio of the spacing width between the adjacent two strip A to the single strip A in the strip layer (3) is 1-10.

4. The secondary battery separator of claim 1, wherein The ratio of the width of the single strip B to the spacing width between the adjacent two strip B in the strip layer (3) is 1-10. The width of the strip A and strip B is independently 1.0-3.0 mm.

5. The secondary battery separator of claim 1, wherein The spacing width between the adjacent two strip A is 0.3-1.0 mm, and the spacing width between the adjacent two strip B is 0.3-1.0 mm. The thickness of the heat-resistant ceramic layer (2) is 0.5-2 um.

6. The secondary battery separator of claim 5, wherein The thickness of the base film (1) is 3-16 um. The secondary battery separator according to any one of claims 1-8.

7. The secondary battery separator of claim 1, wherein The secondary battery according to claim 9.

8. The secondary battery separator of claim 1, wherein ​ 9. A secondary battery characterized by comprising: ​ 10. An electrical device, characterized by ​

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