A diaphragm, an electric core and a secondary battery

Abstract

The utility model belongs to battery technical field, concretely relates to a diaphragm, electric core and secondary battery, wherein, the diaphragm includes base body, heat -resistant protective coating and support heat -resistant coating, the base body has first surface along the thickness direction, the first surface has first edge area, the heat -resistant protective coating is connected to the first surface, the support heat -resistant coating is arranged in the heat -resistant protective coating far from the base body one side surface, and the support heat -resistant coating is opposite with first edge area arrangement. The utility model can reduce the risk of diaphragm inwards contraction, and can improve use stability and security.

Description

Technical Field

[0001] This utility model belongs to the field of battery technology, and in particular relates to a separator, a battery cell and a secondary battery. Background Technology

[0002] Lithium-ion batteries typically consist of a positive electrode, a separator, a negative electrode, an electrolyte, and a casing. The separator, positioned between the positive and negative electrodes, blocks the electron shuttle between them, ensuring battery safety. Lithium-ion batteries possess advantages such as high energy density, long cycle life, low self-discharge rate, and environmental friendliness, leading to their widespread application in aviation, aerospace, marine, and electric vehicle industries. The performance of the separator in a lithium-ion battery determines its interface structure and internal resistance, directly impacting its capacity, cycle life, and safety characteristics. Safety issues, particularly its performance under high temperature, overcharge, and short-circuit conditions, pose a significant challenge for large-scale applications.

[0003] However, when lithium-ion batteries are subjected to thermal shock, the separator between the positive and negative electrodes is prone to shrinking inward, posing a risk of short circuit between the positive and negative electrodes. Furthermore, the separator at the edge of the bare cell experiences less shrinkage resistance, making it more susceptible to curling; therefore, the separator structure of some existing bare cells has poor stability. Utility Model Content

[0004] The purpose of this invention is to provide a diaphragm that addresses the shortcomings of existing technologies and solves the problem of poor stability in the use of existing technologies.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A diaphragm includes a substrate, a heat-resistant protective coating, and a supporting heat-resistant coating; the substrate has a first surface along its thickness direction; the first surface has a first edge region; the heat-resistant protective coating is connected to the first surface; the supporting heat-resistant coating is disposed on the side of the heat-resistant protective coating away from the substrate; and the supporting heat-resistant coating is disposed opposite to the first edge region.

[0007] Preferably, the substrate has a second surface opposite to the first surface along its thickness direction; the second surface has a second edge region; and the supporting heat-resistant coating is disposed on the second edge region of the second surface.

[0008] Preferably, there are two first edge regions, which are respectively located on both sides of the first surface of the substrate along its width direction. There are also two second edge regions, which are respectively located on both sides of the second surface of the substrate along its width direction.

[0009] Preferably, the heat-resistant protective coating is a first ceramic coating; the supporting heat-resistant coating is a second ceramic coating; and the particle size of the ceramic particles in the first ceramic coating is smaller than that in the second ceramic coating.

[0010] Preferably, the relationship between the thickness M of the heat-resistant protective coating and the thickness N of the supporting heat-resistant coating satisfies: 2≥N / (M+2)≥0.5;

[0011] And / or the thickness M of the heat-resistant protective coating satisfies: 1μm≤M≤2μm;

[0012] And / or the thickness N of the supporting heat-resistant coating satisfies: 8μm≥N≥2μm.

[0013] Preferably, on the same side surface of the substrate, there are at least two supporting heat-resistant coatings, and an assembly gap is provided between two adjacent supporting heat-resistant coatings.

[0014] Preferably, the matrix is ​​selected from polypropylene or polyethylene;

[0015] Furthermore, the porosity of the matrix is ​​30% to 65%; and / or the thickness P of the matrix satisfies: 6.5 μm ≥ P ≥ 3.5 μm.

[0016] Preferably, an adhesive coating is provided between the supporting heat-resistant coating and the heat-resistant protective coating; and the supporting heat-resistant coating covers and is connected to the side surface of the adhesive coating; the adhesive coating is connected to the heat-resistant protective coating.

[0017] This utility model also discloses a battery cell, including a separator and an electrode body. The electrode body includes a first electrode and a second electrode with opposite polarities. The separator is disposed between the first electrode and the second electrode. The first electrode, the separator, and the second electrode are stacked and wound together to form a wound body. The separator is the separator described above.

[0018] The battery cell has a first end and a second end along its length, with the first end and the second end disposed opposite to each other. At the first end, the separator extends beyond the electrode body by a dimension of d3, and the supporting heat-resistant coating has a dimension of d1, satisfying: 65%*d3≤d1≤95%*d3; and / or d3 satisfies: 1.5mm≤d3≤3mm.

[0019] This utility model also discloses a secondary battery, including the aforementioned battery cell.

[0020] The beneficial effects of this utility model are that the technical solution increases the edge heat resistance of the diaphragm by using the outermost supporting heat-resistant coating, thereby reducing the risk of the diaphragm shrinking inward; and combined with the heat resistance and structural stability of the middle layer heat-resistant protective coating, it can further increase the stability of the main structure of the diaphragm; thereby reducing the risk of short circuit in the electrochemical device; and at the same time, ensuring the diaphragm puncture strength can also help improve ED; thus improving the stability and safety of use. Attached Figure Description

[0021] The following will refer to the appendix. Figures 1-4 This section describes the features, advantages, and technical effects of exemplary embodiments of the present invention.

[0022] Figure 1 This is a front view of the diaphragm according to an embodiment of the present invention;

[0023] Figure 2 This is a front view of the diaphragm according to another embodiment of the present invention;

[0024] Figure 3 This is a top view of the diaphragm according to an embodiment of the present invention;

[0025] Figure 4 This is a schematic diagram of the structure of a battery cell according to an embodiment of the present invention.

[0026] In the figure: 1-substrate; 101-first surface; 102-second surface; 103-first edge region; 104-second edge region; 2-heat-resistant protective coating; 201-assembly gap; 3-supporting heat-resistant coating; 41-adhesive coating; 400-separation membrane; 500-electrode body; 510-electrode body. Detailed Implementation

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is intended to particularly describe embodiments and not to limit the scope of this application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0028] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. "Multiple" in the embodiment description refers to two or more, unless otherwise specifically defined.

[0029] The term 'embodiment' means that a particular feature, structure, or characteristic described exists in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0030] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or multiple situations existing alone. In addition, the character " / " in this document generally indicates that the related objects before and after are in an "or" relationship.

[0031] In the description of the embodiments of this application, unless otherwise expressly specified and limited, the technical terms "installation," "connection," "joining," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can also refer to a mechanical connection or an electrical connection. They can be directly connected or indirectly connected through an intermediate medium, manifesting as internal communication between two components or an interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0032] The following is in conjunction with the appendix Figures 1-4 The present invention will be described in further detail, but this is not intended to limit the scope of the present invention.

[0033] like Figure 1 and 2 As shown, the diaphragm includes a substrate 1, a heat-resistant protective coating 2, and a supporting heat-resistant coating 3. The substrate 1 has a first surface 101 along its thickness direction. The first surface 101 has a first edge region 103. The heat-resistant protective coating 2 is connected to the first surface 101. The supporting heat-resistant coating 3 is disposed on the side of the heat-resistant protective coating 2 away from the substrate 1. The supporting heat-resistant coating 3 is disposed opposite to the first edge region 103.

[0034] The technical solution of this utility model increases the edge heat resistance of the diaphragm by using the outermost supporting heat-resistant coating to reduce the risk of the diaphragm shrinking inward; and combined with the heat resistance and structural stability of the middle heat-resistant protective coating, it can further increase the stability of the main structure of the diaphragm, thereby reducing the risk of short circuit in the electrochemical device; at the same time, ensuring the diaphragm puncture strength can also help improve ED (energy density); thus improving the stability and safety of use.

[0035] Specifically, in some implementations, such as Figure 1 and2 As shown, the substrate 1 has a second surface 102 opposite to the first surface 101 along its thickness direction; the second surface 102 has a second edge region 104; and a heat-resistant supporting coating 3 is disposed on the second edge region 104 of the second surface 102. There are two first edge regions 103, located on opposite sides of the first surface 101 along its width direction, and two second edge regions 104, located on opposite sides of the second surface 102 along its width direction. That is, there are four heat-resistant supporting coatings 3, corresponding to the two second edge regions 104 of the second surface 102 and the two first edge regions 103 of the first surface 101, respectively, to support and protect the upper and lower edge regions of the diaphragm, thereby further reducing the risk of inward shrinkage of the diaphragm and thus reducing the risk of short circuit in the electrochemical device; at the same time, ensuring the diaphragm puncture strength can also help improve ED (energy density); thus improving the stability and safety of use.

[0036] Specifically, in some embodiments, the heat-resistant protective coating 2 is selected as a first ceramic coating; the supporting heat-resistant coating 3 is selected as a second ceramic coating; and the particle size of the ceramic particles in the first ceramic coating is smaller than that in the second ceramic coating. In some embodiments, the particle size D1 of the first ceramic coating satisfies: 15nm ≤ D1 ≤ 50nm; D1 can be 15nm, 16nm, 20nm, 25nm, 35nm, 45nm, 46nm, 48nm, 50nm, etc.; preferably 45nm. The particle size D2 of the second ceramic coating satisfies: 50nm ≤ D2 ≤ 200nm; D1 can be 50nm, 56nm, 60nm, 65nm, 75nm, 85nm, 100nm, 150nm, 200nm, etc.; preferably 100nm. Further, the first ceramic coating is selected from inorganic particles and organic particles; optionally, the inorganic particles include at least one of boehmite, alumina, barium sulfate, magnesium oxide, magnesium hydroxide, silicon oxide, tin dioxide, titanium oxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, nickel oxide, hafnium dioxide, cerium oxide, zirconium titanate, barium titanate, and magnesium fluoride; more preferably, the inorganic particles include one of boehmite, alumina, barium sulfate, magnesium oxide, silicon oxide, titanium oxide, zinc oxide, cerium oxide, and barium titanate; optionally, the organic particles include one of polystyrene particles, polyacrylic wax particles, melamine-formaldehyde resin particles, phenolic resin particles, polyester particles, polyimide particles, polyamide-imide particles, polyarylamide particles, polyphenylene sulfide particles, polysulfone particles, polyethersulfone particles, polyetheretherketone particles, and polyaryletherketone particles. The second ceramic coating is selected from inorganic particles and organic particles; optionally, the inorganic particles include at least one of boehmite, alumina, barium sulfate, magnesium oxide, magnesium hydroxide, silicon oxide, tin dioxide, titanium oxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, nickel oxide, hafnium dioxide, cerium oxide, zirconium titanate, barium titanate, and magnesium fluoride; more preferably, the inorganic particles include one of boehmite, alumina, barium sulfate, magnesium oxide, silicon oxide, titanium oxide, zinc oxide, cerium oxide, and barium titanate; optionally, the organic particles include one of polystyrene particles, polyacrylic wax particles, melamine-formaldehyde resin particles, phenolic resin particles, polyester particles, polyimide particles, polyamide-imide particles, polyarylamide particles, polyphenylene sulfide particles, polysulfone particles, polyetheretherketone particles, and polyaryletherketone particles.

[0037] Specifically, in some implementations, such as Figure 2As shown, the relationship between the thickness M of the heat-resistant protective coating 2 and the thickness N of the supporting heat-resistant coating 3 satisfies: 2≥N / (M+2)≥0.5; and the thickness M of the heat-resistant protective coating 2 satisfies: 1μm≤M≤2μm; the thickness N of the supporting heat-resistant coating 3 satisfies: 8μm≥N≥2μm. This structure ensures structural stability through appropriate thicknesses of the heat-resistant protective coating 2 and the supporting heat-resistant coating 3. When the thickness is too thick, it is easy to cause edge collapse. In addition, this structure can achieve a total strength limit for the diaphragm: tensile strength satisfies 8N / m≤σ≤25N / m, further reducing the risk of inward shrinkage of the diaphragm; and its puncture strength satisfies 400-700gf. Among them, the heat shrinkage rate is limited: since the diaphragm is prone to shrinkage deformation at high temperatures, the dimensional stability of the diaphragm at high temperatures can be characterized by the heat shrinkage rate. Its transverse and longitudinal heat shrinkage rates of the diaphragm at 150℃ for 1h are <3%. Where S0 is the area of ​​the diaphragm before heating, and S is the area of ​​the diaphragm after shrinkage due to heating. The calculation formula is: heat shrinkage rate = (S0-S) / S0*100%.

[0038] Specifically, in some implementations, such as Figure 3 As shown, the projection of the heat-resistant protective coating 2 toward the substrate 1 coincides with that of the substrate 1. That is, the width of the heat-resistant protective coating 2 is equal to the width of the substrate 1, and is d2; in order to achieve the heat-resistant support performance of the side surface of the substrate 1.

[0039] Specifically, in some implementations, such as Figure 2 As shown, on the same side surface of the substrate 1, there are at least two supporting heat-resistant coatings 3, and an assembly gap 201 is provided between two adjacent supporting heat-resistant coatings 3; so as to achieve a height difference between the edge and the thickness of the main body, which is conducive to electrolyte wetting and increases electrolyte retention.

[0040] Specifically, in some embodiments, the matrix 1 can be polypropylene (PP) or polyethylene (PE); and the porosity of the matrix 1 is 30% to 65%. In some embodiments, such as... Figure 2 As shown, the thickness P of the substrate 1 satisfies: 6.5um ≥ P ≥ 3.5um; it can be 3.5um, 3.6um, 3.8um, 4.0um, 4.5um, 5.5um, 6.5um, etc.; preferably 4.5um. This structure effectively achieves a puncture strength range of 300-700gf and a tensile strength of 200-400MPa for the substrate 1, thereby improving its stability and safety in use. In addition, this structure can also achieve an air permeability of ≤250s / 100mL and a breakdown voltage greater than 1.5KV for the separator.

[0041] Specifically, in some implementations, such as Figure 2As shown, an adhesive coating 41 is provided between the supporting heat-resistant coating 3 and the heat-resistant protective coating 2; and the supporting heat-resistant coating 3 covers and is connected to the side surface of the adhesive coating 41; the adhesive coating 41 is connected to the heat-resistant protective coating 2. The adhesive coating 41 can be one or more of the following structures: polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), ethyl polyacrylate (PEA), polyvinyl alcohol (PVA), polyurethane (PU), sodium dodecyl sulfonate (DLSS), sodium carboxymethyl cellulose, and styrene-butadiene rubber, in a multilayered coating structure.

[0042] This utility model also proposes a battery cell, such as Figure 4 As shown, the battery cell includes a separator 400 and an electrode body 500. The electrode body 500 includes a first electrode and a second electrode with opposite polarities. Each of the first and second electrodes has a corresponding tab 510. The separator 400 is disposed between the first and second electrodes. The first electrode, separator, and second electrode are stacked and wound together to form a wound body. The specific structure of the separator 400 is as described in the above embodiments. Since this battery cell adopts all the technical solutions of all the above embodiments, it possesses at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated further here. Specifically, when the first electrode is a positive electrode, the second electrode is a negative electrode. When the first electrode is a negative electrode, the second electrode is a positive electrode.

[0043] Specifically, in some implementations, such as Figure 3 and 4 As shown, the battery cell has a first end and a second end along its length, with the first end and the second end positioned opposite each other. At the first end, the separator 400 extends beyond the electrode body 500 by a dimension d3, and the supporting heat-resistant coating 3 extends by a dimension d1, satisfying the condition: 65% * d3 ≤ d1 ≤ 95% * d3. The possible values ​​are: 65% * d3 = d1, 70% * d3 = d1, 75% * d3 = d1, 80% * d3 = d1, 85% * d3 = d1, 90% * d3 = d1, 95% * d3 = d1, etc.; preferably, 65% * d3 = d1. This structure, through the appropriate difference between the width of the supporting heat-resistant coating 3 and the width difference between the separator 400 and the electrode body 500, ensures the stability of the overall structure and increases the heat resistance of the separator edge, reducing the risk of the separator shrinking inward, thereby reducing the risk of short circuits in the electrochemical device. Simultaneously, it ensures the puncture strength of the separator, reduces the thickness of the battery cell body, and improves the ED (exposure potential).

[0044] Specifically, in some implementations, such as Figure 4As shown, d3 satisfies: 1.5mm ≤ d3 ≤ 3mm; d3 can be 1.5mm, 1.8mm, 2.0mm, 2.5mm, 2.6mm, 2.8mm, 3.0mm, etc.; preferably 2.0mm. This structure can ensure the stability of the overall structure through a suitable width difference between the separator 400 and the electrode body 500, and can also help avoid the thickness of the battery cell body.

[0045] The positive electrode includes a positive current collector and a positive active material layer, with the positive active material layer coated on the surface of the positive current collector. The positive current collector includes a positive coating area and a positive electrode tab connected to the positive coating area. The positive coating area is coated with the positive active material layer, while the positive electrode tab is not coated with the positive active material layer. Taking a lithium-ion battery as an example, the material of the positive current collector can be aluminum, and the positive active material layer includes positive active material, which can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide, etc. The negative electrode includes a negative current collector and a negative active material layer, with the negative active material layer coated on the surface of the negative current collector. The negative current collector includes a negative coating area and a negative electrode tab connected to the negative coating area. The negative coating area is coated with the negative active material layer, while the negative electrode tab is not coated with the negative active material layer. The material of the negative current collector can be copper, and the negative active material layer includes negative active material, which can be carbon or silicon, etc.

[0046] This utility model also proposes a secondary battery, which includes a battery cell. The specific structure of the battery cell is as described in the above embodiments. Since this secondary battery adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be described in detail here.

[0047] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style of the specification is merely for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0048] Based on the disclosure and teachings of the above specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, this utility model is not limited to the specific embodiments described above, and any obvious improvements, substitutions, or modifications made by those skilled in the art based on this utility model are within the protection scope of this utility model. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on this utility model.

Claims

1. A diaphragm, characterized in that: Includes the substrate, heat-resistant protective coating, and supporting heat-resistant coating; The substrate has a first surface along the thickness direction; the first surface has a first edge region; the heat-resistant protective coating is connected to the first surface; The supporting heat-resistant coating is disposed on the surface of the heat-resistant protective coating away from the substrate; Furthermore, the supporting heat-resistant coating is disposed opposite to the first edge region.

2. The diaphragm according to claim 1, characterized in that: The substrate has a second surface opposite to the first surface along its thickness direction; the second surface has a second edge region; the supporting heat-resistant coating is disposed on the second edge region of the second surface.

3. The diaphragm according to claim 2, characterized in that: The first edge region is provided in two parts, and the two first edge regions are respectively located on both sides of the first surface of the substrate along its width direction. The second edge region is provided in two parts, and the two second edge regions are respectively located on both sides of the second surface of the substrate along its width direction.

4. The diaphragm according to claim 1, characterized in that: The heat-resistant protective coating is selected from the first ceramic coating. The supporting heat-resistant coating is a second ceramic coating; and the particle size of the ceramic particles in the first ceramic coating is smaller than that in the second ceramic coating.

5. The diaphragm according to claim 1 or 4, characterized in that: The relationship between the thickness M of the heat-resistant protective coating and the thickness N of the supporting heat-resistant coating satisfies: 0.5≤N / (M+2)≤2; And / or the thickness M of the heat-resistant protective coating satisfies: 1μm≤M≤2μm; And / or the thickness N of the supporting heat-resistant coating satisfies: 2μm≤N≤8μm.

6. The diaphragm according to any one of claims 1 to 4, characterized in that: On the same side surface of the substrate, there are at least two supporting heat-resistant coatings, and an assembly gap is provided between two adjacent supporting heat-resistant coatings.

7. The diaphragm according to claim 1, characterized in that: The matrix is ​​selected from polypropylene or polyethylene; Furthermore, the porosity of the matrix is ​​30% to 65%; and / or the thickness P of the matrix satisfies: 3.5 μm ≤ P ≤ 6.5 μm.

8. The diaphragm according to claim 1, characterized in that: An adhesive coating is provided between the supporting heat-resistant coating and the heat-resistant protective coating; and the supporting heat-resistant coating covers and is connected to the side surface of the adhesive coating; the adhesive coating is connected to the heat-resistant protective coating.

9. A battery cell, characterized in that: The device includes a separator and an electrode body, wherein the electrode body includes a first electrode and a second electrode with opposite polarities; the separator is disposed between the first electrode and the second electrode, and the first electrode, the separator, and the second electrode are stacked and wound together to form a wound body; and the separator is the separator as described in any one of claims 1 to 8. The battery cell has a first end and a second end along its length, with the first end and the second end disposed opposite to each other. At the first end, the separator extends beyond the electrode body by a dimension d3, and the supporting heat-resistant coating has a dimension d1, satisfying: 65%*d3≤d1≤95%*d3; and / or d3 satisfies: 1.5mm≤d3≤3mm.

10. A secondary battery, characterized in that: Includes the battery cell described in claim 9.

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