A separator and a battery

Abstract

This invention relates to the field of battery technology, specifically to a separator and a battery including the separator. The separator includes a substrate layer and an organic coating located on one or both surfaces of the substrate layer. The organic coating includes organic particles, the composition of which includes nitrogen-containing organic compounds. The molecular structure of the nitrogen-containing organic compounds includes nitrogen-containing heterocycles, and the average aspect ratio of the organic particles is 1-3. The separator of this invention has high electrolyte wettability, promotes uniform lithium-ion transport, reduces the risk of lithium dendrite formation, thereby delaying lithium plating and extending the fast-charge cycle life of the battery. Simultaneously, the separator of this invention can also improve the problem of increased risk of separator puncture due to localized stress concentration, providing a certain buffering effect on the pressure exerted on the separator by the active particles of the positive and negative electrodes and / or the tips of lithium dendrites, thereby reducing the risk of separator puncture and the risk of micro-short circuits in the battery.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically to a separator and a battery including the separator. Background Technology

[0002] Traditional graphite anodes are limited by their inherently low theoretical capacity, making it difficult to meet the ever-increasing demand for high-performance energy storage. The low inherent theoretical capacity of widely used graphite anode materials has become a bottleneck restricting batteries from meeting higher energy storage requirements. Against this backdrop, silicon materials have attracted significant attention due to their much higher theoretical specific capacity than graphite and their suitable lithium intercalation potential.

[0003] However, silicon materials undergo significant volume expansion and contraction during charging and discharging. This repeated and drastic volume change exposes the separator to prolonged exposure to substantial mechanical stress. During high-rate charging and discharging, the squeezing action at the sharp points of silicon particles and the growth of lithium dendrites significantly increase the risk of separator puncture, creating micro-short circuits within the battery. This further amplifies self-discharge, potentially leading to safety issues in severe cases.

[0004] Therefore, it is very important to invent a battery that can improve the micro-short circuit of silicon-based anode systems. Summary of the Invention

[0005] In silicon anode batteries, the repeated expansion and contraction of silicon particles during battery cycling causes repeated rupture and regeneration of the SEI film, resulting in high electrolyte consumption and the formation of a thick and uneven SEI film. Furthermore, the accumulated stress from these volume changes and the rupture of silicon particles easily lead to the detachment of anode active particles from the current collector. During high-rate charging and discharging, the increased rate of lithium-ion insertion and extraction further exacerbates the breakage of silicon particles. These broken anode active particles can compress and puncture the separator, creating micro-short circuits and increasing the risk of cell safety issues. Additionally, the surface of the anode sheet becomes rough after powder shedding, making the lithium-ion diffusion path more distorted and complex, affecting electrolyte flow, increasing internal resistance, intensifying polarization, increasing the risk of lithium plating, and significantly increasing the probability of lithium dendrites puncturing the separator.

[0006] For wound lithium-ion batteries, the electrodes bend at the arcs during charge-discharge cycles. At the innermost bend, the excessive bending can cause cracks or even detachment of the active material layer, leading to greater compression of the separator by the active particles. Simultaneously, when powder is shed from both the positive and negative electrodes, the capacity ratio between the negative and positive electrodes at the arcs becomes mismatched, exacerbating lithium plating. The deposited lithium dendrites pierce the separator, creating micro-short circuits, increasing battery self-discharge, accelerating cycle life degradation, and posing a safety challenge.

[0007] To address the increased risk of separator puncture in existing technologies due to volume changes in silicon-based materials, extrusion or detachment of active particles, and lithium dendrite formation, this invention provides a separator and a battery including the separator. The separator of this invention exhibits high electrolyte wettability, promoting uniform lithium-ion transport and reducing the risk of lithium dendrite formation, thereby delaying lithium plating and extending the battery's fast-charge cycle life. Furthermore, the separator of this invention mitigates the increased risk of separator puncture caused by localized stress concentration, providing a buffering effect on the tips of active particles and / or lithium dendrites, thus reducing the risk of separator puncture and minimizing the risk of micro-short circuits in the battery.

[0008] To achieve the above objectives, a first aspect of the present invention provides a diaphragm comprising a substrate layer and an organic coating located on one or both surfaces of the substrate layer. The organic coating comprises organic particles, the organic particles comprising nitrogen-containing organic compounds. The nitrogen-containing organic compounds include one or more of the following: uracil, 4,6-dimethyl-2-phenylpyrimidine, cytosine, 2,4-dimercaptopyrimidine, 2,4-dimercapto-5,6-diaminopyrimidine, 4-amino-2,6-dihydroxypyrimidine, 2-mercaptobenzimidazole, melamine cyanurate, melamine thiocyanate, polypyrrole, and sulfonated polytriazole. The molecular structure of the nitrogen-containing organic compounds comprises nitrogen-containing heterocycles, and the average aspect ratio of the organic particles is 1-3.

[0009] A second aspect of the present invention provides a battery comprising a positive electrode, a negative electrode, and a separator as described in the first aspect of the present invention, the separator being located between the positive electrode and the negative electrode, the positive electrode comprising a positive current collector and a positive active layer located on one or both surfaces of the positive current collector.

[0010] By employing the above technical solution, the present invention has at least the following advantages compared with the prior art:

[0011] The diaphragm of the present invention comprises organic particles, the components of which include nitrogen-containing organic compounds. These nitrogen-containing organic compounds include one or more of the following: uracil, 4,6-dimethyl-2-phenylpyrimidine, cytosine, 2,4-dimercaptopyrimidine, 2,4-dimercapto-5,6-diaminopyrimidine, 4-amino-2,6-dihydroxypyrimidine, 2-mercaptobenzimidazole, melamine cyanurate, melamine thiocyanate, polypyrrole, and sulfonated polytriazole. The molecular structure of the nitrogen-containing organic compounds includes nitrogen-containing heterocycles, wherein the nitrogen-containing heterocycles contain nitrogen-containing heterocycles. The lone pairs of electrons can influence the rearrangement of the electron cloud, lower the energy barrier, and increase the transport rate of lithium ions. Furthermore, nitrogen-containing heterocycles can improve the electrolyte wettability of the separator, reducing or even inhibiting the formation of lithium dendrites. Simultaneously, nitrogen-containing organic materials have lower hardness; when the separator is subjected to localized compressive stress (e.g., pressure from lithium dendrite tips or the edges of active particles), the stress effect of the organic particles on the separator is reduced, effectively lowering the risk of separator puncture. This reduces the risk of micro-short circuits in the battery and extends the fast-charge cycle life. Therefore, the separator of this invention can reduce or even inhibit the formation of lithium dendrites and has a certain stress buffering effect, reducing the risk of separator puncture, reducing the risk of battery short circuits, and extending the fast-charge cycle life of the battery.

[0012] Meanwhile, the separator of the present invention also controls the average aspect ratio of organic particles to form a more stable and dense coating on the organic coating of the separator, which further improves the puncture resistance of the separator, further reduces the risk of short circuit of the separator, and can also improve the smoothness of the surface of the organic coating, making the electrolyte distribution more uniform, further reducing or even inhibiting the formation of lithium dendrites, and further extending the fast charge cycle life of the battery.

[0013] In summary, the separator of the present invention can reduce or even inhibit the formation of lithium dendrites, while also having a certain stress buffering effect, reducing the risk of puncture, thereby enabling the battery to have both a lower risk of internal short circuit and a longer fast charge cycle life.

[0014] Other features and advantages of the present invention will be described in detail in the following detailed description section.

[0015] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. Attached Figure Description

[0016] Figure 1 The diagram shown is a schematic representation of the diaphragm structure of the present invention.

[0017] Figure 2 The diagram shows the first and second surfaces of the organic coating in the diaphragm of the present invention.

[0018] Figure 3 The diagram shown is one of the schematic diagrams of the striped coating area in the adhesive layer of the diaphragm of the present invention.

[0019] Figure 4 The diagram shown is a second schematic of the striped coating area in the adhesive layer of the diaphragm of the present invention.

[0020] Figure 5 The diagram shown is a third schematic of the striped coating area in the adhesive layer of the diaphragm of the present invention.

[0021] Figure 6 The image shown is a SEM image of the organic coating in the diaphragm of the present invention. Detailed Implementation

[0022] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the invention. Unless otherwise specified herein, data ranges include endpoints.

[0023] It should be noted that the numerical designations such as "first" and "second" in this invention are only used to distinguish different substances or methods of use, and do not represent a difference in order.

[0024] A first aspect of the present invention provides a diaphragm comprising a substrate layer and an organic coating located on one or both surfaces of the substrate layer. The organic coating comprises organic particles, the organic particles comprising a nitrogen-containing organic compound. The nitrogen-containing organic compound comprises one or more of uracil, 4,6-dimethyl-2-phenylpyrimidine, cytosine, 2,4-dimercaptopyrimidine, 2,4-dimercapto-5,6-diaminopyrimidine, 4-amino-2,6-dihydroxypyrimidine, 2-mercaptobenzimidazole, melamine cyanurate, melamine thiocyanate, polypyrrole, and sulfonated polytriazole. The molecular structure of the nitrogen-containing organic compound comprises a nitrogen-containing heterocycle. The average aspect ratio of the organic particles is 1-3 (e.g., 1, 1.3, 1.5, 1.8, 2, 2.3, 2.5, 2.8, or 3).

[0025] like Figure 1 and Figure 2 As shown, the diaphragm 1 includes a substrate layer 11 and an organic coating 12 located on one or both sides of the substrate layer 11.

[0026] The membrane of the present invention comprises organic particles (such as...) Figure 6As shown), the organic particles contain nitrogen-containing organic compounds. These compounds not only reduce or even inhibit the formation of lithium dendrites on the membrane surface but also reduce the local stress on the membrane, thereby reducing the risk of membrane puncture and consequently the risk of battery short circuit. Specifically, on the one hand, the molecular structure of the nitrogen-containing organic compounds includes nitrogen-containing heterocycles. The nitrogen atoms in these heterocycles possess lone pairs of electrons, which can influence the rearrangement of the electron cloud, lower the energy barrier, and increase the lithium-ion transport rate. Simultaneously, the nitrogen-containing heterocycles also exhibit good electrolyte affinity, aiding in… On the one hand, it improves the electrolyte wettability of the separator, further enhances lithium-ion transport, reduces or even inhibits the formation of lithium dendrites on the separator surface, and improves the fast-charging cycle life of the battery. On the other hand, nitrogen-containing organic materials have low hardness. When the separator containing nitrogen-containing organic materials is subjected to local pressure (such as being pressed by the tip of lithium dendrites or the edge of active particles), it can absorb some of the impact energy, play a certain stress buffering role, reduce the effect of local stress on the separator, reduce the risk of the separator being punctured, thereby reducing the risk of micro-short circuits in the battery and extending the fast-charging cycle life of the battery.

[0027] To further reduce the risk of membrane puncture, the membrane of this invention also controls the average aspect ratio of the organic particles. By controlling the average aspect ratio of the organic particles to 1-3, on the one hand, organic particles with the above-mentioned average aspect ratio can accumulate in the organic coating and form a highly dense organic coating. This allows the organic particles to maintain the structural stability of the organic coating even when the membrane is subjected to local compressive stress, reducing or even avoiding the risk of organic particles falling off or breaking from the organic coating, further improving the puncture resistance of the membrane, reducing or even preventing lithium dendrites from penetrating the membrane, and further reducing the risk of short circuits in the membrane. On the other hand, organic particles with the above-mentioned average aspect ratio can make the surface of the organic coating smoother and the electrolyte distribution more uniform, thereby reducing the contact resistance between the membrane and the electrode, improving the uniformity of the current density distribution on the electrode surface, promoting uniform lithium deposition, thereby delaying lithium plating, further reducing the risk of lithium dendrite formation, and further improving the fast-charging cycle life of the battery.

[0028] In this invention, the average aspect ratio of the organic particles can be obtained by testing using the following method: The surface of the organic coating is observed using a scanning electron microscope at 10,000x magnification to identify the organic particles within the field of view, and the outlines of the organic particles are identified using ImageJ image processing software. The longest side of the smallest rectangle tangent to the organic particles is L. 1 The short side of the smallest rectangle tangent to the organic particles is W. 1 Then the aspect ratio A of the organic particles 1 =L 1 / W 1(Where, when the smallest rectangle tangent to the organic particles is a square, the aspect ratio of the organic particles is 1). Randomly measure the aspect ratio of 100 organic particles and take the average value as the average aspect ratio. It can be understood that when there are fewer than 100 organic particles in the field of view, the average aspect ratio of the total 100 organic particles can be set as the average aspect ratio by observing the surface of the organic particles multiple times.

[0029] In this invention, by incorporating organic particles containing nitrogen-containing organic compounds with nitrogen-containing heterocyclic rings into the separator, and simultaneously controlling the average aspect ratio of the organic particles, the risk of separator puncture and battery short circuit can be reduced compared to existing technologies, while also extending the battery's fast-charging cycle life. To further improve the effect, one or more of the technical features can be further optimized.

[0030] In some instances, the morphology of the organic particles includes one or more of the following: blocky, rod-shaped, flake-shaped, stacked, spherical, and spherical.

[0031] In some instances, the organic particles have a layered crystal structure.

[0032] In some instances, the nitrogen-containing organic compounds include one or more of 4-amino-2,6-dihydroxypyrimidine, 2-mercaptobenzimidazole, melamine cyanurate, and melamine thiocyanate. While these substances are more effective at inhibiting dendrite growth, the inventors of this invention have found that when their aspect ratio is large, physical self-discharge is exacerbated when applied to wound batteries, especially high-energy-density and silicon-based wound batteries. The inventors speculate that a possible reason is that although the lone pairs of nitrogen atoms in the nitrogen-containing heterocycles of these substances affect electron cloud rearrangement, lower the energy barrier, and optimize interfacial ion transport, thus inhibiting dendrite growth and preventing dendrites from piercing the separator and causing short circuits, the organic particles containing the aforementioned nitrogen-containing organic compounds have a layered crystal structure, with interlayer forces mainly consisting of weak hydrogen bonds and van der Waals forces. When the battery is cycled... When the ring expands, the bending area of ​​the core is subjected to greater compressive stress. This layered crystal structure is prone to relative sliding between layers, making it easy for organic particles to shift or even fall off when compressed, creating weak areas. Furthermore, organic particles with a large average aspect ratio are more prone to breakage, increasing the risk of the membrane being punctured by active particles or foreign objects in these weak areas. The membrane of this invention also controls the average aspect ratio of the organic particles to 1-3, making the organic particles less prone to breakage and more compactly packed. The organic particles are less likely to fall off under stress, improving the overall structural stability of the organic coating, thereby reducing the risk of weak areas forming in the membrane and reducing the risk of the membrane being punctured.

[0033] In some instances, the number of organic particles with an aspect ratio greater than 10 within an area optionally 20 μm × 20 μm on the surface of the organic coating is denoted as N.1 1, N 1 ≤20 (e.g., 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, or 0). Control N 1 ≤20. Organic particles with a larger aspect ratio have a relatively finer and longer shape, making them more prone to breakage under stress. When the aforementioned range is met, the organic particles on the surface of the organic coating can be more densely packed, and the probability of particle breakage under stress can be reduced, further improving the puncture resistance of the separator, further reducing or even avoiding the separator being punctured, and reducing the risk of internal short circuit in the battery.

[0034] In some instances, the diaphragm satisfies the following relationship: N 2 <N 3 , where N 2 In the thickness direction of the diaphragm, the surface of the organic coating furthest from the substrate layer is designated as the first surface. The number of organic particles with an aspect ratio greater than 10 on the first surface is expressed in units of N. 3 In the thickness direction of the diaphragm, the surface of the organic coating closest to the substrate layer is designated as a second surface. The number of organic particles with an aspect ratio greater than 10 on this second surface is measured in individual particles. The diaphragm is controlled to satisfy N... 2 <N 3 On the one hand, the organic coating contains a larger number of organic particles with an aspect ratio greater than 10 on the side closer to the substrate layer. This results in a looser packing density of organic particles on this side, providing more storage space for the electrolyte, improving the wetting and storage of the electrolyte on the substrate layer surface, and further enhancing the battery's cycle performance. On the other hand, the organic coating contains a smaller number of organic particles with an aspect ratio greater than 10 on the side farther from the substrate layer. This results in a denser and more stable packing of organic particles, which further improves the separator's resistance to lithium dendrites and foreign object puncture, and further reduces the risk of internal short circuits in the battery.

[0035] In some instances, the number of organic particles with an aspect ratio greater than 10 in the organic coating exhibits a gradient change along the thickness direction of the diaphragm. In this invention, the gradient change in the number of organic particles with an aspect ratio greater than 10 in the organic coating along the thickness direction of the diaphragm can be determined by the following method: the surface at 1 / 2 of the thickness of the organic coating is the third surface, and the number of organic particles with an aspect ratio greater than 10 in the organic coating on the third surface is N. 4 The number of organic particles with an aspect ratio greater than 10 on the first, second, and third surfaces was measured and denoted as N. 3 N 4 and N 2 If N is satisfied 2 <N4 <N 3 This indicates that, along the thickness direction of the membrane, the number of organic particles with an aspect ratio greater than 10 in the organic coating exhibits a gradient change. If N is not satisfied... 2 <N 4 <N 3 This indicates a non-gradient change in the number of organic particles with an aspect ratio greater than 10 in the organic coating along the thickness direction of the diaphragm. The third surface, located at half the thickness of the organic coating, can be obtained by tearing the organic coating at this point. For example... Figure 2 As shown, in the thickness direction X of the diaphragm 1, the surface of the organic coating 12 away from the substrate layer 11 is the first surface 121, the surface of the organic coating 12 close to the substrate layer 11 is the second surface 122, and the surface at 1 / 2 of the thickness of the organic coating 12 is the third surface 123.

[0036] In some instances, the organic coating also includes a first adhesive.

[0037] In some instances, the first adhesive comprises one or more of polyvinyl alcohol, styrene-butadiene rubber, ethylene-vinyl acetate copolymer, sodium carboxymethyl cellulose, polyvinylpyrrolidone, acrylate adhesives, styrene-acrylic latex, polyacrylonitrile, polyvinyl acetate, polyurethane, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, or copolymer systems derived from the above polymers.

[0038] In this invention, the acrylate adhesive includes one or more of the following: polymethyl methacrylate, polyethylhexyl acrylate, polybutyl acrylate, acrylate monomer-acrylonitrile copolymer, acrylate monomer-acrylonitrile-ethylene copolymer, styrene-acrylate monomer-acrylonitrile copolymer, acrylate monomer-styrene copolymer, acrylate monomer-ethylene copolymer, ethylhexyl acrylate-methyl methacrylate copolymer, butyl acrylate-methyl methacrylate copolymer, methyl acrylate-N,N-dimethylacrylamide copolymer, ethyl acrylate-2-(diethylamino)ethyl acrylate copolymer, ethyl acrylate-N,N-diethylacrylamide copolymer, and ethyl acrylate-2-(diethylamino)ethyl acrylate.

[0039] In some instances, the organic particles comprise 90%-99% of the total weight of the organic coating (e.g., 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%), and the first adhesive comprises 1%-10% of the total weight of the organic coating (e.g., 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%).

[0040] In some instances, the thickness of the organic coating is 0.2 μm to 5 μm (e.g., 0.2 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm or 5 μm).

[0041] In some instances, the substrate layer is a three-dimensional porous mesh structure composed of interwoven fibers. The pores in the three-dimensional porous mesh structure are distributed within an intricately interwoven fiber skeleton.

[0042] In some examples, the average diameter of the fibers is 0.02 μm-0.45 μm (e.g., 0.02 μm, 0.05 μm, 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm, or 0.45 μm). The fibers act as a supporting porous framework. Controlling the average fiber diameter within this range allows for a uniform distribution of contact sites on the surface of the organic coating on the substrate layer, enhancing the adhesion between the organic coating and the substrate layer. However, when the average fiber diameter is greater than 0.45 μm, it leads to a reduction in pore distribution and poor consistency within a smaller area, affecting the interface consistency of the substrate layer and hindering lithium-ion transport. When the average fiber diameter is less than 0.02 μm, the locking effect on organic particles is poor, making organic particles prone to detachment, and the insufficient support of the fiber framework increases the risk of membrane puncture.

[0043] The average diameter of the fiber can be obtained by the following method: Using SEM to obtain a microscopic image of the substrate surface, arbitrarily select a 20μm × 20μm area on the substrate surface, and measure the diameter of any 20 fibers within this area. Take the average of these measurements as the average diameter. Repeat this test 5 times, and take the average of the 5 test results as the average fiber diameter. It can be understood that if there are fewer than 20 fibers in the area, multiple 20μm × 20μm areas can be selected, and the average diameter of the total 20 fibers can be taken as the average diameter. Here, the fiber diameter refers to the diameter of a single fiber. Along the length of the fiber, select 5 points at equal intervals, and measure the fiber diameter at each of the 5 points. The average of the fiber diameters at these 5 points is the diameter of the fiber.

[0044] In some instances, the puncture strength of the substrate layer is 200gf-600gf (200gf, 230gf, 250gf, 300gf, 350gf, 400gf, 450gf, 500gf, 550gf or 600gf).

[0045] In some instances, the puncture strength of the substrate layer is 280 gf-450 gf.

[0046] In this invention, the puncture strength of the substrate layer can be measured by the following method: disassemble the battery, remove the separator, remove the coating on the surface of the substrate layer, and when the coating residue on the surface of the substrate layer is less than 5%, it is considered as obtaining a test sample of the substrate layer. Alternatively, the original substrate layer without coating can be used as a test sample. A test sample of 50mm×50mm is cut arbitrarily from the test sample. The test sample is laid flat in the fixture of the universal tensile testing machine and clamped. The puncture strength test item is selected, and puncture is performed at a rate of (100±10)mm / min. The puncture strength test result is read from the test report. The test is repeated 3 times and the average value is taken as the puncture strength of the substrate layer.

[0047] In some instances, the thickness of the substrate layer is 3.5 μm to 16 μm (e.g., 3.5 μm, 4 μm, 6 μm, 8 μm, 10 μm, 12 μm, 14 μm or 16 μm).

[0048] In some instances, the thickness of the substrate layer is 4 μm-7 μm.

[0049] In some instances, the average pore size of the substrate layer is 30nm-50nm (e.g., 30nm, 33nm, 35nm, 38nm, 40nm, 43nm, 45nm, 48nm or 50nm).

[0050] In this invention, the average pore size of the substrate layer can be measured by the following method: disassemble the battery, remove the separator, remove the coating on the surface of the substrate layer, and when the coating residue on the surface of the substrate layer is less than 5%, it is considered as obtaining a test sample. Alternatively, the original substrate layer without coating can be used as a test sample. The test sample is tested using a PMI LLP-1200 pore size analyzer. The test sample is cut into a circle with a diameter of 10 mm and fully wetted with deionized water. The wetted test sample is placed in the instrument's sample stage, and the test is started through software. The system software automatically analyzes the data and calculates the average pore size of the test sample.

[0051] In some instances, the porosity of the substrate layer is 25%-45% (e.g., 25%, 28%, 30%, 33%, 35%, 38%, 40%, 43% or 45%).

[0052] In this invention, the porosity of the substrate layer is measured by the following method: the battery is disassembled, the separator is removed, and the coating on the surface of the substrate layer is removed. When the residual amount of coating on the surface of the substrate layer is less than 5%, it is considered as obtaining a test sample of the substrate layer. Alternatively, the original substrate layer without coating is used as a test sample. The test sample is tested in accordance with the standard "GB / T-36363-2018 Polyolefin Separator for Lithium-ion Batteries" to obtain the porosity of the substrate layer.

[0053] According to one specific embodiment, the puncture strength of the substrate layer is 200gf-600gf, the thickness of the substrate layer is 3.5μm-16μm, the average pore size of the substrate layer is 30nm-50nm, and the porosity of the substrate layer is 25%-45%. Controlling the puncture strength, thickness, average pore size, and porosity of the substrate layer within the above ranges can further improve the puncture resistance of the separator, further reduce the risk of separator puncture, and further reduce the risk of internal short circuits in the battery. When the separator thickness exceeds 16μm, the loss in battery energy density is too large. When the puncture strength of the separator exceeds 600gf, the separator cannot maintain a low pore-closing temperature, affecting the high-temperature safety performance of the battery.

[0054] According to one specific embodiment, the puncture strength of the substrate layer is 280gf-450gf, the thickness of the substrate layer is 4μm-7μm, the average pore size of the substrate layer is 30nm-50nm, and the porosity of the substrate layer is 25%-45%.

[0055] In some instances, the substrate layer comprises one or more of the following polymer derivatives: polyolefin, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinyl chloride, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyetherimide, polyethylene terephthalate, polybutylene terephthalate, poly(p-phenylene terephthalamide), poly(m-phenylene isophthalamide), polybenzimidazole, polysulfone, polyketone, or the above polymer derivatives.

[0056] In some instances, the polyolefin includes at least one of polyethylene, modified polyethylene, polypropylene, and modified polypropylene.

[0057] In some instances, such as Figure 1 As shown, the diaphragm 1 includes a carrier layer 21 and an adhesive layer 13 located on one or both sides of the carrier layer 21. The carrier layer 21 includes a substrate layer 11 and an organic coating 12 located on one or both sides of the substrate layer 11.

[0058] In some instances, the diaphragm includes a substrate layer, an organic coating, and an adhesive layer, wherein the organic coating is located on one side surface of the substrate layer, and the adhesive layer is located on the surface of the organic coating and the other side surface of the substrate layer.

[0059] In some instances, the diaphragm includes a substrate layer, an organic coating, and an adhesive layer, wherein the organic coating is located on one side surface of the substrate layer and the adhesive layer is located on the other side surface of the substrate layer.

[0060] In some instances, the diaphragm includes a substrate layer, an organic coating, and an adhesive layer, wherein the organic coating is located on both sides of the substrate layer, and the adhesive layer is located on the surface of the organic coating on either side.

[0061] In some instances, the diaphragm includes a substrate layer, an organic coating, and an adhesive layer, wherein the organic coating is located on both sides of the substrate layer, and the adhesive layer is located on the surfaces of the organic coating on both sides.

[0062] In some instances, the coverage of the adhesive layer on the surface of the carrier layer is 15%-97% (e.g., 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 97%). Controlling the coverage of the adhesive layer on the surface of the carrier layer within the above range ensures good adhesion and good interfacial contact between the diaphragm and the electrode.

[0063] In some instances, the coverage of the adhesive layer on the surface of the carrier layer is 18%-60%.

[0064] In this invention, the coverage rate of the adhesive layer on the carrier layer surface refers to the ratio of the projected area of ​​the adhesive layer on one side of the carrier layer surface to the total area of ​​the carrier layer surface on that side. It is understood that when the adhesive layer is located on both sides of the carrier layer surface, the coverage rates of the adhesive layers on both sides can be the same or different; the coverage rate refers to the coverage rate of the adhesive layer on either side. The coverage rate of the adhesive layer on the carrier layer surface can be tested using the following method: Take a 6cm × 6cm diaphragm sample, stain and penetrate the diaphragm with dye penetrant DPT-5 in a fume hood, and after the membrane surface dries, remove the diaphragm sample and observe it under a 3D ultra-depth-of-field microscope. Adjust the magnification to 50X and use the system software to automatically measure the area (particle counting), thus obtaining the adhesive layer coverage rate. The equipment model is Keyence VHX 6000. Repeat the above operation 5 times, and take the average of the 5 measurements as the coverage rate of the adhesive layer on the carrier layer surface.

[0065] In some instances, the coating layer comprises polymer particles, the polymer particles comprising a first polymer, the first polymer comprising one or more of the following: fluoropolymers, acrylate polymers, polyimides, phenolic resins, poly(p-phenylene terephthalamide), poly(m-phenylene isophthalamide), bio-based aramid, polyethylene, modified polyethylene, polypropylene, modified polypropylene, and styrene-butadiene rubber.

[0066] In this invention, the fluoropolymer includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyvinylidene fluoride, polyhexafluoropropylene, polyvinylidene fluoride-trichloroethylene, polyvinylidene fluoride-chlorotrifluoroethylene, fluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and copolymers thereof.

[0067] In this invention, the acrylate polymers include one or more of the following: polymethyl methacrylate, polyethylhexyl acrylate, polybutyl acrylate, acrylate monomer-acrylonitrile copolymer, acrylate monomer-acrylonitrile-ethylene copolymer, styrene-acrylate monomer-acrylonitrile copolymer, acrylate monomer-styrene copolymer, acrylate monomer-ethylene copolymer, ethylhexyl acrylate-methyl methacrylate copolymer, butyl acrylate-methyl methacrylate copolymer, methyl acrylate-N,N-dimethylacrylamide copolymer, ethyl acrylate-2-(diethylamino)ethyl acrylate copolymer, ethyl acrylate-N,N-diethylacrylamide copolymer, and ethyl acrylate-2-(diethylamino)ethyl acrylate.

[0068] In this invention, the acrylate monomers include one or more of methyl acrylate, methyl methacrylate, ethyl acrylate, butyl acrylate, and ethyl methacrylate.

[0069] In this invention, the bio-based aramid has a structure as shown in formula (I). Equation (I), where m is an integer from 5 to 100 (e.g., 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100), n is an integer from 5 to 100 (e.g., 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100), and Ar1 is selected from... and Ar2 is selected from one or more of the following groups: , , , , , , , , , , , , , , , and .

[0070] In some examples where the adhesive layer includes polymer particles, the average particle size of the polymer particles is 0.1 μm-20 μm (e.g., 0.1 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, or 20 μm). Controlling the average particle size of the polymer particles within the above range can increase the gap between the separator and the electrode (the positive and negative electrodes are collectively referred to as "electrodes") while ensuring the adhesion of the adhesive layer, reducing the risk of separator puncture. When the average particle size of the polymer particles is less than 0.1 μm, it will result in insufficient adhesion between the separator and the electrode, affecting the cycle performance of the battery. When the average particle size of the polymer particles is higher than 20 μm, it will cause the distance between the separator and the electrode to be too large and excessive, which will prevent the electrolyte from being effectively filled after it is consumed, increase the lithium-ion transport path, and affect the battery cycle performance and rate performance.

[0071] The average particle size of the polymer particles can be tested using the following method: On an image obtained by observing the surface of the coating layer using SEM, draw the smallest square or rectangle that completely surrounds one polymer particle. That is, draw a square or rectangle where the edge of the polymer particle meets all four sides of the square or rectangle. The length of one side of the square or the length of the long side of the rectangle is the particle size. Measure the particle size of any 100 polymer particles on the coating layer surface and average the results. Repeat this process five times and take the average value. It should be noted that if no 100 polymer particles are observed in the image, take multiple images and average the total number of particle sizes for the 100 polymer particles. It is understood that when the coating layer contains both non-agglomerated and agglomerated polymer particles, the average particle size is the average of the average particle sizes of the non-agglomerated and agglomerated polymer particles. Non-agglomerated polymer particles refer to polymer particles that are dispersed in the coating layer. In the thickness direction of the membrane, non-agglomerated polymer particles are dispersed in the coating layer, with only one layer or multiple layers, and no large-size agglomerates appear.

[0072] In some instances, the polymer particles may include at least one of a first polymer particle and a second polymer particle, wherein the first polymer particle is an aggregated polymer particle and the second polymer particle is a non-aggregated polymer particle.

[0073] In this invention, the first polymer particle includes secondary particles formed by the agglomeration of primary particles, wherein the average particle size of the primary particles is 0.15 μm-0.3 μm and the average particle size of the secondary particles is 2 μm-25 μm.

[0074] In some instances where the adhesive layer includes polymer particles, the polymer particles include first polymer particles and second polymer particles.

[0075] In some instances where the adhesive layer includes polymer particles, the polymer particles are only second polymer particles, and the coverage of the adhesive layer on the surface of the carrier layer is 15%-97%.

[0076] In some instances where the adhesive layer includes polymer particles, the polymer particles are only the first polymer particles, and the coverage of the adhesive layer on the surface of the carrier layer is 15%-45%.

[0077] In some instances where the adhesive layer comprises polymer particles, the thickness of the adhesive layer is 0.5 μm to 6 μm (e.g., 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm or 6 μm).

[0078] In some instances where the adhesive layer comprises polymer particles, the adhesive layer is located on both sides of the carrier layer, and the adhesive layers on the two sides of the carrier layer are different. Here, "different" refers to one or more differences in the thickness, morphology, coverage, and composition of the adhesive layers on both sides.

[0079] In some instances where the adhesive layer comprises polymer particles, the adhesive layer can be prepared by dispersing the polymer particles in deionized water or water to form an adhesive slurry, and then coating the adhesive slurry onto the surface of a carrier to form the adhesive layer.

[0080] In other examples, the coating layer comprises a second polymer and second particles, the coating layer having a porous structure formed by the second polymer. In this porous structure, the second polymer is a continuous phase, and the second particles are dispersed within the porous structure. Lithium dendrites (especially sharp dendrites) often originate in regions with excessively high local current density or impaired ion transport (such as poor interfacial contact points or electrode surface defects). The aforementioned coating layer can further enhance the adhesion between the separator and the electrode, reduce the relative slippage and delamination between the electrode and the separator, and play a certain role in maintaining the integrity of the electrode structure and preventing the shedding of active materials. This reduces the damage to the interface microstructure during cycling. At the same time, it is also conducive to the uniform diffusion and transport of lithium ions at the interface between the separator and the electrode, reducing areas with excessively high or low local current density. The uniform ion flux can reduce or even avoid excessive local lithium ion accumulation, thereby reducing the driving force for dendrite nucleation and growth, reducing or even avoiding the formation of lithium dendrites. Moreover, the second particle in the coating layer can provide support and form a certain liquid storage space between the coating layer and the electrode. This allows the separator to have both high interfacial adhesion and a certain liquid storage space, further improving and reducing the risk of battery short circuit and further extending the fast-charging cycle life of the battery.

[0081] In other instances, the coating layer includes a second polymer but does not include second particles, and the coating layer has a porous structure formed from the second polymer.

[0082] In some instances, the second polymer includes one or more of the following: fluoropolymers, poly(p-phenylene terephthalamide), poly(m-phenylene isophthalamide), bio-based aramid, acrylate polymers, polyimide, polyacrylonitrile, polyacrylic acid, polyvinyl alcohol, polymodified polyvinyl alcohol, polyvinyl acetate, polyacrylamide, phenolic resins, epoxy resins, ethylene-vinyl acetate copolymers, lithium polystyrene sulfonate, polyethylene oxide, and cyanoethyl polyvinyl alcohol.

[0083] In some instances, the second particle comprises boehmite, alumina, barium sulfate, magnesium oxide, magnesium hydroxide, silicon dioxide, tin dioxide, titanium dioxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, nickel oxide, cerium oxide, zirconium titanate, barium titanate, magnesium fluoride, 1,3,5-triazine-2,4,6-triamine, melamine thiocyanate, melamine cyanurate, symmetrical triaminotriazine, and 2-(4-bromophenyl)-4,6-didi One or more of the following: methyl-1,3,5-triazine, 1-(4,6-diamino-1,3,5-triazine-2-yl)guanidine, 2,4-diamino-6-dimethylamino-1,3,5-triazine, cyanuric chloride, 2,4,6-tris(2-pyridyl)triazine, 2,4,6-triphenyl-1,3,5-triazine, tris(tribromophenoxy)triazine, 2-amino-4,6-methoxy-1,3,5-triazine, uracil, and cytosine.

[0084] In some instances where the adhesive layer comprises a second polymer and second particles, the second polymer accounts for 25%-80% of the total weight of the adhesive layer (e.g., 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, or 80%), and the second particles account for 20%-75% of the total weight of the adhesive layer (e.g., 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or 75%).

[0085] In some instances where the adhesive layer includes a second polymer but does not include second particles, the weight percentage of the second polymer is 80%-100% (e.g., 80%, 83%, 85%, 88%, 90%, 93%, 95%, 98%, or 100%) based on the total weight of the adhesive layer.

[0086] In some instances where the adhesive layer includes a second polymer or comprises both a second polymer and second particles, the adhesive layer may be a striped coating. Striped coating can form a plurality of striped coating areas, such as... Figure 3 , Figure 4 and Figure 5 As shown.

[0087] In some instances where the coating layer includes a second polymer or includes both a second polymer and second particles, the width of the striped coating area is 40 μm to 1000 μm (e.g., 40 μm, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, or 1000 μm). In this invention, the width of the striped coating area refers to the average vertical distance between the two long sides in the orthographic projection of the striped coating area onto the carrier layer surface. For example, 10 points are randomly selected on any one of the long sides, the vertical distance corresponding to each point is measured, and the average value is taken as the width between the two long sides. When the number of striped coating areas is greater than 1, the width of the striped coating area is the average width. For example, when the number of striped coating areas is less than or equal to 20, the width of the striped coating area is the average width of all the striped coating areas; when the number of striped coating areas is greater than 20, the width of the striped coating area is the average width of any 20 striped coating areas.

[0088] In some instances where the coating layer includes a second polymer or comprises both a second polymer and second particles, the spacing between adjacent striped coating areas is 15 μm to 800 μm (e.g., 15 μm, 30 μm, 50 μm, 80 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, 450 μm, 500 μm, 550 μm, 600 μm, 650 μm, 700 μm, 750 μm, or 800 μm). In this invention, the spacing between adjacent striped coating areas refers to the minimum vertical distance between the edge lines of two adjacent striped coating areas in the orthographic projection of the striped coating area onto the carrier layer surface. When the number of striped coating areas is greater than 2, the spacing between adjacent striped coating areas is the average of the spacing between adjacent striped coating areas. For example, when the number of striped coating areas is less than or equal to 20, the spacing between adjacent striped coating areas is the average of the spacing between all adjacent striped coating areas; when the number of striped coating areas is greater than 20, the spacing between adjacent striped coating areas is the average of the spacing between arbitrarily selected 20 adjacent striped coating areas.

[0089] In some instances where the coating layer includes a second polymer or includes both a second polymer and second particles, the spacing between adjacent striped coating areas is 15 μm to 800 μm, and the width of the striped coating area is 40 μm to 1000 μm.

[0090] In this invention, the width of the striped coating area and the spacing between adjacent striped coating areas can both be measured by SEM.

[0091] In some instances where the adhesive layer includes a second polymer or includes both a second polymer and second particles, the thickness of the adhesive layer is 0.5 μm to 3 μm (e.g., 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm or 3 μm).

[0092] In some instances where the adhesive layer includes a second polymer or includes both a second polymer and second particles, the adhesive layer is located on both sides of the carrier layer, and the adhesive layers on the two sides of the carrier layer are different. Herein, the difference in the adhesive layers on the two sides of the carrier layer refers to one or more differences in the thickness, coverage, and composition of the adhesive layers on both sides.

[0093] In some instances where the adhesive layer includes a second polymer or comprises a second polymer and second particles, the adhesive layer can be prepared by dispersing the second polymer or the second polymer and second particles in an organic solvent to form an adhesive layer slurry, and then coating the adhesive layer slurry onto a carrier surface to form the adhesive layer. It is understood that in the finished adhesive layer, the organic solvent is substantially completely recovered, and the weight percentage of the organic solvent in the adhesive layer is less than or equal to 0.2% (e.g., 0.2%, 0.15%, 0.1%, 0.05%, 0.01%, or 0). The organic solvent includes at least one of N-methylpyrrolidone (NMP), dimethylacetamide (DMAC), and acetone.

[0094] In some instances, the adhesive layer is located on both sides of the carrier layer, and the adhesive layer includes a first adhesive layer and a second adhesive layer.

[0095] In some instances, the first coating layer comprises polymer particles, and the second coating layer comprises a second polymer.

[0096] In some instances, the first adhesive layer comprises a second polymer, and the second adhesive layer comprises a second polymer and second particles.

[0097] In some instances, the first coating layer comprises polymer particles, and the second coating layer comprises a second polymer and second particles.

[0098] In some instances, the first adhesive layer may be the same as or different from the second adhesive layer. The difference between the first adhesive layer and the second adhesive layer refers to one or more differences in thickness, coverage, polymer morphology, and composition.

[0099] A second aspect of the present invention provides a battery comprising a positive electrode, a negative electrode, and a separator as described in the first aspect of the present invention, the separator being located between the positive electrode and the negative electrode, the positive electrode comprising a positive current collector and a positive active layer located on one or both surfaces of the positive current collector.

[0100] In some examples, the positive electrode active layer comprises positive electrode active particles, and the cohesive force between these particles is 5 N / m to 60 N / m (e.g., 5 N / m, 10 N / m, 15 N / m, 20 N / m, 25 N / m, 30 N / m, 35 N / m, 40 N / m, 45 N / m, 50 N / m, 55 N / m, or 60 N / m). Controlling the cohesive force between the positive electrode active particles within this range can reduce the risk of particles falling off, further improving the battery's micro-short circuit problem. When the cohesive force between the positive electrode active particles is below 5 N / m, powder is easily shed during battery manufacturing, resulting in foreign object protrusions. This powder shedding also causes a mismatch in the ratio of positive to negative electrode capacity, increasing the risk of lithium dendrite formation and affecting the effectiveness of further improving the battery's micro-short circuit. When the cohesive force between the positive electrode active particles is higher than 60 N / m, the excessively strong bonding between the positive electrode active particles will bind them to each other, restricting volume changes and causing stress accumulation inside the particles. During charge and discharge cycles, repeated expansion and contraction can easily lead to microcracks inside the active particles or even particle breakage. The increased surface area of ​​the positive electrode active particles due to cracks may exacerbate side reactions. Broken particles may detach from the conductive network, affecting lithium-ion transport. Furthermore, excessively high cohesive force between positive electrode active particles usually requires an increase in the amount of binder, which will reduce the energy density of the battery and deteriorate the battery kinetics.

[0101] In this invention, the cohesive force between the positive electrode active particles can be tested by the following method: 1) Sample preparation: Cut the electrode sheet into 20mm×100mm pieces and attach the non-test surface to the stainless steel plate with double-sided tape; 2) Apply 3M tape: Apply 3M tape to the test surface, press it with a pressure roller, and bend the end of the 3M tape 180°; 3) Test: Peel the 3M tape with a tensile testing machine at a speed of 50mm / min and record the average peeling force (unit: N / mm), which is the cohesive force. The peeled 3M tape will carry some of the positive electrode active particles out, that is, some of the positive electrode active particles are peeled off with the 3M tape, rather than peeling the entire positive electrode active layer from the positive electrode current collector.

[0102] In some instances, the positive electrode active particles are composed of one or more of lithium oxide, lithium titanate, lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, and lithium manganese oxide.

[0103] In some instances, the positive electrode active layer comprises carbon nanotubes.

[0104] In some instances, the aspect ratio of the carbon nanotubes is greater than or equal to 10 (e.g., 10, 50, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, or 10000). Controlling the aspect ratio of the carbon nanotubes within the above range helps to form a more complete three-dimensional network structure, increasing the entanglement and binding effect on the positive electrode active particles. Simultaneously, carbon nanotubes possess good flexibility, and the framework structure constructed from carbon nanotubes with aspect ratios within the above range can effectively buffer the volume expansion of the positive electrode active particles during charging and discharging, reducing the deterioration of the positive electrode sheet structural stability caused by stress concentration, thereby further reducing the risk of positive electrode active particle powder shedding to a certain extent.

[0105] In some instances, the aspect ratio of the carbon nanotubes is greater than 1000.

[0106] In this invention, the aspect ratio of the carbon nanotube is the ratio of the average length to the average diameter of the carbon nanotube. The aspect ratio of the carbon nanotube can be obtained by the following method: Using a scanning electron microscope, within a 20μm × 20μm range, the diameter of the carbon nanotube is statistically analyzed. The width of the outer diameter of each carbon nanotube is measured at three different locations, and the average value is recorded as the diameter of that carbon nanotube. The average diameter is obtained by measuring the average diameter of 10 carbon nanotubes. The average length is obtained by measuring the average length of 10 carbon nanotubes. The aspect ratio is then obtained by dividing the average length of the carbon nanotube by the average diameter.

[0107] In some instances, the average diameter of the carbon nanotubes is 6 nm to 10 nm (e.g., 6 nm, 6.5 nm, 7 nm, 7.5 nm, 8 nm, 8.5 nm, 9 nm, 9.5 nm, or 10 nm).

[0108] In some instances, the average length of the carbon nanotubes is 12 μm to 18 μm (e.g., 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm or 18 μm).

[0109] In some examples, the positive electrode active layer includes a positive electrode additive, which includes one or more of dimethyl phthalate, diethyl phthalate, tricresyl phosphate, trioctyl phosphate, dioctyl sebacate, and dioctyl adipate. Adding the above-mentioned positive electrode additives to the positive electrode active layer can effectively increase the flexibility of the positive electrode sheet, reduce or even avoid stress accumulation in the arc region of the electrode sheet in wound batteries, further reduce the risk of positive electrode sheet breakage and powder shedding, and thus further reduce the risk of micro-short circuits caused by powder shedding.

[0110] In some instances, the positive electrode additive is present in the positive electrode active layer at a weight percentage of 0.05%-0.2% (e.g., 0.05%, 0.08%, 0.1%, 0.13%, 0.15%, 0.18% or 0.2%).

[0111] In some instances, the positive electrode active layer also includes a positive electrode binder and a positive electrode conductive agent.

[0112] In some instances, the positive electrode binder includes one or more of polyvinylidene fluoride (PVDF), acrylic-modified PVDF, polyacrylate polymers, acrylic polymers, polytetrafluoroethylene, polyacrylonitrile, polyimide, styrene-butadiene rubber, and styrene-acrylic rubber.

[0113] In some instances, the positive electrode conductive agent includes one or more of conductive carbon black, conductive graphite, and graphene, other than carbon nanotubes.

[0114] In some instances, based on the total weight of the positive electrode active layer, the weight percentage of the positive electrode active particles is 96%-98.7% (e.g., 96%, 96.3%, 96.5%, 96.8%, 97%, 97.3%, 97.5%, 97.8%, 98%, 98.3%, 98.5%, or 98.7%), the weight percentage of the positive electrode conductive agent is 0.1%-1% (e.g., 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1%), and the weight percentage of the positive electrode binder is 0.5%-3% (e.g., 0.5%, 0.8%, 1%, 1.3%, 1.5%, 1.8%, 2%, 2.3%, 2.5%, 2.8%, or 3%).

[0115] In some instances, the negative electrode includes a negative current collector and a negative active layer located on one or both surfaces of the negative current collector, the negative active layer comprising a silicon-based material.

[0116] In some instances, the silicon-based material includes one or more of silicon-oxygen particles, silicon-carbon particles, elemental silicon particles, silicon alloy particles, and silicon-nitrogen particles.

[0117] In some instances, the average particle size of the silicon-carbon particles is 5 μm-12 μm (e.g., 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm or 12 μm).

[0118] In some instances, the elemental silicon content in the negative electrode active layer is 3%-50% by weight (e.g., 3%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%).

[0119] In some instances, the negative electrode active layer further includes a carbon-based material, which includes one or more of natural graphite and artificial graphite.

[0120] In some instances, the negative electrode active layer comprises a negative electrode active material, which includes silicon-based materials and optionally ("optionally" means that it may or may not be present) carbon-based materials.

[0121] In some instances, the carbon-based materials include synthetic graphite and natural graphite.

[0122] In some instances, the negative electrode active material is a silicon-based material.

[0123] In some instances, based on the total weight of the silicon-based material and the carbon-based material, the weight percentage of the silicon-based material can range from 5% to 100% (e.g., 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 100%), and the weight percentage of the carbon-based material can range from 95% to 0% (e.g., 95%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, 5%, 1%, or 0%). However, it should be noted that the sum of the weight percentages of the silicon-based material and the carbon-based material is 100%.

[0124] In some instances, the negative electrode active material layer also includes a negative electrode conductive agent and a negative electrode binder.

[0125] In some instances, the negative electrode conductive agent includes one or more of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, and carbon nanotubes.

[0126] In some instances, the negative electrode binder includes one or more of polyurethane, polyacrylic acid, acrylate adhesives, sodium carboxymethyl cellulose, styrene-butadiene latex, polytetrafluoroethylene, polyethylene oxide, and polyvinylidene fluoride.

[0127] In some instances, based on the total weight of the negative electrode active layer, the negative electrode active material accounts for 80%-99% of the weight, the negative electrode conductive agent accounts for 0.5%-10% of the weight, and the negative electrode binder accounts for 0.5%-10% of the weight.

[0128] In some instances, the battery has a charging cutoff voltage greater than or equal to 4.5V (e.g., 4.5V, 4.53V, 4.55V, 4.57V, 4.6V, or 4.63V).

[0129] In some instances, the battery further includes an electrolyte, which can be a conventional electrolyte in the art, such as an electrolyte comprising lithium salts, organic solvents, and additives.

[0130] In some instances, the battery is a lithium-ion rechargeable battery.

[0131] The application of the battery described in this invention is not particularly limited and can be used for a variety of known applications. Examples include: mobile computers, laptops, portable phones, e-book players, fax machines, copiers, printers, headphones, video recorders, LCD TVs, cleaners, calculators, tape recorders, radios, backup power supplies, automobiles, motorcycles, electric boats, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, cameras, large household batteries, energy storage power stations, etc.

[0132] The present invention will be described in detail below through embodiments. The embodiments described herein are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0133] The following examples illustrate the separator and battery of the present invention.

[0134] Example 1

[0135] (1) Diaphragm

[0136] Organic granules (composed of melamine cyanurate), a first binder (methacrylic acid:sodium polymethyl cellulose (weight ratio) = 1:1), and deionized water were mixed to obtain an organic slurry with a solid content of 30%. Based on 100% solid mass, the weight ratio of organic granules to the first binder was 94:6. After thorough mixing, the organic slurry was coated onto one side of a substrate layer (composed of polyethylene, thickness 5 μm) using a gravure roller. After drying in a multi-section oven at 60°C, an organic coating was formed. The first polymer granules (composed of polymethyl methacrylate, with an average particle size of 6 mm for secondary particles) were then used. A first slurry with a solid content of 10% was obtained by mixing a 1μm polymer with deionized water. After thorough stirring and dispersion, the first slurry was coated onto the surface of the organic coating using a gravure roller. After passing through a multi-section oven at 60°C, the first coating layer was dried. A second polymer (polyvinylidene fluoride) and a second particle (alumina) were dispersed in a solvent DMAC and stirred thoroughly to obtain a second slurry with a solid content of 10%. The weight ratio of the second polymer to the second particle was 60:40 based on 100% solid mass. After thorough stirring, the second slurry was coated onto the other side of the substrate layer using a gravure roller. After passing through a multi-section oven at 60°C, the second coating layer was dried.

[0137] The organic particles are blocky in shape, with an average aspect ratio of 1.8. Within an area of ​​20 μm × 20 μm arbitrarily selected on the surface of the organic coating, the number N of organic particles with an aspect ratio greater than 10 is [not specified]. 1 There are 8 diaphragms, and the diaphragms satisfy the following relationship: N 2 <N 3 The thickness of the organic coating is 2 μm; the average fiber diameter in the substrate layer is 0.15 μm, and the puncture strength of the substrate layer is 290 gf; the coverage of the first adhesive layer on the surface of the carrier layer is 30.3%, and the coverage of the second adhesive layer on the surface of the carrier layer is 45.6%.

[0138] (2) Positive electrode plate

[0139] Lithium cobalt oxide (positive electrode active particles), PVDF, and carbon nanotubes were mixed in N-methylpyrrolidone at a mass ratio of 97:2:1 to prepare a positive electrode slurry. This slurry was then coated onto both sides of a positive electrode current collector (aluminum foil). After drying and rolling, a positive electrode sheet was obtained. The cohesive force between the positive electrode active particles was 45 N / m, the average diameter of the carbon nanotubes was 8.1 nm, the average length of the carbon nanotubes was 15.3 μm, and the aspect ratio of the carbon nanotubes was 1888.9.

[0140] (3) Negative electrode plate

[0141] A negative electrode active material (silicon carbon particles: artificial graphite = 80%: 20%), binder (polyurethane: PVDF = 1: 1), sodium carboxymethyl cellulose, and conductive agent (carbon nanotubes: conductive carbon black = 3: 2) were mixed in a weight ratio of 91%:6%:2%:1%. The mixture was dispersed in water and then subjected to a double planetary mixing process to obtain a negative electrode slurry. This slurry was coated on both sides of a copper current collector, followed by drying and rolling to obtain the negative electrode sheet.

[0142] (4) Electrolyte

[0143] In an argon-filled glove box (moisture <10 ppm, oxygen <1 ppm), ethylene carbonate (EC), propylene carbonate (PC), and propyl propionate (PP) were mixed uniformly at a volume ratio of 2:1.5:2. Then, 14 wt.% LiPF6, 0.3 wt.% lithium bis(oxalato)borate (LiBOB), 2 wt.% 1,3-propanesulfonyl lactone, 3 wt.% 1,4-dicyano-2-butene, and 2 wt.% succinate (succinate) based on the total mass of the electrolyte were slowly added to the mixed solution and stirred until homogeneous to obtain a non-aqueous electrolyte. Finally, 20 wt.% fluoroethylene carbonate (FEC) based on the total mass of the electrolyte was added.

[0144] (5) Lithium-ion batteries

[0145] The positive electrode sheet obtained in step (2), the separator obtained in step (1), and the negative electrode sheet obtained in step (3) are wound together to form a bare battery cell. Then the bare battery cell is placed in an aluminum-plastic film, and the electrolyte obtained in step (4) is injected into the dried bare battery cell. After vacuum sealing, room temperature standing, high temperature formation and other processes, a lithium-ion battery is obtained. The positive electrode sheet corresponds to the side of the separator with organic coating, and the negative electrode sheet corresponds to the other side.

[0146] Example 2 group

[0147] Example 2a

[0148] The procedure was carried out in accordance with Example 1, except that the coating positions of the first slurry and the second slurry were changed. The first slurry was coated on the other side of the substrate layer, and the second slurry was coated on the surface of the organic coating.

[0149] Example 2b

[0150] The procedure was carried out in accordance with Example 1, except that the first slurry was applied to the surface of the organic coating and the other side of the substrate layer, and the second slurry was not applied.

[0151] Example 2c

[0152] The procedure was carried out in accordance with Example 1, except that the second slurry was applied to the surface of the organic coating and the other side of the substrate layer, and the first slurry was no longer applied.

[0153] Example 3 Group

[0154] This set of examples illustrates the effects of changes in the average aspect ratio of organic particles.

[0155] This embodiment group is based on Example 1, except that the average aspect ratio of the organic particles is changed, as detailed in Table 1.

[0156] Example 4 group

[0157] This set of examples illustrates the effects of changes in the specific selection and morphology of nitrogen-containing organic compounds in organic particles.

[0158] This embodiment group is based on Example 1, except that the specific selection and morphology of the nitrogen-containing organic matter in the organic particles are changed, as detailed in Table 1.

[0159] Example 5 group

[0160] This set of examples illustrates the effects of changes in the thickness of the organic coating.

[0161] This set of embodiments is based on Embodiment 1, except that the thickness of the organic coating and the weight ratio of organic particles to the first adhesive in the organic coating are changed. In Embodiment 5a, the weight ratio of organic particles to the first adhesive is 99:1, and in Embodiment 5b, the weight ratio of organic particles to the first adhesive is 90:10. See Table 1 for details.

[0162] Example 6 group

[0163] Example 6a

[0164] The procedure was carried out in accordance with Example 1, except that the diaphragm did not satisfy the relationship N. 2 <N 3 And satisfy the relation N 2 =N 3 .

[0165] Example 6b

[0166] The procedure was carried out in accordance with Example 1, except that the diaphragm did not satisfy the relationship N. 2 <N 3 And satisfy the relation N 2 >N 3 .

[0167] Example 7 group

[0168] This set of examples illustrates the effects of changes in the thickness of the substrate layer and the fiber diameter.

[0169] This embodiment group is based on Embodiment 1, except that the thickness of the substrate layer and the fiber diameter are changed, as detailed in Table 1.

[0170] Table 1

[0171]

[0172] Example 8 group

[0173] This set of examples illustrates the effects of changes in the composition, average particle size, and coverage of the first polymer particle layer on the carrier layer surface, as well as changes in the composition, average particle size, and coverage of the second polymer particle layer on the carrier layer surface.

[0174] This set of examples is based on Example 1, except that the polymer particle composition, average particle size and coverage of the first coating layer on the carrier layer surface are changed. In Example 8a, only the second polymer particles are used, and in Example 8b, only the first polymer particles are used. See Table 2 for details.

[0175] Table 2

[0176]

[0177] Example 9 group

[0178] This set of examples illustrates the effects of altering the cohesive force between positive electrode active particles by adjusting the weight ratio of the positive electrode binder in the positive electrode active layer and / or the selection of the positive electrode binder.

[0179] Example 9a

[0180] This embodiment group is based on Example 1, except that the cohesive force between the positive electrode active particles is 5.2 N / m.

[0181] Example 9b

[0182] This embodiment group is based on Example 1, except that the cohesive force between the positive electrode active particles is 59.7 N / m.

[0183] Example 9c

[0184] This embodiment group is based on Example 1, except that the cohesive force between the positive electrode active particles is 4.6 N / m.

[0185] This embodiment group is based on Example 1, except that the cohesive force between the positive electrode active particles is 61.4 N / m.

[0186] Example 10 group

[0187] This set of examples illustrates the effects of adding positive electrode additives to the positive electrode active layer by adjusting the weight ratio of the positive electrode binder in the positive electrode active layer.

[0188] This embodiment group is based on Example 1, except that a positive electrode additive is added to the positive electrode active layer, as detailed in Table 3.

[0189] Example 11 group

[0190] This set of examples illustrates the effects of changes in the average diameter and average length of carbon nanotubes.

[0191] This embodiment group is based on Embodiment 1, except that the average diameter and average length of the carbon nanotubes are changed, as detailed in Table 3.

[0192] Table 3

[0193]

[0194] Comparative Example 1

[0195] The procedure was carried out in accordance with Example 1, except that the organic particles were replaced with the same amount of alumina particles by weight.

[0196] Comparative Example 2

[0197] The procedure was carried out in accordance with Example 1, except that the average aspect ratio of the organic particles was 4.

[0198] Test case

[0199] The batteries prepared by the examples and comparative examples were subjected to the following tests.

[0200] 1. Short circuit test

[0201] In an environment of 25℃±5℃, the battery was discharged to 3V at 0.2C, left to stand for 10 minutes, charged to 100% SOC at 0.7C, with a cutoff current of 0.05C, and left to stand for 10 minutes. The voltage measured after this period was recorded as the initial voltage V. 0 Then it was stored at 25±2℃ for 7 days. After storage, the final voltage was measured to be V. 1 Then the voltage drop ΔV = V 0 -V 1 .

[0202] 2. Fast charging cycle performance test and lithium plating test

[0203] At 25℃±2℃, the battery was charged at a constant current and constant voltage of 0.7C to 4.53V, cut off at 0.05C, and then discharged at a constant current of 0.2C to 3.0V. The initial discharge capacity at this point is denoted as C. 0 After 10 minutes of rest, the cycle is as follows: 3C constant current / constant voltage charging to 4.25V, cut off at 2C, then 2C constant current / constant voltage charging to 4.48V, cut off at 1.5C, then 1.5C constant current / constant voltage charging to 4.53V, cut off at 0.18C, rest for 5 minutes, and then discharge at 0.7C to 3.0V. After 600 cycles, 0.7C constant current / constant voltage charging is performed to 4.53V, cut off at 0.05C, and then 0.2C constant current discharging is performed to 3.0V. The discharge capacity at this point is denoted as C. 1 Fast charging cycle capacity retention rate: C = (C 1 / C 0 )×100%;

[0204] After the cycle is completed, the battery is disassembled to check whether lithium has been deposited on the negative electrode of each fold in the cell. If lithium deposition occurs in a fold, it means that lithium has been deposited on the negative electrode of that fold. If no lithium deposition occurs in a fold, it means that no lithium has been deposited on that fold. If the ratio of the number of folds with lithium deposition to the total number of negative electrode folds is less than 10%, the result is "1". If the ratio is greater than or equal to 10% but less than 20%, the result is "2". If the ratio is greater than or equal to 20% but less than 40%, the result is "3". If the ratio is greater than or equal to 40% but less than 70%, the result is "4". If the ratio is greater than or equal to 70%, the result is "5".

[0205] The results are recorded in Table 4.

[0206] Table 4

[0207]

[0208] As can be seen from Table 4, by comparing the comparative example and the embodiment, the battery prepared by the separator in the embodiment has a lower voltage drop, a significantly improved capacity retention rate during fast charging cycles, and a significantly improved lithium plating situation. This indicates that by setting organic particles containing nitrogen-containing organic compounds with nitrogen-containing heterocyclic rings in the separator, and controlling the average aspect ratio of the organic particles, the risk of short circuit in the battery is reduced, and the fast charging cycle life of the battery is extended.

[0209] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A diaphragm, characterized by The diaphragm comprises a substrate layer and an organic coating layer on one side or both sides of the substrate layer, the organic coating layer comprises organic particles, the composition of the organic particles comprises nitrogen-containing organic matter, the nitrogen-containing organic matter comprises one or more of uracil, 4,6-dimethyl-2-phenyl pyrimidine, cytosine, 2,4-dimercapto pyrimidine, 2,4-dimercapto-5,6-diaminopyrimidine, 4-amino-2,6-dihydroxypyrimidine, 2-mercaptobenzimidazole, melamine cyanurate, melamine thiocyanate, polypyrrole, sulfonated polytriazole, the molecular structure of the nitrogen-containing organic matter comprises a nitrogen-containing heterocycle, and the average aspect ratio of the organic particles is 1-3; the diaphragm satisfies the following relationship formula: N 2 <N 3 , wherein, in the thickness direction of the diaphragm, the surface of the organic coating layer away from the substrate layer is a first surface, the number of the organic particles with an aspect ratio greater than 10 in the first surface is denoted as N 2 , unit: pieces, in the thickness direction of the diaphragm, the surface of the organic coating layer close to the substrate layer is a second surface, and the number of the organic particles with an aspect ratio greater than 10 in the second surface is denoted as N 3 , unit: pieces.

2. The septum of claim 1, wherein, The number of said organic particles having an aspect ratio greater than 10 within an area of said organic coating of optionally 20 pm x 20 pm is noted N 1 1 ≤ 20;​ And / or, the thickness of the organic coating layer is 0.2-5 μm; And / or, the morphology of the organic particles includes one or more of block, rod, sheet, laminated sheet, quasi-spherical and spherical.

3. The septum of claim 1, wherein, The substrate layer is a three-dimensional porous network structure formed by interweaving a plurality of fibers, the average diameter of the fibers is 0.02-0.45 μm; And / or, the puncture strength of the substrate layer is 200-600 gf; And / or, the thickness of the substrate layer is 3.5-16 μm; And / or, the average pore size of the substrate layer is 30-50 nm; And / or, the porosity of the substrate layer is 25-45%; And / or, the composition of the substrate layer includes one or more of polyolefin, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinyl chloride, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyetherimide, polyethylene terephthalate, polybutylene terephthalate, poly-p-phenyleneterephthalamide, poly-m-phenyleneterephthalamide, polybenzimidazole, polysulfone, polyketone or derivatives of the above polymers.

4. The separator according to any one of claims 1 to 3, wherein The puncture strength of the substrate layer is 280-450 gf; And / or, the separator includes a carrier layer and a coating layer on one or both surfaces of the carrier layer, the carrier layer includes a substrate layer and an organic coating layer on one or both surfaces of the substrate layer; And / or, the separator includes a carrier layer and a coating layer on one or both surfaces of the carrier layer, the coverage of the coating layer on the surface of the carrier layer is 15-97%; And / or, the organic coating layer further includes a first binder, the weight percentage of the organic particles in the total weight of the organic coating layer is 90-99%, and the weight percentage of the first binder is 1-10%; And / or, the organic particles have a layered crystal structure.

5. The septum of claim 4, wherein, The coating layer includes polymer particles, the composition of the polymer particles includes a first polymer, and the first polymer includes one or more of fluorine-containing polymer, acrylate polymer, polyimide, phenolic resin, poly-p-phenyleneterephthalamide, poly-m-phenyleneterephthalamide, bio-based aramid, polyethylene, polypropylene, and styrene-butadiene rubber; And / or, the coating layer includes polymer particles, and the average particle size of the polymer particles is 0.1-20 μm; And / or, the coating layer includes polymer particles, and the polymer particles include at least one of first polymer particles and second polymer particles, the first polymer particles are agglomerated polymer particles, and the second polymer particles are non-agglomerated polymer particles; And / or, the thickness of the coating layer is 0.5-6 μm; And / or, the coating layer is located on both surfaces of the carrier layer, and the coating layers on both surfaces of the carrier layer are different.

6. The septum of claim 4, wherein, The coating layer includes a second polymer, and the coating layer has a porous structure formed by the second polymer; or, the adhesive layer comprises a second polymer, and the second polymer comprises one or more of a fluoropolymer, a poly(p-phenylene terephthalamide), a poly(m-phenylene isophthalamide), a bio-based aramid, an acrylate polymer, a polyimide, a polyacrylonitrile, a polyacrylic acid, a polyvinyl alcohol, a polyvinyl acetate, a polyacrylamide, a phenol formaldehyde resin, an epoxy resin, an ethylene-vinyl acetate copolymer, a polystyrene sulfonate lithium, a polyethylene oxide, and a cyanoethyl polyvinyl alcohol; or, the adhesive layer comprises a second polymer and a second particle, and the second particle comprises one or more of boehmite, alumina, barium sulfate, magnesium oxide, magnesium hydroxide, silica, tin dioxide, titanium oxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, nickel oxide, cerium oxide, zirconium titanate, barium titanate, magnesium fluoride, 1,3,5-triazine-2,4,6-triamine, melamine trithiocyanate, melamine cyanurate, sym-trisamino triazine, 2-(4-bromophenyl)-4,6-dimethyl-1,3,5-triazine, 1-(4,6-diamino-1,3,5-triazin-2-yl) guanidine, 2,4-diamino-6-dimethylamino-1,3,5-triazine, trichloro cyanuric acid, 2,4,6-tris(2-pyridyl) triazine, 2,4,6-triphenyl-1,3,5-triazine, tris(tribromophenoxy) triazine, 2-amino-4,6-methoxy-1,3,5-triazine, uracil, and cytosine; or, the adhesive layer comprises a second polymer, and the weight percentage of the second polymer in the adhesive layer is 25%-100%, based on the total weight of the adhesive layer; or, the adhesive layer comprises a second polymer and a second particle, and the weight percentage of the second particle in the adhesive layer is 20-75%, based on the total weight of the adhesive layer; and / or, the thickness of the adhesive layer is 0.5 μm-3 μm.

7. A battery, characterized by The battery comprises a positive electrode sheet, a negative electrode sheet, and the separator of any one of claims 1-6, the separator being located between the positive electrode sheet and the negative electrode sheet, and the positive electrode sheet comprising a positive electrode current collector and a positive electrode active layer located on one side or both sides of the positive electrode current collector.

8. The battery of claim 7, wherein, The positive electrode active layer comprises positive electrode active particles, and the cohesion between the positive electrode active particles is 5 N / m-60 N / m; and / or, the positive electrode active layer comprises carbon nanotubes, and the aspect ratio of the carbon nanotubes is greater than or equal to 10; and / or, the positive electrode active layer comprises a positive electrode additive, and the positive electrode additive comprises one or more of dimethyl phthalate, diethyl phthalate, tritolyl phosphate, trioctyl phosphate, dioctyl sebacate, dioctyl adipate.

9. The battery of claim 8, wherein, The positive electrode active particles comprise one or more of lithium titanate, lithium cobaltate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, and lithium manganate; and / or, the positive electrode active layer comprises carbon nanotubes, and the aspect ratio of the carbon nanotubes is greater than 1000; and / or, the average tube diameter of the carbon nanotubes is 6 nm-10 nm; and / or, the average tube length of the carbon nanotubes is 12 μm-18 μm; And / or, in the positive electrode active layer, the weight percentage of the positive electrode additive is 0.05%-0.2%.

10. The battery of claim 7, wherein, The negative electrode sheet comprises a negative electrode current collector and a negative electrode active layer located on one side or both sides of the negative electrode current collector, wherein the negative electrode active layer comprises a silicon-based material, and the silicon-based material comprises one or more of silicon-oxygen particles, silicon-carbon particles, elemental silicon particles, silicon alloy particles and silicon-nitrogen particles, and the average particle size of the silicon-carbon particles is 5-12 mu m. And / or, the charging cut-off voltage of the battery is greater than or equal to 4.5V.

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