A separator and a battery

Abstract

The present application provides a separator and a battery, the separator comprising a carrier layer and a glue layer located on at least one side surface of the carrier layer, the carrier layer comprising a substrate layer and an organic coating layer located on at least one side surface of the substrate layer, the organic coating layer comprising first particles, the composition of the first particles comprising a bicyclic organic compound, the molecular structure of the bicyclic organic compound comprising a bicyclic structure formed by a 2-mercaptoimidazole ring and a benzene ring sharing 2 adjacent carbon atoms, the glue layer having a porous continuous phase structure, the glue layer comprising a polymer forming the porous structure and second particles, the separator satisfying the following relationship: 1 1 / N 1 ≤ 15, wherein B 1 is the Dv50 of the second particles, in units of μm, and N 1 is the Dv10 of the first particles, in units of μm. The battery of the present application comprises the above separator. The separator of the present application can weaken or even eliminate the static accumulation phenomenon, and has high adhesion and electrolyte wettability, so that the battery has low self-discharge rate and long cycle stability.

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 of this invention. Background Technology

[0002] Lithium-ion batteries offer advantages over other rechargeable batteries, including high energy density, long cycle life, low self-discharge, and no memory effect, leading to widespread market acceptance and application since their introduction. A lithium-ion battery typically consists of positive and negative electrode materials, a separator, and an electrolyte. The separator, acting as a barrier between the positive and negative electrode materials, primarily prevents direct contact and electron transport between them, while allowing ions from the electrolyte to pass through and reach the electrodes. Currently, mainstream commercial separators are mostly made of polymeric materials (such as polyethylene (PE), polypropylene (PP), polyimide, and aramid), which possess excellent electrochemical stability and mechanical strength. However, polymeric materials, especially polyolefins, have extremely high resistivity, making them prone to generating and accumulating large amounts of static charge during production and processing due to friction.

[0003] This electrostatic buildup phenomenon has led to a series of serious technical challenges. First, the charged separator strongly attracts fine particles such as dust and metal shavings from the environment. These impurities are introduced into the cell during subsequent battery assembly, easily puncturing the separator and causing internal short circuits, resulting in increased battery self-discharge rate and reduced cycle life. Furthermore, in high-speed winding or stacking processes, the separator can adhere to and misalign with the electrodes due to electrostatic adsorption, leading to uneven winding and reduced stacking precision, severely restricting production efficiency and product yield. Simultaneously, strong static electricity can also generate electrostatic discharge during production, interfering with or damaging precision battery manufacturing equipment, thereby significantly reducing battery process capability.

[0004] Therefore, it is important to invent a battery that includes a separator capable of reducing or even eliminating static electricity buildup. Summary of the Invention

[0005] In the prior art, in order to eliminate the static charge of polymer materials, especially polyolefin materials, the surface of the separator is usually modified or coated with an antistatic coating. However, there are often problems such as weak coating adhesion, affecting the pore structure of the separator, or poor compatibility with the electrolyte. This will reduce the wettability or ionic conductivity of the separator, reduce the interfacial performance between the separator and the electrode, and affect the long cycle performance of the battery.

[0006] To simultaneously overcome the problems of electrostatic accumulation in existing separators and reduced adhesion and electrolyte wettability of the separator coating after modification or antistatic coating, this invention provides a separator and a battery including the separator of this invention. The separator of this invention can weaken or even eliminate electrostatic accumulation, reduce or even avoid impurity adsorption by the separator, and reduce or even prevent the risk of internal short circuits caused by separator puncture, thereby effectively reducing the battery's self-discharge rate and improving the battery's long-cycle stability and safety. Simultaneously, the separator of this invention also has high adhesion and electrolyte wettability, ensuring the structural integrity and good ionic conductivity of the separator, improving the interfacial performance between the separator and the electrode, and enhancing the battery's long-cycle performance. Furthermore, the separator of this invention can reduce or even avoid the adverse effects of electrostatic accumulation on battery manufacturing processes, improving battery manufacturing capabilities.

[0007] To achieve the above objectives, a first aspect of the present invention provides a separator comprising a carrier layer and an adhesive layer located on at least one surface of the carrier layer. The carrier layer comprises a substrate layer and an organic coating located on at least one surface of the substrate layer. The organic coating comprises first particles, the first particles comprising a bicyclic organic compound. The molecular structure of the bicyclic organic compound comprises a bicyclic structure formed by a 2-mercaptoimidazole ring sharing two adjacent carbon atoms and a benzene ring. The adhesive layer has a porous structure and comprises a polymer forming the porous structure and second particles. The separator satisfies the following relationship: 1 ≤ B 1 / N 1 ≤15, where B 1 The Dv50 of the second particle is expressed in μm and N. 1 Dv10 is the value of the first particle, in μm.

[0008] 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.

[0009] By employing the above technical solution, the present invention has at least the following advantages compared with the prior art:

[0010] The separator of the present invention includes an organic coating, wherein the organic coating includes a first particle composed of a bicyclic organic compound. The molecular structure of the bicyclic organic compound includes a bicyclic structure formed by a 2-mercaptoimidazole ring and a benzene ring sharing two adjacent carbon atoms. This bicyclic structure can form a large, planar, and highly conjugated π-electron system. The π orbitals in this π-electron system have a large overlap, which can temporarily accept electrons or allow electrons to delocalize within it. This reduces the local charge density and inhibits the accumulation of static charge. As a result, the static charge (electrons) accumulated in the separator can migrate and disperse through the conjugated π-electron system formed by the bicyclic structure in the bicyclic organic compound, rather than being concentrated in a local area of ​​the separator. This weakens the electrostatic accumulation phenomenon of the separator, reduces or even avoids internal short circuits caused by electrostatic adsorption of impurities puncturing the separator, reduces the self-discharge rate of the battery, and improves the long-cycle stability and safety of the battery. Moreover, the molecular structure of bicyclic organic compounds includes polar groups (e.g., thiol (-SH), secondary amino (-NH-), imino (C=N-)), which can improve the wettability of the electrolyte to the separator, thereby increasing the lithium-ion transport rate and further improving the long-cycle stability of the battery.

[0011] The adhesive layer on the surface of the organic coating in the separator of the present invention includes a polymer forming a porous structure and second particles. The polymer forming the porous structure can enhance the bonding strength of the adhesive layer and improve the interfacial adhesion between the separator and the electrode. The second particles have a suitable particle size, which can improve the fit between the separator and the electrode. Thus, in synergy with the organic coating, it weakens or even inhibits the electrostatic adsorption of the separator, reduces or even avoids internal short circuits caused by electrostatic adsorption of impurities piercing the separator, further reduces the self-discharge rate, and improves the long-cycle performance and safety performance of the battery. As a result, the separator can reduce electrostatic accumulation while having good adhesion, fit and electrolyte wettability, improve the interfacial performance of the separator, effectively improve the interfacial compatibility between the separator and the electrode, improve the lithium ion transport rate, and further improve the long-cycle performance of the battery.

[0012] At the same time, the control diaphragm satisfies the following relationship: 1≤B 1 / N 1 With a particle size of ≤15, the electrostatic charge dispersion of the separator is further improved through the synergistic effect of the first and second particles, which further enhances the effect of improving electrostatic accumulation, reduces or even avoids separator puncture caused by electrostatic adsorption of impurities, reduces the risk of internal short circuit in the battery, and can also further improve the flatness of the separator and the wettability of the electrolyte, improve the interface performance between the separator and the electrode, so that the battery has both a low self-discharge rate and good long cycle performance.

[0013] Furthermore, the electrostatic accumulation of the separator of the present invention is reduced, which can reduce or even eliminate separator adhesion and misalignment in the battery manufacturing process, improve production efficiency and product yield, and prevent electrostatic discharge of the separator, ensuring the stable operation of precision manufacturing equipment, thereby effectively improving the battery manufacturing process capability.

[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 image shown is one of the cross-sectional schematic diagrams of the diaphragm of the present invention.

[0017] Figure 2 The image shown is a second cross-sectional schematic diagram of the diaphragm of the present invention.

[0018] Figure 3 The third cross-sectional schematic diagram of the diaphragm of the present invention is shown.

[0019] Figure 4 The image shown is a schematic diagram of the surface of the diaphragm of the present invention.

[0020] Figure 5 The image shown is an SEM image of the adhesive layer in the diaphragm of this invention.

[0021] Figure 6 The image shown is a SEM image of the organic coating in the diaphragm of this 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] The membrane includes a carrier layer and an adhesive layer located on at least one surface of the carrier layer. The carrier layer includes a substrate layer and an organic coating located on at least one surface of the substrate layer. The organic coating includes first particles, the first particles being composed of a bicyclic organic compound. The molecular structure of the bicyclic organic compound includes a bicyclic structure formed by a 2-mercaptoimidazole ring sharing two adjacent carbon atoms and a benzene ring. The adhesive layer has a porous structure and includes a polymer forming the porous structure and second particles. The membrane satisfies the following relationship: 1 ≤ B 1 / N 1 ≤15 (e.g., 1, 2, 4, 6, 8, 10, 12, 14, or 15), where B 1 The Dv50 of the second particle is expressed in μm and N. 1 Dv10 is the value of the first particle, in μm.

[0025] In this invention, such as Figure 1 , Figures 2 to 3 As shown, the diaphragm 1 includes a carrier layer 11 and an adhesive layer 12 located on at least one side surface of the carrier layer 11. The carrier layer 11 includes a substrate layer 111 and an organic coating 112 located on at least one side surface of the substrate layer.

[0026] In some embodiments, such as Figure 1 As shown, the carrier layer 11 includes a substrate layer 111 and an organic coating 112 located on one side surface of the substrate layer, and the adhesive layer 12 is located on both sides surface of the carrier layer 11.

[0027] In some embodiments, such as Figure 2 As shown, the carrier layer 11 includes a substrate layer 111 and an organic coating 112 located on one side surface of the substrate layer, and the adhesive layer 12 is located on the surface of the organic coating 112.

[0028] In some embodiments, such as Figure 3 As shown, the carrier layer 11 includes a substrate layer 111 and an organic coating 112 located on both sides of the substrate layer, and the adhesive layer 12 is located on both sides of the carrier layer 11.

[0029] In some embodiments, the adhesive layer comprises a polymer and second particles, the adhesive layer having a porous structure, the porous structure being a porous continuous phase structure formed by the polymer as a continuous phase, and the second particles being dispersed in the porous structure.

[0030] In this invention, the term "the adhesive layer having a porous continuous phase structure" refers to the adhesive layer having a porous continuous phase structure in the coating area of ​​the adhesive layer. When the adhesive layer is non-continuously coated, such as in striped coating, the adhesive layer has a porous continuous phase structure in the striped coating area; when the adhesive layer is continuously coated, the adhesive layer has a porous continuous phase structure in the continuously coated area.

[0031] The molecular structure of the bicyclic organic compound includes a bicyclic structure formed by a 2-mercaptoimidazole ring and a benzene ring sharing two adjacent carbon atoms. This bicyclic structure can form a large, planar, and highly conjugated π-electron system. The π orbitals in this system have high overlap, which can temporarily accept electrons or allow electrons to delocalize, thereby effectively dispersing the charge, reducing the local charge density, and inhibiting the accumulation of static charge. The organic coating in the membrane includes first particles containing the aforementioned bicyclic organic compound, allowing the static charge (electrons) in the membrane to migrate and disperse within the membrane through the conjugated π-electron system formed by the bicyclic structure of the bicyclic organic compound, reducing or even eliminating the accumulation of static charge in the membrane. The concentration of localized areas of the membrane weakens or even eliminates electrostatic accumulation in the separator, reducing or eliminating the risk of separator puncture and internal short circuits caused by electrostatic adsorption of impurities. This lowers the battery's self-discharge rate and improves its long-cycle stability and safety. Furthermore, in the battery manufacturing process, reducing electrostatic accumulation in the separator significantly reduces problems such as separator adhesion and misalignment caused by electrostatic adsorption, improving the alignment accuracy and operational stability of winding or stacking processes, increasing battery production efficiency and product yield. It also reduces the risk of electrostatic discharge in the separator, minimizing interference or damage to precision battery manufacturing equipment, thus effectively improving battery process capabilities. Moreover, the polar groups in the molecular structure of bicyclic organic compounds (e.g., thiol (-SH), secondary amino (-NH-), imino (C=N-)) can enhance the wettability of the electrolyte on the separator, thereby increasing the lithium-ion transport rate and further improving the battery's long-cycle stability.

[0032] In the separator of the present invention, an adhesive layer comprising a polymer forming a porous structure and second particles is disposed on the surface of the organic coating. The porous structure helps to reduce the impact on the pore structure of the carrier layer. Simultaneously, the polymer forming the porous structure has good adhesion, enhancing the adhesive strength of the separator and thus improving the interfacial adhesion between the separator and the electrode. Furthermore, the second particles improve the fit between the separator and the electrode, further enhancing the adhesive strength of the separator, effectively improving the interfacial compatibility between the separator and the electrode, shortening the lithium-ion transport path, and further increasing the lithium-ion transport rate. This allows the separator to reduce electrostatic accumulation while improving the interfacial compatibility between the separator and the electrode, further improving the long-cycle performance and safety of the battery. Therefore, through the synergistic effect of the organic coating and the adhesive layer, the separator of the present invention can reduce electrostatic accumulation while possessing both high interfacial adhesion and high electrolyte wettability.

[0033] Meanwhile, in order to further enhance the synergistic effect of the organic coating and the adhesive layer, the present invention also controls the diaphragm to satisfy the following relationship: 1≤B 1 / N 1 ≤15. When the separator satisfies the above relationship, on the one hand, the first particle has a suitable specific surface area, which can further improve the electrostatic charge dispersion ability of the first particle, and reduce or even avoid secondary agglomeration caused by the small particle size of the first particle. This is beneficial to the dispersion of the first particle in the organic coating, further weakening or even eliminating the electrostatic accumulation phenomenon of the separator, reducing the self-discharge rate of the battery, and improving the long-cycle performance and safety of the battery. At the same time, it can also reduce the unevenness of the organic coating thickness caused by the secondary agglomeration of the first particle, improve the flatness of the separator, further improve the interfacial performance between the separator and the electrode, and improve the long-cycle stability and safety of the battery. On the other hand, the second particle has a suitable particle size, which can further improve the adhesion between the separator and the electrode, improve the flatness of the separator, so that the adhesive layer further cooperates with the organic coating to suppress the electrostatic adsorption of the separator and improve the interfacial performance between the separator and the electrode. Therefore, with the synergistic cooperation of the first particle and the second particle, the separator can reduce electrostatic accumulation while having high interfacial bonding strength and high flatness, thus improving the interfacial performance between the separator and the electrode.

[0034] When B 1 / N 1 When B < 1, the particle size of the second particle is too small, resulting in excessive moisture in the separator and affecting the battery's cycle performance; or the particle size of the first particle is too large, resulting in a small specific surface area, which affects the first particle's effect on improving the electrostatic accumulation of the separator and also makes the organic coating too thick, reducing the battery's energy density; when B 1 / N 1 When the particle size is greater than 15, the heat resistance, thermal stability and safety of the membrane will decrease if the particle size of the second particle is too large. As a result, the first particle is prone to secondary agglomeration, resulting in uneven thickness of the organic coating and reducing the thickness smoothness of the membrane. Alternatively, if the particle size of the first particle is too small, it will also be prone to secondary agglomeration, thereby reducing the electrostatic dispersion ability of the membrane and reducing the electrostatic accumulation and improving the effect.

[0035] In this invention, by providing an organic coating and an adhesive layer on the surface of the diaphragm, and controlling the diaphragm to satisfy the following relationship: 1≤B 1 / N 1 With a value ≤15, compared to existing technologies, this method can improve the electrostatic accumulation phenomenon of the separator, enhance battery manufacturing capabilities, improve separator adhesion and electrolyte wettability, and enable the battery to possess both high long-cycle performance, safety, and low self-discharge rate. To further improve the effect, one or more of these technical features can be further optimized.

[0036] In some embodiments, the adhesive layer is located on both sides of the carrier layer, and the thickness of the adhesive layer located on both sides of the carrier layer may be the same or different.

[0037] In some embodiments, the organic coating is located on one side of the substrate layer, and the adhesive layer is located on the surface of the organic coating and the other side of the substrate layer. The adhesive layer located on the surface of the organic coating is a first adhesive layer, and the adhesive layer located on the other side of the substrate layer is a second adhesive layer. The thickness of the first adhesive layer is less than the thickness of the second adhesive layer.

[0038] In some embodiments, the difference between the thickness of the second adhesive layer and the thickness of the first adhesive layer is 0.1 μm-0.8 μm (e.g., 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm or 0.8 μm).

[0039] In some embodiments, the Dv10 of the first particle is 0.05 μm-1 μm (e.g., 0.05 μm, 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm, 0.5 μm, 0.55 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm or 1 μm).

[0040] In this invention, Dv10 refers to the particle size corresponding to the cumulative particle size distribution of the first particle, arranged from smallest to largest, reaching 10%. In this invention, the Dv10 of the first particle can be obtained by testing with a laser particle size analyzer. For example, before preparing the diaphragm, the Dv10 of the first particle is measured using a laser particle size analyzer within 5 minutes after thorough stirring. Alternatively, the volumetric particle size distribution of the first particle can be obtained by arbitrarily selecting a 100μm × 100μm area from the SEM image of the diaphragm surface and performing measurement and statistical processing using image analysis software (e.g., ImageJ, NanoMeasurer, Matlab, ParticleMetric, etc.).

[0041] In some embodiments, the Dv50 of the second particle is 0.1 μm-1.2 μm (e.g., 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm or 1.2 μm).

[0042] In this invention, Dv50 refers to the particle size corresponding to 50% of the cumulative particle size distribution in the volumetric particle size distribution of the second particle. The Dv50 of the second particle can be obtained by testing with a laser particle size analyzer. For example, before preparing the diaphragm, the Dv50 of the organic particles can be measured using a laser particle size analyzer within 5 minutes after thorough stirring of the second particle. Alternatively, the volumetric particle size distribution of the second particle can be obtained by arbitrarily selecting a 100μm × 100μm area from the SEM image of the diaphragm surface and performing measurement and statistical processing using image analysis software (e.g., ImageJ, NanoMeasurer, Matlab, ParticleMetric, etc.).

[0043] According to one specific implementation, N 1 B is 0.05μm-1μm. 1 With a diameter of 0.1 μm to 1.2 μm, the diaphragm satisfies the following relationship: 1 ≤ B 1 / N 1 ≤15.

[0044] In some embodiments, the benzene ring in the bicyclic structure may or may not have substituents, wherein the substituents are selected from one or more of C1-C6 alkyl, C1-C6 alkoxy, hydroxy, amino, cyano, halogen substituents, sulfonic acid, carboxyl, and nitro groups.

[0045] In some embodiments, the bicyclic organic compound is 2-mercaptobenzimidazole or a 2-mercaptobenzimidazole derivative.

[0046] In some embodiments, the 2-mercaptobenzimidazole derivative includes one or more of the following: 2-mercapto-5-methylbenzimidazole, 2-mercapto-5-methoxybenzimidazole, 2-mercapto-5-ethoxybenzimidazole, 2-mercapto-5-hydroxybenzimidazole, 2-mercapto-5-aminobenzimidazole, 2-mercapto-5-chlorobenzimidazole, 2-mercapto-5-sulfonic acid benzimidazole, 2-mercapto-5-carboxybenzimidazole, 2-mercapto-5-nitrobenzimidazole, lithium salt of 2-thiolbenzimidazole, sodium salt of 2-thiolbenzimidazole, potassium salt of 2-thiolbenzimidazole, calcium salt of 2-thiolbenzimidazole, magnesium salt of 2-thiolbenzimidazole, aluminum salt of 2-thiolbenzimidazole, and ammonium salt of 2-thiolbenzimidazole.

[0047] In some embodiments, the weight percentage of the first particles in the organic coating is 75%-99% (e.g., 75%, 80%, 85%, 90%, 95% or 99%).

[0048] In some embodiments, the weight percentage of the first particle in the organic coating is 90%-98%.

[0049] In some embodiments, the organic coating further includes a first binder, wherein the weight percentage of the first binder in the organic coating is 1%-25% (e.g., 1%, 3%, 5%, 7%, 9%, 11%, 13%, 15%, 17%, 19%, 20%, 22% or 25%).

[0050] In some embodiments, the first adhesive accounts for 2%-10% of the weight of the organic coating.

[0051] In some embodiments, the first adhesive comprises one or more of polyvinyl alcohol, styrene-butadiene rubber, ethylene-vinyl acetate copolymer, sodium carboxymethyl cellulose, polyvinylpyrrolidone, styrene-acrylic latex, polyacrylonitrile, polyacrylic acid, polyvinyl acetate, acrylate adhesives, polyurethane, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, or copolymer systems derived from the above polymers.

[0052] In this invention, the acrylate adhesive includes one or more of polymethyl methacrylate, polybutyl acrylate, acrylate monomer-acrylonitrile copolymer, acrylate monomer-ethylene copolymer, acrylate monomer-acrylonitrile-ethylene copolymer, styrene-acrylate monomer-acrylonitrile 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. The acrylate monomer is selected from one or more of methyl acrylate, methyl methacrylate, ethyl acrylate, butyl acrylate, and ethyl methacrylate.

[0053] In some instances, the organic coating also includes filler particles, which account for 1%-24% of the total weight of the organic coating, for example, 1%, 3%, 5%, 8%, 10%, 15%, 18%, 20%, 22% or 24%.

[0054] In some instances, the organic coating comprises a first binder, organic particles, and filler particles, wherein, based on the total weight of the organic coating, the organic particles comprise 75%-99% (e.g., 75%, 80%, 85%, 90%, 95%, or 99%), the filler particles comprise 1%-24% (e.g., 1%, 3%, 5%, 7%, 9%, 11%, 13%, 15%, 17%, 19%, 21%, 23%, or 24%), and the first binder comprises 1%-10% (e.g., 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%).

[0055] In some instances, the filler particles comprise 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, poly(p-phenylene terephthalamide), poly(m-phenylene isophthalamide), phenolic resin, modified phenolic resin, 1,3,5-triazine-2,4,6-triamine, melamine thiocyanate, melamine cyanurate, symmetrical triaminotriazine, 2-(4-bromophenyl)- One or more of the following: 4,6-dimethyl-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, 4-amino-2,6-dihydroxypyrimidine, cytosine, guanine, uracil, and cytosine.

[0056] In some embodiments, the thickness of the organic coating is 0.2 μm-5 μm (e.g., 0.2 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm or 5 μm).

[0057] In some embodiments, the adhesive layer is applied continuously or discontinuously.

[0058] In some embodiments, the discontinuous coating is a striped coating, such as... Figure 4 As shown in Figure a, the spacing between two adjacent stripes is 50 μm-560 μm (e.g., 50 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, 450 μm, 500 μm, 550 μm, or 560 μm). In this invention, the spacing between two adjacent stripes refers to the average distance between the edge lines of two adjacent stripes.

[0059] In this invention, the spacing between two adjacent stripes is measured by the following method: arbitrarily select two adjacent stripes as a group, measure the distance between the edge lines of the two stripes as the spacing between the two stripes, arbitrarily select five groups of measured spacings, and calculate the arithmetic mean as the spacing between two adjacent stripes.

[0060] In some embodiments, the thickness of the adhesive layer on one side is 0.5μm-5μm (e.g., 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm or 5μm).

[0061] In some embodiments, the weight ratio of the polymer to the weight of the second particle is (3-19):(7-1) (e.g., 3:7, 4:6, 5:5, 6:4, 7:3, 8:2, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1 or 19:1).

[0062] It is understood that the weight percentage of the polymer can be in the range of 30%-95% (e.g., 30%, 40%, 50%, 60%, 70%, 80%, 90% or 95%), and the weight percentage of the second particle can be in the range of 70%-5% (e.g., 70%, 60%, 50%, 40%, 30%, 20%, 10% or 5%), but it is required that the sum of the weight percentage of the polymer and the weight percentage of the second particle is 100%.

[0063] In some embodiments, the polymer includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl fluoride, polyhexafluoropropylene, fluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, poly(p-phenylene terephthalamide), poly(m-phenylene isophthalamide), phenolic resin, and polyimide.

[0064] In some embodiments, the second particle comprises one or more of the following: 2-mercaptobenzimidazole, 2-mercaptobenzimidazole derivative, melamine cyanurate, melamine thiocyanate, melamine, melamine polyphosphate, uracil, cytosine, guanine, 4-amino-2,6-dihydroxypyrimidine, alumina, boehmite, barium sulfate, silicon dioxide, tin dioxide, titanium dioxide, barium titanate, magnesium oxide, boron nitride, and magnesium hydroxide.

[0065] In some embodiments, in the porous structure of the adhesive layer, the porous structure includes pores, and polymer fibers are present between the edges of the pores and adjacent pores, the polymer fibers having a diameter of 0.1 μm-0.3 μm (e.g., 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm or 0.3 μm).

[0066] In this invention, the diameter of the polymer fiber refers to the arithmetic mean of the diameters of any 100 polymer fibers in the adhesive layer. The diameter of the polymer fiber is measured by the following method: identifying and randomly selecting the diameters of 100 polymer fibers in the SEM image of the membrane adhesive layer surface. If the number of polymer fibers in a single image is insufficient, multiple images can be taken until the number of observed polymer fibers accumulates to 100. The arithmetic mean of the diameters of the 100 polymer fibers is then calculated, which is the diameter of the polymer fiber.

[0067] In some embodiments, on the surface of the adhesive layer, within an area of ​​arbitrarily selected at 100μm×100μm, the number of pores with a diameter greater than 1μm is 80-1500 (e.g., 80, 200, 400, 600, 800, 1000, 1200, 1400 or 1500).

[0068] By controlling the number of pores with a diameter greater than 1 μm within an area of ​​100 μm × 100 μm on the surface of the adhesive layer, the electrolyte storage space and good adhesion can be provided. On the one hand, this can improve the interfacial performance between the separator and the electrode, increase the lithium-ion transport rate, and improve the cycle performance of the battery. On the other hand, it can also reduce the friction between the adhesive layer and the electrode, reduce or even avoid static electricity generated by friction, thereby further reducing the K value.

[0069] In this invention, the number of pores with a diameter greater than 1 μm within an arbitrarily selected 100 μm × 100 μm area on the surface of the adhesive layer is measured by the following method: a microscopic image of the surface of the membrane adhesive layer is obtained using a scanning electron microscope (SEM); within an arbitrarily selected 100 μm × 100 μm area, the maximum distance between any two points on the edge line of a single pore is counted using image analysis software (e.g., ImageJ, NanoMeasurer, Matlab, ParticleMetric, etc.) as the diameter of the pore; and the number of pores with a diameter greater than 1 μm is counted.

[0070] In some embodiments, on the surface of the adhesive layer, within an area of ​​arbitrarily selected at 100μm×100μm, the number of pores with a diameter greater than 1μm is 100-1000.

[0071] In some embodiments, the solubility of the first particle in a polar solvent is less than or equal to 5% (e.g., 0.1%, 1%, 2%, 3%, 4%, or 5%), wherein the polar solvent is selected from one or more of N-methylpyrrolidone and N,N-dimethylacetamide. Controlling the solubility of the first particle in the polar solvent to be less than or equal to 5% is beneficial for further improving the interfacial stability of the organic coating and the adhesive layer. When the solubility of the first particle in the polar solvent is greater than 5%, the solubility of the first particle is too high, making it easy to lose the first particle during the membrane preparation process. At the same time, it leads to a decrease in the packing density of the organic coating, which is not conducive to further improvement of the thermal stability and electrostatic accumulation of the membrane.

[0072] In this invention, the solubility of the first particle in a polar solvent is measured by the following method: the first particle is weighed and recorded as g. 1 Add the first particle to a sufficient amount of polar solvent (enough to submerge the first particle), let it stand at room temperature (e.g., 25℃±2℃) for 24 hours, filter to remove the polar solvent, dry in an oven at 150℃, and then weigh again as g. 2 Then the solubility = [(g 1 -g 2 ) / g 1 ]×100%.

[0073] In some embodiments, the puncture strength of the substrate layer is 200gf-500gf (e.g., 200gf, 250gf, 300gf, 350gf, 400gf, 450gf, or 500gf). Controlling the puncture strength of the substrate layer within the above range is beneficial for enhancing the membrane's resistance to foreign object puncture, further reducing or even avoiding membrane puncture caused by electrostatic accumulation and adsorption of impurities, reducing the risk of internal short circuits, and improving the long-cycle stability and safety of the battery. When the puncture strength of the substrate layer is below 200gf, it is not conducive to resisting foreign object puncture; when the puncture strength of the substrate layer is above 500gf, it is easy to lose the closed-cell characteristics of the membrane at high temperatures, increasing the risk of thermal runaway of the battery.

[0074] In this invention, the puncture strength 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 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 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 puncture strength of the substrate layer.

[0075] In some embodiments, the porosity of the substrate layer is 30%-60% (e.g., 30%, 35%, 40%, 45%, 50%, 55%, or 60%). Controlling the porosity of the substrate layer within the above range can further improve the electrolyte wettability of the separator, which is beneficial for lithium-ion transport, enhances the interfacial performance between the separator and the electrode, and further improves the long-cycle performance of the battery. When the porosity of the substrate layer is less than 30%, it is not conducive to lithium-ion conduction, thus hindering further improvement in the battery's cycle performance. When the porosity of the substrate layer is greater than 60%, it further increases the risk of self-discharge, increases the self-discharge rate, and is not conducive to further improvement in the battery's long-cycle performance, nor is it conducive to the long-term storage of the battery.

[0076] 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.

[0077] In some embodiments, the pore size of the substrate layer is 20nm-75nm (e.g., 20nm, 30nm, 40nm, 50nm, 60nm, 70nm or 75nm).

[0078] In some embodiments, the average pore size of the substrate layer is 30nm-50nm (e.g., 30nm, 35nm, 40nm, 45nm or 50nm).

[0079] 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.

[0080] In some embodiments, the thickness of the substrate layer is 3μm-16μm (e.g., 3μm, 5μm, 7μm, 9μm, 11μm, 13μm, 15μm or 16μm).

[0081] In some embodiments, the thickness of the substrate layer is 4μm-10μm.

[0082] In some embodiments, the substrate layer comprises one or more of the following polymer derivatives: polyolefin, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinyl chloride, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyethylene terephthalate, polybutylene terephthalate, poly(p-phenylene terephthalamide), poly(m-phenylene isophthalamide), or poly(m-phenylene isophthalamide).

[0083] In some embodiments, the substrate layer is a polyolefin substrate layer, and the components of the polyolefin substrate layer include one or more of polyethylene, modified polyethylene, polypropylene, and modified polypropylene.

[0084] In some embodiments, the polyolefin substrate layer is a three-layer composite structure, which includes a top layer, a middle layer, and a bottom layer.

[0085] In some embodiments, the intermediate layer is composed of polyethylene (PE), the top layer is composed of polypropylene (PP), and the bottom layer is composed of polypropylene (PP).

[0086] In some embodiments, the intermediate layer is composed of polypropylene (PP), the top layer is composed of polyethylene (PE), and the bottom layer is composed of polyethylene (PE).

[0087] 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.

[0088] In some embodiments, in the separator, the organic coating is located on one side of the substrate layer, and the adhesive layer is located on the surface of the organic coating and the surface of the substrate layer on the other side. The adhesive layer located on one side of the organic coating is a first adhesive layer, and the adhesive layer located on one side of the substrate layer is a second adhesive layer. The positive electrode corresponds to the side of the separator where the organic coating exists, and the negative electrode corresponds to the other side of the separator. The thickness of the first adhesive layer is less than the thickness of the second adhesive layer.

[0089] The surface of the electrode sheet is rough and filled with active material particles. If the adhesive layers on both sides of the separator are inconsistent in hardness and thickness, it will lead to different adhesion between the separator and the positive and negative electrodes. The harder side may not be able to fully embed into the micro-pits of the electrode, resulting in a reduction in the actual contact area between the separator and the electrode. The separator of the present invention, by precisely controlling the thickness of the adhesive layers on both sides of the separator, makes the thickness of the first adhesive layer less than that of the second adhesive layer, and at the same time makes the adhesive layers with different surface properties on both sides correspond to the positive and negative electrodes respectively, which can further improve the interface performance between the separator and the electrode and further reduce the K value of the battery during long-cycle processes. Specifically, the thicker second adhesive layer is relatively softer and has better adhesion. When the relatively thicker second adhesive layer is matched with the negative electrode, the second adhesive layer can better fill the voids on the surface of the negative electrode. Moreover, the second adhesive layer can also provide more compressible space for the expansion of silicon-based particles in the negative electrode, thereby making the second electrode more flexible and adaptable to the electrode. The adhesive layer can achieve more uniform contact with the negative electrode, reducing or even avoiding the risk of excessive local current density, thereby further improving long-cycle performance and further reducing the K value. Moreover, the thicker second adhesive layer can give it higher density and physical properties, resulting in a smoother surface. A smooth surface can reduce triboelectricity, thus further reducing electrostatic adsorption. On one side of the thinner first adhesive layer, there is an organic coating. The bicyclic organic matter in the organic coating can improve the problem of electrostatic accumulation. Furthermore, reducing the thickness of the first adhesive layer on the surface of the organic coating is beneficial to improving the overall flexibility and fit of the diaphragm.

[0090] In some embodiments, the difference between the thickness of the second adhesive layer and the thickness of the first adhesive layer is 0.1 μm-0.8 μm (e.g., 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm or 0.8 μm).

[0091] Furthermore, by controlling the difference between the thickness of the second adhesive layer and the thickness of the first adhesive layer within the aforementioned range, the problem of increased self-discharge rate during battery cycling can be further improved, the interface performance between the separator and the positive and negative electrodes can be further enhanced, and the long-cycle stability of the battery can be improved.

[0092] In some embodiments, the negative electrode sheet includes a negative current collector and a negative active layer located on one or both sides of the negative current collector. The negative active layer includes a silicon-based material, which includes one or more of elemental silicon, silicon-oxygen, silicon-carbon, silicon-nitrogen composite, and silicon alloy materials.

[0093] In some embodiments, the average particle size of the silicon-carbon material is 5 μm-12 μm (e.g., 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, or 12 μm). Controlling the average particle size of the silicon-carbon material within the above range can reduce or even prevent abnormally large particles or detached active material caused by uneven particle size from piercing the separator during volume changes in the silicon-based material, further reducing the battery's self-discharge rate.

[0094] In this invention, the average particle size of the silicon-carbon material can be measured by the following method: before preparing the negative electrode, the average particle size of the silicon-carbon material is measured using a laser particle size analyzer within 5 minutes after thorough stirring. Alternatively, the average particle size of the silicon-carbon material can be determined by randomly selecting 100 silicon-carbon materials (100 μm × 100 μm) from an SEM image of the negative electrode surface, drawing a rectangle or square with the smallest area completely surrounding each particle (i.e., a rectangle or square tangent to the four sides of the particle's edge). The arithmetic mean of the length of the long side and the short side of the rectangle, or the length of any side of the square, is the particle size of that single particle. If the number of particles in a single image is insufficient, multiple images can be taken until the observed number of particles reaches 100. The arithmetic mean of the particle sizes of these 100 silicon-carbon materials is then calculated as the average particle size of the silicon-carbon material.

[0095] In some embodiments, the negative electrode active layer further includes a carbon-based material, a negative electrode conductive agent, and a negative electrode binder.

[0096] In some embodiments, the carbon-based material includes one or more of artificial graphite, natural graphite, soft carbon, and hard carbon.

[0097] In some embodiments, the negative electrode conductive agent includes one or more of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, carbon nanotubes, metal powder, and carbon fiber.

[0098] In some embodiments, the negative electrode binder further includes one or more of styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polyurethane, polyacrylonitrile, acrylate adhesives, polytetrafluoroethylene (PTFE), lithium polyacrylate (PAALi), polyacrylic acid (PAA), sodium polymethyl cellulose (CMC-Na), and lithium polymethyl cellulose (CMC-Li).

[0099] In some embodiments, in the negative electrode active layer, the weight percentage of the silicon-based material is 1%-95% (e.g., 1%, 10%, 18%, 20%, 26%, 30%, 40%, 44%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%), the weight percentage of the carbon-based material is 45%-94% (e.g., 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 94%), the weight percentage of the negative electrode conductive agent is 0-8% (e.g., 0%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, or 8%), and the weight percentage of the negative electrode binder is 0.5%-18% (e.g., 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, or 18%). When the weight content of the negative electrode conductive agent in the negative electrode active layer is 0, it means that the negative electrode conductive agent does not exist.

[0100] In some embodiments, the positive electrode sheet includes a positive current collector and a positive active layer located on at least one side of the surface of the positive current collector. The positive active layer is not particularly limited and may include a positive active material, a positive conductive agent, and a positive binder in accordance with conventional compositions in the art.

[0101] In this invention, the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder can all be selected from conventional materials in the art.

[0102] In some embodiments, the positive electrode active material may be selected from one or more of lithium nickel 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 embodiments, the positive electrode conductive agent may be selected from one or more of conductive carbon black, carbon nanotubes, conductive graphite, and graphene.

[0104] In some embodiments, the positive electrode binder may be selected from one or more of polyvinylidene fluoride (PVDF), acrylic modified PVDF, acrylate adhesives, acrylic polymers, polytetrafluoroethylene, polyacrylonitrile, polyimide, styrene-butadiene rubber, and styrene-acrylic rubber.

[0105] In some embodiments, the electrolyte may be a conventional electrolyte in the art, for example, the electrolyte may include lithium salts, organic solvents and additives.

[0106] In some embodiments, the lithium salt includes at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0107] In some embodiments, the organic solvent includes at least one of ethylene carbonate, 2,2-difluoroethyl acetate, ethyl 2,2-difluoroethyl acetate, propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), and ethyl butyrate (EB).

[0108] In some embodiments, the additive includes at least one of nitrile compounds, fluorocarbonates, fluorocarboxylic esters, and sulfur-containing compounds.

[0109] In some instances, based on the total weight of the electrolyte, the lithium salt comprises 5%-40% by weight (e.g., 5%, 10%, 15%, 20%, 25%, 30%, or 40%), the organic solvent comprises 10%-85% by weight (e.g., 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or 85%), and the additive comprises 0%-50% by weight (e.g., 0, 0.1%, 0.5%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, or 50%). When the weight percentage of the additive in the electrolyte is 0%, it indicates that the electrolyte contains no additive.

[0110] In some instances, the battery is a lithium-ion rechargeable battery.

[0111] 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.

[0112] 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.

[0113] Example 1

[0114] (1) Preparation of positive electrode

[0115] Lithium cobalt oxide, positive electrode binder (polyvinylidene fluoride 500), and positive electrode conductive agent (carbon black: carbon nanotubes = 1:1) were mixed in N-methylpyrrolidone (NMP) solvent at a weight ratio of 96:2:2 and continuously stirred under the action of a stirrer to form a homogeneous and fluid positive electrode slurry. Subsequently, the positive electrode slurry was coated on both sides of an aluminum foil with a thickness of 10 μm and dried in a vacuum oven at 120°C for 6 hours. Then, it was rolled and slit to obtain the desired positive electrode sheet.

[0116] (2) Preparation of negative electrode

[0117] Graphite, silicon carbide material (average particle size 8 μm), negative electrode conductive agent (carbon black: carbon nanotubes = 1:1), sodium carboxymethyl cellulose, and negative electrode binder (styrene-butadiene rubber: polyacrylic acid = 1:1) were mixed in an aqueous solvent at a weight ratio of 89:8:1:0.5:1.5 and continuously stirred under the action of a stirrer to form a homogeneous and fluid negative electrode slurry. Subsequently, the slurry was coated on both sides of a 10 μm thick copper foil and dried in a vacuum oven at 120°C for 6 hours. Then, after rolling and slitting, the desired negative electrode sheet was obtained.

[0118] (3) Electrolyte preparation

[0119] In an argon-filled glove box (moisture content <1 ppm, oxygen content <1 ppm), ethylene carbonate, propylene carbonate, propyl propionate, and ethyl propionate solvents are mixed in a weight ratio of 15:15:50:20 to form a homogeneous solvent. 16% LiPF6, 3% 1,3,6-hexanetrionitrile, and 20% fluoroethylene carbonate are slowly added based on the total weight of the electrolyte. After stirring until homogeneous, the desired lithium-ion battery electrolyte is obtained.

[0120] (4) Preparation of the diaphragm

[0121] The first particle (a bicyclic organic compound, 2-mercaptobenzimidazole) and the first binder (polymethyl methacrylate) were mixed and dispersed in deionized water at a weight ratio of 90:10. After stirring evenly, a mixed slurry with a solid content of 25% was obtained. This slurry was coated onto one side of the substrate layer using a gravure roller and then dried and set in a multi-section oven at 60°C to obtain an organic coating with a thickness of 2 μm. The Dv10 of the first particle was 0.2 μm (N). 1 The solubility of the first particle in the polar solvent N,N-dimethylacetamide is 3% (0.2%).

[0122] Then, the second particle (2-mercaptobenzimidazole) and polymer (polyvinylidene fluoride) were mixed and dispersed in N,N-dimethylacetamide at a weight ratio of 30:70. After stirring evenly, a mixed slurry with a solid content of 10% was obtained. The mixed slurry was continuously coated onto the side of the organic coating away from the polyethylene (PE, substrate layer) and the other side of the substrate layer using a gravure roller. Then, it was dried and shaped in a multi-section oven at a temperature of 60°C to obtain a first adhesive layer on the surface of the organic coating and a second adhesive layer on the surface of the substrate layer. The Dv50 of the second particle was 0.3 μm (B 1 (0.3), B 1 / N 1 =0.3 / 0.2=1.5, the weight ratio of the polymer to the second particle is 7:3, the adhesive layer is continuously coated, the diameter of the polymer fiber is 0.2μm, on the surface of the adhesive layer, within an arbitrarily selected area of ​​100μm×100μm, the number of pores with a diameter greater than 1μm is 800, the thickness of the first adhesive layer is 2μm, the thickness of the second adhesive layer is 2.5μm, the difference between the thickness of the second adhesive layer and the thickness of the first adhesive layer is 0.5μm, the thickness of the first adhesive layer is less than the thickness of the second adhesive layer, the puncture strength of the substrate layer is 300gf, the porosity of the substrate layer is 45%, the average pore size of the substrate layer is 42nm, and the thickness of the substrate layer is 8μm.

[0123] The positive electrode, negative electrode, separator, and electrolyte prepared above are subjected to winding, vacuum packaging, room temperature standing, and high temperature formation processes to obtain the desired lithium-ion battery. The positive electrode corresponds to the side of the separator with the organic coating, and the negative electrode corresponds to the second adhesive layer in the separator.

[0124] Example 2 group

[0125] This set of examples illustrates the effects of changes in the diaphragm structure.

[0126] Example 2-1

[0127] The procedure was carried out in accordance with Example 1, except that the side of the separator with the organic coating corresponds to the negative electrode.

[0128] Example 2-2

[0129] The procedure was carried out in accordance with Example 1, except that the organic coating was located on both sides of the substrate layer, and the adhesive layer was located on the surface of the organic coating. The first adhesive layer corresponds to the positive electrode sheet, and the second adhesive layer corresponds to the negative electrode sheet.

[0130] Example 3 Group

[0131] This set of examples illustrates the effects of changes in the composition of the first particle (specific selection of the bicyclic organic compound).

[0132] Example 3-1

[0133] The procedure was carried out in accordance with Example 1, except that the first particle was composed of 2-mercapto-5-methylbenzimidazole, the solubility of the first particle in a polar solvent was 4.2%, and the average particle size of the silicon carbide material was 5 μm.

[0134] Example 3-2

[0135] The experiment was conducted in accordance with Example 1, except that the first particle was composed of 2-thiol-benzimidazole zinc salt, the solubility of the first particle in a polar solvent was 1.6%, and the average particle size of the silicon-carbon material was 12 μm.

[0136] Example 4 group

[0137] This set of examples is used to illustrate when B 1 / N 1 The impact of changes.

[0138] Example 4-1

[0139] The procedure was carried out in accordance with Example 1, except that the Dv10 of the first particle was 1 μm (N). 1 The second particle has a Dv50 of 1 μm (B). 1 (1), B 1 / N 1 =1 / 1=1.

[0140] Example 4-2

[0141] The procedure was carried out in accordance with Example 1, except that the Dv10 of the first particle was 0.08 μm (N). 1 The first particle has a Dv50 of 0.08, while the second particle has a Dv50 of 1.2 μm (B). 1 (1.2), B 1 / N 1 =1.2 / 0.08=15.

[0142] Example 4-3

[0143] The procedure was carried out in accordance with Example 1, except that the Dv10 of the first particle was 0.03 μm (N). 1 The first particle has a Dv50 of 0.03, while the second particle has a Dv50 of 0.05 μm (B). 1 (0.05), B 1 / N 1 =0.05 / 0.03=1.67.

[0144] Example 4-4

[0145] The procedure was carried out in accordance with Example 1, except that the Dv10 of the first particle was 1.2 μm (N). 1 The second particle has a Dv50 of 1.3 μm (B). 1 (1.3), B 1 / N 1 =1.3 / 1.2=1.08.

[0146] Example 5 group

[0147] This set of examples illustrates the effects of changes in the thickness of the organic coating.

[0148] This embodiment group is based on Embodiment 1, except that the thickness of the organic coating is changed, as detailed in Table 1.

[0149] Table 1

[0150]

[0151] Example 6 group

[0152] This set of examples illustrates the effects that occur when the difference between the thickness of the second adhesive layer and the thickness of the first adhesive layer changes.

[0153] This embodiment is based on Embodiment 5-1, except that the difference between the thickness of the second adhesive layer and the thickness of the first adhesive layer is changed, as detailed in Table 2.

[0154] Table 2

[0155]

[0156] The " / " indicates that the data does not exist.

[0157] Example 7 group

[0158] This set of examples illustrates the effects of changes in the spacing between two adjacent stripes when the adhesive layer is coated and / or striped.

[0159] This embodiment group is carried out in accordance with Embodiment 1, except that the obtained adhesive layer mixture slurry is discontinuously coated onto the surface of the organic coating and the other side of the substrate layer using a gravure roller, resulting in a striped adhesive layer coating, such as... Figure 4 As shown, the spacing between two adjacent stripes changes, as detailed in Table 3.

[0160] Table 3

[0161]

[0162] Example 8 group

[0163] This set of examples illustrates the effects of a change in the ratio of the weight of the polymer to the weight of the second particle.

[0164] Example 8-1

[0165] This embodiment group is carried out with reference to Embodiment 7-1, except that in the adhesive layer, the weight ratio of the polymer is 25% and the weight ratio of the second particle is 75%, and the weight ratio of the polymer to the second particle is 1:3.

[0166] Example 8-2

[0167] This embodiment group is carried out with reference to Embodiment 7-1, except that in the adhesive layer, the weight ratio of the polymer is 98% and the weight ratio of the second particle is 2%, and the weight ratio of the polymer to the second particle is 49:1.

[0168] Example 9 group

[0169] This set of examples illustrates the effects of changing the diameter of the polymer fibers in the adhesive layer and / or the number of pores with a diameter greater than 1 μm within an arbitrarily selected area of ​​100 μm × 100 μm on the surface of the adhesive layer.

[0170] Example 9-1

[0171] This embodiment group is based on Example 1, except that the diameter of the polymer fiber is 0.1 μm, and the number of pores with a diameter greater than 1 μm is 80 in any 100 μm × 100 μm area on the surface of the adhesive layer.

[0172] Example 9-2

[0173] This embodiment group is based on Example 1, except that the diameter of the polymer fiber is 0.3 μm, and the number of pores with a diameter greater than 1 μm is 1500 within an area of ​​arbitrarily selected 100 μm × 100 μm on the surface of the adhesive layer.

[0174] Example 9-3

[0175] This embodiment group is based on Example 1, except that the diameter of the polymer fiber is 0.08 μm, and the number of pores with a diameter greater than 1 μm is 60 within an area of ​​arbitrarily selected 100 μm × 100 μm on the surface of the adhesive layer.

[0176] Example 9-4

[0177] This embodiment group is based on Example 1, except that the diameter of the polymer fiber is 0.4 μm, and the number of pores with a diameter greater than 1 μm is 1543 in any 100 μm × 100 μm area on the surface of the adhesive layer.

[0178] Example 10 group

[0179] This set of examples illustrates the effects of changes in the puncture strength and / or porosity of the substrate layer.

[0180] This embodiment group is carried out with reference to Embodiment 1, except that the puncture strength and / or porosity of the substrate layer are changed, as detailed in Table 4.

[0181] Table 4

[0182]

[0183] Example 11 group

[0184] This set of examples illustrates the effects of changes in the average particle size of silicon-carbon materials.

[0185] This embodiment group is carried out with reference to Example 3-1, except that the average particle size of the silicon-carbon material is 3μm.

[0186] This embodiment group is based on Example 3-1, except that the average particle size of the silicon-carbon material is 13.2 μm.

[0187] Comparative Example 1

[0188] This comparative example is based on Example 1, except that the diaphragm does not include an organic coating, but only a substrate layer and an adhesive layer.

[0189] Comparative Example 2

[0190] This comparative example is based on Example 1, except that the bicyclic organic compound is replaced with boehmite.

[0191] Comparative Example 3

[0192] This comparative example is based on Example 1, except that the bicyclic organic compound is replaced with a mixture of 2-mercaptoimidazole and tetramercaptobenzene.

[0193] Comparative Example 4

[0194] This comparative example is based on Example 1, except that the diaphragm does not include an adhesive layer, but only includes a substrate layer and an organic coating.

[0195] Comparative Example 5

[0196] This comparative example is based on Example 1, except that the Dv10 of the first particle is 0.12 μm (N). 1 The first particle has a Dv50 of 0.12, while the second particle has a Dv50 of 0.1 μm (B). 1 (0.1), B 1 / N 1 =0.1 / 0.12=0.83.

[0197] Comparative Example 6

[0198] This comparative example is based on Example 1, except that the Dv10 of the first particle is 0.05 μm (N). 1 The first particle has a Dv50 of 0.05, while the second particle has a Dv50 of 0.9 μm (B). 1 (0.9), B 1 / N 1 =0.9 / 0.0.05=18.

[0199] Test case

[0200] The batteries prepared in the examples and comparative examples were subjected to the following performance tests, and the test results are shown in Table 5:

[0201] (1) Capacity retention rate during 25℃ cycling:

[0202] At 25℃±2℃, the battery was charged at a constant current and constant voltage of 0.7C to the upper limit voltage of 4.5V, then cut off at 0.05C, and then discharged at a constant current of 0.2C to the lower limit voltage of 3V. The initial discharge capacity is denoted as C. 1 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 the upper limit voltage of 4.5V, cut off at 0.18C, rest for 5 minutes, and then discharge at 0.7C to the lower limit voltage of 3V. After 800 cycles, 0.7C constant current / constant voltage charging is performed to the upper limit voltage of 4.5V, cut off at 0.05C, and then 0.2C constant current discharge is performed to the lower limit voltage of 3V. The final discharge capacity is recorded as C. 2 Capacity retention rate: C = (C 2 / C 1 )×100%.

[0203] (2) Capacity retention rate during 45℃ cycling:

[0204] At 45℃, the battery is charged at a constant current and constant voltage of 0.5C to the upper limit voltage of 4.5V, then cut off at 0.05C, and then discharged at a constant current of 0.2C to the lower limit voltage of 3.0V. The initial discharge capacity is denoted as C. 2 After 10 minutes of rest, the cycle is as follows: 1C constant current / constant voltage charging to 4.25V, cutoff at 0.7C, then 0.7C constant current / constant voltage charging to 4.48V, cutoff at 0.2C, then 0.2C constant current / constant voltage charging to the upper limit voltage of 4.5V, cutoff at 0.05C, rest for 5 minutes, then discharge at 0.2C to the lower limit voltage of 3.0V. After 500 cycles, 0.5C constant current / constant voltage charging to the upper limit voltage of 4.5V, cutoff at 0.05C, then 0.2C constant current discharging to the lower limit voltage of 3V. The final discharge capacity is recorded as C. 3 Capacity retention rate: C = (C 3 / C 2 )×100%.

[0205] (3) Furnace temperature test at 130℃:

[0206] Suspend a fully charged battery in a circulating air oven at 25℃ (heat transfer is not allowed on non-integral battery modules). Ensure that the voltage and temperature leads are properly insulated (to avoid short circuits). Start at room temperature (25℃) and increase the temperature to 130℃±2℃ at a rate of (5±2)℃ / min. Place the battery at 130℃±2℃ for 60 minutes and observe whether it catches fire or explodes. If the battery does not catch fire or explode, the oven temperature test is considered passed. If the battery catches fire or explodes, the oven temperature test is considered failed. Test 20 samples, record the number of batteries that pass as X, and record the result as "X / 20".

[0207] (4) Determination of K value:

[0208] The open-circuit potential of the lithium-ion batteries after sorting is measured to obtain V. 1 After standing for 24 hours, the open-circuit potential of the battery was measured again to obtain V. 2 , with V 1 Subtract V 2 The difference is then divided by the resting time to obtain the battery's K value.

[0209] Table 5

[0210]

[0211]

[0212] The " / " indicates that the data does not exist.

[0213] As shown in Table 5, by comparing the comparative examples and the embodiments, the embodiments show improved capacity retention during room temperature cycling, improved capacity retention during high temperature cycling, and a significant decrease in the K value. This indicates that by setting an organic coating and an adhesive layer on the diaphragm surface and controlling the diaphragm to satisfy the relationship: 1≤B 1 / N 1 ≤15, which reduces the static buildup of the separator, improves the battery manufacturing process, enhances the separator's adhesion and electrolyte wettability, and enables the battery to have both high cycle performance, safety and low self-discharge rate.

[0214] 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 in that, The separator includes a carrier layer and an adhesive layer located on at least one surface of the carrier layer. The carrier layer includes a substrate layer and an organic coating located on at least one surface of the substrate layer. The organic coating includes first particles, the first particles being composed of a bicyclic organic compound. The molecular structure of the bicyclic organic compound includes a bicyclic structure formed by a 2-mercaptoimidazole ring sharing two adjacent carbon atoms and a benzene ring. The adhesive layer has a porous structure and includes a polymer forming the porous structure and second particles. The separator satisfies the following relationship: 1 ≤ B 1 / N 1 ≤15, where B 1 The Dv50 of the second particle is expressed in μm and N. 1 The first particle's Dv10 is in μm, and the first particle's Dv10 is 0.05μm-1μm, and / or the second particle's Dv50 is 0.1μm-1.2μm.

2. The diaphragm according to claim 1, wherein, The benzene ring in the bicyclic structure may or may not have substituents, and the substituents are selected from one or more of C1-C6 alkyl, C1-C6 alkoxy, hydroxy, amino, cyano, halogen substituents, sulfonic acid, carboxyl and nitro groups; And / or, the weight ratio of the polymer to the weight of the second particle is (3-19):(7-1); And / or, the adhesive layer may be continuously coated or discontinuously coated.

3. The diaphragm according to claim 1, wherein, The bicyclic organic compound is 2-mercaptobenzimidazole or a 2-mercaptobenzimidazole derivative; And / or, the polymer includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl fluoride, polyhexafluoropropylene, fluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, poly(p-phenylene terephthalamide), poly(m-phenylene isophthalamide), phenolic resin, and polyimide. And / or, the weight percentage of the first particles in the organic coating is 75%-99%; And / or, the organic coating further includes a first binder, wherein the weight percentage of the first binder in the organic coating is 1%-25%; And / or, the thickness of the organic coating is 0.2 μm-5 μm; And / or, the thickness of the adhesive layer on one side is 0.5μm-5μm; And / or, the adhesive layer is located on both sides of the carrier layer, and the thickness of the adhesive layer located on both sides of the carrier layer is the same or different.

4. The diaphragm according to claim 3, wherein, In the organic coating, the weight percentage of the first particle is 90%-98%; And / or, the weight percentage of the first adhesive in the organic coating is 2%-10%; And / or, the 2-mercaptobenzimidazole derivatives include one or more of the following: 2-mercapto-5-methylbenzimidazole, 2-mercapto-5-methoxybenzimidazole, 2-mercapto-5-ethoxybenzimidazole, 2-mercapto-5-hydroxybenzimidazole, 2-mercapto-5-aminobenzimidazole, 2-mercapto-5-chlorobenzimidazole, 2-mercapto-5-sulfonic acid benzimidazole, 2-mercapto-5-carboxybenzimidazole, 2-mercapto-5-nitrobenzimidazole, lithium salt of 2-thiolbenzimidazole, sodium salt of 2-thiolbenzimidazole, potassium salt of 2-thiolbenzimidazole, calcium salt of 2-thiolbenzimidazole, magnesium salt of 2-thiolbenzimidazole, aluminum salt of 2-thiolbenzimidazole, and ammonium salt of 2-thiolbenzimidazole. And / or, the first adhesive comprises one or more of the following: polyvinyl alcohol, styrene-butadiene rubber, ethylene-vinyl acetate copolymer, sodium carboxymethyl cellulose, polyvinylpyrrolidone, styrene-acrylic latex, polyacrylonitrile, polyacrylic acid, polyvinyl acetate, acrylate adhesives, polyurethane, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, or copolymer systems derived from the above polymers. And / or, the organic coating is located on one side of the substrate layer, and the adhesive layer is located on the surface of the organic coating and the other side of the substrate layer. The adhesive layer located on the surface of the organic coating is the first adhesive layer, and the adhesive layer located on the other side of the substrate layer is the second adhesive layer. The thickness of the first adhesive layer is less than the thickness of the second adhesive layer.

5. The diaphragm according to claim 1, wherein, The second particle comprises one or more of the following: 2-mercaptobenzimidazole, 2-mercaptobenzimidazole derivatives, melamine cyanurate, melamine thiocyanate, melamine, melamine polyphosphate, uracil, cytosine, guanine, 4-amino-2,6-dihydroxypyrimidine, alumina, boehmite, barium sulfate, silicon dioxide, tin dioxide, titanium dioxide, barium titanate, magnesium oxide, boron nitride, and magnesium hydroxide.

6. The diaphragm according to claim 5, wherein, In the organic coating, the weight percentage of the first particle is 90%-98%; And / or, the 2-mercaptobenzimidazole derivatives include one or more of the following: 2-mercapto-5-methylbenzimidazole, 2-mercapto-5-methoxybenzimidazole, 2-mercapto-5-ethoxybenzimidazole, 2-mercapto-5-hydroxybenzimidazole, 2-mercapto-5-aminobenzimidazole, 2-mercapto-5-chlorobenzimidazole, 2-mercapto-5-sulfonic acid benzimidazole, 2-mercapto-5-carboxybenzimidazole, 2-mercapto-5-nitrobenzimidazole, lithium salt of 2-thiolbenzimidazole, sodium salt of 2-thiolbenzimidazole, potassium salt of 2-thiolbenzimidazole, calcium salt of 2-thiolbenzimidazole, magnesium salt of 2-thiolbenzimidazole, aluminum salt of 2-thiolbenzimidazole, and ammonium salt of 2-thiolbenzimidazole. And / or, the organic coating is located on one side of the substrate layer, and the adhesive layer is located on the surface of the organic coating and the other side of the substrate layer. The adhesive layer located on the surface of the organic coating is the first adhesive layer, and the adhesive layer located on the other side of the substrate layer is the second adhesive layer. The thickness of the first adhesive layer is less than the thickness of the second adhesive layer.

7. The diaphragm according to claim 4, wherein, The difference between the thickness of the second adhesive layer and the thickness of the first adhesive layer is 0.1 μm-0.8 μm.

8. The diaphragm according to claim 1, wherein, In the porous structure of the adhesive layer, the porous structure includes pores, and polymer fibers exist between the edges of the pores and adjacent pores, the diameter of the polymer fibers being 0.1μm-0.3μm; And / or, on the surface of the adhesive layer, within an area of ​​arbitrarily selected from 100μm×100μm, the number of pores with a diameter greater than 1μm is 80-1500.

9. The diaphragm according to any one of claims 1-8, wherein, The solubility of the first particle in a polar solvent is less than or equal to 5%, and the polar solvent is selected from one or more of N-methylpyrrolidone and N,N-dimethylacetamide; And / or, the puncture strength of the substrate layer is 200gf-500gf; And / or, the porosity of the substrate layer is 30%-60%; And / or, the pore size of the substrate layer is 20nm-75nm; And / or, the average pore size of the substrate layer is 30nm-50nm; And / or, the thickness of the substrate layer is 3μm-16μm; And / or, the composition of the substrate layer includes one or more of the following polymer derivatives: polyolefin, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinyl chloride, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyethylene terephthalate, polybutylene terephthalate, poly(p-phenylene terephthalamide), poly(m-phenylene isophthalamide), or poly(m-phenylene isophthalamide).

10. A battery, characterized in that, The battery includes a positive electrode, a negative electrode, and a separator according to any one of claims 1-9, wherein the separator is located between the positive electrode and the negative electrode.

11. The battery according to claim 10, wherein, In the separator, the organic coating is located on one side of the substrate layer, and the adhesive layer is located on the surface of the organic coating and the surface of the substrate layer on the other side. The adhesive layer located on one side of the organic coating is the first adhesive layer, and the adhesive layer located on one side of the substrate layer is the second adhesive layer. The positive electrode corresponds to the side of the separator where the organic coating exists, and the negative electrode corresponds to the other side of the separator. The thickness of the first adhesive layer is less than the thickness of the second adhesive layer. And / or, the negative electrode sheet includes a negative current collector and a negative active layer located on one or both sides of the negative current collector surface, the negative active layer including a silicon-based material, the silicon-based material including one or more of elemental silicon material, silicon-oxygen material, silicon-carbon material, silicon-nitrogen composite material, and silicon alloy material.

12. The battery according to claim 11, wherein, The thickness difference between the second adhesive layer and the first adhesive layer is 0.1 μm-0.8 μm; And / or, the negative electrode sheet includes a negative current collector and a negative active layer located on one or both sides of the surface of the negative current collector, the negative active layer including silicon-carbon material, the silicon-carbon material having an average particle size of 5μm-12μm.

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