Diaphragm and battery

Abstract

The invention relates to the technical field of batteries, in particular to a diaphragm and a battery. The diaphragm comprises a carrier layer and a gluing layer, the carrier layer comprises a base material layer and an organic coating, the organic coating comprises organic particles containing bicyclic organic matter, and the bicyclic organic matter comprises a bicyclic structure formed by a 2-mercaptoimidazole ring and a benzene ring sharing two adjacent carbon atoms; the glued layer includes a first glued layer including first polymer particles and a second glued layer including a porous structure formed of a second polymer. A certain gap can be formed between the diaphragm and the pole piece, and in the normal charging and discharging process, a space is provided for storage of an electrolyte and a channel is provided for flowing of the electrolyte between the pole piece and the diaphragm, so that the lithium precipitation condition of the battery under high magnification is improved and even avoided, and the service life of the battery is prolonged. Meanwhile, the diaphragm disclosed by the invention can also reduce and even prevent the damage of cobalt ions to the SEI membrane, and the high-temperature cycle performance of the battery is improved.

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] Lithium-ion batteries are iteratively developing towards higher energy density and higher rate of operation to meet market demands for long battery life and fast charging in electronic devices. Using silicon-based anode materials can effectively improve battery energy density. However, due to the significant volume change of the silicon-based material during lithium insertion / extraction, the stress generated by this volume change compresses the gaps between active particles in the anode, the pore structure of the separator, and the gap between the separator and the electrode. This reduces the electrolyte storage space at the interface between the separator and the anode, decreasing the smoothness of lithium-ion migration channels. Especially in wound lithium-ion batteries, the core has an arc-shaped area where both the electrode and separator are bent, further exacerbating the compression effect of the silicon-based material volume change on the particle gaps in the anode and the pore structure of the separator. This further worsens the electrolyte storage space and fluidity at the interface between the separator and the anode, making the anode prone to lithium plating, especially at high rates.

[0003] Therefore, it is very important to invent a battery that can increase the electrolyte storage space and electrolyte flow between the electrode and the separator, thereby reducing the risk of lithium plating. Summary of the Invention

[0004] Research has found that cobalt ions dissolved from the positive electrode active material can damage the SEI film, increase the consumption of lithium ions and electrolyte, and cause the battery capacity to decay more, especially at high temperatures, which will further deteriorate the battery's high-temperature cycle performance.

[0005] To address the issues of limited electrolyte storage space and poor electrolyte flow at the electrode-separator interface, which increase the risk of lithium plating, and the poor high-temperature cycle performance of batteries due to cobalt ion damage to the SEI film, this invention provides a separator and a battery including the separator. The separator of this invention forms a certain gap with the electrode, providing space for electrolyte storage and a channel for electrolyte flow during normal charge and discharge. This ensures electrolyte wetting and sufficient electrolyte in localized areas, improving or even preventing lithium plating at high rates. Simultaneously, the separator of this invention can reduce or even prevent cobalt ion damage to the SEI film, improving the high-temperature cycle performance of the battery.

[0006] To achieve the above objectives, a first aspect of the present invention provides a diaphragm comprising a carrier layer, a first adhesive layer, and a second adhesive layer. The first adhesive layer is located on one side surface of the carrier layer, and the second adhesive layer is located on the other side surface of the carrier layer. The carrier layer comprises a substrate layer and an organic coating located on at least one side surface of the substrate layer. The organic coating comprises organic particles, and the organic particles are composed of a bicyclic organic compound. The bicyclic organic compound comprises a bicyclic structure formed by a 2-mercaptoimidazole ring and a benzene ring sharing two adjacent carbon atoms. The first adhesive layer comprises first polymer particles, and the second adhesive layer comprises a porous structure formed by a second polymer.

[0007] 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, wherein the separator is located between the positive electrode and the negative electrode.

[0008] By employing the above technical solution, the present invention has at least the following advantages compared with the prior art: In the separator of the present invention, the first coating layer, including the first polymer particles, can form more gap spaces between the separator and the electrode, thereby ensuring the local liquid retention and flowability of the electrolyte. When the separator and the electrode are subjected to stress, it can maintain the gap between the electrode particles and the pore structure of the separator, providing space for electrolyte storage and providing channels for lithium ion migration, thereby improving the lithium plating of the negative electrode. The second coating layer, including the porous structure formed by the second polymer, can provide sufficient space for electrolyte storage, improve the lithium plating of the negative electrode, and also provide buffer space for the expansion of silicon-based materials. Moreover, the second coating layer with the porous structure has more contact sites with the active particles of the electrode, which can ensure the tight adhesion between the separator and the electrode. Even if the separator is continuously subjected to stress due to expansion and contraction during the battery charging and discharging process, it can still maintain a tight and uniform interface adhesion, thereby ensuring that the battery has high room temperature cycle performance. The organic particles in the organic coating consist of bicyclic structures and thiol groups. Firstly, the nitrogen atoms with lone pairs of electrons in the bicyclic structure endow the bicyclic organic compounds with a certain coordination ability, which allows them to interact with Li. + Coordination occurs, causing Li +Firstly, the bicyclic organic compound can be uniformly deposited on the surface of the negative electrode, thus working synergistically with the coating layer to further improve lithium plating on the negative electrode, especially significantly improving lithium plating in the arc region, thereby further enhancing the battery's room temperature cycle performance. Secondly, the coordination effect of the bicyclic organic compound can also adsorb transition metal ions on the surface of the positive electrode active particles, which can not only reduce or even avoid the dissolution of transition metal ions and improve the stability of the positive electrode active particles, but also complex the dissolved transition metal ions when they pass through the separator to the negative electrode side, controlling the transition metal ions within the bicyclic organic compound, thereby reducing or even preventing transition metal ions from passing through the separator to the negative electrode and damaging the SEI film, improving the stability of the SEI film, and thus improving the battery's high temperature cycle performance. Thirdly, the thiol group in the bicyclic compound has strong reducing properties, which can effectively capture the active free radicals generated by the electrolyte under high temperature conditions, blocking the free radical chain reaction that reduces the stability of the positive and negative electrode active materials, and improving the battery's high temperature cycle performance.

[0009] In summary, the separator of the present invention, through the synergistic effect of the organic coating and the adhesive layer, can improve the problems of small electrolyte storage space and poor electrolyte flow at the interface between the electrode and the separator, which increase the risk of lithium plating, as well as the damage of the SEI film by cobalt ions, which leads to poor high-temperature cycle performance of the battery. Thus, while improving the lithium plating situation, the battery has both high room temperature cycle performance and high high-temperature cycle performance.

[0010] Other features and advantages of the present invention will be described in detail in the following detailed description section.

[0011] 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

[0012] Figure 1 The image shown is one of the structural schematic diagrams of the diaphragm of the present invention.

[0013] Figure 2 The diagram shown is a second schematic diagram of the diaphragm structure of the present invention.

[0014] Figure 3 The third schematic diagram of the diaphragm structure of the present invention is shown.

[0015] Figure 4 The image shown is an SEM image of the organic coating of the diaphragm in one embodiment of the present invention.

[0016] Figure 5 The image shown is an SEM image of the first coating layer of the diaphragm in one embodiment of the present invention.

[0017] Figure 6 The image shown is an SEM image of the second coating layer of the diaphragm in one embodiment of the present invention.

[0018] Figure 7 The diagram shown is a schematic of the stripe coating in the second adhesive layer of the diaphragm of the present invention. Detailed Implementation

[0019] 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.

[0020] 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.

[0021] The first aspect of the present invention provides a diaphragm, the diaphragm comprising a carrier layer, a first adhesive layer, and a second adhesive layer, the first adhesive layer being located on one side surface of the carrier layer, and the second adhesive layer being located on the other side surface of the carrier layer. The carrier layer comprises a substrate layer and an organic coating located on at least one side surface of the substrate layer. The organic coating comprises organic particles, the organic particles comprising a bicyclic organic compound, the bicyclic organic compound comprising a bicyclic structure formed by a 2-mercaptoimidazole ring and a benzene ring sharing two adjacent carbon atoms. The first adhesive layer comprises first polymer particles, and the second adhesive layer comprises a porous structure formed by a second polymer.

[0022] In some specific implementation methods, such as Figure 1 The diaphragm 1 shown includes a substrate layer 11, an organic coating 12, a first adhesive layer 131 and a second adhesive layer 132. The organic coating 12 is located on one side of the substrate layer 11, the first adhesive layer 131 is located on the surface of the organic coating 12, and the second adhesive layer 132 is located on the other side of the substrate layer 11.

[0023] In some specific implementation methods, such as Figure 2 The diaphragm 1 shown includes a substrate layer 11, an organic coating 12, a first adhesive layer 131 and a second adhesive layer 132. The organic coating 12 is located on one side of the substrate layer 11, the first adhesive layer 131 is located on the other side of the substrate layer 11, and the second adhesive layer 132 is located on the surface of the organic coating 12.

[0024] In some specific implementation methods, such as Figure 3As shown, the diaphragm 1 includes a substrate layer 11, an organic coating 12, a first adhesive layer 131, and a second adhesive layer 132. The organic coating 12 is located on both sides of the substrate layer 11, and the first adhesive layer 131 and the second adhesive layer 132 are respectively located on the surfaces of the organic coating 12 on both sides.

[0025] In the diaphragm of the present invention, an organic coating (such as...) Figure 4 (As shown) includes organic particles containing bicyclic organic compounds with thiol groups, and the coating layers located on both sides of the carrier layer have different structures. The first coating layer (e.g.) Figure 5 (As shown) includes first polymer particles, second adhesive layer (as shown) Figure 6 (As shown) includes a porous structure formed from a second polymer.

[0026] The first coating layer, including the first polymer particles, can create more gaps between the separator and the electrode, thereby ensuring local electrolyte retention and giving the separator higher electrolyte retention, especially in the arc-shaped area of ​​the battery. This higher electrolyte retention helps to improve the black spots on the negative electrode caused by electrolyte deficiency in the arc-shaped area. Simultaneously, during battery charging and discharging, the stress caused by the expansion of active particles, especially the volume expansion of silicon-based materials, increases significantly. Constructing more gaps between the separator and the electrode helps to buffer the stress caused by expansion, reducing the stress on the separator and the electrode. This maintains the gap between the electrode and the separator and the porous structure of the separator itself, providing a more unobstructed channel for lithium-ion migration and further improving lithium plating. The porous structure in the second coating layer provides ample space for electrolyte storage, improving the black spots and lithium plating on the negative electrode. Therefore, in the battery, whether the first coating layer or the second coating layer corresponds to the negative electrode, it can improve the black spots and lithium plating on the negative electrode. At the same time, the porous structure of the second coating layer provides more contact sites between the active particles of the electrode, ensuring a tight bond between the separator and the electrode. Even during the battery charging and discharging process, the separator is constantly subjected to stress due to expansion and contraction, maintaining a tight and uniform interface bond, thus ensuring that the battery has high room temperature cycle performance.

[0027] Furthermore, the bicyclic organic compounds in the organic coating include bicyclic structures formed by a 2-mercaptoimidazole ring and a benzene ring sharing two adjacent carbon atoms. The nitrogen atom in the bicyclic structure has a pair of lone electrons, giving the bicyclic organic compound a certain coordination ability. Therefore, the bicyclic organic compound can react with Li. + This generates coordination, improving the uniformity of lithium-ion distribution at the interface between the separator and the electrode, thereby enabling Li... +The first coating layer can be uniformly deposited on the surface of the negative electrode, thus working synergistically with the adhesive layer to further improve the lithium deposition of the negative electrode, especially significantly improving the lithium deposition in the arc region. When the first adhesive layer is located on the surface of the organic coating, it can form more gap space between the separator and the electrode in the arc region, ensuring the local liquid retention and fluidity of the electrolyte. The bicyclic organic matter in the organic coating can improve the uniformity of lithium ion distribution at the interface between the separator and the electrode in the arc region, allowing lithium ions to be uniformly deposited on the surface of the negative electrode in the arc region. Therefore, under the synergistic effect of the organic coating and the first adhesive layer, while ensuring the liquid retention and fluidity of the electrolyte in the arc region, lithium ions in the arc region can be uniformly deposited on the surface of the negative electrode, thus significantly improving the lithium deposition in the arc region and further improving the room temperature cycle performance of the battery. Furthermore, the coordination effect of bicyclic organic compounds can also adsorb transition metal ions (such as cobalt, copper, nickel, and iron ions) on the surface of positive electrode active particles. This adsorption can reduce or even prevent the dissolution of transition metal ions, improving the stability of positive electrode active particles. On the other hand, even if some transition metal ions still dissolve, the bicyclic organic compounds can complex the dissolved transition metal ions as they pass through the separator to the negative electrode side, controlling the transition metal ions within the bicyclic organic compounds. This reduces or even prevents transition metal ions from passing through the separator to the negative electrode and damaging the SEI film, improving the stability of the SEI film and thus enhancing the high-temperature cycle performance of the battery. Moreover, the thiol groups (-SH) in the bicyclic compounds have strong reducing properties, effectively capturing active free radicals generated by the electrolyte at high temperatures, blocking free radical chain reactions that reduce the stability of both positive and negative electrode active materials, further improving the high-temperature cycle performance of the battery.

[0028] Therefore, the separator of the present invention, with the synergistic effect of the organic coating and the adhesive layer, can provide space for electrolyte storage and channels for electrolyte flow between the electrode and the separator, ensuring electrolyte wetting and sufficient electrolyte in local areas, and improving the uniformity of lithium ion distribution at the interface between the separator and the electrode. This improves or even avoids lithium plating in the battery at high rates, improves the battery's room temperature cycle performance, and can also reduce or even prevent the damage of transition metal ions to the SEI film, as well as eliminate active free radicals generated by the electrolyte at high temperatures, improve the stability of active materials at high temperatures, and improve the battery's high temperature cycle performance. Thus, while improving lithium plating, the battery has both high room temperature cycle performance and high high temperature cycle performance.

[0029] In this invention, by adding organic particles including bicyclic organic compounds to the organic coating, and designing the adhesive layers on both sides of the carrier layer to have different structures, it is possible to improve the lithium plating situation of the battery and enhance the battery's room temperature cycle performance and high temperature cycle performance compared with the prior art.

[0030] In some instances, the organic coating is located on one side of the substrate layer.

[0031] In some instances, the first adhesive layer is located on the surface of the organic coating, and the second adhesive layer is located on the opposite surface of the substrate layer (e.g., Figure 1 As shown in the diagram, the first coating layer corresponds to the positive electrode, and the second coating layer corresponds to the negative electrode. In this case, the first coating layer can create more gap space between the separator and the positive electrode, ensuring the local liquid retention of the electrolyte. Simultaneously, the bicyclic organic compound in the organic coating layer located on the same side as the first coating layer can adsorb transition metal ions (such as cobalt ions, copper ions, nickel ions, iron ions, etc.) on the surface of the positive electrode active particles. This adsorption can reduce or even prevent the dissolution of transition metal ions, improving the stability of the positive electrode active particles. Even if transition metal ions still dissolve, the bicyclic organic compound can complex the dissolved transition metal ions as they pass through the separator to the negative electrode side, preventing the transition metal ions from dissolving. Ions are controlled within the bicyclic organic material, thereby reducing or even preventing transition metal ions from penetrating the separator to the negative electrode and damaging the SEI film, thus improving the stability of the SEI film and enhancing the high-temperature cycle performance of the battery. On the other hand, the porous structure of the second coating layer has more contact sites with the active particles of the negative electrode, which helps to ensure a tight bond between the separator and the negative electrode. Even if the battery expands and contracts during charging and discharging, causing continuous stress on the separator, the tight and uniform interfacial bonding can ensure that the battery has excellent room-temperature cycle performance. At the same time, this porous structure layer also provides sufficient space for electrolyte storage, further improving the black spots and lithium plating in the arc area.

[0032] In this invention, the molecular structure of the bicyclic organic compound includes a thiol group, a carbon-nitrogen double bond, and a secondary amino group.

[0033] In some instances, the benzene ring in the bicyclic structure may or may not have substituents, which are selected from one or more of C1-C6 alkyl, C1-C6 alkoxy, hydroxy, amino, cyano, halogen substituents, sulfonic acid, carboxyl, and nitro groups. It is understood that "C1-C6 alkyl" refers to an alkyl group containing one to six carbon atoms (e.g., 1, 2, 3, 4, 5, or 6), and "C1-C6 alkoxy" refers to an alkoxy group containing one to six carbon atoms (e.g., 1, 2, 3, 4, 5, or 6).

[0034] C1-C6 alkyl groups may be selected from one or more of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl, neopentyl, 2,2-dimethylpropyl, 1-ethylpropyl, 1-methylbutyl, 2-methylbutyl, n-hexyl, isohexyl, 2-hexyl, and 3-hexyl.

[0035] C1-C6 alkoxy groups can be selected from one or more of methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, tert-butoxy, n-pentoxy, isopentoxy, tert-pentoxy, neopentoxy, 2,2-dimethylpropoxy, 1-ethylpropoxy, 1-methylbutoxy, 2-methylbutoxy, n-hexoxy, isohexoxy, 2-hexoxy, and 3-hexoxy.

[0036] In some instances, the substituent is selected from one or more of methyl, methoxy, ethoxy, hydroxy, amino, cyano, halogen substituent, sulfonic acid, carboxyl, and nitro groups.

[0037] The halogen substituent can be selected from one or more of F, Cl, Br and I.

[0038] In some instances, the bicyclic organic compound is 2-mercaptobenzimidazole or a 2-mercaptobenzimidazole derivative.

[0039] In this invention, 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.

[0040] In some instances, the organic particles in the organic coating comprise 50%–99% by weight (e.g., 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 99%).

[0041] In some instances, the organic coating also includes a first adhesive.

[0042] In some instances, the first adhesive includes one or more of polyvinyl alcohol, styrene-butadiene rubber, ethylene-vinyl acetate copolymer, sodium carboxymethyl cellulose, polyvinylpyrrolidone, acrylate adhesives, styrene-acrylic latex, polyacrylonitrile, polyacrylic acid, polyvinyl acetate, polyurethane, fluoropolymers, or copolymers derived from the above polymers.

[0043] In some instances, acrylate adhesives include one or more of the following: 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.

[0044] In this invention, the fluoropolymer includes one or more of polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylidene fluoride-trichloroethylene, polyvinylidene fluoride-chlorotrifluoroethylene, acrylic acid-vinylidene fluoride copolymer, and acrylonitrile-vinylidene fluoride copolymer.

[0045] In some instances, the weight percentage of the first binder in the organic coating is 1%-10% (e.g., 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any combination of the above values).

[0046] In some instances, the organic coating also includes optional filler particles.

[0047] In some instances, the filler particles in the organic coating comprise 0%–49% by weight (e.g., 0%, 0.1%, 0.5%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 49%).

[0048] In some instances, the filler particles are composed of one or more of the following: 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, aluminum nitride, boron nitride, zirconium titanate, barium titanate, magnesium fluoride, melamine cyanurate, 1,3,5-triazine-2,4,6-triamine, melamine thiocyanate, uracil, cytosine, guanine, N,N'-di(β-naphthyl)-p-phenylenediamine, and 4-amino-2,6-dihydroxypyrimidine.

[0049] 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, 5 μm).

[0050] In some instances, the coverage of the first adhesive layer on the carrier layer surface is 5%-60% (e.g., 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, or any two of the above values). Controlling the coverage of the first adhesive layer on the carrier layer surface ensures sufficient contact sites between the separator and the electrode, improving the interfacial adhesion between them. When the coverage of the first adhesive layer on the carrier layer surface is less than 5%, the adhesion sites of the separator are insufficient, resulting in weak adhesion and hindering further improvement in room temperature cycling performance. When the coverage of the first adhesive layer on the carrier layer surface is greater than 60%, the hindrance to lithium-ion migration increases, which is detrimental to further improving kinetic performance and lithium plating in the arc region.

[0051] In this invention, the coverage of the first adhesive layer on the carrier layer surface refers to the ratio of the projected area of ​​all polymer particles in the first adhesive layer on the carrier layer surface to the total area of ​​the carrier layer surface on the side with the first adhesive layer. The coverage of the first adhesive layer on the carrier layer surface can be obtained by the following method: using a Hitachi S-3400N scanning electron microscope at 1000x magnification, observe the surface of the first adhesive layer; arbitrarily select three 100μm × 100μm areas on the surface of the first adhesive layer; use ImageJ software to calculate the ratio of the projected area of ​​all polymer particles on the carrier layer surface to the total area of ​​the carrier layer surface on that side; and take the average value as the final test result of the coverage of the first adhesive layer on the carrier layer surface. Alternatively, the following test method can be used: Take a 3cm×3cm diaphragm sample, stain and penetrate the diaphragm with dye penetrant DPT-5 in a fume hood, and after the membrane surface is air-dried, take out 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 count), thus obtaining the coverage of the first coating layer on the carrier layer surface.

[0052] In some examples, the average particle size of the primary particles of the first polymer particles is 0.1 μm-5 μm (e.g., 0.1 μm, 0.5 μm, 0.65 μm, 0.85 μm, 0.95 μm, 1 μm, 3 μm, 5 μm, or within any two of the above values). When the average particle size of the primary particles of the first polymer particles is greater than 5 μm, the first polymer particles swell excessively in the electrolyte, clogging the pores of the carrier layer, which is detrimental to the rapid migration of lithium ions. Controlling the average particle size of the primary particles of the first polymer particles within the above range can ensure the electrolyte storage space and electrolyte flow between the separator and the electrode, while also enabling the separator to have good lithium ion permeability and excellent adhesion between the separator and the electrode, thus giving the battery high kinetic performance and further improving the battery's rate performance.

[0053] In this invention, the average particle size of the primary particles of the first polymer particles can be obtained through SEM testing. Specifically, using a Hitachi S-3400N scanning electron microscope at 20,000x magnification, the surface of the first coating layer is observed. On the image obtained from the SEM observation of the first coating layer surface, a square or rectangle with the smallest area completely surrounding each primary particle of the first polymer particle is drawn. That is, a square or rectangle is drawn where the edge of the primary particle of the first 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 of the primary particle of the first polymer particle. The average particle size is obtained by averaging the particle sizes of 100 primary particles of the first polymer particles on the surface of the first coating layer. This operation is repeated 5 times, and the average value is taken as the test value of the average particle size of the primary particles of the first polymer particles. It should be noted that if 100 primary particles of the first polymer particles are not observed in the image, multiple images are taken, and the average particle size of the total 100 primary particles of the first polymer is taken as the average particle size. It is understandable that when the first coating layer contains both dispersed polymer particles and agglomerated polymer particles, the average particle size of the primary particles of the first polymer particles is the average of the average particle size of the second particles and the average particle size of the primary particles of the first particles. Dispersed polymer particles refer to the first polymer particles being dispersedly distributed in the first coating layer, and in the thickness direction of the membrane, the dispersed polymer particles are dispersedly distributed in the first coating layer, with only one layer or multiple layers, and no large-size agglomerates appear.

[0054] In some instances, the first polymer particle includes at least one of a first particle and a second particle.

[0055] In some instances, the first polymer particle is the second particle. When the first polymer particle is the second particle, the adhesion between the separator and the electrode can be improved, but it is not conducive to further improving the gap space between the separator and the electrode, and is not conducive to further improving the electrolyte storage capacity and flowability.

[0056] In some instances, the first polymer particle includes at least a first particle.

[0057] In some instances, the first polymer particle is the first particle. When the first polymer particle is the first particle, the gap space between the separator and the electrode can be increased, further improving the electrolyte storage capacity and flowability, but it is not conducive to further improving the adhesion between the separator and the electrode.

[0058] In some instances, the first polymer particle consists of a first particle and a second particle.

[0059] In some instances, the first particle is an agglomerated polymer particle, and the second particle is a dispersed polymer particle.

[0060] In some instances, the first particle includes a secondary particle formed by the aggregation of primary particles. In this invention, a secondary particle refers to a particle formed by the aggregation of at least five primary particles.

[0061] In some instances, the average particle size of the primary particles of the first particle is 0.1 μm to 0.4 μm (e.g., 0.1 μm, 0.13 μm, 0.15 μm, 0.18 μm, 0.2 μm, 0.23 μm, 0.25 μm, 0.28 μm, 0.3 μm, 0.33 μm, 0.35 μm, 0.38 μm, 0.4 μm or within any two of the above values), and the average particle size of the secondary particles is 2 μm to 30 μm (e.g., 2 μm, 5 μm, 7 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 22 μm, 25 μm, 27 μm, 30 μm or within any two of the above values).

[0062] In some instances, the average particle size of the secondary particles ranges from 4 μm to 28 μm.

[0063] In this invention, the average particle size of the primary particles of the first particle can be obtained through SEM testing. For example, using a Hitachi S-3400N scanning electron microscope, on an image obtained by observing the surface of the first coating layer through SEM, the particle size of 50 randomly selected primary particles of the first particle is measured using image analysis software (e.g., ImageJ, NanoMeasurer, Matlab, etc.). The average particle size of the 50 primary particles of the first particle is the average particle size of the primary particles of the first particle. It is understood that if no 50 first particles are observed in the image, multiple images are taken, and the average of the particle sizes of the primary particles of the total 50 images is taken as the average particle size of the primary particles of the first particle.

[0064] In this invention, the average size of the secondary particles can be obtained by the following method: Using a Hitachi S-3400N scanning electron microscope, on an image obtained by observing the surface of the first coating layer via SEM, draw the smallest square or rectangle that completely surrounds one secondary particle. That is, draw a square or rectangle where the edge of the secondary particle meets all four sides of the square or rectangle. The length of one side of the square or the long side of the rectangle is the particle size of the secondary particle. The average particle size is obtained by averaging the particle sizes of 50 random secondary particles measured on the surface of the first coating layer. This process is repeated 5 times, and the average value is taken as the test value of the average particle size. It should be noted that if no 50 secondary particles are observed in the image, multiple images are taken, and the average particle size of the total 50 secondary particles is taken as the average particle size.

[0065] In some examples, the number of secondary particles within any 100μm × 100μm area on the surface of the first coating layer is between 20 and 1000 (e.g., 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 1000, or within any two of the above values). Controlling the number of secondary particles within this range within any 100μm × 100μm area on the surface of the first coating layer can further balance the conflict between stress relief and lithium-ion transport efficiency, ensuring lithium-ion transport efficiency while relieving stress. When the number of secondary particles in any 100μm×100μm area on the surface of the first coating layer is less than 20, it is not conducive to further increasing the gap space between the separator and the electrode, and it is not conducive to further improving the storage capacity and fluidity of the electrolyte. When the number of primary particles in any 100μm×100μm area on the surface of the first coating layer is greater than 2000, the gap between the separator and the electrode is too large and the adhesion between the separator and the electrode is reduced, the lithium ion transport path increases, and it is not conducive to further improving the rapid migration of lithium ions.

[0066] In some instances, the number of secondary particles is 30 to 100 within any 100μm × 100μm area on the surface of the first coating layer.

[0067] In some instances, the average particle size of the second particle is 0.1 μm-5 μm (e.g., 0.1 μm, 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).

[0068] In some instances, the average particle size of the second particle is 0.3 μm to 1.2 μm.

[0069] In this invention, the average particle size of the second particle can be obtained through SEM testing. Specifically, using a Hitachi S-3400N scanning electron microscope at 20,000x magnification, the surface of the first coating layer is observed. On the image obtained from the SEM observation of the first coating layer surface, the particle size of 50 randomly selected second particles is measured using image analysis software (e.g., ImageJ, NanoMeasurer, Matlab, etc.). The average particle size of these 50 particles is the average particle size of the second particle. It is understood that if no 50 second particles are observed in the image, multiple images are taken, and the average of the total particle sizes of the 50 second particles is taken as the average particle size of the second particle.

[0070] In some instances, the composition of the first polymer particles includes one or more of the following: fluoropolymers, acrylate polymers, polyacrylonitrile, polyacrylic acid, polyvinyl alcohol, modified polyvinyl alcohol, polyvinyl acetate, polyacrylamide, phenolic resin, epoxy resin, ethylene-vinyl acetate copolymer, lithium polystyrene sulfonate, polyethylene oxide, cyanoethyl polyvinyl alcohol, butadiene-acrylonitrile copolymer and its derivatives, aramid, modified aramid, phenolic resin, modified phenolic resin, polyimide, polyetherimide, and modified polyimide.

[0071] In some instances, acrylate polymers include one or more of the following: 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.

[0072] In this invention, the acrylate monomers are selected from one or more of methyl acrylate, methyl methacrylate, ethyl acrylate, butyl acrylate, and ethyl methacrylate.

[0073] In some instances, modified aramids include bio-based aramids.

[0074] In some instances, the modified aramid fibers have a structure as shown in formula (I). Equation (I), where m is an integer from 5 to 100, n is an integer from 5 to 100, and Ar1 is selected from... and Ar2 is selected from one or more of the following groups: , , , , , , , , , , , , , , , and .

[0075] In some instances, the first polymer particles were immersed in the test electrolyte for 4 hours at 65°C, and the mass swelling degree of the first polymer particles ranged from 2% to 250% (e.g., 2%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 110%, 120%, 130%, 140%, 150%, 160%, 170%, 180%, 190%, 200%, 250%, or within any two of the above values). When the mass swelling degree of the first polymer particles exceeded 200%, the risk of membrane pore blockage increased, which was detrimental to lithium-ion transport, increased interfacial impedance, and hindered further improvement in battery cycle performance. When the mass swelling degree of the first polymer particles is less than 2%, the first polymer particles have high rigidity, which is not conducive to further improving the adhesion between the first coating layer and the electrode. At the same time, the compressibility of the first polymer particles is reduced, which is not conducive to improving the flexibility and flexibility of the diaphragm, reducing the fit between the diaphragm and the electrode, and also not conducive to further improving the adhesion effect between the diaphragm and the electrode.

[0076] In this invention, the test electrolyte is composed of lithium hexafluorophosphate, ethylene carbonate, methyl ethyl carbonate and dimethyl carbonate, with the concentration of lithium hexafluorophosphate being 1 mol / L and the volume ratio of ethylene carbonate, methyl ethyl carbonate and dimethyl carbonate being 1:1:1.

[0077] In some instances, the first polymer particles were immersed in the test electrolyte for 4 hours at 65°C, and the mass swelling of the first polymer particles was 20%-100%.

[0078] In some instances, the first particle was immersed in the test electrolyte for 4 hours at 65°C, and the mass swelling of the first particle was 2%-200% (e.g., 2%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 110%, 120%, 130%, 140%, 150%, 160%, 170%, 180%, 190%, 200%, or within any two of the above values).

[0079] In some instances, the first particle was immersed in the test electrolyte for 4 hours at 65°C, and the mass swelling of the first particle was 20%-120%.

[0080] In some instances, the second particle was immersed in the test electrolyte for 4 hours at 65°C, and the mass swelling of the second particle was 2%-250% (e.g., 2%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 110%, 120%, 130%, 140%, 150%, 160%, 170%, 180%, 190%, 200%).

[0081] In some instances, the second particle was immersed in the test electrolyte for 4 hours at 65°C, and the mass swelling of the second particle was 20%-200%.

[0082] In this invention, the mass swelling degree of the first particle and the mass swelling degree of the second particle can be adjusted by conventional technical means known to those skilled in the art (such as changing one or more of the type of polymerizing monomer, degree of polymerization, molecular weight, crystallinity, polymerization process, etc.), or commercially available products that meet the conditions can be purchased directly.

[0083] In this invention, the mass swelling degree of the first polymer particle, the mass swelling degree of the second particle, and the mass swelling degree of the first polymer particle can all be determined by the following method after soaking in the test electrolyte at 65°C for 4 hours. Specifically, taking "the mass swelling degree of the first polymer particle after soaking in the test electrolyte at 65°C for 4 hours" as an example, the first polymer particle is dispersed in water and then dried to form an independent film, and the initial weight W is weighed and recorded. 1 The film was immersed in the test electrolyte at 65°C for 4 hours. After removing the film, wiping off excess electrolyte, and weighing it, W was obtained. 2 Then the degree of swelling by weight W = [(W2 -W 1 ) / W 1 ×100%. When the first polymer particle includes a first particle and a second particle, the mass swelling degree of the first polymer particle refers to the overall mass swelling degree after the first particle and the second particle are mixed according to the required mass ratio.

[0084] In some instances, the first polymer particles are composed of acrylate polymers, and their glass transition temperature is between 30°C and 100°C (e.g., 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, or any two of these values). Controlling the glass transition temperature of the first polymer particles within this range further balances the interfacial adhesion between the separator and the electrode, maintaining a stable interface during battery charging and discharging.

[0085] In this invention, the glass transition temperature of the first polymer particle can be obtained by the following method: A dried sample of the first polymer particle is weighed and placed in an aluminum crucible, which is then sealed tightly. The test is performed using DSC (Differential Scanning Calorimetry) under a nitrogen atmosphere, starting at room temperature with a heating rate of 10°C / min. After the test, the region where the baseline abruptly changes is found on the heat flow-temperature curve. According to international standards (such as ISO 11357-2), the extrapolated onset temperature is used as the glass transition temperature of the first polymer particle.

[0086] In some instances, the first polymer particles are composed of a fluoropolymer, and the melting point temperature of the first polymer particles is 120°C-180°C (e.g., 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, 180°C, or any two of the above values). Controlling the glass transition temperature of the first polymer particles within the above range can further balance the interfacial adhesion between the separator and the electrode, maintaining a stable interface during battery charging and discharging.

[0087] In some instances, the thickness of the first adhesive layer is 0.5 μm to 5 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).

[0088] In some instances, the second coating layer is applied continuously or intermittently. Intermittent application is a striped coating (e.g., Figure 7 ).

[0089] In some examples, the area of ​​the pores in the second adhesive layer projected onto the carrier layer accounts for 10%-90% of the total surface area of ​​the carrier layer (e.g., 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or any two of the above values). Controlling the area of ​​the pores in the second adhesive layer projected onto the carrier layer within this range allows the second adhesive layer to have a good porous structure, thereby further enhancing ion diffusion and migration, improving the kinetic performance of the separator, and ensuring that the porous structure's framework provides good support. This, to a certain extent, improves the structural stability of the porous coating, enabling the second adhesive layer to better withstand the stress and deformation generated during battery charging and discharging.

[0090] In some instances, the projected area of ​​the pores in the second coating layer onto the carrier layer accounts for 25%-75% of the total area of ​​the carrier layer surface.

[0091] In this invention, the area ratio of the orthogonal projection area of ​​the pores in the second coating layer onto the carrier layer to the total surface area of ​​the carrier layer can be adjusted using conventional techniques known to those skilled in the art (such as coating formulations, preparation processes, etc.). This ratio can be obtained through testing as follows: Select a region of the separator removed from the battery that is not in direct contact with the active layer (e.g., the region of the separator extending beyond the positive or negative electrode), or randomly select a region from a separator that has not yet been fabricated into a battery and cut out a sample of a certain size (e.g., 10 mm × 10 mm). Use a scanning electron microscope (e.g., a Sigma 300 scanning electron microscope from ZEISS, Germany) to obtain a SEM image of the separator (magnification can be 1000x to 30000x). Select the entire area coated with the second coating layer as the test area. Use an image processing detection system (e.g., the Yihong separator detection system 2022-0408) to obtain the total area of ​​the pores in the second coating layer within this test area using a multi-segment binarization method. 1 The total area S of the pores in the second coating layer within the test area 1 The area S of the carrier layer within the selected test area 2 The ratio is C, which is the proportion of the projected area of ​​the pores in the second coating layer onto the carrier layer to the total surface area of ​​the carrier layer. 1 To improve accuracy, the above procedure was repeated five times, and the average of the five parallel samples was taken as the test result. It is understood that when the second adhesive layer is applied intermittently, the test area needs to be selected from the area where the second adhesive layer is applied.

[0092] In some instances, the second polymer includes one or more of the following: fluoropolymers, polyacrylonitrile, polymethyl methacrylate, polyacrylic acid, polyvinyl alcohol, modified polyvinyl alcohol, polyvinyl acetate, polyacrylamide, phenolic resins, epoxy resins, ethylene-vinyl acetate copolymers, multi-component acrylic copolymers, lithium polystyrene sulfonate, polyethylene oxide, cyanoethyl polyvinyl alcohol, butadiene-acrylonitrile copolymers and their derivatives, aramid fibers, phenolic resins, modified phenolic resins, polyimides, polyetherimides, and modified polyimides.

[0093] In some instances, the second adhesive layer comprises a fluoropolymer with a melting point temperature of 120°C–180°C (e.g., 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, 180°C, or any combination of two of these values). Controlling the melting point temperature of the fluoropolymer within this range ensures that the second adhesive layer maintains a stable porous structure even at high temperatures.

[0094] In some instances, the weight percentage of the second polymer in the second adhesive layer is 30%-100% (e.g., 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%).

[0095] In some instances, the second coating layer also includes heat-resistant particles.

[0096] In some instances, the heat-resistant particles are composed of one or more of the following: 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, aluminum nitride, boron nitride, zirconium titanate, barium titanate, magnesium fluoride, melamine cyanurate, 1,3,5-triazine-2,4,6-triamine, melamine thiocyanate, uracil, cytosine, guanine, 2-mercaptobenzimidazole, 2-mercaptobenzimidazole derivatives, N,N'-di(β-naphthyl)-p-phenylenediamine, and 4-amino-2,6-dihydroxypyrimidine.

[0097] In some instances, the weight percentage of heat-resistant particles in the second adhesive layer ranges from 0% to 70% (e.g., 0%, 0.1%, 0.5%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%). When the weight percentage of heat-resistant particles in the second adhesive layer is 0%, it indicates that heat-resistant particles are absent.

[0098] In some instances, the thickness of the second adhesive layer is 0.5 μm to 5 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 or within any two of the above values).

[0099] According to some specific embodiments, the second coating layer is a porous structure formed by a second polymer as a continuous phase. The second polymer includes one or more of the following: fluoropolymer, polyacrylonitrile, polymethyl methacrylate, polyacrylic acid, polyvinyl alcohol, modified polyvinyl alcohol, polyvinyl acetate, polyacrylamide, phenolic resin, epoxy resin, ethylene-vinyl acetate copolymer, multi-component acrylic copolymer, lithium polystyrene sulfonate, polyethylene oxide, cyanoethyl polyvinyl alcohol, butadiene-acrylonitrile copolymer and its derivatives, aramid, phenolic resin, modified phenolic resin, polyimide, polyetherimide, and modified polyimide. The thickness of the second coating layer is 0.5 μm-5 μm. The second coating layer also includes heat-resistant particles, with the weight percentage of heat-resistant particles in the second coating layer being 0%-70%. The second coating layer helps to ensure the uniformity of the interface between the separator and the electrode, provides a smooth channel for lithium-ion transport, and takes into account the battery dynamics performance, enabling the battery to have both high rate performance and high cycle performance.

[0100] In some instances, the thickness of the substrate layer is 3.5 μm to 16 μm.

[0101] In some instances, the thickness of the substrate layer is 4μm-9μm.

[0102] In some instances, the porosity of the substrate layer ranges from 30% to 75%.

[0103] In some instances, the porosity of the substrate layer is 38%–55%.

[0104] 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.

[0105] In some instances, the average pore size of the substrate layer is 30nm-55nm.

[0106] 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, polyethylene terephthalate, polybutylene terephthalate, poly(p-phenylene terephthalamide), poly(m-phenylene isophthalamide), or poly(m-phenylene isophthalamide).

[0107] A second aspect of the present invention provides a battery comprising a positive electrode, a negative electrode, and a separator of the first aspect of the present invention, wherein the separator is located between the positive electrode and the negative electrode.

[0108] In some instances, the adhesion between the separator and the positive electrode is 2 N / m to 50 N / m (e.g., 2 N / m, 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).

[0109] In some instances, the adhesion between the diaphragm and the negative electrode is 2 N / m to 50 N / m. (For example, 2 N / m, 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, or any two of the above values).

[0110] In this invention, the adhesion force between the separator and the positive electrode sheet, and the adhesion force between the separator and the negative electrode sheet, can be tested using the following method. Specifically, taking the "adhesion force between the separator and the negative electrode sheet" as an example, a composite strip with a length of 200 mm and a width of 20 mm is cut and bonded together with the separator and the negative electrode sheet. The cut composite strip is fixed to the steel plate with double-sided tape, and the separator and the steel plate are connected by the double-sided tape. It is rolled once with a 2 kg roller. A universal tensile testing machine is used, with the upper clamp holding the negative electrode sheet and the lower clamp holding the steel plate, and 180° peeling is performed. The test speed is 100 mm / min, and the test displacement distance is 100 mm. During the test, the average tensile force (unit N) and the adhesion force are obtained as the average adhesion force (unit N / m). The average adhesion force = average tensile force / strip width.

[0111] In some examples, the positive electrode corresponds to the first coating layer, and the negative electrode corresponds to the second coating layer. This can improve the adhesion between the separator and the negative electrode and form a buffer space between the separator and the positive electrode, further improving the protection against positive electrode current collector breakage caused by negative electrode volume change stress during cycling.

[0112] In some instances, the battery includes a casing and a cell located within the containment space formed by the casing. The cell includes an electrolyte and an electrode assembly formed by stacking and winding a positive electrode, a separator, and a negative electrode. The electrode assembly includes flat regions and arc-shaped regions. The separator satisfies the following relationship: 0.1 ≤ (H 1 -H2 ) / H 1 ≤0.9 (e.g., 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or any two of the above values), where H 1 H represents the thickness of the diaphragm located in the arc region, in μm. 2 The thickness of the separator located in the flat region is expressed in μm. Controlling the separator to satisfy the above relationship can make the separator more compressible. On the one hand, this can alleviate the expansion stress generated during battery cycling, reduce or even prevent the risk of electrode current collector breakage due to cyclic expansion stress. On the other hand, it can further improve the electrolyte wetting in the arc region, thereby further improving the lithium plating situation in the arc region.

[0113] In this invention, the thickness H of the diaphragm located in the arc region is... 1 And the thickness H of the diaphragm located in the flat region 2 The regulation can be achieved in the following ways: 1) Use first and second coating layers of different thicknesses in the arc area and the straight area respectively; 2) Change the compressibility of the first particles in the first coating layer (such as changing the average particle size of the secondary particles, changing the type of polymerizable monomer, degree of polymerization, molecular weight, crystallinity, polymerization process, etc.) or the hot pressing and formation process of the battery.

[0114] In some instances, the negative electrode includes a negative current collector and a negative active layer located on at least one side of the surface of the negative current collector.

[0115] In some instances, the negative electrode active layer includes a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder.

[0116] In some instances, the negative electrode active material includes silicon-based materials, selected from elemental silicon particles and silicon-oxygen particles (such as SiO₂). x One or more of the following: silicon carbide particles (e.g., Si / C), silicon nitride particles, and silicon alloy particles.

[0117] In some instances, the silicon-carbon particles comprise a porous carbon support and elemental silicon particles that are at least partially located within the pores of the porous carbon support.

[0118] In some instances, the average particle size of silicon-carbon particles is 5μm-12μm, for example, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, or within any two of the above values.

[0119] In this invention, the average particle size of silicon-carbon particles can be obtained by the following method: On a scanned image of the surface of the negative electrode active layer, draw the smallest square or rectangle that completely surrounds a silicon-carbon particle, i.e., draw a square or rectangle whose edge of the silicon-carbon particle is connected to the 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 of the silicon-carbon particle. The average particle size is the number of particle sizes of any 100 silicon-carbon particles on the surface of the negative electrode active layer. Repeat the above operation 5 times and take the average value as the average particle size of the silicon-carbon particles. It should be noted that when 100 silicon-carbon particles can be observed in the captured image, the average particle size of any 100 silicon-carbon particles in the image is taken as the average particle size of the silicon-carbon particles. When no 100 silicon-carbon particles are observed in the image, take multiple images and take the average particle size of the total number of 100 silicon-carbon particles as the average particle size. The average particle size of silicon-carbon particles can also be obtained by testing with a laser particle size analyzer. For example, before preparing the negative electrode, the average particle size of silicon-carbon particles can be obtained by measuring the silicon-carbon particles with a laser particle size analyzer.

[0120] In some instances, the negative electrode active layer also includes carbon-based materials, including one or more of natural graphite and artificial graphite.

[0121] In some instances, the negative electrode active layer comprises a negative electrode active material, which may be silicon-based or optionally carbon-based.

[0122] In some instances, carbon-based materials include synthetic graphite and natural graphite.

[0123] In some instances, the negative electrode active material is a silicon-based material.

[0124] In some instances, based on the total weight of the negative electrode active layer, the weight percentage of silicon-based materials can range from 5% to 95% (e.g., 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%), while the weight percentage of carbon-based materials 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%, 0%).

[0125] In some instances, the negative electrode active material layer also includes a negative electrode conductive agent and a negative electrode binder.

[0126] In some instances, the negative electrode conductive agent includes one or more of conductive carbon black, graphene, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, and carbon nanotubes.

[0127] In some instances, the negative electrode binder includes one or more of polyurethane, polyacrylic acid, acrylate binders, sodium carboxymethyl cellulose, styrene-butadiene latex, vinylidene fluoride-hexafluoropropylene copolymer, acrylic acid-vinylidene fluoride copolymer, acrylonitrile-vinylidene fluoride copolymer, polytetrafluoroethylene, polyethylene oxide, and polyvinylidene fluoride.

[0128] 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.

[0129] In some instances, the surface of the negative electrode active layer away from the negative electrode current collector is the first surface, and the first surface includes several grooves.

[0130] In some instances, the negative electrode corresponds to one side of the second adhesive layer in the separator, and the battery satisfies the following relationship: 0.1≤L 1 / C 1 ≤1 (e.g., 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, or any two of the above values), where L 1 C represents the coverage of the groove on the first surface. 1 This represents the percentage of the area of ​​the pores in the second coating layer projected onto the carrier layer in the total surface area of ​​the carrier layer. By controlling the battery to satisfy the above relationship, in addition to improving the battery's kinetic performance and the liquid storage space at the interface between the separator and the electrode, the contact sites between the porous framework portion of the separator's second coating layer and the active material particles in the non-grooved region of the negative electrode are more sufficient, which can further reduce impedance and further improve lithium plating in the arc region.

[0131] In some instances, the coverage L of the groove on the first surface 1 It is 2%-30% (e.g., 2%, 5%, 7%, 10%, 12%, 15%, 17%, 20%, 22%, 25%, 27%, 30%, or within any two of the above values).

[0132] In this invention, the coverage of the groove on the first surface refers to the ratio of the orthographic projection area of ​​the groove on the first surface to the surface area of ​​the first surface.

[0133] According to some specific implementation methods, L 1 It is 2%-30%, C 1The coating thickness is 10%-90%, with one side of the negative electrode corresponding to one side of the second adhesive layer in the separator. The battery satisfies the following relationship: 0.1≤L 1 / C 1 ≤1.

[0134] According to some specific implementation methods, L 1 It is 2%-30%, C 1 The content is 25%-75%, the negative electrode sheet corresponds to one side of the second coating layer in the separator, and the battery satisfies the following relationship: 0.1≤L 1 / C 1 ≤1.

[0135] In some instances, the positive electrode sheet is a conventional positive electrode sheet in the art. For example, the positive electrode sheet includes a positive current collector and a positive active layer located on at least one surface of the positive current collector. The positive active layer is not particularly limited and can include components such as a positive active material, a positive conductive agent, and a positive binder, according to conventional compositions in the art. The positive active material, positive conductive agent, and positive binder can all be conventional materials in the art. For example, the positive active material can include 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; the positive conductive agent can include one or more of conductive carbon black, carbon nanotubes, conductive graphite, and graphene; and the positive binder can include one or more of polyvinylidene fluoride (PVDF), acrylic acid-modified PVDF, polyacrylate polymers, acrylic polymers, polytetrafluoroethylene, polyacrylonitrile, polyimide, vinylidene fluoride-hexafluoropropylene copolymer, acrylic acid-vinylidene fluoride copolymer, acrylonitrile-vinylidene fluoride copolymer, polyurethane, styrene-butadiene rubber, and styrene-acrylic rubber.

[0136] In some instances, the battery is a lithium-ion rechargeable battery.

[0137] 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.

[0138] The following examples illustrate the separator and battery of the present invention.

[0139] Example 1 (1) Preparation of the diaphragm 95 parts by weight of organic particles (2-mercaptobenzimidazole) and 5 parts by weight of the first binder (polyacrylic acid: polymethyl methacrylate (weight ratio) = 1:1) were mixed in water and stirred thoroughly to obtain an organic slurry with a solid content of 25%. The organic slurry was coated onto one side of a substrate layer (polyethylene) with a thickness of 5 μm and a porosity of 40% by a gravure roller. After drying in a multi-section oven at 60°C, an organic coating with a thickness of 2 μm was formed.

[0140] First polymer particles (first particle (PVDF) and second particle (PMMA)) were mixed with deionized water and stirred at high speed to ensure thorough mixing and uniform dispersion, resulting in a first slurry with a solid content of 8%. The first slurry was then coated onto the surface of an organic coating using a gravure roller and dried in a multi-section oven at 60°C to form a first adhesive layer. At 65°C, the first particle exhibited a mass swelling degree of 68% after immersion in the test electrolyte for 4 hours, while the second particle exhibited a mass swelling degree of 172% after immersion in the test electrolyte for 4 hours at 65°C.

[0141] The second polymer (PVDF) and DMAC were mixed and thoroughly stirred until dissolved. Heat-resistant particles (alumina) were then added and stirred until evenly dispersed to obtain a second slurry with a solid content of 8%. This second slurry was then coated (continuous coating) onto the other side of the substrate layer using a gravure roller. In 100 parts by weight of the second slurry, the contents of PVDF and alumina were 40 parts by weight and 60 parts by weight, respectively. The membrane coated with the second slurry was then subjected to water extraction to create pores using organic solvent, and subsequently dried in a multi-section oven at 60°C to form a second coating layer with a thickness of 2 μm.

[0142] (2) Preparation of positive electrode sheet Lithium cobalt oxide, polyvinylidene fluoride (PVDF 500) binder, and conductive material (SuperP:carbon nanotubes = 2:1) were mixed in N-methylpyrrolidone (NMP) solvent at a weight ratio of 98:1:1 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 positive electrode sheet.

[0143] (3) Preparation of negative electrode sheet Graphite, silicon carbide (Dv50=7μm), conductive material (carbon black:carbon nanotubes=1:1), sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber were mixed in an aqueous solvent at a weight ratio of 90:8:1:0.5:0.5 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 10μm thick current collector copper foil and dried in a vacuum oven at 120℃ for 6 hours. Then, it was rolled and slit to obtain the negative electrode sheet.

[0144] (4) Preparation of electrolyte In an argon-filled glove box (moisture content <1 ppm, oxygen content <1 ppm), ethylene carbonate, propylene carbonate, propyl propionate, and ethyl propionate solvents were mixed in a volume ratio of 15:15:50:20 to form a homogeneous solvent. Then, 16 wt% LiPF6, 3 wt% 1,3,6-hexanetrionitrile, and 14 wt% fluoroethylene carbonate (based on the total mass of the electrolyte) were slowly added and stirred until homogeneous to obtain the electrolyte.

[0145] (5) Preparation of lithium-ion batteries 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, and high temperature formation, a lithium-ion battery is obtained. The positive electrode sheet corresponds to the side of the separator with the first adhesive layer, and the negative electrode sheet corresponds to the side of the separator with the second adhesive layer.

[0146] Example 2 group Example 2a The experiment was carried out in accordance with Example 1, except that the positive electrode sheet and the side of the separator with the second adhesive layer corresponded to each other, and the negative electrode sheet and the side of the separator with the first adhesive layer corresponded to each other. The adhesion between the separator and the positive electrode sheet was 17 N / m, and the adhesion between the separator and the negative electrode sheet was 13 N / m.

[0147] Example 2b The procedure is carried out in accordance with Example 1, except that the first adhesive layer is located on one side of the substrate layer, the organic coating is located on the other side of the substrate layer, and the second adhesive layer is located on the surface of the organic coating (e.g., ...). Figure 2 As shown in the figure, the positive electrode sheet corresponds to the side of the separator with the first adhesive layer, and the negative electrode sheet corresponds to the side of the separator with the second adhesive layer. The adhesion force between the separator and the positive electrode sheet is 16.7 N / m, and the adhesion force between the separator and the negative electrode sheet is 16.5 N / m.

[0148] Example 2c The procedure is carried out in accordance with Example 1, except that the organic coatings are located on both sides of the substrate layer, the first adhesive layer is located on the surface of one side of the organic coating, and the second adhesive layer is located on the surface of the other side of the organic coating (e.g., ...). Figure 3 As shown in the figure, the positive electrode sheet corresponds to the side of the separator with the first adhesive layer, and the negative electrode sheet corresponds to the side of the separator with the second adhesive layer. The adhesion force between the separator and the positive electrode sheet is 14.3 N / m, and the adhesion force between the separator and the negative electrode sheet is 16.3 N / m.

[0149] Example 3 Group This set of examples illustrates the effects of changing the specific choice of a bicyclic organic compound.

[0150] This embodiment group is based on Example 1, except that the specific selection of the bicyclic organic compound is changed, and the specific parameters of the diaphragm are shown in Table 1-1.

[0151] Table 1-1 Example 4 The experiment was conducted in accordance with Example 1, except that filler particles (composed of alumina) were added to the organic coating. The organic particles accounted for 75% of the weight of the organic coating, and the filler particles accounted for 20% of the weight of the organic coating. The adhesion between the separator and the positive electrode was 13.1 N / m, and the adhesion between the separator and the negative electrode was 18.2 N / m.

[0152] Example 5 group Example 5a The experiment was conducted in accordance with Example 1, except that the first polymer particle was a second particle with an average particle size of 0.8 μm. The second particle was immersed in the test electrolyte for 4 hours at 65°C. The mass swelling degree of the second particle was 172%. The adhesion force between the separator and the positive electrode was 14.5 N / m, and the adhesion force between the separator and the negative electrode was 18.6 N / m.

[0153] Example 5b The experiment was conducted in accordance with Example 1, except that the average particle size of the primary particles of the first particle was 0.17 μm, the average particle size of the secondary particles of the first particle was 4.2 μm, and there were 44 secondary particles in any 100 μm × 100 μm area on the surface of the first coating layer. The first particle was immersed in the test electrolyte at 65°C for 4 hours, and the mass swelling degree of the first particle was 62%. The second particle was composed of PVDF, the average particle size of the second particle was 0.3 μm, and the second particle was immersed in the test electrolyte at 65°C for 4 hours, and the mass swelling degree of the second particle was 73%. The adhesion force between the separator and the positive electrode was 11.3 N / m, and the adhesion force between the separator and the negative electrode was 18.3 N / m.

[0154] Example 5c The experiment was conducted in accordance with Example 1, except that the first particle was composed of PMMA, the average particle size of the primary particles of the first particle was 0.38 μm, the average particle size of the secondary particles of the first particle was 16.3 μm, and there were 21 secondary particles in any 100 μm × 100 μm area on the surface of the first coating layer. The first particle was immersed in the test electrolyte at 65°C for 4 hours, and the mass swelling degree of the first particle was 98%. The average particle size of the second particle was 4.5 μm. The second particle was immersed in the test electrolyte at 65°C for 4 hours, and the mass swelling degree of the second particle was 168%. The second polymer was composed of poly(p-phenylene terephthalamide). The adhesion force between the separator and the positive electrode was 13.8 N / m, and the adhesion force between the separator and the negative electrode was 16.7 N / m.

[0155] Example 5d The process is the same as in Example 1, except that the second coating layer is applied using a striped coating method (e.g., ...). Figure 7 As shown in the figure, the adhesion force between the separator and the positive electrode is 14.6 N / m, and the adhesion force between the separator and the negative electrode is 16.2 N / m.

[0156] Example 6 group This set of embodiments is used to illustrate the effect of changing the number of secondary particles in any 100μm×100μm area on the surface of the first coating layer by adjusting one or more of the following: the coverage of the first polymer particles on the surface of the carrier layer, the average particle size of the first polymer particles, the average particle size of the primary particles of the first particle, and the average particle size of the secondary particles of the first particle.

[0157] This embodiment is based on Embodiment 1, except that the number of secondary particles in any 100μm×100μm area on the surface of the first coating layer is changed, as detailed in Tables 1-2.

[0158] Table 1-2 Example 7 group Example 7a The experiment was carried out in accordance with Example 1, except that the thickness of the organic coating was 0.5 μm, the thickness of the second adhesive layer was 4 μm, the adhesion between the separator and the positive electrode was 14.3 N / m, and the adhesion between the separator and the negative electrode was 19.5 N / m.

[0159] Example 7b The experiment was carried out in accordance with Example 1, except that the thickness of the organic coating was 4 μm, the thickness of the second adhesive layer was 0.75 μm, the adhesion between the separator and the positive electrode was 14.3 N / m, and the adhesion between the separator and the negative electrode was 16.1 N / m.

[0160] Example 8 group This set of examples illustrates the effect of changes in the proportion of the orthographic projection area of ​​the pores in the second coating layer onto the carrier layer to the total area of ​​the carrier layer surface.

[0161] This embodiment is based on Embodiment 1, except that the area ratio of the orthogonal projection area of ​​the pores in the second coating layer on the carrier layer to the total area of ​​the carrier layer surface is changed, as shown in Tables 1-3.

[0162] Table 1-3 Example 9 The procedure was carried out in accordance with Example 1, except that no heat-resistant particles were added to the second coating layer, the adhesion between the separator and the positive electrode was 14.2 N / m, and the adhesion between the separator and the negative electrode was 23 N / m.

[0163] Example 10 group This set of embodiments is used to illustrate how, by selecting one or more of different first and second particles and carrier layer thicknesses, (H) 1 -H 2 ) / H 1 The impact of changes.

[0164] This embodiment group is carried out with reference to Embodiment 1, except that (H) is changed. 1 -H 2 ) / H 1 For details, please refer to Table 1-4.

[0165] Table 1-4 Example 11 group This set of examples is used to illustrate when L 1 / C 1 The impact of changes.

[0166] This embodiment is based on Embodiment 1, except that a groove is provided on the first surface of the negative electrode, changing L. 1 / C 1 For details, please refer to Table 1-5.

[0167] Table 1-5 Comparative Example 1 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.

[0168] Comparative Example 2 The procedure was carried out in accordance with Example 1, except that the components of the organic particles were replaced with 2-mercaptoimidazole and tetramercaptobenzene.

[0169] Comparative Example 3 The procedure is carried out in accordance with Example 1, except that the first adhesive layer and the second adhesive layer are not provided.

[0170] Test case The batteries prepared by the examples and comparative examples were tested as follows.

[0171] 1. High-rate lithium plating test The lithium-ion battery was placed at 25℃±3℃ and charged at a constant current of 4C to the upper limit voltage (4.53V). Then it was charged at a constant voltage of 4.53V to 0.05C and left to stand for 5 minutes. Next, it was discharged at a constant current of 0.5C to 3V and left to stand for 5 minutes. This is one charge-discharge cycle. This charge / discharge cycle was repeated 20 times. After 20 cycles, the battery was disassembled to check the lithium plating on the negative electrode. The total number of folds of the battery was 24. The result is expressed by the number of folds in which lithium plating occurred. For example, if black spots or lithium plating appeared on 2 folds of the negative electrode, the result is represented by "2".

[0172] 2. Room temperature cycling performance At 25℃±2℃, the battery was charged at 0.7C constant current and constant voltage to 4.53V, cut off at 0.05C, and then discharged at 0.2C constant current to 3.0V. The initial discharge capacity was recorded as C0. After resting for 10 minutes, the cycle was repeated as follows: 3C constant current and constant voltage charging to 4.25V, cut off at 2C, then 2C constant current and constant voltage charging to 4.48V, cut off at 1.5C, then 1.5C constant current and constant voltage charging to 4.53V, cut off at 0.18C, rested for 5 minutes, and then discharged at 0.7C to 3.0V. After 800 cycles, the battery was charged at 0.7C constant current and constant voltage to 4.53V, cut off at 0.05C, and the final thickness P1 was recorded. Then, the battery was discharged at 0.2C constant current to 3.0V, and the discharge capacity at this point was recorded as C1. The capacity retention rate (%) is calculated as (C1 / C0) × 100%. 3. High-temperature cycling performance The lithium-ion battery was placed at 45℃±3℃, then charged at a constant current of 1C to the upper limit voltage (4.5V), then charged at a constant voltage of 4.53V to 0.05C, and left to stand for 5 minutes; next, it was discharged at a constant current of 0.5C to 3V, and the discharge capacity at this point was recorded as Q1. After standing for 5 minutes, this constituted one charge-discharge cycle. After 500 charge / discharge cycles, the discharge capacity Q2 of the lithium-ion battery after 500T cycles was recorded. The capacity retention rate (%) was then calculated as (Q2 / Q1)×100%.

[0173] The results are recorded in Table 2.

[0174] Table 2 As can be seen from Table 2, by comparing the comparative examples and the embodiments, the lithium plating of the battery prepared by the separator in the embodiments is significantly improved at high rates, and the high-temperature cycling capacity retention rate and the room-temperature cycling capacity retention rate are significantly improved. This indicates that by adding organic particles including bicyclic organic matter to the organic coating, and designing the adhesive layers on both sides of the carrier layer to have different structures, the lithium plating of the battery is improved, and the room-temperature cycling performance and high-temperature cycling performance of the battery are enhanced.

[0175] 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 membrane includes a carrier layer, a first adhesive layer, and a second adhesive layer. The first adhesive layer is located on one side of the carrier layer, and the second adhesive layer is located on the other side of the carrier layer. The carrier layer includes a substrate layer and an organic coating on at least one side of the substrate layer. The organic coating includes organic particles, and the organic particles are composed of bicyclic organic compounds. The bicyclic organic compounds include a bicyclic structure formed by a 2-mercaptoimidazole ring and a benzene ring sharing two adjacent carbon atoms. The first adhesive layer includes first polymer particles, and the second adhesive layer includes a porous structure formed by a second polymer.

2. The diaphragm according to claim 1, wherein, The organic coating is located on one side surface of the substrate layer, the first adhesive layer is located on the surface of the organic coating, and the second adhesive layer is located on the other side surface of the substrate layer; And / or, 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.

3. The diaphragm according to claim 1, wherein, The second coating layer can be applied continuously or intermittently; And / or, the first adhesive layer has a coverage of 5%-60% on the surface of the carrier layer; And / or, the area of ​​the orthographic projection of the pores in the second coating layer onto the carrier layer accounts for 10%-90% of the total area of ​​the carrier layer surface, preferably 25%-75%; And / or, the average particle size of the primary particles of the first polymer particle is 0.1 μm-5 μm; And / or, the first polymer particle includes at least one of a first particle and a second particle, wherein the first particle is an agglomerated polymer particle and the second particle is a dispersed polymer particle; And / or, the bicyclic organic compound is 2-mercaptobenzimidazole or a 2-mercaptobenzimidazole derivative.

4. The diaphragm according to claim 3, wherein, The first particle includes secondary particles formed by the aggregation of primary particles. Within any 100μm×100μm area on the surface of the first coating layer, the number of secondary particles is 20-1000, preferably 30-100. And / or, the first particle includes secondary particles formed by the aggregation of primary particles, wherein the average particle size of the primary particles of the first particle is 0.1 μm-0.4 μm, and the average particle size of the secondary particles is 2 μm-30 μm, preferably, the average particle size of the secondary particles is 4 μm-28 μm; And / or, the average particle size of the second particle is 0.1 μm-5 μm, preferably 0.3 μm-1.2 μm; And / or, the first polymer particle includes at least a first particle; 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.

5. The diaphragm according to claim 1, wherein, The components of the first polymer particles include one or more of the following: fluoropolymers, acrylate polymers, polyacrylonitrile, polyacrylic acid, polyvinyl alcohol, modified polyvinyl alcohol, polyvinyl acetate, polyacrylamide, phenolic resin, epoxy resin, ethylene-vinyl acetate copolymer, lithium polystyrene sulfonate, polyethylene oxide, cyanoethyl polyvinyl alcohol, butadiene-acrylonitrile copolymer and its derivatives, aramid, modified aramid, phenolic resin, modified phenolic resin, polyimide, polyetherimide, and modified polyimide. And / or, the second polymer comprises one or more of the following: fluoropolymers, polyacrylonitrile, polymethyl methacrylate, polyacrylic acid, polyvinyl alcohol, modified polyvinyl alcohol, polyvinyl acetate, polyacrylamide, phenolic resin, epoxy resin, ethylene-vinyl acetate copolymer, multi-component acrylic copolymer, lithium polystyrene sulfonate, polyethylene oxide, cyanoethyl polyvinyl alcohol, butadiene-acrylonitrile copolymer and its derivatives, aramid, phenolic resin, modified phenolic resin, polyimide, polyetherimide, and modified polyimide; And / or, the thickness of the organic coating is 0.2 μm-5 μm; And / or, the thickness of the first adhesive layer is 0.5μm-5μm; And / or, the thickness of the second adhesive layer is 0.5μm-5μm.

6. The diaphragm according to claim 1, wherein, At 65°C, the first polymer particles are immersed in the test electrolyte for 4 hours. The mass swelling degree of the first polymer particles is 2%-250%, preferably 20%-100%. The test electrolyte is composed of lithium hexafluorophosphate, ethylene carbonate, methyl ethyl carbonate and dimethyl carbonate. The concentration of lithium hexafluorophosphate is 1 mol / L, and the volume ratio of ethylene carbonate, methyl ethyl carbonate and dimethyl carbonate is 1:1:

1. And / or, the first polymer particle is composed of an acrylate polymer, and the glass transition temperature of the first polymer particle is 30℃-100℃. And / or, the composition of the first polymer particles is a fluoropolymer, and the melting point temperature of the first polymer particles is 120℃-180℃; And / or, the second coating layer comprises a fluoropolymer with a melting point of 120°C-180°C; And / or, the second coating layer further includes heat-resistant particles, the heat-resistant particles comprising one or more of the following: 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, aluminum nitride, boron nitride, zirconium titanate, barium titanate, magnesium fluoride, melamine cyanurate, 1,3,5-triazine-2,4,6-triamine, melamine thiocyanate, uracil, cytosine, guanine, 2-mercaptobenzimidazole, 2-mercaptobenzimidazole derivatives, N,N'-bis(β-naphthyl)-p-phenylenediamine, and 4-amino-2,6-dihydroxypyrimidine. And / or, the second coating layer further includes heat-resistant particles, wherein the weight percentage of the heat-resistant particles in the second coating layer is 0.1%-70%; And / or, the organic particles in the organic coating account for 50%-99% by weight; And / or, the organic coating further includes a first adhesive, the first adhesive comprising one or more of polyvinyl alcohol, styrene-butadiene rubber, ethylene-vinyl acetate copolymer, sodium carboxymethyl cellulose, polyvinylpyrrolidone, acrylate adhesives, styrene-acrylic latex, polyacrylonitrile, polyacrylic acid, polyvinyl acetate, polyurethane, fluoropolymers, or copolymers derived from the above polymers; And / or, the organic coating further includes a first binder, wherein the weight percentage of the first binder in the organic coating is 1%-10%; And / or, the organic coating further includes optional filler particles, wherein the filler particles constitute 0%-49% by weight in the organic coating. Preferably, the filler particles are composed of one or more of 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, aluminum nitride, boron nitride, zirconium titanate, barium titanate, magnesium fluoride, melamine cyanurate, 1,3,5-triazine-2,4,6-triamine, melamine thiocyanate, uracil, cytosine, guanine, N,N'-di(β-naphthyl)-p-phenylenediamine, and 4-amino-2,6-dihydroxypyrimidine.

7. The diaphragm according to any one of claims 1-6, wherein, The thickness of the substrate layer is 3.5μm-16μm, preferably 4μm-9μm; And / or, the porosity of the substrate layer is 30%-75%, preferably 38%-55%; And / or, the average pore size of the substrate layer is 30nm-55nm; 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).

8. A battery, characterized in that, The battery includes a positive electrode, a negative electrode, and a separator according to any one of claims 1-7, wherein the separator is located between the positive electrode and the negative electrode.

9. The battery according to claim 8, wherein, The adhesion force between the diaphragm and the positive electrode sheet is 2N / m-50N / m; And / or, the adhesion force between the diaphragm and the negative electrode sheet is 2N / m-50N / m; And / or, the positive electrode corresponds to the first coating layer, and the negative electrode corresponds to the second coating layer; And / or, the negative electrode sheet includes a negative electrode current collector and a negative electrode active layer located on at least one side surface of the negative electrode current collector, wherein the surface of the negative electrode active layer away from the negative electrode current collector is a first surface, and the first surface includes a plurality of grooves; And / or, the battery includes a casing and a cell located in the receiving space formed by the casing, the cell including an electrolyte and an electrode assembly formed by stacking and winding the positive electrode, the separator, and the negative electrode, the electrode assembly including a flat region and an arc region, and the separator satisfying the following relationship: 0.1≤(H 1 -H 2 ) / H 1 ≤0.9, where H 1 H represents the thickness of the diaphragm located in the arc region, in μm. 2 The thickness of the diaphragm located in the flat region is expressed in μm.

10. The battery according to claim 9, wherein, The negative electrode sheet corresponds to one side of the second adhesive layer in the separator, and the battery satisfies the following relationship: 0.1≤L 1 / C 1 ≤1, where L 1 C represents the coverage of the groove on the first surface. 1 The area of ​​the orthographic projection of the pores in the second adhesive layer onto the carrier layer is the percentage of the total area of ​​the carrier layer surface.

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