A separator and a battery

Abstract

The application provides a separator and a battery, the separator comprising a substrate layer and a coating layer on one side or both sides of the substrate layer, the coating layer comprising a first coating layer and a second coating layer, the first coating layer comprising first particles with an organic compound, and a unit molecular structure of the organic compound comprising at least one of a carbon-carbon double bond, a phosphorus-oxygen double bond, a carbon-nitrogen double bond, a carbon-sulfur double bond and a carbon-oxygen double bond; the second coating layer being a porous structure formed by a fluorine-containing polymer as a continuous phase, and a surface of the second coating layer comprising through holes, and in an area of 100 mu m*100 mu m on the surface of the second coating layer, a ratio of a projected area of the through holes on the substrate layer and / or the first coating layer in the surface area of the separator is 10%-90%, and the battery comprises the separator, the separator and the battery can improve the stability of the CEI film at high temperature, reduce or even avoid the rupture of the CEI film, and improve the high-temperature intermittent cycle capacity retention rate and the recovery capacity retention rate after high-temperature storage of the battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a separator and a battery comprising the same. BACKGROUND

[0002] Lithium ion batteries have been widely used in the fields of smart phones, tablet computers, smart wear, electric tools and electric vehicles due to their high energy density, long cycle life, no memory effect and green environmental protection. In order to meet the needs of consumers, one of the direct strategies to improve the energy density of the battery is to raise the charging cut-off voltage of the lithium battery. However, due to the characteristics of the positive active material, the positive active particles are extremely unstable after being delithiated beyond the platform voltage, especially under high temperature test conditions, the reaction is intensified, which is easy to cause the collapse of the structure of the active particles and affect the test performance. The stability of the positive active particles under high voltage has become an important problem encountered in the development of high energy density system lithium ion batteries. SUMMARY

[0003] It is found through research that the electrolyte interface (CEI) on the surface of the positive electrode material of the lithium ion battery is prone to rupture under high temperature environment. After the rupture, the electrolyte cannot prevent direct contact with high-activity ions (such as Co 4+ , Fe 3+ , Mn 2+ , Ni 3+ , Al 3+ , Ti 4+ ), which triggers a continuous side reaction, causing the interface performance between the separator and the positive electrode to deteriorate, and further accelerating the crack and structure collapse of the positive active particles, reducing the high-temperature intermittent cycle capacity retention rate and the recovery capacity retention rate after high-temperature storage of the lithium ion battery.

[0004] In order to solve the technical problem that the electrolyte interface (CEI) on the surface of the positive electrode material of the lithium ion battery is prone to rupture under high temperature environment, causing the interface performance between the separator and the positive electrode to deteriorate, the present application provides a separator and a battery comprising the same. The separator of the present application can dissociate organic matter containing electron-deficient groups involved in the formation of the CEI film, and the CEI film formed with the participation of the organic matter containing electron-deficient groups has good high-temperature resistance, which can improve the stability of the CEI film under high temperature, reduce or even avoid the rupture of the CEI film, improve the interface performance between the separator and the positive electrode, and improve the high-temperature intermittent cycle capacity retention rate and the recovery capacity retention rate after high-temperature storage of the battery.

[0005] The first aspect of the present application provides a separator, the separator comprising a substrate layer and a coating layer located on one side or both sides of the substrate layer, the coating layer comprising a first coating layer and a second coating layer, the first coating layer being located on the surface of the substrate layer, and the second coating layer being located on the surface of the first coating layer, the first coating layer comprising first particles, the first particles being composed of an organic compound, the organic compound comprising one or more of a carbon-carbon double bond, a phosphorus-oxygen double bond, a carbon-nitrogen double bond, a carbon-sulfur double bond, and a carbon-oxygen double bond in the unit molecular structure of the organic compound; and the second coating layer being a porous structure formed by a fluorine-containing polymer as a continuous phase, the surface of the second coating layer comprising through holes, and the area of the through holes on the substrate layer and / or the first coating layer in the surface area of the separator being 10%-90% in the orthogonal projection area in the surface area of the separator.

[0006] The second aspect of the present application provides a battery, the battery comprising a positive electrode sheet and the separator of the first aspect of the present application, the positive electrode sheet comprising a positive electrode current collector and a positive electrode active layer located on one side or both sides of the positive electrode current collector, the coating layer corresponding to the positive electrode active layer.

[0007] Compared with the prior art, the present application has at least the following advantages:

[0008] The present application provides a separator, the separator comprising a substrate layer and a coating layer located on one side or both sides of the substrate layer, the coating layer comprising a first coating layer and a second coating layer, the first coating layer being located on the surface of the substrate layer, and the second coating layer being located on the surface of the first coating layer, the first coating layer comprising first particles, the first particles being composed of an organic compound, the organic compound comprising one or more of a carbon-carbon double bond, a phosphorus-oxygen double bond, a carbon-nitrogen double bond, a carbon-sulfur double bond, and a carbon-oxygen double bond in the unit molecular structure of the organic compound; and the second coating layer being a porous structure formed by a fluorine-containing polymer as a continuous phase, the surface of the second coating layer comprising through holes, and the area of the through holes on the substrate layer and / or the first coating layer in the surface area of the separator being 10%-90% in the orthogonal projection area in the surface area of the separator.

[0009] Other features and advantages of the present application will be described in detail in the following specific embodiments.

[0010] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as the exact dimensions are not to be construed as being critical to the patentability of the invention. Ranges can be expressed as from about one particular value to about another particular value. When such a range is recited, it is to be construed as including single values within the range. The endpoints of the ranges and any value between the endpoints are also specifically included as if specifically stated. Ranges are also inclusive of the endpoints. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 One of the cross-sectional views of the diaphragm of the present application.

[0012] Figure 2 One of the cross-sectional views of the diaphragm of the present application.

[0013] Figure 3 One of the cross-sectional views of the diaphragm of the present application.

[0014] Figure 4 One of the cross-sectional views of the cathode sheet of the present application.

[0015] Figure 5 One of the cross-sectional views of the cathode sheet of the present application. DETAILED DESCRIPTION

[0016] The specific embodiments of the present application will now be described in detail below. It should be appreciated that the detailed description of the specific embodiments is merely intended for explanation and illustration and is not intended to limit the present application. In this document, the data ranges include the endpoints unless otherwise indicated.

[0017] It should be noted that the "first", "second", and the like designations in the present application are only used to distinguish different substances or usage manners, and do not represent the difference in order.

[0018] The first aspect of the present application provides a separator, the separator comprising a substrate layer and a coating layer located on one side or both sides of the substrate layer, the coating layer comprising a first coating layer and a second coating layer, the first coating layer being located on the surface of the substrate layer, the second coating layer being located on the surface of the first coating layer, the first coating layer comprising first particles, the first particles comprising an organic compound, the unit molecular structure of the organic compound comprising one or more of a carbon-carbon double bond, a phosphorus-oxygen double bond, a carbon-nitrogen double bond, a carbon-sulfur double bond and a carbon-oxygen double bond; the second coating layer being a porous structure formed by a fluorine-containing polymer as a continuous phase, the surface of the second coating layer comprising through holes, the area of the through holes on the substrate layer and / or the first coating layer in the surface area of the separator being 10%-90%, for example 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90% or within a range between any two of the above values.

[0019] In the present application, as shown in Figure 1 、 Figure 2 and Figure 3 , the separator 4 comprises a substrate layer 3 and a coating layer located on one side (as shown in Figure 1 and Figure 2 ) or both sides (as shown in Figure 3 ) of the substrate layer, the coating layer comprising a first coating layer 1 and a second coating layer 2, the first coating layer being located on the surface of the substrate layer, the second coating layer being located on the surface of the first coating layer.

[0020] The surface of one side or both sides of the base material layer of the diaphragm is coated with a coating layer including a first coating layer and a second coating layer, the first coating layer includes first particles, the composition of the first particles is an organic compound, the unit molecular structure of the organic compound includes carbon-carbon double bond, phosphorus-oxygen double bond, carbon-nitrogen double bond, carbon-sulfur double bond and carbon-oxygen double bond electron-deficient groups, when the battery is in a high temperature state, the first particles in the first coating layer can be dissolved and dissociated to form organic matter containing carbon-carbon double bond, phosphorus-oxygen double bond, carbon-nitrogen double bond, carbon-sulfur double bond or carbon-oxygen double bond electron-deficient groups, these organic matter containing electron-deficient groups quickly diffuse to the interface between the diaphragm and the positive electrode sheet, participate in the CEI film forming reaction, so that the CEI film has excellent high temperature resistance and is not easy to crack, thereby continuously and effectively isolating the electrolyte from the surface of the high-activity positive electrode sheet, inhibiting the occurrence of side reactions, improving the interface performance between the diaphragm and the positive electrode sheet, and reducing the interface impedance. The second coating layer is a porous structure formed by a fluorine-containing polymer as a continuous phase, and the surface of the second coating layer includes through holes, and at the same time, the proportion of the area of the through hole on the surface of the second coating layer in the surface area of the diaphragm is controlled in the above range, when the surface of the first coating layer has the second coating layer, the organic matter containing electron-deficient groups is facilitated to quickly and directionally diffuse from the first coating layer of the diaphragm to the interface of the positive electrode sheet through the through hole, which creates favorable conditions for the organic matter containing electron-deficient groups to participate in the formation of the CEI film, and also limits its excessive diffusion in the electrolyte outside the interface, avoiding its influence on other performances of the battery, and when the proportion of the through hole is less than the above range, the diffusion channel is reduced, which is not conducive to the diffusion of the organic matter containing electron-deficient groups to the interface between the diaphragm and the positive electrode sheet, and when the proportion of the through hole is greater than the above range, the adhesion between the diaphragm and the electrode sheet is not conducive, which reduces the interface performance between the diaphragm and the electrode sheet. The diaphragm of the present application can participate in improving the heat resistance of the CEI film, reducing the risk of CEI film damage at high temperature, improving the high-temperature intermittent cycle capacity retention rate of the battery, reducing the irreversible capacity loss of the battery during high-temperature storage, and improving the recovery capacity retention rate after high-temperature storage.

[0021] It can be understood that in the present application, the first particles in the first coating layer can be dissolved and dissociated to form organic matter containing carbon-carbon double bond, phosphorus-oxygen double bond, carbon-nitrogen double bond, carbon-sulfur double bond or carbon-oxygen double bond electron-deficient groups, which is not present in the form of a group alone, and the organic matter can be one or more of an organic compound, a monomer, and an ion.

[0022] In the present application, the dissolution of the first particles does not mean that the particle state of all the first particles disappears or that all the first particles are completely dissolved, but that the particle state of a single first particle completely disappears or partially disappears, and it can also be that part of the group in a single first particle is dissolved out, and the particle state of a single first particle can also be completely retained.

[0023] In the present application, the through hole refers to a hole that penetrates from one side surface of the second coating layer to the other side surface of the second coating layer in the thickness direction of the separator. It can be understood that in the surface SEM image of the separator, the first coating layer and / or the substrate layer can be seen through the through hole.

[0024] In the present application, in the area of 100 μm x 100 μm of the surface of the second coating layer, the ratio of the area of the orthographic projection of the through hole on the substrate layer and / or the first coating layer in the surface area of the separator can be measured by a scanning electron microscope (SEM), specifically: the surface micrograph of the separator is obtained by SEM, an area of 100 μm x 100 μm of the surface of the second coating layer is randomly selected as an analysis area, the area is divided into 400 x 400 uniform squares (it can be understood that the above analysis area is also the area of the surface of the separator, so the number of squares Y of the surface of the separator is 400 x 400), if the coverage area of the through hole in the square exceeds half of the area of the square, it means that the square is occupied by the through hole, otherwise it means that the square is not occupied by the through hole, the number of squares occupied by the through hole is counted, the total number of squares occupied by the through hole is recorded as X, the area ratio is (X / Y) x 100%, the above operation is repeated 5 times, and the average of 5 times is taken as the final measurement result.

[0025] By setting the first particles containing electron-deficient groups on the separator and controlling the coverage of the through hole which facilitates the diffusion of organic matter containing electron-deficient groups, compared with the prior art, the high temperature resistance of the CEI film can be improved, the damage of the CEI film can be reduced or even avoided, and the high temperature intermittent cycle capacity retention rate and the recovery capacity retention rate after high temperature storage of the battery can be improved. In order to further improve the effect, one or more of the technical features can be further optimized.

[0026] In some embodiments, in the area of 100 μm x 100 μm of the surface of the second coating layer, the ratio of the area of the orthographic projection of the through hole on the substrate layer and / or the first coating layer in the surface area of the separator is 20%-80%.

[0027] In some embodiments, the coating layer includes the first coating layer and the second coating layer, and it can be understood that at this time the structure of the separator is that the first coating layer is located on one side or both sides of the surface of the substrate layer, and the second coating layer is located on the surface of the first coating layer (as shown in Figure 1 、 Figure 2 and Figure 3 , the first coating layer includes first particles, the composition of the first particles includes elemental nitrogen, elemental sulfur and elemental phosphorus, and the second coating layer includes fluorine-containing polymer, and the second coating layer includes elemental fluorine.

[0028] In some embodiments, the coating includes the first coating and the second coating, and the ratio of the weight of elemental fluorine to the sum of the weights of elemental nitrogen, elemental sulfur, and elemental phosphorus on the surface of the coating on the side of the coating away from the substrate layer is (0.25-3): 1, for example, 0.25: 1, 0.5: 1, 0.75: 1, 1: 1, 1.5: 1, 2: 1, 2.5: 1, 3: 1, or within a range between any two of the above values. The weight of elemental fluorine refers to the weight of all fluorine elements exposed on the surface of the coating, and the sum of the weights of elemental nitrogen, elemental sulfur, and elemental phosphorus refers to the total weight of the three elements exposed on the surface of the coating. It is understood that, since the surface of the second coating includes through holes, the through holes can expose the first coating and / or the substrate layer, and thus, when the coating includes the first coating and the second coating, the surface of the coating can include the surface of the second coating, the surface of the first coating. On the surface of the coating on the side of the coating away from the substrate layer, the elements exposed on the surface of the coating can include one or more of elemental nitrogen, elemental sulfur, and elemental phosphorus, and elemental fluorine. When the elements exposed on the surface of the coating on the side of the coating away from the substrate layer include one of elemental nitrogen, elemental sulfur, and elemental phosphorus, the sum of the weights of elemental nitrogen, elemental sulfur, and elemental phosphorus refers to the weight of the one element (i.e., one of elemental nitrogen, elemental sulfur, and elemental phosphorus); when the surface of the coating on the side of the coating away from the substrate layer includes multiple of elemental nitrogen, elemental sulfur, and elemental phosphorus, the sum of the weights of elemental nitrogen, elemental sulfur, and elemental phosphorus refers to the sum of the weights of the multiple elements (multiple of elemental nitrogen, elemental sulfur, and elemental phosphorus).

[0029] Specifically, when the coating includes a large number of through holes, the elements exposed on the surface of the coating should include not only the elements of the second coating but also the elements exposed through the pores of the second coating, so that the content of the elements exposed on the surface of the coating can reflect the overall performance of the coating and the interface performance between the separator and the pole piece.

[0030] By controlling the ratio of the weight of element fluorine to the sum of the weights of element nitrogen, element sulfur and element phosphorus in the surface of the first coating layer and the second coating layer away from the substrate layer within the above range, on the one hand, the electron-deficient groups of carbon-carbon double bond, phosphorus-oxygen double bond, carbon-nitrogen double bond, carbon-sulfur double bond or carbon-oxygen double bond and fluorine element can be further promoted to act on the CEI film, the high-temperature performance of the CEI film is improved, and the interface performance between the separator and the positive electrode sheet is improved. On the other hand, by using the electron-withdrawing property between the double bond (for example, one or more of carbon-carbon double bond, phosphorus-oxygen double bond, carbon-nitrogen double bond, carbon-sulfur double bond and carbon-oxygen double bond) formed by element fluorine and one or more of element nitrogen, element sulfur and element phosphorus, the adhesion between the first coating layer and the second coating layer under high temperature is improved, the interface performance between the separator and the electrode sheet under high temperature is improved, the structural stability of the separator is improved, the first coating layer and the second coating layer are prevented from separating, and the interface impedance is prevented from being too large in the high-temperature intermittent cycle process, thereby affecting the high-temperature intermittent cycle capacity retention rate.

[0031] In some embodiments, the coating layer includes the first coating layer and the second coating layer, and the ratio of the weight of element fluorine to the sum of the weights of element nitrogen, element sulfur and element phosphorus in the surface of the coating layer away from the substrate layer is (0.35-2):1.

[0032] In the present application, the coating layer includes the first coating layer and the second coating layer, and the ratio of the weight of element fluorine to the sum of the weights of element nitrogen, element sulfur and element phosphorus in the surface of the coating layer away from the substrate layer can be measured by an energy dispersive X-ray spectrometer (EDS). Specifically, first, the surface of the coating layer is cleaned with a solvent and dried, a standard sample containing element fluorine, element nitrogen, element sulfur and element phosphorus is used to calibrate the system, and EDS surface scanning analysis is performed on the surface of the coating layer away from the substrate layer under a scanning electron microscope (SEM) to obtain the weight a1 of element fluorine and the sum b1 of the weights of element nitrogen, element sulfur and element phosphorus, and the ratio a1:b1 of the weight of element fluorine to the sum of the weights of element nitrogen, element sulfur and element phosphorus is calculated.

[0033] In some embodiments, the thickness of the first coating layer is 0.2 μm-5 μm, for example, 0.2 μm, 1 μm, 1.5 μm, 1.8 μm, 2 μm, 2.5 μm, 2.8 μm, 3 μm, 3.5 μm, 3.8 μm, 4 μm, 4.5 μm, 5 μm or within a range formed by any two of the above values.

[0034] In some embodiments, the weight percentage of the first particles in the first coating layer is 90%-99%, for example, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or within a range formed by any two of the above values.

[0035] In some embodiments, the first particles have a median particle size Dv50 of 0.05-5 μm, for example 0.05 μm, 0.08 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 a range between any two of the aforementioned values. Controlling the median particle size of the first particles within the aforementioned range improves the softness of the first coating, thereby improving the adhesion of the separator to the electrode, maintaining the integrity of the electrode structure, improving the cycle performance of the battery at room temperature, while enhancing the adhesion strength between the first coating and the substrate layer and the second coating, maintaining the structural stability of the separator, reducing the cycle interface impedance between the separator and the electrode, and improving the cycle performance of the battery at room temperature.

[0036] In the present application, the median particle size Dv50 of the first particles refers to the particle size corresponding to 50% of the cumulative volume particle size distribution of the first particles arranged in ascending order of particle size. The median particle size Dv50 of the first particles can be measured using a Malvern Mastersizer 3000 laser particle size analyzer.

[0037] In some embodiments, the first particles have a specific surface area of 4 m 2 / g-35 m 2 / g, for example 4 m 2 / g, 6 m 2 / g, 10 m 2 / g, 12 m 2 / g, 14 m 2 / g, 16 m 2 / g, 18 m 2 / g, 20 m 2 / g, 30 m 2 / g, 35 m 2 / g, or within a range between any two of the aforementioned values. When the specific surface area of the first particles is controlled within the aforementioned range, the contact area between the first particles and the electrolyte is large, and the dissolution rate is accelerated. At high temperatures, atoms on the surface of the first particles are more likely to generate organic compounds containing electron-deficient groups, so that the organic compounds containing electron-deficient groups participate more quickly and more in the construction of the CEI film, forming a more high-temperature-resistant electrolyte film (CEI film), avoiding damage to the separator, and improving the high-temperature intermittent cycle capacity retention rate and the recovery capacity retention rate after high-temperature storage of the battery.

[0038] In some embodiments, in the unit structure of the organic compound, the sum of the number of carbon-carbon double bonds, phosphorus-oxygen double bonds, carbon-nitrogen double bonds, carbon-sulfur double bonds, and carbon-oxygen double bonds is 3-12, for example 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or within a range between any two of the aforementioned values.

[0039] The number of carbon-carbon double bonds, phosphorus-oxygen double bonds, carbon-nitrogen double bonds, carbon-sulfur double bonds, and carbon-oxygen double bonds in the unit structure of the organic compound is controlled within the above range, which on the one hand ensures the rigidity of the chemical structure of the organic compound, thereby improving the rigidity of the first particles and maintaining the structural stability of the first coating; on the other hand, the appropriate number of electron-deficient groups can promote the participation of the dissociated organic compounds in the CEI film-forming reaction, thereby improving the stability of the film formation; if the number of electron-deficient groups is too small, the rigidity of the particles is not enough, and the structural stability of the coating is poor; if the number of electron-deficient groups is too large, the chemical oxidation resistance of the particles is poor, which leads to the first coating being easily oxidized, increasing the side reactions of the electrolyte and causing gas generation after high-temperature storage.

[0040] In some embodiments, the organic compound comprises one or more of 1,3,5-triazine-2,4,6-triamine, melamine polyphosphate, melamine hydrobromide, melamine polyphosphates, sym-triaminotriazine, 2-(4-bromophenyl)-4,6-dimethyl-1,3,5-triazine, 2,4-diamino-6-dimethylamino-1,3,5-triazine, cyanuric chloride, melamine trithiocyanate, melamine cyanurate, 2-amino-4,6-methoxy-1,3,5-triazine, 1-(4,6-diamino-1,3,5-triazin-2-yl)guanidine, uracil, cytosine, 5-azacytosine, indole-3-propionic acid, N4-methylcytosine, 1-phenyl-3-methyl-5-pyrazolone, formaldehyde poly melamine hydrochloride, 2,4,6-triphenyl-1,3,5-triazine, 2-quinoline sulfonic acid and 2-quinoline sulfonate, 2,4,6-tris(2-pyridyl)triazine, tris(tribromophenoxy)triazine, dithiourea, 2,4-dimercapto-5,6-diaminopyrimidine, 4,6-dimethyl-2-mercaptopyrimidine, 1,3,4-thiadiazole-2-thione salt, coumarin-3-sulfonate, 3-methyl-1-phenyl-2-phospholene 1-oxide.

[0041] In some embodiments, the first coating comprises a binder, and the weight percentage of the binder in the first coating is 1%-10%, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or within a range between any two of the above values.

[0042] In some embodiments, the binder comprises one or more of polyvinyl alcohol, styrene-butadiene rubber, ethylene-vinyl acetate copolymer, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polymethyl methacrylate, polybutyl methacrylate, styrene-acrylic latex, polyacrylonitrile, polyethyl acrylate, polyvinyl acetate, polyacrylate, polyurethane polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, or a copolymer system derived from the above polymers.

[0043] In some embodiments, the second coating layer has a thickness of 0.5 μm to 5 μm, for example, 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.8 μm, 2 μm, 2.2 μm, 2.5 μm, 2.8 μm, 3 μm, 3.5 μm, 3.8 μm, 4 μm, 4.5 μm, 5 μm, or within a range between any two of the above values.

[0044] In some embodiments, the fluoropolymer in the second coating layer accounts for 70% to 100% by weight, for example, 70%, 72%, 75%, 78%, 80%, 83%, 85%, 88%, 90%, 92%, 95%, 98%, 100%, or within a range between any two of the above values.

[0045] In some embodiments, the second coating layer further comprises one or more of alumina, boehmite, magnesium hydroxide, magnesium oxide, boron nitride, aluminum nitride, and silicon oxide, and the one or more of alumina, boehmite, magnesium hydroxide, magnesium oxide, boron nitride, aluminum nitride, and silicon oxide in the second coating layer accounts for 0% to 30% by weight, for example, 0%, 2%, 5%, 7%, 10%, 12%, 15%, 18%, 20%, 25%, 28%, 30%, 35%, or within a range between any two of the above values.

[0046] In some embodiments, the fluoropolymer comprises one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0047] In some embodiments, the ratio of the thickness of the first coating layer to the thickness of the second coating layer is 0.4 to 3, for example, 0.4, 0.8, 1.2, 1.6, 2, 2.4, 2.8, 3, or within a range between any two of the above values. Controlling the ratio of the thickness of the first coating layer to the thickness of the second coating layer within the above range can shorten the path of the electron-deficient group-containing organic matter produced by the dissolution of the first particles in the electrolyte under high temperature conditions to diffuse to the positive electrode sheet via the second coating layer, ensuring that the electron-deficient group-containing organic matter can smoothly pass through the second coating layer and reach the positive electrode sheet side to participate in the film-forming reaction of the CEI film.

[0048] In some embodiments, the coating layer is located on one side surface of the substrate layer, and the other side surface of the substrate layer comprises a third coating layer (as shown in Figure 1 and Figure 2 ).

[0049] In some embodiments, the third coating and the second coating are the same, the surface of the third coating comprises through-holes (e.g., as shown in FIG. 6). It should be understood that the same here refers to the same composition and structure of the coating, but the thickness of the coating can be the same or different. Figure 1

[0050] In some embodiments, the third coating and the second coating are different, the surface of the third coating does not comprise through-holes (e.g., as shown in FIG. 6). Figure 2

[0051] In some embodiments, the third coating comprises a first polymer and filler particles, the mass percentage of the first polymer is 20-70%, for example, 20%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or within a range between any two of the above values, and the mass percentage of the filler particles is 30-80%, for example, 30%, 40%, 50%, 60%, 70%, 80%, or within a range between any two of the above values, based on the total mass of the polymer coating.

[0052] In some embodiments, the first polymer comprises one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyfluoroethylene, polyhexafluoropropylene, fluorovinyl-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, nitrile rubber, poly(p-phenyleneterephthalamide), poly(m-phenyleneterephthalamide), and one or more of copolymer systems derived from the above polymers.

[0053] In some embodiments, the filler particles comprise one or more of boehmite, alumina, barium sulfate, magnesium oxide, magnesium hydroxide, silicon dioxide, tin dioxide, titanium oxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, nickel oxide, cerium oxide, zirconium titanate, barium titanate, magnesium fluoride, 1,3,5-triazine-2,4,6-triamine, melamine trithiocyanate, melamine cyanurate, sym-trisamino triazine, 2-(4-bromophenyl)-4,6-dimethyl-1,3,5-triazine, 1-(4,6-diamino-1,3,5-triazin-2-yl) guanidine, 2,4-diamino-6-dimethylamino-1,3,5-triazine, trichloro cyanuric acid, 2,4,6-tris(2-pyridyl) triazine, 2,4,6-triphenyl-1,3,5-triazine, tris(tribromophenoxy) triazine, 2-amino-4,6-methoxy-1,3,5-triazine, uracil, and cytosine.

[0054] ​​In some embodiments, the substrate layer has a porosity of 25-70%, such as 25%, 30%, 35%, 37%, 40%, 45%, 47%, 50%, 53%, 55%, 60%, 62%, 65%, 70%, or a range between any two of the aforementioned values.

[0055] In some embodiments, the substrate layer has a thickness of 2-10 μm, such as 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or a range between any two of the aforementioned values.

[0056] In some embodiments, the substrate layer comprises one or more of polyolefin, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinyl chloride, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyethylene terephthalate, polybutylene terephthalate, poly paraphenylene terephthalamide, poly-m-phenylene isophthalamide, and derivatives of the aforementioned polymers.

[0057] In some embodiments, a 1.5 g membrane is soaked in 5 mL of a first solution for 2 h in an environment of 85 °C, the membrane has an air permeability value increment of 20-400 sec / 100 cc, such as 20 sec / 100 cc, 40 sec / 100 cc, 60 sec / 100 cc, 80 sec / 100 cc, 100 sec / 100 cc, 120 sec / 100 cc, 140 sec / 100 cc, 160 sec / 100 cc, 180 sec / 100 cc, 200 sec / 100 cc, 220 sec / 100 cc, 250 sec / 100 cc, 260 sec / 100 cc, 300 sec / 100 cc, 320 sec / 100 cc, 340 sec / 100 cc, 380 sec / 100 cc, 400 sec / 100 cc, or a range between any two of the aforementioned values, and the first solution in which the membrane is soaked is a soaking solution, in which the sum of the weight percentages of elemental nitrogen, elemental sulfur, and elemental phosphorus is 500-20,000 ppm, such as 500 ppm, 1,000 ppm, 2,500 ppm, 5,000 ppm, 6,000 ppm, 8,000 ppm, 10,000 ppm, 12,000 ppm, 15,000 ppm, 18,000 ppm, 20,000 ppm, or a range between any two of the aforementioned values, wherein the first solution is composed of dimethyl carbonate, ethylene carbonate, and methyl ethyl carbonate, and the weight ratio of the dimethyl carbonate, the ethylene carbonate, and the methyl ethyl carbonate is 1:1:1.

[0058] The air permeability value increment of the separator is controlled to be 20-400 seconds / 100 cc when the separator is tested by using the above method, so that the lithium ions can pass through the separator normally, the charge and discharge capacity of the battery is maintained, and the sum of the weight proportions of the elements nitrogen, sulfur and phosphorus in the immersion solution in which the separator is immersed is controlled to be 500-20,000 ppm, so that the first particles in the first coating of the separator can dissociate to generate sufficient organic matter containing carbon-carbon double bond, phosphorus-oxygen double bond, carbon-nitrogen double bond, carbon-sulfur double bond or carbon-oxygen double bond electron-deficient group under high temperature, effectively participating in the CEI film formation and enhancing the heat resistance of the CEI film.

[0059] In the present application, the air permeability value increment of the separator is measured by the following method, specifically: three pieces of the separator with a weight of 1.5 g are cut longitudinally with a distance of 150 mm, the separator is placed in an air permeability tester for air permeability value testing, the average value of three test results is taken as the air permeability value A of the separator before immersion, with the unit of seconds / 100 cc, after the three pieces of the separator with a weight of 1.5 g are immersed in the first solution with a volume of 5 mL at 85°C for 2 h, the separator is taken out, placed on filter paper to absorb residual liquid, the surface of the separator is purged with nitrogen until completely dry, the separator is placed in an air permeability tester for air permeability value testing, the average value of three test results is taken as the air permeability value B of the separator after immersion, with the unit of seconds / 100 cc, the air permeability value increment of the separator is calculated by the formula B-A, with the unit of seconds / 100 cc.

[0060] In the present application, the sum of the weight proportions of the elements nitrogen, sulfur and phosphorus in the immersion solution is measured by the following method, specifically: 2 mL of the immersion solution is taken, the weight thereof is weighed as M1, ultrapure water is used to make up to 20 mL, ICP-MS is used to detect the element concentration in the solution (the detection wavelengths are: 174.27 nm for element nitrogen, 180.73 nm for element sulfur, and 178.22 nm for element phosphorus), and the proportion is calculated according to the formula: the sum of the weight proportions of element nitrogen, element sulfur and element phosphorus = [(C N +C S +C P )×(20 / 2) / M1], with the unit of μg / g (ppm), wherein C N is the element nitrogen concentration, with the unit of μg / mL, C S is the element sulfur concentration, with the unit of μg / mL, and C Pis the concentration of elemental phosphorus, expressed in μg / mL. It should be noted that the soaking solution may include one or more of elemental nitrogen, elemental sulfur and elemental phosphorus. When the soaking solution includes one of elemental nitrogen, elemental sulfur and elemental phosphorus, the sum of the weight proportions of the elemental nitrogen, elemental sulfur and elemental phosphorus refers to the weight proportion of the one element (i.e., one of elemental nitrogen, elemental sulfur and elemental phosphorus); when the soaking solution includes multiple elements of elemental nitrogen, elemental sulfur and elemental phosphorus, the sum of the weights of the elemental nitrogen, elemental sulfur and elemental phosphorus refers to the sum of the weights of multiple elements (multiple elements of elemental nitrogen, elemental sulfur and elemental phosphorus).

[0061] The second aspect of the present invention provides a battery, which includes a positive electrode sheet and the separator described in the first aspect of the present invention, the positive electrode sheet includes a positive electrode collector and a positive electrode active layer located on one side or both sides of the positive electrode collector, and the coating corresponds to the positive electrode active layer.

[0062] In the present invention, "the coating corresponds to the positive electrode active layer" means that when the coating is located on one surface of the substrate layer, the positive electrode active layer corresponds to the coated side of the separator, and the negative electrode active layer corresponds to the other side of the separator; when the coating is located on both surfaces of the substrate layer, the positive electrode active layer corresponds to either coated side of the separator, and the negative electrode active layer corresponds to the other side of the separator. In this case, the organic matter containing electron-deficient groups produced by the dissolution of the first particles at high temperature can quickly diffuse to the positive electrode sheet through the through-pores of the second coating, participate in the film-forming reaction of the CEI film, enhance the high-temperature resistance of the CEI film, and improve the interfacial stability between the separator and the positive electrode sheet, thereby improving the battery's high-temperature intermittent cycle capacity retention rate and the recovery capacity retention rate after high-temperature storage.

[0063] In some embodiments, as Figure 4 As shown, in the thickness direction K of the positive electrode sheet 5, the positive electrode sheet includes a first surface 52 and a second surface 53, the first surface corresponds to the coating, and the first surface includes a plurality of pits 51. The battery satisfies the following relationship: 0.005≤V1 / D1≤10 (V1 / D1 is, for example, 0.005, 0.01, 0.03, 0.05, 0.08, 0.1, 0.3, 0.5, 1, 1.3, 1.5, 1.8, 2, 3, 4, 5, 6, 7, 8, 9, 10 or is within the range of any two of the above values), wherein D1 is the Dv10 of the first particle, in μm, and V1 is the average volume of the pits, in mm 3, research found that the positive plate and the coating corresponding to the first surface set of regular pits, can enhance the electrolyte capacity of the positive active layer, and then increase the coating of the separator corresponding to the positive side of the first particle containing electron-deficient group organic matter in the dissolution amount, and the smaller the particle size of the first particle, the more the amount of electron-deficient group organic matter dissolved in the positive side of the first particle, but the pit volume is too large, the particle size of the first particle is too small, and the dissolution amount of the electron-deficient group organic matter is too large, which will lead to the gap between the separator and the positive plate, increase the risk of separator and positive plate delamination, therefore, when the Dv10 of the first particle and the average volume of the pit are controlled, the battery satisfies the above relationship, the electrolyte capacity of the positive active layer can be expanded, the dissolution amount of the electron-deficient group organic matter in the first particle on the positive side can be increased, and the delamination of the separator and the positive plate caused by excessive dissolution amount can be avoided, the advantages of appropriate gap between the separator and the positive plate are ensured, the interface impedance is avoided to increase, and the high-temperature intermittent cycle capacity retention rate and the recovery capacity retention rate after high-temperature storage of the battery are improved.

[0064] In some embodiments, the battery satisfies the following relationship: 0.05≤V1 / D1≤5.

[0065] In some embodiments, the Dv10 of the first particle is 0.01-0.5 μm, for example, 0.01 μm, 0.05 μm, 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.34 μm, 0.4 μm, 0.43 μm, 0.46 μm, 0.5 μm, or within a range consisting of any two of the above values.

[0066] In the present application, the Dv10 of the first particle refers to the particle size corresponding to the cumulative volume particle size distribution percentage of 10% when the particle size of the first particle is arranged from small to large. In the present application, the particle size Dv10 of the first particle can be measured by using a Malvern Mastersizer 3000 laser particle size analyzer.

[0067] In some embodiments, the average volume V1 of the pit is 0.001mm 3 -0.15mm 3 , for example, 0.001mm 3 , 0.005mm 3 , 0.01mm 3 , 0.015mm 3 , 0.02mm 3 , 0.025mm 3 , 0.03mm 3 , 0.035mm 3 , 0.04mm 30.045mm 3 0.05mm 3 0.1mm 3 0.13mm 3 0.15mm 3 or within a range between any two of the above values.

[0068] In some embodiments, the volume of the pits is measured by the following method: scanning the surface of the positive electrode sheet using a 3D optical profiler, when the pits have regular geometric shapes (such as cylinder, cone, cube, etc.), obtaining the depth, diameter or edge length of the pits, and obtaining the volume of the pits according to the volume calculation formula of the specific geometric shape, when the pits have irregular geometric shapes, drawing a circle that is tangent to the orthographic projection of the irregular pit on the first surface, measuring the diameter d thereof, combining the depth h of the irregular pit, and calculating the volume of the irregular pit according to the formula π(d / 2) 2 h, calculating the average value of the volume of 100 pits, which is the average volume of the pits.

[0069] In some embodiments, at least part of the first surface is recessed towards the second surface to form a plurality of pits, and a plurality of protrusions are correspondingly arranged on the second surface.

[0070] According to a specific embodiment, V1 is 0.001-0.15, D1 is 0.01-0.5, and the battery satisfies the following relationship: 0.005≤V1 / D1≤10.

[0071] According to a specific embodiment, V1 is 0.001-0.15, D1 is 0.01-0.5, and the battery satisfies the following relationship: 0.05≤V1 / D1≤5.

[0072] In some embodiments, the average depth of the pits is 2-30 μm, for example, 2 μm, 6 μm, 10 μm, 14 μm, 18 μm, 20 μm, 24 μm, 26 μm, 30 μm, or within a range between any two of the above values.

[0073] In some embodiments, the average depth of the pits is 3-20 μm.

[0074] In the present application, the depth of the pits is the vertical distance from the lowest point of the bottom of the pit to the plane on which the first surface is located along the thickness direction K (as shown by b in Figure 4 In the present application, the depth of the pits is the vertical distance from the lowest point of the bottom of the pit to the plane on which the first surface is located along the thickness direction K (as shown by b in

[0075] In some embodiments, the average distance between adjacent said pits is 100-500 μm, for example 100 μm, 120 μm, 150 μm, 180 μm, 200 μm, 230 μm, 250 μm, 280 μm, 300 μm, 350 μm, 380 μm, 400 μm, 430 μm, 450 μm, 500 μm or within a range defined by any two of the above values.

[0076] In the present application, the distance between adjacent said pits refers to the nearest distance between the edge lines of two adjacent pits (as shown by a in Figure 4 The average distance between adjacent said pits is calculated by counting the distance between 100 groups of adjacent pits and calculating the average value.

[0077] In some embodiments, as shown in Figure 5 The shape of the projection of said pits on said first surface is a regular figure (for example, a circle 511, an ellipse 512, a diamond 513, a rectangle 514, a square 515, etc.) or an irregular figure (for example, an island 516).

[0078] In some embodiments, the positive electrode active layer comprises a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder.

[0079] In some embodiments, the positive electrode active material comprises at least one of lithium nickelate, lithium titanate, lithium cobaltate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, and lithium manganate.

[0080] In some embodiments, the positive electrode active material comprises lithium cobaltate.

[0081] In some embodiments, the positive electrode conductive agent comprises at least one of conductive carbon black, carbon nanotubes, conductive graphite, and graphene.

[0082] In some embodiments, the positive electrode binder comprises at least one of polyvinylidene fluoride (PVDF), acrylic modified PVDF, polyacrylate polymer, acrylic polymer, polytetrafluoroethylene, polyacrylonitrile, polyimide, butadiene styrene rubber, and styrene butadiene rubber.

[0083] In some embodiments, the battery comprises a negative electrode sheet comprising a negative electrode current collector and a negative electrode active layer on one or both sides of the negative electrode current collector, the negative electrode active layer comprising a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder, the negative electrode active material comprising a silicon-based material comprising at least one of elemental silicon, a silicon oxide compound (for example, SiOx / C), a silicon-carbon composite (for example, Si / C), a silicon-nitrogen composite, and a silicon alloy.

[0084] The present application will be described in detail below by way of examples. The examples described in the present application are only a part of the examples of the present application, but not all the examples. Based on the examples in the present application, all other examples obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0085] Example 1

[0086] (1) Preparation of positive electrode sheet

[0087] Lithium cobaltate, binder polyvinylidene fluoride (PVDF 500), and conductive material (conductive carbon black: carbon nanotube = 2:1) were mixed in N-methyl pyrrolidone (NMP) solvent in a weight ratio of 96:2:2, and continuously stirred into a uniform and flowable positive electrode slurry under the action of a blender. Subsequently, the positive electrode slurry was coated on both sides of an aluminum foil with a thickness of 10 μm, dried in a vacuum oven at 120°C for 6 h, then rolled and cut to obtain a positive electrode sheet, and then a roll with protrusions was used to control the depth and density of the pits on the first surface of the positive electrode sheet to obtain a positive electrode sheet with regular pits, wherein the average volume of the pits was 0.4 mm 3 (i.e. V1 was 0.05), the average depth of the pits was 12 μm, the average distance between adjacent pits was 263 μm, and the shape of the orthographic projection of the pits on the first surface was circular.

[0088] (2) Preparation of negative electrode sheet

[0089] Graphite, silicon-carbon composite (Dv50 = 7 μm), conductive material (carbon black: carbon nanotube = 1:1), sodium carboxymethyl cellulose (CMC), and butadiene rubber were mixed in a water solvent in a weight ratio of 92:6:1:0.5:0.5, and continuously stirred into a uniform and flowable negative electrode slurry under the action of a blender. Subsequently, the slurry was coated on both sides of a current collector copper foil with a thickness of 10 μm, dried in a vacuum oven at 120°C for 6 h, then rolled and cut to obtain the desired negative electrode sheet.

[0090] (3) Preparation of electrolyte

[0091] In an argon-filled glove box (moisture <1 ppm, oxygen <1 ppm), ethylene carbonate, propylene carbonate, propyl propionate, and ethyl propionate solvents were mixed into a uniform solvent in a mass ratio of 15:15:50:20, and 16wt% LiPF6, 3wt% 1,3,6-hexanetricarbonitrile, and 19wt% fluoroethylene carbonate were slowly added. After stirring uniformly, the desired lithium ion battery electrolyte was obtained.

[0092] (4) Preparation of separator

[0093] 96 parts by weight of melamine cyanurate (first particles) and 4 parts by weight of polymethyl methacrylate (binder) are mixed in water, and after being stirred sufficiently, a mixed slurry with a solid content of 25% is obtained. The mixed slurry is coated on one side surface of a substrate layer by means of a gravure roll, and after passing through a multi-section oven at 60°C, a first coating layer is formed by drying. The thickness of the first coating layer is 2 μm. In the first coating layer, the sum of the number of carbon-carbon double bonds, phosphorus-oxygen double bonds, carbon-nitrogen double bonds, carbon-sulfur double bonds, and carbon-oxygen double bonds in the unit structure of the organic compound (melamine cyanurate) is 6. The median particle diameter Dv50 of the first particles is 0.8 μm, and the specific surface area of the first particles is 9.4 m 2 / g; PVDF (fluorine-containing polymer) is dissolved in a solvent DMAC, and after being stirred sufficiently, a solution is obtained. The solution is coated on the surface of the first coating layer and the other side surface of the substrate layer by means of a gravure roll, and then extracted by means of a water tank, dried at 60°C, and a second coating layer is formed on the surface of the first coating layer, and a third coating layer is formed on the other side surface of the substrate layer. The second coating layer and the third coating layer are porous structures formed of a continuous phase of polyvinylidene fluoride (PVDF). The weight ratio of the fluorine-containing polymer (i.e., polyvinylidene fluoride) in the second coating layer and the third coating layer is 100%. The surface of the second coating layer and the third coating layer includes through-holes. The thickness of the second coating layer and the third coating layer is 1 μm. The ratio of the thickness of the first coating layer to the thickness of the second coating layer is 2. In an area of 100 μm x 100 μm on the surface of the second coating layer, the ratio of the area of the orthographic projection of the through-holes on the substrate layer and / or the first coating layer to the surface area of the separator is 57.3%. The coating layer includes the first coating layer and the second coating layer. On the surface of the coating layer away from the substrate layer, the ratio of the weight of element fluorine to the sum of the weights of element nitrogen, element sulfur, and element phosphorus is 0.68:1. A separator with a weight of 1.5 g is soaked in a first solution with a volume of 5 mL at 85°C for 2 h. The increment of the air permeability value of the separator is 36 sec / 100 cc, and the first solution in which the separator is soaked is a soaking solution. In the soaking solution, the sum of the weight ratios of element nitrogen, element sulfur, and element phosphorus is 2530 ppm.

[0094] (5) Preparation of a lithium ion battery

[0095] The positive electrode sheet, the separator, and the negative electrode sheet prepared above are wound to prepare a bare battery cell. Subsequently, the bare battery cell is placed in an aluminum plastic film, and the electrolyte prepared above is injected into the dried bare battery cell. After vacuum packaging, standing at room temperature, and high-temperature formation, a lithium ion battery is obtained. The coating layer of the separator corresponds to the positive active layer, and the battery satisfies V1 / D1 = 0.05 / 0.14 = 0.4.

[0096] Example 2 group

[0097] This group of examples is used to illustrate the influence when the composition of the first particles is changed.

[0098] Example 2-1

[0099] This example was performed in the same manner as in Example 1, except that the component of the first particles was uracil, the sum of the number of carbon-carbon double bonds, phosphorus-oxygen double bonds, carbon-nitrogen double bonds, carbon-sulfur double bonds, and carbon-oxygen double bonds in the unit structure of the organic compound was 3, the ratio of the weight of elemental fluorine to the sum of the weights of elemental nitrogen, elemental sulfur, and elemental phosphorus on the surface of the coating layer on the side away from the base material layer was 0.41:1, the weight of the separator was 1.5 g, the volume of the first solution was 5 mL, the immersion time was 2 h, the increment of the air permeability value of the separator was 44 sec / 100 cc in an environment at 85°C, and the first solution in which the separator was immersed was the immersion solution, and the sum of the weight fractions of elemental nitrogen, elemental sulfur, and elemental phosphorus in the immersion solution was 8432 ppm.

[0100] Example 2-2

[0101] This example was performed in the same manner as in Example 1, except that the component of the first particles was 3-methyl-1-phenyl-2-phospholene 1-oxide, the sum of the number of carbon-carbon double bonds, phosphorus-oxygen double bonds, carbon-nitrogen double bonds, carbon-sulfur double bonds, and carbon-oxygen double bonds in the unit structure of the organic compound was 5, the ratio of the weight of elemental fluorine to the sum of the weights of elemental nitrogen, elemental sulfur, and elemental phosphorus on the surface of the coating layer on the side away from the base material layer was 0.27:1, the weight of the separator was 1.5 g, the volume of the first solution was 5 mL, the immersion time was 2 h, the increment of the air permeability value of the separator was 39 sec / 100 cc in an environment at 85°C, and the first solution in which the separator was immersed was the immersion solution, and the sum of the weight fractions of elemental nitrogen, elemental sulfur, and elemental phosphorus in the immersion solution was 1955 ppm.

[0102] Example 2-3

[0103] This example was performed in the same manner as in Example 1, except that the component of the first particles was melamine trithiocyanate, the sum of the number of carbon-carbon double bonds, phosphorus-oxygen double bonds, carbon-nitrogen double bonds, carbon-sulfur double bonds, and carbon-oxygen double bonds in the unit structure of the organic compound was 3, the ratio of the weight of elemental fluorine to the sum of the weights of elemental nitrogen, elemental sulfur, and elemental phosphorus on the surface of the coating layer on the side away from the base material layer was 1.2:1, the weight of the separator was 1.5 g, the volume of the first solution was 5 mL, the immersion time was 2 h, the increment of the air permeability value of the separator was 52 sec / 100 cc in an environment at 85°C, and the first solution in which the separator was immersed was the immersion solution, and the sum of the weight fractions of elemental nitrogen, elemental sulfur, and elemental phosphorus in the immersion solution was 3558 ppm.

[0104] Example 2-4

[0105] This embodiment is carried out with reference to Example 1, except that the component of the first particle is 2,4-dimercapto-5,6-diaminopyrimidine, and in the unit structure of the organic compound, the sum of the number of carbon-carbon double bonds, phosphorus-oxygen double bonds, carbon-nitrogen double bonds, carbon-sulfur double bonds, and carbon-oxygen double bonds is 3. On the surface of the coating away from the substrate layer, the ratio of the weight of elemental fluorine to the sum of the weights of elemental nitrogen, elemental sulfur, and elemental phosphorus is 1.06:1. In an environment of 85°C, a membrane weighing 1.5 g is immersed in a first solution with a volume of 5 mL for 2 h. The permeability value increase of the membrane is 61 sec / 100 cc, and the first solution soaked with the membrane is a soaking solution. In the soaking solution, the sum of the weight proportions of elemental nitrogen, elemental sulfur, and elemental phosphorus is 3648 ppm.

[0106] Example 3 group

[0107] This set of examples is used to illustrate the effects produced when the median particle size Dv50 of the first particles and / or the specific surface area of ​​the first particles are changed.

[0108] This embodiment group was carried out with reference to the embodiment 1, except that the median particle size Dv50 of the first particles and / or the specific surface area of ​​the first particles were changed, as shown in Table 1 for details.

[0109] Table 1

[0110]

[0111] Example 4 Group

[0112] This set of embodiments is used to illustrate the impact when the proportion of the orthographic projection area of ​​the through hole on the substrate layer and / or the first coating layer in the diaphragm surface area changes in the area of ​​the second coating layer of 100 μm×100 μm.

[0113] Example 4-1

[0114] This embodiment is carried out with reference to embodiment 1, except that, in the area of ​​100 μm×100 μm of the second coating, the orthographic projection area of ​​the through hole on the substrate layer and / or the first coating accounts for 10.6% of the surface area of ​​the diaphragm, and on the surface of the coating away from the substrate layer, the ratio of the weight of elemental fluorine to the sum of the weights of elemental nitrogen, elemental sulfur and elemental phosphorus is 2.85:1. In an environment of 85°C, a diaphragm weighing 1.5 g is immersed in a first solution with a volume of 5 mL for 2 h, and the permeability value increase of the diaphragm is 396 sec / 100 cc. The first solution soaked with the diaphragm is an immersion solution, and the sum of the weights of elemental nitrogen, elemental sulfur and elemental phosphorus in the immersion solution is 325 ppm.

[0115] Example 4-2

[0116] The embodiment is implemented with reference to Embodiment 1, except that the ratio of the area of the orthogonal projection of the through hole on the substrate layer and / or the first coating layer to the surface area of the separator is 79.3% in the area of 100 μm x 100 μm of the second coating layer, the ratio of the weight of element fluorine to the sum of the weights of element nitrogen, element sulfur and element phosphorus is 0.58:1 on the surface of the coating layer away from the substrate layer, the increment of the air permeability value of the separator is 39 sec / 100cc after the separator with a weight of 1.5 g is soaked in the first solution with a volume of 5 mL for 2 h in an environment at 85°C, and the first solution soaked by the separator is the soaking solution, and the sum of the weight ratios of element nitrogen, element sulfur and element phosphorus is 8546 ppm in the soaking solution.

[0117] Embodiment 4-3

[0118] The embodiment is implemented with reference to Embodiment 1, except that the ratio of the area of the orthogonal projection of the through hole on the substrate layer and / or the first coating layer to the surface area of the separator is 79.3% in the area of 100 μm x 100 μm of the second coating layer, the ratio of the weight of element fluorine to the sum of the weights of element nitrogen, element sulfur and element phosphorus is 0.58:1 on the surface of the coating layer away from the substrate layer, the increment of the air permeability value of the separator is 39 sec / 100cc after the separator with a weight of 1.5 g is soaked in the first solution with a volume of 5 mL for 2 h in an environment at 85°C, and the first solution soaked by the separator is the soaking solution, and the sum of the weight ratios of element nitrogen, element sulfur and element phosphorus is 8546 ppm in the soaking solution.

[0119] Embodiment 4-4

[0120] The embodiment is implemented with reference to Embodiment 1, except that the ratio of the area of the orthogonal projection of the through hole on the substrate layer and / or the first coating layer to the surface area of the separator is 79.3% in the area of 100 μm x 100 μm of the second coating layer, the ratio of the weight of element fluorine to the sum of the weights of element nitrogen, element sulfur and element phosphorus is 0.58:1 on the surface of the coating layer away from the substrate layer, the increment of the air permeability value of the separator is 39 sec / 100cc after the separator with a weight of 1.5 g is soaked in the first solution with a volume of 5 mL for 2 h in an environment at 85°C, and the first solution soaked by the separator is the soaking solution, and the sum of the weight ratios of element nitrogen, element sulfur and element phosphorus is 8546 ppm in the soaking solution.

[0121] Embodiment 5 group

[0122] This group of embodiments is used to illustrate the influence when the ratio of the thickness of the first coating layer to the thickness of the second coating layer changes.

[0123] This group of examples was performed with reference to Example 1, except that the ratio of the thickness of the first coating layer to the thickness of the second coating layer was changed by changing the thickness of the first coating layer and / or the thickness of the second coating layer, as shown in Table 2.

[0124] Table 2

[0125]

[0126] " " indicates the same as Example 1

[0127] Example 6 group

[0128] This group of examples was performed to show the effect when V1 / D1 is changed.

[0129] This group of examples was performed with reference to Example 1, except that V1 / D1 was changed by changing the particle size Dv10 (D1) of the first particles and / or the average volume (V1) of the positive electrode sheet recesses, as shown in Table 3.

[0130] Table 3

[0131]

[0132] Example 7

[0133] This example was performed with reference to Example 1, except that the weight ratio of the first particles in the first coating layer was 98%, the thickness of the first coating layer was 3 μm, the thickness of the second coating layer was 0.5 μm, the ratio of the thickness of the first coating layer to the thickness of the second coating layer was 6, the ratio of the weight of elemental fluorine to the sum of the weights of elemental nitrogen, elemental sulfur, and elemental phosphorus on the surface of the coating layer away from the base material layer side was 0.15:1, a separator having a weight of 1.5 g was immersed in a first solution having a volume of 5 mL at 85°C for 2 h, the increase in the air permeability value of the separator was 12 sec / 100 cc, and the first solution in which the separator was immersed was an immersion solution, and the sum of the weight ratios of elemental nitrogen, elemental sulfur, and elemental phosphorus in the immersion solution was 18445 ppm.

[0134] Example 8

[0135] The present example is performed according to example 1, except that the weight percentage of the first particles in the first coating layer is 90.2%, the percentage of the area of the orthogonal projection of the through holes on the substrate layer and / or the first coating layer in the surface area of the separator is 10.1% in an area of 100 μm x 100 μm of the second coating layer, the ratio of the weight of the element fluorine to the sum of the weights of the element nitrogen, the element sulfur and the element phosphorus on the surface of the coating layer away from the substrate layer is 2.2:1, the weight of the separator is 1.5 g, the volume of the first solution is 5 mL, the soaking time is 2 h in an environment of 85°C, the increment of the air permeability value of the separator is 410 sec / 100cc, and the first solution soaked by the separator is the soaking solution, and the sum of the weight percentages of the element nitrogen, the element sulfur and the element phosphorus in the soaking solution is 653 ppm.

[0136] Example 9

[0137] The present example is performed according to example 1, except that the weight percentage of the first particles in the first coating layer is 98%, the percentage of the area of the orthogonal projection of the through holes on the substrate layer and / or the first coating layer in the surface area of the separator is 89.5% in an area of 100 μm x 100 μm of the second coating layer, the ratio of the weight of the element fluorine to the sum of the weights of the element nitrogen, the element sulfur and the element phosphorus on the surface of the coating layer away from the substrate layer is 0.12:1, the weight of the separator is 1.5 g, the volume of the first solution is 5 mL, the soaking time is 2 h in an environment of 85°C, the increment of the air permeability value of the separator is 27 sec / 100cc, and the first solution soaked by the separator is the soaking solution, and the sum of the weight percentages of the element nitrogen, the element sulfur and the element phosphorus in the soaking solution is 23109 ppm.

[0138] Comparative Example 1

[0139] The present example group is performed according to example 1, except that the composition of the first particles is alumina, the weight of the separator is 1.5 g, the volume of the first solution is 5 mL, the soaking time is 2 h in an environment of 85°C, the increment of the air permeability value of the separator is 135 sec / 100cc, and the first solution soaked by the separator is the soaking solution, and the sum of the weight percentages of the element nitrogen, the element sulfur and the element phosphorus in the soaking solution is 0 ppm.

[0140] Comparative Example 2

[0141] The present example group is performed according to example 1, except that the surface of the second coating layer does not include through holes, the weight of the separator is 1.5 g, the volume of the first solution is 5 mL, the soaking time is 2 h in an environment of 85°C, the increment of the air permeability value of the separator is 532 sec / 100cc, and the first solution soaked by the separator is the soaking solution, and the sum of the weight percentages of the element nitrogen, the element sulfur and the element phosphorus in the soaking solution is 105 ppm.

[0142] Comparative Example 3

[0143] This example group was conducted in reference to Example 1, except that the ratio of the area of the orthogonal projection of the through holes on the substrate layer and / or the first coating layer in the surface area of the separator to the surface area of the second coating layer was 94.7%, and the ratio of the weight of fluorine to the sum of the weights of nitrogen, sulfur, and phosphorus on the surface of the coating layer away from the substrate layer was 0.07:1. The increment of the air permeability value of the separator was 17 sec / 100cc when the weight of the separator was 1.5 g and the volume of the first solution was 5 mL, and the first solution in which the separator was immersed was the immersion solution. The sum of the weight ratios of nitrogen, sulfur, and phosphorus in the immersion solution was 25300 ppm.

[0144] Comparative Example 4

[0145] This example group was conducted in reference to Example 1, except that the ratio of the area of the orthogonal projection of the through holes on the substrate layer and / or the first coating layer in the surface area of the separator to the surface area of the second coating layer was 94.7%, and the ratio of the weight of fluorine to the sum of the weights of nitrogen, sulfur, and phosphorus on the surface of the coating layer away from the substrate layer was 0.07:1. The increment of the air permeability value of the separator was 17 sec / 100cc when the weight of the separator was 1.5 g and the volume of the first solution was 5 mL, and the first solution in which the separator was immersed was the immersion solution. The sum of the weight ratios of nitrogen, sulfur, and phosphorus in the immersion solution was 25300 ppm.

[0146] Comparative Example 5

[0147] This example group was conducted in reference to Example 1, except that the second coating layer was a porous structure formed by a continuous phase of polyacrylonitrile (without fluorine), and the ratio of the weight of fluorine to the sum of the weights of nitrogen, sulfur, and phosphorus on the surface of the coating layer away from the substrate layer was 0. The increment of the air permeability value of the separator was 118 sec / 100cc when the weight of the separator was 1.5 g and the volume of the first solution was 5 mL, and the first solution in which the separator was immersed was the immersion solution. The sum of the weight ratios of nitrogen, sulfur, and phosphorus in the immersion solution was 3520 ppm.

[0148] Comparative Example 6

[0149] The present example group is carried out with reference to Example 1, except that the coating layer on one side surface of the substrate layer only includes the first coating layer, the third coating layer is located on the other side surface of the substrate layer, the ratio of the weight of element fluorine to the sum of the weights of element nitrogen, element sulfur and element phosphorus on the surface of the coating layer away from the substrate layer is 0, the weight of the separator is 1.5 g, the volume of the first solution is 5 mL, and the soaking time is 2 h at 85°C, the increment of the air permeability value of the separator is 85 sec / 100 cc, and the first solution in which the separator is soaked is the soaking solution, and the sum of the weight percentages of element nitrogen, element sulfur and element phosphorus in the soaking solution is 35300 ppm.

[0150] Test Example

[0151] The batteries prepared in the examples and comparative examples were subjected to the following performance tests, and the test results are shown in Table 4:

[0152] (1) Cycle capacity retention rate at room temperature / % (cycled for 600 cycles at an environment of 25°C±2°C):

[0153] At an environment of 25°C±2°C, the battery was charged at 1C constant current to the upper limit voltage of 4.53V, then continued to be charged at constant voltage to 0.05C, and was static for 5 min, then discharged at 0.7C constant current to 3V, and was static for 5 min, and the initial discharge capacity was recorded as C0. The cycle mode was as follows: charged at 1C constant current to the upper limit voltage of 4.53V, then continued to be charged at constant voltage to 0.05C, and was static for 5 min, then discharged at 0.7C constant current to 3V. After 600 cycles, the discharge capacity was recorded as C1. The cycle capacity retention rate at room temperature was (C1 / C0)×100%.

[0154] (2) High-temperature intermittent cycle capacity retention rate / % (intermittently cycled for 91 days at an environment of 45°C±2°C):

[0155] Initial capacity Q1 test: the battery was static for 10 minutes at an environment of 25°C±3°C; then discharged at 0.2C constant current to 3V cut-off voltage, and was static for 10 minutes again; then charged at 0.8C constant current to full state, and was static for 10 minutes after constant voltage charging to 0.05C cut-off current; and discharged at 0.2C constant current to 3V again, and the discharge capacity at this time was recorded as the initial capacity Q1;

[0156] Intermittent charge and discharge at 45°C±2°C: the battery was static for 10 minutes at an environment of 45°C±2°C; then discharged at 0.5C constant current to 3V cut-off voltage; and was static for 10 minutes; then charged at 0.7C constant current to full state; and the total test time of the above static, discharge, static and charge steps was controlled to be 24 hours;

[0157] Final capacity Q2 test: the aforementioned intermittent charge and discharge step at 45°C±2°C is taken as one cycle, and a total of 91 cycles are performed; after the end of the cycles, the battery is moved to an environment of 25°C±5°C, and after the sample returns to room temperature, the aforementioned initial capacity Q1 test step is repeated, and the obtained discharge capacity is the final capacity Q2, and (Q2 / Q1) x 100% is the final cycle capacity retention rate.

[0158] (2) High-temperature storage recovery capacity retention rate / % (stored for 6 hours in an environment of 85°C±2°C):

[0159] Initial capacity Q3 test: the battery is placed in an environment of 25°C±2°C for 10 minutes; then discharged at 0.5C to the lower limit voltage 3V, and then left for 10 minutes; then charged at 0.7C to the full state of charge, and then converted to constant voltage charging until the current is 0.05C cutoff, and then left for 10 minutes; then discharged at 0.5C to the lower limit voltage 3V, and the discharge capacity at this time is recorded as the initial capacity Q3;

[0160] Test storage state: after the initial capacity test is completed, the battery is left for 10 minutes, and then charged at 0.7C to the full state of charge, and then converted to constant voltage charging until the current is 0.05C cutoff; the full battery is left to stand for 2 hours in an environment of 25°C±2°C;

[0161] Recovery capacity Q4 test: the battery is placed in an oven at 85°C±2°C for 6 hours, and after the storage is completed, the sample is taken out and left to stand for 2 hours in an environment of 25°C±2°C to allow the battery to return to room temperature; after the sample returns to room temperature, the aforementioned initial capacity Q3 test step is repeated, and the obtained discharge capacity is the recovery capacity Q4, and (Q4 / Q3) x 100% is the recovery capacity retention rate.

[0162] Table 4

[0163]

[0164]

[0165] As can be seen from the comparison of the test results of the comparative examples and the examples in Table 4, the room temperature cycle capacity retention rate, the high-temperature intermittent cycle capacity retention rate, and the high-temperature storage recovery capacity retention rate of the battery of the examples are all significantly improved, which can indicate that by providing the first particles containing electron-deficient groups on the separator, and simultaneously controlling the coverage rate of the through holes that facilitate the diffusion of the organic matter containing electron-deficient groups, the high-temperature resistance of the CEI film is effectively improved, the damage of the CEI film is reduced or even avoided, so that the room temperature cycle capacity retention rate, the high-temperature intermittent cycle capacity retention rate, and the recovery capacity retention rate after high-temperature storage of the battery are significantly improved.

[0166] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including that each technical feature is combined in any other suitable manner. These simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. A battery, characterized in that: The battery includes a positive electrode sheet and a separator, wherein the positive electrode sheet includes a positive electrode current collector and a positive electrode active layer located on one side or both sides of the positive electrode current collector, the separator includes a substrate layer and a coating located on one side or both sides of the substrate layer, the coating corresponding to the positive electrode active layer, the coating including a first coating and a second coating, the first coating located on the surface of the substrate layer, the second coating located on the surface of the first coating, the first coating including first particles, the first particles are composed of organic compounds, the unit molecular structure of the organic compound includes one or more of a carbon-carbon double bond, a phosphorus-oxygen double bond, a carbon-nitrogen double bond, a carbon-sulfur double bond and a carbon-oxygen double bond; the second coating is a porous structure formed by a fluorine-containing polymer as a continuous phase, the surface of the second coating includes through holes, and an area of ​​100 μm×100 μm on the surface of the second coating In the embodiment, the orthographic projection area of ​​the through hole on the substrate layer and / or the first coating accounts for 10%-90% of the surface area of ​​the diaphragm, wherein a scanning electron microscope is used to obtain a microscopic image of the diaphragm surface, and a 100 μm×100 μm area on the surface of the second coating is randomly selected as the analysis area, and the analysis area is divided into 400×400 squares, with the number of squares Y=400×400. If the coverage area of ​​the through hole in the square exceeds half of the square area, it means that the square is occupied by the through hole, and the total number of squares occupied by the through hole is recorded as X, and the area ratio is (X / Y)×100%. The operation is repeated 5 times to calculate the average value to obtain the ratio of the orthographic projection area of ​​the through hole on the substrate layer and / or the first coating in the 100 μm×100 μm area of ​​the surface of the second coating to the surface area of ​​the diaphragm.

2. The battery according to claim 1, wherein The coating comprises the first coating and the second coating, and on a surface of the coating away from the substrate layer, a ratio of the weight of elemental fluorine to the sum of the weights of elemental nitrogen, elemental sulfur, and elemental phosphorus is (0.25-3):1; And / or, in the unit structure of the organic compound, the sum of the numbers of carbon-carbon double bonds, phosphorus-oxygen double bonds, carbon-nitrogen double bonds, carbon-sulfur double bonds and carbon-oxygen double bonds is 3-12.

3. The battery according to claim 1, wherein The organic compounds include 1,3,5-triazine-2,4,6-triamine, melamine polyphosphate, melamine hydrobromide, melamine polyphosphate, symmetrical triaminotriazine, 2-(4-bromophenyl)-4,6-dimethyl-1,3,5-triazine, 2,4-diamino-6-dimethylamino-1,3,5-triazine, cyanuric chloride, melamine thiocyanate, melamine cyanurate, 2-amino-4,6-methoxy-1,3,5-triazine, 1-(4,6-diamino-1,3,5-triazin-2-yl)guanidine, uracil, cytosine, 5-azacytosine , indole-3-propionic acid, N4-methylcytosine, 1-phenyl-3-methyl-5-pyrazolone, formaldehyde polymelamine hydrochloride, 2,4,6-triphenyl-1,3,5-triazine, 2-quinolinesulfonic acid and 2-quinolinesulfonate, 2,4,6-tris(2-pyridyl)triazine, tris(tribromophenoxy)triazine, dithiourea, 2,4-dimercapto-5,6-diaminopyrimidine, 4,6-dimethyl-2-mercaptopyrimidine, 1,3,4-thiadiazole-2-thione salt, coumarin-3-sulfonate, 3-methyl-1-phenyl-2-phosphacyclopentene 1-oxide; And / or, the fluorine-containing polymer includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.

4. The battery according to claim 1, wherein The ratio of the thickness of the first coating layer to the thickness of the second coating layer is 0.4-3; and / or, the thickness of the first coating layer is 0.2 μm-5 μm; and / or, the thickness of the second coating layer is 0.5 μm-5 μm; and / or, the weight proportion of the first particles in the first coating layer is 90%-99%; And / or, the weight proportion of the fluorine-containing polymer in the second coating layer is 70%-100%; and / or, the median particle size Dv50 of the first particles is 0.05 μm-5 μm; And / or, the specific surface area of ​​the first particles is 4m 2 / g-35m 2 / g.

5. The battery according to claim 1, wherein One side surface of the substrate layer includes the coating layer, and the other side surface of the substrate layer includes a third coating layer; and / or, the porosity of the substrate layer is 25%-70%; and / or, the thickness of the substrate layer is 2 μm-10 μm; And / or, the components of the substrate layer include one or more of polyolefin, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinyl chloride, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyethylene terephthalate, polybutylene terephthalate, poly(p-phenylene terephthalamide), and poly(m-phenylene isophthalamide).

6. The battery according to any one of claims 1 to 5, wherein In an environment of 85°C, the diaphragm weighing 1.5g is soaked in a first solution with a volume of 5mL for 2h, the air permeability value increment of the diaphragm is 20 sec / 100cc-400sec / 100cc, and the first solution soaked with the diaphragm is a soaking solution, in which the sum of the weight proportions of elemental nitrogen, elemental sulfur and elemental phosphorus is 500ppm-20000ppm, wherein the first solution is composed of dimethyl carbonate, ethylene carbonate and ethyl methyl carbonate, and the weight ratio of the dimethyl carbonate, the ethylene carbonate and the ethyl methyl carbonate is 1:1:

1.

7. The battery according to claim 1, wherein In the thickness direction of the positive electrode sheet, the positive electrode sheet includes a first surface and a second surface, the first surface corresponds to the coating, the first surface includes a plurality of pits, and the battery satisfies the following relationship: 0.005≤V1 / D1≤10, wherein D1 is the Dv10 of the first particle, in μm, and V1 is the average volume of the pits, in mm 3 .

8. The battery according to claim 7, wherein: The battery satisfies the following relationship: 0.05≤V1 / D1≤5, and / or, the average volume V1 of the pits is 0.001 mm 3 -0.15mm 3 ; and / or, the Dv10 of the first particles is 0.01 μm-0.5 μm; And / or, at least a portion of the first surface is recessed toward the second surface to form a plurality of pits, and a plurality of protrusions are correspondingly provided on the second surface.

9. The battery according to claim 7, wherein The average depth of the pits is 2 μm-30 μm; and / or, the average spacing between adjacent pits is 100 μm-500 μm; And / or, the shape of the orthographic projection of the pit on the first surface includes one or more of a circle, an ellipse, a diamond, a rectangle, a square and an island.

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