Separator, and electrochemical device and electronic device including same

Abstract

The present invention discloses a separator and an electrochemical device and an electronic device comprising the same, the separator comprises a porous base membrane and a functional coating layer arranged on at least one surface of the porous base membrane, the functional coating layer comprises a fibrous polymer and columnar inorganic particles, the average length of the fibrous polymer is Lnm, and the columnar inorganic particles are arranged on at least one surface of the porous base membrane. The average length of the columnar inorganic particles is Dnm, D and L meet the condition that D / L is larger than or equal to 0.05 and smaller than or equal to 1, and D and T meet the condition that D / T is larger than or equal to 2 and smaller than or equal to 10. According to the diaphragm disclosed by the invention, the functional coating is arranged on the surface of the porous base membrane, the functional coating comprises the fibrous polymer and the columnar inorganic particles, and organic components and inorganic components are matched for use, so that the coating has better affinity to electrolyte, and the wettability of the diaphragm is better. The fibrous polymer is used as a key component and has the effects of providing electrolyte absorption and retention and forming a flexible interface buffer layer with the electrode to reduce interface impedance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of energy storage, more particularly, to a separator, and an electrochemical device and an electronic device comprising the same. BACKGROUND

[0002] Lithium ion batteries play a key role in the field of electric vehicles, grid-level energy storage and consumer electronics due to their high energy density, small self-discharge rate and long cycle life. With the continuous development of lithium ion batteries towards high energy density, high safety and fast charging, the performance bottleneck of traditional polyolefin separators has become increasingly prominent, especially in terms of thermal safety and fast charging performance. The low melting point of the material easily leads to high-temperature shrinkage and thermal runaway risk, while the strong hydrophobicity and poor electrolyte wettability of the material not only increase the ion transfer impedance and limit the fast charging capacity, but also cause uneven wettability and local polarization, indirectly exacerbating the thermal safety hazard. Therefore, the development of new separators with high thermal stability and excellent electrolyte affinity has become a key to promoting advanced lithium ion battery technology. SUMMARY

[0003] The present application aims to at least solve one of the above technical problems in the prior art. To this end, the present application provides a separator, which has a higher thermal stability and significantly improves the affinity of the separator to the electrolyte by constructing an organic-inorganic composite coating on the surface of the base film, so that the wettability is effectively improved, the ion impedance is significantly reduced, and the liquid retention performance of the separator is also significantly improved.

[0004] The present application also provides a method for preparing a separator.

[0005] The present application also provides an electrochemical device.

[0006] The present application also provides an electronic device.

[0007] The first aspect of the present application provides a separator, comprising a porous base film and a functional coating provided on at least one side of the porous base film, the functional coating comprising fibrous polymers and columnar inorganic particles, the average length of the fibrous polymers being Lnm, the average length of the columnar inorganic particles being Dnm, and the average diameter of the columnar inorganic particles being Tnm, wherein D and L satisfy: 0.05≤D / L≤1, and D and T satisfy: 2≤D / T≤10.

[0008] The technical solution of the present application for a separator has at least the following beneficial effects:

[0009] The diaphragm of the present application is provided with a functional coating on the surface of the porous base film, which includes fibrous polymer and columnar inorganic particles. By using the fibrous polymer and columnar inorganic particles together, the coating has better affinity to the electrolyte while having higher thermal stability, higher ionic conductivity, and better wettability of the diaphragm. The fibrous polymer coating can improve the wettability through physical capillary action due to its high specific surface area and multi-level porosity, solving the wetting problem of traditional diaphragms caused by hydrophobicity or uneven porosity. The fibrous polymer as a key component can provide electrolyte absorption and liquid retention and form a flexible interface buffer layer with the electrode to reduce interface impedance.

[0010] When 2≤D / T≤10, in this range of aspect ratio, the columnar inorganic particles are more easily arranged vertically under the assistance of electric field or shear force, forming low-curved ion channels to improve ionic conductivity.

[0011] According to some embodiments of the present application, D and L satisfy: 0.1≤D / L≤0.8.

[0012] According to some embodiments of the present application, D and L satisfy: 0.4≤D / L≤0.8.

[0013] According to some embodiments of the present application, D and T satisfy: 2≤D / T≤8.

[0014] According to some embodiments of the present application, the average length value L of the fibrous polymer satisfies: 50≤L≤5000.

[0015] According to some embodiments of the present application, the average length value L of the fibrous polymer satisfies: 100≤L≤4000.

[0016] According to some embodiments of the present application, the average length value L of the fibrous polymer satisfies: 500≤L≤3000.

[0017] According to some embodiments of the present application, the average length value L of the fibrous polymer satisfies: 800≤L≤2000.

[0018] According to some embodiments of the present application, the average diameter of the fibrous polymer is anm.

[0019] According to some embodiments of the present application, the average diameter value a of the fibrous polymer satisfies: 1≤a≤300. The fibrous polymer has a high aspect ratio, which is beneficial for interlacing and lapping on the surface layer of the coating to form a three-dimensional horizontal cross-linking network.

[0020] According to some embodiments of the present application, the average diameter value T of the columnar inorganic particles satisfies: 20≤T≤500.

[0021] According to some embodiments of the present application, the average diameter value T of the columnar inorganic particles satisfies: 50≤T≤300.

[0022] According to some embodiments of the present application, the average length value D of the columnar inorganic particles satisfies: 200≤D≤3000.

[0023] According to some embodiments of the present application, the average length value D of the columnar inorganic particles satisfies: 300≤D≤2000.

[0024] The porous base film is the core support structure of the separator, and its material and pore characteristics affect the mechanical strength, thermal stability, electrolyte wettability and ion transport performance of the separator.

[0025] According to some embodiments of the present application, the porous base film can be composed of organic polymers, including polyolefins, polyesters, polyacetals, polyamides, polycarbonates, polyimides, polyether ether ketones, polyether sulfones, polyphenylene ethers, polyphenylene sulfides, polyacrylonitriles, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) copolymer, polyoxymethylene, polyvinylpyrrolidone or a combination thereof.

[0026] According to some embodiments of the present application, the polyolefins include at least one of polyethylene (PE), polypropylene (PP), polypropylene / polyethylene (PP-PE) copolymer, polypropylene / polyethylene / polypropylene (PP / PE / PP) copolymer, and polyethylene / polypropylene / polyethylene (PE / PP / PE) copolymer.

[0027] According to some embodiments of the present application, the weight percentage of the fibrous polymer is 5-50% and the weight percentage of the columnar inorganic particles is 60-90% based on the total weight of the functional coating. When the components of the functional coating are within this range, the bottom layer is mainly composed of columnar inorganic particles during the coating process of the separator, ensuring the thermal stability of the base film; the top layer is mainly composed of fibrous polymers, forming a porous network, reducing the electrolyte contact angle, and at the same time enhancing the puncture resistance and flexibility.

[0028] According to some embodiments of the present application, the weight percentage of the fibrous polymer is 10-40% and the weight percentage of the columnar inorganic particles is 70-80% based on the total weight of the functional coating. When the mass fractions of the fibrous polymer and the columnar inorganic particles, which are components of the functional coating, satisfy the above conditions, the liquid absorption rate of the separator is better.

[0029] According to some embodiments of the present application, the functional coating has a gradient structure. In this structure, the columnar inorganic particles are rod-like particles, which are arranged vertically (perpendicular to the surface of the base membrane) at a high density on the side close to the porous base membrane to form a heat-resistant support layer that effectively resists penetration, and are arranged horizontally (parallel to the surface of the base membrane) on the side close to the electrolyte to form porous wetting channels that facilitate the absorption of impact energy. This gradient structure design takes into account both high heat resistance and high wettability.

[0030] According to some embodiments of the present application, the thickness of the functional coating is h μm, and the value of the thickness h of the functional coating satisfies: h > (a + 0.7D) / 1000.

[0031] According to some embodiments of the present application, the fibrous polymer can be a water-soluble polymer or an oil-soluble polymer, and can be a homopolymer or a copolymer.

[0032] According to some embodiments of the present application, the fibrous polymer is at least one of a halogenated polymer, a polyester polymer, a polycarboxylic acid polymer, a polyurethane polymer, a polyamide polymer, a polyimide polymer, a vinyl polymer, a polyether polymer, an engineering plastic polymer, a conductive polymer, cellulose and its derivatives, or a rubber / elastomer.

[0033] According to some embodiments of the present application, the fibrous polymer is at least one of polyvinylidene fluoride (PVDF), a homopolymer or a copolymer formed by vinylidene fluoride and another copolymerizable monomer (such as one or more of tetrafluoroethylene, hexafluoropropylene, trifluoroethylene, trichloroethylene, fluoroethylene), polytetrafluoroethylene, fluorinated ethylene propylene copolymer, perfluorosulfonic acid resin, polycarboxylate, polycaprolactone, polyacrylate, polyurethane, polyamide, polyimide, polyacrylonitrile, polyethylene oxide, polyacrylic acid, polymethacrylic acid, polymethacrylate, polyvinyl alcohol, polyvinyl acetate, polyacrylamide, polyphenylene ether, polyvinyl compound, polystyrene, polyvinylpyrrolidone, acrylonitrile-styrene-butadiene copolymer, polyphenylene sulfide, polyether ether ketone, polyaramide, polypyrrole, polyaniline, polythiophene, polyethylene glycol, polylactic acid, cellulose (which can be cellulose nanofiber), cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, carboxymethyl cellulose, cyanoethyl cellulose, nitrile rubber (NBR), styrene-butadiene rubber (SBR), and latex.

[0034] According to some embodiments of the present application, the polyvinylidene fluoride-based resin comprises at least one of a homopolymer of polyvinylidene fluoride (i.e., polyvinylidene fluoride), a copolymer formed from polyvinylidene fluoride and another copolymerizable monomer (such as at least one of tetrafluoroethylene, hexafluoropropylene, trifluoroethylene, trichloroethylene, fluoroethylene).

[0035] According to some embodiments of the present application, the columnar inorganic particles comprise at least one of silica particles, barium dititanate particles, zirconia particles, alumina particles, barium metatitanate particles, barium sulfate particles, tin oxide particles, titanium nitride particles, aluminum nitride particles, silicon oxide particles, calcium oxide particles, magnesium oxide particles, magnesium hydroxide particles, zinc oxide particles, titanium dioxide particles, boehmite particles, hydrated alumina particles, and ceramic particles.

[0036] According to some embodiments of the present application, the angle between the columnar inorganic particles and the porous base film is > 45°.

[0037] A second aspect of the present application provides a method for preparing the separator of the first aspect of the present application, comprising the following steps:

[0038] S1: dispersing the fibrous polymer and the columnar inorganic particles in a solvent to obtain a slurry;

[0039] S2: after coating the slurry on the surface of the porous base film, pre-solidifying and drying to form the functional coating, thereby obtaining the separator.

[0040] The present application relates to a method for preparing a separator, and at least has the following beneficial effects:

[0041] The method for preparing the present application forms a uniform slurry by co-dispersing the fibrous polymer and the columnar inorganic particles in a solvent, constructs a structured coating on the porous base film, and then obtains a composite separator product after pre-solidification and drying. The process promotes the formation of a uniform mixture of the two phases through the co-dispersing process, eliminating the interfacial energy barrier; further, the pre-solidification process improves the bonding strength between the slurry and the base film, and the drying process forms a through-porous structure in the coating, improving the electrolyte infiltration effect.

[0042] According to some embodiments of the present application, the solvent comprises at least one of water, dimethylacetamide (DMAC), dichloroethane, dimethylformamide (DMF), trichloroethane, trichloromethane, ethyl acetate, sulfolane, dimethyl sulfoxide (DMSO), N-methyl pyrrolidone (NMP), chloroform, dichloromethane, and acetone.

[0043] According to some embodiments of the present application, the solvent can be a combination of a low-boiling point solvent and a high-boiling point solvent, which rapidly forms a concentration gradient on the surface of the coating, promoting the parallel spreading of the fibers on the electrolyte side.

[0044] According to some embodiments of the present application, the coating speed is 10 m / min to 20 m / min.

[0045] According to some embodiments of the present application, the shear rate during the coating process is 1000 s -1 to 1400 s -1 .

[0046] According to some embodiments of the present application, the coating method can be one or more of microgravure coating, extrusion coating, dip coating, spray coating, dot coating or wire bar coating. Preferably, microgravure coating or extrusion coating technique is used, by adjusting the coating speed and shear force direction, to facilitate the driving of the fibrous polymer to arrange horizontally along the plane direction of the base film.

[0047] According to some embodiments of the present application, the coating amount of the coating layer is 0.5 g / m 2 to 3.0 g / m 2 , preferably 1.0-2.5 g / m 2 .

[0048] A third aspect of the present application provides an electrochemical device comprising a positive electrode, a negative electrode, an electrolyte and the separator of the first aspect of the present application.

[0049] According to some embodiments of the present application, the electrochemical device is a lithium ion battery.

[0050] A fourth aspect of the present application provides an electronic device comprising the electrochemical device of the third aspect of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0051] The embodiments in the present application will not be limited to the drawings described below, and the drawings described below are only some embodiments in the present application. Those skilled in the art can obtain the drawings of other embodiments according to the content in the present application.

[0052] Figure 1 is a structural schematic diagram of the separator of the embodiments of the present application. DETAILED DESCRIPTION

[0053] General definitions

[0054] The term "porous base film" refers to a substrate having pores or voids inside. The material used as the component of the porous base film can be an organic material or an inorganic material, as long as the material is an electrically insulating material. Any porous base film having electrical insulation can be used herein.

[0055] The term "polymer" refers to a polymeric compound prepared by polymerizing monomers of the same or different type. The general term "polymer" includes "homopolymer", "copolymer", "terpolymer", and "interpolymer".

[0056] The term "fibrous polymer" refers to a high molecular weight material having a continuous filamentous morphology, with polymer molecular chains highly oriented along the axial direction in the solid state microstructure, forming a microfibrillar structure with crystalline and amorphous regions periodically alternating. The material typically exhibits a fiber unit with an aspect ratio (ratio of length to characteristic diameter) of 50:1 or more at a macroscopic scale, which can be prepared by processes such as spinning, phase separation, or self-assembly.

[0057] The term "functional coating" refers to one or more layers coated on one or both sides of a porous base film. The functional coating comprises a mixture of at least one organic binder and at least one inorganic filler. In addition to the organic binder and the inorganic filler, the protective porous layer can also include one or more additives. The functional coating can be a single layer, a double layer, or a multi-layer structure.

[0058] The term "average length of fibrous polymer" refers to the average value of the length of individual fibrous polymer (single fiber) constituting the functional coating in a statistical sample.

[0059] The term "average diameter of fibrous polymer" refers to the average value of the widest distance of the cross section of a single fibrous polymer constituting the functional coating in a statistical sample.

[0060] The term "average length of columnar inorganic particle" refers to the average value of the length of individual rod-shaped inorganic material constituting the functional coating in a statistical sample.

[0061] The term "average diameter of columnar inorganic particle" refers to the average value of the widest distance of the cross section of a rod-shaped inorganic material constituting the functional coating in a statistical sample.

[0062] In the following description, all numbers disclosed herein are approximate unless otherwise indicated. It is possible, however, that the numbers represent exact values.

[0063] The present application provides a separator for an electrochemical device, comprising a porous base film and a functional coating provided on at least one side of the porous base film, the functional coating comprising fibrous polymers and columnar inorganic particles, the average length of the fibrous polymers being Lnm, the average length of the columnar inorganic particles being Dnm, and the average diameter of the columnar inorganic particles being Tnm, wherein D and L satisfy: 0.05≤D / L≤1, and D and T satisfy: 2≤D / T≤10.

[0064] Exemplarily, the value of D / L can be 0.05, 0.07, 0.08, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1, or within a range between any two of the above values.

[0065] Exemplarily, the value of D / T can be 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5 or 10, or within a range between any two of the above values.

[0066] According to some embodiments of the present application, D and L satisfy: 0.1≤D / L≤0.8.

[0067] According to some embodiments of the present application, D and L satisfy: 0.4≤D / L≤0.8.

[0068] According to some embodiments of the present application, D and T satisfy: 2≤D / T≤8. Controlling within this aspect ratio range is conducive to realizing efficient directional arrangement of inorganic particles under the action of electric field or shear force, and forming regular structures perpendicular to the surface of the base film. Such ordered arrangement on the one hand builds an open pore network that is interconnected and communicated, significantly improving the lithium ion transmission efficiency and reducing the interface impedance; on the other hand, the close packing of particles forms a support skeleton with higher mechanical strength, effectively enhancing the anti- dendrite puncture ability of the separator and improving the thermal stability. This aspect ratio range balances the particle orientation efficiency and packing density, achieving the synergistic optimization of electrochemical performance and structural stability.

[0069] I. Separator

[0070] Porous base film

[0071] The porous base film is the core support structure of the separator, and its material and pore characteristics affect the mechanical strength, thermal stability, electrolyte wettability and ion transmission performance of the separator. According to some embodiments of the present application, the porous base film can be composed of organic polymers, including polyolefins, polyesters, polyacetals, polyamides, polycarbonates, polyimides, polyether ether ketones, polyether sulfones, polyphenylene ethers, polyphenylene sulfides, polyacrylonitriles, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTEE) and polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) copolymer, polyformaldehyde, polyvinylpyrrolidone or a combination thereof. However, all other known polymer fibers or many natural fibers can also be used.

[0072] According to some embodiments of the present application, the polyolefin comprises at least one of polyethylene (PE), polypropylene (PP), polypropylene / polyethylene (PP-PE) copolymer, polypropylene / polyethylene / polypropylene (PP / PE / PP) copolymer, and polyethylene / polypropylene / polyethylene (PE / PP / PE) copolymer.

[0073] According to some embodiments of the present application, the porous base film has a melting point of 130-160 °C. Illustratively, the porous base film can have a melting point of 130 °C, 131 °C, 132 °C, 133 °C, 134 °C, 135 °C, 136 °C, 137 °C, 138 °C, 139 °C, 140 °C, 141 °C, 142 °C, 143 °C, 144 °C, 145 °C, 146 °C, 147 °C, 148 °C, 149 °C, 150 °C, 151 °C, 152 °C, 153 °C, 154 °C, 155 °C, 156 °C, 157 °C, 158 °C, 159 °C, or 160 °C, or within a range between any two of the aforementioned values.

[0074] According to some embodiments of the present application, the porous base film has a thickness of 2-30 μιη. Illustratively, the porous base film can have a thickness of 2 μιη, 3 μιη, 4 μιη, 5 μιη, 6 μιη, 7 μιη, 8 μιη, 9 μιη, 10 μιη, 11 μιη, 12 μιη, 13 μιη, 14 μιη, 15 μιη, 16 μιη, 17 μιη, 18 μιη, 19 μιη, 20 μιη, 21 μιη, 22 μιη, 23 μιη, 24 μιη, 25 μιη, 26 μιη, 27 μιη, 28 μιη, 29 μιη, or 30 μιη, or within a range between any two of the aforementioned values.

[0075] According to some embodiments of the present application, the porous base film has a porosity of 20-60%. Illustratively, the porous base film can have a porosity of 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, or 60%, or within a range between any two of the aforementioned values.

[0076] According to some embodiments of the present application, the air permeability of the porous base film is 30 sec / 100cc-400 sec / 100cc. Illustratively, the air permeability of the porous base film is 30 sec / 100cc, 40 sec / 100cc, 50 sec / 100cc, 60 sec / 100cc, 70 sec / 100cc, 80 sec / 100cc, 90 sec / 100cc, 100 sec / 100cc, 110 sec / 100cc, 120 sec / 100cc, 130 sec / 100cc, 140 sec / 100cc, 150 sec / 100cc, 160 sec / 100cc, 170 sec / 100cc, 180 sec / 100cc, 190 sec / 100cc, 200 sec / 100cc, 210 sec / 100cc, 220 sec / 100cc, 230 sec / 100cc, 240 sec / 100cc, 250 sec / 100cc, 260 sec / 100cc, 270 sec / 100cc, 280 sec / 100cc, 290 sec / 100cc, 300 sec / 100cc, 310 sec / 100cc, 320 sec / 100cc, 330 sec / 100cc, 340 sec / 100cc, 350 sec / 100cc, 360 sec / 100cc, 370 sec / 100cc, 380 sec / 100cc, 390 sec / 100cc, or 400 sec / 100cc, or within a range between any two of the above values.

[0077] Functional coating

[0078] According to some embodiments of the present application, the functional coating layer is coated on at least one side of the porous base film, and the functional coating layer comprises a fibrous polymer and columnar inorganic particles.

[0079] Fibrous polymer

[0080] According to some embodiments of the present application, the fibrous polymer can be a water-soluble polymer or an oil-soluble polymer, and can be a homopolymer or a copolymer.

[0081] According to some embodiments of the present application, the fibrous polymer comprises at least one of a fluoropolymer, a polyester polymer, a polycarboxylic acid polymer, an acrylic acid polymer, a polyurethane polymer, a polyamide polymer, a polyimide polymer, a vinyl polymer, a polyether polymer, an engineering plastic polymer, a conductive polymer, cellulose and its derivatives, or a rubber / elastomer.

[0082] According to some embodiments of the present application, the material of the fibrous polymer comprises at least one of polyvinylidene fluoride (PVDF), a homopolymer or a copolymer formed from vinylidene fluoride and another copolymerizable monomer (such as one or more of tetrafluoroethylene, hexafluoropropylene, trifluoroethylene, trichloroethylene, fluoroethylene), polytetrafluoroethylene, fluorinated ethylene propylene copolymer, perfluorosulfonic acid resin, polycarboxylate, polycaprolactone, polyacrylate, polyurethane, polyamide, polyimide, polyacrylonitrile, polyethylene oxide, polyacrylic acid, polymethacrylic acid, polymethacrylate, polyvinyl alcohol, polyvinyl acetate, polyacrylamide, polyphenylene ether, polyvinyl compound, polystyrene, polyvinylpyrrolidone, acrylonitrile-styrene-diene copolymer, polyphenylene sulfide, polyether ether ketone, polyaramid, polypyrrole, polyaniline, polythiophene, polyethylene glycol, polylactic acid, cellulose (may be cellulose nanofiber), cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, carboxymethyl cellulose, cyanoethyl cellulose, nitrile rubber (NBR), styrene butadiene rubber (SBR), and latex.

[0083] According to some embodiments of the present application, the polyvinylidene fluoride-based resin comprises at least one of a homopolymer of vinylidene fluoride (i.e., polyvinylidene fluoride) and a copolymer formed from vinylidene fluoride and another copolymerizable monomer (such as one or more of tetrafluoroethylene, hexafluoropropylene, trifluoroethylene, trichloroethylene, fluoroethylene).

[0084] According to some embodiments of the present application, the material of the fibrous polymer comprises at least one of polytetrafluoroethylene, fluorinated ethylene propylene copolymer, perfluorosulfonic acid resin, polyphenylene sulfide, polyether ether ketone, polyaramid, cellulose nanofiber, polypyrrole, polyaniline, polythiophene, polyvinyl alcohol, polyethylene glycol, polylactic acid, polycaprolactone, and polystyrene.

[0085] According to some embodiments of the present application, the average diameter of the fibrous polymer of the present application is anm.

[0086] According to some embodiments of the present application, the average diameter of the fibrous polymer is a value a that satisfies: 1≤a≤300.

[0087] According to some embodiments of the present application, exemplarily, a is 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, 180, 185, 190, 195, 200, 205, 210, 215, 220, 225, 230, 235, 240, 245, 250, 255, 260, 265, 270, 275, 280, 285, 290, 295, or 300, or within a range between any two of the above values.

[0088] According to some embodiments of the present application, the average diameter of the fibrous polymer is a, and a satisfies 50≤a≤250.

[0089] According to some embodiments of the present application, the average diameter of the fibrous polymer is a, and a satisfies 60≤a≤220.

[0090] According to some embodiments of the present application, the thickness of the functional coating is h μm.

[0091] According to some embodiments of the present application, exemplarily, h is 1.5 μm, 1.450 μm, 1.4 μm, 1.35 μm, 1.3 μm, 1.25 μm, 1.2 μm, 1.15 μm, 1.1 μm, 1.05 μm, or 1.0 μm, or within a range between any two of the above values.

[0092] According to some embodiments of the present application, the thickness value h of the functional coating, the average diameter value a of the fibrous polymer, and the average length value D of the columnar inorganic particles satisfy: h > (a + 0.7D) / 1000. h > (a + 0.7D) / 1000 can make the angle between the inorganic particles and the normal of the separator < 45°, and when this condition is satisfied, the prepared separator can have excellent puncture resistance (safety), good porosity / ionic conductivity (performance), and high thermal barrier (safety). When h satisfies the above relationship, the prepared separator can have: 1. Optimized lithium ion transmission path: the vertical or near-vertical arrangement of the columnar structure forms a more direct ion transmission channel, significantly reducing the tortuosity of ion migration, thereby improving the electrochemical kinetic efficiency; 2. Higher effective porosity: the vertical or near-vertical arrangement of the columnar structure helps to save horizontal space, increase the effective pore volume and three-dimensional connectivity in the vertical direction, and provide a more abundant three-dimensional space network for ion transmission; 3. Faster electrolyte infiltration speed: the regular straight channel structure is conducive to the rapid and uniform penetration of the electrolyte, realizes efficient infiltration of the electrode-electrolyte interface, and shortens the battery liquid injection time; 4. Lower ion migration resistance: the shortened migration path and optimized pore structure synergistically reduce the interface impedance, reduce the battery ohmic resistance, significantly improve the large-rate charge and discharge performance and energy conversion efficiency; 5. Higher thermal safety performance: the shortened migration path and optimized pore structure synergistically reduce the interface impedance, reduce the battery ohmic resistance, significantly improve the large-rate charge and discharge performance and energy conversion efficiency. According to some embodiments of the present application, the thickness value h of the functional coating, the average diameter value a of the fibrous polymer, and the average length value D of the columnar inorganic particles satisfy: h - (a + 0.7D) / 1000 > 0.2.

[0093] According to some embodiments of the present application, the average length value L of the fibrous polymer satisfies: 50 ≤ L ≤ 5000.

[0094] In some embodiments, L is exemplarily 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000, 1050, 1100, 1150, 1200, 1250, 1300, 1350, 1400, 1450, 1500, 1550, 1600, 1650, 1700, 1750, 1800, 1850, 1900, 1950, 2000, 2050, 2100, 2150, 2200, 2250, 2300, 2350, 2400, 2450, 2500, 2550, 2600, 2650, 2700, 2750, 2800, 2850, 2900, 2950, 3000, 3050, 3100, 3150, 3200, 3250, 3300, 3350, 3400, 3450, 3500, 3550, 3600, 3650, 3700, 3750, 3800, 3850, 3900, 3950, 4000, 4050, 4100, 4150, 4200, 4250, 4300, 4350, 4400, 4450, 4500, 4550, 4600, 4650, 4700, 4750, 4800, 4850, 4900, 4950, or 5000, or within a range between any two of the above values.

[0095] According to some embodiments of the present application, the average length L of the fibrous polymer satisfies: 100≤L≤4000.

[0096] According to some embodiments of the present application, the average length L of the fibrous polymer satisfies: 500≤L≤3000.

[0097] According to some embodiments of the present application, the average length L of the fibrous polymer satisfies: 800≤L≤2000. The fibrous polymer is characterized by high aspect ratio, and interlaced and overlapped at the surface layer of the coating to form a three-dimensional horizontal cross-linking network.

[0098] According to some embodiments of the present application, the mass percentage of the fibrous polymer is controlled in the range of 5% to 50%, because in this range the bottom layer is mainly composed of columnar inorganic particles to ensure the thermal stability of the base film, and the top layer is mainly composed of fibrous polymers to form a porous network, reduce the contact angle of the electrolyte, and at the same time enhance the puncture resistance and flexibility. More preferably, the mass percentage is controlled in the range of 10% to 40%, in which case the liquid absorption rate of the separator is better.

[0099] Exemplarily, the fibrous polymer has a mass percentage of 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, or 50%, or within a range between any two of the above values.

[0100] According to some embodiments of the present application, the fibrous polymer is a key component, which has the function of providing liquid absorption and liquid retention of the electrolyte and forming a flexible interface buffer layer with the electrode to reduce the interface impedance.

[0101] Columnar inorganic particles

[0102] The columnar inorganic particles of the present application include at least one of silica particles, barium dititanate particles, zirconia particles, alumina particles, barium metatitanate particles, barium sulfate particles, tin oxide particles, titanium nitride particles, aluminum nitride particles, silicon oxide particles, calcium oxide particles, magnesium oxide particles, magnesium hydroxide particles, zinc oxide particles, titanium dioxide particles, boehmite particles, hydrated alumina particles, and ceramic particles.

[0103] According to some embodiments of the present application, the average diameter T of the columnar inorganic particles satisfies: 20≤T≤500.

[0104] Exemplarily, T has a value of 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, 300, 310, 320, 330, 340, 350, 360, 370, 380, 390, or 400, or within a range between any two of the above values.

[0105] According to some embodiments of the present application, the average diameter T of the columnar inorganic particles satisfies: 50≤T≤300.

[0106] According to some embodiments of the present application, the average length D of the columnar inorganic particles satisfies: 200≤D≤3000.

[0107] Exemplarily, the value of D is 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, 2100, 2200, 2300, 2400, 2500, 2600, 2700, 2800, 2900, 3000, or within a range between any two of the above values.

[0108] According to some embodiments of the present application, the average length value D of the columnar inorganic particles satisfies: 300≤D≤2000.

[0109] According to some embodiments of the present application, the angle θ between the columnar inorganic particles and the porous base film satisfies: 45°<θ<90° (i.e. the angle between the columnar inorganic particles and the normal of the porous base film is <45°). According to some embodiments of the present application, controlling the angle (tilt angle) between the columnar inorganic particles and the normal of the surface of the porous base film within a specific range can significantly improve the performance of the battery: on the one hand, this angle range can ensure that the root of the particles maintains sufficient contact area with the base film to form a stable mechanical anchoring interface; on the other hand, it can effectively disperse shear stress during battery charging and discharging vibration and electrode winding process, reducing the risk of interface failure caused by local stress concentration; at the same time, using a separator that meets this angle can significantly reduce the particle shedding rate, improve the cell interface bonding strength and prolong the cycle life, thereby significantly improving the high-rate charging and discharging cycle stability. This precise control of the tilt angle of the particles, through the optimization of its arrangement state, synergistically improves the mechanical reliability and electrochemical cycle performance of the battery.

[0110] Exemplarily, the angle between the columnar inorganic particles and the porous base film can be 45°, 50°, 55°, 60°, 65°, 70°, 75°, 75°, 80°, 85°, 86°, 87°, 88°, 89°, 89.5°, 89.9° or 90°, or within a range between any two of the above values.

[0111] According to the present application, when the angle between the columnar inorganic particles and the porous base film is greater than 45° (tending to be perpendicular), the performance of the separator can be significantly improved: this arrangement effectively reduces the obstruction of transverse pores, forms low-curved ion channels throughout the coating, improves the efficiency of lithium ion transmission, and reduces the interface impedance; and avoids the local pore closure caused by disordered accumulation, ensuring uniform electrolyte infiltration and reducing side reactions. In addition, the vertically arranged particles form a rigid skeleton through interlayer support, improving the puncture strength of the coating and effectively inhibiting the risk of lithium dendrite penetration; the three-dimensional rigid network formed by the particles significantly reduces the thermal shrinkage rate of the separator at high temperatures, avoiding short circuits; at the same time, the structure delays the heat diffusion through low thermal conductivity, reduces the probability of thermal runaway, and can adsorb impurities (such as HF) in the electrolyte, improving the chemical stability, thereby synergistically optimizing the cycle stability and safety of the battery.

[0112] According to some embodiments of the present application, a method for preparing a separator is provided, comprising the following steps:

[0113] S1: uniformly mixing the fibrous polymer, columnar inorganic particles, and binder in a solvent to obtain a slurry;

[0114] S2: after coating the slurry on the surface of the porous base film, pre-solidifying and drying to form the functional coating, thereby obtaining the separator.

[0115] According to some embodiments of the present application, the solvent can be one or a combination of water, dimethylacetamide (DMAC), dichloroethane, dimethylformamide (DMF), trichloroethane, trichloromethane, ethyl acetate, sulfolane, dimethyl sulfoxide (DMSO), N-methyl pyrrolidone (NMP), chloroform, and dichloromethane, and acetone. The solvent evaporation gradient control: using a combination of low-boiling point solvents and high-boiling point solvents to quickly form a concentration gradient on the surface of the coating, promoting the parallel spreading of fibers on the electrolyte side.

[0116] According to some embodiments of the present application, the binder can be any polymer material with a binding function in the art, including but not limited to aqueous binders and oily binders.

[0117] According to some embodiments of the present application, the binder of the present application is a non-fibrous polymer.

[0118] According to some embodiments of the present application, the solvent can be a combination of low-boiling point solvents and high-boiling point solvents to quickly form a concentration gradient on the surface of the coating, promoting the parallel spreading of fibers on the electrolyte side.

[0119] According to some embodiments of the present application, the coating speed is 10 m / min to 20 m / min. Illustratively, the coating speed is 10 m / min, 11 m / min, 12 m / min, 13 m / min, 14 m / min, 15 m / min, 16 m / min, 17 m / min, 18 m / min, 19 m / min or 20 m / min, or within a range between any two of the aforementioned values.

[0120] According to some embodiments of the present application, the shear rate during the coating process is also controlled to be 1000 s -1 to 1400 s -1 . Illustratively, the shear rate is 1000 s -1 , 1050 s -1 , 1200 s -1 , 1250 s -1 , 1300 s -1 , 1350 s -1 , or 1400 s -1 , or within a range between any two of the aforementioned values.

[0121] According to some embodiments of the present application, the coating method can be one or more of micro gravure coating, extrusion coating, dip coating, spray coating, dot coating or wire bar coating.

[0122] According to some embodiments of the present application, the coating amount is 0.5 g / m 2 to 3.0 g / m 2 , preferably 1.0 g / m 2 to 2.5 g / m 2 . When the coating amount is 0.5 g / m 2 to 3 g / m 2 , the columnar inorganic particle skeleton can form a continuous heat-resistant network and can achieve a higher level of ionic conductivity. Illustratively, the coating amount is 0.5 g / m 2 , 1.0 g / m 2 , 1.5 g / m 2 , 2.0 g / m 2 , 2.5 g / m 2 , or 3.0 g / m 2 , or within a range between any two of the aforementioned values.

[0123] The coating layer has a gradient structure, in which the inorganic short rod-shaped particles are arranged vertically in a high proportion near the side of the base film to form a heat-resistant support layer, and the fibrous polymer is arranged horizontally on the side in contact with the electrolyte.

[0124] The microgravure coating or extrusion coating technology is adopted, and by adjusting the coating speed and the shear force direction, the fibrous polymer is driven to arrange horizontally along the plane direction of the base film.

[0125] According to some embodiments of the present application, an electrochemical device is provided, comprising an electrolyte, an electrode and the above-mentioned separator.

[0126] According to some embodiments of the present application, the electrochemical device is a secondary battery, such as a lithium ion battery.

[0127] According to some embodiments of the present application, an electronic device is provided, comprising the above-mentioned electrochemical device.

[0128] The present application has the following advantages over the prior art: 1) the combination of organic components and inorganic components makes the coating have better affinity to electrolyte, and the separator has better wettability; 2) the coating has a gradient structure, in which the inorganic short rod particles are vertically arranged at a high proportion near the side of the base film to form a heat-resistant support layer, and the fibrous polymer is horizontally cross-linked on the side in contact with the electrolyte to form a porous wetting channel, thus balancing high heat resistance and high wettability.

[0129] II. Positive electrode

[0130] The electrochemical device of the present application comprises a positive electrode, wherein the positive electrode comprises a positive electrode current collector and a positive electrode active layer disposed on at least one side of the positive electrode current collector.

[0131] According to some embodiments of the present application, the positive electrode current collector is a metal foil or a composite current collector.

[0132] According to some embodiments of the present application, the metal foil is an aluminum foil. The composite current collector can comprise a metal foil substrate and a conductive layer disposed on at least one surface of the metal foil substrate.

[0133] According to some embodiments of the present application, the conductive layer comprises at least one of carbon, carbon black, graphite, expanded graphite, graphene, carbon fiber, graphitized carbon sheet, carbon tube, activated carbon and mesoporous carbon. The conductive layer can adopt nanomaterials, such as graphene nanosheets for graphene, carbon nanofibers for carbon fiber, carbon nanotubes for carbon tube, etc.

[0134] According to some embodiments of the present application, the positive electrode active layer comprises a positive electrode active material, a positive electrode binder and a positive electrode conductive agent.

[0135] According to some embodiments of the present application, the positive electrode active material is selected from the group consisting of LiCoO2, LiNiO2, LiNi x Mn y O2, Li 1+z Ni x Mn y Co 1-x-yO2, LiNi x Co y Al z O2, LiV2O5, LiTiS2, LiMoS2, LiMnO2, LiCrO2, LiMn2O4, Li2MnO3, LiFeO2, LiFePO4, LiMnPO4, and combinations thereof, wherein each x is independently 0.2 to 0.9 (exemplarily, it can be 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9, or within a range between any two of the foregoing); each y is independently 0.1 to 0.45 (exemplarily, it can be 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, or 0.45, or within a range between any two of the foregoing); and each z is independently 0 to 0.2 (exemplarily, it can be 0, 0.1, 0.15, or 0.2, or within a range between any two of the foregoing).

[0136] According to certain embodiments of the application, the positive active material is selected from the group consisting of LiCoO2, LiNiO2, LiNixMnyO2, Li 1+z Ni x Mn y Co 1-x-y O2(NMC), LiNi x Co y Al z O2, LiV2O5, LiTiS2, LiMoS2, LiMnO2, LiCrO2, LiMn2O4, LiFeO2, LiFePO4, and combinations thereof, wherein each x is independently 0.4 to 0.6; each y is independently 0.2 to 0.4; and each z is independently 0 to 0.1.

[0137] According to certain embodiments of the application, the positive active material is Li 1+x Ni a Mn b Co c Al (1-a-b-c) O2; wherein -0.2≤x≤0.2, 0≤a<1, 0≤b<1, 0≤c<1 and a+b+c≤1. According to some embodiments of the application, the positive active material has the general formula Li 1+x Ni a Mn b Co c Al (1-a-b-c)O2, where 0.33 < a < 0.92, 0.33 < a < 0.9, 0.33 < a < 0.8, 0.5 < a < 0.92, 0.5 < a < 0.9, 0.5 < a < 0.8, 0.6 < a < 0.92, or 0.6 < a < 0.9; 0 < b < 0.5, 0 < b < 0.3, 0.1 < b < 0.5, 0.1 < b < 0.4, 0.1 < b < 0.3, 0.1 < b < 0.2, or 0.2 < b < 0.5; 0 < c < 0.5, 0 < c < 0.3, 0.1 < c < 0.5, 0.1 < c < 0.4, 0.1 < c < 0.3, 0.1 < c < 0.2, or 0.2 < c < 0.5.

[0138] According to some embodiments of the present application, the positive active material is doped with a dopant selected from the group consisting of Fe, Ni, Mn, Al, Mg, Zn, Ti, La, Ce, Sn, Zr, Ru, Si, Ge, and combinations thereof. According to some embodiments of the present application, the dopant is not Fe, Ni, Mn, Mg, Zn, Ti, La, Ce, Ru, Si, or Ge. According to certain embodiments of the present application, the dopant is not Al, Sn, or Zr.

[0139] According to some embodiments of the present application, the positive active material comprises LiNi 0.33 Mn 0.33 Co 0.33 O2(NMC333), LiNi 0.4 Mn 0.4 Co 0.2 O2, LiNi 0.5 Mn 0.3 Co 0.2 O2(NMC532), LiNi 0.6 Mn 0.2 Co 0.2 O2(NMC622), LiNi 0.7 Mn 0.15 Co 0.15 O2, LiNi 0.8 Mn 0.1 Co 0.1 O2(NMC811), LiN i0.92 Mn 0.04 Co 0.04 O2, LiNi 0.8 Co 0.15 Al 0.05 O2(NCA), and LiNiO2(LNO).

[0140] The present application is not limited to the above-mentioned materials, but also includes other materials that can be used as a conductive agent for a battery negative electrode.

[0141] According to some embodiments of the present application, the positive electrode binder includes at least one of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) copolymer, polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorine-containing acrylate resin, polyacrylic acid, polyacrylonitrile, polyimide, polyurethane, polyvinyl butyral, polyvinylpyrrolidone (PVP), acrylic acid-acrylonitrile-acrylamide copolymer, and acrylic acid-acrylonitrile-acrylate copolymer. The present application is not limited to the above-mentioned materials, but also includes other materials that can be used as a positive electrode binder.

[0142] According to some embodiments of the present application, the positive electrode conductive agent includes at least one of carbon, carbon black, graphite, expanded graphite, graphene, superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon fibers, graphitized carbon sheets, carbon nanotubes, activated carbon, and mesoporous carbon. According to some embodiments of the present application, the positive electrode conductive agent can use nanomaterials, such as graphene nanosheets for graphene, carbon nanofibers for carbon fibers, carbon nanotubes for carbon nanotubes, etc. The present application is not limited to the above-mentioned materials, but also includes other materials that can be used as a positive electrode conductive agent.

[0143] III. Negative electrode

[0144] The negative electrode includes a negative electrode current collector and a negative electrode active layer disposed on at least one side of the negative electrode current collector, wherein the negative electrode active layer includes a negative electrode active material, a negative electrode binder, and a negative electrode conductive agent.

[0145] According to some embodiments of the present application, the negative electrode active material includes at least one of natural graphite particles, synthetic graphite particles, hard carbon, soft carbon, mesocarbon microbeads (MCMB), Sn, SnO2, SnO, Li4Ti5O 12 (LTO), Si material, silicon-carbon (Si-C) composite material, silicon-nitrogen (Si-N) composite material, and silicon-oxygen (Si-O) composite material. The present application is not limited to the above-mentioned materials, but also includes other materials that can be used as a negative electrode active material.

[0146] According to some embodiments of the present application, the negative electrode binder includes at least one of polyacrylic acid, polymethacrylic acid, polyacrylate, polymethacrylate, polyacrylamide, styrene butadiene rubber, acrylated styrene butadiene rubber, acrylic-acrylonitrile-acrylamide copolymer, acrylic-acrylonitrile-acrylate copolymer, acrylonitrile-butadiene rubber, nitrile rubber, acrylonitrile-styrene-butadiene copolymer, acryl rubber, butyl rubber, fluoro rubber, polytetrafluoroethylene, polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, latex, acrylic resin, phenolic resin, epoxy resin, carboxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl cellulose, carboxymethyl chitosan, polyester, polyamide, polyether, polyimide, polycarboxylate, polycarboxylic acid, polyurethane, alginate, fluorinated polymer, chlorinated polymer, polyvinylidene fluoride, poly(vinylidene fluoride)-hexafluoropropylene. The present application is not limited to the above-mentioned materials, and includes other materials that can be used as a battery negative electrode binder.

[0147] According to some embodiments of the present application, the negative electrode conductive agent includes at least one of carbon, carbon black, graphite, expanded graphite, graphene, graphene nanoplatelets, superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon fibers, carbon nanofibers, graphitized carbon sheets, carbon tubes, carbon nanotubes, activated carbon, mesoporous carbon. According to some embodiments of the present application, the negative electrode conductive agent can use nanomaterials, such as graphene using graphene nanoplatelets, carbon fibers using carbon nanofibers, carbon tubes using carbon nanotubes, etc. The present application is not limited to the above-mentioned materials, and includes other materials that can be used as a battery negative electrode conductive agent.

[0148] IV. Electrolyte

[0149] The electrolyte is also included in the electrochemical device of the present application.

[0150] According to some embodiments of the present application, the electrolyte includes at least one of a gel electrolyte, a solid-state electrolyte, and a liquid electrolyte.

[0151] According to some embodiments of the present application, the liquid electrolyte includes a non-aqueous solvent and a lithium salt.

[0152] According to some embodiments of the present application, the lithium salt includes at least one of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, LiSiF6, LiBOB, and lithium difluoroborate.

[0153] According to some embodiments of the present application, the non-aqueous solvent can be at least one of a carbonate compound, a carboxylic acid ester compound, an ether compound.

[0154] According to some embodiments of the present application, the carbonate compound includes at least one of a chain carbonate compound, a cyclic carbonate compound, a fluorinated carbonate compound.

[0155] According to some embodiments of the present application, the chain carbonate compound includes diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), and combinations thereof. Examples of the cyclic carbonate compound are ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinyl ethylene carbonate (VEC), and combinations thereof. Examples of the fluorinated carbonate compound are at least one of fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methyl ethylene carbonate, 1-fluoro-1-methyl ethylene carbonate, 1,2-difluoro-1-methyl ethylene carbonate, 1,1,2-trifluoro-2-methyl ethylene carbonate, and trifluoromethyl ethylene carbonate.

[0156] According to some embodiments of the present application, examples of the carboxylic acid ester compound are at least one of methyl acetate, ethyl acetate, n-propyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanolactone, valerolactone, methylvaleronolactone, caprolactone, and methyl formate.

[0157] According to some embodiments of the present application, examples of the ether compound are dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, and combinations thereof.

[0158] According to some embodiments of the present application, the non-aqueous solvent includes at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidinone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and a phosphate ester.

[0159] The present application also provides an electronic device including the electrochemical device of the present application.

[0160] The present application provides an electrochemical device, including any device in which electrochemical reactions occur to convert chemical energy and electrical energy to each other, specific non-limiting examples including all kinds of primary batteries, secondary batteries, fuel cells, solar cells or capacitors. In particular, the electrochemical device is a lithium secondary battery, including a lithium metal secondary battery, a lithium ion secondary battery or a lithium polymer secondary battery.

[0161] In some embodiments, the electrochemical device includes a positive electrode, a negative electrode, an electrolyte, and a separator, the separator is located between the positive electrode and the negative electrode, and the electrochemical device adopts the separator described above in the present application.

[0162] The use of the electrochemical device of the present application is not particularly limited, which can be used in any electronic device known in the prior art. According to some embodiments of the present application, the electronic device includes but is not limited to mobile phones, mobile phones, smart phones, notebook computers, tablet computers, wearable devices, smart watches, smart bracelets, smart glasses, mobile power supplies, televisions, game consoles, game controllers, digital cameras, smart speakers, earphones, keyboards, mice, displays, drones, sound systems, household appliances, toys, power tools, cars, motorcycles, electric bicycles, bicycles, robots, robotic dogs, industrial robots, humanoid robots, etc.

[0163] The preparation of the separator of the present application scheme and its application in lithium ion batteries are described below taking lithium ion batteries as an example and in combination with specific examples, and those skilled in the art will understand that the preparation methods described in the present application are only examples, and any other suitable preparation method is within the scope of the present application.

[0164] The test methods used in the examples are conventional methods unless otherwise specified; the reagents and the like used, unless otherwise specified, are commercially available reagents and materials. The source information of the raw materials used in the following examples and comparative examples is only illustrative, and does not constitute any limitation on the purchase of raw materials. Those skilled in the art know that the relevant raw materials can be obtained through other commercial channels, or prepared by conventional methods in the art.

[0165] The polyethylene film (thickness of 12 μm) was purchased from Enjet.

[0166] The polyamide (CAS No. 63428-84-2) was purchased from Dongguan Feierbo New Material Technology Co., Ltd.

[0167] The boehmite (Al2O3, CAS No. 1318-23-6) was purchased from Sasol.

[0168] The polyacrylate (CAS No. 9003-01-4) was purchased from BASF SE.

[0169] Silica (Si02): Silica for Example 2 and Comparative Example 2 was purchased from Evonik Industries AG, and silica for Example 6 and Comparative Example 6 was purchased from Cabot Corporation.

[0170] Polyurethane (CAS No. 9009-54-5) was purchased from Covestro AG.

[0171] Titanium dioxide (Ti02, CAS No. 13463-67-7) was purchased from Tronox Holdings plc.

[0172] Polyimide (CAS No. 25038-81-7) was purchased from DuPont de Nemours, Inc.

[0173] Zirconium dioxide (Zr02, CAS No. 1314-23-4) was purchased from Tosoh Corporation.

[0174] Polyvinyl alcohol (CAS No. 9002-89-5) was purchased from Kuraray Co., Ltd.

[0175] Polyacrylamide (CAS No. 9003-05-8) was purchased from SNF.

[0176] Example 1

[0177] Preparation of separator

[0178] The separator of the present application, as shown in Figure 1 includes a porous base film (polyolefin base film) and a functional coating layer provided on one side of the porous base film, which is composed of fibrous polymer and columnar inorganic particles. In the functional coating layer, the mass ratio of fibrous polymer and columnar inorganic particles is: fibrous polymer 30%, columnar inorganic particles 70%. Among them, the fibrous polymer has an average length L and an average diameter a. The columnar inorganic particles have an average length D and an average diameter T, and r = D / L and C = D / T can be obtained by calculation. The types of functional coating materials of the separator and their physical property parameters are summarized in Table 1.

[0179] The preparation steps include:

[0180] (1) Slurry preparation: 30 parts of polyamide, 70 parts of boehmite particles, and 15 parts of binder (PVDF) were dispersed in the solvent acetone in proportion, stirred at 2000 rpm for 2 hours to form a uniform slurry;

[0181] (2) Coating process: slurry was coated on one side of PE base film with thickness of 12 pm by using slot coating technology. By controlling the coating speed of 15 m / min, the slurry passed through the die gap of ≤50 pm at high speed, generating a strong shear flow field of up to 1200 s -1 -1. Under the action of this shear field, boehmite fibers were oriented and rotated, and their long axes gradually arranged perpendicular to the plane of the base film (angle <45° with the normal line of the base film). To strengthen the orientation effect, the slurry viscosity and the surface energy of the base film (treated by corona) were simultaneously controlled to reduce the rotation resistance of the fibers; and the gradient drying process (75°C→120°C) was used to lock the orientation structure, finally realizing the oriented coating with the perpendicularity deviation angle of boehmite fibers <45°.

[0182] (3) Pre-curing treatment: the coated separator was pre-cured at 32°C for 30 seconds by hot air to lock the vertical orientation structure of boehmite fibers (angle <45° with the normal line of the base film). The vertical arrangement of fibers formed by shear coating was in a metastable state in the wet slurry, and the 32°C hot air accelerated the evaporation of the solvent acetone, causing the viscosity of the slurry to rise sharply, thereby quickly fixing the spatial position of the fibers. This temperature (32°C) is much lower than the melting point of the fibrous polymer, which can ensure that its fiber morphology does not melt and deform, maintaining the integrity of the initial structure.

[0183] (4) Post-treatment: the separator was baked at 45°C for 30 seconds, and finally baked at 60°C for 30 seconds to remove residual solvents. The final coating thickness of the separator was 1.0 pm, and the coating amount was 2.0 g / m 2 . The coating thickness was measured by a Malvern thickness gauge before and after coating. The base film thickness was B1, and the total thickness of the separator was B2. The functional coating thickness h = B2-B1, and the average value of three groups of coating thicknesses was taken.

[0184] Further, the coating thickness h (pm) needs to satisfy the physical constraint equation h > (a + 0.7D) / 1000 to ensure that the angle Q between the columnar particles and the normal of the base film is < 45°. The separator satisfying this thickness requirement (h > (a + 0.7D) / 1000) has excellent puncture resistance (improving safety), good porosity and ionic conductivity (optimizing performance), and high-efficiency thermal barrier effect (enhancing thermal safety). On the contrary, if the coating thickness is insufficient (h < (a + 0.7D) / 1000), the particles will be more inclined: on the one hand, the interlaced inclined columns will significantly increase the tortuosity of the ion transport path, reducing the lithium ion conduction rate; on the other hand, the column occupies more lateral space, reducing the effective porosity and damaging the pore connectivity, thus delaying the electrolyte imbibition rate; at the same time, the long and tortuous ion path causes the cell resistance to rise (ohmic impedance increases), damaging the rate performance and energy efficiency; in addition, when heated and melted, the physical barrier formed by the inclined columns has reduced density, significantly weakening the thermal barrier effect and adversely affecting the blocking of the positive and negative electrode contact and heat transfer during the thermal runaway process.

[0185] Preparation of electrochemical device

[0186] Preparation of the negative electrode

[0187] The negative electrode active material artificial graphite, the conductive agent (Super P), the binder styrene-butadiene rubber, and the thickening agent sodium carboxymethyl cellulose were dissolved in a deionized water solvent system according to a weight ratio of 98:0.5:1:0.5, fully stirred and mixed uniformly to prepare a negative electrode slurry. The copper foil was used as the negative electrode current collector, and the negative electrode slurry was coated from the starting end of the copper foil towards the terminal opposite to the starting end, dried, cold-pressed, and slitted to obtain the negative electrode.

[0188] Preparation of the positive electrode

[0189] The positive electrode active material lithium cobaltate, the conductive carbon (Super P), and the binder polyvinylidene fluoride (PVDF) were dissolved in an N-methyl pyrrolidone solvent (NMP) system according to a weight ratio of 96:2:2, fully stirred and mixed uniformly to prepare a positive electrode slurry. The aluminum foil was used as the positive electrode current collector, and the positive electrode slurry was coated from the starting end of the aluminum foil towards the terminal opposite to the starting end, dried, cold-pressed, and slitted to obtain the positive electrode.

[0190] Assembly of the battery

[0191] The above separator, positive and negative electrodes, and electrolyte were assembled into a battery, specifically:

[0192] The positive electrode sheet, the separator and the negative electrode sheet are laminated to form a laminated structure, and the laminated structure is wound around a center axis into a flat electrode assembly from a first end of the separator. Then the electrode assembly is dried in a box-type resistance furnace at 105°C for about 16 hours under vacuum. A solution of lithium salt LiPF6 and non-aqueous organic solvent (ethylene carbonate (EC): diethyl carbonate (DEC): propylene carbonate (PC): propyl propionate (PP): vinylene carbonate (VC)) = 20:30:20:28:2, mass ratio) is prepared in a mass ratio of 8:92 as an electrolyte for a lithium ion battery. The electrode assembly is placed in an outer package, injected with an electrolyte and packaged, and after formation, the final lithium ion battery product is made.

[0193] Examples 2 to 6

[0194] Examples 2 to 6 use the same preparation method as Example 1, which is different from Example 1 in that the types and physical property parameters of the functional coating material of the separator are different. The schemes of Examples 2 to 6 are summarized in Table 1.

[0195] The types and physical property parameters of the fibrous polymer and columnar inorganic particle components in Examples 1 to 6 are shown in Table 1 below.

[0196] Table 1

[0197] Comparative Examples 1 to 6

[0198] Comparative Examples 1 to 6 use the same preparation method as Example 1, which is different from Example 1 in that the types and physical property parameters of the functional coating material of the separator are different. The types and physical property parameters of the fibrous polymer and columnar inorganic particle components used in Comparative Examples 1 to 6 are shown in Table 2 below.

[0199] Table 2

[0200]

[0201]

[0202] Test methods

[0203] The thermal shrinkage properties, wettability, porosity, ion impedance, separator liquid retention coefficient and capacity retention rate of 1000 times of the separators in Examples 1-6 and Comparative Examples 1-6. Among them:

[0204] 1. Test method for heat shrinkage property:

[0205] Cut the separator into 100 mm x 100 mm sample, use a steel ruler to mark an 80 x 80 mm measuring reference frame in the center area of the sample. Use an image measuring instrument to measure the initial longitudinal (MD0) and transverse (TD0) dimensions of the reference frame. Then clamp the sample in 6 layers of standard copy paper (3 layers on top and bottom), and place it in a 150℃ constant temperature oven for heat treatment for 30 minutes. After taking it out, naturally cool it, re-measure the dimensions of the reference frame after shrinkage (MD1 and TD1), and calculate the heat shrinkage rate. The calculation formula of the heat shrinkage rate R is as follows: R = (MD0 + TD0 - MD1 - TD1) / (MD0 + TD0) * 100%.

[0206] 2. Test method for wettability:

[0207] Take a suitable separator sample (100 mm x 100 mm), use a clamp to pull the sample horizontally apart; then take 10 μL of electrolyte and drop it in the middle of the sample, after 60 s, measure two perpendicular diffusion diameters, count O1 and O2; the wettability of the separator = (O1 + O2) / 2.

[0208] 3. Test method for porosity:

[0209] Cut the separator sample with an area of A (cm 2 ), after vacuum drying at 105℃ for 2 hours, measure the thickness d (cm) and record the initial mass M1 (g). Completely immerse the sample in an inert solvent (hexadecane / anhydrous ethanol), soak at a constant temperature of 25℃ for 24 hours until saturated adsorption. After taking it out, quickly absorb the surface residual solvent with filter paper (within 3 seconds), immediately weigh the saturated mass M2 (g). Porosity = (M2 - M1) / (p x A x d). Where p is the density of the solvent (g / cm 3 ).

[0210] 4. Test method for ion impedance:

[0211] Place the electrolyte-impregnated separator between two stainless steel (SS) electrodes to form a SS | separator / electrolyte | SS sandwich structure. Apply a sinusoidal alternating current signal with an amplitude of 10 mV and a frequency of 10 mHz - 100 kHz through an electrochemical workstation, and collect the Nyquist plot. Take the impedance value at the intersection of the high frequency curve (> 10 kHz) with the real axis as the ohmic resistance R Ω , which is the ion migration resistance of the separator body, and the ion impedance Z ion = R Ω .

[0212] 5. Test method for liquid retention coefficient of separator:

[0213] Take a 10 cm x 10 cm separator sample, and pre-treat it in a dry box at 25℃ ± 2℃ and a humidity of ≤ 10% RH for 24 hours, and weigh the dry weight Md The sample was completely immersed in the actual electrolyte (e.g. 1M LiPF6 / EC:DMC = 1:1 (v / v)) and soaked for 60 ± 0.5 min at 25°C under constant temperature conditions with vacuum-assisted bubble removal. After removal, the sample was hung vertically and drained for 60 s, and immediately two-sidedly absorbed residual liquid with inert PTFE filter paper with a single light pressure of 0.1 N, and the wet weight Mwetwas obtained by weighing within 10 s. w The liquid retention coefficient = (Mdry- Mwet) / Mdry x 100% w d d

[0214] 6. Test method for cycle capacity retention rate of battery:

[0215] According to the JIS C 8712:2019 Portable Sealed Secondary Cells or Batteries - Safety Requirements standard, the cycle performance test was performed using an Arbin battery test system in a constant temperature environment of 25°C using a high-precision test system (e.g. LAND CT3001A): constant current charging at 1C to the cut-off voltage (4.2V), and then constant voltage charging until the current decayed to 0.05C; constant current discharging at 1C to the cut-off voltage (2.5V), and the sample was rested for 5 min between charging and discharging, and the initial discharge capacity C0was recorded; after 1000 cycles, the capacity C1000was measured, and the capacity retention rate was calculated as η = (C1000 / C0) x 100%. 1000 1000

[0216] The test results of Examples 1-6 and Comparative Examples 1-6 are shown in Table 3.

[0217] Table 3

[0218]

[0219]

[0220] As can be seen from Table 3, when the value of r is in the range of 0.05-1 and the value of C is in the range of 2-10, the separator can significantly improve the wettability while maintaining good thermal shrinkage.

[0221] In terms of thermal shrinkage performance: the thermal shrinkage rate (150°C / 0.5h) of Examples 1-6 was 4.8%-6.1%, and good thermal shrinkage resistance was obtained, and the thermal shrinkage rate of Comparative Example 6 (17.6%) was significantly deteriorated, and the above results showed that when r≥0.05, the stable three-dimensional network structure formed inside the functional coating could effectively inhibit the molecular chain movement at high temperature, thereby reducing the thermal shrinkage rate. When the aspect ratio C < 2, effective directional arrangement cannot be formed by electric field or shear force, resulting in disordered accumulation inside the coating, weakening the mechanical support effect, and significantly reducing the anti-branching puncture ability and heat resistance of the separator.

[0222] ​​​​​Infiltration: The infiltration (electrolyte diffusion diameter) of Examples 1-6 was 38-42 mm, and good electrode liquid infiltration performance was obtained. Comparative Examples 1-6 all showed different degrees of decline. The above results show that the length of the fibrous polymer and the aspect ratio of the columnar inorganic particles are controlled within a certain range to form connected pores in the coating, making the electrolyte absorption path unobstructed, thereby improving the infiltration. Therefore, the control of r value is a necessary condition to obtain good infiltration, and the structural stability has a synergistic effect on the simultaneous possession of high thermal stability and high infiltration.

[0223] Porosity: The porosity of Examples 1-6 was 43.8-48.2%, and good separator porosity was obtained. Comparative Examples 1-6 all showed different degrees of decline. The above results show that when the ratio of the particle size of the columnar inorganic particles and the length of the fibers is appropriate, the particles can uniformly fill the fiber gap to form a continuous pore structure, thereby improving the porosity. Therefore, the accurate control of r value is the core element of building a high-porosity structure, and the aspect ratio of the inorganic particles has a synergistic effect on pore formation by affecting the uniformity of filling.

[0224] Ion impedance: The ion impedance of Examples 1-6 was 0.78-0.92 Ω, and good ion conductivity was obtained. The ion impedance of Comparative Examples 1-6 was significantly increased. The above results show that the regulation of r value and C value also has a synergistic effect on reducing ion impedance.

[0225] Liquid retention coefficient: The liquid retention coefficient of Examples 1-6 was 120.8-123.5%, and good liquid retention performance was obtained. Comparative Examples 1-6 all showed different degrees of decline. The above results show that the connected pore structure can quickly absorb electrolyte and provide sufficient storage space, thereby improving the liquid retention capacity. Therefore, the synergistic optimization of pore structure and infiltration is a double guarantee for obtaining a high liquid retention coefficient, and the r value plays a core role in regulating the connectivity of the pores.

[0226] Capacity retention rate: The 1000-cycle capacity retention rate of Examples 1-6 was 94.5-96.1%, and good battery cycle performance was obtained. Comparative Examples 1-6 showed different degrees of decline. The above results show that the triple guarantee of structural stability, pore optimization, and ion uniformity can effectively inhibit side reactions and structural degradation during the cycle process. Therefore, the synergistic control of various parameters is a necessary condition to achieve high cycle life, and the structural stability has a decisive influence on long-term performance.

[0227] Reference in the specification to "an embodiment" or "the embodiments" means that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the application. The appearances of the phrase "in some embodiments," "in certain embodiments," "in one embodiment," or other similar phrases in various places in the specification are not necessarily referring to the same embodiment. Furthermore, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments.

[0228] While the illustrative embodiments have been described and illustrated, it will be understood by those skilled in the art that the above-described embodiments are not the only ways in which the present application can be practiced. Changes can be made to the embodiments in light of the teachings of the present disclosure, and it is understood that well-known elements have not been described in order to not obscure the present application.

Claims

1. A diaphragm, characterized by A porous base film and a functional coating layer provided on at least one side of the porous base film, the functional coating layer comprising a fibrous polymer and columnar inorganic particles, the fibrous polymer having an average length of Lnm, the columnar inorganic particles having an average length of Dnm and an average diameter of Tnm, wherein D / L satisfies 0.05≤D / L≤1 and D / T satisfies 2≤D / T≤10.

2. The separator according to claim 1, characterized in that The average length of the fibrous polymer satisfies 50≤L≤5000; and / or, the average diameter of the fibrous polymer satisfies 1≤a≤300.

3. The separator of claim 1, wherein The average length of the columnar inorganic particles satisfies 200≤D≤3000; and / or, the average diameter of the columnar inorganic particles satisfies 20≤T≤500.

4. The diaphragm of claim 2, wherein, The thickness of the functional coating layer satisfies h>(a+0.7D) / 1000.

5. The separator according to any one of claims 1 to 4, characterized in that, The fibrous polymer comprises at least one of a halogenated polymer, a polyester polymer, a polycarboxylic acid polymer, a polyurethane polymer, a polyamide polymer, a polyimide polymer, a vinyl polymer, a polyether polymer, an engineering plastic polymer, a conductive polymer, cellulose and its derivatives, or a rubber / elastomer.

6. The separator according to any one of claims 1 to 4, characterized in that, The fibrous polymer comprises at least one of polyvinylidene fluoride, a homopolymer or copolymer formed from vinylidene fluoride and another copolymerizable monomer, polytetrafluoroethylene, a fluorinated ethylene propylene copolymer, a perfluorosulfonic acid resin, a polycarboxylate, a polycaprolactone, a polyacrylate, a polyurethane, a polyamide, a polyimide, a polyacrylonitrile, a polyethylene oxide, a polyacrylic acid, a polymethacrylic acid, a polymethacrylate, a polyvinyl alcohol, a polyvinyl acetate, a polyacrylamide, a polyphenylene ether, a polyvinyl compound, a polystyrene, a polyvinylpyrrolidone, an acrylonitrile-styrene-butadiene copolymer, a polyphenylene sulfide, a polyether ether ketone, a polyaramid, a polypyrrole, a polyaniline, a polythiophene, a polyethylene glycol, a polylactic acid, cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, carboxymethyl cellulose, cyanoethyl cellulose, nitrile rubber, styrene butadiene rubber, and latex; wherein the copolymerizable monomer comprises one or more of tetrafluoroethylene, hexafluoropropylene, trifluoroethylene, trichloroethylene, and fluoroethylene.

7. The separator according to any one of claims 1 to 4, characterized in that, The columnar inorganic particles comprise at least one of silica particles, barium dititanate particles, zirconium dioxide particles, aluminum oxide particles, barium metatitanate particles, barium sulfate particles, tin oxide particles, titanium nitride particles, aluminum nitride particles, silicon oxide particles, calcium oxide particles, magnesium oxide particles, magnesium hydroxide particles, zinc oxide particles, titanium dioxide particles, boehmite particles, hydrated aluminum oxide particles, and ceramic particles.

8. The separator according to any one of claims 1 to 4, characterized in that, The porous base film comprises polyolefin, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyether ether ketone, polyether sulfone, polyphenylene ether, polyphenylene sulfide, polyacrylonitrile, polyvinylidene fluoride, polytetrafluoroethylene, polyvinylidene fluoride-hexafluoropropylene copolymer, polyformaldehyde, polyvinylpyrrolidone, or a combination thereof.

9. An electrochemical device, characterized by, An electrolyte, an electrode, and the separator of any one of claims 1 to 8.

10. An electronic device, comprising: An electrochemical device comprising the separator of claim 9.

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