Electrochemical Devices

Abstract

An electrochemical device comprises an electrode plate (1) and a porous layer (2) formed on the surface of the electrode plate (1), wherein the porous layer (2) comprises nanofibers and inorganic particles, and the nanofibers and inorganic particles are bonded via a crosslinking agent. Thus, the mechanical strength of the porous layer (2) is improved, so that the porous layer (2) has a stronger ability to resist penetration by positive and negative electrode particles, thereby ensuring that the electrochemical device has lower self-discharge and higher cycle performance.

Description

Technical Field

[0001] The present application relates to an electrochemical device and an electronic device comprising the electrochemical device, and more specifically, the present application relates to a lithium ion battery and an electronic device comprising the lithium ion battery. Background Art

[0002] Lithium-ion batteries have many advantages such as high energy density, long cycle life, high nominal voltage (>3.7V), and low self-discharge rate, and are widely used in the field of consumer electronics. With the rapid development of electric vehicles and mobile electronic devices in recent years, people have higher and higher requirements for the energy density, safety, and cycle performance of lithium-ion batteries, and are looking forward to the emergence of new lithium-ion batteries with comprehensive performance improvements. Among them, setting a fiber porous layer between the positive and negative electrodes of lithium-ion batteries instead of the traditional ordinary isolation membrane is a new technology that has attracted much attention.

[0003] The fibrous porous layer prepared on the surface of the electrode plate by the spinning method can be directly integrated into the surface of the electrode plate, without the step of separately making an isolation membrane in the traditional process, which can simplify the production process of lithium-ion batteries. At the same time, since the thickness of the fibrous porous layer prepared by spinning can be made thinner, the energy density of the lithium-ion battery can be improved. At the same time, the fibrous porous layer prepared by spinning also has a higher porosity than the traditional isolation membrane, which can improve the liquid retention capacity of the lithium-ion battery, and has therefore received widespread attention.

[0004] At present, the fiber porous layer prepared by spinning is combined with nanometer or micrometer fibers in a directional or random manner, and the random overlap between each fiber forms a large number of holes for the transmission of ions, and the fiber itself serves as the skeleton of the fiber porous layer. However, the mechanical strength of the fiber itself and the bonding force between the fibers are weak, resulting in insufficient mechanical strength of the fiber porous layer as a whole, which easily leads to local internal short circuit under the piercing of particles in the positive and negative electrodes, causing the self-discharge degree of lithium ion batteries (such as poor K value) to increase, or even the exothermic explosion of lithium ion batteries, resulting in potential safety hazards. For this reason, it is urgent to develop a technology that can improve the mechanical strength of the fiber porous layer and the bonding force between the fibers in the fiber porous layer to improve the performance of lithium ion batteries. Summary of the invention

[0005] The object of the present application is to provide an electrochemical device, the porous layer of which has good puncture resistance.

[0006] In a first aspect, the present application provides an electrochemical device, comprising an electrode plate and a porous layer formed on the surface of the electrode plate, wherein the porous layer contains nanofibers and inorganic particles, and the nanofibers and the inorganic particles are bonded by a crosslinking agent.

[0007] In some embodiments of the first aspect of the present application, the porous layer also includes an initiator. Calculated by the mass percentage of the porous layer, the content of the nanofibers is 4.9% to 95%, the content of the inorganic particles is 4.9% to 95%, and the content of the cross-linking agent and the initiator is 0.1% to 40%, wherein the initiator accounts for 5% to 20% of the total mass of the cross-linking agent and the initiator.

[0008] In some embodiments of the first aspect of the present application, the puncture strength P of the porous layer and the ratio M of the mass of the inorganic particles to the total mass of the porous layer satisfy the following relationship (1):

[0009] 9≤P / (M+1)≤150 Formula (1)

[0010] The unit of the puncture strength P is N / 20 μm.

[0011] In some embodiments of the first aspect of the present application, P≥16, preferably P≥20.

[0012] In some embodiments of the first aspect of the present application, the crosslinking agent includes at least one of polyisocyanate, hexamethoxymethyl melamine, N-hydroxymethyl acrylamide, carbodiimide, trimethylolpropane, aziridine, diisopropyl peroxide, butyl acrylate, N,N′-methylenebisacrylamide, 2,5-dimethyl-2,5-bis(tert-butyl peroxide)hexane, bisphenol A epoxy resin, acrylate derivatives, nitrile-containing polymers, styrene, vinyl fluoride, acrylonitrile, acrylic amine, vinyl acetate, alkyl vinyl ether, alkylene oxide or oxetane derivatives.

[0013] In some embodiments of the first aspect of the present application, the initiator is selected from at least one of benzoyl peroxide, tert-butyl benzoyl peroxide, methyl ethyl ketone peroxide, azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, azobisisobutylamidine hydrochloride, boron trifluoride, phosphorus pentafluoride, titanium tetrachloride, tin tetrachloride or zinc dichloride.

[0014] In some embodiments of the first aspect of the present application, the nanofibers include flat ribbon-shaped fibers, and the ratio of the length values ​​of the widest part to the narrowest part of the cross-section of the flat ribbon-shaped fibers is between 2 and 100, preferably 5 to 20.

[0015] In some embodiments of the first aspect of the present application, the nanofiber comprises at least one of polyvinylidene fluoride, polyimide, polyamide, polyacrylonitrile, polyethylene glycol, polyethylene oxide, polyphenylene ether, polypropylene carbonate, polymethyl methacrylate, polyethylene terephthalate, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-chlorotrifluoroethylene and their derivatives, and preferably comprises at least one of polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyphenylene ether, polypropylene carbonate, polyethylene oxide, etc. and their derivatives.

[0016] In some embodiments of the first aspect of the present application, the porous layer has at least one of the following characteristics:

[0017] (a) The air permeability of the porous layer is 5s / 100cm 3 ~400s / 100cm 3 ;

[0018] (b) the porosity of the porous layer is 30% to 95%;

[0019] (c) the average pore size of the porous layer is 20 nm to 10 μm;

[0020] (d) the thickness of the porous layer is 1 μm to 20 μm;

[0021] (e) the pore size of the porous layer decreases linearly along the thickness direction from away from the electrode plate to close to the electrode plate;

[0022] (f) the pore size of the porous layer decreases nonlinearly along the thickness direction from far away from the electrode plate to close to the electrode plate;

[0023] (g) The pore size of the porous layer decreases discontinuously along the thickness direction from far away from the electrode pad to close to the electrode pad.

[0024] In some embodiments of the first aspect of the present application, the number of the inorganic particles in the porous layer per unit area is 5×10 7 pcs / m 2 ~3×10 19 pcs / m 2 .

[0025] In some embodiments of the first aspect of the present application, the mass of the inorganic particles in the porous layer per unit area is 0.004 g / m 2 ~60g / m 2 .

[0026] In some embodiments of the first aspect of the present application, the average particle size of the inorganic particles is 0.01 μm to 10 μm.

[0027] In some embodiments of the first aspect of the present application, the inorganic particles are selected from any one or a mixture of at least two of the following: HfO2, SrTiO3, SnO2, CeO2, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, boehmite, magnesium hydroxide, aluminum hydroxide, lithium phosphate, lithium titanium phosphate, lithium aluminum titanium phosphate, lithium lanthanum titanate, lithium germanium thiophosphate, lithium nitride, SiS2 glass, P2S5 glass, Li2O, LiF, LiOH, Li2CO3, LiAlO2, Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2 ceramics and garnet ceramics.

[0028] In some embodiments of the first aspect of the present application, the porous layer is prepared by electrospinning, air spinning or centrifugal spinning.

[0029] In some embodiments of the first aspect of the present application, the nanofiber comprises a core layer and a shell layer, and the crosslinking agent and the initiator are contained in the shell layer.

[0030] A second aspect of the present application provides an electronic device, comprising the electrochemical device provided in the first aspect of the present application.

[0031] The electrochemical device provided in the present application uses a crosslinking agent to crosslink the nanofibers with the surface of the inorganic particles, thereby improving the relative slip problem between the fibers in the porous layer and improving the mechanical strength of the porous layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present application and the technical solutions of the prior art, the following briefly introduces the drawings required for use in the embodiments and the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 A schematic diagram of the structure of an implementation scheme of the present application;

[0034] Figure 2 This is a structural schematic diagram of another implementation scheme of the present application;

[0035] Figure 3 This is a structural schematic diagram of another implementation scheme of the present application;

[0036] Figure 4 This is a micrograph of the fiber layer of Comparative Example 2 of the present application;

[0037] Figure 5This is a micrograph of the porous layer of Example 2 of the present application. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical scheme, and advantages of the present application more clearly understood, the present application is further described in detail with reference to the accompanying drawings and examples. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0039] The electrochemical device of the present application may be any electrochemical device using an electrode plate and a porous layer, such as a lithium-ion battery, a capacitor, etc., and the following description is made by taking a lithium-ion battery as an example. Those skilled in the art should understand that the following description is only for illustrative purposes and does not limit the scope of protection of the present application.

[0040] One aspect of the present application provides an electrochemical device, such as Figure 1-3 As shown, it includes an electrode plate 1 and a porous layer 2 formed on the surface of the electrode plate 1, wherein the porous layer 2 contains nanofibers and inorganic particles, and the nanofibers and the inorganic particles are combined by a cross-linking agent.

[0041] The electrode sheet 1 may be a positive electrode sheet 101 and / or a negative electrode sheet 102, and the porous layer 2 may be disposed on the positive electrode sheet 101 and / or the negative electrode sheet 102 to separate the positive electrode sheet 101 from the negative electrode sheet 102. The porous layer 2 may be disposed on one surface or both surfaces of the positive electrode sheet and / or the negative electrode sheet.

[0042] In some embodiments of the present application, the porous layer also includes an initiator. Calculated by the mass percentage of the porous layer, the content of the nanofibers is 4.9% to 95%, the content of the inorganic particles is 4.9% to 95%, the content of the cross-linking agent and the initiator is 0.1% to 40%, and the initiator accounts for 5% to 20% of the total mass of the cross-linking agent and the initiator.

[0043] Since the nanofibers and inorganic particles are bonded by the cross-linking agent, the nanofibers and inorganic particles are combined into a whole, preventing the inorganic particles from sliding between the nanofibers, thereby improving the overall strength of the porous layer and preventing the positive and negative active material particles from piercing the porous layer.

[0044] The inventors of the present application have found through in-depth research that the puncture strength P of the porous layer and the ratio M of the mass of the inorganic particles to the total mass of the porous layer satisfy the following relationship (1):

[0045] 9≤P / (M+1)≤150 Formula (1)

[0046] The unit of the puncture strength P is N / 20 μm.

[0047] In some embodiments of the present application, the nanofibers are oriented or randomly combined to form a porous matrix, and the random overlap between the nanofibers forms a large number of holes for ion transport, while the nanofibers themselves serve as a skeleton supporting the porous layer, and the inorganic particles are distributed in the porous matrix. By introducing a crosslinking agent and an initiator on the surface of the nanofibers and / or the surface of the inorganic particles, the nanofibers are combined together at the intersection by crosslinking to prevent the nanofibers from sliding each other. In addition, the nanofibers and the inorganic particles are combined together at the contact part by crosslinking to prevent the sliding between the inorganic particles and the nanofibers, thereby improving the strength of the porous layer. In the present application, the nanofibers are usually combined at the intersection, and there may also be a larger area of ​​combination between some fibers (for example, two nanofibers are partially combined in parallel); the combination between the inorganic particles and the nanofibers can be a point combination or a larger area combination. For example, when the nanofibers are overlapped on the inorganic particles, a line combination may be formed to further improve the strength of the porous layer and prevent the porous layer from being pierced by the positive and negative active material particles.

[0048] In some embodiments of the present application, the puncture strength P of the porous layer is ≥16, preferably ≥20

[0049] The introduction method of the crosslinking agent and the initiator of the present application is not particularly limited, as long as the present application can be achieved. For example, the crosslinking agent and the initiator can be introduced into the polymer solution for forming the nanofibers, or into the inorganic particle suspension, or into both the polymer solution for forming the nanofibers and the inorganic particle suspension.

[0050] The type of the cross-linking agent is not particularly limited, and can be any cross-linking agent known in the art. For example, the cross-linking agent can be selected from at least one of isocyanate, hexamethoxymethyl melamine, N-hydroxymethyl acrylamide, carbodiimide, trimethylolpropane, aziridine, diisopropylbenzene peroxide, butyl acrylate, N, N'-methylenebisacrylamide, 2,5-dimethyl-2,5-bis(tert-butyl peroxide)hexane, bisphenol A epoxy resin, acrylate derivatives, nitrile-containing polymers, styrene, vinyl fluoride, acrylonitrile, acrylic amine, vinyl acetate, alkyl vinyl ether, oxirane or oxetane derivatives. These cross-linking agents can be used alone or in combination of two or more.

[0051] The type of the initiator is not particularly limited, and can be any initiator known in the art. For example, the initiator can be selected from free radical polymerization initiators such as peroxides, azos, and redox types, and can specifically be benzoyl peroxide, tert-butyl benzoyl peroxide, methyl ethyl ketone peroxide, azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, and azobisisobutylamidine hydrochloride; it can also be selected from at least one of cationic polymerization initiators such as boron trifluoride, phosphorus pentafluoride, titanium tetrachloride, tin tetrachloride, and zinc dichloride. These initiators can be used alone or in combination of two or more.

[0052] The nanofiber is not particularly limited and can be any nanofiber known in the art. In one embodiment of the present application, the nanofiber is a polymer nanofiber. The polymer is not particularly limited as long as a porous layer of the present application can be formed. For example, the polymer is selected from polyvinylidene fluoride, polyimide, polyamide, polyacrylonitrile, polyethylene glycol, polyethylene oxide, polyphenylene oxide, polypropylene carbonate, polymethyl methacrylate, polyethylene terephthalate, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-chlorotrifluoroethylene and at least one thereof, preferably including polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyphenylene oxide, polypropylene carbonate, polyethylene oxide, etc. and at least one thereof. These polymers can be used alone or in combination of two or more.

[0053] The diameter of the nanofiber is not particularly limited as long as the purpose of the present application can be achieved. For example, the diameter of the nanofiber is 20 nm to 2 μm, preferably 50 nm to 1 μm, and more preferably 100 nm to 500 nm.

[0054] The cross-sectional shape of the nanofiber is not particularly limited and can be any shape. It is preferably in the shape of a flat ribbon, for example, the aspect ratio of the cross section of the nanofiber is 2 to 100, preferably 5 to 20; the aspect ratio is the ratio of the length values ​​of the widest part and the narrowest part of the cross section of the flat ribbon-shaped fiber. By making the cross section of the nanofiber into a flat ribbon, the contact area between the nanofibers and between the nanofibers and the inorganic particles can be further increased, thereby further increasing the bonding strength between the nanofibers and between the nanofibers and the inorganic particles, thereby further increasing the puncture strength of the porous layer, thereby increasing the ability of the porous layer to resist puncture by the positive and negative active material particles.

[0055] In a preferred embodiment of the present application, the nanofiber is a coaxial structure, which includes a first fiber as a core layer and a second fiber as a shell layer. The first fiber as the core layer mainly contains a polymer, and the second fiber as the shell layer on the surface of the core layer contains a crosslinking agent and an initiator. The diameter of the coaxial structure nanofiber is not particularly limited, as long as the purpose of the present application can be achieved. For example, it can be 20nm to 2μm, preferably 50nm to 1μm, and more preferably 100nm to 500nm. There is no special limitation on the ratio of the first fiber diameter to the second fiber outer diameter, for example, it can be 0.98 to 0.6, preferably 0.9 to 0.7. This ratio is within the above range, which can better achieve good bonding between nanofibers and good bonding between nanofibers and inorganic particles, and further improve the puncture resistance of the porous layer.

[0056] The present application does not limit the preparation method of the coaxial nanofibers, and the nanofibers may be prepared, for example, by the following method:

[0057] 1) dissolving a polymer in an organic solvent to obtain a polymer solution A;

[0058] 2) dispersing a crosslinking agent and an initiator in an organic solvent to obtain a solution B;

[0059] 3) using a coaxial spinning device, simultaneously injecting the above two solutions, wherein solution A is located in the core layer and solution B is located in the shell layer;

[0060] 4) The ejected coaxial fibers are nanofibers with a coaxial structure, and the nanofibers with a coaxial structure can be directly collected on the surface of the positive electrode sheet and / or the negative electrode sheet.

[0061] The inorganic particles are not particularly limited, and can be selected from, for example, HfO2, SrTiO3, SnO2, CeO2, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, boehmite, magnesium hydroxide, aluminum hydroxide, lithium phosphate, lithium titanium phosphate, lithium aluminum titanium phosphate, lithium lanthanum titanate, lithium germanium thiophosphate, lithium nitride, SiS2 glass, P2S5 glass, Li2O, LiF, LiOH, Li2CO3, LiAlO2, Li2O-Al2O3-SiO2-P2O5-TiO2-GeO2 ceramics or at least one of garnet ceramics. These inorganic particles can be used alone or in combination of two or more.

[0062] The average particle size of the inorganic particles is not particularly limited, for example, it can be 0.01 μm to 10 μm, preferably 20 nm to 5 μm. The ratio between the diameter of the nanofiber and the average particle size of the inorganic particles is not particularly limited, for example, it can be 1:2 to 1:200, preferably 1:3 to 1:20.

[0063] The number of inorganic particles in the porous layer can be 5×10 7 pcs / m 2 ~3×10 19 pcs / m 2 .

[0064] The mass of the inorganic particles in the porous layer can be 0.004 g / m 2 ~60g / m 2 .

[0065] The thickness of the porous layer is not particularly limited, and is preferably less than the thickness of the prior art separator. For example, the thickness of the porous layer of the present application may be 1 μm to 20 μm, preferably 5 μm to 10 μm. By making the thickness of the porous layer of the present application less than the thickness of the prior art separator, the energy density of the battery can be increased.

[0066] The porosity of the porous layer is not particularly limited, but is preferably 30% to 95% from the perspective of improving liquid retention. The air permeability of the porous layer according to the present application is not particularly limited, as long as it can achieve the purpose of the present application, for example, it can be 5s / 100cm 3 ~400s / 100cm 3 Without being limited to any theory, the inventors believe that controlling the air permeability within the above range can further improve the ion conductivity.

[0067] According to the present application, the average pore size of the porous layer is not particularly limited, and can be 20nm to 10μm. According to the present application, the pore size of the porous layer can be evenly distributed in the entire porous layer, or it can be distributed in the porous layer according to a certain rule. There is no special restriction in this regard, as long as the purpose of the present application can be achieved. For example, in a preferred embodiment of the present application, the pore size of the porous layer decreases linearly in the thickness direction from away from the electrode pole piece to close to the electrode pole piece. In another preferred embodiment of the present application, the pore size of the porous layer decreases nonlinearly in the thickness direction from away from the electrode pole piece to close to the electrode pole piece. In another embodiment of the present application, the pore size of the porous layer decreases discontinuously in the thickness direction from away from the electrode pole piece to close to the electrode pole piece, that is, it changes in layers. The number of layers is not particularly limited. From the perspective of the preparation process, it can be 2 to 10 layers, preferably 2 to 5 layers.

[0068] In some embodiments of the present application, Figure 3As shown, one or more inorganic material layers 3 may be covered between fiber layers of different pore sizes within the porous layer 2 and above the outer surface to further improve the mechanical strength and ensure insulation performance. The inorganic material layer has a certain mechanical strength and the ability to conduct electrons. Preferably, the inorganic material has the ability to conduct lithium ions. The thickness of the inorganic material layer 3 is 0.1μm to 20μm. If it is too thin, it will not improve the mechanical strength and inhibit particle penetration and lithium dendrite growth. If it is too thick, it will inhibit lithium ion conduction, increase battery polarization, and inhibit performance. The porosity of the inorganic material layer is 10% to 40%, and the average pore size is 0.1μm to 1μm. Generally, the electronic resistivity of the inorganic material layer is >10 7 Ωm, preferably, electronic resistivity>10 10 Ωm, the ionic conductivity range of the inorganic material layer is required to be 10 -2 S / cm~10 -8 S / cm.

[0069] There is no particular limitation on the bonding between the inorganic material layer 3 and the porous layer 2. For example, the bonding can be performed in the following manner:

[0070] 1. Hot pressing and / or bonding can be used. In the hot pressing method, the hot pressing temperature should be the minimum value of the melting points of the inorganic material layer and the porous layer, and the pressure should be between 0.1MPa and 1MPa. In the bonding method, there is no special restriction on the adhesive, for example, one or more of polyamide, polyurethane, ethylene-vinyl acetate copolymer (EVA), ethylene-vinyl alcohol copolymer (EVOH), acrylate, and polyvinylidene fluoride can be selected.

[0071] 2. If the inorganic material layer 3 is directly deposited or coated on the porous layer 2, a binder is not necessarily required, and the bonding can be formed naturally.

[0072] The type of lithium-ion battery according to the present application is not limited, and it can be any type of lithium-ion battery, such as button-type, cylindrical, soft-pack lithium-ion battery, etc. The lithium-ion battery according to the present application includes a positive electrode, a negative electrode, an electrolyte, and a porous layer according to the present application. In one embodiment of the present application, the porous layer can be formed on one surface of the positive electrode sheet and one surface of the negative electrode sheet, and then stacked in the manner of negative electrode sheet + porous layer, positive electrode sheet + porous layer to form a lithium-ion battery stack. In another embodiment of the present application, the porous layer can be formed on both surfaces of the positive electrode sheet, and then stacked in the manner of negative electrode sheet, porous layer + positive electrode sheet + porous layer to form a lithium-ion battery stack, wherein there is no porous layer on the surface of the negative electrode sheet. In another embodiment of the present application, the porous layer can be formed on both surfaces of the negative electrode sheet, and then stacked in the manner of porous layer + negative electrode sheet + porous layer, positive electrode sheet to form a lithium-ion battery stack. The stacked body formed in the above embodiment can be further stacked in the above order, or can be directly wound to form a multi-layer lithium ion battery stacked body. The present application has no limitation on the stacking method, and those skilled in the art can choose according to actual conditions.

[0073] In the embodiments of the present application, there is no particular limitation on the positive electrode sheet, as long as the purpose of the present application can be achieved. For example, the positive electrode sheet generally comprises a positive electrode collector and a positive electrode active material layer, and the positive electrode active material layer comprises a positive electrode active material. Among them, the positive electrode collector is not particularly limited, and can be any positive electrode collector known in the art, such as copper foil, aluminum foil, aluminum alloy foil, and composite collector. The positive electrode active material is not particularly limited, and can be any positive electrode active material of the prior art, for example, the positive electrode active material is selected from at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, or lithium iron manganese phosphate.

[0074] Optionally, the positive electrode sheet may further include a conductive layer, the conductive layer being located between the positive electrode current collector and the positive electrode active material layer. The composition of the conductive layer is not particularly limited, and may be a conductive layer commonly used in the art.

[0075] In the embodiments of the present application, the negative electrode plate is not particularly limited, as long as the purpose of the present application can be achieved. For example, the negative electrode plate generally comprises a negative electrode collector and a negative electrode active material layer, and the negative electrode active material layer comprises a negative electrode active material. Among them, the negative electrode collector is not particularly limited, and any negative electrode collector known in the art can be used, such as copper foil, aluminum foil, aluminum alloy foil, and composite collector. The negative electrode active material is not particularly limited, and any negative electrode active material known in the art can be used. For example, it can include at least one of artificial graphite, natural graphite, mesophase carbon microspheres, silicon, silicon carbon, silicon oxides, soft carbon, hard carbon, lithium titanate, or niobium titanate.

[0076] The electrolyte of the lithium-ion battery is not particularly limited, and any electrolyte known in the art can be used, which can be any of a gel state, a solid state and a liquid state. For example, the liquid electrolyte includes a lithium salt and a non-aqueous solvent.

[0077] The lithium salt is not particularly limited, and any lithium salt known in the art can be used as long as the purpose of the present application can be achieved. For example, the lithium salt can be selected from at least one of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3 or LiPO2F2. For example, the lithium salt can be selected from LiPF6.

[0078] The non-aqueous solvent is not particularly limited as long as the purpose of the present application can be achieved. For example, the non-aqueous solvent can be selected from at least one of carbonate compounds, carboxylate compounds, ether compounds, nitrile compounds, and other organic solvents.

[0079] For example, the carbonate compound can be selected from at least one of diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), ethyl methyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinyl ethylene carbonate (VEC), 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-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, and trifluoromethylethylene carbonate.

[0080] The method for depositing the nanofibers and the inorganic particles is not particularly limited, and can be carried out by a deposition method known in the art, for example, the porous matrix is ​​prepared by electrospinning, air spinning or centrifugal spinning, and the inorganic particles are prepared by electrospraying. The order of depositing the nanofibers and the inorganic particles is not particularly limited, as long as a porous layer of the present application can be formed, the porous layer comprising a nanofiber porous matrix and inorganic particles distributed in the porous matrix. For example, the nanofibers and the inorganic particles can be deposited simultaneously.

[0081] The porous matrix can be made with any spinning equipment known in the art without any particular limitation, as long as the purpose of the present application can be achieved, and any spinning equipment known in the art or commercially available can be used.

[0082] Electrospraying, also known as electrostatic spraying, is a process of electrostatic spraying of particles. The spray device is filled with particle suspension. Under the action of an external electric field, the suspension droplets are held at the nozzle by surface tension. Under the induction of the electric field, the surface accumulates charges and is subjected to an electric field force in the opposite direction of the surface tension. The suspension droplets at the nozzle leave the nozzle and move toward the deposition target under the action of the electric field and are deposited on the target.

[0083] The electrospraying can be carried out by any equipment known in the art, without any particular limitation, as long as the purpose of the present application can be achieved. For example, any equipment known to those skilled in the art or commercially available can be used for the electrospraying.

[0084] Another aspect of the present application provides an electronic device, which includes the electrochemical device according to the present application.

[0085] definition:

[0086] The number of inorganic particles: the number of inorganic particles per unit area of ​​the porous layer.

[0087] Average particle size of inorganic particles: A laser particle size tester is used to test and obtain the particle size distribution curve of the inorganic particles. In the volume distribution curve of the inorganic particles, the particle size corresponding to 50% of the cumulative volume starting from the small particle size side is the average particle size of the inorganic particles.

[0088] Test method:

[0089] Lithium-ion battery self-discharge rate K:

[0090] The lithium-ion battery was discharged at a current of 0.5C to 3.0V, and then left to stand for 5 minutes. Then, the lithium-ion battery was charged at a constant current of 0.5C to 3.85V, and then charged at a constant voltage of 3.85V to a current of 0.05C, and left to stand for two days in an environment of 25℃±3℃, and the voltage OCV1 at this time was tested and recorded. Then, the lithium-ion battery was left to stand for two days in an environment of 25℃±3℃, and the voltage OCV2 at this time was tested and recorded, and the K value was obtained by the following formula: K (mV / h) = (OCV2-OCV1) / 48h×1000.

[0091] Porosity of porous layer:

[0092] The lithium-ion battery is disassembled after being discharged to obtain an electrode plate with a porous layer on the surface. A portion of the porous layer sample is cut out and the porosity of the porous layer is tested by a conventional mercury injection method.

[0093] Capacity retention rate:

[0094] Charge the lithium-ion battery to 4.4V at a constant current of 0.5C, then charge it to a current of 0.05C at a constant voltage of 4.4V, let it stand for 10 minutes in an environment of 25℃±3℃, then discharge it to 3.0V at a current of 0.5C, record the first discharge capacity as Q1, repeat this cycle 50 times, and record the discharge capacity at this time as Q 50 The capacity retention rate η after 50 cycles is obtained by the following formula: η=Q 50 / Q1×100%.

[0095] Puncture strength of porous layer:

[0096] A microcomputer-controlled electronic universal testing machine (MTS-E44.104) was used to test the puncture strength of the porous layer.

[0097] Testing process:

[0098] Disassemble the lithium-ion battery, take a laminated sample with a three-layer structure of a positive electrode sheet, a porous layer and a negative electrode sheet, bake it at 80°C for 2 hours, and place it on an aluminum plate on one side of a press; place a steel ball (iron, 5mm in diameter) on top of the sample; apply a 10V voltage between the tabs of the two electrodes, and apply pressure to the sample surface through the aluminum plates on both sides. The vertical pressure speed is 0.1mm / min, and the pressure when the resistance changes sharply is recorded, which is the puncture strength.

[0099] Example

[0100] Preparation Example 1: Preparation of negative electrode sheet

[0101] The negative electrode active materials artificial graphite, conductive carbon black (Super P), and styrene-butadiene rubber are mixed in a weight ratio of 96:1.5:2.5, deionized water is added as a solvent, and stirred evenly. The slurry is evenly coated on one surface of a negative electrode collector copper foil with a thickness of 10 μm, and dried at 110°C to obtain a negative electrode sheet with a coating thickness of 150 μm and coated on one side with a negative electrode active material layer. Repeat the above steps on the other surface of the negative electrode sheet to obtain a negative electrode sheet with a negative electrode active material layer coated on both sides. Then, the negative electrode sheet is cut into a specification of 41 mm × 61 mm for standby use.

[0102] Preparation Example 2: Preparation of positive electrode sheet

[0103] The positive electrode active material lithium cobalt oxide, conductive carbon black (Super P), and polyvinylidene fluoride are mixed in a weight ratio of 97.5:1.0:1.5, N-methylpyrrolidone is added as a solvent, and stirred evenly. The slurry is evenly coated on one surface of the positive electrode collector aluminum foil, and dried at 90°C to obtain a positive electrode sheet with a positive electrode active material layer thickness of 100μm. On the other surface of the positive electrode collector aluminum foil, the above steps are repeated to obtain a positive electrode sheet coated with a positive electrode active material layer on both sides. Then, the positive electrode sheet is cut into a specification of 38mm×58mm for standby use.

[0104] Preparation Example 3: Preparation of electrolyte

[0105] In a dry argon atmosphere, organic solvents ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are first mixed in a mass ratio of EC:EMC:DEC=30:50:20, and then lithium salt lithium hexafluorophosphate (LiPF6) is added to the organic solvent to dissolve and mix evenly to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L.

[0106] The following examples illustrate the preparation of the nanofiber porous matrix + inorganic particle integrated porous layer according to the present application. These embodiments are described by taking the positive electrode sheet as an example, and the integrated porous layer is deposited on both surfaces of the positive electrode sheet. It should be understood that the integrated porous layer can also be deposited on both surfaces of the negative electrode sheet, or the integrated porous layer can be deposited on one surface of the positive electrode sheet and one surface of the negative electrode sheet, respectively, and these embodiments can also achieve the purpose of the present application. Those skilled in the art should understand that these embodiments are also within the scope of protection of the present application.

[0107] Embodiment 1:

[0108] 99.9 parts by weight of polyvinylidene fluoride (PVDF), 0.09 parts by weight of acrylonitrile as a crosslinking agent and 0.01 parts by weight of boron trifluoride as an initiator were dispersed in a dimethylformamide / acetone (7:3) solvent, i.e., a small amount of crosslinking agent and initiator were added to a conventional electrospinning solution, and stirred evenly until the slurry viscosity was stable, to obtain a solution A with a mass fraction of 25%. At the same time, 99.9 parts by weight of boehmite, 0.09 parts by weight of acrylonitrile and 0.01 parts by weight of boron trifluoride were dispersed in a dimethylformamide / acetone (7:3) solvent, and stirred evenly until the slurry viscosity was stable, to obtain a suspension B with a mass fraction of 40%.

[0109] On the surface of the positive electrode of Preparation Example 2, solution A is used as a raw material to prepare polyvinylidene fluoride nanofibers by electrospinning, and the average diameter of the nanofibers is 100nm. While spinning, suspension B is used as a raw material, and inorganic particles are simultaneously prepared on the surface of the positive electrode by electrospraying. The average particle size of the selected inorganic particles is 500nm, and the ratio of the average diameter of the nanofibers to the average particle size of the inorganic particles is 1:5. The thickness of the porous layer is 10μm, the average pore size of the porous layer is 200nm, and the porosity of the porous layer is 75%. Then, the above steps are repeated on the other surface of the positive electrode, and the solvents such as dimethylformamide are removed by vacuum drying at 40°C, and then the temperature is increased to 80°C for heat treatment for 6h, and cross-linking is performed to obtain a positive electrode with a double-sided porous layer. In the porous layer finally prepared, the mass fraction of polymer nanofibers is: 95%, the mass fraction of inorganic particles is: 4.9%, and the mass fraction of cross-linking agent and initiator is: 0.1%.

[0110] Embodiment 2-5

[0111] Except for adjusting the mass fraction of nanofibers and the mass fraction of inorganic particles in the porous layer as shown in Table 1, the rest is the same as Example 1, wherein the micrograph of the porous layer of Example 2 is as follows: Figure 5 shown.

[0112] Example 6

[0113] 99 parts by weight of polyvinylidene fluoride, 0.9 parts by weight of acrylonitrile and 0.1 parts by weight of boron trifluoride were dispersed in a dimethylformamide / acetone (7:3) solvent, and stirred evenly until the slurry viscosity was stable, to obtain a 25% solution A. At the same time, 99 parts by weight of boehmite, 0.9 parts by weight of acrylonitrile and 0.1 parts by weight of boron trifluoride were dispersed in a dimethylformamide / acetone (7:3) solvent, and stirred evenly until the slurry viscosity was stable, to obtain a 40% suspension B.

[0114] Solution A and suspension B were used as raw materials to prepare a positive electrode sheet coated with a porous layer on both sides in the same manner as in Example 1. In the porous layer finally prepared, the mass fraction of nanofibers was 69%, the mass fraction of inorganic particles was 30%, and the mass fraction of crosslinking agent and initiator was 1%.

[0115] The rest is the same as Example 1.

[0116] Example 7

[0117] 95 parts by weight of polyvinylidene fluoride, 4.5 parts by weight of acrylonitrile and 0.5 parts by weight of boron trifluoride were dispersed in a dimethylformamide / acetone (7:3) solvent, and stirred evenly until the slurry viscosity was stable to obtain a solution A with a mass fraction of 25%. At the same time, 95 parts by weight of boehmite, 4.5 parts by weight of acrylonitrile and 0.5 parts by weight of boron trifluoride were dispersed in a dimethylformamide / acetone (7:3) solvent, and stirred evenly until the slurry viscosity was stable to obtain a suspension B with a mass fraction of 40%.

[0118] Solution A and suspension B were used as raw materials to prepare a positive electrode sheet coated with a porous layer on both sides in the same manner as in Example 1. In the porous layer finally prepared, the mass fraction of nanofibers was 65%, the mass fraction of inorganic particles was 30%, and the mass fraction of crosslinking agent and initiator was 5%.

[0119] The rest is the same as Example 1.

[0120] Example 8

[0121] 93 parts by weight of polyvinylidene fluoride, 6.3 parts by weight of acrylonitrile and 0.7 parts by weight of boron trifluoride were dispersed in a dimethylformamide / acetone (7:3) solvent, and stirred evenly until the slurry viscosity was stable to obtain a solution A with a mass fraction of 25%. At the same time, 93 parts by weight of boehmite, 6.3 parts by weight of acrylonitrile and 0.7 parts by weight of boron trifluoride were dispersed in a dimethylformamide / acetone (7:3) solvent, and stirred evenly until the slurry viscosity was stable to obtain a suspension B with a mass fraction of 40%.

[0122] Solution A and suspension B were used as raw materials to prepare a positive electrode sheet coated with a porous layer on both sides in the same manner as in Example 1. In the porous layer finally prepared, the mass fraction of nanofibers was 63%, the mass fraction of inorganic particles was 30%, and the mass fraction of crosslinking agent and initiator was 7%.

[0123] The rest is the same as Example 1.

[0124] Example 9

[0125] The process is the same as Example 7 except that the polyvinylidene fluoride in solution A is replaced by polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP).

[0126] Example 10

[0127] Except that the boehmite in the turbid solution B is replaced by ZrO2, the rest is the same as Example 7.

[0128] Embodiment 11

[0129] Except that the crosslinking agent in solution A is triethylene glycol diacrylate and the initiator is lauroyl peroxide, the rest is the same as Example 7.

[0130] Example 12

[0131] The process was the same as Example 7 except that the average particle size of the inorganic particles was adjusted to 200 nm.

[0132] Example 13

[0133] The process is the same as Example 7 except that the average particle size of the inorganic particles is adjusted to 1000 nm.

[0134] Embodiment 14

[0135] Except for adjusting the average diameter of nanofibers to 50 nm and the average particle size of inorganic particles to 10000 nm according to Table 1, the rest is the same as Example 12.

[0136] Embodiment 15

[0137] Except that the average pore size of the porous layer close to the positive electrode plate is 200nm, the average pore size of the porous layer far from the positive electrode plate is 1000nm, and the average pore size of the porous layer in the middle area increases linearly with the distance from the electrode surface, forming a gradient change in the average pore size of the porous layer, the rest is the same as Example 13.

[0138] Example 16

[0139] The same as Example 13 except that a flat nozzle is selected as the electrospinning nozzle to obtain flat ribbon-type nanofibers with a long side diameter of 100 nm and an aspect ratio of 20; and a ratio of the long side diameter of the nanofiber cross section to the average particle size of the inorganic particles of 1:10.

[0140] Embodiment 17

[0141] PVDF was dispersed in a dimethylformamide / acetone (7:3) solvent and stirred evenly until the slurry viscosity was stable to obtain a solution A with a mass fraction of 25%. 95 parts by weight of boehmite, 4.5 parts by weight of acrylonitrile and 0.5 parts by weight of boron trifluoride were dispersed in a dimethylformamide / acetone (7:3) solvent and stirred evenly until the slurry viscosity was stable to obtain a suspension B with a mass fraction of 40%. 90 parts by weight of acrylonitrile and 10 parts by weight of boron trifluoride were dispersed in a dimethylformamide / acetone (7:3) solvent and stirred evenly until the slurry was stable to obtain a solution C with a mass fraction of 25%.

[0142] On the surface of the positive electrode plate of Preparation Example 2, solution A and solution C are used as raw materials to prepare a coaxial structured PVDF / (acrylonitrile + boron trifluoride) nanofiber matrix by electrospinning. The electrospinning nozzle is selected as a sleeve-type nozzle, in which the inner tube passes through solution A, and solution C passes between the inner tube and the outer tube. After electrospinning, a coaxial structured nanofiber with a core layer of PVDF fiber and a shell layer of crosslinking agent + initiator is obtained. The average diameter of the nanofiber is 100nm, and the ratio of the core fiber diameter to the outer diameter of the shell fiber is 0.6. While spinning, suspension B is used as a raw material, and inorganic particles are simultaneously prepared on the surface of the positive electrode plate by electrospraying. The average particle size of the selected inorganic particles is 1000nm, and the ratio of the average diameter of the nanofiber to the average particle size of the inorganic particles is 1:10. The thickness of the porous layer is 10μm, the average pore size of the porous layer is 200nm, and the porosity of the porous layer is 75%. Then, repeat the above steps on the other side of the positive electrode sheet, and vacuum dry at 40°C to remove dispersants such as dimethylformamide, then heat treat at 80°C for 6 hours for cross-linking to obtain a positive electrode sheet with a double-sided porous layer. In the porous layer finally prepared, the mass fraction of nanofibers is 30%, the mass fraction of inorganic particles is 30%, and the mass fraction of cross-linking agent and initiator is 40%.

[0143] Embodiment 18

[0144] The throughput of solution A and solution C in the electrospinning parameters was changed so that in the finally prepared porous layer, the mass fraction of nanofibers was 55%, the mass fraction of cross-linker and initiator was 15%, and the ratio of the core fiber diameter to the outer diameter of the shell fiber was adjusted to 0.85. The rest was the same as Example 17.

[0145] Embodiment 19

[0146] The throughput of solution A and solution C in the electrospinning parameters was changed so that in the finally prepared porous layer, the mass fraction of nanofibers was 67%, the mass fraction of cross-linker and initiator was 3%, and the ratio of the core fiber diameter to the outer diameter of the shell fiber was adjusted to 0.98. The rest was the same as in Example 17.

[0147] Embodiment 20

[0148] The process was the same as Example 13 except that the average particle size of the inorganic particles was adjusted to 5000 nm.

[0149] Embodiment 21

[0150] The process is the same as Example 13 except that the average pore size of the porous layer is adjusted to 800 nm.

[0151] Embodiment 22

[0152] The process was the same as Example 13 except that the thickness of the porous layer was adjusted to 5 μm.

[0153] Embodiment 23

[0154] The process is the same as Example 13 except that the porosity of the porous layer is adjusted to 90%.

[0155] Embodiment 24

[0156] Conductive carbon black (Super P) and styrene-butadiene rubber (SBR) were mixed at a weight ratio of 97:3, and deionized water (H2O) was added as a solvent to prepare a slurry with a solid content of 0.85, and stirred evenly. The slurry was evenly coated on the positive electrode collector aluminum foil and dried at 110°C to obtain a positive electrode conductive layer with a thickness of 2 μm.

[0157] The positive electrode active material lithium cobalt oxide (LiCoO2), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) are mixed in a weight ratio of 97.5:1.0:1.5, and N-methylpyrrolidone (NMP) is added as a solvent to prepare a slurry with a solid content of 0.75, and stirred evenly. The slurry is evenly coated on the above-mentioned positive electrode conductive layer of the positive electrode collector aluminum foil with a thickness of 10μm, and dried at 90°C to obtain a positive electrode sheet with a conductive layer thickness of 2μm. On the other surface of the positive electrode collector aluminum foil, repeat the above steps to obtain a positive electrode sheet coated with a conductive layer and a positive electrode active material layer on both sides. Then, the positive electrode sheet is cut into a specification of 38mm×58mm for standby use.

[0158] On the surface of the positive electrode sheet, the steps of Example 13 are repeated to obtain a positive electrode sheet with a positive electrode conductive layer.

[0159] Embodiment 25

[0160] Prepare a positive electrode sheet according to the steps of Example 13;

[0161] Inorganic ceramic particles of aluminum oxide (Al2O3) and polyvinylidene fluoride (PVDF) were mixed at a weight ratio of 95:5, and N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 0.8, and stirred evenly. The slurry was evenly coated on the porous layer on one side of the positive electrode plate prepared above, and dried at 90°C to obtain an inorganic material layer. The inorganic material layer had a thickness of 3μm, a porosity of 30%, and an average pore size of 0.8μm.

[0162] Repeat the same steps on the other surface of the positive electrode plate to obtain a positive electrode plate with inorganic material layers coated on both sides.

[0163] Embodiment 26

[0164] Except that the turbid liquid B does not contain the crosslinking agent and the initiator, the rest is the same as Example 1.

[0165] Preparation of lithium-ion batteries

[0166] The negative electrode sheet prepared in the above Preparation Example 1 and the positive electrode sheet with a porous layer obtained in each embodiment are stacked opposite to each other. Figure 2 After the four corners of the entire laminate structure are fixed with tape, it is placed in an aluminum-plastic film, sealed on the top and sides, injected with the electrolyte in Preparation Example 3, and then packaged to obtain a lithium-ion laminated battery.

[0167] Comparative Example 1

[0168] A polyethylene film with a thickness of 10 μm was selected as a separator and placed between the positive electrode sheet and the negative electrode sheet prepared in Preparation Example 1 and Preparation Example 2 as a separator. The negative electrode sheet, the positive electrode sheet and the separator were stacked opposite to each other. After the four corners of the entire laminate structure were fixed with tape, it was placed in an aluminum-plastic film, top and side sealed, the electrolyte in Preparation Example 3 was injected, and packaging was performed to obtain a lithium-ion laminated battery.

[0169] Comparative Example 2

[0170] 99.9 parts by weight of PVDF, 0.09 parts by weight of acrylonitrile and 0.01 parts by weight of boron trifluoride were dispersed in a DMF / acetone (7:3) solvent and stirred evenly until the slurry viscosity was stable to obtain a solution A with a mass fraction of 25%.

[0171] On the surface of the positive electrode obtained in Preparation Example 2, a PVDF fiber layer with a thickness of 10 μm was prepared by electrospinning using Solution A as a raw material. The average fiber diameter was 100 nm, the average pore size of the fiber layer was 400 nm, and the porosity was 75%. The above steps were repeated on the other surface of the positive electrode, and vacuum dried at 40°C to remove dispersants such as DMF. The temperature was then raised to 80°C for heat treatment for 6 hours to complete the cross-linking process, and a positive electrode with a porous layer on both sides was obtained. In the obtained porous layer, the mass fraction of the polymer fiber is 99.9%, the mass fraction of the cross-linking agent and the initiator is 0.1%, and the micrograph of the fiber layer of Comparative Example 2 is shown in FIG. Figure 4 shown.

[0172] The positive electrode sheet is placed opposite to the negative electrode sheet prepared in Preparation Example 1 and stacked. Figure 2 After the four corners of the entire laminate structure are fixed with tape, it is placed in an aluminum-plastic film, top and side sealed, the electrolyte in Preparation Example 3 is injected, and packaging is performed to obtain a lithium-ion laminated battery.

[0173] The data and test results of each embodiment and comparative example are shown in Table 1.

[0174]

[0175]

[0176]

[0177] As can be seen from Table 1, the introduction of inorganic particles into the nanofiber porous matrix significantly improves the puncture resistance of the porous layer; the self-discharge rate is significantly reduced, and the cycle characteristics of the lithium-ion battery are improved. Without being limited to any theory, the inventors believe that the introduction of inorganic particles improves the strength of the porous layer and blocks the "macropores" that may exist in the nanofiber porous matrix, thereby improving the puncture resistance of the porous layer, reducing the self-discharge rate, and improving the cycle characteristics of the lithium-ion battery. Due to the introduction of the cross-linking agent, the bonding strength between the nanofibers and between the nanofibers and the inorganic particles is further improved, the puncture resistance of the porous layer is further improved, the self-discharge rate is reduced, and the cycle characteristics of the lithium-ion battery are improved.

[0178] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. An electrochemical device, comprising an electrode plate and a porous layer formed on the surface of the electrode plate, wherein the porous layer comprises nanofibers and inorganic particles, and the nanofibers and the inorganic particles are bonded by a crosslinking agent; The porous layer also includes an initiator. Calculated by the mass percentage of the porous layer, the content of the nanofibers is 4.9% to 95%, the content of the inorganic particles is 4.9% to 95%, the content of the crosslinking agent and the initiator is 5% to 15%, wherein the initiator accounts for 5% to 20% of the total mass of the crosslinking agent and the initiator; The ratio between the diameter of the nanofibers and the average particle size of the inorganic particles is 1:5 to 1:50; The puncture strength P of the porous layer and the ratio M of the mass of the inorganic particles to the total mass of the porous layer satisfy the following relationship (1): 9≤P / (M+1)≤150 Formula (1) in, The unit of the puncture strength P is N / 20µm.

2. The electrochemical device according to claim 1, wherein P ≥ 16. The electrochemical device according to claim 2 , wherein P≧20.

4. The electrochemical device according to claim 1, in, The crosslinking agent includes at least one of polyisocyanate, hexamethoxymethyl melamine, N-hydroxymethyl acrylamide, carbodiimide, trimethylolpropane, aziridine, diisopropylbenzene peroxide, butyl acrylate, N,N'-methylenebisacrylamide, 2,5-dimethyl-2,5-bis(tert-butyl peroxide)hexane, bisphenol A epoxy resin, acrylate derivatives, nitrile-containing polymers, styrene, vinyl fluoride, acrylonitrile, acrylic amine, vinyl acetate, alkyl vinyl ether, alkylene oxide or oxetane derivatives.

5. The electrochemical device according to claim 1, in, The initiator is selected from at least one of benzoyl peroxide, tert-butyl benzoyl peroxide, methyl ethyl ketone peroxide, azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, azobisisobutylamidine hydrochloride, boron trifluoride, phosphorus pentafluoride, titanium tetrachloride, tin tetrachloride or zinc dichloride.

6. The electrochemical device according to claim 1, in, The nanofibers include flat ribbon-shaped fibers, and the ratio of the length values ​​of the widest part to the narrowest part of the cross section of the flat ribbon-shaped fibers is between 2 and 100.

7. The electrochemical device according to claim 6, in, The ratio of the length values ​​of the widest part and the narrowest part of the cross section of the flat ribbon-shaped fiber is between 2 and 20.

8. The electrochemical device according to claim 1, in, The nanofibers include at least one of polyvinylidene fluoride, polyimide, polyamide, polyacrylonitrile, polyethylene glycol, polyethylene oxide, polyphenylene ether, polypropylene carbonate, polymethyl methacrylate, polyethylene terephthalate, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-chlorotrifluoroethylene and derivatives thereof.

9. The electrochemical device according to claim 1, in, The porous layer has at least one of the following characteristics: (a) The air permeability of the porous layer is 5 s / 100 cm 3 ~400s / 100cm 3 ; (b) the porosity of the porous layer is 30% to 95%; (c) the average pore size of the porous layer is 20 nm to 10 μm; (d) the thickness of the porous layer is 1 μm to 20 μm; (e) the pore size of the porous layer decreases linearly along the thickness direction from far away from the electrode plate to close to the electrode plate; (f) the pore size of the porous layer decreases nonlinearly along the thickness direction from far away from the electrode plate to close to the electrode plate; (g) The pore size of the porous layer decreases discontinuously along the thickness direction from far away from the electrode pad to close to the electrode pad.

10. The electrochemical device according to claim 1, in, The number of the inorganic particles in the porous layer per unit area is 5×10 7 pcs / m 2 ~3×10 19 pcs / m 2 .

11. The electrochemical device according to claim 1, in, The mass of the inorganic particles in the porous layer per unit area is 0.004 g / m 2 ~60 g / m 2 .

12. The electrochemical device according to claim 1, in, The average particle size of the inorganic particles is 0.01 μm to 10 μm.

13. The electrochemical device according to claim 1, in, The inorganic particles are selected from any one or a mixture of at least two of the following: HfO 2 、SrTiO 3 SnO 2 、CeO 2 , MgO, NiO, CaO, BaO, ZnO, ZrO 2 , Y 2 O 3 、Al 2 O 3 、TiO 2 、SiO 2 , boehmite, magnesium hydroxide, aluminum hydroxide, lithium phosphate, lithium titanium phosphate, lithium aluminum titanium phosphate, lithium lanthanum titanate, lithium germanium thiophosphate, lithium nitride, SiS 2 Glass, P 2 S 5 Glass, Li 2 O, LiF, LiOH, Li 2 CO 3 、LiAlO 2 , Li 2 O-Al 2 O 3 -SiO 2 -P 2 O 5 -TiO 2 -GeO 2 Ceramics and garnet ceramics.

14. The electrochemical device according to claim 1, in, The porous layer is prepared by electrospinning, air spinning or centrifugal spinning.

15. The electrochemical device according to claim 1, in, The nanofiber includes a core layer and a shell layer, and the crosslinking agent and the initiator are contained in the shell layer.

16. An electronic device comprising the electrochemical device according to any one of claims 1 to 15.

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