CN113540699A - Electrochemical device and electronic device - Google Patents

Electrochemical device and electronic device Download PDF

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CN113540699A
CN113540699A CN202110818487.4A CN202110818487A CN113540699A CN 113540699 A CN113540699 A CN 113540699A CN 202110818487 A CN202110818487 A CN 202110818487A CN 113540699 A CN113540699 A CN 113540699A
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oxide
lithium
electrochemical device
fiber
layer
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曾志鹏
张益博
魏红梅
翁秋燕
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Ningde Amperex Technology Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/46—Separators, membranes or diaphragms characterised by their combination with electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/431—Inorganic material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/44—Fibrous material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/443—Particulate material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/446—Composite material consisting of a mixture of organic and inorganic materials
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • Composite Materials (AREA)
  • Manufacturing & Machinery (AREA)
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Abstract

The application provides an electrochemical device and electronic device, including electrode plate, electrode plate includes the mass flow body and active substance layer, wherein, has the fibre isolation layer on at least one surface of electrode plate, and including polymer fibre, polymer fibre in the fibre isolation layerTortuosity τ of dimension0Comprises the following steps: 1.2<τ0<1.9. The fibrous separator layer of the present application improves the self-discharge problem of electrochemical devices, thereby improving the performance of the electrochemical devices.

Description

Electrochemical device and electronic device
Technical Field
The present disclosure relates to electrochemical technologies, and particularly to an electrochemical device and an electronic device.
Background
The lithium ion battery has the characteristics of large specific energy, high working voltage, low self-discharge rate, small volume, light weight and the like, and is widely applied to various fields of electric energy storage, portable electronic equipment, electric automobiles and the like. With the rapid development of electric vehicles and mobile electronic devices, people have increasingly high performance requirements, such as high energy density requirements, for lithium ion batteries.
By directly preparing the isolating layer on the surface of the pole piece by adopting an electrostatic spinning technology, the thickness of the isolating layer can be reduced, and thus the energy density of the lithium ion battery is improved. However, the existing isolation layer is affected by the fiber structure, and the size uniformity of the pores in the isolation layer is poor, so that the lithium ion battery has a serious self-discharge problem, and the performance of the lithium ion battery is affected.
Disclosure of Invention
The present application is directed to an electrochemical device and an electronic device to improve the self-discharge problem of a lithium ion battery.
In the following description of the present application, the present application is explained by taking a lithium ion battery as an example of an electrochemical device, but the electrochemical device of the present application is not limited to a lithium ion battery.
A first aspect of the present application provides an electrochemical device comprising an electrode sheet comprising a current collector and an active substance layer, wherein a fiber isolation layer is provided on at least one surface of the electrode sheet, the fiber isolation layer comprises polymer fibers, and the tortuosity τ 0 of the polymer fibers is: 1.2<τ0<1.9, preferably 1.3<τ0<1.5。
The inventors have discovered that fibrous insulation layers are typically formed by the oriented or random bonding together of nano-to micron-sized polymer fibers,the random bridging between fibers forms a large number of pores for ion transport, but the pores in the current fibrous isolation layer have large pore sizes and are not uniformly distributed, and the existence of partial "macropores" (for example, pores with the pore size larger than 1 μm) can cause lithium ions to have more serious self-discharge problems. If the pore size in the fibrous separator is simply reduced, lithium ion transport is impeded, thereby affecting the dynamic performance of the lithium ion battery. In view of the above, the present application is directed to controlling the tortuosity τ of a polymer fiber0Comprises the following steps: 1.2<τ0<1.9, can improve the homogeneous degree in the hole in the fibre isolation layer, thereby can improve lithium ion battery self discharge problem and improve the security, guarantee simultaneously that ionic transmission lasts unobstructed, improve lithium ion battery's multiplying power performance.
In this application, having the fiber isolation layer on at least one surface of electrode sheet can mean that one surface of electrode sheet can have the fiber isolation layer, or have the fiber isolation layer simultaneously on two surfaces of electrode sheet. Tortuosity τ of Polymer fibers of the present application0Can mean that: the actual straightened length (L) of the polymer fibers and the crimped length (L) of the polymer fibers0) The ratio of (a) to (b), namely: tau is0＝L/L0. The electrode piece of the present application may refer to a positive electrode piece or a negative electrode piece.
In some embodiments of the present application, the degree of tortuosity τ of the fibrous insulation layer1Comprises the following steps: 1.2<τ1<1.8, preferably 1.3<τ1<1.7. By controlling the tortuosity tau of the fibrous insulation layer1Within the above range, the uniformity of the pores in the fibrous separation layer can be further improved. The tortuosity of the fibrous insulation layer of the present application can be determined by the following expression:
Figure BDA0003171119420000021
wherein
Figure BDA0003171119420000022
Epsilon is the porosity, rho, of the fibrous insulationsIs the resistivity of the fibrous insulation layer, peIs the electrolyte resistivity.
In some embodiments of the present application, the pores in the fibrous insulation layer have an average pore diameter of 20nm to 1 μm, preferably 100nm to 500 nm. Without being bound by any theory, too small an average pore size (e.g., less than 20nm) of the pores in the fibrous separator layer can result in insufficient ion transport pathways that prevent normal cycling of the lithium ion battery; the too large average pore diameter (for example, greater than 1 μm) of the pores in the fiber isolation layer may result in too poor mechanical strength of the fiber isolation layer at the pore diameter position, which may not resist the puncture of particles on the surface of the pole piece, for example, the puncture of active material particles, and may easily cause the short circuit of local positive and negative electrodes, resulting in the problems of electrical performance attenuation and serious self-discharge of the lithium ion battery. The average pore diameter of pores in the fiber isolation layer is controlled within the range, so that the cycle performance and the safety of the lithium ion battery can be improved.
In some embodiments of the present application, the fibrous insulation layer has a porosity of 20% to 80%. Without being bound by any theory, too little porosity (e.g., less than 20%) of the fibrous separator layer can result in insufficient ion transport pathways that prevent normal cycling of the lithium ion battery; too large porosity (for example, less than 80%) of the fiber isolation layer can result in unstable structure of the fiber isolation layer, poor mechanical strength of the fiber isolation layer, and failure to resist puncture of particles on the surface of the pole piece, such as puncture of active material particles, which easily causes short circuit of a local positive electrode and a local negative electrode, and causes problems of electrical performance attenuation and serious self-discharge of the lithium ion battery. According to the application, the porosity of the fiber isolation layer is controlled within the range, so that the cycle performance and the safety of the lithium ion battery can be improved.
In some embodiments of the present application, the thickness of the fibrous insulation layer is 0.5 μm to 20 μm, preferably 1 μm to 15 μm, more preferably 1 μm to 10 μm. Without being limited to any theory, the thickness of the fiber isolation layer is too small (for example, less than 0.5 μm), the mechanical strength of the fiber isolation layer is poor, and the safety of the lithium ion battery is not improved; the thickness of the fiber isolation layer is too large (for example, more than 20 μm), which is not beneficial to improving the energy density of the lithium ion battery. This application is through the thickness of control fibre isolation layer in above-mentioned within range, can make the fibre isolation layer thinner for traditional barrier film, improves lithium ion battery energy density when guaranteeing that lithium ion battery has good security.
In some embodiments of the present application, the polymer fibers have a diameter of 50nm to 1 μm, preferably 100nm to 500 nm. Without being bound by any theory, the polymer fiber has an excessively small diameter (e.g., less than 50nm), and the structural strength of the polymer fiber is low, which is not favorable for improving the safety of the lithium ion battery; too large a diameter of the polymer fiber (e.g., greater than 1 μm) can affect the pore size of the pores in the fibrous separator layer, resulting in an insufficient ion transport path and preventing the normal cycling of the lithium ion battery. By controlling the diameter of the polymer fiber within the range, the cycle performance and the safety of the lithium ion battery can be improved.
The material of the polymer fiber is not particularly limited as long as the object of the present application can be achieved, and may be, for example, a lithium ion conductor material. In some embodiments of the present application, the polymer fibers comprise polyvinylidene fluoride, polyimide, polyamide, polyacrylonitrile, polyethylene glycol, polyethylene oxide, polyphenylene oxide, polypropylene carbonate, polymethyl methacrylate, polyethylene terephthalate, polyvinylidene fluoride-hexafluoropropylene, poly (vinylidene fluoride-co-chlorotrifluoroethylene), polyethylene oxide, or at least one of the foregoing derivatives. Preferably at least one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyacrylonitrile, polymethyl methacrylate, polyphenylene oxide, polypropylene carbonate, polyethylene oxide, or derivatives thereof.
In some embodiments of the present application, the fibrous insulation layer may further comprise inorganic particles, the inorganic particles account for less than or equal to 40% by mass of the fibrous insulation layer, and at least one of the following conditions (a) to (c) is satisfied: (a) the inorganic particles are positioned on the surface of the fiber isolation layer; (b) the inorganic particles are positioned in the polymer fiber gaps of the fiber isolation layer; (c) the inorganic particles are compounded in the polymer fibers. In the application, the inorganic particles account for less than or equal to 40% of the mass of the fiber isolation layer by controlling the mass of the inorganic particles, so that the fiber isolation layer has excellent mechanical strength, the puncture resistance of the fiber isolation layer is improved, and the safety of the lithium ion battery is improved.
In some embodiments of the present application, the inorganic particles further comprise an inorganic filler, the inorganic filler being compounded in the polymer fibers, i.e., the polymer fibers further comprise an inorganic filler, the inorganic filler being present in the polymer fibers in an amount of 5 to 10% by mass. According to the preparation method, the inorganic filler is compounded in the polymer fiber, and the content of the inorganic filler is controlled within the range, so that the polymerization degree of the polymer in the fiber isolation layer is reduced, and the amorphization of the polymer is favorable for improving the ionic conductivity, so that the dynamic performance of the lithium ion battery is improved.
In some embodiments of the present application, the inorganic particles have an average particle size of 20nm to 100nm, preferably 20nm to 50 nm. By controlling the average particle diameter of the inorganic particles within the above range, the inorganic particles can have good dispersibility, and thus can be more uniformly dispersed on the surface and/or inside of the fiber separator, improving the performance of the fiber separator.
The inorganic particles or inorganic filler are not particularly limited as long as the object of the present application can be achieved, and for example, the inorganic particles or inorganic filler include hafnium oxide (H)fO2) Strontium titanate (SrTiO)3) Tin dioxide (SnO)2) Cesium oxide (CeO)2) Magnesium oxide (MgO), nickel oxide (NiO), calcium oxide (CaO), barium oxide (BaO), zinc oxide (ZnO), zirconium oxide (ZrO)2) Yttrium oxide (Y)2O3) Aluminum oxide (Al)2O3) Titanium oxide (TiO)2) Silicon dioxide (SiO)2) Boehmite, magnesium hydroxide (Mg (OH)2) Aluminum hydroxide (Al (OH)3) Lithium phosphate (Li)3PO4) Lithium titanium phosphate (Li)xTiy(PO4)3Wherein 0 is<x<2 and 0<y<3) Lithium aluminum titanium phosphate (Li)xAlyTiz(PO4)3Wherein 0 is<x<2，0<y<1, and 0<z<3)、Li1+x+y(Al,Ga)x(Ti,Ge)2-xSiyP3-yO12(x is more than or equal to 0 and less than or equal to 1 and y is more than or equal to 0 and less than or equal to 1), lithium lanthanum titanate (LixLayTiO3Wherein 0 is<x<2 and 0<y<3) Lithium germanium thiophosphate (Li)xGeyPzSwWherein 0 is<x<4，0<y<1，0<z<1, and 0<w<5)、Lithium nitride (Li)xNyWherein 0 is<x<4，0<y<2)、SiS2Glass (Li)xSiySzWherein 0 is less than or equal to x<3，0<y<2, and 0<z<4)、P2S5Glass (Li)xPySzWherein 0 is less than or equal to x<3，0<y<3, and 0<z<7) Lithium oxide (Li)2O), lithium fluoride (LiF), lithium hydroxide (LiOH), lithium carbonate (Li)2CO3) Lithium metaaluminate (LiAlO)2) Lithium germanium phosphorus sulfur ceramics (Li)2O-Al2O3-SiO2-P2O5-TiO2-GeO2) Particle or garnet ceramic (Li3+ xLa)3M2O12Wherein x is more than or equal to 0 and less than or equal to 5, and M comprises at least one of Te, Nb or Zr) particles.
In some embodiments of the present application, a conductive coating may be disposed between the current collector and the active material layer, so as to improve the conductivity between the current collector and the active material layer, and further improve the dynamic performance of the lithium ion battery; and/or, at least one surface of the fiber isolation layer is provided with an inorganic coating, so that the mechanical strength of the fiber isolation layer is improved, and the safety of the lithium ion battery is further improved. The material of the conductive coating is not particularly limited as long as the object of the present invention can be achieved, and may be, for example, a conductive material such as carbon nanotube, conductive carbon, graphene, or the like. The conductive coating can be coated on both sides of the surface of the current collector or on one side of the surface of the current collector.
The method for preparing the fibrous separator layer is not particularly limited, and a method known to those skilled in the art may be used, and for example, the following method may be used:
dispersing a polymer in an organic solvent, and uniformly stirring until the viscosity of the slurry is stable to obtain a spinning solution; and spraying the spinning solution on the surface of the electrode pole piece by using an electrostatic spinning method to prepare a fiber isolation layer. Parameters such as tortuosity, porosity and thickness of the polymer fiber are adjusted by controlling parameters such as spinning voltage of a spinning device, pouring speed of spinning solution, receiving distance, concentration of the spinning solution, spinning time and rotating speed of a collecting roller.
If the electrode plate with the fiber isolation layers on the two sides needs to be prepared, the steps can be repeated on the back of the electrode plate, and the electrode plate with the fiber isolation layers on the two sides is obtained.
Also, if it is desired to improve the strength and safety of the fibrous insulation layer, the fibrous insulation layer may include an inorganic coating on its surface and/or inorganic particles within the fibrous insulation layer. The fibrous insulation layer comprising inorganic particles may be prepared by: spraying a slurry containing inorganic particles while spinning the polymer fibers, and/or using a slurry of polymer fibers containing inorganic filler. Wherein, the inorganic filler is added into the spinning solution, which can further improve the thermal stability of the fiber isolating layer, such as silica, lithium aluminum titanium phosphate, etc. The inorganic particles and the inorganic filler in the present application may be selected from the same inorganic substance or may be selected from different inorganic substances.
The technical personnel in the field should understand, this application can be at anodal pole piece surface preparation fibre isolation layer, also can be at the negative pole piece surface preparation fibre isolation layer, of course, can also be at anodal, negative pole piece surface preparation fibre isolation layer simultaneously, as long as can realize this application purpose.
For example, the fiber separator may be prepared on one side of the positive electrode plate, or on one side of the negative electrode plate, or on both sides of the positive electrode plate, or on both sides of the negative electrode plate, or on one side of the positive electrode plate and one side of the negative electrode plate.
According to the preparation process of the fiber isolation layer, the fiber isolation layer is integrated on the electrode plate, so that the production flow of the lithium ion battery can be greatly simplified; the thickness of the fiber isolation layer is controllable, and the thickness of the fiber isolation layer can be reduced by adjusting process parameters, so that the energy density of the lithium ion battery is improved; the polymer fibers prepared under the process condition have higher tortuosity, so that the weaving capacity and acting force among the polymer fibers are improved, the tensile strength of the fiber isolation layer is improved, the high-tortuosity intertwined polymer fibers improve the density of the fiber isolation layer, and the self-discharge of the lithium ion battery is favorably improved.
The positive electrode sheet in the present application generally includes a positive electrode current collector and a positive electrode active material layer. The positive electrode current collector is not particularly limited, and may be any positive electrode current collector known in the art, such as an aluminum foil, an aluminum alloy foil, or a composite current collector. The positive electrode active material layer includes a positive electrode active material, and any positive electrode active material known in the art may be used without particular limitation, and may include at least one of lithium nickel cobalt manganese oxide (811, 622, 523, 111), lithium nickel cobalt aluminate, lithium iron phosphate, a lithium rich manganese-based material, lithium cobalt oxide, lithium manganese iron phosphate, or lithium titanate, for example.
The negative electrode sheet in the present application generally includes a negative electrode current collector and a negative electrode active material layer. The negative electrode current collector is not particularly limited, and any negative electrode current collector known in the art, such as copper foil, aluminum alloy foil, and composite current collector, may be used. The anode active material layer includes an anode active material, and the anode active material is not particularly limited, and any anode active material known in the art may be used. For example, at least one of artificial graphite, natural graphite, mesocarbon microbeads, soft carbon, hard carbon, silicon carbon, lithium titanate, and the like may be included.
The lithium ion battery of the present application further includes an electrolyte, which may be one or more of a gel electrolyte, a solid electrolyte, and an electrolyte including a lithium salt and a non-aqueous solvent. In some embodiments herein, the lithium salt is selected from LiPF6、LiBF4、LiAsF6、LiClO4、LiB(C6H5)4、LiCH3SO3、LiCF3SO3、LiN(SO2CF3)2、LiC(SO2CF3)3、LiSiF6One or more of LiBOB and lithium difluoroborate. For example, the lithium salt may be LiPF6Since it can give high ion conductivityRate and improve cycle characteristics. The non-aqueous solvent may be a carbonate compound, a carboxylate compound, an ether compound, other organic solvent, or a combination thereof. The carbonate compound may be a chain carbonate compound, a cyclic carbonate compound, a fluoro carbonate compound, or a combination thereof. Examples of the above chain carbonate compound are dimethyl carbonate (DMC), diethyl carbonate (DEC), 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 fluoro carbonate compound are fluoroethylene carbonate (FEC), 1, 2-difluoroethylene carbonate, 1, 2-trifluoroethylene carbonate, 1,2, 2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1, 2-difluoro-1-methylethylene carbonate, 1, 2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate, and combinations thereof. Examples of the above carboxylic acid ester compounds are methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ -butyrolactone, decalactone, valerolactone, mevalonolactone, caprolactone, and combinations thereof. Examples of the above ether compounds are dibutyl ether, tetraglyme, diglyme, 1, 2-dimethoxyethane, 1, 2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, and combinations thereof. Examples of such other organic solvents are dimethylsulfoxide, 1, 2-dioxolane, sulfolane, methyl sulfolane, 1, 3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate esters and combinations thereof.
The present application also provides an electronic device including the electrochemical device described in the embodiments of the present application, which has excellent rate performance and safety.
The electronic device of the present application is not particularly limited, and may be any electronic device known in the art. In some embodiments, the electronic device may include, but is not limited to, a notebook computer, a pen-input computer, a mobile computer, an electronic book player, a portable phone, a portable facsimile machine, a portable copier, a portable printer, a headphone, a video recorder, a liquid crystal television, a handheld cleaner, a portable CD player, a mini-disc, a transceiver, an electronic organizer, a calculator, a memory card, a portable recorder, a radio, a backup power source, an electric motor, an automobile, a motorcycle, a power-assisted bicycle, a lighting fixture, a toy, a game machine, a clock, an electric tool, a flashlight, a camera, a large household battery, a lithium ion capacitor, and the like.
The process for preparing the electrochemical device is well known to those skilled in the art, and the present application is not particularly limited. For example, the electrochemical device may be manufactured by the following process: stacking a negative pole piece and a positive pole piece to form a lamination, fixing four corners of the whole lamination structure by using an adhesive tape, placing the lamination structure into an aluminum-plastic film, and performing top-side sealing, electrolyte injection and packaging to obtain the electrochemical device; or, oppositely and overlapping the negative pole piece and the positive pole piece of the fiber isolation layer to form an electrode assembly, winding and folding the electrode assembly according to the requirement, putting the electrode assembly into a shell, injecting electrolyte into the shell, and sealing the shell; or, the positive pole piece and the negative pole piece of the integrated fiber isolation layer are oppositely overlapped and wound into an electrode assembly, the electrode assembly is placed into the shell after the operations of winding, folding and the like are carried out according to needs, and the electrolyte is injected into the shell and sealed. Further, an overcurrent preventing element, a guide plate, or the like may also be placed in the housing as necessary.
An electrochemical device and an electronic device are provided, in which a fiber separation layer of the electrochemical device includes polymer fibers by controlling a tortuosity τ of the polymer fibers in the fiber separation layer0Comprises the following steps: 1.2<τ0<1.9, can improve the homogeneous degree in the fibre isolation layer pore, the fibre isolation layer of this application has improved electrochemical device's self-discharge problem to improve electrochemical device's multiplying power performance and security.
Drawings
In order to illustrate the technical solutions of the present application and the prior art more clearly, the following briefly introduces examples and figures that need to be used in the prior art, it being obvious that the figures in the following description are only some examples of the present application.
FIG. 1 is a schematic structural view of an electrode sheet according to an embodiment of the present application;
FIG. 2 is a schematic view of an electrode sheet structure according to another embodiment of the present application;
FIG. 3 is a schematic view of the electrode sheet structure according to yet another embodiment of the present application;
FIG. 4 is a schematic view of the electrode pad structure of a fourth embodiment of the present application;
FIG. 5 is a schematic view of the electrode sheet structure of a fifth embodiment of the present application;
FIG. 6 is a schematic view of the electrode pad structure of a sixth embodiment of the present application;
FIG. 7 is a schematic view of the electrode sheet structure of a seventh embodiment of the present application;
FIG. 8 is a schematic structural view of a spinning apparatus in one embodiment of the present application;
FIG. 9a is a Scanning Electron Microscope (SEM) image of the surface of a fibrous insulation layer of comparative example 5;
FIG. 9b is a surface SEM image of a fibrous insulation layer of example 6;
FIG. 10a is a surface SEM image of a fibrous insulation layer of comparative example 5 (at a high magnification of about 3000 times);
FIG. 10b is a surface SEM image of the fibrous insulation layer of example 6 (at a high magnification of about 3000 times);
FIG. 11a is a schematic drawing of a plain fiber insulation layer drawn in plan view;
FIG. 11b is a schematic drawing of a planar stretch of a fibrous insulation layer of the present application;
FIG. 12a is a schematic perspective view of a conventional fibrous insulation layer;
fig. 12b is a schematic perspective view of a fibrous insulation layer of the present application.
Reference numerals: 1: a positive current collector; 2: a positive conductive coating; 3: a positive electrode active material layer; 4: a fibrous insulation layer; 5: a negative electrode active material layer; 6: a negative conductive coating; 7: a negative current collector; 8: an inorganic coating.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is further described in detail below with reference to the accompanying drawings and examples. It is to be understood that the embodiments described are only a few embodiments of the present application and not all embodiments. All other technical solutions obtained by a person of ordinary skill in the art based on the embodiments in the present application belong to the scope of protection of the present application.
Fig. 1 shows a schematic structural view of an electrode sheet according to an embodiment of the present application, i.e., a schematic view of a fiber separator layer 4 disposed on one side of the electrode sheet. Referring to fig. 1, a positive electrode active material layer 3 is disposed on a surface of a positive electrode current collector 1, a fiber isolation layer 4 is disposed on a surface of the positive electrode active material layer 3, and the fiber isolation layer 4 is disposed on a single surface of an electrode sheet. Of course, in another embodiment, it may be that the surface of the negative electrode current collector 7 is provided with the negative electrode active material layer 5, and the surface of the negative electrode active material layer 5 is provided with the fibrous separator 4.
Fig. 2 shows a schematic structural diagram of an electrode sheet according to another embodiment of the present application, namely a schematic diagram of a fiber separator 4 arranged on both sides in a positive electrode sheet. Referring to fig. 2, both sides of the positive electrode current collector 1 are provided with a positive electrode active material layer 3 and a fibrous separator 4. The fiber separator 4 is provided with a negative electrode active material layer 5 and a negative electrode current collector 7 on the side away from the positive electrode active material layer 3.
Fig. 3 shows a schematic structural diagram of an electrode sheet according to yet another embodiment of the present application, namely a schematic diagram of a fiber isolation layer 4 disposed on one side of the electrode sheet and added with a conductive coating. Referring to fig. 3, a positive conductive coating 2, a positive active material layer 3 and a fiber isolation layer 4 are sequentially disposed on the surface of a positive current collector 1, and the fiber isolation layer 4 is disposed on a single surface of an electrode plate.
Fig. 4 shows a schematic structural diagram of an electrode pole piece according to a fourth embodiment of the present application, namely a schematic diagram of a fiber isolation layer 4 arranged on both sides of a positive pole piece and a conductive coating added thereto. Referring to fig. 4, both sides of the positive current collector 1 are provided with a positive conductive coating 2, a positive active material layer 3 and a fiber isolation layer 4, and one side of the fiber isolation layer 4 departing from the positive active material layer 3 is sequentially provided with a negative active material layer 5, a negative conductive coating 6 and a negative current collector 7.
Fig. 5 shows a schematic structural diagram of an electrode sheet according to a fifth embodiment of the present application, that is, a schematic diagram of a fiber isolation layer 4 is provided and added with a conductive coating and an inorganic coating on one side of the electrode sheet. Referring to fig. 5, a positive conductive coating 2, a positive active material layer 3, a fiber isolation layer 4 and an inorganic coating 8 are sequentially disposed on the surface of a positive current collector 1, and the fiber isolation layer 4 is disposed on one side of an electrode plate.
Fig. 6 shows a schematic structural diagram of an electrode plate of a sixth embodiment of the present application, namely a schematic diagram of a fiber isolation layer 4 arranged on both sides of a positive electrode plate and added with a conductive coating and an inorganic coating. Referring to fig. 6, both sides of the positive electrode current collector 1 are provided with a positive electrode conductive coating 2, a positive electrode active material layer 3, a fibrous separator 4, and an inorganic coating 8.
Fig. 7 shows a schematic structural diagram of an electrode plate according to a seventh embodiment of the present application, that is, a schematic diagram of a fiber separator 4 disposed on both sides of a negative electrode plate and added with a conductive coating and an inorganic coating. Referring to fig. 7, both sides of the negative electrode current collector 7 are provided with a negative electrode conductive coating 6, a negative electrode active material layer 5, a fibrous separator 4, and an inorganic coating 8.
Fig. 8 is a schematic structural view of a spinning apparatus in an embodiment of the present application, and referring to fig. 8, the spinning apparatus includes an electrospinning nozzle 11, a collecting roller 12, and a pole piece 13. The receiving distance in this application may refer to the vertical distance between the electrospinning spray heads 11 and the pole pieces 13.
Hereinafter, embodiments of the present application will be described in more detail with reference to examples and comparative examples. Various tests and evaluations were carried out according to the following methods. Unless otherwise specified, "part" and "%" are based on mass.
The test method and the test equipment are as follows:
tortuosity τ of Polymer fiber0And (3) testing:
the tortuosity test mode of the polymer fibers can be performed by the test method described in application numbers 97195703.7, 201922086518.2.
Measurement of Polymer fiber tortuosity τ by image analysis0Mainly comprises preprocessing of input images, contour tracing, feature extraction and identification of polymer fibers and calculation and analysis of related parameters. In addition, before testing, the pixels of the image need to be calibrated by using an eyepiece micrometer and an objective micrometer. The polymer fiber sample is placed on an object stage, after imaging through a camera lens and a CCD (Charge-coupled Device), the imaging is collected into a computer, and feature extraction, identification and measurement are carried out on the polymer fiber in the image by length measurement software, and then measurement is carried out.
The polymer fiber can be measured in the test process by collecting fiber images by using two light source signals of reflected light and projected light. After the image information is obtained, the image background nonuniformity is preprocessed by software analysis to obtain clear polymer fiber outline, so that the actual length L and the bending length L of the polymer fiber are measured0And the tortuosity of the polymer fiber is further determined according to the expression tau 0-L/L0. The fiber tortuosity data in the image field can be integrated, that is, the tortuosity of a plurality of polymer fibers in the image field can be measured, and then statistics can be performed, for example, the average value of the tortuosity of the plurality of polymer fibers can be calculated.
Tortuosity τ of fiber insulation layer1And (3) testing:
calculating the tortuosity of the fiber isolation layer by adopting a Macmalin formula:
Figure BDA0003171119420000091
wherein
Figure BDA0003171119420000092
Epsilon is the porosity, rho, of the fibrous insulationsIs the resistivity of the fibrous insulation layer, peIs the electrolyte resistivity.
Pore size testing of pores in fibrous insulation:
completely wetting and filling a pore channel of a diaphragm to be detected (such as a fiber isolating layer) with liquid, and forming positive pressure in the pore channel due to a capillary phenomenon;
secondly, placing the diaphragm into a closed groove, pressurizing by gas pressure to extrude liquid out of a capillary channel;
thirdly, according to the relative relationship between the pressure applied when the liquid in the single pore channel is completely extruded from the capillary channel and the diameter of the pore channel, the pore diameter of the diaphragm can be obtained according to a Laplace equation which is shown as the following formula:
d＝-4γcosθ/ΔP×100％
wherein d is the pore diameter, Δ P is the pressure, γ is the surface tension of the liquid, and θ is the contact angle of the membrane and the liquid. The liquid in the diaphragm can be extruded out successively under different pressures to generate a certain gas penetration flow, and the pore size and pore size distribution can be calculated according to the relation between the pressure and the flow change.
Porosity test of the fibrous insulation layer:
drying the fiber isolation layer sample in a vacuum drying oven at 105 ℃ for 2h, taking out, placing in a dryer for cooling, testing, wrapping the isolation film with A4 paper, flatly spreading on a cutting die, and stamping with a stamping machine to prepare the sample for testing. The thickness of the sample is measured by using a ten-thousandth ruler, the apparent volume V1 of the sample is calculated according to the surface area and the thickness of the sample, and then the true volume V2 of the test sample is measured by using a true densitometer (model AccuPyc II), so that the porosity is (V1-V2)/V1 multiplied by 100 percent.
Thickness test of fibrous insulation layer:
under the normal temperature environment, the fiber isolation layer is cut into sample strips with the width of 50mm along the transverse direction, three parallel samples are obtained, a ten-thousandth micrometer thickness gauge (Mitutoyo testing VL-50B, the diameter of a testing head is 5mm, the pressure is 0.01N under the test) is used for uniformly testing 10 data points along the central position of the transverse direction, and after 3 parallel samples are tested, the average value of 30 test data is taken as the thickness of the fiber isolation layer.
Diameter testing of polymer fibers:
the fiber separator was photographed at 10000 times magnification by SEM image, and the fiber diameter was counted in the visual field range to calculate the average diameter.
Inorganic particle size test:
the average particle size of the inorganic particles was measured using a laser particle sizer.
The particle size of the inorganic particles may be counted by means of SEM images or the like, and the average particle size thereof may be calculated.
And (3) testing the binding power between the fiber isolation layer and the negative pole piece:
firstly, preparing a prepared pole piece containing a fiber isolation layer into a standard test sample strip which accords with a tensile machine test, and fixing the pole piece on a test steel plate;
manually peeling off the fiber isolation layer carefully, wherein one end of a chuck of the stretcher clamps the pole piece and the steel plate to be fixed, and the other end clamps the fiber isolation layer;
stretching by a universal stretcher, gradually stripping the fiber isolation layer of the strip sample, and recording the force value during separation;
fourthly, calculating the adhesive force between the polymer fiber layer and the pole piece through the force value obtained in the third step;
testing the self-discharge rate of the lithium ion battery:
the lithium ion battery was discharged to 3.0V at a current of 0.5C, left to stand for 5min, and then charged to 3.85V at a constant current of 0.5C, then charged to a current of 0.05C at a constant voltage of 3.85V, left to stand in an environment of 25 ℃ ± 3 ℃ for two days, and the voltage OCV1 at this time was tested and recorded. Next, the lithium ion battery was allowed 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.
And 2C specific discharge capacity and 0.1C specific discharge capacity test:
the lithium ion batteries in the embodiments and the comparative examples were subjected to a charge and discharge test using a blue (LAND) series battery test system, and the charge and discharge performance was tested, and the lithium ion batteries were charged at a constant current of 0.1C magnification at normal temperature until the voltage reached 4.2V, and further charged at a constant voltage of 4.2V until the current was less than 0.05C, so that the lithium ion batteries were in a full charge state of 4.2V.
Then constant current discharging at 2C rate untilThe voltage is stopped at 3.0V, and the obtained capacity is the 2C specific discharge capacity which is marked as SC1(ii) a Charging the lithium ion battery according to the charging process to enable the lithium ion battery to be in a 4.2V full-charge state, then discharging at a constant current of 0.1C multiplying power until the voltage is 3.0V, and stopping discharging until the obtained capacity is 0.1C specific discharge capacity which is marked as SC2(ii) a The ratio of the 2C specific discharge capacity to the 0.1C specific discharge capacity is as follows: (SC)1/SC2)×100％。
Capacity retention ratio:
charging a lithium ion battery to 4.2V at a constant current of 0.5C, then charging to 0.05C at a constant voltage of 4.2V, standing for 10min in an environment with the temperature of 25 +/-3 ℃, then discharging to 3.0V at a current of 0.5C, and recording the first discharge capacity as Q1The cycle was repeated 50 times in this manner, and the discharge capacity at this time was recorded as Q50The capacity retention ratio η after 50 cycles was obtained by the following formula: eta is Q50/Q1×100％。
Example 1
<1-1. preparation of negative electrode sheet >
Mixing the negative active material graphite, the conductive carbon black and the styrene butadiene rubber according to the mass ratio of 96: 1.5: 2.5, adding deionized water as a solvent, preparing slurry with the solid content of 70%, and uniformly stirring. And uniformly coating the slurry on one surface of a copper foil with the thickness of 8 mu m, and drying at 110 ℃ to obtain the negative pole piece.
And after the steps are completed, finishing the single-side coating of the negative pole piece. And then, the steps are also finished on the back surface of the pole piece by a completely consistent method, and the cathode pole piece with the finished double-sided coating is obtained. After coating, the pole pieces were cut to size (41mm × 61mm) for use.
<1-2. preparation of Positive electrode sheet >
The positive electrode active material lithium cobaltate (LiCoO)2) Mixing conductive carbon black and polyvinylidene fluoride (PVDF) according to a mass ratio of 97.5: 1.0: 1.5, adding N-methylpyrrolidone (NMP) as a solvent, preparing slurry with the solid content of 75%, and uniformly stirring. The slurry was uniformly coated on one surface of an aluminum foil having a thickness of 12 μmAnd drying at 90 ℃ to obtain the positive pole piece. After the steps are completed, the single-side coating of the positive pole piece is completed. And then, the steps are also finished on the back of the pole piece by a completely consistent method, and the dispersing agent in the coating is dried at the temperature of 90 ℃, so that the positive pole piece with the double-sided coating is obtained. After coating, the pole pieces were cut to size (38 mm. times.58 mm) for use.
<1-2-1. preparation of spinning solution >
And (3) dispersing PVDF in a mixed solvent of Dimethylformamide (DMF) and acetone (7: 3), and uniformly stirring until the viscosity of the slurry is stable to obtain a spinning solution with the solid content of 25%.
<1-2-2. preparation of fibrous Barrier layer >
The spinning solution is sprayed on the surface of the positive active material layer of the positive pole piece by an electrostatic spinning method according to the process parameters shown in table 1, so as to prepare a PVDF fiber isolation layer with the thickness of 15 μm, wherein the average pore diameter, the thickness, the porosity, the tortuosity and the like of the PVDF fiber isolation layer are shown in table 1.
<1-3. preparation of electrolyte solution >
Mixing organic solvents of Ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC) at a mass ratio of EC: EMC: DEC: 30: 50: 20 in a dry argon atmosphere to obtain an organic solution, and adding lithium salt of lithium hexafluorophosphate (LiPF) to the organic solvent6) Dissolving and mixing evenly to obtain LiPF6The concentration of (2) was 1.15 Mol/L.
<1-4. preparation of lithium ion Battery >
The coated negative electrode plate and positive electrode plate are oppositely stacked to form a structure as shown in fig. 2. And fixing four corners of the whole lamination structure by using an adhesive tape, placing the four corners into an aluminum-plastic film, and finally obtaining the lithium ion lamination battery after top-side sealing, liquid injection and packaging.
Example 2, example 3, and example 4
The procedure of example 1 was repeated, except that in < preparation of positive electrode sheet >, a fibrous separator was prepared according to the process parameters shown in table 1, and the average pore diameter, thickness, porosity, tortuosity, and the like of the fibrous separator thus prepared were as shown in table 1.
Example 5
The same as example 1 except that < preparation of fiber separator > was different from example 1.
<5-2-2. preparation of fibrous Barrier layer >
Dispersing silicon dioxide (average particle size is 2 μm) in a mixed solvent of DMF: acetone: 7: 3, and stirring uniformly until the viscosity of the slurry is stable to obtain slurry A with solid content of 40% as a raw material.
And spraying the spinning solution and the slurry A on the surface of the positive active material layer of the positive pole piece by using an electric spraying method, so that the inorganic particle silicon dioxide is synchronously prepared on the surface of the positive pole piece, and the fiber isolation layer with the inorganic filler in the polymer fiber gap is obtained. The thickness, average pore diameter, thickness, porosity, tortuosity, and the like of the fiber separator are shown in table 1.
Example 6
The same as example 1 except that < preparation of fiber separator > was different from example 1.
Adding inorganic particle precursor sodium ethyl orthosilicate (TEOS) into the spinning solution, and uniformly stirring until the viscosity of the slurry is stable to obtain suspension B with the mass fraction of 40% as a raw material.
And spraying the suspension B on the surface of the positive active material layer of the positive pole piece by using an electric spraying method to obtain the fiber isolation layer with inorganic particles in the polymer fibers. The thickness, average pore diameter, thickness, porosity, tortuosity, and the like of the fiber separator are shown in table 1.
Example 7 and example 8
The procedure was carried out in the same manner as in example 1 except that in < preparation of positive electrode sheet >, the average pore diameter of the fibrous separator was adjusted as shown in table 1.
Example 9, example 10, example 11, and example 12
The procedure was carried out in the same manner as in example 1 except that in < preparation of positive electrode sheet >, the thickness of the fibrous separator was adjusted as shown in table 1.
Example 13
The same procedure as in example 1 was repeated, except that in < preparation of positive electrode sheet >, polyethylene oxide (PEO) was used as the polymer for preparing the polymer fibers.
Example 14
The procedure of example 1 was repeated, except that the fiber separator was formed on the surface of the negative electrode sheet, and the fiber separator was not formed on the surface of the positive electrode sheet.
Example 15
<15-1. preparation of negative electrode sheet >
Mixing the negative active material graphite, the conductive carbon black and the styrene butadiene rubber according to the mass ratio of 96: 1.5: 2.5, adding deionized water as a solvent, preparing slurry with the solid content of 70%, and uniformly stirring. And uniformly coating the slurry on one surface of a copper foil with the thickness of 8 mu m, and drying at 110 ℃ to obtain the negative pole piece. After coating, the pole piece is cut into 74mm × 851mm specifications for standby.
And after the steps are completed, finishing the single-side coating of the negative pole piece. And then, the steps are also finished on the back surface of the pole piece by a completely consistent method, and the cathode pole piece with the finished double-sided coating is obtained.
<15-2. preparation of Positive electrode sheet >
The positive electrode active material lithium cobaltate (LiCoO)2) Mixing conductive carbon black and polyvinylidene fluoride (PVDF) according to a mass ratio of 97.5: 1.0: 1.5, adding N-methylpyrrolidone (NMP) as a solvent, preparing slurry with the solid content of 75%, and uniformly stirring. And uniformly coating the slurry on one surface of an aluminum foil with the thickness of 12 mu m, and drying at 90 ℃ to obtain the positive pole piece. After coating, the pole pieces were cut to a size of (74 mm. times.867 mm) for use.
<15-2-1. preparation of spinning solution >
And (3) dispersing PVDF in a mixed solvent of Dimethylformamide (DMF) and acetone (7: 3), and uniformly stirring until the viscosity of the slurry is stable to obtain a spinning solution with the solid content of 25%.
<15-2-2. preparation of fibrous Barrier layer >
The spinning solution is sprayed on the surface of the positive active material layer of the positive pole piece by an electrostatic spinning method according to the process parameters shown in table 1, so as to prepare a PVDF fiber isolation layer with the thickness of 15 μm, wherein the average pore diameter, the thickness, the porosity, the tortuosity and the like of the PVDF fiber isolation layer are shown in table 1.
After the steps are completed, the single-side coating of the positive pole piece is completed. And then, the steps are also finished on the back of the pole piece by a completely consistent method, and the dispersing agent in the coating is dried at the temperature of 90 ℃, so that the positive pole piece with the double-sided coating is obtained.
<15-3 > preparation of electrolyte solution >
Mixing organic solvents of Ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC) at a mass ratio of EC: EMC: DEC: 30: 50: 20 in a dry argon atmosphere to obtain an organic solution, and adding lithium salt of lithium hexafluorophosphate (LiPF) to the organic solvent6) Dissolving and mixing evenly to obtain LiPF6The concentration of (2) was 1.15 Mol/L.
<15-4. preparation of lithium ion Battery >
And oppositely overlapping the prepared negative pole piece and the positive pole piece of the integrated isolation layer to form an electrode assembly, then winding the tail part and the tab part of the structure, pasting the head part area of the positive pole, putting the positive pole into an aluminum-plastic film, and carrying out top side sealing, liquid injection and packaging to obtain the lithium ion battery.
Comparative example 1
The same procedure as in example 1 was repeated, except that < preparation of positive electrode sheet > was changed from example 1, and a Polyethylene (PE) separator having a thickness of 15 μm was used as the separator.
< preparation of Positive electrode sheet >
The positive electrode active material lithium cobaltate (LiCoO)2) Mixing conductive carbon black and polyvinylidene fluoride (PVDF) according to a mass ratio of 97.5: 1.0: 1.5, adding N-methylpyrrolidone (NMP) as a solvent, preparing slurry with the solid content of 75%, and uniformly stirring. The slurry was uniformly coated on a coating layer having a thickness of 12 μmAnd drying one surface of the aluminum foil at 90 ℃ to obtain the positive pole piece.
After the steps are completed, the single-side coating of the positive pole piece is completed. And then, the steps are also finished on the back surface of the pole piece by a completely consistent method, and the positive pole piece with the finished double-sided coating is obtained. After coating, the pole pieces were cut to size (38 mm. times.58 mm) for use.
Comparative example 2
The same procedure as in comparative example 1 was repeated, except that an inorganic coating was formed on the surface of the polyethylene separator to obtain a polyethylene separator having an inorganic coating.
< preparation of inorganic coating layer >
Silica (average particle size of 2 μm) was dispersed in N-methylpyrrolidone (NMP) to form a slurry having a solid content of 50%, and then the resulting slurry was uniformly coated on one side of a separator film substrate (polyethylene, thickness of 15 μm) by a micro gravure coating method, and dried to obtain an inorganic coating layer having a thickness of 0.5 μm.
Comparative example 3
The procedure of example 1 was repeated, except that in < preparation of positive electrode sheet >, a fibrous separator was prepared according to the process parameters shown in table 1, and the average pore diameter, thickness, porosity, tortuosity, and the like of the fibrous separator thus prepared were as shown in table 1.
Comparative example 4
The procedure of example 5 was repeated, except that in < preparation of positive electrode sheet >, a fibrous separator was prepared according to the process parameters shown in table 1, and the average pore diameter, thickness, porosity, tortuosity, and the like of the fibrous separator thus prepared were as shown in table 1.
Comparative example 5
The procedure of example 6 was repeated, except that in < preparation of positive electrode sheet >, a fibrous separator was prepared according to the process parameters shown in table 1, and the average pore diameter, thickness, porosity, tortuosity, and the like of the fibrous separator thus prepared were as shown in table 1.
Figure BDA0003171119420000161
Figure BDA0003171119420000171
As can be seen from examples 1 to 4 and comparative example 1, compared with a common PE isolation film, the fiber isolation layer of the present application can significantly improve the interfacial adhesion between the isolation layer and the pole piece. By controlling the tortuosity tau of the fibrous insulation0In the range of the application, the lithium ion battery can remarkably improve the ratio of the 2C discharge specific capacity to the 0.1C discharge specific capacity and the ratio of the discharge capacity after 50 circles to the first discharge capacity under the condition of maintaining a low self-discharge rate, and shows that the lithium ion battery has excellent rate performance and a low self-discharge rate.
As can be seen from examples 1 to 4 and comparative example 2, the fibrous separator of the present application has a higher porosity compared to a general PE separator having an inorganic coating layer, and thus can prevent the risk of pore blocking of inorganic particles, and the lithium ion battery of the present application has excellent rate properties and a lower self-discharge rate.
As can be seen from examples 1 to 4 and comparative example 3, the high tortuosity fibrous insulation of the present application can significantly improve the tensile strength of the insulation compared to conventional spun fibrous insulation. Because the fiber isolation layer has higher surface density, the risk of macroporosity in the fiber isolation layer is reduced, the self-discharge problem of the lithium ion battery is improved, and the lithium ion battery has excellent rate performance and lower self-discharge rate.
As can be seen from example 5 and comparative example 4, in the case that the fiber separator also contains the inorganic filler, the high-tortuosity fiber separator of the present application can significantly improve the tensile strength of the fiber separator, and the lithium ion battery of the present application has excellent rate performance and a low self-discharge rate.
From example 6 and comparative example 5, it can be seen that, in the case that the polymer fiber also has inorganic particles inside, the high-tortuosity fiber insulation layer of the present application can significantly improve the tensile strength of the fiber insulation layer, and the lithium ion battery of the present application has excellent rate performance and a lower self-discharge rate.
It can be seen from examples 1 to 6 that when the fibrous separator contains an inorganic filler or the polymer fibers contain inorganic particles, the dynamic performance of the lithium ion battery can be further improved, and the self-discharge rate of the lithium ion battery can be improved.
The average pore size and thickness of the fiber isolation layer, the material of the polymer fiber, the arrangement position of the fiber isolation layer, and the structure of the lithium ion battery generally affect the dynamic performance of the lithium ion battery, and it can be seen from examples 7 to 15 that the lithium ion battery with a low self-discharge rate and excellent rate performance can be obtained as long as the above parameters are within the range of the present application.
As can be seen from fig. 9a and 9b and fig. 10a and 10b, the fibrous insulation layer of example 6 of the present application has polymer fibers that are more tortuous than the fibrous insulation layer of comparative example 5, indicating a higher tortuosity, thereby improving the knitability and force between the polymer fibers and also improving the tensile strength of the fibrous insulation layer. The high-tortuosity intertwined polymer fibers improve the density of the fiber isolation layer, thereby being beneficial to improving the K value of the lithium ion battery and improving the safety of the lithium ion battery.
As can be seen from fig. 11a and 11b, the fiber insulation layer with high tortuosity of the present application has higher tensile strength when receiving a tensile force F due to higher tortuosity, so that the fiber insulation layer has higher mechanical strength.
As can be seen from fig. 12a and 12b, the fiber isolation layer with high tortuosity of the present application has a higher surface density, and the pores therein can form an ion transmission path, so as to ensure normal transmission of lithium ions, so that the lithium ion battery has a lower self-discharge rate and excellent dynamic performance.
The above description is only exemplary of the present application and should not be taken as limiting the present application, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims (14)

1. An electrochemical device comprising an electrode sheet comprising a current collector and an active material layer, wherein at least one surface of said electrode sheet has a fibrous separator layer comprising polymer fibers having a tortuosity τ0Comprises the following steps: 1.2<τ0<1.9。
2. The electrochemical device of claim 1, wherein the fibrous insulation layer has a tortuosity τ1Comprises the following steps: 1.2<τ1<1.8。
3. The electrochemical device of claim 1, wherein the pores in the fibrous separator layer have an average pore size of 20nm to 1 μ ι η.
4. The electrochemical device of claim 1, wherein the porosity of the fibrous separator layer is 20% to 80%.
5. The electrochemical device of claim 1, wherein the fibrous separator layer has a thickness of 0.5 to 20 μ ι η.
6. The electrochemical device of claim 1, wherein the polymer fibers have an average diameter of 50nm to 1 μ ι η.
7. The electrochemical device of claim 1, wherein the polymer fibers comprise at least one of polyvinylidene fluoride, polyimide, polyamide, polyacrylonitrile, polyethylene glycol, polyethylene oxide, polyphenylene oxide, polypropylene carbonate, polymethyl methacrylate, polyethylene terephthalate, polyvinylidene fluoride-hexafluoropropylene, poly (vinylidene fluoride-co-chlorotrifluoroethylene), polyethylene oxide, or derivatives thereof.
8. The electrochemical device of claim 1, wherein the fibrous separator layer further comprises inorganic particles, wherein the mass of the inorganic particles is less than or equal to 40% of the mass of the fibrous separator layer.
9. The electrochemical device according to claim 8, wherein the inorganic particles have an average particle diameter of 20nm to 100 nm.
10. The electrochemical device according to claim 1, wherein the polymer fiber further comprises an inorganic filler, and a mass content of the inorganic filler in the polymer fiber is 5% to 10%.
11. The electrochemical device according to claim 8 or 10, wherein the inorganic particles or inorganic filler comprises hafnium oxide, strontium titanate, tin oxide, cesium oxide, magnesium oxide, nickel oxide, calcium oxide, barium oxide, zinc oxide, zirconium oxide, yttrium oxide, aluminum oxide, titanium oxide, silicon dioxide, boehmite, magnesium hydroxide, aluminum hydroxide, lithium phosphate, lithium titanium phosphate, lithium aluminum titanium phosphate, lithium lanthanum titanate, lithium germanium thiophosphate, lithium nitride, SiS2Glass, P2S5At least one of glass, lithium oxide, lithium fluoride, lithium hydroxide, lithium carbonate, lithium metaaluminate, lithium germanium phosphorus sulfur ceramic particles, or garnet ceramic particles.
12. The electrochemical device of claim 1, wherein the electrochemical device satisfies at least one of the following characteristics:
(a) the polymer fiber has a tortuosity of tau0Comprises the following steps: 1.3<τ0<1.8；
(b) Tortuosity τ of the fibrous insulation layer1Comprises the following steps: 1.3<τ1<1.7；
(c) The thickness of the fiber isolation layer is 1-10 μm;
(d) a conductive coating is arranged between the current collector and the active material layer;
(e) the fibrous insulation layer has an inorganic coating on at least one surface thereof.
13. The electrochemical device of claim 1, wherein the polymer fiber comprises at least one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyacrylonitrile, polymethyl methacrylate, polyphenylene oxide, polypropylene carbonate, polyethylene oxide, or derivatives thereof.
14. An electronic device comprising the electrochemical device of any one of claims 1-13.
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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114583247A (en) * 2022-02-28 2022-06-03 宁德新能源科技有限公司 Electrochemical device and electronic device
CN115312974A (en) * 2022-07-22 2022-11-08 天津力神电池股份有限公司 Negative plate with isolating layer and battery thereof
WO2023065927A1 (en) * 2021-10-18 2023-04-27 宁德时代新能源科技股份有限公司 Pole piece, assembly, cell, battery, device, and pole piece manufacturing method and system
CN116169428A (en) * 2023-04-06 2023-05-26 宁德新能源科技有限公司 Separator, electrochemical device and electronic device comprising same

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20070292750A1 (en) * 2006-06-16 2007-12-20 Kirby Beard Optimized microporous structure of electrochemical cells
JP2009169289A (en) * 2008-01-18 2009-07-30 Kuraray Kuraflex Co Ltd Toner seal material
CN101842528A (en) * 2007-08-31 2010-09-22 可乐丽可乐富丽世股份有限公司 Base material for cushioning and use thereof
JP2011192528A (en) * 2010-03-15 2011-09-29 Teijin Ltd Polyolefin microporous film, separator for nonaqueous secondary battery, and nonaqueous secondary battery
JP2011207048A (en) * 2010-03-30 2011-10-20 Toray Ind Inc Fiber-reinforced resin laminate
JP2011210574A (en) * 2010-03-30 2011-10-20 Teijin Ltd Polyolefin microporous film, separator for nonaqueous secondary battery, and the nonaqueous secondary battery
CN105594014A (en) * 2013-12-17 2016-05-18 Lg化学株式会社 Separation membrane for electrochemical device
CN109792035A (en) * 2016-11-01 2019-05-21 阿莫绿色技术有限公司 Electrode and using its secondary cell and electrode preparation method
CN109802083A (en) * 2019-03-29 2019-05-24 宁德新能源科技有限公司 Electrochemical appliance

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20070292750A1 (en) * 2006-06-16 2007-12-20 Kirby Beard Optimized microporous structure of electrochemical cells
CN101842528A (en) * 2007-08-31 2010-09-22 可乐丽可乐富丽世股份有限公司 Base material for cushioning and use thereof
JP2009169289A (en) * 2008-01-18 2009-07-30 Kuraray Kuraflex Co Ltd Toner seal material
JP2011192528A (en) * 2010-03-15 2011-09-29 Teijin Ltd Polyolefin microporous film, separator for nonaqueous secondary battery, and nonaqueous secondary battery
JP2011207048A (en) * 2010-03-30 2011-10-20 Toray Ind Inc Fiber-reinforced resin laminate
JP2011210574A (en) * 2010-03-30 2011-10-20 Teijin Ltd Polyolefin microporous film, separator for nonaqueous secondary battery, and the nonaqueous secondary battery
CN105594014A (en) * 2013-12-17 2016-05-18 Lg化学株式会社 Separation membrane for electrochemical device
CN109792035A (en) * 2016-11-01 2019-05-21 阿莫绿色技术有限公司 Electrode and using its secondary cell and electrode preparation method
CN109802083A (en) * 2019-03-29 2019-05-24 宁德新能源科技有限公司 Electrochemical appliance

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2023065927A1 (en) * 2021-10-18 2023-04-27 宁德时代新能源科技股份有限公司 Pole piece, assembly, cell, battery, device, and pole piece manufacturing method and system
CN114583247A (en) * 2022-02-28 2022-06-03 宁德新能源科技有限公司 Electrochemical device and electronic device
CN115312974A (en) * 2022-07-22 2022-11-08 天津力神电池股份有限公司 Negative plate with isolating layer and battery thereof
CN115312974B (en) * 2022-07-22 2024-05-28 天津力神电池股份有限公司 Negative electrode sheet with isolating layer and battery thereof
CN116169428A (en) * 2023-04-06 2023-05-26 宁德新能源科技有限公司 Separator, electrochemical device and electronic device comprising same
CN116169428B (en) * 2023-04-06 2023-06-20 宁德新能源科技有限公司 Separator, electrochemical device and electronic device comprising same

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