WO2022198583A1 - Collecteur de courant de carbone, dispositif électrochimique comprenant un collecteur de courant de carbone et dispositif électronique - Google Patents

Collecteur de courant de carbone, dispositif électrochimique comprenant un collecteur de courant de carbone et dispositif électronique Download PDF

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WO2022198583A1
WO2022198583A1 PCT/CN2021/083054 CN2021083054W WO2022198583A1 WO 2022198583 A1 WO2022198583 A1 WO 2022198583A1 CN 2021083054 W CN2021083054 W CN 2021083054W WO 2022198583 A1 WO2022198583 A1 WO 2022198583A1
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current collector
carbon
conductive fibers
carbon current
present application
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PCT/CN2021/083054
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English (en)
Chinese (zh)
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刘宏威
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宁德新能源科技有限公司
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Priority to PCT/CN2021/083054 priority Critical patent/WO2022198583A1/fr
Priority to CN202180004872.3A priority patent/CN114531925B/zh
Publication of WO2022198583A1 publication Critical patent/WO2022198583A1/fr

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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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/663—Selection of materials containing carbon or carbonaceous materials as conductive part, e.g. graphite, carbon fibres
    • 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
    • H01M4/04—Processes of manufacture in general
    • 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

Definitions

  • the present application relates to the field of energy storage, and in particular, to a carbon current collector, a preparation method thereof, and electrochemical devices and electronic devices using the same.
  • Lithium-ion batteries have the advantages of high energy density, long cycle life and small self-discharge, and have been widely used; with the continuous advancement of technology, people have higher and higher requirements for the energy density of lithium-ion batteries.
  • the energy density of ion batteries has become a research hotspot.
  • Fluid can improve the gravimetric energy density of the battery; the use of a thinner carbon current collector can simultaneously increase the weight energy density and volumetric energy density of the battery; however, when the thickness of the carbon current collector becomes thinner, its strength is greatly reduced, which cannot meet the capacity of the battery
  • the conductivity of graphite is worse than that of traditional metal current collectors, and the polarization of electrons in the length direction of the pole piece is serious during the charge and discharge process, which affects the overall charge and discharge consistency of the pole piece, and affects the rate performance of the battery.
  • the present application provides a carbon current collector, the carbon current collector has higher tensile strength and lower internal resistance, and a lithium ion battery using the current collector can have a higher energy density and better rate performance.
  • the present application also provides electrochemical devices and electronic devices including the carbon current collectors.
  • the present application provides a carbon current collector comprising a carbon material film and conductive fibers, wherein the conductive fibers are distributed in the carbon material film along a length direction of the carbon current collector.
  • the included angle between the projection of the conductive fibers on the carbon material film and the length direction of the carbon current collector is 0° to 5°.
  • the tensile strength of the carbon current collector in the length direction is 200 MPa to 500 MPa.
  • the electrical resistance of the carbon current collector along the length direction is 3 m ⁇ to 30 m ⁇ .
  • the conductive fibers are in the form of sheets.
  • the conductive fibers have a width of 0.01 mm to 5 mm.
  • the conductive fibers have a thickness of 0.5 ⁇ m to 20 ⁇ m.
  • the conductive fibers satisfy at least one of the following characteristics: the spacing between adjacent conductive fibers in the width direction of the carbon current collector is 0.1 mm to 9 mm; the conductivity of the conductive fibers is 0.1 mm to 9 mm. 30 ⁇ 10 6 S/m to 60 ⁇ 10 6 S/m; the strength of the conductive fiber is 220 MPa to 1400 MPa.
  • the projected area of the conductive fibers on the carbon material film accounts for 10% to 90% of the total area of the carbon material film.
  • the conductive fibers are metal fibers.
  • the material of the metal fiber includes at least one of copper, aluminum or nickel.
  • the thickness of the carbon current collector is 2 ⁇ m to 10 ⁇ m.
  • the present application also provides a method for preparing a carbon current collector as described above in the first aspect, comprising the following steps:
  • the polymer in the polymer solution includes at least one of polyimide, polyacrylonitrile, carboxymethyl cellulose or polyvinyl alcohol.
  • the polymer solution may further include a carbon material.
  • the carbon material includes at least one of acetylene black, carbon nanotubes, or graphene.
  • the mass percentage of the carbon material is 1% to 80% based on the total mass of the polymer and the carbon material.
  • the present application provides an electrochemical device comprising the carbon current collector of the first aspect or the carbon current collector prepared by the method of the second aspect.
  • the present application provides an electronic device comprising the electrochemical device of the third aspect.
  • the carbon current collector of the present application has higher tensile strength (fiber length direction) and lower internal resistance;
  • Li-ion batteries using this current collector can have higher energy density and better rate performance.
  • FIG. 1 is a schematic top-view structure diagram of a carbon current collector according to an embodiment of the present application, and the symbols in the schematic diagram are as follows: 1-conductive fiber; 2-carbon material film.
  • FIG. 2 is a left-view structural schematic diagram of a carbon current collector according to an embodiment of the present application, and the symbols in the schematic diagram are as follows: 1-conductive fiber; 2-carbon material film.
  • a term may refer to a range of variation less than or equal to ⁇ 10% of the numerical value, such as less than or equal to ⁇ 5%, less than or equal to ⁇ 4%, less than or equal to ⁇ 3%, Less than or equal to ⁇ 2%, less than or equal to ⁇ 1%, less than or equal to ⁇ 0.5%, less than or equal to ⁇ 0.1%, or less than or equal to ⁇ 0.05%.
  • a list of items linked by the term "at least one of” can mean any combination of the listed items.
  • the phrase "at least one of A and B” means A only; B only; or A and B.
  • the phrase "at least one of A, B, and C” means A only; or B only; C only; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C.
  • Item A may contain a single element or multiple elements.
  • Item B may contain a single element or multiple elements.
  • Item C may contain a single element or multiple elements.
  • the present application provides a carbon current collector comprising a carbon material film and conductive fibers, wherein the conductive fibers are distributed in the carbon material film along a length direction of the carbon current collector.
  • the conductive fibers in the carbon current collector of the present application are distributed in the carbon material film along the length direction of the carbon current collector.
  • the conductive fibers distributed along the length direction of the carbon current collector can utilize fiber Its own strength provides the strength required by the current collector in the process of lithium-ion battery processing and transport, which solves the problem of low tensile strength of traditional carbon current collectors after thinning, which is insufficient for mass production and processing of lithium-ion batteries;
  • the direction of the conductive fibers is consistent with the length direction of the current collector, and the conductive fibers with high conductivity improve the conductivity in the length direction of the pole piece, which solves the problem of poor long-range conductivity of traditional carbon current collectors. Therefore, the carbon current collector of the present application has lower internal resistance and higher tensile strength, so that the thinner carbon current collector has better mass production processability and higher application feasibility. Lithium ions using this current collector can have higher energy density and better rate capability.
  • the included angle between the projection of the conductive fibers on the carbon material film and the length direction of the carbon current collector is 0° to 5°, such as 0.1°, 0.5°, 1.0°, 1.5°, 2.0° , 2.5°, 3.0°, 4.0°, 4.5°, or any value in between. If the included angle is too large, on the one hand, to prepare carbon current collectors of the same length, the required fiber length increases, the electron transmission distance increases, and the difficulty increases; on the other hand, the tensile strength of the current collector in the length direction is affected, and it will Creating a force component perpendicular to the length of the current collector increases the risk of tearing of the current collector perpendicular to its length. In addition, if the included angle is too large, the number of fibers running through the head and tail ends of a single pole piece is reduced, which is not conducive to long-range conduction and affects the conduction effect.
  • the included angle between the projection of the conductive fibers on the carbon material film and the length direction of the carbon current collector is 0°, that is, the conductive fibers are distributed parallel to the carbon current collector along the length direction of the carbon current collector. material film.
  • the strength of the conductive fibers distributed parallel to each other can more effectively improve the strength of the current collector along the fiber direction, and the amount of fibers used is less, which reduces the weight of the current collector.
  • the length direction of the carbon current collector is consistent with the coating direction of each material layer (such as electrode active material layer) in the process of pole piece processing, and is also consistent with the direction of the pole piece in the process of manufacturing electrochemical devices (such as batteries).
  • the winding direction is the same.
  • the width direction is perpendicular to the length direction.
  • the carbon current collector is shown in FIG. 1, which includes conductive fibers 1 and carbon material films 2, wherein the conductive fibers 1 are distributed in the carbon material films 2 at equal intervals along the MD direction.
  • the MD direction is consistent with the length direction of the carbon current collector.
  • the tensile strength of the carbon current collector in the length direction is 200 MPa to 500 MPa. In some embodiments, the tensile strength of the carbon current collector along the length direction is 220 MPa, 250 MPa, 270 MPa, 300 MPa, 330 MPa, 350 MPa, 380 MPa, 400 MPa, 450 MPa, 470 MPa, or any value therebetween.
  • the electrical resistance of the carbon current collector along the length direction is 3 m ⁇ to 30 m ⁇ .
  • the resistance along the length direction of the carbon current collector is 3.1m ⁇ , 3.3m ⁇ , 3.5m ⁇ , 3.7m ⁇ , 4.0m ⁇ , 4.3m ⁇ , 4.5m ⁇ , 4.7m ⁇ , 5.0m ⁇ , 5.3m ⁇ , 5.5m ⁇ m ⁇ , 5.7m ⁇ , 6.0m ⁇ , 6.5m ⁇ , 7.0m ⁇ , 7.5m ⁇ , 8.0m ⁇ , 8.5m ⁇ , 9.0m ⁇ , 10m ⁇ , 13m ⁇ , 15m ⁇ , 17m ⁇ , 20m ⁇ , 25m ⁇ , or any value in between.
  • the conductive fibers are in the form of sheets. Compared with other shapes such as cylindrical shape, sheet-shaped conductive fibers can obtain a current collector with a higher fiber projected area. The increase in the projected area of the fiber is beneficial to improve the tensile strength of the current collector and reduce the internal resistance in the length direction.
  • the thin thickness of the current collector restricts the diameter of cylindrical fibers from being too large, while the manufacturing of cylindrical fibers with too small diameter is difficult, and its uniform and dense arrangement is difficult, so it is difficult to prepare Current collectors with high fiber projected area.
  • the conductive fibers have a width of 0.01 mm to 5 mm. According to some embodiments of the present application, the conductive fibers have a width of 0.05mm, 0.1mm, 0.3mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1.0mm, 1.1mm, 1.3mm, 1.5mm , 1.7mm, 1.9mm, 2.0mm, 2.5mm, 3.0mm, 3.5mm, 4.0mm, 4.5mm or any value in between. In some embodiments of the present application, the conductive fibers have a width of 0.5 mm to 3 mm. Too wide fiber width may lead to too much fiber proportion, reducing the advantage of weight energy density, and too small width may lead to higher cost and difficulty in making current collectors.
  • the conductive fibers have a thickness of 0.5 ⁇ m to 20 ⁇ m.
  • the thickness of the conductive fibers is 0.5 ⁇ m, 1.0 ⁇ m, 1.5 ⁇ m, 2.0 ⁇ m, 2.5 ⁇ m, 3.0 ⁇ m, 4.0 ⁇ m, 4.5 ⁇ m, 5.0 ⁇ m, 7.0 ⁇ m, 9.0 ⁇ m, 10 ⁇ m, 11 ⁇ m, 13 ⁇ m, 15m, 17 ⁇ m, 19 ⁇ m or any value in between.
  • the conductive fibers have a thickness of 0.5 ⁇ m to 10 ⁇ m. Too thick fiber thickness will increase the thickness of the current collector, which will affect the volume energy density. Too small thickness will increase the cost and difficulty of fiber fabrication, reduce the tensile strength of the composite current collector, and increase the internal resistance.
  • the length direction of the conductive fibers is consistent with the length direction of the carbon current collector.
  • the direction perpendicular to the length direction of the conductive fibers is the width direction of the conductive fibers, and the dimension corresponding to this direction is the width of the conductive fibers.
  • the direction perpendicular to the length direction of the conductive fibers is the thickness direction of the conductive fibers, and the dimension corresponding to this direction is the thickness of the conductive fibers.
  • the spacing between adjacent conductive fibers along the width direction of the carbon current collector is 0.1 mm to 9 mm, such as 0.5 mm, 1.0 mm, 2.0 mm, 3.0 mm, 4.0 mm, 5.0 mm, 6.0 mm , 7.0mm or 8.0mm.
  • the spacing between adjacent conductive fibers along the width direction of the carbon current collector is 0.5 mm to 5 mm. If the interval is too small, the process is difficult and the cost is high; if the interval is too large, the proportion of fibers decreases, the tensile strength of the current collector decreases, and the internal resistance increases.
  • adjacent conductive fibers have the same spacing along the width direction of the carbon current collector.
  • the electrical conductivity of the conductive fibers is 30 ⁇ 10 6 S/m to 60 ⁇ 10 6 S/m, such as 40 ⁇ 10 6 S/m or 50 ⁇ 10 6 S/m.
  • the conductive fibers have a strength of 220 MPa to 1400 MPa, such as 300 MPa, 500 MPa, 700 MPa, 900 MPa, 1100 MPa or 1300 MPa.
  • the projected area of the conductive fibers on the carbon material film accounts for 10% to 90% of the total area of the carbon material film.
  • the proportion of the projected area of the conductive fibers on the carbon material film to the total area of the carbon material film is 20%, 25%, 30%, 35%, 40%, 45%, 50% , 60%, 70% or 80% etc.
  • the projected area of the conductive fibers on the carbon material film accounts for 20% to 50% of the total area of the carbon material film.
  • the conductive fibers are metal fibers.
  • the material of the metal fiber includes at least one of copper, aluminum or nickel.
  • the thickness of the carbon current collector is 2 ⁇ m to 10 ⁇ m. In some embodiments of the present application, the thickness of the carbon current collector is 3 ⁇ m, 4 ⁇ m, 5 ⁇ m, 6 ⁇ m, 7 ⁇ m, 8 ⁇ m, 9 ⁇ m, or any value therebetween. If the thickness of the current collector is too low, it is difficult to process and has many defects. If the thickness is too high, the volume energy density will be lost.
  • the present application also provides a method for preparing a carbon current collector as described above in the first aspect, comprising the following steps:
  • the polymer in the polymer solution includes at least one of polyimide, polyacrylonitrile, carboxymethyl cellulose or polyvinyl alcohol.
  • the polymer solution may further include a carbon material.
  • the carbon material includes at least one of acetylene black, carbon nanotubes, or graphene.
  • adding carbon material to the polymer solution can further reduce the resistance in the length direction of the current collector, which is due to the very high electrical conductivity of carbon materials such as acetylene black, carbon nanotubes or graphene, which can promote the carbon current collector.
  • the conductivity of itself and the conductivity of the current collector in the length direction are improved.
  • adding carbon nanotubes with a one-dimensional structure and graphene with a two-dimensional structure will form a richer conductive network and increase the electrical conductivity along the length of the current collector.
  • the mass percentage of the carbon material is 1% to 80% based on the total mass of the polymer and the carbon material. In some embodiments, based on the total mass of the polymer and the carbon material, the mass percentage of the carbon material is 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40% %, 45%, 50%, 60%, 70% or any value in between. As the mass content of carbon material increases, the electrical resistance decreases, but the tensile strength also decreases. This is due to the interface between the carbon material and the polymer.
  • the mass percentage of the carbon material is 1% to 50% based on the total mass of the polymer and the carbon material.
  • the substrate in step (1) is selected from glass, polytetrafluoroethylene plate, polypropylene plate, marble plate, and the like.
  • the carbonization atmosphere in step (3) is carbonization under the protection of an inert gas, such as a nitrogen atmosphere.
  • the carbonization temperature is 500°C to 800°C, such as 600°C, 650°C, 700°C or 750°C, and the like.
  • the carbonization time is 60 min to 150 min, such as 70 min, 90 min, 110 min, 130 min, and the like.
  • the pressing described in step (3) is cold pressing.
  • the carbonized film is cold-pressed by a cold press at a pressure of 5 tons and a speed of 1 m/min.
  • the present application further provides an electrochemical device comprising the carbon current collector provided by the present application.
  • the carbon current collector provided in the present application can be used as a current collector for the positive electrode and the negative electrode.
  • the positive electrode sheet includes the carbon current collector provided herein. According to some embodiments, the positive electrode sheet further includes a positive active material disposed on the carbon current collector.
  • the positive active material of the present application may include lithium nickel cobalt manganate (811, 622, 523, 111), lithium nickel cobalt aluminate, lithium iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide, lithium manganate, iron manganese phosphate At least one of lithium or lithium titanate.
  • the negative pole piece includes the carbon current collector provided herein. According to some embodiments, the negative pole piece further includes a negative active material disposed on the carbon current collector.
  • the negative active material in the present application may include at least one of artificial graphite, natural graphite, mesocarbon microspheres, soft carbon, hard carbon, silicon, silicon carbon, lithium titanate, and the like.
  • the electrochemical device of the present application such as a lithium ion battery, further includes an electrolyte, and the electrolyte may be one or more of a gel electrolyte, a solid electrolyte, and an electrolyte, and the electrolyte includes a lithium salt and a non-aqueous solvent.
  • the lithium salt is selected from LiPF 6 , LiBF 4 , LiAsF 6 , LiClO 4 , LiB(C 6 H 5 ) 4 , LiCH 3 SO 3 , LiCF 3 SO 3 , LiN(SO 2 CF 3 ) 2.
  • LiPF 6 may be chosen as the lithium salt because it gives high ionic conductivity and improves cycling characteristics.
  • the non-aqueous solvent may be a carbonate compound, a carboxylate compound, an ether compound, other organic solvents, or a combination thereof.
  • the above-mentioned carbonate compound may be a chain carbonate compound, a cyclic carbonate compound, a fluorocarbonate compound, or a combination thereof.
  • Examples of the above-mentioned chain carbonate compound are dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), carbonic acid Methyl ethyl ester (MEC) and combinations thereof.
  • Examples of cyclic carbonate compounds are ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylethylene carbonate (VEC), and combinations thereof.
  • fluorocarbonate compounds are fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate Ethyl carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-dicarbonate Fluoro-1-methylethylene, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate, and combinations thereof.
  • FEC fluoroethylene carbonate
  • 1,2-difluoroethylene carbonate 1,1-difluoroethylene carbonate
  • 1,1,2-trifluoroethylene carbonate Ethyl carbonate 1,1,2,2-tetrafluoroethylene carbonate
  • 1-fluoro-2-methylethylene carbonate 1-fluoro-1-methylethylene carbonate
  • 1,2-dicarbonate Fluoro-1-methylethylene 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethyl
  • carboxylate compounds are methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, ⁇ -butyrolactone , caprolactone, valerolactone, mevalonolactone, caprolactone, and combinations thereof.
  • ether compounds examples include dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethyl ether Oxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, and combinations thereof.
  • Examples of the above-mentioned other organic solvents are dimethyl sulfoxide, 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 material and shape of the separator used in the electrochemical device of the present application are not particularly limited, and it may be any technique disclosed in the prior art.
  • the separator includes a polymer or inorganic or the like formed from a material that is stable to the electrolyte of the present application.
  • the release film may include a substrate layer and a surface treatment layer.
  • the base material layer is a non-woven fabric, film or composite film with a porous structure, and the material of the base material layer is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate and polyimide.
  • a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene non-woven fabric, a polyethylene non-woven fabric or a polypropylene-polyethylene-polypropylene porous composite membrane can be selected.
  • At least one surface of the base material layer is provided with a surface treatment layer, and the surface treatment layer may be a polymer layer or an inorganic material layer, or a layer formed by mixing a polymer and an inorganic material.
  • the inorganic layer includes inorganic particles and a binder, and the inorganic particles are selected from aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium oxide, tin oxide, ceria, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, At least one of yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate.
  • the binder is selected from polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinylalkoxy , at least one of polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene.
  • the polymer layer contains a polymer, and the material of the polymer is selected from polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinylalkoxy, polyvinylidene fluoride, At least one of poly(vinylidene fluoride-hexafluoropropylene).
  • the present application further provides an electronic device comprising the electrochemical device described herein.
  • the electronic equipment or device of the present application is not particularly limited.
  • the electronic devices of the present application include, but are not limited to, notebook computers, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, headsets , VCR, LCD TV, Portable Cleaner, Portable CD Player, Mini CD, Transceiver, Electronic Notepad, Calculator, Memory Card, Portable Recorder, Radio, Backup Power, Motor, Automobile, motorcycle, Power-assisted Bicycle, Bicycle , lighting equipment, toys, game consoles, clocks, power tools, flashes, cameras, large household batteries and lithium-ion capacitors, etc.
  • Test method for resistance in the length direction of the current collector using an internal resistance tester, clamp the two clips connected to the internal resistance tester on the current collector respectively, and the size of the junction between the clip and the current collector is 0.5cm ⁇ 3cm, The 3cm long side is perpendicular to the length direction of the current collector, the two clips are spaced 30cm apart along the length direction of the current collector, and the long sides of the two clips are clamped on both sides of the pole piece.
  • Tensile strength test in the length direction of the current collector Use an Instron universal testing machine for tensile test to prepare a current collector spline with a width of 20mm and a length of 100mm, in which the length direction of the current collector is the same as the length direction of the conductive fiber, and the tension is set. The speed is 5mm/min, the test is stopped after breaking, and the average value of 3 tests is taken.
  • Thickness and width of conductive fibers use a micrometer for thickness measurement, randomly select 5 fibers with a length of 30cm, and measure at 4-6cm intervals, and take the average value of 25 measurements;
  • the width was measured using a laser microscope. Three fibers with a length of 30 cm were randomly selected and measured at 7-10 cm intervals. Each sample was measured three times, and the average value of nine measurements was finally taken.
  • Spacing distance of conductive fibers The spacing distance is measured with a laser microscope. Take a 10cm ⁇ 20cm current collector sample, cut it perpendicular to the fiber length direction, cut it into two samples of similar size, and measure the two fibers on the cross section. The distance between each sample is measured 3 values, and the average value of 6 measurements is taken.
  • Projected area of conductive fibers The projected area is tested by CT scanning. A 10cm ⁇ 10cm current collector is randomly selected and scanned perpendicular to the surface of the current collector to calculate the fiber projection ratio.
  • PI polyimide
  • PAN polyacrylonitrile
  • PVA polyvinyl alcohol
  • CMC carboxymethyl cellulose
  • SP acetylene black
  • CNT carbon nanotube
  • the copper conductive fibers with a thickness of 3 ⁇ m and a width of 1 mm were laid flat on the glass with a gap of 2 mm and straightened, and the PI polymer solution with a solid content of 1% was scraped on the release film. After drying, a PI copper fiber composite membrane with a thickness of 7 ⁇ m was obtained.
  • a carbon current collector in which the copper fibers are distributed in the composite film parallel to each other along the length direction of the carbon current collector, that is, the included angle between the projection of the copper fibers on the carbon material film and the length direction of the carbon current collector is 0°.
  • Example 1 the difference from the Example is that the parameters of each raw material in the synthesis process of the carbon current collector are adjusted, and the specific parameter changes are shown in the tables corresponding to each Example and Comparative Example.
  • Preparation of positive electrode Lithium cobaltate, acetylene black and polyvinylidene fluoride are fully stirred and mixed uniformly in N-methylpyrrolidone solvent system according to the weight ratio of 98:1:1 to prepare positive electrode slurry.
  • the prepared positive electrode slurry is coated on the above-mentioned carbon current collector, dried, and cold-pressed to obtain a positive electrode.
  • Preparation of negative electrode Graphite, polymethacrylic acid and styrene-butadiene rubber were fully stirred and mixed in an appropriate amount of deionized water solvent according to the weight ratio of 98:1:1 to form a uniform negative electrode slurry.
  • the prepared negative electrode slurry is coated on the carbon current collector, dried, and cold pressed to obtain a negative electrode.
  • Preparation of lithium ion battery stack the positive electrode, the separator and the negative electrode in order, so that the separator is placed between the positive electrode and the negative electrode for isolation.
  • a bare cell is obtained by winding.
  • the bare cell is placed in the outer package, and after vacuum drying, the electrolyte is injected and packaged.
  • the lithium-ion battery is obtained through the process of formation, degassing, trimming and other processes.
  • Table 1 shows the effect of the conductive fibers and the polymer species in the polymer solution on the performance of the prepared carbon current collectors and lithium-ion batteries containing the same.
  • the conductive fibers in Examples 2-5 are copper fibers, which are the same as those in Example 1, and the shape is sheet-like.
  • the thickness of the fibers is 3 ⁇ m and the width is 1 mm.
  • the distance between the fibers is 2 mm
  • the projected area ratio of the conductive fibers on the carbon material mold is 33.3%
  • the angle between the projection of the conductive fibers on the carbon material film and the length direction of the carbon current collector is 0°.
  • Comparative Examples 1-4 did not contain conductive fibers.
  • Example 1 and Comparative Examples 1-3 in Table 1 that the current collectors of Examples 1-5 containing conductive fibers have lower current collectors than the current collectors of Comparative Examples 1-4 without conductive fibers internal resistance and higher tensile strength.
  • the conductive fibers provide the strength required by the current collector during the processing and transport of lithium-ion batteries, which solves the problem that the traditional carbon current collectors have low strength after thinning and are insufficient for mass production of lithium-ion batteries; fiber orientation Consistent with the length direction of the current collector, the conductive fiber with high conductivity improves the conductivity in the length direction of the pole piece, which solves the problem of poor long-range conductivity of the traditional carbon current collector.
  • Table 2 shows the effects of the types and contents of carbon materials in the polymer solution on the performance of the prepared carbon current collectors and lithium-ion batteries comprising the same.
  • the conductive fibers are copper fibers, which are the same as in Example 1.
  • the shape is sheet-like.
  • the thickness of the fibers is 3 ⁇ m, the width is 1 mm, and the distance between adjacent conductive fibers is 2 mm.
  • the projected area ratio of the conductive fibers on the carbon material mold is 33.3%, and the included angle between the projection of the conductive fibers on the carbon material film and the length direction of the carbon current collector is 0°.
  • the mass content of the carbon material refers to the mass percentage content of the carbon material in the total amount of the carbon material and the polymer.
  • Example 6 and Examples 9-11 in Table 2 It can be seen from Example 6 and Examples 9-11 in Table 2 that the mass content of carbon material in the polymer has a certain influence on the strength and resistance of the current collector. As the mass content of carbon material increases, the resistance decreases, but the strength Also decreased, because there is an interface between the carbon material and the polymer, the interface will be slightly peeled off when the polymer is carbonized, resulting in the weakening of the force between the carbon material and the carbonized polymer, and the excessive addition of carbon material will This leads to poor polymer continuity and insufficient internal connection points after carbonization, resulting in reduced tensile strength.
  • Table 3 shows the effect of various parameters of the conductive fibers on the performance of the prepared carbon current collectors and lithium-ion batteries containing the same.
  • the polymer in the polymer solution in Examples 12-30 shown in Table 3 was the same as Example 1 and was PI.
  • the sheet-shaped conductive fibers have better effects than other shapes such as cylindrical shapes, because the sheet-shaped conductive fibers can obtain a current collector with a higher fiber projected area .
  • the increase in the projected area of the fiber is beneficial to improve the tensile strength of the current collector and reduce the internal resistance in the length direction.
  • the thin thickness of the current collector restricts the diameter of cylindrical fibers from being too large, while the manufacture of cylindrical fibers with too small diameters is difficult, and its uniform and dense arrangement is difficult, so it is difficult to prepare Current collectors with high fiber projected area.
  • the carbon current collector has high tensile strength and low internal resistance. If the thickness of the fiber is too thick, the thickness of the current collector will increase, which will affect the volume energy density; if the thickness is too small, the cost and difficulty of fiber fabrication will increase, the tensile strength of the composite current collector will decrease, and the internal resistance will increase.
  • the carbon current collector has high tensile strength and low internal resistance. Too wide fiber width may lead to too much fiber proportion, reducing the advantage of weight energy density; too small width will lead to higher cost and difficulty in making current collectors.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Cell Electrode Carriers And Collectors (AREA)

Abstract

La présente invention concerne un collecteur de courant de carbone, un dispositif électrochimique comprenant ledit collecteur de courant de carbone, et un dispositif électronique. Le collecteur de courant de carbone de la présente invention comprend un film de matériau carboné et des fibres conductrices, les fibres conductrices étant réparties dans le film de matériau carboné dans le sens de la longueur du collecteur de courant de carbone. Le collecteur de courant de carbone de la présente invention présente une résistance à la traction (sens de la longueur des fibres) supérieure et une résistance interne inférieure. Une batterie au lithium-ion qui utilise le collecteur de courant peut avoir une densité d'énergie supérieure et une meilleure performance de débit.
PCT/CN2021/083054 2021-03-25 2021-03-25 Collecteur de courant de carbone, dispositif électrochimique comprenant un collecteur de courant de carbone et dispositif électronique WO2022198583A1 (fr)

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PCT/CN2021/083054 WO2022198583A1 (fr) 2021-03-25 2021-03-25 Collecteur de courant de carbone, dispositif électrochimique comprenant un collecteur de courant de carbone et dispositif électronique
CN202180004872.3A CN114531925B (zh) 2021-03-25 2021-03-25 碳集流体及包括该碳集流体的电化学装置和电子装置

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PCT/CN2021/083054 WO2022198583A1 (fr) 2021-03-25 2021-03-25 Collecteur de courant de carbone, dispositif électrochimique comprenant un collecteur de courant de carbone et dispositif électronique

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WO2024077473A1 (fr) * 2022-10-11 2024-04-18 宁德时代新能源科技股份有限公司 Collecteur de courant et son procédé de fabrication, et plaque d'électrode, batterie secondaire et appareil électrique

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