WO2022198644A1 - Collecteur de courant de carbone poreux et dispositif électrochimique - Google Patents

Collecteur de courant de carbone poreux et dispositif électrochimique Download PDF

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WO2022198644A1
WO2022198644A1 PCT/CN2021/083314 CN2021083314W WO2022198644A1 WO 2022198644 A1 WO2022198644 A1 WO 2022198644A1 CN 2021083314 W CN2021083314 W CN 2021083314W WO 2022198644 A1 WO2022198644 A1 WO 2022198644A1
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Prior art keywords
current collector
porous carbon
carbon current
polymer
porous
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PCT/CN2021/083314
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English (en)
Chinese (zh)
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李志愿
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宁德新能源科技有限公司
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Priority to CN202180002681.3A priority Critical patent/CN114026717B/zh
Priority to PCT/CN2021/083314 priority patent/WO2022198644A1/fr
Publication of WO2022198644A1 publication Critical patent/WO2022198644A1/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
    • H01M4/665—Composites
    • H01M4/666—Composites in the form of mixed materials
    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • 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
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/665—Composites
    • H01M4/667—Composites in the form of layers, e.g. coatings
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present application relates to the field of energy storage, in particular to a porous carbon current collector and an electrochemical device.
  • the current collectors of lithium-ion batteries are mainly copper foil and aluminum foil, which are the heaviest part of the battery except for the positive and negative electrode materials, and the metal material has poor flexibility, so it is not suitable for flexible electrodes.
  • flexible substrates for bendable flexible lithium-ion batteries There are two main types of flexible substrates for bendable flexible lithium-ion batteries:
  • Non-conductive flexible substrates such as polymers, paper, and woven fabrics.
  • Conductive flexible substrate mainly using carbon material films such as graphene or carbon nanotubes as the flexible substrate, and the active material is attached to its structural unit to form a flexible electrode. It has obvious advantages in quality and is the mainstream development direction of flexible batteries with high energy density and light weight.
  • the purpose of the present application is to prepare a porous carbon current collector that can improve the rate performance of a battery, as well as electrochemical devices and electronic devices comprising the porous carbon current collector.
  • the present application provides a porous carbon current collector comprising a carbon material and a polymer, wherein the porous carbon current collector has a porosity of 9% to 60%.
  • the porous carbon current collector satisfies at least one of the following features (1) to (3): (1) the pore size of the porous carbon current collector ranges from 0.02 ⁇ m to 1 ⁇ m; (2) ) the air permeability of the porous carbon current collector is 100s/100cc to 500s/100cc; (3) the volume of pores with a pore size ranging from 0.03 ⁇ m to 0.2 ⁇ m in the porous carbon current collector accounts for 80% of the total pore volume % to 100%.
  • the mass content of the carbon material is 40% to 90%, and the mass content of the polymer is 10% to 60%.
  • the polymer satisfies at least one of the following features (4) to (8): (4) the melting point of the polymer ranges from 130°C to 200°C; (5) the The weight average molecular weight of the polymer ranges from 150,000 to 1,000,000; (6) the melt index of the polymer is 0.3g/10min to 20g/10min; (7) The liquid absorption rate of the polymer in the electrolyte is less than 5%; (8) The film stretch rate of the polymer is -5% to 5%.
  • the thickness of the porous carbon current collector is 3 ⁇ m to 30 ⁇ m.
  • the carbon material includes at least one of conductive carbon black, acetylene black, graphite, graphene, carbon nanotubes, or carbon fibers.
  • the polymer comprises polyethylene, polypropylene, polymethyl methacrylate, polyamide, polyvinyl alcohol, polyoxymethylene, polyimide, ethylene-vinyl acetate copolymer or polyvinylidene At least one of vinyl fluoride.
  • the porous carbon current collector satisfies at least one of the following features (9) to (12): (9) the electrical resistance of the porous carbon current collector is 3 m ⁇ to 100 m ⁇ ; (10) the The strength of the porous carbon current collector is 100MPa to 500MPa; (11) After the porous carbon current collector is baked at 120°C for 15 minutes, the resistance is more than 98% of the initial resistance, and the strength is more than 98% of the initial strength; (12) The elongation of the porous carbon current collector is 2% to 10%.
  • At least one surface of the porous carbon current collector is further provided with a metal layer.
  • the ratio of the projected area of the metal layer on the surface of the porous carbon current collector to the area of the porous carbon current collector is 5% to 70%.
  • the thickness of the metal layer is 0.2 ⁇ m to 2 ⁇ m.
  • the metal in the metal layer includes at least one of copper, aluminum, gold, silver or nickel.
  • the present application provides an electrochemical device comprising the porous carbon current collector as described in the first aspect of the present application.
  • the present application provides an electronic device comprising the electrochemical device according to the second aspect of the present application.
  • the present application provides a porous carbon current collector, the porous carbon current collector includes a carbon material and a polymer, and the porous carbon current collector has a porosity of 9% to 60%.
  • the porous carbon current collector of the present application has a specific porous structure, so that the current collector has a certain liquid retention capacity, overcomes the disadvantage of poor high-power performance of the existing flexible lithium-ion battery, and improves the rate and low-temperature performance of the lithium-ion battery.
  • 1 is a schematic diagram of a current collector according to an embodiment of the present application, wherein 1 represents a carbon material and 2 represents a polymer.
  • FIG. 2 is a SEM image of a cross-section of a current collector according to an embodiment of the present application.
  • a first aspect of the present application provides a porous carbon current collector including a carbon material and a polymer, and the porous carbon current collector has a porosity of 9% to 60%. Porosity is contributed by gaps between polymers or between polymers and carbon materials or between carbon materials and carbon materials.
  • the increase of the porosity of the current collector and the improvement of the liquid retention capacity are beneficial to the improvement of the charge-discharge capacity retention rate and the low-temperature capacity retention rate.
  • the porosity is too high, the mechanical properties of the current collector will deteriorate, resulting in a decrease in its strength, which is not conducive to the subsequent coating cold pressing. and other processing.
  • the carbon material as the current collector can improve the flexibility and energy density of the electrode, and the prepared electrode sheet is suitable for batteries for flexible electronic devices.
  • the porous carbon current collector of the present application has a specific porous structure, so that the current collector has a certain liquid-holding capacity, thereby improving the rate and low-temperature performance of the lithium-ion battery.
  • the porous carbon current collector has a porosity of 10%, 15%, 18%, 25%, 28%, 30%, 35%, 38%, 40%, 45%, 18%, 52% %, 56% or 60%.
  • the porous carbon current collector has a pore size ranging from 0.02 ⁇ m to 1 ⁇ m.
  • the volume of pores with a pore size ranging from 0.03 ⁇ m to 0.2 ⁇ m in the porous carbon current collector is 80% to 100% of the total pore volume, such as 80%, 85%, 90%, 95% %, 98%, etc.
  • the pore size of the porous carbon current collector meets the above range, which can reduce the adverse effect of the existence of the current collector pore structure on the mechanical properties of the current collector.
  • the pore distribution is more uniform. , so that the structure of the current collector is uniform, which further ensures the improvement of the electrical performance, and is also conducive to the improvement of the mechanical performance of the current collector and avoids the poor processing process.
  • the porous carbon current collector has an air permeability of 100s/100cc to 500s/100cc.
  • the porous carbon current collector consists of a carbon material and a polymer.
  • the mass content of the carbon material is 40% to 90% based on the total mass of the porous carbon current collector. Since the polymer does not have electrical conductivity, an increase in the content will increase the resistance of the current collector, which is not conducive to electron conduction, and the polymer content is preferably not more than 60%. In some embodiments, the mass content of the polymer is 10% to 60% based on the total mass of the porous carbon current collector.
  • the polymer has a melting point in the range of 130°C to 200°C. In some embodiments, the polymer has a melting point in the range of 130 to 150°C, 150 to 180°C, or 180 to 200°C.
  • the melting point of the polymer is too low, so that the processing temperature range that the current collector can withstand is limited, which is not conducive to the dimensional stability of the current collector and the fabrication and processing of lithium ion batteries.
  • the melting point of the polymer is too high, which makes it difficult to melt and process the current collector, and is not conducive to the stability of the pore-forming agent added during the current collector manufacturing process.
  • the polymer has a weight average molecular weight in the range of 150,000 to 1 million, such as 150,000, 200,000, 250,000, 300,000, 350,000, 400,000, 450,000, and the like.
  • the molecular weight of the polymer is too low, which will lead to weak intermolecular forces and enhanced molecular chain mobility, thereby reducing the melting point of the polymer, increasing the melt index, decreasing the mechanical properties, and weakening the dimensional stability. It is difficult to ensure the preparation and processing of the current collector itself. Process stability and current collector stability during slurry coating.
  • the molecular weight of the polymer is too large, on the one hand, the synthesis process is difficult, and it is difficult to find a suitable polymer for use; Pore structure.
  • the polymer has a melt index of 0.3g/10min to 20g/10min, eg, 0.3g/10min, 1.0g/10min, 1.5g/10min, 2.0g/10min, 3.0g/10min, 4.0 g/10min, 5.0g/10min, 6g/10min, 10g/10min, etc.
  • the polymer is required to have a certain melt processing capability.
  • the melt index of the polymer reflects the melt processing ability to a certain extent. The higher the melt index, the stronger the flow ability of the polymer at high temperature, and it is difficult to prepare a dimensionally stable composite film. The lower the melt index, the weaker the flow ability of the melt, which is difficult to pass through Melt processing.
  • the polymer has a liquid uptake of less than 5% in the electrolyte.
  • the liquid absorption rate of the polymer in the electrolyte represents the weight change rate after immersing the polymer film (the thickness of the film can be in the range of 10 ⁇ m to 15 ⁇ m) in the electrolyte or the electrolyte solvent,
  • the calculation formula can be (m2-m1)/m1, where m1 represents the weight of the adhesive film before dipping, and m2 represents the weight of the adhesive film after dipping.
  • the immersion time may be 48h-96h (eg 72h), and the immersion temperature may be 70°C-90°C (eg 85°C).
  • the porous structure of the current collector plays a role in retaining liquid during use, and the polymer component in it needs to have a certain resistance to electrolyte to avoid the size change, conductive network structure change, and mechanical properties change of the current collector caused by liquid absorption expansion.
  • the structure of the current collector is kept stable during the use of the cell.
  • the electrolyte solvent used in testing the liquid absorption rate is EC and DMC, and the specific mass ratio may be 1/1.
  • the polymer has a film stretch of -5% to 5%.
  • the stretch rate of the polymer film refers to the change rate of the film length after the polymer film is stretched along the length direction of the film, and the calculation formula can be (L2-L1)/L1, where L1 represents The length of the film before stretching, L2 represents the length of the film after stretching. Since the coating and drying temperature is generally within 90°C to 110°C when the current collector of the present application is used to coat the positive and negative electrode slurry, the current collector should have good dimensional stability within 110°C to avoid coating Process abnormality in processing due to thermal contraction or expansion of the current collector. In some embodiments, the polymer has a film stretch of -5% to 0%.
  • the polymer film stretch is 0% to -5%. Therefore, the film stretch ratio of the polymer is required to be -5% to 5%.
  • the test conditions for the stretch rate of the adhesive film of the polymer include: the temperature is in the range of 90° C. to 110° C., the thickness of the adhesive film is in the range of 10 ⁇ m to 15 ⁇ m, and the stretching is performed with a force of 5g-10g , the stretching time is 10min to 30min.
  • the test conditions for the stretch rate of the adhesive film of the polymer include: the temperature is 110° C., the thickness of the adhesive film is 10 ⁇ m to 15 ⁇ m, the stretching is performed with a force of 5 g, and the stretching time is 20 minutes.
  • the polymer comprises polyethylene, polypropylene, polymethyl methacrylate, polyamide, polyvinyl alcohol, polyoxymethylene, polyimide, ethylene vinyl acetate, polyvinylidene fluoride at least one of.
  • the porous carbon current collector has a thickness of 3 ⁇ m to 30 ⁇ m.
  • the increase in the thickness of the current collector has no effect on the mechanical properties, and the electrolyte retention increases to a certain extent, but has little effect on the performance; considering that the increase in the thickness of the current collector will lose the volumetric energy density, it is preferably not more than 30 ⁇ m.
  • the thickness of the porous carbon current collector is 3 ⁇ m, 8 ⁇ m, 10 ⁇ m, 15 ⁇ m, 20 ⁇ m, 25 ⁇ m, or 30 ⁇ m, or the like.
  • the carbon material includes at least one of conductive carbon black, acetylene black, graphite, graphene, carbon nanotubes, or carbon fibers.
  • the carbon material plays a conductive role, and there are no special requirements for the type.
  • the carbon material preferably has a D50 of 30 nm to 500 nm and a specific surface area of 5 m 2 /g to 300 m 2 /g.
  • the carbon material is a carbon nanotube, preferably, the diameter of the tube is 20 nm to 50 nm, and the tube length is 0.5 ⁇ m to 5 ⁇ m.
  • the carbon material has a specific surface area of 100 m 2 /g to 300 m 2 /g.
  • the electrical resistance of the porous carbon current collector is 3 m ⁇ to 100 m ⁇ .
  • the strength of the porous carbon current collector is 100 MPa to 500 MPa.
  • the resistance is more than 98% of the initial resistance, and the strength is more than 98% of the initial strength.
  • the elongation of the porous carbon current collector is 2% to 10%.
  • At least one surface of the porous carbon current collector is further provided with a metal layer.
  • the metal coating on the surface of the carbon current collector is beneficial to improve its electronic conduction. It can be used in the case of low conductivity of the main material. Considering the influence of thickness and the retention of electrolyte, the coverage should be less than 70% and the thickness should be less than 2 ⁇ m.
  • the ratio of the projected area of the metal layer on the surface of the porous carbon current collector to the area of the porous carbon current collector is 5% to 70% (tested using a KEYENCE VHX5000).
  • the thickness of the metal layer is 0.2 ⁇ m to 2 ⁇ m.
  • the metal in the metal layer includes at least one of copper, aluminum, gold, silver or nickel, and the introduction method may be electroplating, deposition or spraying.
  • the current collector of the present application can be prepared by a conventional melt extraction pore-making method.
  • the melt-extraction pore-forming method includes: casting the carbon material, the polymer, and the pore-forming agent into a conductive composite film by melt extrusion; thermally stretching the conductive composite film; After the conductive composite film is removed.
  • the porosity of the current collector is controlled by changing the content of the pore-forming agent, and the pore distribution is controlled by changing the size of the pore-forming agent.
  • the pore-forming agent used in the present application is not particularly limited, as long as the additive is suitable for forming the pore structure of the polymer in the present application, it can be used in the present application.
  • the pore former is one or more of polyvinyl alcohol and polyethylene glycol.
  • a second aspect of the present application provides an electrochemical device comprising the porous current collector provided by the present application.
  • the porous current collector provided in the present application can be used as the current collector of the positive electrode sheet and the negative electrode sheet.
  • the positive electrode sheet includes the porous current collector provided herein. According to some embodiments, the positive electrode sheet further includes a positive active material disposed on the porous current collector.
  • the positive active material of the present application is not particularly limited, and any positive active material known in the art can be used, for example, it can include nickel cobalt lithium manganate (811, 622, 523, 111), nickel cobalt lithium aluminate, lithium iron phosphate, At least one of lithium-rich manganese-based material, lithium cobaltate, lithium manganate, lithium iron manganese phosphate or lithium titanate.
  • the negative electrode sheet includes the porous current collector provided herein. According to some embodiments, the negative electrode sheet further includes a negative electrode active material disposed on the porous current collector.
  • the negative electrode active material in the present application is not particularly limited, and any negative electrode active material known in the art can be used. For example, at least one of artificial graphite, natural graphite, mesocarbon microspheres, soft carbon, hard carbon, silicon, silicon carbon, lithium titanate, and the like may be included.
  • 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 separator 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.
  • 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.
  • any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with any other lower limit to form an unspecified range, and likewise any upper limit can be combined with any other upper limit to form an unspecified range.
  • each individually disclosed point or single value may itself serve as a lower or upper limit in combination with any other point or single value or with other lower or upper limits to form a range that is not expressly recited.
  • a list of items to which the terms "at least one of,” “at least one of,” “at least one of,” or other similar terms are linked to can mean any combination of the listed items. For example, if items A and B are listed, the phrase “at least one of A and B” means A only; B only; or A and B. In another example, if items A, B, and C are listed, 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 component or multiple components.
  • Item B may contain a single component or multiple components.
  • Item C may contain a single component or multiple components.
  • Thickness of current collector Take a current collector with a length of 40cm and a width of 20cm to ensure that the current collector is flat and wrinkle-free. Use a Mitutoyo micrometer to test the thickness of 12 different positions within this size range, and take the average value.
  • Current collector resistance Take a current collector with a length of 40cm and a width of 20cm to ensure that the current collector is flat and wrinkle-free. Use a BER1300 resistance meter and choose the four-point probe method to test the resistance of 12 different positions within this size range and take the average value.
  • Current collector strength and elongation Take a current collector with a length of 40cm and a width of 20cm to ensure that the current collector is flat and wrinkle-free. Cut it into a spline with a width of 12mm and a length of 100mm along the length direction. Use an Instron3365 universal testing machine and select a tensile fixture for testing. , the distance between the clamps, that is, the length of the test section is 50mm, the tensile rate is 10mm/min, and the average value of 12 test strips is taken to calculate the strength and elongation of the sample when it is broken.
  • Current collector pore structure refer to the standard GB/T 21650 mercury porosimetry and gas adsorption method to determine the pore size distribution and porosity of solid materials. Take three current collector samples with a width of 20mm and a length of 300mm, and weigh them; use an Autopore V 9620 mercury porosimeter for testing, roll up the samples along the length direction and put them into a sample tube for sealing. The volume of the sample tube is V0; The sample tube is placed in a low-pressure chamber for low-pressure mercury filling. When the volume of the sample tube other than the sample is filled with mercury, the volume of the filled mercury is V1. Since the mercury is outside the sample at this time, it is not pressed into the sample.
  • the sample volume is (V0-V1), put the sample tube into the high-pressure chamber for high-pressure mercury filling, so that the mercury enters the hole of the sample, and the total volume of mercury charged into the sample is the pore volume V2 of the sample, and obtain
  • the pore size-volume distribution curve of the current collector, and the pore size range of the current collector corresponds to the pore size distribution range in the pore size-volume distribution curve.
  • the calculation method of porosity is V2/(V0-V1), the cumulative mercury injection volume corresponding to the pressure in the pore size range of 0.03 ⁇ m to 0.2 ⁇ m is the volume V3, and the volume of the pores in the pore size range of 0.03 ⁇ m to 0.2 ⁇ m accounts for the total pore volume. Percent V3/V2.
  • the test values are all obtained by taking the average value of 3 samples.
  • Air permeability of current collectors refer to the standard GB/T 458-2008 Determination of air permeability of paper and cardboard. Take 12 pieces of current collectors with a size of 5cm ⁇ 5cm to ensure that the current collectors are flat without wrinkling and damage. Use a Gurley 4110C air permeability tester to test to ensure that the current collector covers all the discs to be tested, test 100cc of gas for the time of the current collector, and take the average value of 12 pieces of current collectors as the air permeability.
  • Coverage of metal coating Take 12 pieces of current collector samples with a size of 10mm ⁇ 10mm, use KEYENCE VHX5000 to test, the magnification is 500 times, the automatic measurement area mode calculates the coverage, and takes the average value of 12 pieces.
  • Thickness of metal coating Take 12 pieces of current collectors, size 10mm ⁇ 10mm, use IB-09010CP to cut the cross-section, use SIGMA/X-max field emission scanning electron microscope to test the thickness of metal coating on the cross-section of 12 pieces of current collector, select each piece 3 positions, take the average of all data.
  • the stretch rate of the polymer film prepare the polymer into a film with a thickness of 10 ⁇ m to 15 ⁇ m, cut it into a spline with a width of 8mm and a length of 40mm to 50mm, and use the DMA850 of TA Instruments to test, the test mode is stretching , place the spline in the tensile jig, adjust the upper and lower distance of the jig to be the length of the sample, the length is between 15mm and 15.5mm, denoted as L1, raise the test furnace to 110°C at a heating rate of 10°C/min, and measure the length of the sample along the Apply 5g force in the stretching direction, record the change of the sample length, after 20min, the sample length is L2, and the tensile ratio of the film is calculated: (L2-L1)/L1.
  • 1.5C charging capacity retention rate at 25°C, the cell with SOC of 0% is charged to 100% SOC with 0.2C constant current, and constant voltage is charged to 0.05C, the charging capacity is C0, and the 0.5C DC discharge is to 0% SOC, 1.5C constant current charging to 100% SOC, charging capacity is C1, C1/C0.
  • 2C discharge capacity retention rate at 25°C, the cell with SOC of 0% is charged to 100% SOC with 0.2C constant current, constant voltage charged to 0.05V, 0.2C DC discharge to 0% SOC, the discharge capacity is D0, 0.2 C constant current charge to 100% SOC, constant voltage charge to 0.05V, 2C DC discharge to 0% SOC, the discharge capacity is D1, D1/D0.
  • -20°C_0.5C capacity retention rate at 25°C, charge the cell with SOC of 0% to 100% SOC with 0.2C constant current, charge to 0.05V with constant voltage, and discharge 0.5C DC to 0% SOC, the discharge capacity It is D0; at 25°C, the cell with SOC of 0% is charged to 100% SOC with 0.2C constant current, charged to 0.05V with constant voltage, and discharged to 0% SOC with 0.5C DC at -20°C, and the discharge capacity is D1 , D1/D0.
  • Carbon materials used in the examples and comparative examples carbon nanotubes: the diameter of the tube is 20-50 nm, the tube length is 0.5-5 ⁇ m, and the specific surface area is 200 m 2 /g.
  • Polyethylene high density polyethylene, the melting point is 142°C, the molecular weight is 200,000, the melt index is 3g/10min (200°C/21.6Kg), the liquid absorption rate is 0.2%, and the film stretch rate is -2.5%.
  • Polypropylene isotactic polypropylene, the melting point is 170°C, the molecular weight is 300,000, the melt index is 1g/10min (200°C/21.6Kg), the liquid absorption rate is 0.2%, and the film stretch rate is -1.5%.
  • Polyimide melting point 194°C, molecular weight 400,000, melt index 0.5g/10min (200°C/21.6Kg), liquid absorption rate 0.3%, film stretch rate 0.8%.
  • Polyoxymethylene melting point is 185°C, molecular weight is 340,000, melt index is 0.7g/10min (200°C/21.6Kg), liquid absorption rate is 1%, and film stretch rate is 1.1%.
  • Ethylene-vinyl acetate copolymer melting point 155°C, molecular weight 370,000, melt index 1.9g/10min (200°C/21.6Kg), liquid absorption 0.3%, film stretch rate -2.4%.
  • Carbon nanotubes, polyethylene and pore-forming agent polyvinyl alcohol (polymerization degree 400-500, alcoholysis degree 88%) are cast into conductive composite films by melt extrusion, wherein the mass ratio of carbon nanotubes and polyethylene is 30 /70.
  • the conductive composite membrane is thermally stretched to a target thickness, and the membrane is placed in a solvent to wash away the pore-forming agent and dry to obtain a porous carbon current collector.
  • the porosity of the porous carbon current collector prepared in this example is 38.2%, the proportion of pores of 0.03-0.2 ⁇ m is 89.5%, and the thickness is 5 ⁇ m.
  • the positive active material lithium cobaltate, acetylene black, and polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 94:3:3, and then N-methylpyrrolidone (NMP) was added as a solvent to prepare a solid content of 75%. slurry and mix well.
  • the slurry was uniformly coated on the above-mentioned porous carbon current collector, dried at 90°C, and cold-pressed to obtain a positive electrode sheet with a positive active material layer thickness of 100 ⁇ m, and then repeat the above on the other surface of the positive electrode sheet step to obtain a positive electrode sheet coated with a positive electrode active material layer on both sides. Cut the positive pole piece into a size of 74mm ⁇ 867mm and weld the tabs for later use.
  • the negative active materials artificial graphite, acetylene black, styrene-butadiene rubber and sodium carboxymethyl cellulose are mixed in a mass ratio of 96:1:1.5:1.5, and then deionized water is added as a solvent to prepare a slurry with a solid content of 70% , and stir well.
  • the slurry was uniformly coated on the above-mentioned porous carbon current collector, dried at 110°C, and after cold pressing, a negative electrode pole piece with a negative electrode active material layer thickness of 150 ⁇ m was obtained on one side coated with a negative electrode active material layer, and then the negative electrode was placed on the negative electrode.
  • the above coating steps are repeated on the other surface of the pole piece to obtain a negative pole piece coated with a negative electrode active material layer on both sides. Cut the negative pole piece into a size of 74mm ⁇ 867mm and weld the tabs for later use.
  • the non-aqueous organic solvents ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), propyl propionate (PP), vinylene carbonate ( VC) is mixed according to the mass ratio of 20:30:20:28:2, then lithium hexafluorophosphate (LiPF 6 ) is added to the non-aqueous organic solvent to dissolve and mix uniformly to obtain an electrolyte, wherein the mass ratio of LiPF 6 to the non-aqueous organic solvent to 8:92.
  • LiPF 6 lithium hexafluorophosphate
  • the above-prepared positive pole piece, separator, and negative pole piece are stacked in order, the side of the separator with the first coating is in contact with the positive pole piece, and the side of the separator with the second coating is in contact with the negative pole piece , and rolled to obtain an electrode assembly.
  • the electrode assembly is put into an aluminum-plastic film packaging bag, and the moisture is removed at 80 ° C, the prepared electrolyte is injected, and the lithium ion battery is obtained through vacuum packaging, standing, forming, and shaping.
  • Example 2 the difference from Example 1 is that the porosity of the current collector is adjusted, and the parameter changes are shown in Table 2.
  • Example 1 The difference from Example 1 is that the copper foil is used as the negative electrode current collector, the aluminum foil is used as the positive electrode current collector, and other conditions are the same.
  • the porosity of the current collector increases (from 9.7% to 58.7%), and the liquid retention capacity improves, which is beneficial to the improvement of the charge-discharge capacity retention rate and the low-temperature capacity retention rate; however, the increase of the current collector porosity is not enough. It is beneficial to liquid retention, but at the same time, it will deteriorate the mechanical properties and cause its strength to decrease. When the porosity exceeds 60%, it is not conducive to the subsequent processing such as coating and cold pressing.
  • Example 1 the difference from Example 1 is that the pore volume of the current collector is adjusted. See Table 2 for parameter changes.
  • the existence of the current collector pore structure will cause a certain decline in the mechanical properties of the current collector, which can be reduced from the perspective of pore size distribution.
  • the smaller pores with larger pores have a greater impact on the strength, and the proportion should be reduced.
  • the proportion of small pores of 0.03 to 0.2 ⁇ m is preferably not low. at 80%. It can be seen from Table 2 that the uniform pore distribution has no effect on the air permeability and resistance, but it is conducive to the uniform structure of the current collector, which further ensures the improvement of the electrical performance; the uniform distribution of the pores is conducive to the improvement of the mechanical performance of the current collector and avoids poor processing.
  • Example 1 the difference from Example 1 is that the type of polymer is adjusted, and the parameter changes are shown in Table 3.
  • Example 1 the difference from Example 1 is that the polymer content, that is, the polyethylene content, is adjusted, and the parameter changes are shown in Table 4.
  • the increase of the polymer content is beneficial to the improvement of mechanical properties, but since the polymer does not have electrical conductivity, the increase of the content also increases the resistance of the current collector, which is not conducive to electron conduction. Therefore, the polymer content is preferably not more than 60 %.
  • Example 1 the difference from Example 1 is that the thickness of the current collector is adjusted, and the parameter changes are shown in Table 5.
  • the increase in the thickness of the current collector has basically no effect on the mechanical properties, and the electrolyte retention increases to a certain extent, but has little effect on the performance; however, the increase in the thickness of the current collector will lose the volumetric energy density, preferably not more than 30 ⁇ m.
  • Example 1 the difference from Example 1 is that metal coating is applied on the surface of the current collector or the main material of the negative electrode is changed, and the parameter changes are shown in Table 6.
  • Adding a metal coating on the surface of the carbon current collector can increase its electronic conduction.
  • the introduction of a metal coating on the surface of the current collector is beneficial to the performance improvement. Therefore, the metal coating can be introduced when the electrical conductivity of the main material is low.
  • the coverage of the metal coating is preferably ⁇ 70%, and the thickness is ⁇ 2 ⁇ m.

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Abstract

L'invention concerne un collecteur de courant de carbone poreux et un dispositif électrochimique. Le collecteur de courant de carbone poreux comprend un matériau carboné (1) et un polymère (2), et la porosité du collecteur de courant de carbone poreux est de 9 % à 60 %. L'invention concerne également un dispositif électrochimique. Le dispositif électrochimique comprend le collecteur de courant de carbone poreux. Le collecteur de courant de carbone poreux peut améliorer les performances de la batterie.
PCT/CN2021/083314 2021-03-26 2021-03-26 Collecteur de courant de carbone poreux et dispositif électrochimique WO2022198644A1 (fr)

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US4554063A (en) * 1983-05-06 1985-11-19 Bbc Brown, Boveri & Company Limited Cathodic, gas- and liquid-permeable current collector
US5972538A (en) * 1996-05-17 1999-10-26 Nisshinbo Industries, Inc. Current collector for molten salt battery, process for producing material for said current collector, and molten salt battery using said current collector
CN108137842A (zh) * 2015-10-30 2018-06-08 宇部兴产株式会社 多孔膜以及蓄电装置
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