WO2023115563A1 - 电化学装置和电子装置 - Google Patents

电化学装置和电子装置 Download PDF

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WO2023115563A1
WO2023115563A1 PCT/CN2021/141317 CN2021141317W WO2023115563A1 WO 2023115563 A1 WO2023115563 A1 WO 2023115563A1 CN 2021141317 W CN2021141317 W CN 2021141317W WO 2023115563 A1 WO2023115563 A1 WO 2023115563A1
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negative electrode
silicon
electrochemical device
electrode sheet
active material
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PCT/CN2021/141317
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English (en)
French (fr)
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廖群超
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宁德新能源科技有限公司
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Priority to PCT/CN2021/141317 priority Critical patent/WO2023115563A1/zh
Priority to CN202180031196.9A priority patent/CN115516665A/zh
Publication of WO2023115563A1 publication Critical patent/WO2023115563A1/zh
Priority to US18/751,884 priority patent/US20240347694A1/en

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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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • 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
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • 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
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • 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
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • 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 electrochemical energy storage, in particular to electrochemical devices and electronic devices.
  • Some embodiments of the present application provide an electrochemical device, the electrochemical device includes a negative electrode sheet, the negative electrode sheet includes a negative electrode active material layer, the negative electrode active material layer includes silicon-based material particles and a binder, and the negative electrode sheet satisfies: (B+C)/7 ⁇ A ⁇ (B+C)/1.8, wherein, A represents the weight loss rate in mass percent when the negative electrode active material layer of the negative pole sheet is heated to 480°C under Ar atmosphere; B represents The relative percentage content fluctuation value of the silicon element in the silicon-based material particles; C represents the content of the silicon element in the negative electrode sheet in mass percent.
  • A represents the weight loss rate in mass percent when the negative electrode active material layer of the negative pole sheet is heated to 480°C under Ar atmosphere
  • B represents The relative percentage content fluctuation value of the silicon element in the silicon-based material particles
  • C represents the content of the silicon element in the negative electrode sheet in mass percent.
  • the weight loss rate A of the negative electrode active material layer of the negative electrode sheet when heated to 480° C. under Ar atmosphere satisfies: 1.5% ⁇ A ⁇ 18%. If the value of A is too large, it indicates that there are too many binders in the negative electrode active material layer, which will inhibit the transmission of lithium ions, increase the polarization of the electrochemical device, and deteriorate the rate performance of the electrochemical device; if the value of A is too high If is small, it indicates that there is too little binder in the negative electrode active material layer, which is not conducive to alleviating the volume expansion of the silicon-based material during cycling and deteriorating the cycle performance of the electrochemical device.
  • the relative percentage content fluctuation value B of the silicon element in the silicon-based material particle satisfies: B ⁇ 16%. If B is too large, it indicates that the homogeneity of the silicon element is poor, which is not conducive to the improvement of the cycle performance and expansion performance of the electrochemical device.
  • the content C of the silicon element in the negative electrode sheet satisfies: 1% ⁇ C ⁇ 20%. If the value of C is too large, the silicon-based material will expand too much during the cycle, which is not conducive to the improvement of the cycle performance of the electrochemical device; if the value of C is too small, it is not conducive to the improvement of the energy density of the electrochemical device.
  • the porosity P of the negative electrode sheet and the mass percentage C of the silicon element in the negative electrode sheet satisfy: P ⁇ 15 ⁇ C 1/4 .
  • the mass percentage content C of the silicon element in the negative electrode sheet is greater, more pores are needed to alleviate the expansion of the silicon-based material.
  • P ⁇ 15 ⁇ C 1/4 is satisfied, the volume expansion of silicon-based materials can be effectively alleviated.
  • the porosity P of the negative electrode sheet satisfies: 18% ⁇ P ⁇ 40%.
  • the porosity of the negative electrode sheet is too low, the electrolyte is difficult to fully infiltrate, which increases the transmission distance of lithium ions, deteriorates the kinetic performance of the electrochemical device, and is not conducive to alleviating the expansion of silicon-based materials during cycling.
  • the porosity of the negative electrode sheet is too large, it is not conducive to the improvement of the energy density of the electrochemical device.
  • the electrochemical device also includes an electrolyte, including fluoroethylene carbonate in the electrolyte, and the content X of the fluoroethylene carbonate in mass percent and the mass percentage of the silicon element in the negative pole piece
  • the content C in units of percentage satisfies: X ⁇ C.
  • the content X of fluoroethylene carbonate in mass percent satisfies: 2% ⁇ X ⁇ 20%.
  • the value of X is too small, the improvement effect of fluoroethylene carbonate on the cycle performance of the electrochemical device is relatively limited; when the value of X is too large, it indicates that the FEC content is too high, and too much FEC will reduce the lithium in the electrolyte.
  • the mobility of ions affects the rate performance of electrochemical devices.
  • the silicon-based material particles include silicon and carbon.
  • An embodiment of the present application also provides an electronic device, including the above-mentioned electrochemical device.
  • the expansion of the silicon-based material can be limited to the range that the pole piece can bear Internally, the expansion and deformation performance of the electrochemical device is significantly improved; from the material level, the lithium intercalation expansion of the silicon-based material is reduced, the repeated generation and destruction of SEI on the surface of the silicon-based particle is reduced, and the cycle performance and rate performance of the electrochemical device are significantly improved.
  • the electrochemical device includes a negative electrode sheet.
  • the negative electrode sheet includes a negative electrode active material layer
  • the negative electrode active material layer includes silicon-based material particles and a binder.
  • the binder can bind the silicon-based material particles together, reducing the degree of expansion and contraction of the silicon-based material particles during cycling.
  • the negative electrode sheet satisfies: (B+C)/7 ⁇ A ⁇ (B+C)/1.8, wherein A represents that the negative electrode active material layer of the negative electrode sheet is heated to 480° C. under an Ar atmosphere Weight loss rate in mass percentage; B represents the relative percentage content fluctuation value of silicon element in silicon-based material particles; C represents the content of silicon element in negative electrode sheet in mass percentage.
  • the value of A can reflect the content of binder to a certain extent, the larger A is, the amount of binder in the negative electrode active material layer is more, the smaller A is, the binder in the negative electrode active material layer The less the amount of binder.
  • the fluctuation value of the relative percentage content of the silicon element in the silicon-based material particles indicates the uniformity of the distribution of the silicon element, and the larger the fluctuation value, the worse the uniformity.
  • the distribution uniformity of silicon has a significant correlation with the cycle performance and expansion performance of the electrochemical device. The higher the uniformity, the more conducive to reducing the stress caused by the expansion of lithium-ion batteries, and the better the cycle performance and expansion performance of the electrochemical device.
  • the energy density of the electrochemical device can be increased accordingly.
  • the negative electrode sheet satisfy (B+C)/7 ⁇ A ⁇ (B+C)/1.8, the cycle performance, rate performance and expansion performance of the electrochemical device can be significantly improved.
  • the weight loss rate A of the negative electrode active material layer of the negative electrode sheet when heated to 480° C. under Ar atmosphere satisfies: 1.5% ⁇ A ⁇ 18%. If the value of A is too large, it indicates that there are too many binders in the negative electrode active material layer, which will inhibit the transmission of lithium ions, increase the polarization of the electrochemical device, and deteriorate the rate performance of the electrochemical device; if the value of A is too high If is small, it indicates that there is too little binder in the negative electrode active material layer, which is not conducive to alleviating the volume expansion of the silicon-based material during cycling and deteriorating the cycle performance of the electrochemical device. In some embodiments, A may be 1.5%, 5%, 8%, 12%, 15%, 18%, or any other suitable value.
  • the relative percentage content fluctuation value B of the silicon element in the silicon-based material particle satisfies: B ⁇ 16%. If B is too large, it indicates that the homogeneity of the silicon element is poor, which is not conducive to the improvement of the cycle performance and expansion performance of the electrochemical device. In some embodiments, B may be a value of 15%, 10%, 8%, 5% or less.
  • the content C of the silicon element in the negative electrode sheet satisfies: 1% ⁇ C ⁇ 20%.
  • C may be 1%, 5%, 10%, 15%, 20%, or any other suitable value.
  • the porosity P of the negative electrode sheet and the mass percentage C of the silicon element in the negative electrode sheet satisfy: P ⁇ 15 ⁇ C 1/4 .
  • the volume expansion of silicon-based material particles is about 300% after lithium intercalation at room temperature. The huge volume expansion effect can easily lead to problems such as demoulding and powder dropping of the negative electrode sheet. Reserving a certain amount of pores in the negative electrode sheet can effectively alleviate the problem of silicon-based materials. Volume expansion. When the mass percentage content C of the silicon element in the negative electrode sheet is greater, more pores are needed to ease the expansion of the silicon-based material. When P ⁇ 15 ⁇ C 1/4 is satisfied, the volume expansion of silicon-based materials can be effectively alleviated.
  • the porosity P of the negative electrode sheet satisfies: 18% ⁇ P ⁇ 40%.
  • the porosity of the negative electrode sheet is too low, the electrolyte is difficult to fully infiltrate, which increases the transmission distance of lithium ions, deteriorates the kinetic performance of the electrochemical device, and is not conducive to alleviating the expansion of silicon-based materials during cycling.
  • the porosity of the negative electrode sheet is too large, it is not conducive to the improvement of the energy density and kinetic performance of the electrochemical device.
  • the electrochemical device further includes an electrolyte solution, which will be reduced at the negative electrode sheet to generate an SEI layer on the surface of the negative electrode active material to stabilize the interface and delay the continuous consumption of reversible lithium. If the SEI is too thin, it is easy to break during the expansion of the negative electrode active material particles, forming a new interface and deteriorating the cycle performance of the electrochemical device; if the SEI is too thick, the rate of charge transfer will be reduced and the rate performance of the electrochemical device will be deteriorated.
  • fluoroethylene carbonate is included in the electrolyte, and the content X in mass percent of fluoroethylene carbonate and the content C in mass percent of the silicon element in the negative pole sheet satisfy: X ⁇ C.
  • Fluoroethylene carbonate is an important film-forming additive in the electrolyte.
  • the SEI generated by decomposition during the cycle isolates the further contact between the negative electrode active material and the electrolyte, reduces the consumption of lithium ions, and improves the cycle performance.
  • the content of FEC in the electrolyte is greater than or equal to the content of silicon in the negative electrode sheet, the cycle performance, expansion performance and rate performance of the electrochemical device are better.
  • the content X of fluoroethylene carbonate in mass percent satisfies: 2% ⁇ X ⁇ 20%.
  • the value of X is too small, the improvement effect of fluoroethylene carbonate on the cycle performance of the electrochemical device is relatively limited; when the value of X is too large, it indicates that the FEC content is too high, and too much FEC will reduce the lithium in the electrolyte.
  • the mobility of ions affects the rate performance of electrochemical devices.
  • X may be 2%, 5%, 10%, 12%, 15%, 20%, or other suitable values.
  • the silicon-based material particles include elemental silicon and elemental carbon, eg, silicon-carbon compounds or composites, eg, SiC.
  • the preparation method of the silicon-based material can adopt the following preparation method: the porous carbon matrix is placed in a rotary furnace, and the furnace tube is purged with nitrogen for 20 to 40 minutes at room temperature, and then the porous carbon matrix sample is The temperature is increased to 450°C to 500°C.
  • the nitrogen flow rate was adjusted so that the gas residence time in the rotary kiln was at least 90 seconds and maintained at this flow rate for about 30 minutes. Then the gas supply is switched from nitrogen to a mixed gas of silicon-containing gas and nitrogen (the volume fraction of silicon-containing gas in the mixed gas is 5% to 30%).
  • the porous carbon matrix may be selected from at least one of hard carbon, soft carbon, and graphite.
  • the aforementioned hard carbon may include resinous carbon, carbon black, organic polymer pyrolytic carbon, and combinations thereof.
  • the aforementioned soft carbon may include carbon fibers, carbon microspheres, and combinations thereof.
  • the particle size of the porous carbon matrix is not limited, as long as the purpose of the present application can be achieved.
  • the particle size range of the porous carbon matrix is 3 ⁇ m ⁇ Dv50 ⁇ 15 ⁇ m.
  • the weight loss rate A of the negative electrode active material layer of the negative electrode sheet when heated to 480 ° C under the Ar atmosphere is related to the content of the binder in the negative electrode active material layer, for example, the more the binder in the negative electrode active material layer. , the larger A is, the smaller the amount of binder in the negative electrode active material layer is, and the smaller A is. Based on this, A can be adjusted by adjusting the amount of binder.
  • the relative percentage content fluctuation value B of the silicon element in the silicon-based material particles is related to the uniformity and size of the pore distribution inside the carbon matrix, for example, the more uniform the pore distribution inside the carbon matrix, the smaller B is. Based on this, B can be adjusted by adjusting the pore distribution and pore size.
  • the mass percent content C of the silicon element in the negative pole sheet is related to the addition amount of the silicon-based material in the negative electrode active material layer, wherein, the silicon content deposited inside the silicon-based material can be controlled by adjusting the deposition temperature, the deposition time and the use of silicon-containing gas For example, C generally increases with the increase of the deposition temperature, C generally increases with the increase of the deposition time, and C generally increases with the concentration of the silicon-containing gas. Based on this, the mass content C of the silicon element in the negative electrode material layer can be adjusted.
  • the porosity of the negative electrode sheet usually decreases with the increase of the compaction density of the negative electrode sheet. Based on this, the compaction density of the negative electrode sheet can be adjusted by adjusting the cold pressing pressure of the negative electrode sheet, thereby adjusting the porosity of the negative electrode sheet Rate.
  • the binder in the negative active material layer may include carboxymethylcellulose (CMC), polyacrylic acid, polyvinylpyrrolidone, polyaniline, polyimide, polyamideimide, polysilicon At least one of oxane, styrene-butadiene rubber, epoxy resin, polyester resin, polyurethane resin or polyfluorene.
  • CMC carboxymethylcellulose
  • polyacrylic acid polyvinylpyrrolidone
  • polyaniline polyimide
  • polyamideimide polyamideimide
  • polysilicon At least one of oxane, styrene-butadiene rubber, epoxy resin, polyester resin, polyurethane resin or polyfluorene.
  • the electrochemical device may include an electrode assembly including a positive pole piece, a negative pole piece, and a separator disposed between the positive pole piece and the negative pole piece.
  • the negative electrode sheet further includes a negative electrode current collector.
  • the negative active material layer may be located on one side or both sides of the negative current collector.
  • a conductive agent may also be included in the negative electrode active material layer.
  • the conductive agent in the negative electrode active material layer may include at least one of nano-conductive carbon black, carbon nanotubes, carbon fibers, flake graphite, graphene, or Ketjen Black.
  • the negative electrode active material layer may further include negative electrode active material graphite, that is, the negative electrode active material layer may include silicon-based materials and graphite as negative electrode active materials.
  • the mass ratio of the negative active material, the conductive agent and the binder in the negative active material layer may be (78 to 98.5):(0.1 to 10):(0.1 to 10). It should be understood that the above description is only an example, and any other suitable materials and mass ratios may be used.
  • the negative electrode current collector may use at least one of copper foil, nickel foil, or carbon-based current collector.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector, and the positive electrode active material layer may include a positive electrode active material.
  • the positive electrode active material includes lithium cobaltate, lithium iron phosphate, lithium manganese iron phosphate, sodium iron phosphate, lithium vanadium phosphate, sodium vanadium phosphate, lithium vanadyl phosphate, sodium vanadyl phosphate, lithium vanadate, manganese Lithium oxide, lithium nickelate, lithium nickel cobalt manganese oxide, lithium-rich manganese-based materials or lithium nickel cobalt aluminate.
  • the positive active material layer may further include a conductive agent.
  • the conductive agent in the positive electrode active material layer may include at least one of conductive carbon black, Ketjen black, flake graphite, graphene, carbon nanotubes, or carbon fibers.
  • the positive electrode active material layer can also include a binder, and the binder in the positive electrode active material layer can include carboxymethylcellulose (CMC), polyacrylic acid, polyvinylpyrrolidone, polyaniline, polyamide At least one of imine, polyamideimide, polysiloxane, styrene-butadiene rubber, epoxy resin, polyester resin, polyurethane resin or polyfluorene.
  • CMC carboxymethylcellulose
  • the mass ratio of the positive active material, the conductive agent and the binder in the positive active material layer may be (80 to 99):(0.1 to 10):(0.1 to 10).
  • the positive active material layer may have a thickness of 10 ⁇ m to 500 ⁇ m. It should be understood that the above description is only an example, and any other suitable material, thickness and mass ratio may be used for the positive electrode active material layer.
  • Al foil may be used as the positive current collector, and of course, other current collectors commonly used in the art may also be used.
  • the positive electrode collector may have a thickness of 1 ⁇ m to 50 ⁇ m.
  • the positive active material layer may be coated only on a partial area of the current collector of the positive electrode.
  • the isolation film includes at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, or aramid.
  • polyethylene includes at least one selected from high-density polyethylene, low-density polyethylene, or ultra-high molecular weight polyethylene.
  • the thickness of the isolation film is in the range of about 3 ⁇ m to 20 ⁇ m.
  • the surface of the isolation membrane may also include a porous layer, the porous layer is arranged on at least one surface of the isolation membrane, the porous layer includes inorganic particles and a binder, and the inorganic particles are selected from alumina (Al 2 O 3 ), Silicon oxide (SiO 2 ), magnesium oxide (MgO), titanium oxide (TiO 2 ), hafnium oxide (HfO 2 ), tin oxide (SnO 2 ), cerium oxide (CeO 2 ), nickel oxide (NiO), oxide Zinc (ZnO), calcium oxide (CaO), zirconia (ZrO 2 ), yttrium oxide (Y 2 O 3 ), silicon carbide (SiC), boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide or sulfuric acid at least one of barium.
  • alumina Al 2 O 3
  • Silicon oxide SiO 2
  • magnesium oxide MgO
  • titanium oxide TiO 2
  • hafnium oxide HfO 2
  • the pores of the isolation membrane have a diameter in the range of about 0.01 ⁇ m to 1 ⁇ m.
  • the binder of the porous layer is selected from polyvinylidene fluoride, copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, poly At least one of vinylpyrrolidone, polyvinyl ether, polymethylmethacrylate, polytetrafluoroethylene or polyhexafluoropropylene.
  • the porous layer on the surface of the separator can improve the heat resistance, oxidation resistance and electrolyte wettability of the separator, and enhance the adhesion between the separator and the pole piece.
  • the electrolyte solution further includes a lithium salt
  • the lithium salt may include LiPF 6 , LiBF 4 , LiAsF 6 , LiClO 4 , LiB(C 6 H 5 ) 4 , LiCH 3 SO 3 , LiCF 3 SO 3 , LiN( At least one of SO 2 CF 3 ) 2 , LiC(SO 2 CF 3 ) 3 , LiSiF 6 , LiBOB or lithium difluoroborate.
  • the lithium salt comprises LiPF 6 .
  • the electrolyte solution may also include a non-aqueous solvent.
  • the non-aqueous solvent can be carbonate compound, carboxylate compound, ether compound, other organic solvent or their combination.
  • the carbonate compound can be a chain carbonate compound, a cyclic carbonate compound, a fluorocarbonate compound or a combination thereof. Examples of chain carbonate compounds are diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methyl carbonate Ethyl esters (MEC) and combinations thereof.
  • DEC diethyl carbonate
  • DMC dimethyl carbonate
  • DPC dipropyl carbonate
  • MPC methylpropyl carbonate
  • EPC ethylpropyl carbonate
  • MEC methyl carbonate Ethyl esters
  • Examples of the cyclic carbonate compound are ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylethylene carbonate (VEC), or combinations thereof.
  • Examples of the fluorocarbonate compound are 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1, 2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate ester, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate, or combinations thereof.
  • carboxylate compounds are methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, ⁇ -butyrolactone, decanolactone, Valerolactone, mevalonolactone, caprolactone, methyl formate, or combinations thereof.
  • ether compounds are dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxy ethyl ethane, 2-methyltetrahydrofuran, tetrahydrofuran or a combination thereof.
  • organic solvents examples include dimethylsulfoxide, 1,2-dioxolane, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, methyl Amide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate or combinations thereof.
  • the content of the non-aqueous solvent is not particularly limited, as long as the purpose of the application can be achieved, for example, the mass percentage of the above-mentioned other non-aqueous solvents is 67% to 86%, such as 67%, 67.5%, 70% , 75%, 80%, 83%, 85%, 85.5%, 86%, or any range therebetween.
  • the electrochemical device includes a lithium-ion battery, although the present application is not limited thereto.
  • the electrode assembly of the electrochemical device is a wound electrode assembly, a stacked electrode assembly or a folded electrode assembly.
  • the positive pole piece and/or the negative pole piece of the electrochemical device can be a multilayer structure formed by winding or stacking, or a single-layer structure in which a single-layer positive electrode, a separator, and a single-layer negative electrode are stacked. .
  • the positive electrode sheet, separator, and negative electrode sheet are wound or stacked in order to form an electrode assembly, and then packed into an aluminum-plastic film for packaging, and injected with electrolytic Liquid, formed, packaged, that is, made into a lithium-ion battery. Then, performance tests were performed on the prepared lithium-ion batteries.
  • Embodiments of the present application also provide an electronic device including the above electrochemical device.
  • the electronic device in the embodiment of the present application is not particularly limited, and it may be used in any electronic device known in the prior art.
  • electronic devices may include, but are not limited to, notebook computers, pen-based computers, mobile computers, e-book players, cellular phones, portable fax machines, portable copiers, portable printers, headsets, VCRs, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic organizers, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles, bicycles, Lighting appliances, toys, game consoles, clocks, electric tools, flashlights, cameras, large household storage batteries and lithium-ion capacitors, etc.
  • Preparation of the positive electrode sheet mix the positive active material lithium cobaltate, conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) according to a weight ratio of 97:1.4:1.6, and add N-methylpyrrolidone (NMP) As a solvent, stir well.
  • the slurry solid content is 72wt%) is uniformly coated on the aluminum foil of the positive electrode current collector with a coating thickness of 80 ⁇ m, dried at 85°C, and then cold-pressed, cut into pieces, and slit, and vacuum-coated at 85°C Drying under the same conditions for 4 hours to obtain a positive electrode sheet.
  • the negative electrode sheet the silicon-based material prepared above, artificial graphite, binder polyacrylic acid and sodium carboxymethylcellulose (CMC) were dissolved in deionized water at a ratio of 5.7:91.8:1:1.5 by weight , Form negative electrode slurry (solid content is 40wt%). Copper foil with a thickness of 10 ⁇ m was used as the negative electrode current collector, and the negative electrode slurry was coated on the negative electrode current collector with a coating thickness of 50 ⁇ m, dried at 85 ° C, and then cold-pressed, cut into pieces, and cut at 120 °C under vacuum conditions for 12 hours to obtain a negative electrode sheet.
  • CMC carboxymethylcellulose
  • the isolation membrane is polyethylene (PE) with a thickness of 7 ⁇ m.
  • EC ethylene carbonate
  • PC propylene carbonate
  • DEC diethyl carbonate
  • Lithium-ion battery preparation stack the positive pole piece, the separator, and the negative pole piece in order, so that the separator is in the middle of the positive electrode and the negative pole to play the role of isolation, and wind up to obtain the electrode assembly.
  • the electrode assembly is placed in the outer packaging aluminum-plastic film, after dehydration at 80°C, the above electrolyte is injected and packaged, and the lithium-ion battery is obtained through chemical formation, degassing, trimming and other processes.
  • test of silicon element content in the negative pole piece place the negative pole piece in a vacuum oven at 100°C and dry for 24 hours, scrape off part of the active material layer on the negative pole piece with a blade and weigh it to obtain the mass M1, and then scrape off the active material layer to obtain the mass M1.
  • the material layer is heat-treated at 800°C in a continuous air atmosphere to remove the carbonaceous material, and the remaining material is weighed to obtain the mass M2.
  • Fluctuation value test of the relative percentage content of silicon element in silicon-based material particles place the pole piece in a vacuum oven at 100°C to dry for 24 hours, and in a protective atmosphere, use focused ion beam (FIB) to concentrate the silicon in the pole piece
  • the base material particles are processed into thin slices of 50-100nm, and then the relative percentage of silicon atoms in the silicon-based particles is tested by X-ray energy spectrometer (EDS) in the transmission electron microscope (TEM) equipment.
  • EDS X-ray energy spectrometer
  • TEM transmission electron microscope
  • Fluoroethylene carbonate (FEC) content test in the electrolyte the electrochemical device was discharged to 0% state of charge (SOC) and then centrifuged, and the liquid obtained after centrifugation was tested by GC-MS, and the FEC group was detected points percentage.
  • SOC state of charge
  • Rate performance test at 25°C, discharge at 0.2C to 3.0V, let stand for 5 minutes, charge at 0.5C to 4.45V, charge at constant voltage to 0.05C and let stand for 5 minutes, then adjust the discharge rate to 0.2C and 2.0C for discharge test to obtain the discharge capacity respectively, divide the capacity obtained at 2C rate by the capacity obtained at 0.2C to obtain the rate performance.
  • testing of the above parameters of the lithium-ion battery belongs to the technology known to those skilled in the art, and will not be described here, and the testing method is not limited to the method described in this application, and other suitable testing methods can also be used.
  • Comparative Examples 1-2 to 1-10 and Examples 1-1 to 1-15 are the same as those of Comparative Example 1-1, the difference is that the corresponding parameters are adjusted to make the values of A, B and/or C different .
  • Embodiment 2-1 to 2-10 are identical to Embodiment 2-1 to 2-10:
  • Example 2-1 to 2-10 The preparation methods of Examples 2-1 to 2-10 are the same as those of Example 1-2, the only difference being that the corresponding parameters are adjusted so that the porosity P of the negative electrode sheet and/or the silicon element content C in the negative electrode sheet The values are different.
  • the volume expansion of silicon-based material particles is about 300% after lithium intercalation at room temperature.
  • the huge volume effect can easily lead to problems such as demoulding and powder falling of the negative electrode active material layer. Reserving a certain amount of pores in the negative electrode sheet can effectively alleviate the problem of silicon-based materials. Volume expansion. When the porosity of the negative electrode sheet is too low, it is difficult for the electrolyte to fully infiltrate the negative electrode sheet, which increases the transmission distance of lithium ions and deteriorates the kinetic performance of the lithium ion battery.
  • Example 1-2 By comparing Example 1-2 with Examples 2-1 to 2-10, it can be seen that the porosity P of the negative electrode sheet and the content C of silicon element in the negative electrode sheet satisfy the following relational formula: P>15 ⁇ C 1/4 , the cycle capacity retention rate and deformation rate of the lithium-ion battery at room temperature and low temperature are both improved.
  • Embodiment 3-1 to 3-5 are identical to Embodiment 3-1 to 3-5:
  • Example 3-1 to 3-5 The preparation method of Examples 3-1 to 3-5 is the same as that of Example 2-6, but a certain amount of fluoroethylene carbonate is added to the electrolyte, the difference is only that the fluoroethylene carbonate in the electrolyte
  • the ester content X has different values.
  • Fluoroethylene carbonate is an important film-forming additive in the electrolyte.
  • the SEI produced by the decomposition during the cycle isolates the further contact between the negative electrode active material and the electrolyte, reduces the consumption of lithium ions, and plays an important role in the cycle performance of lithium-ion batteries. important role.
  • Example 1-1, Example 3-1 to Example 3-5 it can be seen that after adding FEC to the electrolyte, when the FEC content in the electrolyte is greater than or equal to the silicon element content in the negative pole piece, lithium ions Both the cycle capacity retention rate and the deformation rate of the battery at normal temperature and low temperature are improved.
  • the FEC content should not be too high, because the addition of too much FEC will reduce the mobility of lithium ions in the electrolyte, affect the rate performance, and the deformation rate of lithium-ion batteries will increase, and the capacity retention rate at low temperatures will also decrease. .

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Abstract

本申请提供了电化学装置和电子装置。电化学装置包括负极极片，负极极片包括负极活性材料层，负极活性材料层包括硅基材料颗粒和粘结剂，负极极片满足：(B+C)/7<A<(B+C)/1.8，其中，A表示负极极片的负极活性材料层在Ar气氛下加热至480℃时以质量百分比为单位的失重率；B表示硅基材料颗粒内的硅元素的相对百分比含量波动值；C表示负极极片中的硅元素的以质量百分比为单位的含量。通过使负极极片满足(B+C)/7<A<(B+C)/1.8，能够显著改善电化学装置的循环性能、倍率性能和膨胀性能。

Description

电化学装置和电子装置 技术领域
本申请涉及电化学储能领域，尤其涉及电化学装置和电子装置。
背景技术
随着电化学装置(例如，锂离子电池)的发展和进步，对其循环性能和能量密度提出了越来越高的要求。目前，在改善电化学装置的能量密度方面，在负极极片中采用硅基材料是当前的趋势。然而，在硅基材料脱嵌锂过程中，存在较大的体积膨胀和收缩，形成大量新的固体电解质界相膜(SEI)，消耗电化学装置中有限的锂离子和电解液，显著增加电化学装置的阻抗，阻碍硅基材料的工业化大规模应用。
发明内容
本申请的一些实施例提供了一种电化学装置，电化学装置包括负极极片，负极极片包括负极活性材料层，负极活性材料层包括硅基材料颗粒和粘结剂，负极极片满足：(B+C)/7<A<(B+C)/1.8，其中，A表示负极极片的负极活性材料层在Ar气氛下加热至480℃时以质量百分比为单位的失重率；B表示硅基材料颗粒内的硅元素的相对百分比含量波动值；C表示负极极片中的硅元素的以质量百分比为单位的含量。通过使负极极片满足(B+C)/7<A<(B+C)/1.8，能够显著改善电化学装置的循环性能、倍率性能和膨胀性能。
在一些实施例中，负极极片的负极活性材料层在Ar气氛下加热至480℃时的失重率A满足：1.5％≤A≤18％。如果A的值太大，则表明负极活性材料层中的粘结剂太多，如此会抑制锂离子传输，增加电化学装置的极化作用，恶化电化学装置的倍率性能；如果A的值太小，则表明负极活性材料层中的粘结剂太少，不利于缓解硅基材料在循环过程中的体积膨胀，恶化电化学装置的循环性能。
在一些实施例中，硅基材料颗粒内的硅元素的相对百分比含量波动值B满足：B<16％。如果B太大，则表明硅元素的均一性较差，不利于电化学装置的循环性能和膨胀性能的改善。
在一些实施例中，负极极片中的硅元素的以质量百分比为单位的含量C满足：1％≤C≤20％。如果C的值太大，则硅基材料在循环过程中的膨胀过大，不利于电化学装置的循环性能的改善；如果C的值太小，则不利于电化学装置的能量密度的提升。
在一些实施例中，负极极片的孔隙率P和负极极片中的硅元素的质量百分含量C满足：P≥15×C 1/4。当负极极片中的硅元素的以质量百分比为单位的含量C越大时，则需要更多的孔隙来缓解硅基材料的膨胀。当满足P≥15×C 1/4时，能够有效缓解硅基材料的体积膨胀。
在一些实施例中，负极极片的孔隙率P满足：18％≤P≤40％。当负极极片的孔隙率过低时，电解液难以充分浸润，增加锂离子的传输距离，恶化电化学装置的动力学性能，并且也不利于缓解硅基材料在循环过程中的膨胀。当负极极片的孔隙率过大时，则不利于电化学装置的能量密度的提升。
在一些实施例中，电化学装置还包括电解液，电解液中包括氟代碳酸乙烯酯，并且氟代碳酸乙烯酯的以质量百分比为单位的含量X和负极极片中的硅元素的以质量百分比为单位的含量C满足:X≥C。当电解液中的FEC含量大于或等于负极极片中的硅元素的含量时，电化学装置的循环性能、膨胀性能和倍率性能较好。
在一些实施例中，氟代碳酸乙烯酯的以质量百分比为单位的含量X满足：2％≤X≤20％。当X的值太小时，氟代碳酸乙烯酯对电化学装置的循环性能的改善作用相对有限；当X的值太大时，表明FEC含量过高，过多的FEC会降低电解液中的锂离子的迁移率，影响电化学装置的倍率性能。
在一些实施例中，硅基材料颗粒包括硅元素和碳元素。通过将硅基颗粒嵌入碳基体中，避免硅基颗粒和电解液直接接触，减少循环过程中SEI的反复生成，从而减少可逆锂的损失。
本申请的实施例还提供了一种电子装置，包括上述电化学装置。
本申请的实施例通过使负极极片满足(B+C)/7<A<(B+C)/1.8，从极片层面看，能够将硅基材料的膨胀限制在极片可承受的范围内，显著改善电化学装 置的膨胀变形性能；从材料层面看，减少硅基材料的嵌锂膨胀，减少硅基颗粒表面的SEI反复生成与破坏，显著改善电化学装置的循环性能和倍率性能。
具体实施方式
下面的实施例可以使本领域技术人员更全面地理解本申请，但不以任何方式限制本申请。
本申请的一些实施例提供了一种电化学装置，电化学装置包括负极极片。在一些实施例中，负极极片包括负极活性材料层，负极活性材料层包括硅基材料颗粒和粘结剂。在一些实施例中，粘结剂可以将硅基材料颗粒粘结在一起，减小硅基材料颗粒在循环过程中的膨胀和收缩程度。
在一些实施例中，负极极片满足：(B+C)/7<A<(B+C)/1.8，其中，A表示负极极片的负极活性材料层在Ar气氛下加热至480℃时以质量百分比为单位的失重率；B表示硅基材料颗粒内的硅元素的相对百分比含量波动值；C表示负极极片中的硅元素的以质量百分比为单位的含量。在一些实施例中，A的值可以在一定程度上反映粘结剂的含量，A越大，负极活性材料层中的粘结剂的量越多，A越小，负极活性材料层中的粘结剂的量越少。为了减小电化学装置在循环过程中的变形，负极极片中可以存在足够的粘结剂，但是粘结剂过多会抑制锂离子传输，增加电化学装置的极化作用，恶化电化学装置的倍率性能。在一些实施例中，硅基材料颗粒内的硅元素的相对百分比含量波动值表示硅元素分布的均一性，波动值越大，均一性越差。硅元素的分布均一性对电化学装置的循环性能和膨胀性能有着显著的关联，均一性越高，越有利于降低锂离子电池膨胀产生的应力，电化学装置的循环性能和膨胀性能越好。在一些实施例中，通常地，负极极片中的硅元素的以质量百分比为单位的含量增大，电化学装置的能量密度能够相应地得到提高。通过使负极极片满足(B+C)/7<A<(B+C)/1.8，能够显著改善电化学装置的循环性能、倍率性能和膨胀性能。
在一些实施例中，负极极片的负极活性材料层在Ar气氛下加热至480℃时的失重率A满足：1.5％≤A≤18％。如果A的值太大，则表明负极活性材料层中的粘结剂太多，如此会抑制锂离子传输，增加电化学装置的极化作用，恶化电化学装置的倍率性能；如果A的值太小，则表明负极活性材料层中的 粘结剂太少，不利于缓解硅基材料在循环过程中的体积膨胀，恶化电化学装置的循环性能。在一些实施例中，A可以为1.5％、5％、8％、12％、15％、18％或任何其他合适的值。
在一些实施例中，硅基材料颗粒内的硅元素的相对百分比含量波动值B满足：B<16％。如果B太大，则表明硅元素的均一性较差，不利于电化学装置的循环性能和膨胀性能的改善。在一些实施例中，B可以为15％、10％、8％、5％或更小的值。
在一些实施例中，负极极片中的硅元素的以质量百分比为单位的含量C满足：1％≤C≤20％。在一些实施例中，如果C的值太大，则硅基材料在循环过程中的膨胀过大，不利于电化学装置的循环性能的改善；如果C的值太小，则不利于电化学装置的能量密度的提升。在一些实施例中，C可以为1％、5％、10％、15％、20％或任何其他合适的值。
在一些实施例中，负极极片的孔隙率P和负极极片中的硅元素的质量百分含量C满足：P≥15×C 1/4。硅基材料颗粒常温下嵌锂后体积膨胀约300％，巨大的体积膨胀效应容易导致负极极片脱模、掉粉等问题，在负极极片中预留一定的孔隙可有效缓解硅基材料的体积膨胀。当负极极片中的硅元素的以质量百分比为单位的含量C越大时，则需要更多的孔隙来缓解硅基材料的膨胀。当满足P≥15×C 1/4时，能够有效缓解硅基材料的体积膨胀。
在一些实施例中，负极极片的孔隙率P满足：18％≤P≤40％。当负极极片的孔隙率过低时，电解液难以充分浸润，增加锂离子的传输距离，恶化电化学装置的动力学性能，并且也不利于缓解硅基材料在循环过程中的膨胀。当负极极片的孔隙率过大时，则不利于电化学装置的能量密度和动力学性能的提升。
在一些实施例中，电化学装置还包括电解液，电解液在负极极片处会还原，在负极活性材料表面生成SEI层，稳定界面，延缓可逆锂的持续消耗。SEI过薄，容易在负极活性材料颗粒膨胀的过程中破裂，产生新的界面，恶化电化学装置的循环性能；SEI过厚会降低电荷转移的速率，恶化电化学装置的倍率性能。在一些实施例中，电解液中包括氟代碳酸乙烯酯，并且氟代碳酸乙烯酯的以质量百分比为单位的含量X和负极极片中的硅元素的以质量百分比为单位的含量C满足:X≥C。氟代碳酸乙烯酯(FEC)是电解液中重 要的成膜添加剂，循环过程中分解产生的SEI隔绝负极活性材料和电解液的进一步接触，减少锂离子的消耗，对于循环性能具有改善作用。当电解液中的FEC含量大于或等于负极极片中的硅元素的含量时，电化学装置的循环性能、膨胀性能和倍率性能更好。
在一些实施例中，氟代碳酸乙烯酯的以质量百分比为单位的含量X满足：2％≤X≤20％。当X的值太小时，氟代碳酸乙烯酯对电化学装置的循环性能的改善作用相对有限；当X的值太大时，表明FEC含量过高，过多的FEC会降低电解液中的锂离子的迁移率，影响电化学装置的倍率性能。在一些实施例中，X可以为2％、5％、10％、12％、15％、20％或其他合适的值。
在一些实施例中，硅基材料颗粒包括硅元素和碳元素，例如、硅碳化合物或复合物，例如，SiC。通过将硅基颗粒嵌入碳基体中，避免硅基颗粒和电解液直接接触，减少循环过程中SEI的反复生成，从而减少可逆锂的损失。
在一些实施例中，硅基材料的制备方法可以采用如下制备方法：将多孔碳基体置于回转炉中，在室温下用氮气将炉管吹扫20至40分钟，然后将多孔碳基体样品的温度提高到450℃至500℃。调节氮气流速以使气体在回转炉中的停留时间至少为90秒，并以该流速维持30分钟左右。然后将气体供应从氮气切换为含硅气体和氮气的混合气体(混合气体中含硅气体的体积分数为5％至30％)。在200sccm至400sccm的气体流速下沉积8小时至16小时后，向回转炉中持续通氮气从炉中吹出含硅气体，再在氮气条件下将回转炉吹扫30分钟，然后在5小时至10小时内将回转炉冷却到室温。然后通过将气流从氮气转换为来自压缩空气源的空气，在1小时至2小时内将回转炉内的氮气逐渐转换为空气，得到硅基材料。
在一些实施例中，多孔碳基体可以选自硬碳、软碳、石墨中的至少一种。例如，上述硬碳可以包括树脂碳、碳黑、有机聚合物热解碳及其组合。上述软碳可以包括碳纤维、碳微球及其组合。多孔碳基体的粒径没有限制，只要能实现本申请目的即可。例如，多孔碳基体的粒径范围为3μm<Dv50<15μm。
负极极片的负极活性材料层在Ar气氛下加热至480℃时的失重率A与负极活性材料层中的粘结剂的含量相关，例如，负极活性材料层中的粘结剂的用量越多，A越大，负极活性材料层中的粘结剂的用量越少，A越小。基于此，可以通过调节粘结剂的用量，从而调整A。
硅基材料颗粒内的硅元素的相对百分比含量波动值B与碳基体内部孔隙分布的均一性以及孔径大小相关，例如，碳基体内部孔隙分布越均一则B越小。基于此，可以通过调节孔隙分布和孔径大小，从而调整B。
负极极片中的硅元素的质量百分含量C与负极活性材料层中硅基材料的添加量相关，其中，硅基材料内部沉积的硅含量可通过调节沉积温度、沉积时间以及使用含硅气体的浓度来进行调整，例如，C通常随沉积温度的升高而增大、C通常随沉积时间的增加而增大、C通常随含硅气体的浓度升高而增加。基于此，可进行负极材料层中硅元素的质量含量C的调整。
负极极片的孔隙率通常随负极极片的压实密度增大而降低，基于此，可以通过调整负极极片的冷压压力，调节负极极片的压实密度，从而调整负极极片的孔隙率。
在一些实施例中，负极活性材料层中的粘结剂可以包括羧甲基纤维素(CMC)、聚丙烯酸、聚乙烯基吡咯烷酮、聚苯胺、聚酰亚胺、聚酰胺酰亚胺、聚硅氧烷、丁苯橡胶、环氧树脂、聚酯树脂、聚氨酯树脂或聚芴中的至少一种。
在一些实施例中，电化学装置可以包括电极组件，电极组件包括正极极片、负极极片、设置在正极极片和负极极片之间的隔离膜。在一些实施例中，负极极片还包括负极集流体。在一些实施例中，负极活性材料层可以位于负极集流体的一侧或两侧上。在一些实施例中，负极活性材料层中还可以包括导电剂。在一些实施例中，负极活性材料层中的导电剂可以包括纳米导电炭黑、碳纳米管、碳纤维、鳞片石墨、石墨烯或科琴黑中的至少一种。在一些实施例中，负极活性材料层还可以包括负极活性材料石墨，即负极活性材料层中可以包括作为负极活性材料的硅基材料和石墨。在一些实施例中，负极活性材料层中的负极活性材料、导电剂和粘结剂的质量比可以为(78至98.5)：(0.1至10)：(0.1至10)。应该理解，以上所述仅是示例，可以采用任何其他合适的材料和质量比。在一些实施例中，负极集流体可以采用铜箔、镍箔或碳基集流体中的至少一种。
在一些实施例中，正极极片包括正极集流体和设置在正极集流体上的正极活性材料层，正极活性材料层可以包括正极活性材料。在一些实施例中，正极活性材料包括钴酸锂、磷酸铁锂、磷酸锰铁锂、磷酸铁钠、磷酸钒锂、 磷酸钒钠、磷酸钒氧锂、磷酸钒氧钠、钒酸锂、锰酸锂、镍酸锂、镍钴锰酸锂、富锂锰基材料或镍钴铝酸锂中的至少一种。在一些实施例中，正极活性材料层还可以包括导电剂。在一些实施例中，正极活性材料层中的导电剂可以包括导电炭黑、科琴黑、片层石墨、石墨烯、碳纳米管或碳纤维中的至少一种。在一些实施例中，正极活性材料层还可以包括粘结剂，正极活性材料层中的粘结剂可以包括羧甲基纤维素(CMC)、聚丙烯酸、聚乙烯基吡咯烷酮、聚苯胺、聚酰亚胺、聚酰胺酰亚胺、聚硅氧烷、丁苯橡胶、环氧树脂、聚酯树脂、聚氨酯树脂或聚芴中的至少一种。在一些实施例中，正极活性材料层中的正极活性材料、导电剂和粘结剂的质量比可以为(80至99)：(0.1至10)：(0.1至10)。在一些实施例中，正极活性材料层的厚度可以为10μm至500μm。应该理解，以上所述仅是示例，正极活性材料层可以采用任何其他合适的材料、厚度和质量比。
在一些实施例中，正极集流体可以采用Al箔，当然，也可以采用本领域常用的其他集流体。在一些实施例中，正极集流体的厚度可以为1μm至50μm。在一些实施例中，正极活性材料层可以仅涂覆在正极的集流体的部分区域上。
在一些实施例中，隔离膜包括聚乙烯、聚丙烯、聚偏氟乙烯、聚对苯二甲酸乙二醇酯、聚酰亚胺或芳纶中的至少一种。例如，聚乙烯包括选自高密度聚乙烯、低密度聚乙烯或超高分子量聚乙烯中的至少一种。尤其是聚乙烯和聚丙烯，它们对防止短路具有良好的作用，并可以通过关断效应改善电池的稳定性。在一些实施例中，隔离膜的厚度在约3μm至20μm的范围内。
在一些实施例中，隔离膜表面还可以包括多孔层，多孔层设置在隔离膜的至少一个表面上，多孔层包括无机颗粒和粘结剂，无机颗粒选自氧化铝(Al 2O 3)、氧化硅(SiO 2)、氧化镁(MgO)、氧化钛(TiO 2)、二氧化铪(HfO 2)、氧化锡(SnO 2)、二氧化铈(CeO 2)、氧化镍(NiO)、氧化锌(ZnO)、氧化钙(CaO)、氧化锆(ZrO 2)、氧化钇(Y 2O 3)、碳化硅(SiC)、勃姆石、氢氧化铝、氢氧化镁、氢氧化钙或硫酸钡中的至少一种。在一些实施例中，隔离膜的孔具有在约0.01μm至1μm的范围的直径。多孔层的粘结剂选自聚偏氟乙烯、偏氟乙烯-六氟丙烯的共聚物、 聚酰胺、聚丙烯腈、聚丙烯酸酯、聚丙烯酸、聚丙烯酸盐、羧甲基纤维素钠、聚乙烯呲咯烷酮、聚乙烯醚、聚甲基丙烯酸甲酯、聚四氟乙烯或聚六氟丙烯中的至少一种。隔离膜表面的多孔层可以提升隔离膜的耐热性能、抗氧化性能和电解质浸润性能，增强隔离膜与极片之间的粘结性。
在一些实施例中，电解液还包括锂盐，锂盐可以包括LiPF 6、LiBF 4、LiAsF 6、LiClO 4、LiB(C 6H 5) 4、LiCH 3SO 3、LiCF 3SO 3、LiN(SO 2CF 3) 2、LiC(SO 2CF 3) 3、LiSiF 6、LiBOB或者二氟硼酸锂中的至少一种。优选地，锂盐包括LiPF 6。
在一些实施例中，电解液还可以包括非水溶剂。非水溶剂可为碳酸酯化合物、羧酸酯化合物、醚化合物、其它有机溶剂或它们的组合。碳酸酯化合物可为链状碳酸酯化合物、环状碳酸酯化合物、氟代碳酸酯化合物或其组合。链状碳酸酯化合物的实例为碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸甲乙酯(MEC)及其组合。所述环状碳酸酯化合物的实例为碳酸亚乙酯(EC)、碳酸亚丙酯(PC)、碳酸亚丁酯(BC)、碳酸乙烯基亚乙酯(VEC)或者其组合。所述氟代碳酸酯化合物的实例为碳酸1,2-二氟亚乙酯、碳酸1,1-二氟亚乙酯、碳酸1,1,2-三氟亚乙酯、碳酸1,1,2,2-四氟亚乙酯、碳酸1-氟-2-甲基亚乙酯、碳酸1-氟-1-甲基亚乙酯、碳酸1,2-二氟-1-甲基亚乙酯、碳酸1,1,2-三氟-2-甲基亚乙酯、碳酸三氟甲基亚乙酯或者其组合。羧酸酯化合物的实例为乙酸甲酯、乙酸乙酯、乙酸正丙酯、乙酸叔丁酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、γ-丁内酯、癸内酯、戊内酯、甲瓦龙酸内酯、己内酯、甲酸甲酯或者其组合。醚化合物的实例为二丁醚、四甘醇二甲醚、二甘醇二甲醚、1,2-二甲氧基乙烷、1,2-二乙氧基乙烷、乙氧基甲氧基乙烷、2-甲基四氢呋喃、四氢呋喃或者其组合。其它有机溶剂的实例为二甲亚砜、1,2-二氧戊环、环丁砜、甲基环丁砜、1,3-二甲基-2-咪唑烷酮、N-甲基-2-吡咯烷酮、甲酰胺、二甲基甲酰胺、乙腈、磷酸三甲酯、磷酸三乙酯、磷酸三辛酯或者其组合。所述非水溶剂的含量没有特别限制，只要能实现本申请的目的即可，例如，上述其它非水溶剂的质量百分含量为67％至86％，例如可以67％、67.5％、70％、75％、80％、83％、 85％、85.5％、86％或为其间的任意范围。
在一些实施例中，电化学装置包括锂离子电池，但是本申请不限于此。
在本申请的一些实施例中，电化学装置的电极组件为卷绕式电极组件、堆叠式电极组件或折叠式电极组件。在一些实施例中，电化学装置的正极极片和/或负极极片可以是卷绕或堆叠式形成的多层结构，也可以是单层正极、隔离膜、单层负极叠加的单层结构。
在本申请的一些实施例中，以锂离子电池为例，将正极极片、隔离膜、负极极片按顺序卷绕或堆叠成电极组件，之后装入例如铝塑膜中进行封装，注入电解液，化成、封装，即制成锂离子电池。然后，对制备的锂离子电池进行性能测试。
本领域的技术人员将理解，以上描述的电化学装置(例如，锂离子电池)的制备方法仅是实施例。在不背离本申请公开的内容的基础上，可以采用本领域常用的其他方法。
本申请的实施例还提供了包括上述电化学装置的电子装置。本申请实施例的电子装置没有特别限定，其可以是用于现有技术中已知的任何电子装置。在一些实施例中，电子装置可以包括，但不限于，笔记本电脑、笔输入型计算机、移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、电子记事本、计算器、存储卡、便携式录音机、收音机、备用电源、电机、汽车、摩托车、助力自行车、自行车、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机、家庭用大型蓄电池和锂离子电容器等。
下面列举了一些具体实施例和对比例以更好地对本申请进行说明，其中，采用锂离子电池作为示例。
对比例1-1
正极极片的制备：将正极活性材料钴酸锂、导电炭黑(Super P)、聚偏二氟乙烯(PVDF)按照重量比97：1.4：1.6进行混合，加入N-甲基吡咯烷酮(NMP)作为溶剂，搅拌均匀。将浆料(固含量为72wt％)均匀涂覆在正 极集流体铝箔上，涂覆厚度为80μm，在85℃下烘干，然后经过冷压、裁片、分切后，在85℃的真空条件下干燥4小时，得到正极极片。
硅基复合材料的制备：将Dv50为10μm的多孔碳基体置于回转炉中，在室温下用氮气将炉管吹扫30分钟，然后将多孔碳样品的加热温度提高到450℃。调节氮气流速以使气体在回转炉中的停留时间至少为90秒，并以该流速维持30分钟。然后将气体供应从氮气切换为含硅气体(例如硅烷)和氮气的混合气体，其中混合气体中含硅气体和氮气的体积比为5︰95。在200sccm的气体流速下沉积8小时后，向回转炉中持续通氮气从炉中吹出含硅气体，再在氮气条件下将回转炉吹扫30分钟，然后在数小时(例如8小时)内将回转炉冷却到室温。然后通过将气流从氮气转换为来自压缩空气源的空气，在2小时内将回转炉内的氮气逐渐转换为空气，得到硅基复合材料，即硅基颗粒。经测定，该硅基材料颗粒内的硅元素的相对百分比含量波动值B为10％。
负极极片的制备：将上述制备得到的硅基材料、人造石墨、粘结剂聚丙烯酸和羧甲基纤维素钠(CMC)按重量:5.7：91.8：1：1.5的比例溶于去离子水中，形成负极浆料(固含量为40wt％)。采用10μm厚度铜箔作为负极集流体，将负极浆料涂覆于负极的集流体上，涂覆厚度为50μm，在85℃下烘干，然后经过冷压、裁片、分切后，在120℃的真空条件下干燥12小时，得到负极极片。
隔离膜的制备：隔离膜为7μm厚的聚乙烯(PE)。
电解液的制备：在干燥的氩气气氛手套箱中，将碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸二乙酯(DEC)按照质量比为EC：PC：DEC＝1：1：1进行混合，溶解并充分搅拌后加入锂盐LiPF 6，混合均匀后获得电解液，其中LiPF 6的质量百分含量为12.5％。
锂离子电池的制备：将正极极片、隔离膜、负极极片按顺序依次叠好，使隔离膜处于正极和负极中间，起到隔离的作用，并卷绕得到电极组件。将电极组件置于外包装铝塑膜中，在80℃下脱去水分后，注入上述电解液并封装，经过化成，脱气，切边等工艺流程得到锂离子电池。
其他实施例和对比例是在对比例1-1的步骤的基础上进行参数变更，具体变更的参数如下表所述。
下面描述本申请的各个参数的测试方法。
1.负极极片的孔隙率测试：采用气体置换法测试负极极片的孔隙率：采用同一模具冲切大于50片半径为d极片，分别测量每片极片的厚度h，并装入真密度测试仪(AccuPycⅡ1340)样品杯中，在密闭的样品仓中采用He对极片进行填充，由此测得极片的真体积V，最后通过如下公式获得极片的孔隙率P：P＝(1-V/πd 2×50×h)×100％。
2.负极极片中硅元素含量的测试：将负极极片置于真空烘箱中100℃干燥24h，用刀片刮下负极极片上的部分活性材料层称量得质量M1，再将刮下的活性材料层置于持续的空气气氛中800℃热处理，去除碳质材料，剩余的材料称量得质量M2，最后通过如下公式获得极片中硅元素的含量C：C＝0.467×M2/M1。
3.硅基材料颗粒内的硅元素的相对百分比含量波动值测试：将极片置于真空烘箱中100℃干燥24h，在保护性气氛下，采用聚焦离子束(FIB)将极片中的硅基材料颗粒加工成50-100nm的薄片，然后采用投射电子显微镜(TEM)设备中的X射线能谱仪(EDS)线扫测试硅基颗粒内硅原子相对百分比含量，线扫位置选取在硅基颗粒的内部的任意位置，硅元素的波动值为整个线扫中硅原子相对百分比含量最高值和最低值的差值。
4.电解液中的氟代碳酸乙烯酯(FEC)含量测试：将电化学装置放电至0％的荷电状态(SOC)后离心，离心后得到的液体进行GC-MS测试，检测出FEC组分百分比。
5.负极活性材料层在Ar气氛下加热至480℃时以质量百分比为单位的失重率测试：用刀片刮下负极极片上的部分活性材料层称量得质量A1，再将刮下的活性材料层置于Ar气氛下加热至480℃，量得质量A2，失重率A＝(A1-A2)/A1。
6.循环性能测试：测试温度分别为25℃和-10℃，以0.7C恒流充电到4.4V，恒压充电到0.025C，静置5分钟后以0.5C放电到3.0V。以此时得到 的容量为初始容量，进行0.7C充电/0.5C放电进行循环测试，以25℃/-10℃循环400圈时的容量为实际容量，容量保持率＝实际容量/初始容量。
7.倍率性能测试：在25℃下，以0.2C放电到3.0V，静置5min，以0.5C充电到4.45V，恒压充电到0.05C后静置5分钟，调整放电倍率，以0.2C和2.0C进行放电测试，分别得到放电容量，以2C倍率下得到的容量除以0.2C得到的容量，得到倍率性能。
8.变形率测试：用螺旋千分尺测试半充时新鲜锂离子电池的厚度h1，循环至400圈时，锂离子电池处于满充状态下，再用螺旋千分尺测试此时锂离子电池的厚度h2，锂离子电池的变形率＝(h2-h1)/h1。
应该理解，锂离子电池的上述参数的测试属于本领域技术人员公知的技术，在此不展开描述，并且测试方法不限于本申请描述的方法，还可以采用其他合适的测试方法。
对比例1-1至1-10和实施例1-1至1-15：
对比例1-2至1-10和实施例1-1至1-15的制备方法与对比例1-1的制备方法相同，区别仅在于调整相应参数使A、B和/或C的值不同。
表1：
Figure PCTCN2021141317-appb-000001
Figure PCTCN2021141317-appb-000002
通过比较实施例1-1至1-3和对比例1-1至1-2可以看出，当负极极片中的硅元素含量C和硅元素在硅基材料颗粒内的分布均一度B一定时，随着失重率A的提高，锂离子电池的循环容量保持率先增大后减小，锂离子电池的变形率先减小后增大，锂离子电池的倍率性能先增大后减小。这是由于A值越高，负极极片的粘结力越强，硅基材料颗粒的表面SEI的稳定性越高，对硅基材料在循环过程中的保护越好；但当A过高时，锂离子电池的循环容量保持率、变形率和倍率性能受到影响，这是由于粘结剂和SEI的含量过多，会抑制锂离子传输，增加锂离子电池的极化作用。通过比较对比例1-3至1-4和实施例1-4至1-6、或比较对比例1-5至1-6和实施例1-7至1-9、或比较对比例1-7至1-8和实施例1-10至1-12、或比较对比例1-9至1-10和实施例1-13至1-15可以得到同样的结论。
此外，负极极片中的硅元素含量越高，硅元素在硅基材料内的分布均匀度越低，需要使用的粘结剂和SEI越多，当其满足不等式：(B+C)/7<A<(B+C)/1.8时，锂离子电池的容量保持率、变形率以及倍率性能提升。
实施例2-1至2-10：
实施例2-1至2-10的制备方法与实施例1-2的制备方法相同，区别仅在于调整相应参数使负极极片的孔隙率P和/或负极极片中的硅元素含量C的值不同。
表2：
Figure PCTCN2021141317-appb-000003
硅基材料颗粒常温下嵌锂后体积膨胀约300％，巨大的体积效应容易导致负极活性材料层脱模、掉粉等问题，在负极极片中预留一定的孔隙可有效缓解硅基材料的体积膨胀。当负极极片的孔隙率过低时，电解液难以充分浸润负极极片，增加锂离子的传输距离，恶化锂离子电池的动力学性能。通过比较实施例1-2和实施例2-1至2-10可知，负极极片的孔隙率P和负极极片中的硅元素的含量C满足如下关系式：P＞15×C 1/4时，锂离子电池的常温和低温下的循环容量保持率和变形率均得到改善。
实施例3-1至3-5：
实施例3-1至3-5的制备方法与实施例2-6的制备方法相同，但向电解液中再加入一定含量的氟代碳酸乙烯酯，区别仅在于电解液中的氟代碳酸乙烯酯的含量X的值不同。
表3：
Figure PCTCN2021141317-appb-000004
Figure PCTCN2021141317-appb-000005
表3中，“/”表示不存在相应制备参数。
氟代碳酸乙烯酯(FEC)是电解液中重要的成膜添加剂，循环过程中分解产生的SEI隔绝负极活性材料和电解液的进一步接触，减少锂离子的消耗，对于锂离子电池的循环性能有着重要的作用。通过比较实施例1-1、实施例3-1至实施例3-5可知，电解液中添加FEC后，当电解液中的FEC含量大于或等于负极极片中的硅元素含量时，锂离子电池的常温和低温下的循环容量保持率和变形率均得到改善。然而，FEC含量也不能过高，这是由于过多FEC的添加会降低电解液中锂离子的迁移率，影响倍率性能，并且锂离子电池的变形率增大，低温下的容量保持率也降低。
以上描述仅为本申请的较佳实施例以及对所运用技术原理的说明。本领域技术人员应当理解，本申请中所涉及的公开范围，并不限于上述技术特征的特定组合而成的技术方案，同时也应涵盖由上述技术特征或其等同特征进行任意组合而形成的其它技术方案。例如上述特征与本申请中公开的具有类似功能的技术特征进行互相替换而形成的技术方案。

Claims (10)

  1. 一种电化学装置，其包括：
    负极极片，所述负极极片包括负极活性材料层，所述负极活性材料层包括硅基材料颗粒和粘结剂，所述负极极片满足：
    (B+C)/7<A<(B+C)/1.8，
    其中，A表示所述负极极片的所述负极活性材料层在Ar气氛下加热至480℃时以质量百分比为单位的失重率；B表示所述硅基材料颗粒内的硅元素的相对百分比含量波动值；C表示所述负极极片中的硅元素的以质量百分比为单位的含量。
  2. 根据权利要求1所述的电化学装置，其中，所述负极极片的所述负极活性材料层在Ar气氛下加热至480℃时的失重率A满足：1.5％≤A≤18％。
  3. 根据权利要求1所述的电化学装置，其中，所述硅基材料颗粒内的硅元素的相对百分比含量波动值B满足：B<16％。
  4. 根据权利要求1所述的电化学装置，其中，所述负极极片中的硅元素的以质量百分比为单位的含量C满足：1％≤C≤20％。
  5. 根据权利要求1所述的电化学装置，其中，所述负极极片的孔隙率P和所述负极极片中的硅元素的质量百分含量C满足：P＞15×C 1/4。
  6. 根据权利要求5所述的电化学装置，其中，所述负极极片的孔隙率P满足：18％≤P≤40％。
  7. 根据权利要求1所述的电化学装置，其中，所述电化学装置还包括电解液，所述电解液中包括氟代碳酸乙烯酯，并且所述氟代碳酸乙烯酯的以质量百分比为单位的含量X和所述负极极片中的硅元素的以质量百分比为单位的含量C满足:X≥C。
  8. 根据权利要求7所述的电解液，其中，所述氟代碳酸乙烯酯的以质量百分比为单位的含量X满足：2％≤X≤20％。
  9. 根据权利要求1所述的电化学装置，其中，所述硅基材料颗粒包括硅元素和碳元素。
  10. 一种电子装置，包括根据权利要求1至9中任一项所述的电化学装置。
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