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WO2022142241A1 - 负极活性材料、电化学装置和电子装置 - Google Patents

负极活性材料、电化学装置和电子装置 Download PDF

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Publication number
WO2022142241A1
WO2022142241A1 PCT/CN2021/104552 CN2021104552W WO2022142241A1 WO 2022142241 A1 WO2022142241 A1 WO 2022142241A1 CN 2021104552 W CN2021104552 W CN 2021104552W WO 2022142241 A1 WO2022142241 A1 WO 2022142241A1
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Prior art keywords
negative electrode
active material
electrode active
carbon
silicon
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PCT/CN2021/104552
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English (en)
French (fr)
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陈聪荣
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宁德新能源科技有限公司
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Priority to JP2022520150A priority Critical patent/JP7378605B2/ja
Priority to EP21912994.7A priority patent/EP4273961A4/en
Publication of WO2022142241A1 publication Critical patent/WO2022142241A1/zh
Priority to US18/345,321 priority patent/US20230343933A1/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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • H—ELECTRICITY
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    • 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
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    • 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
    • H—ELECTRICITY
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    • 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
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    • 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
    • H01M10/0568—Liquid materials characterised by the solutes
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    • H01M4/00—Electrodes
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
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    • 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
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    • 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
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
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    • 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
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
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    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
    • 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
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • 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
    • 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
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
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    • 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
    • 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 lithium-ion batteries. Specifically, the present application relates to a negative electrode active material and a preparation method thereof. The present application also relates to negative electrodes, electrochemical devices, and electronic devices including the negative electrode active material.
  • the main means to improve the cycle performance of silicon-oxygen materials include the following: carbon-protected silicon-oxygen materials, interstitial void layers in the middle of carbon-protected silicon-oxygen materials, reducing the size of silicon-oxygen materials, polymer-protected silicon-oxygen materials, amorphous oxide protection Silicone materials, etc.
  • carbon-protected silicon-oxygen materials have become the main application direction at present due to their relatively good electronic conductivity and high stability.
  • the carbon-protected silicon-oxygen material is likely to cause decarburization due to repeated shear force during the processing of the battery pole piece, which affects the Coulomb efficiency, and the formation of the SEI film (solid electrolyte interface film) consumes the electrolyte.
  • the expansion, contraction and cracking of silicon during multiple cycles cause the carbon layer to be easily peeled off from the substrate.
  • the carbon layer With the formation of SEI, the carbon layer is wrapped by by-products, which greatly increases the electrochemical impedance and polarization. , affecting the cycle life. Therefore, improving the interface bonding performance between the carbon layer and the silicon-oxygen material is of great significance for improving the cycle life and improving the stability of the cycle structure.
  • the polymer-protected silicon-oxygen material and the amorphous oxide-protected silicon-oxygen material can effectively avoid the direct contact between the electrolyte and the silicon-oxygen material, due to the poor conductivity of the polymer and the amorphous oxide, it will increase the electrochemical impedance and polarity. Not only the silicon oxide material cannot effectively deintercalate lithium, but also the protective layer is easily destroyed when deintercalating lithium, which affects the cycle life. Therefore, while avoiding the direct contact between the electrolyte and the silicon-oxygen material, improving the conductivity of the silicon-oxygen material and suppressing the volume expansion of the silicon-oxygen material are of great significance for improving the cycle life of the negative electrode active material and improving the stability of the cycle structure.
  • the present application provides, in a first aspect, a negative electrode active material, which can improve cycle life and cycle structure stability as a negative electrode active material for a lithium ion battery.
  • the negative electrode active material provided by the present application includes a silicon carbon composite, wherein the silicon carbon composite includes silicon oxide and graphite, the general formula of the silicon oxide is SiO X , 0.5 ⁇ x ⁇ 1.6, the silicon carbon
  • the composite satisfies the following relation: 2 ⁇ b/a ⁇ 6, where a represents the average particle size of silicon oxide and b represents the average particle size of graphite.
  • the inventors of the present application have found through research that only when the average particle size of SiO X and graphite satisfies 2 ⁇ b/a ⁇ 6, can an appropriate granulation particle size and better cycle improvement be achieved.
  • the silicon oxide has an average particle size of 2 ⁇ m to 6 ⁇ m.
  • the average particle size of the graphite is 4.1 ⁇ m to 30 ⁇ m. The combination of silicon oxide and graphite with a suitable particle size range can effectively improve the cycle performance of the negative electrode active material.
  • c represents the Dv50 of the negative electrode active material, c is 6.1 ⁇ m to 60 ⁇ m, and the negative electrode active material with a particle size in an appropriate range is selected through a granulation process.
  • the negative electrode active material satisfies the following relationship: a+b ⁇ c ⁇ 5b, a represents the average particle size of silicon oxide, b represents the average particle size of graphite, and c represents the negative electrode active material Dv50.
  • a represents the average particle size of silicon oxide
  • b represents the average particle size of graphite
  • c represents the negative electrode active material Dv50.
  • the negative electrode active material further includes a protective layer on the surface of the silicon carbon composite.
  • the protective layer includes at least one of carbon nanotubes, amorphous carbon or graphene.
  • the carbon nanotubes are wrapped on the surface of graphite and SiO X , improve the combination of SiO X and graphite, and are interspersed between SiO X and graphite at the same time to improve the ionic and electronic conductivity of the material; the amorphous carbon is protected on the surfaces of graphite and SiO X , and at the same time
  • the protective layer not only improves the conductive interface of silicon and graphite, but also improves the conductivity of the material, thereby improving the cycle performance, expansion rate and kinetics of the hybrid negative electrode.
  • the protective layer includes a first protective material and a second protective material
  • the first protective material includes at least one of carbon nanotubes, amorphous carbon or graphene
  • the second protective material includes At least one of carbon nanotubes, amorphous carbon or graphene
  • the tube length of the carbon nanotubes is d, 1 ⁇ m ⁇ d ⁇ 15 ⁇ m
  • the mass fraction of the protective layer is 0.05% to 5%.
  • the protective layer includes a first protective material and a second protective material
  • the first protective material includes at least one of carbon nanotubes, amorphous carbon or graphene
  • the second protective material includes At least one of carbon nanotubes, amorphous carbon or graphene.
  • the carbon nanotubes are wrapped on the surface of graphite and SiO X , improve the combination of SiO X and graphite, and are interspersed between SiO X and graphite at the same time to improve the ionic and electronic conductivity of the material; the amorphous carbon is protected on the surfaces of graphite and SiO X , and at the same time In contact with carbon nanotubes, it plays a bonding role and inhibits the volume expansion of silicon oxide.
  • the protective layer not only improves the conductive interface of silicon and graphite, but also improves the conductivity of the material, thereby improving the cycling performance, expansion rate, and kinetics of the anode.
  • the tube length of the carbon nanotube is d, and 1 ⁇ m ⁇ d ⁇ 15 ⁇ m.
  • a certain length of carbon nanotubes can provide long-range electrical conductivity between particles during cycling, while too short carbon nanotubes have little effect on improving the long-range electrical conductivity between particles during cycling. It is easy to cause particles to agglomerate and expand to increase.
  • the mass fraction of the protective layer is 0.05% to 5%.
  • the role of the protective layer is to protect the interface of the negative electrode active material and avoid direct contact between more particle surfaces and the electrolyte.
  • the mass fraction of the protective layer is too high, it is easy to cause more side reactions in the protective layer.
  • the protection layer includes a first protection object and a second protection object, the first protection object and the second protection object are in contact, and the thickness of the first protection object is 20 nm To 300 nm, the thickness of the second protective material is 20 nm to 500 nm.
  • the thickness is the vertical distance from the contact of the first protector with the silicon-carbon composite ( SiOx /graphite) to the contact with the second protector, ie, amorphous carbon.
  • the thickness of the second protection material is 20 nm to 500 nm, and the thickness is calculated from the surface of SiO X and in a direction perpendicular to the surface.
  • the thickness of amorphous carbon needs to be controlled below 500 nm, too thick amorphous carbon cannot ensure the conduction of ions and the long-range conductivity of carbon nanotubes.
  • the specific surface area of the negative electrode active material is 1 m 2 /g to 50 m 2 /g; according to some preferred embodiments of the present application, based on the negative electrode active material, the mass fraction of the silicon oxide is 5% to 50%, and the mass fraction of the graphite is 25% to 93.5%.
  • the negative electrode active material has a specific surface area of 1.11 m 2 /g to 1.59 m 2 /g. If the specific surface area of the negative electrode active material is too high, it is easy to cause side reactions of the cycle.
  • the graphite includes at least one of artificial graphite or natural graphite, wherein the artificial graphite or natural graphite includes at least one of mesocarbon microspheres or hard carbon.
  • the carbon nanotubes comprise single-walled carbon nanotubes, multi-walled carbon nanotubes, or a combination of both.
  • the amorphous carbon is obtained by carbonization of organic matter, wherein the organic matter includes selected from carboxymethyl cellulose and its metal salts, polyvinylpyrrolidone, polyacrylate, polyimide, polyamide, polyamideimide, polyamide At least one of vinylidene fluoride, styrene-butadiene rubber, sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, polyacrylonitrile, alkane, alkene or alkyne.
  • the organic matter includes selected from carboxymethyl cellulose and its metal salts, polyvinylpyrrolidone, polyacrylate, polyimide, polyamide, polyamideimide, polyamide At least one of vinylidene fluoride, styrene-butadiene rubber, sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, polyacrylonitrile, alkane, alkene or alkyne.
  • the negative electrode active material provided by this application uses silicon oxide and graphite for composite granulation, and protects carbon nanotubes and amorphous carbon on silicon and graphite, which acts as a bridge, strengthens the contact between silicon oxide and graphite, and improves the electrical conductivity, and suppresses the volume expansion of silicon oxide, thereby improving the cycling performance, expansion ratio, and kinetics of the anode.
  • a second aspect of the present application provides a method for preparing the negative electrode active material described in the first aspect, comprising the following steps: step A, mixing silicon oxide and graphite in a solvent to form a first mixture; step B, mixing carbon The nanotubes are mixed with the first mixture to form a second mixture; in step C, the second mixture is spray-dried to form granulation; in step D, the granulated product obtained in step C is sintered in an inert atmosphere.
  • the present application provides a negative electrode comprising the negative electrode active material described in the first aspect of the present application.
  • the negative electrode further includes a conductive agent and a binder.
  • the 5t compaction of the negative electrode is P
  • the mass fraction of carbon nanotubes (relative to the total mass of the negative electrode active material) is n
  • P the mass fraction of carbon nanotubes
  • the sheet resistance of the anode of the anode active material is less than 1 ohm.
  • the negative electrode of the present invention can be prepared by a known method in the art. Usually, the negative electrode active material and optional conductive agent (such as carbon black and other carbon materials and metal particles, etc.), binder (such as SBR), other optional additives (such as PTC thermistor material) and other materials are mixed in Disperse together in a solvent (such as deionized water), uniformly coat the negative electrode current collector after stirring evenly, and obtain a negative electrode containing a negative electrode membrane after drying.
  • a solvent such as deionized water
  • a material such as a metal foil or a porous metal plate can be used as the negative electrode current collector.
  • the present application provides an electrochemical device comprising a negative electrode comprising the negative electrode active material according to the first aspect of the present application.
  • the present application provides an electrochemical device comprising an electrolyte, the electrolyte further comprising a lithium salt, the lithium salt comprising lithium bis(fluorosulfonyl)imide (LiFSI) and lithium hexafluorophosphate ( LiPF 6 ), according to some embodiments of the present application, the concentration of the lithium salt is 1 mol/L to 2 mol/L, and the mass ratio of lithium bis(fluorosulfonyl)imide to lithium hexafluorophosphate is 0.06 to 5.
  • LiFSI lithium bis(fluorosulfonyl)imide
  • LiPF 6 lithium hexafluorophosphate
  • the cycle performance and expansion performance of the cell are improved, which is mainly because the interaction between the silicon-carbon composite in the anode material and the lithium salt in the electrolyte improves the gap between the anode and the electrolyte. contact, thereby improving its cycle performance.
  • the negative electrode active material further includes a protective layer on the surface of the silicon carbon composite, the protective layer including carbon nanotubes, amorphous carbon or graphene at least one of them.
  • the protective layer includes a first protective material and a second protective material, the thickness of the first protective material is 20 nm to 300 nm, and the second protective material The thickness is 20nm to 500nm.
  • the protective layer includes a first protective material and a second protective material
  • the first protective material includes at least one of carbon nanotubes, amorphous carbon or graphene
  • the second protective material includes carbon At least one of nanotubes, amorphous carbon or graphene
  • the tube length of the carbon nanotubes is d, 1 ⁇ m ⁇ d ⁇ 15 ⁇ m
  • the mass fraction of the protective layer is 0.05% to 5% based on the negative electrode active material.
  • the specific surface area of the negative electrode active material is 1 m 2 /g to 50 m 2 /g; according to some preferred embodiments of the present application, based on the negative electrode active material, the The mass fraction of the silicon oxide is 5% to 50%, and the mass fraction of the graphite is 25% to 93.5%; according to some preferred embodiments of the present application, a is 2 ⁇ m to 6 ⁇ m; according to some preferred embodiments of the present application , b is 4.1 ⁇ m to 30 ⁇ m; according to some preferred embodiments of the present application, c represents the Dv50 of the negative electrode active material, and c is 6.1 ⁇ m to 60 ⁇ m; according to some preferred embodiments of the present application, c represents the Dv50 of the negative electrode active material, a +b ⁇ c ⁇ 5b.
  • the electrochemical device of the present application refers to any device capable of generating an electrochemical reaction, and specific examples thereof include all kinds of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors.
  • the electrochemical device is a lithium secondary battery, including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.
  • the present application further provides an electronic device comprising the electrochemical device described in the third aspect of the present application.
  • the electronic device of the present application is not particularly limited.
  • the electronic devices of the present application include, but are not limited to, notebook computers, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, headsets , VCR, LCD TV, Portable Cleaner, Portable CD Player, Mini CD, Transceiver, Electronic Notepad, Calculator, Memory Card, Portable Recorder, Radio, Backup Power, Motor, Automobile, motorcycle, Power-assisted Bicycle, Bicycle , lighting equipment, toys, game consoles, clocks, power tools, flashes, cameras, large household batteries and lithium-ion capacitors, etc.
  • the negative electrode active material provided by the present application achieves a suitable granulation particle size and better cycle improvement through the median particle size of SiO X and graphite satisfying 2 ⁇ b/a ⁇ 6.
  • the negative electrode active material is used for the negative electrode of a lithium ion battery, and can improve cycle life and cycle structure stability.
  • FIG. 1 is a schematic structural diagram of an anode active material according to an embodiment of the present application.
  • FIG. 2 is a SEM image of the anode active material according to Example 1 of the present application.
  • FIG. 3 is a SEM image of the anode active material according to Example 3 of the present application.
  • Example 4 is a cross-sectional view of the negative electrode according to Example 1 of the present application.
  • 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.
  • the negative electrode active material provided by the present application includes a silicon carbon composite, the silicon carbon composite includes silicon oxide and graphite, the general formula of the silicon oxide is SiO X , 0.5 ⁇ x ⁇ 1.6, the silicon carbon composite The following relational expression is satisfied: 2 ⁇ b/a ⁇ 6, where a represents the average particle size of silicon oxide and b represents the average particle size of graphite.
  • the inventors of the present application have found through research that only when the median particle size of SiO X and graphite satisfies 2 ⁇ b/a ⁇ 6, can an appropriate granulation particle size and better cycle improvement be achieved.
  • the silicon oxide has an average particle size of 2 ⁇ m to 6 ⁇ m
  • the graphite has an average particle size of 4.1 ⁇ m to 30 ⁇ m. If the average particle size of silicon oxide is too large or too small, its cycle will be affected.
  • the combination of silicon oxide and graphite with a suitable particle size range can effectively improve the cycle performance of the negative electrode active material.
  • the average particle size of the silicon oxide is 2 ⁇ m to 6 ⁇ m, and specifically, may be 2 ⁇ m, 2.5 ⁇ m, 3 ⁇ m, 3.5 ⁇ m, 4 ⁇ m, 4.5 ⁇ m, 5 ⁇ m, 5.5 ⁇ m, 6 ⁇ m or among these values A range of any two.
  • the average particle size of the graphite is 4.1 ⁇ m to 30 ⁇ m, specifically, may be 5 ⁇ m, 5.5 ⁇ m, 6 ⁇ m, 6.5 ⁇ m, 7 ⁇ m, 7.5 ⁇ m, 8 ⁇ m, 9 ⁇ m, 10 ⁇ m, 11 ⁇ m, 12 ⁇ m, 13 ⁇ m , 14 ⁇ m, 15 ⁇ m, 16 ⁇ m, 17 ⁇ m, 18 ⁇ m, 19 ⁇ m, 20 ⁇ m, 23 ⁇ m, 25 ⁇ m, 28 ⁇ m, or a range of any two of these values.
  • c represents the Dv50 of the negative electrode active material, c is 6.1 ⁇ m to 60 ⁇ m, and the negative electrode active material with a particle size in an appropriate range is selected through a granulation process.
  • the negative electrode active material satisfies the following relationship: a+b ⁇ c ⁇ 5b, a represents the average particle size of silicon oxide, b represents the average particle size of graphite, and c represents the negative electrode active material Dv50.
  • a represents the average particle size of silicon oxide
  • b represents the average particle size of graphite
  • c represents the negative electrode active material Dv50.
  • the Dv50 of the negative electrode active material is 6.1 ⁇ m to 60 ⁇ m, 17 ⁇ m, 18 ⁇ m, 19 ⁇ m, 20 ⁇ m, 23 ⁇ m, 25 ⁇ m, 28 ⁇ m, 30 ⁇ m, 35 ⁇ m, 38 ⁇ m, 42 ⁇ m, 45 ⁇ m, 48 ⁇ m, 50 ⁇ m, 55 ⁇ m or a range of any two of these values.
  • the negative electrode active material further includes a protective layer on the surface of the silicon carbon composite.
  • the protective layer includes at least one of carbon nanotubes, amorphous carbon or graphene.
  • the carbon nanotubes are wrapped on the surface of graphite and SiO X , improve the combination of SiO X and graphite, and are interspersed between SiO X and graphite at the same time to improve the ionic and electronic conductivity of the material; the amorphous carbon is protected on the surfaces of graphite and SiO X , and at the same time
  • the protective layer not only improves the conductive interface of silicon and graphite, but also improves the conductivity of the material, thereby improving the cycle performance, expansion rate and kinetics of the hybrid negative electrode.
  • the protection layer includes a first protection object and a second protection object, the first protection object and the second protection object are in contact, and the thickness of the first protection object is 20 nm To 300 nm, the thickness of the second protective material is 20 nm to 500 nm. The thickness is the vertical distance from the contact of the first protector with the silicon-carbon composite ( SiOx /graphite) to the contact with the second protector, ie, amorphous carbon. The thickness of the second protection material is 20 nm to 500 nm, which belongs to irregular protection, and the thickness is calculated from the surface of SiO X.
  • the thickness of the first protector is 20 nm, 30 nm, 50 nm, 80 nm, 100 nm, 120 nm, 150 nm, 180 nm, 200 nm, 250 nm, 300 nm, or a range composed of any two of these values.
  • the thickness of the second protector is 20 nm, 30 nm, 50 nm, 80 nm, 100 nm, 120 nm, 150 nm, 180 nm, 200 nm, 250 nm, 300 nm, 320 nm, 350 nm, 500 nm, 400 nm, or any two of these values range composed of.
  • the thickness of amorphous carbon needs to be controlled below 500 nm, too thick amorphous carbon cannot ensure the conduction of ions and the long-range conductivity of carbon nanotubes.
  • the negative electrode active material has a specific surface area of 1 m 2 /g to 50 m 2 /g, such as 1 m 2 /g, 5 m 2 /g, 8 m 2 /g, 10 m 2 /g, 15 m 2 /g, 18m 2 /g, 23m 2 /g, m 2 /g, 30m 2 /g, 38m 2 /g, 42m 2 /g, 48m 2 /g, or a range of any two of these values. If the specific surface area of the negative electrode active material is too high, it is easy to cause side reactions of the cycle.
  • the tube length of the carbon nanotube is d, and 1 ⁇ m ⁇ d ⁇ 15 ⁇ m, for example, 1 ⁇ m, 2 ⁇ m, 5 ⁇ m, 8 ⁇ m, 10 ⁇ m, 12 ⁇ m or a range composed of any two of these values.
  • a certain length of carbon nanotubes can provide long-range electrical conductivity between particles during cycling, while too short carbon nanotubes have little effect on improving the long-range electrical conductivity between particles during cycling. It is easy to cause particles to agglomerate and expand to increase.
  • the mass fraction of the protective layer is 0.05% to 5% based on the negative electrode active material.
  • the role of the protective layer is to protect the interface of the negative electrode active material and avoid direct contact between more particle surfaces and the electrolyte.
  • the mass fraction of the protective layer is too high, it is easy to cause more side reactions in the protective layer.
  • the mass fraction of the silicon oxide is 5% to 50%, and specifically may be 5%, 8%, 10%, 12%, 15%, 20%, 25% %, 30%, 35%, 40%, 45%, or a range of any two of these values.
  • the mass fraction of the graphite is 25% to 93.5%, specifically 25%, 28%, 30%, 35%, 40%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or a range of any two of these values.
  • the mass fraction of the carbon nanotubes is 0.05% to 5%, specifically 0.10%, 0.25%, 0.30%, 0.35%, 0.40%, 0.50%, 0.55% %, 0.60%, 0.65%, 0.70%, 0.75%, 0.80%, 1.0%, 1.25%, 1.5%, 1.75%, 2.0%, 2.25%, 2.50%, 2.75%, 3.0%, 3.25%, 3.5%, 3.75%, 4.0%, 4.25%, 4.5%, 5.0%, or a range of any two of these values.
  • the mass fraction of the amorphous carbon is 0.1% to 20%, specifically 0.1%, 0.5%, 1.0%, 1.5%, 2%, 3%, 5% %, 8%, 10%, 12%, 15%, 18%, or a range of any two of these values.
  • the graphite includes at least one of artificial graphite or natural graphite, wherein the artificial graphite or natural graphite includes at least one of mesocarbon microspheres or hard carbon.
  • the carbon nanotubes comprise single-walled carbon nanotubes, multi-walled carbon nanotubes, or a combination of both.
  • the amorphous carbon is obtained by carbonization of organic matter, wherein the organic matter includes selected from carboxymethyl cellulose and its metal salts, polyvinylpyrrolidone, polyacrylate, polyimide, polyamide, polyamideimide, polyamide At least one of vinylidene fluoride, styrene-butadiene rubber, sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, polyacrylonitrile, alkane, alkene or alkyne.
  • the organic matter includes selected from carboxymethyl cellulose and its metal salts, polyvinylpyrrolidone, polyacrylate, polyimide, polyamide, polyamideimide, polyamide At least one of vinylidene fluoride, styrene-butadiene rubber, sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, polyacrylonitrile, alkane, alkene or alkyne.
  • the negative electrode active material provided by this application uses silicon oxide and graphite for composite granulation, and protects carbon nanotubes and amorphous carbon on silicon and graphite, which acts as a bridge, strengthens the contact between silicon oxide and graphite, and improves the Conductivity, and suppresses the volume expansion of silicon oxide.
  • This composite anode active material not only improves the conductive interface between silicon and graphite, but also carbon nanotubes and amorphous carbon can not only stabilize the structure of the material, but also improve the conductivity of the material, thereby improving the cycle performance, expansion rate and kinetics of the hybrid anode. .
  • the preparation method of the negative electrode active material provided by this application includes:
  • Step A the silicon oxide and graphite are mixed in a solvent to form a first mixture
  • Step B mixing carbon nanotubes with the first mixture to form a second mixture
  • Step C the second mixture is spray-dried to form granulation
  • Step D The granulated product obtained in Step C is sintered under an inert atmosphere.
  • the general formula of the silicon oxide is SiO X , 0.5 ⁇ x ⁇ 1.6, 2 ⁇ b/a ⁇ 6, a represents the average particle size of the silicon oxide, and b represents the graphite The average particle size.
  • the average particle size of the silicon oxide is 2 ⁇ m to 6 ⁇ m, and specifically, may be 2 ⁇ m, 2.5 ⁇ m, 3 ⁇ m, 3.5 ⁇ m, 4 ⁇ m, 4.5 ⁇ m, 5 ⁇ m, 5.5 ⁇ m, 6 ⁇ m or these A range of any two of the values.
  • the average particle size of the graphite is 4.1 ⁇ m to 30 ⁇ m, and specifically, may be 5 ⁇ m, 5.5 ⁇ m, 6 ⁇ m, 6.5 ⁇ m, 7 ⁇ m, 7.5 ⁇ m, 8 ⁇ m, 9 ⁇ m, 10 ⁇ m, 11 ⁇ m, 12 ⁇ m , 13 ⁇ m, 14 ⁇ m, 15 ⁇ m, 16 ⁇ m, 17 ⁇ m, 18 ⁇ m, 19 ⁇ m, 20 ⁇ m, 23 ⁇ m, 25 ⁇ m, 28 ⁇ m, or a range of any two of these values.
  • the tube length of the carbon nanotube is d, which satisfies 1 ⁇ m ⁇ d ⁇ 15 ⁇ m, such as 1 ⁇ m, 2 ⁇ m, 5 ⁇ m, 8 ⁇ m, 10 ⁇ m, 12 ⁇ m or any two of these values. scope.
  • the carbon nanotubes are added to the first mixture in the form of carbon nanotube slurry and mixed therewith.
  • the carbon nanotube slurry includes carbon nanotubes and organic matter.
  • the organic matter can be selected from carboxymethyl cellulose and its metal salts, polyvinylpyrrolidone, polyacrylate, polyimide, polyamide, polyamideimide, polyvinylidene fluoride, styrene-butadiene rubber, At least one of sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, polyacrylonitrile, alkane, alkene or alkyne.
  • the solvent described in step A may be: water, ethanol, methanol, n-hexane, N,N-dimethylformamide, pyrrolidone, acetone, toluene, isopropanol, n-propyl alcohol One or more of alcohols and the like, among which water is preferred.
  • the sintering temperature in step D may be a certain temperature in the temperature range of 450°C to 1100°C, preferably 500°C to 900°C, more preferably 500°C to 700°C. According to some embodiments, the sintering temperature is in the range of 575°C to 625°C, eg, 600°C.
  • the inert atmosphere in step D may be one or a mixture of nitrogen and argon. Nitrogen is preferred.
  • the negative electrode provided by the present application includes the negative electrode active material described in the first aspect of the present application.
  • the negative electrode provided by the present application further includes a conductive agent and a binder.
  • the negative electrode further includes a current collector on which the negative electrode active material is located.
  • the current collector comprises: copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrate coated with conductive metal, or any combination thereof.
  • binders include, but are not limited to: polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-containing Oxygen polymer, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylic (esterified) styrene-butadiene rubber, epoxy resin or Nylon etc.
  • conductive agents include, but are not limited to, carbon-based materials, metal-based materials, conductive polymers, and mixtures thereof.
  • the carbon-based material is selected from natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, or any combination thereof.
  • the metal-based material is selected from metal powders, metal fibers, copper, nickel, aluminum, or silver.
  • the conductive polymer is a polyphenylene derivative.
  • the 5t compaction of the negative electrode is P
  • the mass fraction of carbon nanotubes (relative to the total mass of the negative electrode active material) is n
  • P the mass fraction of carbon nanotubes
  • the sheet resistance of the anode of the anode active material is less than 1 ohm.
  • the negative electrode of the present invention can be prepared by a known method in the art. Usually, the negative electrode active material and optional conductive agent (such as carbon black and other carbon materials and metal particles, etc.), binder (such as SBR), other optional additives (such as PTC thermistor material) and other materials are mixed in Disperse together in a solvent (such as deionized water), uniformly coat the negative electrode current collector after stirring evenly, and obtain a negative electrode containing a negative electrode membrane after drying.
  • a solvent such as deionized water
  • a material such as a metal foil or a porous metal plate can be used as the negative electrode current collector.
  • Embodiments of the present application provide an electrochemical device including a negative electrode, a positive electrode, an electrolyte, and a separator.
  • the electrochemical device of the present application includes a positive electrode having a positive electrode active material capable of occluding and releasing metal ions; a negative electrode according to the present application; an electrolyte; and a separator interposed between the positive electrode and the negative electrode.
  • the negative electrode in the electrochemical device of the present application includes the negative electrode active material of the present application.
  • Materials, compositions, and methods of making the positive electrodes that can be used in embodiments of the present application include any of those disclosed in the prior art.
  • the positive electrode includes a current collector and a layer of positive active material on the current collector.
  • the positive active material includes, but is not limited to: lithium cobalt oxide (LiCoO 2 ), lithium nickel cobalt manganese (NCM) ternary material, lithium iron phosphate (LiFePO 4 ), or lithium manganate (LiMn 2 O 4 ).
  • the positive active material layer further includes a binder, and optionally a conductive material.
  • the binder improves the bonding of the positive electrode active material particles to each other, and also improves the bonding of the positive electrode active material to the current collector.
  • binders include, but are not limited to: polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-containing Oxygen polymer, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylic (esterified) styrene-butadiene rubber, epoxy resin or Nylon etc.
  • conductive materials include, but are not limited to, carbon-based materials, metal-based materials, conductive polymers, and mixtures thereof.
  • the carbon-based material is selected from natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, or any combination thereof.
  • the metal-based material is selected from metal powders, metal fibers, copper, nickel, aluminum, or silver.
  • the conductive polymer is a polyphenylene derivative.
  • the current collector may include, but is not limited to, aluminum.
  • the positive electrode can be prepared by a preparation method known in the art.
  • the positive electrode can be obtained by mixing an active material, a conductive material, and a binder in a solvent to prepare an active material composition, and coating the active material composition on a current collector.
  • the solvent may include, but is not limited to: N-methylpyrrolidone.
  • the electrolyte that can be used in the embodiments of the present application may be an electrolyte known in the prior art.
  • the electrolyte includes an organic solvent, a lithium salt, and an additive.
  • the organic solvent of the electrolyte solution according to the present application can be any organic solvent known in the prior art that can be used as a solvent of the electrolyte solution.
  • the electrolyte used in the electrolyte solution according to the present application is not limited, and it may be any electrolyte known in the prior art.
  • the additive for the electrolyte according to the present application may be any additive known in the art as an additive for the electrolyte.
  • the organic solvent includes, but is not limited to: ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate or ethyl propionate.
  • the lithium salt includes at least one of an organic lithium salt or an inorganic lithium salt.
  • the lithium salts include, but are not limited to: lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium difluorophosphate (LiPO 2 F 2 ), bistrifluoromethanesulfonimide Lithium LiN(CF 3 SO 2 ) 2 (LiTFSI), Lithium Bis(fluorosulfonyl)imide Li(N(SO 2 F) 2 )(LiFSI), Lithium Bisoxalate Borate LiB(C 2 O 4 ) 2 (LiBOB) ) or lithium difluorooxalate borate LiBF 2 (C 2 O 4 ) (LiDFOB).
  • LiPF 6 lithium hexafluorophosphate
  • LiBF 4 lithium tetrafluoroborate
  • LiPO 2 F 2 lithium difluorophosphate
  • LiPFSI bistrifluoromethanesulfonimide Lithium LiN(CF 3 SO
  • the concentration of the lithium salt in the electrolyte is: 0.5 mol/L to 3 mol/L, 0.5 mol/L to 2 mol/L, or 0.8 mol/L to 1.5 mol/L.
  • a separator is provided between the positive electrode and the negative electrode to prevent short circuits.
  • the material and shape of the isolation membrane that can be used in the embodiments of the present application are not particularly limited, and may be any of the techniques disclosed in the prior art.
  • the separator includes a polymer or inorganic or the like formed from a material that is stable to the electrolyte of the present application.
  • the release film may include a substrate layer and a surface treatment layer.
  • the base material layer is a non-woven fabric, film or composite film with a porous structure, and the material of the base material layer includes at least one of polyethylene, polypropylene, polyethylene terephthalate or 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 include aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, ceria, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, oxide At least one of yttrium, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate.
  • Binders include polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinyl At least one of methyl methacrylate, polytetrafluoroethylene or polyhexafluoropropylene.
  • the polymer layer contains a polymer, and the material of the polymer includes polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride or poly( At least one of vinylidene fluoride-hexafluoropropylene).
  • the electrochemical devices of the present application include, but are not limited to, all kinds of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors.
  • the electrochemical device is a lithium secondary battery.
  • the lithium secondary battery includes, but is not limited to, a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.
  • the electronic device of the present application may be any device using the electrochemical device according to the fourth aspect of the present application.
  • the electronic devices 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 or lithium-ion capacitors, etc.
  • the preparation process of the negative electrode active materials of Examples 1 to 13 and Comparative Examples 1 to 2 is as follows:
  • step 3 Sinter the dry powder in step 2 in a nitrogen atmosphere, the nitrogen flow rate is 0.5 to 1.5 L/min, the furnace body is kept at normal pressure, the sintering temperature is 600° C., and the sintering time is 2 hours.
  • the thickness of the amorphous carbon was 20 nm to 50 nm because the dry powder was controlled in a sintering process under a nitrogen atmosphere.
  • the main function of amorphous carbon is to cooperate with carbon nanotubes to increase the conductivity of the matrix silicon oxide, and at the same time to enhance the contact between the granulated silicon oxide and graphite, and to improve the interface contact.
  • the thickness of amorphous carbon needs to be controlled below 500 nm, too thick amorphous carbon cannot ensure ion conduction and long-range conductivity of carbon nanotubes.
  • Particle size test of negative electrode active material add about 0.02g powder sample to a 50ml clean beaker, add about 20ml deionized water, and then add a few drops of 1% surfactant to make the powder completely dispersed in water, 120W ultrasonic cleaning machine Ultrasonic for 5 minutes, using MasterSizer 2000 to test the particle size, that is, the Dv50 of the negative electrode active material, Dv50 represents the particle size of the material in the particle size distribution of the volume reference, starting from the small particle size side, reaching 50% of the volume cumulative particle size.
  • Particle size test (average particle size): take a cross-section SEM photograph of the pole piece, select a multiple of 500X, select the backscatter mode, and randomly pick 100 graphite or silicon particles to measure the maximum diameter of the particles (the interval on the boundary of the particles). The average particle size of the farthest distance), that is, the average particle size, obtains the average particle size of graphite and the average particle size of silicon oxide.
  • the active material LiCoO 2 , conductive carbon black, and binder polyvinylidene fluoride (PVDF) were fully stirred and mixed in the N-methylpyrrolidone solvent system in a weight ratio of 96.7:1.7:1.6, and then coated on Al foil After drying and cold pressing, a positive electrode is obtained.
  • the silicon material in the embodiment is mixed according to a certain proportion to design a mixed powder with a gram capacity of 500mAh/g, and the mixed negative electrode, conductive agent acetylene black, and polyacrylic acid (PAA) are mixed in a deionized water solvent according to a weight ratio of 95:1.2:3.8. After fully stirring and mixing in the system, it is coated on Cu foil for drying and cold pressing to obtain a negative electrode.
  • the PE porous polymer film is used as the separator.
  • the positive electrode, the separator and the negative electrode are stacked in sequence, so that the separator is placed between the negative electrode and the negative electrode to play a role of isolation, and the bare cell is obtained by winding.
  • the bare cell is placed in the outer package, the prepared electrolyte is injected and packaged, and the full cell is obtained through the process of formation, degassing, and trimming.
  • the test temperature is 25°C or 45°C, charge to 4.45V with 0.7C constant current, charge to 0.025C with constant voltage, and discharge to 3.0V with 0.5C after standing for 5 minutes.
  • take the capacity obtained in this step as the initial capacity, perform 0.7C charge/0.5C discharge for cycle test, then perform cycle charge and discharge, and record the discharge capacity value of each cycle, and use the following formula to calculate the cycle capacity retention rate: Cycle The N-th cycle capacity retention rate (the discharge capacity of the N-th cycle/the discharge capacity of the first cycle) ⁇ 100%.
  • Examples 1 to 4 and Comparative Example 3 show that because the particle size of silicon particles is smaller than that of graphite, as the silicon content of the composite particles increases, the particle size of the composite particles decreases and the BET also increases. Compared with Comparative Example 3, although the silicon content is increased, the cycle can still be improved. Therefore, the silicon-carbon composite is selected to satisfy the following relationship: 2 ⁇ b/a ⁇ 6, where a represents the average particle size of silicon oxide, and b represents the average particle size of graphite, and a suitable particle size range of silicon-oxygen and graphite is obtained by recycling In order to improve, the cell expansion rate of 25°C cycle up to 400 cycles and the cell expansion rate of 45°C cycle up to 400 cycles were also improved.
  • LiFSI molar mass is 187.07 g/mol
  • LiPF 6 molar mass is 151.91 g/mol.
  • LiFSI lithium salt bis(fluorosulfonyl)imide

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Abstract

一种负极活性材料、电化学装置和电子装置。该负极活性材料包括硅碳复合物，其中，所述硅碳复合物包括硅氧化物和石墨，所述硅氧化物的通式为SiOX，0.5≤x≤1.6，所述硅碳复合物满足以下关系式：2≤b/a<6，其中a表示硅氧化物的平均粒径，b表示石墨的平均粒径。

Description

负极活性材料、电化学装置和电子装置
相关申请的交叉引用
本申请基于申请号为202011623085.0、申请日为2020年12月31日，名称为“负极活性材料、电化学装置和电子装置”的中国专利申请提出，并要求该中国专利申请的优先权，该中国专利申请的全部内容在此引入本申请作为参考。
技术领域
本申请涉及锂离子电池领域。具体地，本申请涉及一种负极活性材料及其制备方法。本申请还涉及包括该负极活性材料的负极、电化学装置和电子装置。
背景技术
近年来，由于硅的可逆容量高达4200mAh/g，被认为最有可能被大规模应用的锂离子负极活性材料。由于充放电过程中材料会发生膨胀与收缩，紧密的保护结构可以有效缓解这个过程中结构的破坏。另一方面材料的破坏会产生新鲜界面，多次循环会产生大量的SEI副产物，当界面结合不紧密、不牢固时，这层副产物会推动和加速碳层的剥离，从而加速材料衰减与失效。
提升硅氧材料循环性能的主要手段包括以下几种：碳保护硅氧材料、碳保护硅氧材料中间设置中间空隙层、降低硅氧材料的尺寸、聚合物保护硅氧材料、无定形氧化物保护硅氧材料等。在这些保护手段中，碳保护硅氧材料由于电子导电性能比较好、稳定性高而成为目前的主要应用方向。但是碳保护硅氧材料很可能在电池极片加工过程中由于反复剪切力造成脱碳现象，影响库伦效率，并且SEI膜(固体电解质界面膜)的生成消耗电解液。另一方 面，多次的循环过程中硅的膨胀收缩和破裂，导致碳层很容易从基体上剥落，随着SEI的生成，碳层被副产物包裹，从而极大地增加电化学阻抗和极化，影响循环寿命。因此提高碳层与硅氧材料的界面结合性能对于改善循环寿命、提高循环结构稳定性具有重要意义。
聚合物保护硅氧材料和无定形氧化物保护硅氧材料虽然能够有效避免电解液与硅氧材料直接接触，但由于聚合物和无定形氧化物的导电性较差，会增加电化学阻抗和极化，不但使得硅氧材料无法有效脱嵌锂，而且保护层容易在脱嵌锂时被破坏，影响循环寿命。因此在避免电解液与硅氧材料直接接触的同时，提高硅氧材料的导电性，抑制硅氧材料体积膨胀对于改善负极活性材料的循环寿命和提高循环结构稳定性具有重要意义。
发明内容
针对现有技术的不足，本申请在第一方面提供了一种负极活性材料，该负极活性材料作为锂离子电池负极活性材料能够提高循环寿命和循环结构稳定性。
本申请提供的负极活性材料包括硅碳复合物，其中，所述硅碳复合物包括硅氧化物和石墨，所述硅氧化物的通式为SiO X，0.5≤x≤1.6，所述硅碳复合物满足以下关系式：2≤b/a<6，其中a表示硅氧化物的平均粒径，b表示石墨的平均粒径。本申请的发明人通过研究发现，SiO X和石墨的平均粒径满足2≤b/a<6的情况下，才能达到合适的造粒粒径和更好的循环改善。
根据本申请的一些优选实施例，硅氧化物的平均粒径为2μm至6μm。根据本申请的一些优选实施例，石墨的平均粒径为4.1μm至30μm。合适粒径范围的硅氧化物和石墨搭配，能有效的改善负极活性材料的循环性能。
根据本申请的一些优选实施例，c表示负极活性材料的Dv50，c为6.1μm至60μm，通过造粒工艺，选择粒径在合适范围的负极活性材料。
根据本申请的一些优选实施例，所述负极活性材料满足以下关系式：a+b≤c≤5b，a表示硅氧化物的平均粒径，b表示石墨的平均粒径，c表示负极活性材料的Dv50。当负极活性材料的Dv50满足该关系时，能达到更加合适的造粒粒径和更好的循环改善。
根据本申请的一些优选实施例，所述负极活性材料还包括位于所述硅碳复合物表面的保护层。根据一些优选实施例，所述保护层包括碳纳米管、无定形碳或石墨烯中的至少一种。碳纳米管包裹在石墨和SiO X外表，提高SiO X和石墨结合，同时穿插于SiO X和石墨之间，提升材料离子和电子电导率；所述无定形碳保护于石墨和SiO X表面，同时和碳纳米管接触，起到粘接作用，抑制氧化亚硅的体积膨胀。所述负极活性材料中，此保护层不仅改善硅和石墨的导电界面，还能提高材料的导电性，从而改善混合负极的循环性能、膨胀率和动力学。
根据本申请的一些优选实施例，所述保护层包括第一保护物和第二保护物，第一保护物包括碳纳米管、无定形碳或石墨烯中的至少一种，第二保护物包括碳纳米管、无定形碳或石墨烯中的至少一种；根据本申请的一些优选实施例，所述碳纳米管的管长为d，1μm≤d≤15μm；根据本申请的一些优选实施例，基于负极活性材料，所述保护层的质量分数为0.05％至5％。
根据本申请的一些优选实施例，所述保护层包括第一保护物和第二保护物，第一保护物包括碳纳米管、无定形碳或石墨烯中的至少一种，第二保护物包括碳纳米管、无定形碳或石墨烯中的至少一种。碳纳米管包裹在石墨和SiO X外表，提高SiO X和石墨结合，同时穿插于SiO X和石墨之间，提升材料离子和电子电导率；所述无定形碳保护于石墨和SiO X表面，同时和碳纳米管接触，起到粘接作用，抑制氧化亚硅的体积膨胀。该保护层不仅改善硅和石墨的导电界面，还能提高材料的导电性，从而改善负极的循环性能、膨胀率和动力学。
根据本申请的一些优选实施例，所述碳纳米管的管长为d，1μm≤d≤15μm。一定长度的碳纳米管可提供循环过程中颗粒之间的长程导电性，碳纳米管的长度太短对于改善循环过程中颗粒之间的长程导电性效果不明显，碳纳米管的长度太长，容易导致颗粒团聚，膨胀增大。
根据本申请的一些优选实施例，基于负极活性材料，所述保护层的质量分数为0.05％至5％。负极活性材料中，保护层的作用是保护负极活性材料界面，避免更多的颗粒表面和电解液直接接触，但是保护层质量分数太高，容易导致保护层更多的副反应。
根据本申请的一些优选实施例，所述保护层包括第一保护物和第二保护物，所述第一保护物和所述第二保护物相接触，所述第一保护物的厚度为20nm至300nm，所述第二保护物的厚度为20nm至500nm。该厚度为从第一保护物接触硅碳复合物(SiO X/石墨)到接触第二保护物即无定形碳的垂直距离。所述第二保护物的厚度为20nm至500nm，该厚度为从SiO X表面且垂直表面方向上开始算厚度。无定形碳厚度需控制在500nm以下，太厚的无定形碳无法保证离子的传导以及碳纳米管的长程导电性。
根据本申请的一些优选实施例，所述负极活性材料的比表面积为1m 2/g至50m 2/g；根据本申请的一些优选实施例，基于负极活性材料，所述硅氧化物的质量分数为5％至50％，所述石墨的质量分数为25％至93.5％。
根据本申请的一些优选实施例，所述负极活性材料的比表面积为1.11m 2/g至1.59m 2/g。负极活性材料的比表面积太高容易造成循环的副反应。
根据本申请的一些实施例，所述石墨包括人造石墨或天然石墨中至少一种，其中所述人造石墨或天然石墨包括中间相碳微球或硬碳中至少一种。所述碳纳米管包含单壁碳纳米管、多壁碳纳米管或二者组合。所述无定形碳由有机物碳化得到，其中所述有机物包括选自羧甲基纤维素及其金属盐、聚乙烯吡咯烷酮、聚丙烯酸酯、聚酰亚胺、聚酰胺、聚酰胺酰亚胺、聚偏氟乙烯、 丁苯橡胶、海藻酸钠、聚乙烯醇、聚四氟乙烯、聚丙烯腈、烷烃、烯烃或炔烃中的至少一种。本申请提供的负极活性材料使用氧化亚硅和石墨进行复合造粒，并将碳纳米管和无定形碳保护于硅和石墨，起到桥架作用，加强氧化亚硅和石墨之间的接触，提高导电性，并抑制氧化亚硅的体积膨胀，从而改善负极的循环性能、膨胀率和动力学。
本申请第二方面提供了一种第一方面所述负极活性材料的制备方法，包括以下步骤：步骤A、将硅氧化物和石墨在溶剂中进行混合，形成第一混合物；步骤B、将碳纳米管与所述第一混合物进行混合，形成第二混合物；步骤C、将第二混合物进行喷雾干燥形成造粒；步骤D、将步骤C所得造粒产物在惰性气氛下进行烧结。
在第三方面，本申请提供了一种负极，该负极包括本申请第一方面所述的负极活性材料。
根据本申请的一些实施例，所述负极还包括导电剂和粘结剂。
根据本申请的一些实施例，负极的5t压密为P，碳纳米管质量分数(相对于所述负极活性材料总质量)为n，当0.05％＜n＜3.2％，P随着n增大而增大。
根据本申请的一些进一步的实施例，在相同硅含量的负极，所述的负极活性材料的负极，其膜片电阻小于1欧姆。
本发明的负极可以采用本领域的公知方法进行制备。通常，将负极活性材料以及可选的导电剂(例如碳黑等碳素材料和金属颗粒等)、粘结剂(例如SBR)、其他可选添加剂(例如PTC热敏电阻材料)等材料混合在一起分散于溶剂(例如去离子水)中，搅拌均匀后均匀涂覆在负极集流体上，烘干后即得到含有负极膜片的负极。可以使用金属箔或多孔金属板等材料作为负极集流体。
在第四方面，本申请提供了一种电化学装置，其包括负极，所述负极包 含如本申请第一方面所述的负极活性材料。
在第四方面，本申请提供了一种电化学装置，其包括电解液，所述电解液还包括锂盐，所述锂盐包括双(氟磺酰基)酰亚胺锂(LiFSI)和六氟磷酸锂(LiPF 6)，根据本申请的一些实施例，锂盐的浓度为1mo l/L至2mo l/L，且双(氟磺酰基)酰亚胺锂和六氟磷酸锂的质量比为0.06至5。通过调控与LiFSI与LiPF 6的质量比，改善了电芯循环性能和膨胀性能，这主要是因为，负极材料中的硅碳复合物和电解液中锂盐相互作用，改善负极和电解液之间的接触，从而改善其循环性能。
根据本申请的一些实施例，在所述电化学装置中，所述负极活性材料还包括位于所述硅碳复合物表面的保护层，所述保护层包括碳纳米管、无定形碳或石墨烯中的至少一种。
根据本申请的一些实施例，在所述电化学装置中，所述保护层包括第一保护物和第二保护物，所述第一保护物的厚度为20nm至300nm，所述第二保护物的厚度为20nm至500nm。
根据本申请的一些实施例，所述保护层包括第一保护物和第二保护物，第一保护物包括碳纳米管、无定形碳或石墨烯中的至少一种，第二保护物包括碳纳米管、无定形碳或石墨烯中的至少一种；根据本申请的一些优选实施例，所述碳纳米管的管长为d，1μm≤d≤15μm；根据本申请的一些优选实施例，基于负极活性材料，所述保护层的质量分数为0.05％至5％。
根据本申请的一些实施例，在所述电化学装置中，所述负极活性材料的比表面积为1m 2/g至50m 2/g；根据本申请的一些优选实施例，基于负极活性材料，所述硅氧化物的质量分数为5％至50％，所述石墨的质量分数为25％至93.5％；根据本申请的一些优选实施例，a为2μm至6μm；根据本申请的一些优选实施例，b为4.1μm至30μm；根据本申请的一些优选实施例，c表示负极活性材料的Dv50，c为6.1μm至60μm；根据本申请的一些优选实施例，c 表示负极活性材料的Dv50，a+b≤c≤5b。
本申请的电化学装置是指能够发生电化学反应的任何装置，它的具体实例包括所有种类的一次电池、二次电池、燃料电池、太阳能电池或电容。特别地，该电化学装置是锂二次电池，包括锂金属二次电池、锂离子二次电池、锂聚合物二次电池或锂离子聚合物二次电池。
在第五个方面，本申请进一步提供了一种电子装置，其包括本申请第三方面所述的电化学装置。
本申请的电子装置没有特别限定。在一些实施例中，本申请的电子装置包括但不限于，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。
本申请提供的负极活性材料通过SiO X和石墨的中位粒径满足2≤b/a<6，达到合适的造粒粒径和更好的循环改善。该负极活性材料用于锂离子电池的负极，能够提高循环寿命和循环结构稳定性。
附图说明
图1为根据本申请的实施方式的负极活性材料的结构示意图。
图2为根据本申请的实施例1的负极活性材料的SEM图。
图3为根据本申请的实施例3的负极活性材料的SEM图。
图4为根据本申请的实施例1的负极的截面图。
具体实施方式
为了简明，本文仅具体地公开了一些数值范围。然而，任意下限可以与任何上限组合形成未明确记载的范围；以及任意下限可以与其它下限组合形成未明确记载的范围，同样任意上限可以与任意其它上限组合形成未明确记载的范围。此外，每个单独公开的点或单个数值自身可以作为下限或上限与任意其它点或单个数值组合或与其它下限或上限组合形成未明确记载的范围。
在本文的描述中，除非另有说明，“以上”、“以下”包含本数。
除非另有说明，本申请中使用的术语具有本领域技术人员通常所理解的公知含义。除非另有说明，本申请中提到的各参数的数值可以用本领域常用的各种测量方法进行测量(例如，可以按照在本申请的实施例中给出的方法进行测试)。
术语“中的至少一者”、“中的至少一个”、“中的至少一种”或其他相似术语所连接的项目的列表可意味着所列项目的任何组合。例如，如果列出项目A及B，那么短语“A及B中的至少一者”意味着仅A；仅B；或A及B。在另一实例中，如果列出项目A、B及C，那么短语“A、B及C中的至少一者”意味着仅A；或仅B；仅C；A及B(排除C)；A及C(排除B)；B及C(排除A)；或A、B及C的全部。项目A可包含单个组分或多个组分。项目B可包含单个组分或多个组分。项目C可包含单个组分或多个组分。
一、负极活性材料
本申请提供的负极活性材料包括硅碳复合物，所述硅碳复合物包括硅氧化物和石墨，所述硅氧化物的通式为SiO X，0.5≤x≤1.6，所述硅碳复合物满足以下关系式：2≤b/a<6，其中a表示硅氧化物的平均粒径，b表示石墨的平均粒径。本申请的发明人通过研究发现，SiO X和石墨的中位粒径满足2≤b/a<6的情况下，才能达到合适的造粒粒径和更好的循环改善。
根据本申请的一些优选实施例，硅氧化物的平均粒径为2μm至6μm，石 墨的平均粒径为4.1μm至30μm。若硅氧化物的平均粒径过大或过小，都会影响其循环，合适粒径范围的硅氧化物和石墨搭配，能有效的改善负极活性材料的循环性能。
根据本申请的一些实施例，硅氧化物的平均粒径为2μm至6μm，具体地，可以是2μm、2.5μm、3μm、3.5μm、4μm、4.5μm、5μm、5.5μm、6μm或者这些数值中任意两者组成的范围。
根据本申请的一些实施例，石墨的平均粒径为4.1μm至30μm，具体地，可以是5μm、5.5μm、6μm、6.5μm、7μm、7.5μm、8μm、9μm、10μm、11μm、12μm、13μm、14μm、15μm、16μm、17μm、18μm、19μm、20μm、23μm、25μm、28μm或者这些数值中任意两者组成的范围。
根据本申请的一些优选实施例，c表示负极活性材料的Dv50，c为6.1μm至60μm，通过造粒工艺，选择粒径在合适范围的负极活性材料。
根据本申请的一些优选实施例，所述负极活性材料满足以下关系式：a+b≤c≤5b，a表示硅氧化物的平均粒径，b表示石墨的平均粒径，c表示负极活性材料的Dv50。当负极活性材料的Dv50满足该关系时，能达到更加合适的造粒粒径和更好的循环改善。根据本申请的一些实施例，负极活性材料的Dv50为6.1μm至60μm，具体地，可以是6.5μm、7μm、7.5μm、8μm、9μm、10μm、11μm、12μm、13μm、14μm、15μm、16μm、17μm、18μm、19μm、20μm、23μm、25μm、28μm、30μm、35μm、38μm、42μm、45μm、48μm、50μm、55μm或者这些数值中任意两者组成的范围。
根据本申请的一些优选实施例，所述负极活性材料还包括位于所述硅碳复合物表面的保护层。根据一些优选实施例，所述保护层包括碳纳米管、无定形碳或石墨烯中的至少一种。碳纳米管包裹在石墨和SiO X外表，提高SiO X和石墨结合，同时穿插于SiO X和石墨之间，提升材料离子和电子电导率；所述无定形碳保护于石墨和SiO X表面，同时和碳纳米管接触，起到粘接作用， 抑制氧化亚硅的体积膨胀。所述负极活性材料中，此保护层不仅改善硅和石墨的导电界面，还能提高材料的导电性，从而改善混合负极的循环性能、膨胀率和动力学。
根据本申请的一些优选实施例，所述保护层包括第一保护物和第二保护物，所述第一保护物和所述第二保护物相接触，所述第一保护物的厚度为20nm至300nm，所述第二保护物的厚度为20nm至500nm。该厚度为从第一保护物接触硅碳复合物(SiO X/石墨)到接触第二保护物即无定形碳的垂直距离。所述第二保护物的厚度为20nm至500nm，该厚度为属于非规则保护，从SiO X表面开始算厚度。在一些实施例中，所述第一保护物的厚度为20nm、30nm、50nm、80nm、100nm、120nm、150nm、180nm、200nm、250nm、300nm或者这些数值中任意两者组成的范围。在一些实施例中，所述第二保护物的厚度为20nm、30nm、50nm、80nm、100nm、120nm、150nm、180nm、200nm、250nm、300nm、320nm、350nm、500nm、400nm或者这些数值中任意两者组成的范围。无定形碳厚度需控制在500nm以下，太厚的无定形碳无法保证离子的传导以及碳纳米管的长程导电性。
根据本申请的一些优选实施例，所述负极活性材料的比表面积为1m 2/g至50m 2/g，例如1m 2/g、5m 2/g、8m 2/g、10m 2/g、15m 2/g、18m 2/g、23m 2/g、m 2/g、30m 2/g、38m 2/g、42m 2/g、48m 2/g或者这些数值中任意两者组成的范围。负极活性材料的比表面积太高容易造成循环的副反应。
根据本申请的一些优选实施例，所述碳纳米管的管长为d，1μm≤d≤15μm，例如1μm、2μm、5μm、8μm、10μm、12μm或者这些数值中任意两者组成的范围。一定长度的碳纳米管可提供循环过程中颗粒之间的长程导电性，碳纳米管的长度太短对于改善循环过程中颗粒之间的长程导电性效果不明显，碳纳米管的长度太长，容易导致颗粒团聚，膨胀增大。
根据本申请的一些优选实施例，基于负极活性材料，所述保护层的质量 分数为0.05％至5％。负极活性材料中，保护层的作用是保护负极活性材料界面，避免更多的颗粒表面和电解液直接接触，但是保护层质量分数太高，容易导致保护层更多的副反应。
根据本申请的一些实施例，基于负极活性材料，所述硅氧化物的质量分数为5％至50％，具体可以为5％、8％、10％、12％、15％、20％、25％、30％、35％、40％、45％或者这些数值中任意两者组成的范围。
根据本申请的一些实施例，基于负极活性材料，所述石墨的质量分数为25％至93.5％，具体可以为25％、28％、30％、35％、40％、50％、55％、60％、65％、70％、75％、80％、85％、90％或者这些数值中任意两者组成的范围。
根据本申请的一些实施例，基于负极活性材料，所述碳纳米管的质量分数为0.05％至5％，具体可以为0.10％、0.25％、0.30％、0.35％、0.40％、0.50％、0.55％、0.60％、0.65％、0.70％、0.75％、0.80％、1.0％、1.25％、1.5％、1.75％、2.0％、2.25％、2.50％、2.75％、3.0％、3.25％、3.5％、3.75％、4.0％、4.25％、4.5％、5.0％或者这些数值中任意两者组成的范围。
根据本申请的一些实施例，基于负极活性材料，所述无定形碳的质量分数为0.1％至20％，具体可以为0.1％、0.5％、1.0％、1.5％、2％、3％、5％、8％、10％、12％、15％、18％或者这些数值中任意两者组成的范围。
根据本申请的一些实施例，所述石墨包括人造石墨或天然石墨中至少一种，其中所述人造石墨或天然石墨包括中间相碳微球或硬碳中至少一种。所述碳纳米管包含单壁碳纳米管、多壁碳纳米管或二者组合。所述无定形碳由有机物碳化得到，其中所述有机物包括选自羧甲基纤维素及其金属盐、聚乙烯吡咯烷酮、聚丙烯酸酯、聚酰亚胺、聚酰胺、聚酰胺酰亚胺、聚偏氟乙烯、丁苯橡胶、海藻酸钠、聚乙烯醇、聚四氟乙烯、聚丙烯腈、烷烃、烯烃或炔烃中的至少一种。本申请提供的负极活性材料使用氧化亚硅和石墨进行复合造粒，并将碳纳米管和无定形碳保护于硅和石墨，起到桥架作用，加强氧化 亚硅和石墨之间的接触，提高导电性，并抑制氧化亚硅的体积膨胀。此复合负极活性材料，不仅改善硅和石墨的导电界面，碳纳米管和无定形碳不仅能够稳定材料的结构，还能提高材料的导电性，从而改善混合负极的循环性能、膨胀率和动力学。
二、负极活性材料的制备方法
本申请提供的负极活性材料的制备方法包括：
步骤A、将硅氧化物和石墨在溶剂中进行混合，形成第一混合物；
步骤B、将碳纳米管与所述第一混合物进行混合，形成第二混合物；
步骤C、将第二混合物进行喷雾干燥形成造粒；
步骤D、将步骤C所得造粒产物在惰性气氛下进行烧结。
在上述制备方法的一些实施例中，所述硅氧化物的通式为SiO X，0.5≤x≤1.6，2≤b/a<6，a表示硅氧化物的平均粒径，b表示石墨的平均粒径。
在上述制备方法的一些实施例中，硅氧化物的平均粒径为2μm至6μm，具体地，可以是2μm、2.5μm、3μm、3.5μm、4μm、4.5μm、5μm、5.5μm、6μm或者这些数值中任意两者组成的范围。
在上述制备方法的一些实施例中，石墨的平均粒径为4.1μm至30μm，具体地，可以是5μm、5.5μm、6μm、6.5μm、7μm、7.5μm、8μm、9μm、10μm、11μm、12μm、13μm、14μm、15μm、16μm、17μm、18μm、19μm、20μm、23μm、25μm、28μm或者这些数值中任意两者组成的范围。
在上述制备方法的一些实施例中，所述碳纳米管的管长为d，其满足1μm≤d≤15μm，例如1μm、2μm、5μm、8μm、10μm、12μm或者这些数值中任意两者组成的范围。
在上述制备方法的一些实施例中，在步骤B中，所述碳纳米管以碳纳米管浆料的形式加入到第一混合物中与其进行混合。根据本申请的实施例，所述碳纳米管浆料中包括碳纳米管和有机物。具体地，所述有机物可选自羧甲 基纤维素及其金属盐、聚乙烯吡咯烷酮、聚丙烯酸酯、聚酰亚胺、聚酰胺、聚酰胺酰亚胺、聚偏氟乙烯、丁苯橡胶、海藻酸钠、聚乙烯醇、聚四氟乙烯、聚丙烯腈、烷烃、烯烃或炔烃中的至少一种。
在上述制备方法的一些实施例中，步骤A中所述溶剂可以是：水、乙醇、甲醇、正己烷、N,N-二甲基甲酰胺、吡咯烷酮、丙酮、甲苯、异丙醇、正丙醇等中的一种或者多种，其中优选水。
在上述制备方法的一些实施例中，步骤D中所述烧结温度可以为：450℃至1100℃的温度区间中某一温度，优选为500℃至900℃，更优选为500℃至700℃。根据一些是实施例，所述烧结温度在575℃至625℃范围内，例如600℃。
在上述制备方法的一些实施例中，步骤D中所述惰性气氛可以为氮气、氩气一种或者混合。优选氮气。
三、负极
在一些实施例中，本申请提供的负极包括本申请第一方面所述的负极活性材料。
在一些实施例中，本申请提供的负极还包括导电剂以及粘结剂。
在一些实施例中，所述负极还包括集流体，所述负极活性材料位于集流体上。
在一些实施例中，所述集流体包括：铜箔、镍箔、不锈钢箔、钛箔、泡沫镍、泡沫铜、覆有导电金属的聚合物基底或其任意组合。
在一些实施例中，粘结剂包括，但不限于：聚乙烯醇、羟丙基纤维素、二乙酰基纤维素、聚氯乙烯、羧化的聚氯乙烯、聚氟乙烯、含亚乙基氧的聚合物、聚乙烯吡咯烷酮、聚氨酯、聚四氟乙烯、聚偏1，1-二氟乙烯、聚乙烯、聚丙烯、丁苯橡胶、丙烯酸(酯)化的丁苯橡胶、环氧树脂或尼龙等。
在一些实施例中，导电剂包括，但不限于：基于碳的材料、基于金属的 材料、导电聚合物和它们的混合物。在一些实施例中，基于碳的材料选自天然石墨、人造石墨、碳黑、乙炔黑、科琴黑、碳纤维或其任意组合。在一些实施例中，基于金属的材料选自金属粉、金属纤维、铜、镍、铝或银。在一些实施例中，导电聚合物为聚亚苯基衍生物。
根据本申请的一些实施例，负极的5t压密为P，碳纳米管质量分数(相对于所述负极活性材料总质量)为n，当0.05％＜n＜3.2％，P随着n增大而增大。
根据本申请的一些进一步的实施例，在相同硅含量的负极，所述的负极活性材料的负极，其膜片电阻小于1欧姆。
本发明的负极可以采用本领域的公知方法进行制备。通常，将负极活性材料以及可选的导电剂(例如碳黑等碳素材料和金属颗粒等)、粘结剂(例如SBR)、其他可选添加剂(例如PTC热敏电阻材料)等材料混合在一起分散于溶剂(例如去离子水)中，搅拌均匀后均匀涂覆在负极集流体上，烘干后即得到含有负极膜片的负极。可以使用金属箔或多孔金属板等材料作为负极集流体。
四、电化学装置
本申请的实施例提供了一种电化学装置，所述电化学装置包括负极、正极、电解液和隔离膜。
在一些实施例中，本申请的电化学装置包括具有能够吸留、放出金属离子的正极活性物质的正极；根据本申请的负极；电解液；和置于正极和负极之间的隔离膜。
负极
本申请的电化学装置中的负极包括本申请的负极活性材料。
正极
可用于本申请的实施例中正极的材料、构成和其制造方法包括任何现有技术中公开的技术。
在一些实施例中，正极包括集流体和位于该集流体上的正极活性材料层。
在一些实施例中，正极活性材料包括，但不限于：钴酸锂(LiCoO 2)、锂镍钴锰(NCM)三元材料、磷酸亚铁锂(LiFePO 4)或锰酸锂(LiMn 2O 4)。
在一些实施例中，正极活性材料层还包括粘合剂，并且可选地包括导电材料。粘合剂提高正极活性材料颗粒彼此间的结合，并且还提高正极活性材料与集流体的结合。
在一些实施例中，粘合剂包括，但不限于：聚乙烯醇、羟丙基纤维素、二乙酰基纤维素、聚氯乙烯、羧化的聚氯乙烯、聚氟乙烯、含亚乙基氧的聚合物、聚乙烯吡咯烷酮、聚氨酯、聚四氟乙烯、聚偏1，1-二氟乙烯、聚乙烯、聚丙烯、丁苯橡胶、丙烯酸(酯)化的丁苯橡胶、环氧树脂或尼龙等。
在一些实施例中，导电材料包括，但不限于：基于碳的材料、基于金属的材料、导电聚合物和它们的混合物。在一些实施例中，基于碳的材料选自天然石墨、人造石墨、碳黑、乙炔黑、科琴黑、碳纤维或其任意组合。在一些实施例中，基于金属的材料选自金属粉、金属纤维、铜、镍、铝或银。在一些实施例中，导电聚合物为聚亚苯基衍生物。
在一些实施例中，集流体可以包括，但不限于：铝。
正极可以通过本领域公知的制备方法制备。例如，正极可以通过如下方法获得：在溶剂中将活性材料、导电材料和粘合剂混合，以制备活性材料组合物，并将该活性材料组合物涂覆在集流体上。在一些实施例中，溶剂可以包括，但不限于：N-甲基吡咯烷酮。
电解液
可用于本申请实施例的电解液可以为现有技术中已知的电解液。
在一些实施例中，所述电解液包括有机溶剂、锂盐和添加剂。根据本申 请的电解液的有机溶剂可为现有技术中已知的任何可作为电解液的溶剂的有机溶剂。根据本申请的电解液中使用的电解质没有限制，其可为现有技术中已知的任何电解质。根据本申请的电解液的添加剂可为现有技术中已知的任何可作为电解液添加剂的添加剂。
在一些实施例中，所述有机溶剂包括，但不限于：碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸二乙酯(DEC)、碳酸甲乙酯(EMC)、碳酸二甲酯(DMC)、碳酸亚丙酯或丙酸乙酯。
在一些实施例中，所述锂盐包括有机锂盐或无机锂盐中的至少一种。
在一些实施例中，所述锂盐包括，但不限于：六氟磷酸锂(LiPF 6)、四氟硼酸锂(LiBF 4)、二氟磷酸锂(LiPO 2F 2)、双三氟甲烷磺酰亚胺锂LiN(CF 3SO 2) 2(LiTFSI)、双(氟磺酰)亚胺锂Li(N(SO 2F) 2)(LiFSI)、双草酸硼酸锂LiB(C 2O 4) 2(LiBOB)或二氟草酸硼酸锂LiBF 2(C 2O 4)(LiDFOB)。
在一些实施例中，所述电解液中锂盐的浓度为：0.5mol/L至3mol/L、0.5mol/L至2mol/L或0.8mol/L至1.5mol/L。
隔离膜
在一些实施例中，正极与负极之间设有隔离膜以防止短路。可用于本申请的实施例中使用的隔离膜的材料和形状没有特别限制，其可为任何现有技术中公开的技术。在一些实施例中，隔离膜包括由对本申请的电解液稳定的材料形成的聚合物或无机物等。
例如，隔离膜可包括基材层和表面处理层。基材层为具有多孔结构的无纺布、膜或复合膜，基材层的材料包括聚乙烯、聚丙烯、聚对苯二甲酸乙二醇酯或聚酰亚胺中的至少一种。具体地，可选用聚丙烯多孔膜、聚乙烯多孔膜、聚丙烯无纺布、聚乙烯无纺布或聚丙烯-聚乙烯-聚丙烯多孔复合膜。
基材层的至少一个表面上设置有表面处理层，表面处理层可以是聚合物 层或无机物层，也可以是混合聚合物与无机物所形成的层。
无机物层包括无机颗粒和粘结剂，无机颗粒包括氧化铝、氧化硅、氧化镁、氧化钛、二氧化铪、氧化锡、二氧化铈、氧化镍、氧化锌、氧化钙、氧化锆、氧化钇、碳化硅、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。粘结剂包括聚偏氟乙烯、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、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。
聚合物层中包含聚合物，聚合物的材料包括聚酰胺、聚丙烯腈、丙烯酸酯聚合物、聚丙烯酸、聚丙烯酸盐、聚乙烯呲咯烷酮、聚乙烯醚、聚偏氟乙烯或聚(偏氟乙烯-六氟丙烯)中的至少一种。
在一些实施例中，本申请的电化学装置包括，但不限于：所有种类的一次电池、二次电池、燃料电池、太阳能电池或电容。
在一些实施例中，所述电化学装置是锂二次电池。
在一些实施例中，锂二次电池包括，但不限于：锂金属二次电池、锂离子二次电池、锂聚合物二次电池或锂离子聚合物二次电池。
五、电子装置
本申请的电子装置可为任何使用根据本申请第四方面所述的电化学装置的装置。
在一些实施例中，所述电子装置包括，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、家庭用大型蓄电池或锂离子电容器等。
实施例1至实施例13以及对比例1至对比例2的负极活性材料制备过程如下：
1.将100g的SiO X(x为0.5至1.5)，石墨粉末(天然石墨的质量见表1)分散于水中，搅拌10min后，加入200g(碳纳米管质量见表1，羧甲基纤维素质量分数为0.6％，其他为溶剂水)的碳纳米管浆料，搅拌4h。
2.除去溶剂后得到干燥粉末；
3.将步骤2的干燥粉末在氮气气氛下进行烧结，氮气流量为：0.5至1.5L/min，炉体保持常压，烧结温度为600℃，烧结时间为2小时。
表1--材料制备具体实施例和对比例
Figure PCTCN2021104552-appb-000001
Figure PCTCN2021104552-appb-000002
注：表1中，对比例3中简单机械混合指不进行造粒，在制作混浆过程直接加入硅氧化物和石墨以及碳纳米管。
表1中的实施例1至实施例13和对比例1和对比例2中，因为干燥粉末在氮气气氛下进行烧结工艺的控制，无定形碳的厚度均为20nm至50nm。无定形碳的主要作用是配合碳纳米管增加基体硅氧化物的导电性，同时增强造粒后的硅氧化物和石墨接触，提高界面接触。无定形碳的厚度需控制在500nm以下，太厚的无定形碳无法保证离子的传导以及碳纳米管的长程导电性。
测试方法：
1、比表面积测试：在恒温低温下，测定不同相对压力时的气体在固体表面的吸附量后，基于布朗诺尔-埃特-泰勒吸附理论及其公式(BET公式)求得试样单分子层吸附量，从而计算出固体的比表面积。每个N 2分子的所占据的平均面积16.2A 2，称取1.5至3.5g粉末样品装入TriStar II 3020的测试测试样品管中，200℃脱气120min后进行测试。
2、负极活性材料粒径测试：50ml洁净烧杯中加入约0.02g粉末样品，加入约20ml去离子水，再滴加几滴1％的表面活性剂，使粉末完全分散于水中，120W超声清洗机中超声5分钟，利用MasterSizer 2000测试粒度，即负极活性材料的Dv50，Dv50表示材料在体积基准的颗粒分布中，从小粒径侧起、 达到体积累积50％的粒径。
3、极片粒度测试(平均粒径)：将极片进行截面SEM拍摄，选择500X的倍数，选择背散模式，随机挑取100个石墨或者硅颗粒测量颗粒中最大直径(颗粒的边界上间隔最远的距离)的平均值，即平均粒径，得到石墨的平均粒径和硅氧化物的平均粒径。
全电池评估
电芯的制备
将活性物质LiCoO 2、导电炭黑、粘结剂聚偏二氟乙烯(PVDF)按重量比96.7：1.7：1.6在N-甲基吡咯烷酮溶剂体系中充分搅拌混合均匀后，涂覆于Al箔上烘干、冷压，得到正极。
将实施例中的硅材料按照一定的比例混合设计克容量为500mAh/g的混合粉末，将混合负极、导电剂乙炔黑、聚丙烯酸(PAA)按照重量比95：1.2：3.8在去离子水溶剂体系中充分搅拌混合均匀后，涂覆于Cu箔上烘干、冷压，得到负极。以PE多孔聚合薄膜作为隔离膜。将正极、隔离膜、负极按顺序叠好，使隔离膜处于阴负极中间起到隔离的作用，并卷绕得到裸电芯。将裸电芯置于外包装中，注入配好的电解液并封装，经过化成，脱气，切边等工艺流程得到全电芯。
其中，电芯制备中的电解液的制备方法为：在含水量小于10ppm的环境下，将六氟磷酸锂、氟代碳酸乙烯酯(FEC)与非水有机溶剂(碳酸乙烯酯(EC)：碳酸二甲酯(DMC)：碳酸二乙酯(DEC)＝1：1：1，重量比)配制成氟代碳酸乙烯酯的重量浓度为10wt％，表2中所有实施例的电芯用的锂盐为六氟磷酸锂，浓度为1mol/L。
循环测试：
测试温度为25℃或45℃，以0.7C恒流充电到4.45V，恒压充电到0.025C，静置5分钟后以0.5C放电到3.0V。以此步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，然后进行循环充放电，并记录每一圈循环的放电容量值，使用下述公式计算循环容量保持率：循环第N圈容量保持率＝(第N次循环的放电容量/首次循环的放电容量)×100％。25℃时，当容量保持率为90％时，记录该保持率下的圈数，即25℃循环截至到90％的圈数；45℃时，当容量保持率为80％时，记录该保持率下的圈数，即45℃循环截至到80％的圈数。
电芯满充膨胀率测试：
用螺旋千分尺测试未进行充放电时初始电芯的厚度D0，循环至400圈时，电芯处于满充状态下，再用螺旋千分尺测试此时电芯的厚度D1，根据下述公式计算电池厚度膨胀率ε，ε＝(D1-D0)/D0×100％。从而获得25℃或45℃循环至400圈的电芯膨胀率。
表2
Figure PCTCN2021104552-appb-000003
Figure PCTCN2021104552-appb-000004
实施例1至4和对比例3对比说明：因为硅颗粒的粒径比石墨小，随着复合颗粒硅含量的增加，复合颗粒的粒径随着有所下降，BET也有所增加。和对比例3对比，虽然硅含量提升，循环依然能够得到改善。因此，选择硅碳复合物满足以下关系式：2≤b/a<6，其中a表示硅氧化物的平均粒径，b表示石墨的平均粒径，合适粒径范围的硅氧和石墨循环得到了改善，25℃循环循环至400圈的电芯膨胀率和45℃循环循环至400圈的电芯膨胀率也得到了改善。
实施例5至实施例7和对比例3对比说明：随着碳纳米管含量的增加，复合颗粒的粒径随之有所增大，比表面积也有所增大。和对比例3对比，循环依然能够得到显著改善。
实施例8至实施例9和对比例1至3对比说明：硅和石墨粒径需要满足关系式2≤b/a<6，才能达到合适的造粒粒径和更好的循环改善。
实施例10至实施例11和对比例3对比说明：复合造粒的复合颗粒的粒径需要满足关系式a+b≤c≤5b，才能达到合适的造粒粒径和更好的循环改善。
实施例12至实施例13和对比例3对比说明：负极活性材料的Dv50(中 位粒径)需满足6.1μm至60μm，才能得到合适的负极活性材料和更好的循环性能。
在实施例7的基础上，保持其他条件不变，仅进一步的改变锂盐，具体的锂盐浓度见表3。
表3
Figure PCTCN2021104552-appb-000005
注：LiFSI摩尔质量为187.07g/mol，LiPF 6摩尔质量为151.91g/mol。
实施例14至16与实施例7相比，不同的仅仅是加入了锂盐双(氟磺酰基)酰亚胺锂(LiFSI)，通过调控与LiFSI与LiPF 6的质量比，改善了电芯循环性能和膨胀性能，这主要是因为，负极材料中的硅碳复合物和电解液中锂盐相互作用，改善负极和电解液之间的接触，从而改善其循环性能。
虽然已经说明和描述了本发明的一些示例性实施方式，然而本发明不限于所公开的实施方式。相反，本领域普通技术人员将认识到，在不脱离如所附权利要求中描述的本发明的精神和范围的情况下，可对所描述的实施方式进行一些修饰和改变。

Claims (14)

  1. 一种负极活性材料，包括硅碳复合物，其中，所述硅碳复合物包括硅氧化物和石墨，所述硅氧化物的通式为SiO X，0.5≤x≤1.6，所述硅碳复合物满足以下关系式：2≤b/a<6，其中a表示硅氧化物的平均粒径，b表示石墨的平均粒径。
  2. 根据权利要求1所述的负极活性材料，其中，a为2μm至6μm。
  3. 根据权利要求1所述的负极活性材料，其中，b为4.1μm至30μm。
  4. 根据权利要求1所述的负极活性材料，其中，c表示负极活性材料的Dv50，c为6.1μm至60μm。
  5. 根据权利要求4所述的负极活性材料，其中，所述负极活性材料满足以下关系式：a+b≤c≤5b。
  6. 根据权利要求1所述的负极活性材料，其中，所述负极活性材料还包括位于所述硅碳复合物表面的保护层，所述保护层包括碳纳米管、无定形碳或石墨烯中的至少一种。
  7. 根据权利要求6所述的负极活性材料，其中，满足如下条件(i)至(iii)中至少一者；
    (i)所述保护层包括第一保护物和第二保护物，第一保护物包括碳纳米管、无定形碳或石墨烯中的至少一种，第二保护物包括碳纳米管、无定形碳或石墨烯中的至少一种；
    (ii)所述碳纳米管的管长为d，1μm≤d≤15μm；
    (iii)基于负极活性材料，所述保护层的质量分数为0.05％至5％。
  8. 根据权利要求6所述的负极活性材料，其中，所述保护层包括第一保护物和第二保护物，所述第一保护物的厚度为20nm至300nm，所述第二保护物的厚度为20nm至500nm。
  9. 根据权利要求1所述的负极活性材料，其中，满足如下条件(a)至(b) 中至少一者：
    (a)所述负极活性材料的比表面积为1m 2/g至50m 2/g；
    (b)基于负极活性材料，所述硅氧化物的质量分数为5％至50％，所述石墨的质量分数为25％至93.5％。
  10. 一种电化学装置，其包括负极、电解液、隔离膜和正极，所述负极包含如权利要求1所述的负极活性材料。
  11. 根据权利要求10所述的电化学装置，其中，所述电解液还包括锂盐，所述锂盐包括双(氟磺酰基)酰亚胺锂和六氟磷酸锂。
  12. 根据权利要求11所述的电化学装置，其中，所述锂盐的浓度为1mol/L至2mol/L。
  13. 根据权利要求11所述的电化学装置，其中，所述双(氟磺酰基)酰亚胺锂和六氟磷酸锂的质量比为0.06至5。
  14. 一种电子装置，其包含如权利要求10至13任一所述的电化学装置。
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US20230343933A1 (en) 2023-10-26
JP2023512136A (ja) 2023-03-24
CN112820869A (zh) 2021-05-18

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