WO2021195913A1 - 负极材料、负极极片、电化学装置和电子装置 - Google Patents

负极材料、负极极片、电化学装置和电子装置 Download PDF

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WO2021195913A1
WO2021195913A1 PCT/CN2020/082266 CN2020082266W WO2021195913A1 WO 2021195913 A1 WO2021195913 A1 WO 2021195913A1 CN 2020082266 W CN2020082266 W CN 2020082266W WO 2021195913 A1 WO2021195913 A1 WO 2021195913A1
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group
negative electrode
silicon
electrode material
polymer
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PCT/CN2020/082266
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English (en)
French (fr)
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王超
章婷
姜道义
崔航
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宁德新能源科技有限公司
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Priority to PCT/CN2020/082266 priority Critical patent/WO2021195913A1/zh
Priority to EP20928837.2A priority patent/EP4131499A4/en
Priority to CN202080030144.5A priority patent/CN113728471B/zh
Publication of WO2021195913A1 publication Critical patent/WO2021195913A1/zh
Priority to US17/957,179 priority patent/US20230042519A1/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
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • 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
    • 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
    • H01M4/139—Processes of manufacture
    • H01M4/1395—Processes of manufacture of 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
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • 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
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/46—Separators, membranes or diaphragms characterised by their combination with electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • 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
    • H01M2004/028—Positive 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

  • This application relates to the field of electronic technology, and in particular to a negative electrode material, a negative electrode piece, an electrochemical device and an electronic device.
  • carbon nanotubes can be used to coat the silicon-based materials.
  • the current carbon nanotube coating solutions are not satisfactory.
  • the second group includes at least one of a carboxyl group, a hydroxyl group, a phenolic hydroxyl group, an aldehyde group, an amide group, an acid halide group, an ester group, a carbonyl group, or a halogenated hydrocarbon group.
  • Fig. 1 is a schematic diagram of the negative electrode material of the present application.
  • Fig. 3 is a schematic diagram of the electrode assembly of the electrochemical device of the present application.
  • FIG. 5 is an X-ray diffraction pattern of silicon-based material particles in Example 1.
  • FIG. 6 is a cycle curve of Example 1 and Comparative Example 1.
  • porous silicon-based materials can be used to reduce the size of silicon-based materials, coated with polymers, coated with oxides, and coated with carbon.
  • Material coating, etc., in which polymer coating is used the conductivity is poor and the impedance is large.
  • Carbon material coating is an important means. Carbon nanotubes have good mechanical properties (tensile strength can reach 200Gpa, which is 100 times that of steel; modulus of elasticity can reach 1TPa, which is about 5 times that of steel), and excellent electrical conductivity (conductivity is usually up to 10,000 times that of copper) Therefore, it can be used as an excellent coating material for silicon-based materials.
  • carboxymethyl cellulose is used to disperse carbon nanotubes on the surface of silicon-based materials.
  • carboxymethyl cellulose and carbon nanotubes do not have a direct chemical bond, so the binding force between them is weak.
  • This application simultaneously introduces carbon nanotubes and a polymer with double groups on the surface of silicon-based material particles, and the two groups of the polymer are chemically bonded to the silicon-based material and the carbon nanotubes, respectively, to improve the silicon-based material and the carbon nanotubes.
  • the bonding force of the silicon-based anode material can be significantly improved, and the uniform carbon nanotube coating layer can be formed, thereby improving the cycle performance and rate performance of the electrochemical device.
  • the negative electrode material includes a composite formed of a silicon-based material 1, a polymer 2 and a carbon nanotube 3.
  • the polymer 2 has a first group and a second group, the first group is chemically bonded to the carbon nanotube 3 and the second group is chemically bonded to the silicon-based material 1.
  • the bonding force between the polymer 2 and the carbon nanotube 3 is enhanced, and the bonding force between the silicon-based material and the carbon nanotube 3 is improved.
  • a uniform carbon nanotube coating layer is formed, which improves the conductivity of the silicon-based material, thereby improving the cycle performance and rate performance of the electrochemical device.
  • the silicon-based material includes at least one of silicon nanoparticles, silicon oxide, or silicon-carbon composite particles. In some embodiments, the silicon-based material includes at least one of silicon, silicon oxide, silicon carbon, or silicon alloy. In some embodiments, the silicon-based material may contain elements such as lithium, magnesium, titanium, and aluminum. These doped metal elements can improve the conductivity of the negative electrode material, the first effect of the battery, the cycle performance of the electrochemical device and the DCR (Directive Current Resistance). In some embodiments, the average particle size of the silicon-based particles is 500 nm-30 ⁇ m, and the size of the nano-silicon crystal particles is less than 100 nm.
  • the average particle size of the silicon-based material is too small, the silicon-based material is prone to agglomeration and consumes more electrolyte to form the SEI film due to the large specific surface area. If the average particle size of the silicon-based material is too large, it is not conducive to suppressing the volume expansion of the silicon-based material, and it is also easy to cause the deterioration of the conductivity of the active material layer. In addition, if the average particle size of the silicon-based material is too large, the strength of the negative pole piece will decrease. In some embodiments, the particle size of Si is less than 100 nm.
  • the polymer 2 bridges the silicon-based material 1 and the carbon nanotube 3.
  • carbon nanotubes 3 are present on the surface of the silicon-based material 1.
  • FIG. 4 is a TEM image of a silicon-based material bridged by a polymer and carbon nanotubes, and the carbon nanotubes are shown in a dashed frame.
  • the silicon-based material 1 is silicon-based particles, and the carbon nanotubes 3 are bridged with the silicon-based material 1 through the action of the polymer 2 to coat the surface of the silicon-based material 1.
  • the bonding force between the silicon-based material 1 and the carbon nanotubes 3 is enhanced, and the uniform dispersion of the carbon nanotubes 3 on the surface of the silicon-based material 1 is also improved, and the carbon nanotubes 3 are prevented from being on the surface. Agglomeration of the surface of the silicon-based material 1.
  • the carbon nanotubes may include at least one of alkali metal ions such as Li, Na, or K.
  • the carbon nanotubes include single-walled carbon nanotubes, multi-walled carbon nanotubes, or a combination thereof.
  • the diameter of the carbon nanotube is 1 nm to 30 nm, and the carbon nanotube has an aspect ratio of 50 to 30,000.
  • the first group includes at least one of epoxy, phenolic hydroxyl, anilino, phenyl, naphthyl, anthracenyl, phenanthryl, phenyl ether, pyrrole, pyridine, or furan.
  • the second group includes at least one of a carboxyl group, a hydroxyl group, a phenolic hydroxyl group, an aldehyde group, an amide group, an acid halide group, an ester group, a carbonyl group, or a halogenated hydrocarbon group.
  • the above-mentioned first group can facilitate the chemical bonding between the polymer and the carbon nanotubes
  • the above-mentioned second group can facilitate the chemical bonding between the polymer and the silicon-based material.
  • the mass percentage of the polymer in the composite is 0.5%-10%.
  • the content of the polymer is too small, the bonding between the silicon-based material particles and the carbon nanotubes cannot be effectively enhanced, so that the electronic conductivity of the negative electrode material and the cycle performance and direct current resistance (DCR) of the electrochemical device cannot be effectively improved.
  • the content of the polymer is too much, although the two groups of the polymer can effectively enhance the bond between the silicon-based material particles and the carbon nanotubes, due to the poor conductivity of the polymer itself, too much polymer will As a result, the electronic conductivity of the negative electrode material is reduced, which in turn damages the cycle performance and direct current resistance (DCR) of the electrochemical device.
  • the thickness of the polymer layer is 5 nm to 200 nm.
  • the mass percentage of carbon nanotubes in the composite is 0.5%-10%.
  • the content of carbon nanotubes is too small, the conductivity of silicon-based materials cannot be effectively improved.
  • the content of carbon nanotubes is too large, the coating layer of carbon nanotubes is too thick, which is not conducive to the migration of lithium ions, thereby deteriorating the cycle performance of the electrochemical device.
  • the mass ratio of the silicon-based material, polymer, and carbon nanotubes in the composite is 85-96.5:0.5-10:0.5-10.
  • the highest intensity value of 2 ⁇ attributable to the range of 20.5° to 21.5° is I 1
  • the highest intensity value attributable to the range of 28.0° to 29.0° is I 2 , 0 ⁇ I 2 /I 1 ⁇ 3.
  • the value of I 2 /I 1 reflects the degree to which the silicon-based material is affected by disproportionation.
  • the negative electrode material is further doped with at least one element of lithium, magnesium, titanium, or aluminum.
  • the negative electrode material doping with metal elements has an effect on improving the conductivity of the negative electrode material, the first effect of the battery, the cycle performance of the electrochemical device, and the DCR.
  • the specific surface area of the negative electrode material is 1 m 2 /g to 50 m 2 /g.
  • the above-mentioned negative electrode material can be prepared by the following method: adding 0.5 g to 15 g of carbon nanotube (CNT) powder to a solvent containing 0.5 g to 20 g of polymer, and dispersing for 1 hour to 24 hours to obtain a CNT slurry Material; Add 100g of silicon-based material powder to the above-mentioned CNT slurry, stir and disperse for 2h-4h at a rotation speed of 300r/min ⁇ 2500r/min, to obtain a mixed slurry; dry, remove the above-mentioned mixed slurry The solvent is used to obtain the composite; the composite is mechanically crushed and processed through a 400-mesh sieve to obtain the negative electrode material, that is, the silicon-based material coated with CNT and polymer.
  • CNT carbon nanotube
  • the solvent in the above preparation process can be at least one of water, ethanol, methanol, n-hexane, N,N-dimethylformamide, pyrrolidone, acetone, toluene, isopropanol, or n-propanol.
  • drying can be done by rotary evaporation, spray drying, filtration or freeze drying.
  • the negative pole piece includes a current collector 4 and an active material layer 5.
  • the active material layer 5 is located on the current collector 4. It should be understood that although the active material layer 5 is shown as being located on one side of the current collector 4 in FIG. 2, this is only exemplary, and the active material layer 5 may be located on both sides of the current collector 4.
  • the current collector of the negative pole piece may include at least one of copper foil, aluminum foil, nickel foil, or carbon-based current collector.
  • the active material layer 5 includes the above-mentioned negative electrode material.
  • the active material layer further includes a carbon material, a conductive agent, and a binder.
  • the carbon material includes graphite, graphene, or the like.
  • the binder may include carboxymethyl cellulose (CMC), polyacrylic acid, polyvinylpyrrolidone, polyaniline, polyimide, polyamideimide, polysiloxane, polystyrene-butadiene At least one of rubber, epoxy resin, polyester resin, polyurethane resin, or polyfluorene.
  • the mass percentage of the binder in the active material layer is 0.5%-10%.
  • the conductive agent includes at least one of single-walled carbon nanotubes, multi-walled carbon nanotubes, vapor-grown carbon fibers, conductive carbon black, acetylene black, Ketjen black, conductive graphite, or graphene.
  • the mass percentage of the conductive agent in the active material layer is 0.1% to 5%.
  • the electrochemical device includes a positive pole piece 10, a negative pole piece 12, and a separator disposed between the positive pole piece 10 and the negative pole piece 12.
  • the positive pole piece 10 may include a positive current collector and a positive active material layer coated on the positive current collector. In some embodiments, the positive active material layer may only be coated on a partial area of the positive current collector.
  • the positive active material layer may include a positive active material, a conductive agent, and a binder. Al foil can be used as the positive electrode current collector, and similarly, other positive electrode current collectors commonly used in this field can also be used.
  • the conductive agent of the positive pole piece may include at least one of conductive carbon black, sheet graphite, graphene, or carbon nanotubes.
  • the binder in the positive pole piece may include polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, styrene-acrylate copolymer, styrene-butadiene copolymer, polyamide, polyacrylonitrile, Polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinyl acetate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene or polyhexafluoropropylene At least one of them.
  • the positive active material includes, but is not limited to, at least one of lithium cobaltate, lithium nickelate, lithium manganate, lithium nickel manganate, lithium nickel cobaltate, lithium iron phosphate, lithium nickel cobalt aluminate or lithium nickel cobalt manganate,
  • the above positive active material can be doped or coated.
  • the isolation film 11 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.
  • polyethylene and polypropylene they have a good effect on preventing short circuits, and can improve the stability of the battery through the shutdown effect.
  • the surface of the isolation membrane may further include a porous layer, the porous layer is disposed 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 dioxide (HfO 2 ), tin oxide (SnO 2 ), ceria (CeO 2 ), nickel oxide (NiO), oxide Zinc (ZnO), calcium oxide (CaO), zirconium oxide (ZrO 2 ), yttrium oxide (Y 2 O 3 ), silicon carbide (SiC), boehmite, aluminum hydroxide, magnesium hydroxide or calcium hydroxide and sulfuric acid At least one of barium.
  • alumina Al 2 O 3
  • Silicon oxide SiO 2
  • magnesium oxide MgO
  • titanium oxide TiO 2
  • hafnium dioxide HfO 2
  • the binder is selected from polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyethylene pyrrole At least one of alkanone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, or polyhexafluoropropylene.
  • the porous layer on the surface of the isolation membrane can improve the heat resistance, oxidation resistance and electrolyte infiltration performance of the isolation membrane, and enhance the adhesion between the isolation membrane and the pole piece.
  • the negative pole piece 12 may be the negative pole piece as described above.
  • the electrode assembly of the electrochemical device is a wound electrode assembly or a stacked electrode assembly.
  • the electrochemical device includes a lithium ion battery, but the application is not limited thereto.
  • the electrochemical device may also include an electrolyte.
  • the electrolyte includes dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), ethylene carbonate (EC), propylene carbonate (PC), propylene propionate At least two of esters (PP).
  • the electrolyte may additionally include at least one of vinylene carbonate (VC), fluoroethylene carbonate (FEC), or dinitrile compound as an additive to the electrolyte.
  • the positive pole piece, separator film, and negative pole piece are sequentially wound or stacked into electrode parts, and then packaged in, for example, aluminum-plastic film, and injected into electrolysis.
  • Lithium-ion battery is made by liquid, formed and packaged. Then, perform performance test and cycle test on the prepared lithium-ion battery.
  • the embodiments of the present application also provide an electronic device including the above-mentioned electrode assembly or an electronic device including the above-mentioned electrochemical device.
  • the electronic device of the present application is not particularly limited, and it can be used in any electronic device known in the prior art.
  • electronic devices may include, but are not limited to, notebook computers, pen-input computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, headsets, Video recorders, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, assisted bicycles, bicycles, Lighting equipment, toys, game consoles, clocks, power tools, flashlights, cameras, large household storage batteries and lithium-ion capacitors, etc.
  • the current collector adopts copper foil with a thickness of 10 ⁇ m
  • the active material adopts the above-mentioned silicon-based material and graphite, in which the silicon-based material accounts for 10% of the mass of the active material layer
  • the binder adopts polyacrylic acid
  • the materials, conductive carbon black, and binder are mixed according to 95:1.2:3.8 and then dispersed in water to form a slurry, which is stirred, coated on copper foil, dried, cold pressed, and slit to obtain a negative pole piece.
  • Preparation of positive pole piece After taking positive active material LiCoO 2 , conductive carbon black, and binder polyvinylidene fluoride (PVDF) at a weight ratio of 96.7:1.7:1.6 in an N-methylpyrrolidone solvent system, stir and mix well. Coating on the aluminum foil, and then drying and cold pressing to obtain a positive pole piece.
  • positive active material LiCoO 2 LiCoO 2 , conductive carbon black, and binder polyvinylidene fluoride (PVDF) at a weight ratio of 96.7:1.7:1.6 in an N-methylpyrrolidone solvent system
  • Battery preparation Polyethylene porous polymer film is used as the separator, and the positive pole piece, separator film, and negative pole piece are stacked in sequence, so that the separator is in the middle of the positive and negative pole pieces for isolation, and rolled Wind the electrode assembly.
  • the electrode assembly is placed in the outer packaging aluminum plastic film, the electrolyte containing ethylene carbonate (EC) and propylene carbonate (PC) is injected and packaged, and the lithium ion battery is obtained through the process flow of chemical formation, degassing, and trimming.
  • EC ethylene carbonate
  • PC propylene carbonate
  • Example 2-22 and Comparative Examples 1 to 3 the preparation of the positive pole piece and lithium ion battery are the same as in Example 1, except that the preparation of the negative electrode material in the negative pole piece is different. Only the preparation of the negative electrode material will be described below. s difference.
  • the types of polymers were changed to epoxy resin (containing hydroxyl and epoxy groups), lithium carboxymethyl cellulose (containing only carboxyl groups), polyethylene glycol (only Containing hydroxyl group), polyaniline (containing only aniline group), polysiloxane (containing only epoxy group), polyethylene (without group A and group B).
  • Example 7-10 and Comparative Example 2 the content of polymer was changed to 1g, 5g, 10g, 20g, 0g, and the content of silicon-based material particles was changed to 94g, 90g, 85g, 75g, 95g, respectively. .
  • Example 11-14 and Comparative Example 3 the content of carbon nanotubes was changed to 1g, 3g, 10g, 20g, 0g, and the content of silicon-based material particles was changed to 96g, 94g, 87g, 77g, 97g.
  • Example 15-18 the I 2 /I 1 values of the silicon-based material particles were changed to 0.41, 0.64, 1, and 2.5, respectively, and the rest remained unchanged.
  • the negative electrode material, conductive carbon black, and binder polyacrylic acid (PAA) are mixed with deionized water at a mass ratio of 80:10:10 to form a slurry, and a 100 ⁇ m thick coating is coated with a doctor blade. After 12 hours of vacuum at 85°C After drying in the drying box, in a dry environment, a punch is used to cut into discs with a diameter of 1 cm. In the glove box, a metal lithium sheet is used as a counter electrode, a ceglard composite film is selected as the isolation film, and an electrolyte is added to assemble the button cell. Use LAND series battery test test to charge and discharge the battery to test its charge and discharge performance.
  • PAA binder polyacrylic acid
  • the fixed body resistance is determined by measuring the voltage at both ends of the resistance to be measured and the current flowing through it, and the conductivity is calculated by combining the height and bottom area of the resistance to be measured.
  • the test mold shake it gently, then place the gasket on the mold on the sample; after the sample is loaded, place the mold on the worktable of the electronic pressure testing machine at a rate of 5mm/min Raise to 500kg (159Mpa), constant pressure for 60s, and then relieve the pressure to 0; when the constant pressure of the sample reaches 5000 ⁇ 2kg (about 15-25s after the pressure rises to 5000kg), record the sample pressure, read the deformation height of the sample, and record this When the resistance tester displays the value, the formula can be used to calculate the electronic conductivity.
  • the test temperature is 45°C, and it is charged to 4.4V at a constant current of 0.7C, then charged to 0.025C at a constant voltage, and discharged to 3.0V at 0.5C after standing for 5 minutes.
  • the capacity obtained in this step is the initial capacity, and the 0.7C charge/0.5C discharge is carried out for a cycle test.
  • the capacity at each step is used as the ratio of the initial capacity to obtain the capacity attenuation curve, and the number of cycles at which the capacity attenuates to 80% of the initial capacity is counted. .
  • Table 1 shows the parameter settings of Examples 1 to 6 and Comparative Example 1
  • Table 2 shows the electronic conductivity of the corresponding negative electrode material, the first effect of the battery, and the cycle performance and DCR of the electrochemical device.
  • Fig. 6 shows the cycle curves of Example 1 and Comparative Example 1. For the same number of cycles, the capacity retention rate of Example 1 is larger.
  • Table 3 shows the parameter settings of Examples 1, 7-10 and Comparative Example 2, and Table 4 shows the electronic conductivity of the corresponding negative electrode materials, the first effect of the battery, and the cycle performance and DCR of the electrochemical device.
  • Table 5 shows the parameter settings of Examples 1, 11-14 and Comparative Example 3.
  • Table 6 shows the electronic conductivity of the corresponding negative electrode materials, the first effect of the battery, and the cycle performance and DCR of the electrochemical device.
  • Table 7 shows the parameter settings of Examples 1 and 15-18, and Table 8 shows the electronic conductivity of the corresponding negative electrode material, the first effect of the battery, and the cycle performance and DCR of the electrochemical device.
  • FIG. 5 shows an X-ray diffraction pattern of silicon-based material particles in Example 1.
  • Table 9 shows the parameter settings of Examples 1 and 19-22
  • Table 10 shows the electronic conductivity of the corresponding negative electrode material, the first effect of the battery, and the cycle performance and DCR of the electrochemical device.

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Abstract

一种负极材料、负极极片（12）、电化学装置和电子装置。负极材料包括由硅基材料（1）、聚合物（2）和碳纳米管（3）形成的复合物，其中，聚合物（2）具有第一基团和第二基团，第一基团化学键合至碳纳米管（3），第二基团化学键合至硅基材料（1）。在硅基材料（1）颗粒表面同时引入碳纳米管（3）和具有双基团的聚合物（2），通过聚合物（2）的两种基团分别与硅基材料（1）和碳纳米管（3）化学键合，提升了硅基材料（1）与碳纳米管（3）的结合力，并且形成均匀的碳纳米管（3）包覆层，从而可以显著改善硅基材料（1）的导电性，进而改善电化学装置的循环性能和倍率性能。

Description

负极材料、负极极片、电化学装置和电子装置 技术领域
本申请涉及电子技术领域，尤其涉及一种负极材料、负极极片、电化学装置和电子装置。
背景技术
硅基材料具有高达4200mAh/g的理论比容量，是具有应用前景的下一代电化学装置(例如，锂离子电池)的负极材料。然而，硅基材料在充放电过程中具有约300％的体积膨胀，并且在其表面形成不稳定的固体电解质界面膜(SEI，solid electrolyte interface)，这些影响了电化学装置的性能的发挥。
为了改善硅基材料的体积膨胀和导电性，可以采用碳纳米管来包覆硅基材料，然而，目前的碳纳米管包覆方案并不令人满意。
发明内容
鉴于以上所述现有技术的缺点，本申请采用具有两种基团的聚合物来改善硅基材料和碳纳米管之间的结合。
本申请提供一种负极材料，包括：由硅基材料、聚合物和碳纳米管形成的复合物，其中，所述聚合物具有第一基团和第二基团，所述第一基团化学键合至所述碳纳米管，所述第二基团化学键合至所述硅基材料。
在上述负极材料中，其中，所述硅基材料的表面存在所述碳纳米管。
在上述负极材料中，其中，所述第一基团包括环氧基、酚羟基、苯胺基、苯基、萘基、蒽基、菲基、苯醚基、吡咯、吡啶或呋喃中的至少一种。
在上述负极材料中，其中，所述第二基团包括羧基、羟基、酚羟基、醛基、酰胺基、酰卤基、酯基、羰基或卤代烃基中的至少一种。
在上述负极材料中，其中，所述复合物中的所述聚合物的质量百分比为0.5％～10％。
在上述负极材料中，其中，所述复合物中的所述碳纳米管的质量百分比为0.5％～10％。
在上述负极材料中，其中，所述复合物中的所述硅基材料、所述聚合物和所述碳纳米管的质量比为85～96.5：0.5～10：0.5～10。
在上述负极材料中，其中，所述硅基材料在X射线衍射图案中2θ归属于20.5°～21.5°范围内的最高强度数值为I 1，归属于28.0°～29.0°范围内的最高强度数值为I 2，0<I 2/I 1≤3。
在上述负极材料中，其中，所述负极材料还掺杂有锂、镁、钛或铝中的至少一种元素。
本申请还提供了一种负极极片，包括：集流体；活性物质层，位于所述集流体上；其中，所述活性物质层包括上述任一负极材料。
本申请还提供了一种电化学装置，包括：正极极片；负极极片；隔离膜，设置于所述正极极片和所述负极极片之间；其中，所述负极极片为上述负极极片。
本申请还提供了一种电子装置，包括上述电化学装置。
本申请在硅基材料颗粒表面同时引入碳纳米管和具有双基团的聚合物，通过聚合物的两种基团分别与硅基材料和碳纳米管化学键合，提升硅基材料与碳纳米管的结合力，并且形成均匀的碳纳米管包覆层，从而可以显著改善硅基材料的导电性，进而改善电化学装置的循环性能和倍率性能。
附图说明
图1是本申请的负极材料的示意图。
图2是本申请的负极极片的示意图。
图3是本申请的电化学装置的电极组件的示意图。
图4是碳纳米管和聚合物包覆的硅基材料的透射电子显微镜(TEM)图像。
图5是实施例1中的硅基材料颗粒的X射线衍射图。
图6是实施例1和对比例1的循环曲线。
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。
目前，为了提升采用硅基材料作为负极材料的电化学装置的循环稳定性和倍率性能，可以采用多孔硅基材料，降低硅基材料尺寸，采用聚合物包覆，采用氧化物包覆，采用碳材料包覆等，其中采用聚合物包覆，导电性较差，阻抗较大。碳材料包覆是重要手段。碳纳米管力学性能好(抗拉强度可达200Gpa，是钢的100倍；弹性模量可达1TPa，约为钢的5倍)，导电性能优(电导率通常可达铜的1万倍)，因此可以作为硅基材料的优异包覆材料。碳纳米管包覆在改善硅基材料的体积膨胀的同时，还可以显著提升硅基材料的导电性，是近年来广泛应用的一种技术。然而，高导电的碳纳米管与硅基材料的表面结合力较弱，因为它们之间没有直接的键合作用，并且碳纳米管难以分散，因为碳纳米管会聚结而使得分散性差，因此在硅基材料表面形成均匀的碳纳米管包覆层的难度较大。因此，在硅基材料中加入碳纳米管，可以形成导电网络结构，但是并未形成均匀有效的包覆。
在目前的一些方案中，使用羧甲基纤维素使碳纳米管分散在硅基材料表面。然而，羧甲基纤维素与碳纳米管并无直接的化学键合作用，因此它们之间的结合力较弱。
本申请在硅基材料颗粒表面同时引入碳纳米管和具有双基团的聚合物，通过聚合物的两种基团分别与硅基材料和碳纳米管化学键合，提升硅基材料与碳纳米管的结合力，并且形成均匀的碳纳米管包覆层，从而可以显著改善硅基负极材料的导电性，进而改善电化学装置的循环性能和倍率性能。
如图1所示，本申请的一些实施例提供了一种负极材料，负极材料包括由硅基材料1、聚合物2和碳纳米管3形成的复合物。在一些实施例中，聚合物2具有第一基团和第二基团，第一基团化学键合至碳纳米管3，第二基团化学键合至硅基材料1。通过第一基团与碳纳米管3之间的化学键合作用，增强了聚合物2与碳纳米管3之间的结合力，进而提升了硅基材料与碳纳米 管3之间的结合力，并且形成均匀的碳纳米管包覆层，改善了硅基材料的导电性，进而改善电化学装置的循环性能和倍率性能。
在一些实施例中，硅基材料包括硅纳米颗粒、氧化亚硅或硅碳复合颗粒中的至少一种。在一些实施例中，硅基材料包括硅、硅氧、硅碳或硅合金中的至少一种。在一些实施例中，硅基材料可以含有锂、镁、钛、铝等元素。这些掺杂金属元素对负极材料的导电性能、电池首效、电化学装置的循环性能和DCR(Directive Current Resistance，直流电阻)均有改善作用。在一些实施例中，硅基颗粒的平均粒径为500nm～30μm，其中纳米硅晶粒的尺寸小于100nm。如果硅基材料的平均粒径过小，硅基材料容易发生团聚，并且由于比表面积大而消耗更多的电解液来形成SEI膜。如果硅基材料的平均粒径过大，不利于抑制硅基材料的体积膨胀，也容易引起活性物质层的导电性能的恶化。另外，如果硅基材料的平均粒径太大，则会使得负极极片的强度降低。在一些实施例中，Si的颗粒尺寸小于100nm。
在一些实施例中，聚合物2桥连硅基材料1和碳纳米管3。在一些实施例中，硅基材料1的表面存在碳纳米管3。如图4所示，图4是通过聚合物与碳纳米管桥连的硅基材料的TEM图像，虚线框内示出了碳纳米管。在一些实施例中，硅基材料1为硅基颗粒，碳纳米管3通过聚合物2的作用与硅基材料1桥连，包覆于硅基材料1的表面。通过聚合物2的作用，增强了硅基材料1与碳纳米管3之间的结合力，也改善了碳纳米管3在硅基材料1的表面的均匀分散性，避免了碳纳米管3在硅基材料1的表面的团聚。在一些实施例中，碳纳米管可以包含Li、Na或K等碱金属离子中的至少一种。在一些实施例中，碳纳米管包括单壁碳纳米管、多壁碳纳米管或其组合。在一些实施例中，碳纳米管的直径为1nm～30nm，且碳纳米管具有50～30000的长径比。
在一些实施例中，第一基团包括环氧基、酚羟基、苯胺基、苯基、萘基、蒽基、菲基、苯醚基、吡咯、吡啶或呋喃中的至少一种。在一些实施例中，第二基团包括羧基、羟基、酚羟基、醛基、酰胺基、酰卤基、酯基、羰基或卤代烃基中的至少一种。上述的第一基团可以便利聚合物与碳纳米管之间的化学键合，上述的第二基团可以便利聚合物与硅基材料之间的化学键合。
在一些实施例中，复合物中的聚合物的质量百分比为0.5％～10％。当聚合物的含量过少时，无法有效地增强硅基材料颗粒与碳纳米管之间的结合，使得无法有效改善负极材料的电子电导率以及电化学装置的循环性能、直流电阻(DCR)。当聚合物的含量过多时，虽然可以通过聚合物的两种基团有效地增强硅基材料颗粒与碳纳米管之间的结合，但是由于聚合物本身导电性较差，过多的聚合物会导致负极材料的电子电导率降低，进而损害电化学装置的循环性能和直流电阻(DCR)。在一些实施例中，聚合物层的厚度为5nm～200nm。
在一些实施例中，复合物中的碳纳米管的质量百分比为0.5％～10％。当碳纳米管的含量过少时，不能有效地提升硅基材料的导电性。当碳纳米管的含量过多时，碳纳米管的包覆层过厚，不利于锂离子的迁移，从而恶化了电化学装置的循环性能。
在一些实施例中，复合物中的硅基材料、聚合物和碳纳米管的质量比为85～96.5：0.5～10：0.5～10。通过采用合适的材料配比，在发挥硅基材料比容量高的优点的同时，能够有效地克服硅基材料的导电性差和体积膨胀大的问题，进而改善形成的电化学装置的循环性能和倍率性能。
在一些实施例中，硅基材料在X射线衍射图案中2θ归属于20.5°～21.5°范围内的最高强度数值为I 1，归属于28.0°～29.0°范围内的最高强度数值为I 2，0<I 2/I 1≤3。I 2/I 1的值反映了硅基材料受到歧化的影响程度，I 2/I 1的值越大，硅基材料内部产生的SiO歧化产生的纳米硅基晶粒的尺寸越大，在嵌锂过程中会导致局部区域的应力急剧增大，从而导致硅基材料在循环过程中发生结构破坏。
在一些实施例中，负极材料还掺杂有锂、镁、钛或铝中的至少一种元素。在一些实施例中，负极材料掺杂金属元素对负极材料的导电性能、电池首效、电化学装置的循环性能和DCR均有改善作用。在一些实施例中，负极材料的比表面积为1m 2/g～50m 2/g。
在一些实施例中，可以通过以下方法制备上述负极材料：将0.5g～15g的碳纳米管(CNT)粉末加入到含有0.5g～20g聚合物的溶剂中，进行分散1h～24h，得到CNT浆料；将100g硅基材料粉末加入上述的CNT浆料中，在 转速为300r/min～2500r/min的情况下搅拌分散2h～4h，得到混合浆料；干燥，去除上述的混合浆料中的溶剂，得到复合物；将复合物进行机械破碎、400目过筛处理后得到负极材料，即CNT和聚合物包覆的硅基材料。上述制备过程中的溶剂可以是水、乙醇、甲醇、正己烷、N,N-二甲基甲酰胺、吡咯烷酮、丙酮、甲苯、异丙醇或正丙醇等中的至少一种。另外，干燥可以采用旋转蒸发、喷雾干燥、过滤或冷冻干燥等方式。
如图2所示，本申请的一些实施例提供了一种负极极片，负极极片包括集流体4和活性物质层5。活性物质层5位于集流体4上。应该理解，虽然图2中将活性物质层5示出为位于集流体4的一侧上，但是这仅是示例性的，活性物质层5可以位于集流体4的两侧上。在一些实施例中，负极极片的集流体可以包括铜箔、铝箔、镍箔或碳基集流体中的至少一种。在一些实施例中，活性物质层5包括上述负极材料。
在一些实施例中，活性物质层还包括碳材料、导电剂和粘结剂。在一些实施例中，碳材料包括石墨或石墨烯等。在一些实施例中，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、聚丁苯橡胶、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，活性物质层中的粘结剂的质量百分比为0.5％～10％。在一些实施例中，导电剂包括单壁碳纳米管、多壁碳纳米管、气相生长碳纤维、导电炭黑、乙炔黑、科琴黑、导电石墨或石墨烯中的至少一种。在一些实施例中，活性物质层中的导电剂的质量百分比为0.1％～5％。
如图3所示，本申请的一些实施例提供了一种电化学装置，电化学装置包括正极极片10、负极极片12以及设置于正极极片10和负极极片12之间的隔离膜11。正极极片10可以包括正极集流体和涂覆在正极集流体上的正极活性物质层。在一些实施例中，正极活性物质层可以仅涂覆在正极集流体的部分区域上。正极活性物质层可以包括正极活性物质、导电剂和粘结剂。正极集流体可以采用Al箔，同样，也可以采用本领域常用的其他正极集流体。正极极片的导电剂可以包括导电炭黑、片层石墨、石墨烯或碳纳米管中的至少一种。正极极片中的粘结剂可以包括聚偏氟乙烯、偏氟乙烯-六氟丙烯的共聚物、苯乙烯-丙烯酸酯共聚物、苯乙烯-丁二烯共聚物、 聚酰胺、聚丙烯腈、聚丙烯酸酯、聚丙烯酸、聚丙烯酸盐、羧甲基纤维素纳、聚醋酸乙烯酯、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。正极活性物质包括但不限于钴酸锂、镍酸锂、锰酸锂、镍锰酸锂、镍钴酸锂、磷酸铁锂、镍钴铝酸锂或镍钴锰酸锂中的至少一种，以上正极活性物质可以经过掺杂或包覆处理。
在一些实施例中，隔离膜11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，隔离膜表面还可包括多孔层，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、氢氧化镁或氢氧化钙和硫酸钡中的至少一种。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、羧甲基纤维素纳、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接性。
在一些实施例中，负极极片12可以为如上所述的负极极片。
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或堆叠式电极组件。
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。例如，电化学装置还可以包括电解液。在一些实施例中，电解液包括碳酸二甲酯(DMC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、丙酸丙酯(PP)中的至少两种。此外，电解液还可以额外地包括作为电解液添加剂的碳酸亚乙烯酯(VC)、氟 代碳酸乙烯酯(FEC)或二腈化合物中的至少一种。
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及循环测试。
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极组件的电子装置或包括上述电化学装置的电子装置。在一些实施例中，本申请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。
实施例1
负极材料的制备：将5g碳纳米管粉末加入到含有3g邻氨基苯甲酸钠(具有羧基和苯胺基)的溶剂中，进行分散10h得到碳纳米管浆料；将92g SiO颗粒(I 2/I 1值为0.38)加入上述的碳纳米管浆料中，在转速为2000r/min的情况下搅拌分散4h；干燥，去除上述的混合浆料中的溶剂，得到复合物；然后进行机械破碎、400目过筛处理后得到碳纳米管和聚合物包覆的负极材料。
负极极片的制备：集流体采用铜箔，厚度为10μm；活性材料采用上述硅基材料和石墨，其中硅基材料占活性材料层的质量比为10％；粘结剂采用 聚丙烯酸；将活性材料、导电炭黑、粘结剂按95：1.2：3.8混合后分散于水中形成浆料，经搅拌、涂布于铜箔上干燥、冷压、分条后得到负极极片。
正极极片制备：取正极活性物质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，涂覆于铝箔上，再经烘干、冷压，得到正极极片。
电池制备：以聚乙烯多孔聚合薄膜作为隔离膜，将正极极片、隔离膜、负极极片按顺序依次叠好，使隔离膜处于正积极片和负极极片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，注入含有碳酸乙烯酯(EC)和碳酸丙烯酯(PC)的电解液并封装，经过化成，脱气，切边等工艺流程得到锂离子电池。
在实施例2～22与对比例1～3中，正极极片、锂离子电池的制备均与实施例1相同，仅负极极片中的负极材料的制备不同，下面仅分别描述负极材料的制备的不同。在实施例2～6和对比例1中，将聚合物的种类分别更改为环氧树脂(含羟基及环氧基)、羧甲基纤维素锂(仅含羧基)、聚乙二醇(仅含羟基)、聚苯胺(仅含苯胺基)、聚硅氧烷(仅含环氧基)、聚乙烯(不含基团A和基团B)。
在实施例7～10和对比例2中，将聚合物的含量分别更改为1g、5g、10g、20g、0g，将硅基材料颗粒的含量则相应更改为94g、90g、85g、75g、95g。
在实施例11～14和对比例3中，将碳纳米管的含量分别更改为1g、3g、10g、20g、0g，将硅基材料颗粒的含量则相应更改为96g、94g、87g、77g、97g。
在实施例15～18中，将硅基材料颗粒的I 2/I 1值分别更改为0.41、0.64、1、2.5，其余不变。
在实施例19～22中，在负极材料中分别加入等量的微量掺杂金属元素锂、镁、钛、铝，其余不变。
实施例和对比例的各项参数的测定过程如下。
充放电测试：
将负极材料、导电炭黑与粘结剂聚丙烯酸(PAA)按照质量比80：10：10加去离子水经过搅成浆料，利用刮刀涂层100μm厚度的涂层，85℃经过 12小时真空干燥箱烘干后，在干燥环境中用冲压机切成直径为1cm的圆片，在手套箱中以金属锂片作为对电极，隔离膜选择ceglard复合膜，加入电解液组装成扣式电池。运用蓝电(LAND)系列电池测试测试对电池进行充放电测试，测试其充放电性能。
电子电导率测试：
采用四线两端子法，通过测量待测电阻两端电压和流经电流确定定体电阻，结合待测电阻的高度和底面积计算电导率。取一定量粉末加入到测试模具中，轻轻震平后，再将模具上的垫片放置在样品上；装样完毕后将模具置于电子压力试验机工作台面上，以5mm/min的速率升至500kg(159Mpa)，恒压60s，再卸压至0；当样品恒压至5000±2kg(升压到达5000kg后约15～25s)时记录样品压力，并读取样品变形高度，记录此时的电阻测试仪显示数值，即可采用公式计算电子电导率。
X射线衍射(XRD)测试：
称取样品1.0～2.0g倒入玻璃样品架的凹槽内，并用玻璃片将其压实和磨平，采用X射线衍射仪(布鲁克，D8)按照JJS K 0131-1996《X射线衍射分析法通则》进行测试，测试电压设置40kV，电流为30mA，扫描角度范围为10°～85°，扫描步长为0.0167°，每个步长所设置的时间为0.24s，得到XRD衍射图案，从图中得到2θ归属于28.4°最高强度数值I 2，与归属于21.0°最高强度I 1，从而计算出I 2/I 1的比值。
电池循环性能测试：
测试温度为45℃，以0.7C恒流充电到4.4V，再恒压充电到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，以每一步的容量与初始容量做比值，得到容量衰减曲线，统计容量衰减到初始容量80％的循环圈数。
直流阻抗(DCR)测试：
利用Maccor机在25℃测试电极组件的实际容量(0.7C恒流充电到4.4V,恒压充电到0.025C,静置10分钟，以0.1C放电到3.0V，静置5分钟)通过0.1C放电一定荷电状态(SOC)下，测试1s放电以5ms进行采点，计算出在不同SOC下的DCR值。
下面描述各个实施例和对比例的参数设置和性能结果。表1示出了实施例1～6和对比例1的参数设置，表2示出了相应的负极材料的电子电导率、电池首效以及电化学装置的循环性能和DCR。
表1
Figure PCTCN2020082266-appb-000001
表2
Figure PCTCN2020082266-appb-000002
通过比较实施例1～6和对比例1可知，与不具备基团A和基团B的聚合物相比，当聚合物同时具有基团A和基团B时，负极材料的电子电导率、电池首效、电化学装置的循环性能均有较大提高，电化学装置的DCR也有较大改善。这是因为两个基团的存在使得碳纳米管与硅基材料颗粒的结合更加紧密，同时分布也更加均匀，从而有效提高硅基材料的导电性和循环稳定性。而当聚合物只具有基团A或只具有基团B时，负极材料的电子电导率、电池首效、电化学装置的循环性能、DCR虽然也有一定改善，但不如聚合物同时具有基团A和基团B的情况，这是因为碳纳米管与硅基材料颗粒的结合不够紧密。图6示出了实施例1和对比例1的循环曲线，同样的循环圈数的情况下，实施例1的容量保持率要大。
表3示出了实施例1、7～10和对比例2的参数设置，表4示出了相应的负极材料的电子电导率、电池首效以及电化学装置的循环性能和DCR。
表3
Figure PCTCN2020082266-appb-000003
表4
Figure PCTCN2020082266-appb-000004
通过比较实施例1、7～10和对比例2可知，当聚合物同时具有基团A和基团B，且碳纳米管的含量相同时，聚合物的含量对负极材料的性能也具有一定影响。当聚合物的含量过少时，无法有效地增强硅基材料颗粒与碳纳米管之间的结合，使得负极材料的电子电导率、电池首效、电化学装置的循环性能、DCR等无法得到有效地改善；当聚合物的含量过多时，虽然可以通过两种基团有效地增强硅基材料颗粒与碳纳米管之间的结合，但是由于聚合物本身导电性较差，过多的聚合物会导致负极材料的电子电导率降低，进而使得电池首效、电化学装置的循环性能、DCR等无法得到有效地改善。
表5示出了实施例1、11～14和对比例3的参数设置，表6示出了相应的负极材料的电子电导率、电池首效以及电化学装置的循环性能和DCR。
表5
Figure PCTCN2020082266-appb-000005
Figure PCTCN2020082266-appb-000006
表6
Figure PCTCN2020082266-appb-000007
通过比较实施例1、11～14和对比例3可知，当聚合物同时具有基团A和基团B，且聚合物含量相同时，随着碳纳米管含量的增加，负极材料的导电性能、电池首效、电化学装置的DCR有改善的趋势，但是电化学装置的循环性能呈现先提升后下降的趋势，这说明当碳纳米管含量过大时，包覆层过厚，不利于锂离子的迁移，从而恶化了电化学装置的循环性能。
表7示出了实施例1和15～18的参数设置，表8示出了相应的负极材料的电子电导率、电池首效以及电化学装置的循环性能和DCR。图5示出了实施例1中的硅基材料颗粒的X射线衍射图。
表7
Figure PCTCN2020082266-appb-000008
表8
Figure PCTCN2020082266-appb-000009
通过比较实施例1和15～18可知，当聚合物同时具有基团A和基团B，且聚合物含量和碳纳米管含量相同时，负极材料的导电性能、电池首效、电化学装置的DCR基本持平。但是随着硅基材料的I 2/I 1的值不断增加，电化学装置的循环性能不断降低。I 2/I 1的值反映了硅基材料受到歧化的影响程度，I 2/I 1的值越大，硅基材料内部产生的SiO歧化产生的纳米硅晶粒的尺寸越大，在嵌锂过程中会导致局部区域的应力急剧增大，从而导致硅基材料在循环过程中的结构破坏。
表9示出了实施例1和19～22的参数设置，表10示出了相应的负极材料的电子电导率、电池首效以及电化学装置的循环性能和DCR。
表9
Figure PCTCN2020082266-appb-000010
表10
Figure PCTCN2020082266-appb-000011
通过比较实施例1和19～22可知，当聚合物同时具有基团A和基团B，且聚合物含量和碳纳米管含量相同时，负极材料中掺杂金属元素对负极材料的导电性能、电池首效、电化学装置的循环性能和DCR均有改善作用，掺杂金属元素的种类的差别虽然对这些性能有一定的影响，但区别较小。
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，同时也应涵盖在不脱离上述公开构思的 情况下，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 (12)

  1. 一种负极材料，包括：
    由硅基材料、聚合物和碳纳米管形成的复合物，
    其中，所述聚合物具有第一基团和第二基团，所述第一基团化学键合至所述碳纳米管，所述第二基团化学键合至所述硅基材料。
  2. 根据权利要求1所述的负极材料，其中，所述硅基材料的表面存在所述碳纳米管。
  3. 根据权利要求1所述的负极材料，其中，所述第一基团包括环氧基、酚羟基、苯胺基、苯基、萘基、蒽基、菲基、苯醚基、吡咯、吡啶或呋喃中的至少一种。
  4. 根据权利要求1所述的负极材料，其中，所述第二基团包括羧基、羟基、酚羟基、醛基、酰胺基、酰卤基、酯基、羰基或卤代烃基中的至少一种。
  5. 根据权利要求1所述的负极材料，其中，所述复合物中的所述聚合物的质量百分比为0.5％～10％。
  6. 根据权利要求1所述的负极材料，其中，所述复合物中的所述碳纳米管的质量百分比为0.5％～10％。
  7. 根据权利要求1所述的负极材料，其中，所述复合物中的所述硅基材料、所述聚合物和所述碳纳米管的质量比为85～96.5：0.5～10：0.5～10。
  8. 根据权利要求1所述的负极材料，其中，所述硅基材料在X射线衍射图案中2θ归属于20.5°～21.5°范围内的最高强度数值为I 1，归属于28.0°～29.0°范围内的最高强度数值为I 2，0<I 2/I 1≤3。
  9. 根据权利要求1所述的负极材料，其中，所述负极材料还掺杂有锂、镁、钛或铝中的至少一种元素。
  10. 一种负极极片，包括：
    集流体；
    活性物质层，位于所述集流体上；
    其中，所述活性物质层包括根据权利要求1至9中任一项所述的负极材料。
  11. 一种电化学装置，包括：
    正极极片；
    负极极片；
    隔离膜，设置于所述正极极片和所述负极极片之间；
    其中，所述负极极片为根据权利要求10所述的负极极片。
  12. 一种电子装置，包括根据权利要求11所述的电化学装置。
PCT/CN2020/082266 2020-03-31 2020-03-31 负极材料、负极极片、电化学装置和电子装置 WO2021195913A1 (zh)

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