WO2023184127A1 - 负极极片、电化学装置及电子设备 - Google Patents

负极极片、电化学装置及电子设备 Download PDF

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WO2023184127A1
WO2023184127A1 PCT/CN2022/083535 CN2022083535W WO2023184127A1 WO 2023184127 A1 WO2023184127 A1 WO 2023184127A1 CN 2022083535 W CN2022083535 W CN 2022083535W WO 2023184127 A1 WO2023184127 A1 WO 2023184127A1
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carbon
negative electrode
active material
containing silicon
composite particles
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French (fr)
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任文臣
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Ningde Amperex Technology Ltd
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Ningde Amperex Technology Ltd
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Priority to EP22933984.1A priority Critical patent/EP4485561A4/en
Priority to CN202280012067.XA priority patent/CN116848656A/zh
Priority to PCT/CN2022/083535 priority patent/WO2023184127A1/zh
Publication of WO2023184127A1 publication Critical patent/WO2023184127A1/zh
Priority to US18/897,099 priority patent/US20250023025A1/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • H01M4/139—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
    • H01M4/362—Composites
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • 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
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • 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
    • 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

  • This application belongs to the technical field of secondary batteries, and specifically relates to a negative electrode plate, electrochemical device and electronic equipment.
  • Secondary batteries have outstanding characteristics such as high energy density, long cycle life, no pollution, and no memory effect. As a clean energy source, the application of secondary batteries has gradually spread from electronic products to large-scale devices such as electric vehicles to adapt to the sustainable development strategy of the environment and energy. As a result, higher requirements have been placed on the energy density of secondary batteries.
  • silicon anode material Si has attracted much attention due to its theoretical capacity that is much higher than that of carbon materials.
  • the silicon anode material has a serious volume effect, which will cause huge volume shrinkage and expansion during the charge and discharge process. Therefore, during the charge and discharge process, the silicon anode material is easily broken, so that it cannot be placed on the surface of the negative electrode piece. Form a stable SEI film. Therefore, when silicon anode materials are used in secondary batteries, it is easy to cause electrolyte consumption and pulverization of the anode film layer, resulting in capacity attenuation of the secondary battery and reduction of the rate performance and cycle stability of the secondary battery.
  • the purpose of this application is to provide a negative electrode plate, electrochemical device and electronic equipment, aiming to reduce the volume expansion rate of the negative active material particles in the negative active material layer, improve the active ion conductivity of the negative electrode plate, thereby improving the secondary Battery cycle capacity retention, rate performance and cycle stability.
  • a first aspect of the present application provides a negative electrode sheet, which includes a negative electrode current collector and a negative electrode active material layer located on at least one side of the negative electrode current collector,
  • the negative active material layer includes carbon-containing silicon-oxygen composite particles,
  • C atoms can replace Si-O bonds inside SiO x particles to form Si-C and OC bonds.
  • the number of Si-O bonds can be reduced, thereby reducing the number of Si-Si bonds formed after the Si-O bonds are broken, thereby preventing excessive stress in the Si atom-rich region from causing expansion and cracking of the negative electrode material particles.
  • the above-mentioned carbon-containing silicon-oxygen composite particles are included in the negative active material layer of the negative electrode piece, and the X-ray diffraction pattern of the negative electrode piece meets the above conditions, which can effectively reduce the volume expansion rate of the negative electrode active material particles and improve the negative electrode
  • the active ion conductivity of the pole piece improves the cycle capacity retention rate, rate performance and cycle stability of the secondary battery.
  • silicon crystallites of appropriate size can be formed during the charge and discharge cycle of the secondary battery.
  • the silicon crystallites have a suitable size, the negative active material particles can have a lower volume expansion rate, thereby reducing the risk of expansion and cracking of the negative active material particles. Therefore, when the negative electrode plate is used in secondary batteries, the secondary batteries can have high cycle capacity retention, good rate performance and cycle stability.
  • the Raman spectrum of the carbon-containing silicon-oxygen composite particles satisfies: I D > I G , where I D is the intensity of the D band peak, I G is the intensity of the G band peak, optional Ground, 1.1 ⁇ I D /I G ⁇ 2.0.
  • I D is the intensity of the D band peak
  • I G is the intensity of the G band peak
  • optional Ground 1.1 ⁇ I D /I G ⁇ 2.0.
  • the carbon-containing silicon-oxygen composite particles can have appropriate Structure.
  • the negative electrode material particles can have a lower volume expansion rate during the charge and discharge cycle of the secondary battery. Therefore, secondary batteries using the negative electrode sheet can have high cycle capacity retention, good rate performance and cycle stability.
  • the content of carbon is 0.5% to 10% based on the total mass of carbon, silicon and oxygen.
  • the distribution of carbon, silicon and oxygen meets the above conditions, which can make the proportion of Si-O bonds, Si-C bonds and O-C bonds appropriate.
  • the negative electrode material particles can Has lower volume expansion rate. Therefore, secondary batteries using the negative electrode sheet can have high cycle capacity retention, good rate performance and cycle stability.
  • the conductive polymer includes polyvinylidene fluoride and its derivatives, carboxymethylcellulose and its derivatives, polyvinylpyrrolidone and its derivatives, polyvinyl alcohol and its derivatives, One or more of polyacrylic acid and its derivatives, styrene-butadiene rubber, polyacrylamide, polyimide, PEDOT: PSS and its derivatives, and polyamide-imide.
  • the carbon material includes one or more of carbon fiber, carbon nanotube, graphene, graphite and amorphous carbon.
  • the Me includes at least one of Mg, Al, Ti, Zn, Ni, Mn, V, Cr, Co and Zr.
  • the thickness of the coating layer is 0.1 nm to 10 nm.
  • the thickness of the coating layer is 1 nm to 3 nm.
  • the volume average particle diameter D V50 of the carbon-containing silicon-oxygen composite particles is 2.5 ⁇ m to 10 ⁇ m, and the linear average particle diameter D n10 of the carbon-containing silicon-oxygen composite particles is consistent with the The D v50 satisfies: 0.3 ⁇ Dn 10 /Dv 50 ⁇ 0.6.
  • the powder compaction density of the carbon-containing silicon-oxygen composite particles under a pressure of 5000kg is 1.21g/cm 3 to 1.50g/cm 3 .
  • a second aspect of the present application provides an electrochemical device, which includes the negative electrode plate of the first aspect of the present application.
  • the electrochemical device is a lithium-ion battery.
  • a third aspect of the present application provides an electronic device, which includes the electrochemical device of the second aspect of the present application.
  • Figure 1 is an XRD test chart of negative active material particles according to an embodiment of the present application.
  • Figure 2 is a scanning electron microscope image (SEM image) of a cross section of negative active material particles according to an embodiment of the present application.
  • Figure 3 is an element line distribution curve obtained by performing a linear scan according to the SEM image of the cross-section of the negative active material particles in Figure 2 of the present application.
  • Figure 4 is an XRD test chart of the negative electrode plate according to an embodiment of the present application.
  • any lower limit can be combined with any upper limit to form an unexpressed range; and any lower limit can be combined with other lower limits to form an unexpressed range, and likewise any upper limit can be combined with any other upper limit to form an unexpressed range.
  • every point or individual value between the endpoints of a range is included in the range.
  • each point or single value may serve as a lower or upper limit on its own in combination with any other point or single value or with other lower or upper limits to form a range not expressly recited.
  • a term may refer to a variation of less than or equal to ⁇ 10% of the stated numerical value, such as less than or equal to ⁇ 5%, less than or equal to ⁇ 4%, less than or equal to ⁇ 3%, Less than or equal to ⁇ 2%, less than or equal to ⁇ 1%, less than or equal to ⁇ 0.5%, less than or equal to ⁇ 0.1%, or less than or equal to ⁇ 0.05%. Additionally, quantities, ratios, and other numerical values are sometimes presented herein in range format.
  • a list of items connected by the terms “at least one of,” “at least one of,” “at least one of,” or other similar terms may 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 only A; only B; or A and B. In another example, if the items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; 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 silicon negative electrode material has a high theoretical capacity, due to its severe volume effect, its application in secondary batteries can easily cause the consumption of electrolyte and the powdering of the negative electrode film layer, resulting in the failure of the secondary battery. Capacity fading, reducing rate performance and cycle stability of secondary batteries.
  • Silicone oxide ( SiO Anode materials have lower volume effects. However, the volume effect of silicon oxide still cannot meet market expectations for anode materials.
  • disproportionation treatment is to convert part of the oxidized silicon into quartz phase SiO 2 and Si nanocrystals at high temperature.
  • SiO 2 covers the surface of Si nanocrystals and acts as a buffer substance to inhibit the lithium intercalation process of Si nanocrystals.
  • Surface coating uses metal oxides , polymers, etc. to coat SiO Both methods build buffer regions to limit the volume expansion of Si during the lithium insertion process.
  • Nanonizing SiO x can reduce the volume expansion rate of SiO x itself, thus solving the problem of excessive volume expansion of the anode material during the lithium insertion process.
  • Due to the large specific surface area of nano-treated SiO x it will consume a large amount of electrolyte and form a thick SEI film, thereby negatively affecting the first Coulombic efficiency and cycle performance of the secondary battery.
  • the inventor provided a negative electrode plate after in-depth thinking and experiments.
  • the negative electrode plate is used in secondary batteries and can enable the secondary batteries to have high cycle capacity retention rate and good electrochemical performance.
  • the inventor provides a negative electrode sheet, which includes a negative electrode current collector and a negative electrode active material layer located on at least one side of the negative electrode current collector.
  • the negative active material layer includes carbon-containing silicon-oxygen composite particles.
  • the carbon-containing silicon-oxygen composite particles may be silicon oxide particles doped with atomic-level carbon elements in the bulk phase.
  • the carbon-containing silicon-oxygen composite particles may be composite particles obtained by bulk carbon doping of SiO x .
  • the mass percentage of carbon element in the carbon-containing silicon-oxygen composite may be 0.5%-10%.
  • the mass percentage of carbon element can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5 %, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10% or within the range of any of the above values.
  • the carbon-containing silicon-oxygen composite particles may be SiC x O y particles, where 0 ⁇ x ⁇ 0.04, 0.8 ⁇ y ⁇ 1.2.
  • C atoms can replace Si-O bonds inside the SiO x particles to form Si-C and OC bonds.
  • the number of Si-O bonds can be reduced, thereby reducing the number of Si-Si bonds formed after the Si-O bonds are broken, thereby preventing excessive stress in the Si atom-rich region from causing expansion and cracking of the negative electrode material particles.
  • the inventor unexpectedly found that the above-mentioned carbon-containing silicon-oxygen composite particles are included in the negative active material layer of the negative electrode plate, and the X-ray diffraction pattern of the negative electrode plate satisfies the above conditions, which can effectively Reduce the volume expansion rate of the negative active material particles and improve the active ion conductivity of the negative electrode sheet, thereby improving the cycle capacity retention rate, rate performance and cycle stability of the secondary battery.
  • the negative electrode piece can contain specific components, such as a specific proportion of silicates with different structures. These specific ingredients can not only inhibit the expansion of silicon crystallites, but also help enhance the mass transfer process of electrochemical reactions, thereby improving the cycle capacity retention rate, rate performance and cycle stability of secondary batteries.
  • the X-ray diffraction pattern of the carbon-containing silicon-oxygen composite particles can satisfy: I 3 /I 4 ⁇ 2, for example, 0 ⁇ I 3 /I 4 ⁇ 2, 0.5 ⁇ I 3 /I 4 ⁇ 1.8, 0.8 ⁇ I 3 /I 4 ⁇ 1.5 or 1.0 ⁇ I 3 /I 4 ⁇ 1.2.
  • the value of I 3 /I 4 can reflect the degree of disproportionation of carbon-containing silicon-oxygen composite particles.
  • silicon crystallites of appropriate size can be formed during the charge and discharge cycles of the secondary battery.
  • the silicon crystallites have a suitable size, the negative active material particles can have a lower volume expansion rate, thereby reducing the risk of expansion and cracking of the negative active material particles. Therefore, when the negative electrode plate is used in secondary batteries, the secondary batteries can have high cycle capacity retention, good rate performance and cycle stability.
  • the Raman spectrum of the carbon-containing silicon-oxygen composite particles can satisfy: I D > I G , where I D is the intensity of the D band peak and I G is the intensity of the G band peak.
  • the Raman spectrum of the carbon-containing silicon-oxygen composite particles satisfies 1.1 ⁇ ID / IG ⁇ 2.0 , for example, 1, 1 ⁇ ID / IG ⁇ 2.0 , 1.3 ⁇ ID / IG ⁇ 2.0, 1.5 ⁇ I D /I G ⁇ 2.0, 1.7 ⁇ I D /I G ⁇ 2.0, 1.9 ⁇ I D /I G ⁇ 2.0, 1.1 ⁇ I D /I G ⁇ 1.8 , 1.3 ⁇ I D /I G ⁇ 1.8, 1.5 ⁇ I D /I G ⁇ 1.8 , 1.7 ⁇ I D /I G ⁇ 1.8, 1.1 ⁇ I D /I G ⁇ 1.6, 1.3 ⁇ I D /I G ⁇ 1.6 , 1.5 ⁇ I D /I G ⁇ 1.6, 1.1 ⁇ I D
  • the carbon-containing silicon-oxygen composite in the Raman spectrum of carbon-containing silicon-oxygen composite particles, when the intensity of the D-band peak and the intensity of the G-band peak meet the above conditions, the carbon-containing silicon-oxygen composite can be considered
  • the carbon content doped in the particles is within a suitable range, and the carbon-containing silicon-oxygen composite particles can have a suitable structure.
  • the ratio of Si-O bonds, Si-C bonds, and O-C bonds is appropriate, and the negative electrode material particles can have a lower volume expansion rate during the charge and discharge cycle of the secondary battery. Therefore, secondary batteries using the negative electrode sheet can have high cycle capacity retention, good rate performance and cycle stability.
  • the carbon content in any region of the negative active material layer including carbon-containing silicon-oxygen composite particles, may be 0.5% to 10% based on the total mass of carbon, silicon, and oxygen.
  • the mass percentage content of the carbon element in any area of the negative active material layer including carbon-containing silicon-oxygen composite particles, based on the total mass of carbon, silicon and oxygen, can be 0.5%, 1%, 1.5%, 2% , 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10% or at Within the range composed of any of the above values.
  • the distribution of carbon, silicon, and oxygen in the negative active material layer satisfies the above conditions, enabling an appropriate proportion of Si-O bonds, Si-C bonds, and O-C bonds, and the negative electrode material particles are
  • the secondary battery can have a lower volume expansion rate during the charge and discharge cycle. Therefore, secondary batteries using the negative electrode sheet can have high cycle capacity retention, good rate performance and cycle stability.
  • the coating layer can be physically coated on the surface of the carbon-containing silicon-oxygen composite particles, or can be chemically coated on the surface of the carbon-containing silicon-oxygen composite particles, which is not limited here.
  • the cladding layer can have a single-layer structure or a multi-layer structure.
  • the cladding layer may include one or more of conductive polymer, carbon material, and oxide MeO z .
  • each single layer of the cladding layer may include one or more of conductive polymer, carbon material, and oxide MeOz .
  • the conductive polymer may include polyvinylidene fluoride (PVDF) and its derivatives, carboxymethylcellulose (CMC) and its derivatives, polyvinylpyrrolidone (PVP) and its derivatives, Polyvinyl alcohol (PVA) and its derivatives, polyacrylic acid (PAA) and its derivatives, styrene-butadiene rubber SBR, polyacrylamide (PAM), polyimide (PI), PEDOT: PSS and its derivatives, poly One or more of amide imides (PAI).
  • PVDF polyvinylidene fluoride
  • CMC carboxymethylcellulose
  • PVP polyvinylpyrrolidone
  • PVA Polyvinyl alcohol
  • PAA polyacrylic acid
  • SBR polyacrylamide
  • PAM polyimide
  • PEDOT PEDOT: PSS and its derivatives
  • PAI poly One or more of amide imides
  • the carbon material may include one or more of carbon fibers, carbon nanotubes, graphene, graphite, and amorphous carbon.
  • Me in the oxide MeOz may include one or more of Mg, Al, Ti, Zn, Ni, Mn, V, Cr, Co and Zr.
  • Me includes one or more of Mg, Al, and Ni.
  • the inventor found that the above-mentioned coating layer coating the surface of the carbon-containing silicon-oxygen composite particles can interact with the functional groups on the surface of the carbon-containing silicon-oxygen composite particles, Thus, a three-dimensional conductive network with a certain mechanical strength is formed.
  • the three-dimensional conductive network has a certain mechanical strength and can inhibit the volume expansion of the negative active material particles during the lithium insertion process through binding.
  • the three-dimensional conductive network can improve the conductive performance of the negative active material. This can reduce the surface resistance of the negative electrode piece. As a result, the volume expansion of the negative active material particles can be suppressed while the conductive performance of the negative active material can be improved, thereby improving the cycle capacity retention rate, rate performance and cycle stability of the secondary battery.
  • the conductive polymer, carbon material, and oxide MeO z are selected from the above-mentioned suitable materials.
  • the coating layer can have better mechanical properties and conductive properties. Therefore, the volume expansion rate of the negative active material particles can be further reduced and the conductive properties of the negative active material particles can be improved, thereby improving the cycle capacity retention rate, rate performance and cycle stability of the secondary battery.
  • the thickness of the cladding layer may be 0.1 nm to 10 nm. In some embodiments, the thickness of the cladding layer may be 1 nm to 3 nm. In some embodiments, the thickness of the coating layer may be 0.5nm, 0.8nm, 1nm, 1.2nm, 1.5nm, 1.8nm, 2nm, 2.5nm, 2.8nm, 3nm, 3.5nm, 3.8nm, 4nm, 4.5nm, 5nm, 5.5nm, 6nm, 6.5nm, 7nm, 7.5nm, 8nm, 8.5nm, 9nm, 9.5nm, 10nm or within the range of any of the above values.
  • the thickness of the coating layer within the above range can have both good mechanical properties and electrical conductivity, thereby effectively suppressing the volume expansion of the negative active material particles and improving the performance of the negative active material. Conductive properties.
  • the thickness of the coating layer when the thickness of the coating layer is within the above-mentioned appropriate range, the negative electrode piece can also have a high energy density, thereby improving the energy density of the secondary battery.
  • the volume average particle diameter D V50 of the carbon-containing silicon-oxygen composite particles is 2.5 ⁇ m to 10 ⁇ m
  • the linear average particle diameter D n10 of the carbon-containing silicon-oxygen composite particles is consistent with the D v50 can satisfy: 0.3 ⁇ Dn 10 /Dv 50 ⁇ 0.6.
  • Dn 10 /Dv 50 can be 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6 or within the range of any of the above values.
  • Controlling the volume average particle size D V50 of the negative active material within an appropriate range can shorten the diffusion path of active ions and facilitate the formation of a smooth pore structure in the negative active material layer. Therefore, the negative electrode plate can have good liquid phase transmission performance and good active ion solid phase diffusion performance at the same time.
  • the inventor unexpectedly found that when the linear average particle diameter D n10 and the D v50 of the carbon-containing silicon-oxygen composite particles meet the above conditions, it is beneficial to the negative electrode active material. capacity, ensuring the secondary battery has high rate performance and good cycle stability.
  • the carbon-containing silicon -oxygen composite particles may have a powder compacted density of 1.21 to 1.50 g/cm 3 under a pressure of 5000 kg.
  • the powder compaction density of the carbon-containing silicon-oxygen composite particles under a pressure of 5000kg can be 1.21g/cm 3 to 1.48g/cm 3 , 1.25g/cm 3 to 1.45g/cm 3 , 1.30g /cm 3 to 1.42g/cm 3 , 1.35g/cm 3 to 1.40g/cm 3 .
  • the powder compaction density of the carbon-containing silicon-oxygen composite particles under 5000kg pressure can be 1.21g/cm 3 , 1.25g/cm 3 , 1.28g/cm 3 , 1.31g/cm 3 , 1.35g/cm 3 , 1.38g/cm 3 , 1.41g/cm 3 , 1.45g/cm 3 , 1.48g/cm 3 , 150g/cm 3 or within the range of any of the above values.
  • the powder compaction density of carbon-containing silicon-oxygen composite particles under a pressure of 5000kg is within the given range, which can make the particles in the negative active material layer in close contact and increase the active material content per unit volume, thus improving the Battery energy density.
  • Metal foil or porous metal plate may be used, for example, foil or porous plate using metals such as copper, nickel, titanium, iron or alloys thereof.
  • the negative electrode current collector is copper foil.
  • the negative electrode current collector has two opposite sides in its thickness direction, and the negative electrode active material layer may be disposed on one side of the negative electrode current collector, or may be disposed on both sides of the negative electrode current collector.
  • the negative electrode current collector has two sides opposite in its own thickness direction, and the negative electrode active material layer is disposed on any one or both sides of the opposite sides of the negative electrode current collector.
  • other negative active materials other than the carbon-containing silicon-oxygen composite particles are not excluded from the negative active material layer.
  • the specific types of other negative active materials are not subject to specific restrictions and can be selected according to needs.
  • other negative active materials include, but are not limited to, natural graphite, artificial graphite, mesophase microcarbon beads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, SiO, Li-Sn alloy, Li-Sn -O alloy, Sn, SnO, SnO 2 , spinel structure Li 4 Ti 5 O 12 , and Li-Al alloy.
  • the negative active material layer optionally further includes a binder.
  • the binder may be selected from polyacrylate, polyimide, polyamide, polyamideimide, polyvinylidene fluoride, styrene-butadiene rubber, sodium alginate, polyvinyl alcohol, polytetrafluoroethylene, and polypropylene At least one of nitrile, sodium carboxymethylcellulose, potassium carboxymethylcellulose, sodium carboxymethylcellulose, and potassium carboxymethylcellulose.
  • the negative active material layer optionally further includes a conductive agent.
  • the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the negative active material layer optionally also includes other auxiliaries, such as thickeners (such as sodium carboxymethyl cellulose (CMC-Na)) and the like.
  • auxiliaries such as thickeners (such as sodium carboxymethyl cellulose (CMC-Na)) and the like.
  • the negative electrode piece in this application can be prepared according to conventional methods in this field.
  • the carbon-containing silicon-oxygen composite particles and optional other negative active materials, conductive agents, binders and thickeners are dispersed in a solvent.
  • the solvent can be N-methylpyrrolidone (NMP) or deionized water to form a uniform negative electrode slurry, apply the negative electrode slurry on the negative electrode current collector, and obtain the negative electrode piece through drying, cold pressing and other processes.
  • NMP N-methylpyrrolidone
  • each negative active material layer given in this application refers to the parameter range of the single-sided negative active material layer.
  • the negative active material layer is disposed on both sides of the negative current collector, if the parameters of the negative active material layer on either side meet the requirements of this application, it is deemed to fall within the protection scope of this application.
  • the negative electrode sheet in this application does not exclude other additional functional layers in addition to the negative active material layer.
  • the negative electrode sheet of the present application also includes a conductive undercoat layer (for example, composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode active material layer and disposed on the surface of the negative electrode current collector. composition).
  • the negative electrode sheet of the present application further includes a protective layer covering the surface of the negative active material layer.
  • XRD patterns can be determined by methods and instruments known in the art. For example, it can be obtained through XRD testing using the °/min, 2 ⁇ range is 10-80°.
  • Raman spectra can be measured by methods and instruments known in the art. For example, it can be obtained by using the HORIBA LabRAM HR Evolution high-resolution Raman spectrometer for Raman testing. Specifically, it can be tested using an Ar ion laser as the light source.
  • the carbon content can be determined by the cross-section of the carbon-containing silicon-oxygen composite particles.
  • Element distribution test chart determined.
  • carbon-containing silicon-oxygen composite particles can be sprinkled on the copper foil of the conductive adhesive, cut into cross-sections, and polished using a plasma polishing machine (Leica EM TIC 3X-Ion Beam Slope Cutter). Then put the copper foil into a scanning electron microscope (SEM) to find the cut negative active material particles.
  • SEM scanning electron microscope
  • FIB focused ion beam
  • TEM transmission electron microscopy
  • EDS energy dispersive spectroscopy
  • the thickness of the coating layer on the surface of the carbon-containing silicon-oxygen composite particles has a meaning known in the art, and can be measured using methods and instruments known in the art.
  • a scanning electron microscope (SEM) can be used to observe the micromorphology of the sample (for example, particle agglomeration) to characterize the coating of the sample surface.
  • the testing instrument can be OXFORD EDS (X-max-20mm 2 ), acceleration voltage is 10KV.
  • the volume average particle diameter D V50 of the carbon-containing silicon-oxygen composite particles and the linear average particle diameter D n10 of the carbon-containing silicon-oxygen composite particles have meanings known in the art, and methods known in the art can be used. Methods and Instrumental Determinations. For example, you can refer to GB/T 19077-2016 particle size distribution laser diffraction method and use a laser particle size analyzer (such as Malvern Mastersizer 2000E, UK) to measure it.
  • a laser particle size analyzer such as Malvern Mastersizer 2000E, UK
  • the powder compaction density of carbon-containing silicon-oxygen composite particles under a pressure of 5000kg has a meaning known in the art and can be measured using methods known in the art.
  • An exemplary test method is as follows: weigh 1g of carbon-containing silicon-oxygen composite particles, add it to a mold with a base area of 1.327cm2 , pressurize to 5000kg, hold the pressure for 30s, then release the pressure, hold for 10s, then record and calculate The powder compaction density of the negative active material under a pressure of 5000kg.
  • the sample can be sampled according to the following steps S10-S30.
  • step S20 Bake the negative electrode sheet dried in step S10 at a certain temperature and time (for example, 400°C, 2 hours). Select an area in the baked negative electrode sheet to sample the negative electrode active material (you can choose blade scraper powder sampling).
  • step S30 sieve the negative active material collected in step S20 (for example, using a 200-mesh screen) to finally obtain a sample that can be used to test the parameters of each negative active material mentioned above in this application.
  • a second aspect of the present application provides an electrochemical device, including any device in which an electrochemical reaction occurs to convert chemical energy into electrical energy.
  • the lithium secondary battery includes a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery or a lithium ion polymer secondary battery.
  • the electrochemical device of the present application includes a positive electrode piece, a negative electrode piece, a separator and an electrolyte.
  • the positive electrode piece, the negative electrode piece and the separator film can be made into an electrode assembly through a winding process or a lamination process.
  • the electrochemical device of the present application also includes an outer package for packaging the electrode assembly and the electrolyte.
  • the outer packaging can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc., or a soft bag, such as a bag-type soft bag.
  • the soft bag may be made of plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PBS polybutylene succinate
  • the negative electrode sheet used in the electrochemical device of the present application is the negative electrode sheet of the first aspect of the present application.
  • the material, composition and manufacturing method of the positive electrode piece used in the electrochemical device of the present application may include any technology known in the prior art.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector and including a positive electrode active material.
  • the positive electrode current collector has two surfaces facing each other in its own thickness direction, and the positive electrode active material layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive active material layer includes a positive active material.
  • the specific type of the positive active material is not specifically limited and can be selected according to requirements.
  • the cathode active material may include one or more of lithium transition metal oxides, lithium-containing phosphates with an olivine structure, and their respective modified compounds.
  • the above-mentioned modified compounds of each positive electrode active material may be doping modification, surface coating modification, or doping and surface coating modification of the positive electrode active material.
  • lithium transition metal oxides may include lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, One or more of lithium nickel cobalt aluminum oxide and its modified compounds.
  • the lithium-containing phosphate with an olivine structure may include lithium iron phosphate, a composite of lithium iron phosphate and carbon, a lithium manganese phosphate, a composite of lithium manganese phosphate and carbon, a lithium manganese iron phosphate, a lithium manganese iron phosphate and carbon One or more of the composite materials and their modified compounds.
  • These positive electrode active materials may be used alone or in combination of two or more.
  • the positive active material layer optionally further includes a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the positive active material layer optionally further includes a binder.
  • the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene At least one of ethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • a metal foil aluminum foil can be used as the positive electrode current collector.
  • the composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer.
  • the metal material may be selected from one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy.
  • the polymer material base layer may be selected from polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.
  • the positive electrode piece in this application can be prepared according to conventional methods in this field.
  • the positive electrode active material layer is usually formed by coating the positive electrode slurry on the positive electrode current collector, drying, and cold pressing.
  • the cathode slurry is usually formed by dispersing the cathode active material, optional conductive agent, optional binder and any other components in a solvent and stirring evenly.
  • the solvent may be N-methylpyrrolidone (NMP), but is not limited thereto.
  • the positive electrode sheet of the present application does not exclude other additional functional layers in addition to the positive active material layer.
  • the positive electrode sheet of the present application also includes a conductive undercoat layer (for example, composed of a conductive agent and a binder) sandwiched between the positive electrode current collector and the positive electrode active material layer and disposed on the surface of the positive electrode current collector. ).
  • the positive electrode sheet of the present application further includes a protective layer covering the surface of the positive electrode active material layer.
  • the electrolyte plays a role in conducting active ions between the positive electrode piece and the negative electrode piece.
  • the electrolyte solution that can be used in the electrochemical device of the present application can be an electrolyte solution known in the art.
  • the electrolyte solution includes an organic solvent, a lithium salt and optional additives.
  • organic solvent a lithium salt and optional additives.
  • the types of the organic solvent, lithium salt and additives are not specifically limited and can be selected according to needs.
  • the lithium salts include, but are not limited to, LiPF 6 (lithium hexafluorophosphate), LiBF 4 (lithium tetrafluoroborate), LiClO 4 (lithium perchlorate), LiFSI (lithium bisfluorosulfonimide) ), LiTFSI (lithium bistrifluoromethanesulfonimide), LiTFS (lithium trifluoromethanesulfonate), LiDFOB (lithium difluoromethanesulfonate), LiBOB (lithium difluoromethanesulfonate), LiPO 2 F 2 (difluorophosphoric acid Lithium), LiDFOP (lithium difluorodioxalate phosphate) and LiTFOP (lithium tetrafluorooxalate phosphate).
  • LiPF 6 lithium hexafluorophosphate
  • LiBF 4 lithium tetrafluoroborate
  • LiClO 4 lithium perchlorate
  • LiFSI
  • the organic solvent includes, but is not limited to, ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), carbonic acid Dimethyl ester (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate Ester (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), Methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS)
  • EC ethylene carbon
  • the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain properties of the battery, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance. wait.
  • the additives include, but are not limited to, fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), vinyl sulfate (DTD), propylene sulfate, vinyl sulfite Esters (ES), 1,3-propene sultone (PS), 1,3-propene sultone (PST), sulfonate cyclic quaternary ammonium salts, succinic anhydride, succinonitrile (SN) , at least one of adiponitrile (AND), tris(trimethylsilane)phosphate (TMSP), and tris(trimethylsilane)borate (TMSB).
  • FEC fluoroethylene carbonate
  • VC vinylene carbonate
  • VEC vinyl ethylene carbonate
  • DTD vinyl sulfate
  • ES vinyl sulfite Esters
  • PS 1,3-propene sultone
  • PST 1,3-propene sultone
  • the electrolyte solution can be prepared according to conventional methods in the art.
  • the organic solvent, lithium salt, and optional additives can be mixed evenly to obtain an electrolyte.
  • the materials There is no particular restriction on the order in which the materials are added. For example, add lithium salt and optional additives to the organic solvent and mix evenly to obtain an electrolyte; or add lithium salt to the organic solvent first, and then add the optional additives.
  • the additives are added to the organic solvent and mixed evenly to obtain an electrolyte.
  • the isolation film is placed between the positive electrode piece and the negative electrode piece. It mainly prevents the positive and negative electrodes from short-circuiting and allows active ions to pass through.
  • isolation membrane There is no particular restriction on the type of isolation membrane in this application. Any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be used.
  • the material of the isolation membrane can be selected from one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride, but is not limited to these.
  • the isolation film can be a single-layer film or a multi-layer composite film. When the isolation film is a multi-layer composite film, the materials of each layer may be the same or different. In some embodiments, a ceramic coating or a metal oxide coating can also be provided on the isolation film.
  • a third aspect of the present application provides an electronic device, which includes the electrochemical device of the second aspect of the present application.
  • the electronic device of the present application is not particularly limited and may be used in any electronic device known in the art.
  • electronic devices may include, but are not limited to, laptop computers, pen computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headsets, video recorders , LCD TV, portable cleaner, portable CD player, mini CD, transceiver, electronic notepad, calculator, memory card, portable recorder, radio, backup power supply, motor, automobile, motorcycle, power-assisted bicycle, bicycle, lighting Appliances, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries and lithium-ion capacitors, etc.
  • the above-mentioned carbon-containing silicon-oxygen composite particles are the negative electrode active material particles in Examples 1 to 6.
  • a mixed negative active material After uniformly mixing the negative active material particles and graphite at a mass ratio of 15.5:84.5, a mixed negative active material is obtained.
  • the negative electrode slurry is evenly coated on both surfaces of the negative electrode current collector copper foil; then it is dried in a 120°C oven, cold pressed, cut, etc. to obtain the negative electrode piece.
  • cathode active material LiCoO 2 , binder PVDF, and conductive agent carbon black according to the mass ratio of 92.6:5.0:1.3:1.1, add an appropriate amount of solvent NMP, and use it in a vacuum mixer to obtain a cathode slurry; apply the cathode slurry evenly Cover the two surfaces of the positive electrode current collector aluminum foil; then dry it in a 120°C oven, cold press, cut it, etc. to obtain the positive electrode piece.
  • EC ethylene carbonate
  • EMC ethyl methyl carbonate
  • DEC diethyl carbonate
  • FEC fluoroethylene carbonate
  • concentration of LiPF 6 is 1 mol/L
  • mass percentage of fluorinated ethylene carbonate is 5% based on the total mass of the electrolyte.
  • a porous polypropylene membrane (from Celgard Company) with a thickness of 14 ⁇ m was used as the isolation membrane.
  • Electrode assembly Stack the positive electrode sheets, isolation film, and negative electrode sheets in order and wind them to obtain an electrode assembly. Put the electrode assembly into the outer packaging, add the above-mentioned electrolyte, and after processes such as packaging, standing, forming, and shaping, the secondary Battery.
  • the uncoated carbon-containing silicon-oxygen composite particles are surface-coated to obtain coated carbon-containing silicon-oxygen composite particles.
  • coated carbon-containing silicon-oxygen composite particles are the negative active material particles of Examples 7 to 15.
  • the surface coating treatment process of Examples 7 to 11 includes: placing uncoated carbon-containing silicon-oxygen composite particles in a first mixed air flow, and controlling the first mixed air flow to heat up at a heating rate of 5°C/min. to 1000°C, and after 2 hours of heat preservation, replace the first mixed air flow with the second mixed air flow, and control the second mixed air flow to heat up to 1000°C at a heating rate of 5°C/min, and keep the temperature for 2 hours.
  • the first mixed gas flow is a gas flow mixed with methane with a flow rate of 1.5L/min and argon with a flow rate of 2L/min
  • the second mixed gas flow is a mixture of propylene with a flow rate of 0.5L/min and argon with a flow rate of 2L/min.
  • the surface coating treatment process of Examples 12 and 13 includes: placing uncoated carbon-containing silicon-oxygen composite particles in a third mixed air flow, and controlling the third mixed air flow to heat up at a heating rate of 5°C/min. to T°C and keep warm for 1.5 hours.
  • the third mixed gas flow is a gas flow formed by mixing acetylene with a flow rate of 0.5L/min and argon with a flow rate of 2L/min.
  • T 800.
  • T 1000.
  • the surface coating treatment process of Example 14 includes: forming a mixed solution of uncoated carbon-containing silicon-oxygen composite particles and MeT n in the presence of an organic solvent (ethanol) and deionized water, and drying the mixture. The solution yields a powder, which is then sintered at about 250°C to 900°C for about 0.5 to 24 hours.
  • Me includes at least one of Mg, Al, Ti, Zn, Ni, Mn, V, Cr, Co or Zr
  • T includes at least one of methoxy, ethoxy, isopropoxy or halogen.
  • n is 1, 2, 3 or 4.
  • the surface coating treatment process of Example 15 includes: dispersing uncoated carbon-containing silicon-oxygen composite particles and conductive polymer in a solvent at high speed for 1 to 12 hours to obtain a suspension, and then removing the suspension in the solvent.
  • conductive polymers include polyvinylidene fluoride and its derivatives, carboxymethylcellulose and its derivatives, polyvinylpyrrolidone and its derivatives, polyvinyl alcohol and its derivatives, polyacrylic acid and its derivatives, poly One or more of styrene-butadiene rubber, polyacrylamide, polyimide, PEDOT: PSS and its derivatives, polyamide-imide, the solvent is ethanol, methanol, isopropyl alcohol or a mixture of the above substances in any proportion obtained solvent.
  • Comparative Example 1 the preparation processes of the negative electrode sheet, positive electrode sheet, electrolyte, separator and secondary battery were the same as those in Examples 1 to 6.
  • the above-mentioned silicon-oxygen composite particles are subjected to surface coating treatment to obtain negative electrode active material particles.
  • the surface coating process of Comparative Example 2 is the same as that of Examples 7 to 11; the surface coating process of Comparative Example 3 is the same as that of Example 12; the surface coating process of Comparative Example 4 is the same as that of Example 13; The surface coating treatment process of Example 5 is the same as that of Example 14; the surface coating treatment process of Comparative Example 6 is the same as that of Example 15.
  • the carbon content of the negative active material particle phase is defined as the mass percentage of the carbon element doped in the negative active material particle phase based on the total mass of the negative active material particles.
  • the surface is evenly covered with 0.8g of tungsten-tin-iron three-in-one flux; use a crucible clamp to place the crucible on the quartz crucible holder, and test it with a high-frequency infrared carbon and sulfur analyzer.
  • the test parameters are set as follows: the pre-oxygen blowing time is 20s. , the top oxygen blowing time is 50s, the oxygen blowing flow is 1.8L/min, the carbon cutoff level is 10%, the analysis time is 20-50s, and the analytical oxygen flow is 2.0L/min.
  • the radiation source of XRD test is Cu target material
  • the test parameters are set as follows: tube voltage is 40kV, tube current is 30mA, scanning speed is 8°/min, and 2 ⁇ range is 10°-80°.
  • the intensity of the highest characteristic diffraction peak of 2 ⁇ in the range of 28.3 ⁇ 0.5° is I 3
  • the intensity of the highest characteristic peak of 2 ⁇ in the range of 22.5 ⁇ 0.3° is I 4 .
  • Test instrument HORIBA LabRAM HR Evolution high-resolution Raman spectrometer
  • the negative electrode sheet is prepared into a secondary battery; in a dry room with a temperature of 21 ⁇ 5°C and a humidity of ⁇ 1.7%, after 10 charge and discharge cycles, the battery is charged to a fully charged state, and then the secondary battery is disassembled.
  • test results of the negative active material particles are detailed in Table 1, and the XRD test results of the negative electrode sheet and the secondary battery test results are detailed in Table 2.
  • Table 1 and Table 2 "/" indicates that no corresponding processing has been performed, or the corresponding parameters cannot be measured.
  • Example 1 1.0 82 10.1 Example 2 1.3 83 9.4 Example 3 1.9 84 9.3 Example 4 2.1 83 9.1 Example 5 2.4 83 8.8 Example 6 2.5 86 8.6 Example 7 1.1 85 9.3 Example 8 1.8 86 8.9 Example 9 2.7 90 8.7 Example 10 2.9 85 8.5 Example 11 3.0 84 8.4 Example 12 1.6 85 8.6 Example 13 2.0 82 9.0 Example 14 2.4 83 9.5 Example 15 2.8 84 10.3 Comparative example 1 0.3 62 20.5 Comparative example 2 0.9 59 12.1 Comparative example 3 0.7 77 19.7 Comparative example 4 0.6 72 16.4 Comparative example 5 0.5 78 15.3 Comparative example 6 0.4 70 17.1 Comparative example 7 0.5 80 10.8 Comparative example 8 3.2 64 18.0
  • the I 1 /I 2 value of the negative electrode plate satisfies 1 ⁇ I 1 /I 2 ⁇ 3, it can provide a good cycle retention rate and expansion rate for the battery. This may be due to the fact that when 1 ⁇ I 1 /I 2 ⁇ 3, the specific components in the negative electrode sheet are conducive to enhancing the mass transfer process of the electrochemical reaction, and also have a certain limiting effect on the expansion of Si crystallites.
  • doping carbon elements into the bulk phase of silicon-oxygen composite particles can not only inhibit the size growth of silicon crystallites inside the negative active material particles during the high-temperature coating process, but also inhibit the growth of the negative active material particles during the embedding process.
  • the cycle capacity retention rate of the secondary battery can be significantly improved.

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Abstract

本申请公开了一种负极极片、电化学装置及电子设备，所述负极极片包括负极集流体以及位于所述负极集流体至少一个侧的负极活性材料层，所述负极活性材料层包括含碳的硅氧复合物颗粒，其中，所述负极极片的X射线衍射图满足：1≤I 1/I 2≤3，其中，I 1为2θ＝31.9±0.5处的最高特征衍射峰的强度，I 2为2θ＝21.5±0.5处的最高特征衍射峰的强度。本申请能够降低负极活性材料层中负极活性材料颗粒的体积膨胀率、提升负极极片的活性离子传导能力，从而提升二次电池的循环容量保持率、倍率性能和循环稳定性。

Description

负极极片、电化学装置及电子设备 技术领域
本申请属于二次电池技术领域，具体涉及一种负极极片、电化学装置及电子设备。
背景技术
二次电池具有能量密度高、循环寿命长，以及无污染、无记忆效应等突出特点。作为清洁能源，二次电池的应用已由电子产品逐渐普及到电动汽车等大型装置领域，以适应环境和能源的可持续发展战略。由此，也对二次电池的能量密度提出了更高的要求。
在众多负极活性材料中，硅负极材料(Si)由于具有远高于碳材料的理论容量而备受瞩目。
然而，硅负极材料存在着严重的体积效应，在充放电过程中会产生巨大的体积収缩和膨胀，因此，在充放电过程中，硅负极材料极易发生破碎，以致无法在负极极片表面形成稳定的SEI膜。由此，硅负极材料应用于二次电池中，容易造成电解液的消耗和负极膜层的粉化，从而导致二次电池的容量衰减、降低二次电池的倍率性能和循环稳定性。
发明内容
本申请的目的在于提供一种负极极片、电化学装置及电子设备，旨在降低负极活性材料层中负极活性材料颗粒的体积膨胀率、提升负极极片的活性离子传导能力，从而提升二次电池的循环容量保持率、倍率性能和循环稳定性。
本申请第一方面提供一种负极极片，其包括负极集流体以及位于所述负极集流体至少一个侧的负极活性材料层，
所述负极活性材料层包括含碳的硅氧复合物颗粒，
其中，所述负极极片的X射线衍射图满足：1≤I 1/I 2≤3，其中，I 1为2θ＝31.9±0.5°处的最高特征衍射峰的强度，I 2为2θ＝21.5±0.5°处的最高特征衍射峰的强度。
含碳的硅氧复合物颗粒中，C原子能够在SiO x颗粒内部取代Si-O键形成Si-C和O-C键。由此，能够减少Si-O键的数量，从而减少Si-O键断裂后形成的Si-Si键的数量，进而避免Si原子富集区应力过大而导致负极材料颗粒膨胀破裂。此外，在负极极片的负极活性材料层中包括上述含碳的硅氧复合物颗粒，且负极极片的X射线衍射图满足以上条件，能够有效降低负极活性材料颗粒的体积膨胀率、提升负极极片的活性离子传导能力，从而提升二次电池的循环容量保持率、倍率性能和循环稳定性。
在本申请任意实施方式中，含碳的硅氧复合物颗粒的X射线衍射图满足：I 3/I 4≤2，其中，I 3为2θ＝28.3±0.5°处的最高特征衍射峰的强度，I 4为2θ＝22.5±0.3°处的最高特征衍射峰的强度。含碳的硅氧复合物颗粒的X射线衍射图满足上述条件时，在二次电池的充放电循环过程中，能够形成尺寸适当的硅微晶。在该硅微晶具有合适尺寸的情况下，负 极活性材料颗粒能够具有较低的体积膨胀率，由此能够降低负极活性材料颗粒膨胀破裂的风险。由此，负极极片应用于二次电池中，能够使得二次电池具备高循环容量保持率、良好的倍率性能和循环稳定性。
在本申请任意实施方式中，含碳的硅氧复合物颗粒的拉曼光谱满足：I D＞I G，其中，I D为D频带峰的强度，I G为G频带峰的强度，可选地，1.1≤I D/I G≤2.0。D频带峰的强度与G频带峰的强度满足上述条件时，可认为含碳的硅氧复合物颗粒中掺杂的碳含量在合适的范围内，且含碳的硅氧复合物颗粒能够具有合适的结构。在该合适的结构下，Si-O键、Si-C键、O-C键的比例适当，负极材料颗粒在二次电池的充放电循环过程中，能够具有更低的体积膨胀率。因此，应用该负极极片的二次电池能够具有高循环容量保持率、良好的倍率性能和循环稳定性。
在本申请任意实施方式中，在所述负极活性材料层包括含碳的硅氧复合物颗粒的任意区域中，基于碳、硅和氧的总质量，所述碳的含量为0.5％至10％。负极活性材料层中，碳、硅和氧的分布满足上述条件，能够使得Si-O键、Si-C键、O-C键的比例适当，负极材料颗粒在二次电池的充放电循环过程中，能够具有更低的体积膨胀率。因此，应用该负极极片的二次电池能够具有高循环容量保持率、良好的倍率性能和循环稳定性。
在本申请任意实施方式中，所述含碳的硅氧复合物颗粒表面的至少部分区域还包括包覆层，所述包覆层包含导电聚合物、碳材料以及氧化物MeO z中的至少一者，其中，Me为金属元素，z＝0.5至3。
在本申请任意实施方式中，所述导电聚合物包括聚偏氟乙烯及其衍生物、羧甲基纤维素及其衍生物、聚乙烯基吡咯烷酮及其衍生物、聚乙烯醇及其衍生物、聚丙烯酸及其衍生物、丁苯橡胶、聚丙烯酰胺、聚酰亚胺、PEDOT：PSS及其衍生物、聚酰胺酰亚胺中的一种或多种。
在本申请任意实施方式中，所述碳材料包括碳纤维、碳纳米管、石墨烯、石墨及无定形碳中的一种或多种。
在本申请任意实施方式中，所述Me包括Mg、Al、Ti、Zn、Ni、Mn、V、Cr、Co及Zr中的至少一者。
在本申请任意实施方式中，所述包覆层的厚度为0.1nm至10nm。可选地，所述包覆层的厚度为1nm至3nm。
在本申请任意实施方式中，所述含碳的硅氧复合物颗粒的体积平均粒径D V50为2.5μm至10μm，所述含碳的硅氧复合物颗粒的线性平均粒径D n10与所述D v50满足：0.3≤Dn 10/Dv 50≤0.6。
在本申请任意实施方式中，含碳的硅氧复合物颗粒在5000kg压力下的粉末压实密度为1.21g/cm 3至1.50g/cm 3。
本申请第二方面提供一种电化学装置，其包括本申请第一方面的负极极片。
在本申请任意实施方式中，所述电化学装置为锂离子电池。
本申请第三方面提供一种电子设备，其包括本申请第二方面的电化学装置。
附图说明
为了更清楚地说明本申请实施例的技术方案，下面将对本申请实施例中所需要使 用的附图作简单地介绍，显而易见地，下面所描述的附图仅仅是本申请的一些实施方式。
图1是本申请一实施例的负极活性材料颗粒的XRD测试图。
图2是本申请一实施例的负极活性材料颗粒截面的扫描电子显微镜图(SEM图)。
图3是按照本申请图二负极活性材料颗粒截面SEM图标示进行线性扫描得到的的元素线分布曲线。
图4是本申请一实施例的负极极片的XRD测试图。
具体实施方式
为了使本申请的发明目的、技术方案和有益技术效果更加清晰，以下结合实施例对本申请进行进一步详细说明。应当理解的是，本说明书中描述的实施例仅仅是为了解释本申请，并非为了限定本申请。
为了简便，本文仅明确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，尽管未明确记载，但是范围端点间的每个点或单个数值都包含在该范围内。因而，每个点或单个数值可以作为自身的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，需要说明的是，除非另有说明，“以上”、“以下”为包含本数，“一种或几种”中“几种”的含义是两种或两种以上。
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“约”用以描述及说明小的变化。当与事件或情形结合使用时，所述术语可指代其中事件或情形精确发生的例子以及其中事件或情形极近似地发生的例子。举例来说，当结合数值使用时，术语可指代小于或等于所述数值的±10％的变化范围，例如小于或等于±5％、小于或等于±4％、小于或等于±3％、小于或等于±2％、小于或等于±1％、小于或等于±0.5％、小于或等于±0.1％、或小于或等于±0.05％。另外，有时在本文中以范围格式呈现量、比率和其它数值。应理解，此类范围格式是用于便利及简洁起见，且应灵活地理解，不仅包含明确地指定为范围限制的数值，而且包含涵盖于所述范围内的所有个别数值或子范围，如同明确地指定每一数值及子范围一般。
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。
本申请的上述发明内容并不意欲描述本申请中的每个公开的实施方式或每种实现方式。如下描述更具体地举例说明示例性实施方式。在整篇申请中的多处，通过一系列 实施例提供了指导，这些实施例可以以各种组合形式使用。在各个实例中，列举仅作为代表性组，不应解释为穷举。
如背景技术所述，硅负极材料虽然具有高理论容量，但由于其具有严重的体积效应，应用于二次电池中易造成电解液的消耗和负极膜层的粉化，从而导致二次电池的容量衰减、降低二次电池的倍率性能和循环稳定性。
氧化亚硅(SiO x，0.8≤x≤1.2)负极材料可在首次充电嵌锂时生成硅酸锂和氧化锂等缓冲物质，从而减缓负极材料在充放电过程中的体积膨胀，因此相对于硅负极材料具有更低的体积效应。但是氧化亚硅的体积效应仍然无法满足市场对负极材料的期望。
目前，进一步减小氧化亚硅的体积效应的方法多是对氧化亚硅进行歧化处理、表面包覆或者纳米化处理。其中，歧化处理是在高温下，使部分氧化亚硅转变为石英相的SiO 2和Si纳米微晶，SiO 2覆盖于Si纳米微晶表面，作为缓冲物质以抑制Si纳米微晶在嵌锂过程中的体积膨胀。表面包覆则是利用利用金属氧化物、聚合物等对SiO x进行表面包覆处理，利用包覆层的束缚作用抵抗SiO x体积膨胀时产生的应力，从而防止颗粒破裂。这两种方法都是通过构建缓冲区域，以限制Si在嵌锂过程中的体积膨胀。但是，随着充放电循环次数的增加，缓冲区域的结构会因反复受力而产生裂痕，甚至发生坍塌，以致负极材料颗粒破碎，造成二次电池的容量损失、降低二次电池的倍率性能和循环稳定性。对SiO x进行纳米化处理能够减小SiO x本身的体积膨胀率，从而解决了负极材料在嵌锂过程中体积膨胀过大的问题。然而，经纳米化处理的SiO x由于比表面积大，相应地会消耗大量的电解液，形成较厚的SEI膜，由此对二次电池的首次库伦效率和循环性能造成负面影响。
为了解决上述问题，发明人经深入思考与实验，提供了一种负极极片，该负极极片应用于二次电池，能够使得二次电池具备高循环容量保持率和良好的电化学性能。
负极极片
发明人经深入思考与实验，提供了一种负极极片，其包括负极集流体以及位于负极集流体至少一个侧的负极活性材料层。该负极活性材料层包括含碳的硅氧复合物颗粒。其中，所述负极活性材料层的X射线衍射(XRD)图满足：1≤I 1/I 2≤3，其中，I 1为2θ＝31.9±0.5°处的最高特征衍射峰的强度，I 2为2θ＝21.5±0.5°处的最高特征衍射峰的强度。
本申请对含碳的硅氧复合物颗粒不作限定，含碳的硅氧复合物颗粒可以为体相掺杂有原子级别碳元素的氧化亚硅颗粒。在一些实施方式中，含碳的硅氧复合物颗粒可以为对SiO x进行体相碳掺杂得到的复合物颗粒。可选地，所述含碳的硅氧复合物中，碳元素的质量百分含量可以为0.5％-10％。例如，所述含碳的硅氧复合物中，碳元素的质量百分含量可以为0.5％，1％，1.5％，2％，2.5％，3％，3.5％，4％，4.5％，5％，5.5％，6％，6.5％，7％，7.5％，8％，8.5％，9％，9.5％，10％或处于以上任何数值所组成的范围内。优选的，含碳的硅氧复合物颗粒可以为SiC xO y颗粒，其中，0＜x＜0.04，0.8＜y＜1.2。
并非意在受限于任何理论或解释，发明人发现，含碳的硅氧复合物颗粒中，C原子能够在SiO x颗粒内部取代Si-O键形成Si-C和O-C键。由此，能够减少Si-O键的数量，从而减少Si-O键断裂后形成的Si-Si键的数量，进而避免Si原子富集区应力过大而导致负极材料颗粒膨胀破裂。此外，虽然机理尚不明确，发明人意外地发现，在负极极片的负极活性材料层中包括上述含碳的硅氧复合物颗粒，且负极极片的X射线衍射图满 足以上条件，能够有效降低负极活性材料颗粒的体积膨胀率、提升负极极片的活性离子传导能力，从而提升二次电池的循环容量保持率、倍率性能和循环稳定性。具体地，负极极片的X射线衍射图满足以上条件时，负极极片中能够包含特定的成分，例如包含特定比例的具有不同结构的硅酸盐。这些特定的成分不仅能够抑制硅微晶的膨胀，而且有利于增强电化学反应的传质过程，由此能够提升二次电池的循环容量保持率、倍率性能和循环稳定性。
在一些实施方式中，所述含碳的硅氧复合物颗粒的X射线衍射图可以满足：I 3/I 4≤2，例如，0≤I 3/I 4≤2，0.5≤I 3/I 4≤1.8，0.8≤I 3/I 4≤1.5或1.0≤I 3/I 4≤1.2。其中，I 3为2θ＝28.3±0.5°处的最高特征射峰的强度，I 4为2θ＝22.5±0.3°处的最高特征衍射峰的强度。
I 3/I 4数值的大小可反映含碳的硅氧复合物颗粒受到歧化的程度。I 3/I 4值越小，负极活性材料内部的硅微晶的晶粒尺寸越大。并非意在受限于任何理论或解释，含碳的硅氧复合物颗粒的X射线衍射图满足上述条件时，在二次电池的充放电循环过程中，能够形成尺寸适当的硅微晶。在该硅微晶具有合适尺寸的情况下，负极活性材料颗粒能够具有较低的体积膨胀率，由此能够降低负极活性材料颗粒膨胀破裂的风险。由此，负极极片应用于二次电池中，能够使得二次电池具备高循环容量保持率、良好的倍率性能和循环稳定性。
在一些实施方式中，所述含碳的硅氧复合物颗粒的拉曼光谱可以满足：I D＞I G，其中，I D为D频带峰的强度，I G为G频带峰的强度。可选地，所述含碳的硅氧复合物颗粒的拉曼光谱满足1.1≤I D/I G≤2.0，例如，1，1≤I D/I G≤2.0，1.3≤I D/I G≤2.0，1.5≤I D/I G≤2.0，1.7≤I D/I G≤2.0，1.9≤I D/I G≤2.0，1.1≤I D/I G≤1.8，1.3≤I D/I G≤1.8，1.5≤I D/I G≤1.8，1.7≤I D/I G≤1.8，1.1≤I D/I G≤1.6，1.3≤I D/I G≤1.6，1.5≤I D/I G≤1.6，1.1≤I D/I G≤1.4或1.3≤I D/I G≤1.4。
并非意在受限于任何理论或解释，含碳的硅氧复合物颗粒的拉曼光谱中，D频带峰的强度与G频带峰的强度满足上述条件时，可认为含碳的硅氧复合物颗粒中掺杂的碳含量在合适的范围内，且含碳的硅氧复合物颗粒能够具有合适的结构。在该合适的结构下，Si-O键、Si-C键、O-C键的比例适当，负极材料颗粒在二次电池的充放电循环过程中，能够具有更低的体积膨胀率。因此，应用该负极极片的二次电池能够具有高循环容量保持率、良好的倍率性能和循环稳定性。
在一些实施方式中，负极活性材料层包括含碳的硅氧复合物颗粒的任意区域中，基于碳、硅和氧的总质量，碳的含量可为0.5％至10％。例如，负极活性材料层包括含碳的硅氧复合物颗粒的任意区域中，基于碳、硅和氧的总质量，碳元素的质量百分含量可以为0.5％，1％，1.5％，2％，2.5％，3％，3.5％，4％，4.5％，5％，5.5％，6％，6.5％，7％，7.5％，8％，8.5％，9％，9.5％，10％或处于以上任何数值所组成的范围内。
并非意在受限于任何理论或解释，负极活性材料层中，碳、硅和氧的分布满足上述条件，能够使得Si-O键、Si-C键、O-C键的比例适当，负极材料颗粒在二次电池的充放电循环过程中，能够具有更低的体积膨胀率。因此，应用该负极极片的二次电池能够具有高循环容量保持率、良好的倍率性能和循环稳定性。
在一些实施方式中，所述含碳的硅氧复合物颗粒表面的至少部分区域还包括包覆层，所述包覆层可包含导电聚合物、碳材料以及氧化物MeO z中的至少一者，其中，Me为金属元素，z＝0.5至3。
该实施方式中，包覆层可以通过物理作用包覆在含碳的硅氧复合物颗粒表面，也可以通过化学作用包覆在含碳的硅氧复合物颗粒表面表面，在此不做限定。包覆层可以为单层结构，也可以具有多层结构。当包覆层为单层结构时，包覆层中可包括导电聚合物、碳材料以及氧化物MeO z中的一种或多种。当包覆层具有多层结构时，包覆层的每一单层中可包括导电聚合物、碳材料以及氧化物MeO z中的一种或多种。
在一些实施方式中，所述导电聚合物可包括聚偏氟乙烯(PVDF)及其衍生物、羧甲基纤维素(CMC)及其衍生物、聚乙烯基吡咯烷酮(PVP)及其衍生物、聚乙烯醇(PVA)及其衍生物、聚丙烯酸(PAA)及其衍生物、丁苯橡胶SBR、聚丙烯酰胺(PAM)、聚酰亚胺(PI)、PEDOT：PSS及其衍生物、聚酰胺酰亚胺(PAI)中的一种或多种。
在一些实施方式中，所述碳材料可包括碳纤维、碳纳米管、石墨烯、石墨及无定形碳中的一种或多种。
在一些实施方式中，所述氧化物MeO z中的Me可包括Mg、Al、Ti、Zn、Ni、Mn、V、Cr、Co及Zr中的一种或多种。可选地，Me包括Mg、Al、Ni中的一种或多种。
并非意在受限于任何理论或解释，发明人发现，上述包覆于含碳的硅氧复合物颗粒表面的包覆层，其能够与含碳的硅氧复合物颗粒表面的官能团相互作用，从而形成具有一定机械强度三维导电网络。一方面，该三维导电网络具有一定的机械强度，能够通过束缚作用抑制负极活性材料颗粒的在嵌锂过程中产生的体积膨胀；另一方面，该三维导电网络能够提升负极活性材料的导电性能，从而能够减小负极极片的表面阻抗。由此，能够在抑制负极活性材料颗粒的体积膨胀的同时，提升负极活性材料导电性能，进而能够提升二次电池的循环容量保持率、倍率性能和循环稳定性。
进一步地，含碳的硅氧复合物颗粒表面的包覆层中，导电聚合物、碳材料、氧化物MeO z选自上述合适的材料，包覆层能够具有更好的机械性能和导电性能。因此，能够进一步降低负极活性材料颗粒的体积膨胀率、提升负极活性材料颗粒的导电性能，由此提升二次电池的循环容量保持率、倍率性能和循环稳定性。
在一些实施方式中，所述包覆层的厚度可为0.1nm至10nm。在一些实施方式中，所述包覆层的厚度可为1nm至3nm。在一些实施方式中，所述包覆层的厚度可为0.5nm、0.8nm、1nm、1.2nm、1.5nm、1.8nm、2nm、2.5nm、2.8nm、3nm、3.5nm、3.8nm、4nm、4.5nm、5nm、5.5nm、6nm、6.5nm、7nm、7.5nm、8nm、8.5nm、9nm、9.5nm、10nm或者处于上述任意数值所组成的范围内。
并非意在受限于任何理论或解释，包覆层的厚度在上述范围内，能够兼具良好的机械性能和导电性能，由此能够有效抑制负极活性材料颗粒的体积膨胀、提升负极活性材料的导电性能。此外，包覆层的厚度在上述合适的范围内，还能使得负极极片具备高能量密度，由此能够提升二次电池的能量密度。
在一些实施方式中，所述含碳的硅氧复合物颗粒的体积平均粒径D V50为2.5μm至10μm，所述含碳的硅氧复合物颗粒的线性平均粒径D n10与所述D v50可满足：0.3≤Dn 10/Dv 50≤0.6。例如，Dn 10/Dv 50可以为0.3、0.35、0.4、0.45、0.5、0.55、0.6或者上述任意数值所组成的范围内。
负极活性材料的体积平均粒径D V50控制在合适的范围内，可以缩短活性离子的扩 散路径，有利于负极活性材料层形成通畅的孔隙结构。因此，负极极片能同时具有良好的液相传输性能以及良好的活性离子固相扩散性能。另外，并非意在受限于任何理论或解释，发明人意外地发现，含碳的硅氧复合物颗粒的线性平均粒径D n10与所述D v50满足以上条件时，有利于负极活性材料的容量发挥、保证二次电池具有高倍率性能和良好的循环稳定性。
在一些实施方式中，所述含碳的硅氧复合物颗粒在5000kg压力下的粉末压实密度可为1.21g/cm 3至1.50g/cm 3。具体地，所述含碳的硅氧复合物颗粒在5000kg压力下的粉末压实密度可以为1.21g/cm 3至1.48g/cm 3，1.25g/cm 3至1.45g/cm 3，1.30g/cm 3至1.42g/cm 3，1.35g/cm 3至1.40g/cm 3。在一些实施方式中，所述含碳的硅氧复合物颗粒5000kg压力下的粉末压实密度可为1.21g/cm 3、1.25g/cm 3、1.28g/cm 3、1.31g/cm 3、1.35g/cm 3、1.38g/cm 3、1.41g/cm 3、1.45g/cm 3、1.48g/cm 3、150g/cm 3或者处于上述任意数值所组成的范围内。
含碳的硅氧复合物颗在5000kg压力下的粉末压实密度在所给范围内，能使负极活性材料层中的颗粒之间紧密接触，提高单位体积内的活性材料含量，由此能提升电池的能量密度。
本申请对负极极片的负极集流体不作限定。可以使用金属箔材或多孔金属板，例如使用铜、镍、钛、铁等金属或它们的合金的箔材或多孔板。作为示例，负极集流体为铜箔。
在一些实施方式中，所述负极集流体具有在自身厚度方向上相对的两个侧，负极活性材料层可以设置在负极集流体的一侧，也可以同时设置在负极集流体的两侧。例如，负极集流体具有在其自身厚度方向相对的两侧，负极活性材料层设置在负极集流体相对的两侧中的任意一侧或两侧上。
在一些实施方式中，所述负极活性材料层中并不排除除了所述含碳的硅氧复合物颗粒外的其他负极活性材料。其他负极活性材料的具体种类不受到具体的限制，可根据需求进行选择。作为示例，其他负极活性材料包括但不限于天然石墨、人造石墨、中间相微碳球(MCMB)、硬碳，软碳、硅、硅-碳复合物、SiO、Li-Sn合金、Li-Sn-O合金、Sn、SnO、SnO 2、尖晶石结构的Li 4Ti 5O 12、Li-Al合金中的至少一种。
在一些实施方式中，所述负极活性材料层还可选地包括粘结剂。所述粘结剂可选自聚丙烯酸酯、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、羧甲基纤维素钠、羧甲基纤维素钾、羟甲基纤维素钠、羟甲基纤维素钾中的至少一种。
在一些实施方式中，负极活性材料层还可选地包括导电剂。导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，负极活性材料层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。
本申请中负极极片可以按照本领域常规方法制备。例如将所述含碳的硅氧复合物颗粒及可选的其他负极活性材料，导电剂，粘结剂和增稠剂分散于溶剂中，溶剂可以是N-甲基吡咯烷酮(NMP)或去离子水，形成均匀的负极浆料，将负极浆料涂覆在负极集流体上，经烘干、冷压等工序得到负极极片。
需要说明的是，本申请所给的各负极活性材料层参数均指单侧负极活性材料层的 参数范围。当负极活性材料层设置在负极集流体的两侧时，其中任意一侧的负极活性材料层参数满足本申请，即认为落入本申请的保护范围内。
另外，本申请中的负极极片并不排除除了负极活性材料层之外的其他附加功能层。例如，在某些实施方式中，本申请的负极极片还包括夹在负极集流体和负极活性材料层之间、设置于负极集流体表面的导电底涂层(例如由导电剂和粘结剂组成)。在另外一些实施方式中，本申请的负极极片还包括覆盖在负极活性材料层表面的保护层。在本申请中，XRD图可通过本领域已知的方法和仪器测定。例如，可以利用X’PertPro MPD X射线衍射仪进行XRD测试得到，其中，XRD测试的辐射源为Cu靶材，测试的参数可设置为：管电压为40kV，管电流为30mA，扫描速度为8°/min，2θ范围为10-80°。
在本申请中，拉曼光谱图可通过本领域已知的方法和仪器测定。例如，可以利用HORIBA LabRAM HR Evolution高分辨拉曼光谱仪进行Raman测试得到，具体地，可以以Ar离子激光器为光源测试得到。
在本申请中，负极活性负极活性材料层包括含碳的硅氧复合物颗粒的任意区域中，基于碳、硅和氧的总质量，碳的含量可通过含碳的硅氧复合物颗粒的截面元素分布测试图确定。例如，可以将含碳的硅氧复合物颗粒洒在导电胶的铜箔上，裁剪成断面，采用等离子抛光机(Leica EM TIC 3X-Ion Beam Slope Cutter)抛光。随后将铜箔放入扫描电子显微镜(SEM)中，寻找到切开的负极活性材料颗粒，采用采聚焦离子束(FIB)将上述负极活性材料颗粒沿断面的垂直方向切割，得到含有负极活性材料颗粒截面的薄片后，采用透射电子显微镜(TEM)和能谱仪(EDS)测量选定区域中碳、氧和硅中碳的比例。
在本申请中，含碳的硅氧复合物颗粒表面的包覆层的厚度具有本领域公知的含义，可采用本领域已知的方法和仪器测定。例如，可以利用扫描电子显微镜(SEM)观察样品的微观形貌(例如，颗粒团聚情况)，以表征样品表面的包覆情况，测试仪器可以为OXFORD EDS(X-max-20mm 2)，加速电压为10KV。
在本申请中，含碳的硅氧复合物颗粒的体积平均粒径D V50、含碳的硅氧复合物颗粒的线性平均粒径D n10具有本领域公知的含义，可采用本领域已知的方法和仪器测定。例如，可以参照GB/T 19077-2016粒度分布激光衍射法，采用激光粒度分析仪(例如英国马尔文Mastersizer 2000E)测定。
在本申请中，含碳的硅氧复合物颗粒在5000kg压力下的粉末压实密度具有本领域公知的含义，可以用本领域已知的方法测定。例如参照标准GB/T24533-2009，通过电子压力试验机(例如UTM7305型)测定。示例性测试方法如下：称取1g含碳的硅氧复合物颗粒，加入底面积为1.327cm 2的模具中，加压至5000kg，保压30s，然后卸压，保持10s，然后记录并计算得到负极活性材料在5000kg压力下的粉末压实密度。
需要说明的是，上述针对负极活性材料层或负极活性材料颗粒的各种参数测试，可以在电池制备过程中取样测试，也可以从制备好的二次电池中取样测试。
当上述测试样品是从制备好的二次电池中取样时，作为示例，可以按如下步骤S10-S30进行取样。
S10，将二次电池做放电处理(为了安全起见，一般使电池处于满放状态)；将电池拆卸后取出负极极片，使用碳酸二甲酯(DMC)将负极极片浸泡一定时间(例如2- 10小时)；然后将负极极片取出并在一定温度和时间下干燥处理(例如60℃，4小时)，干燥后取出负极极片。此时即可以在干燥后的负极极片中取样测试本申请上述的负极活性材料层相关的各参数。
S20，将步骤S10干燥后的负极极片在一定温度及时间下烘烤(例如400℃，2小时)，在烘烤后的负极极片中任选一区域，对负极活性材料取样(可以选用刀片刮粉取样)。
S30，将步骤S20收集到的负极活性材料做过筛处理(例如用200目的筛网过筛)最终得到可以用于测试本申请上述的各负极活性材料参数的样品。
电化学装置
本申请第二方面提供一种电化学装置，包括其中发生电化学反应以将化学能与电能互相转化的任何装置，它的具体实例包括所有种类的锂一次电池或锂二次电池。特别地，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。
在一些实施方式中，本申请的电化学装置包括正极极片、负极极片、隔离膜和电解液。
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
本申请的电化学装置还包括外包装，用于封装电极组件及电解液。在一些实施方式中，外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等，也可以是软包，例如袋式软包。软包的材质可以是塑料，如聚丙烯(PP)、聚对苯二甲酸丁二醇酯(PBT)、聚丁二酸丁二醇酯(PBS)中的至少一种。
[负极极片]
本申请的电化学装置中使用的负极极片为本申请第一方面的负极极片。
[正极极片]
本申请的电化学装置中使用的正极极片的材料、构成和其制造方法可包括任何现有技术中公知的技术。
正极极片包括正极集流体以及设置在正极集流体至少一个表面上且包括正极活性材料的正极活性物质层。作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极活性物质层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，正极活性物质层包括正极活性材料，正极活性材料的具体种类不受到具体的限制，可根据需求进行选择。例如，正极活性材料可以包括锂过渡金属氧化物、橄榄石结构的含锂磷酸盐及其各自的改性化合物中的一种或几种。在本申请的电化学装置中，上述各正极活性材料的改性化合物可以是对正极活性材料进行掺杂改性、表面包覆改性、或掺杂同时表面包覆改性。
作为示例，锂过渡金属氧化物可以包括锂钴氧化物、锂镍氧化物、锂锰氧化物、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物、锂镍钴铝氧化物及其改性化合物中的一种或几种。作为示例，橄榄石结构的含锂磷酸盐可以包括磷酸铁锂、磷酸铁锂与碳的复合材料、磷酸锰锂、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料及其改性化合物中的一种或几种。这些正极活性材料可以仅单独使 用一种，也可以将两种以上组合使用。
在一些实施方式中，正极活性物质层还可选的包括导电剂。作为示例，所述导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，正极活性物质层还可选的包括粘结剂。作为示例，所述粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。
在一些实施方式中，正极集流体可采用金属箔片或复合集流体。作为金属箔片的示例，正极集流体可采用铝箔。复合集流体可包括高分子材料基层以及形成于高分子材料基层至少一个表面上的金属材料层。作为示例，金属材料可选自铝、铝合金、镍、镍合金、钛、钛合金、银、银合金中的一种或几种。作为示例，高分子材料基层可选自聚丙烯、聚对苯二甲酸乙二醇酯、聚对苯二甲酸丁二醇酯、聚苯乙烯、聚乙烯等。
本申请中正极极片可以按照本领域常规方法制备。例如，正极活性物质层通常是将正极浆料涂布在正极集流体上，经干燥、冷压而成的。正极浆料通常是将正极活性材料、可选的导电剂、可选的粘结剂以及任意的其他组分分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)，但不限于此。
本申请的正极极片并不排除除了正极活性物质层之外的其他附加功能层。例如，在一些实施方式中，本申请的正极极片还包括夹在正极集流体和正极活性物质层之间、设置于正极集流体表面的导电底涂层(例如由导电剂和粘结剂组成)。在另外一些实施方式中，本申请的正极极片还包括覆盖在正极活性物质层表面的保护层。
[电解液]
电解液在正极极片和负极极片之间起到传导活性离子的作用。可用于本申请电化学装置的电解液可以为现有技术已知的电解液。
在一些实施方式中，所述电解液包括有机溶剂、锂盐和可选的添加剂，有机溶剂、锂盐和添加剂的种类均不受到具体的限制，可根据需求进行选择。
在一些实施方式中，作为示例，所述锂盐包括但不限于LiPF 6(六氟磷酸锂)、LiBF 4(四氟硼酸锂)、LiClO 4(高氯酸锂)、LiFSI(双氟磺酰亚胺锂)、LiTFSI(双三氟甲磺酰亚胺锂)、LiTFS(三氟甲磺酸锂)、LiDFOB(二氟草酸硼酸锂)、LiBOB(二草酸硼酸锂)、LiPO 2F 2(二氟磷酸锂)、LiDFOP(二氟二草酸磷酸锂)及LiTFOP(四氟草酸磷酸锂)中的至少一种。上述锂盐可以单独使用一种，也可以同时使用两种或两种以上。
在一些实施方式中，作为示例，所述有机溶剂包括但不限于碳酸亚乙酯(EC)、碳酸亚丙酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸亚丁酯(BC)、氟代碳酸亚乙酯(FEC)、甲酸甲酯(MF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸甲酯(MB)、丁酸乙酯(EB)、1，4-丁内酯(GBL)、环丁砜(SF)、二甲砜(MSM)、甲乙砜(EMS)及二乙砜(ESE)中的至少一种。上述有机溶剂可以单独使用一种，也可以 同时使用两种或两种以上。可选地，上述有机溶剂同时使用两种或两种以上。
在一些实施方式中，所述添加剂可以包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
作为示例，所述添加剂包括但不限于氟代碳酸乙烯酯(FEC)、碳酸亚乙烯酯(VC)、乙烯基碳酸乙烯酯(VEC)、硫酸乙烯酯(DTD)、硫酸丙烯酯、亚硫酸乙烯酯(ES)、1，3-丙磺酸内酯(PS)、1，3-丙烯磺酸内酯(PST)、磺酸酯环状季铵盐、丁二酸酐、丁二腈(SN)、己二腈(AND)、三(三甲基硅烷)磷酸酯(TMSP)、三(三甲基硅烷)硼酸酯(TMSB)中的至少一种。
电解液可以按照本领域常规的方法制备。例如，可以将有机溶剂、锂盐、可选的添加剂混合均匀，得到电解液。各物料的添加顺序并没有特别的限制，例如，将锂盐、可选的添加剂加入到有机溶剂中混合均匀，得到电解液；或者，先将锂盐加入有机溶剂中，然后再将可选的添加剂加入有机溶剂中混合均匀，得到电解液。
[隔离膜]
隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使活性离子通过。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施方式中，隔离膜的材质可以选自玻璃纤维、无纺布、聚乙烯、聚丙烯、聚偏氟乙烯中的一种或几种，但不仅限于这些。隔离膜可以是单层薄膜，也可以是多层复合薄膜。隔离膜为多层复合薄膜时，各层的材料相同或不同。在一些实施方式中，隔离膜上还可以设置陶瓷涂层、金属氧化物涂层。
电子设备
本申请第三方面提供了一种电子设备，其包括本申请第二方面的电化学装置。
本申请的电子设备没有特别限定，其可以是用于现有技术中已知的任何电子设备。在一些实施方式中，电子设备可以包括但不限于，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。
实施例
下述实施例更具体地描述了本发明公开的内容，这些实施例仅仅用于阐述性说明，因为在本发明公开内容的范围内进行各种修改和变化对本领域技术人员来说是明显的。除非另有声明，以下实施例中所报道的所有份、百分比、和比值都是基于质量计，而且实施例中使用的所有试剂都可商购获得或是按照常规方法进行合成获得，并且可直接使用而无需进一步处理，以及实施例中使用的仪器均可商购获得。
实施例1至6
负极活性材料颗粒的制备
将15kg SiO 2、7kg Si混合均匀后于置于流速为v 1L/min的乙炔气流中，控制反应 体系以5℃/min的升温速率升温至1300℃，保温5h，得到含碳的硅氧复合物颗粒。
上述含碳的硅氧复合物颗粒即为实施例1至6的负极活性材料颗粒。
实施例1至6中乙炔气流的流速v 1如表1所示。
负极极片的制备
将负极活性材料颗粒与石墨按照质量比15.5∶84.5均匀混合后，得到混合负极活性材料。将所述混合负极活性材料与粘结剂聚丙烯酸(PAA)、导电剂炭黑按照质量比95.9∶2.8∶1.3进行混合，加入适量的溶剂去离子水，在真空搅拌机作用下获得负极浆料；将负极浆料均匀涂覆在负极集流体铜箔的两个表面上；然后经过120℃烘箱干燥、冷压、分切等，得到负极极片。
正极极片的制备
将正极活性材料LiCoO 2、粘结剂PVDF、导电剂炭黑按照质量比92.6∶5.0∶1.3∶1.1进行混合，加入适量的溶剂NMP，在真空搅拌机作用获得正极浆料；将正极浆料均匀涂覆在正极集流体铝箔的两个表面上；然后经120℃烘箱干燥、冷压、分切等，得到正极极片。
电解液的制备
将碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)及碳酸二乙酯(DEC)按照体积比为1∶1∶1进行混合，得到有机溶剂；将LiPF 6溶解在上述有机溶剂中，再加入氟代碳酸乙烯酯(FEC)混合均匀，得到电解液。其中，LiPF 6的浓度为1mol/L，基于电解液的总质量，氟代碳酸乙烯酯的质量百分含量为5％。
隔离膜的制备
采用厚度为14μm的多孔聚丙烯膜(来自Celgard公司)作为隔离膜。
二次电池的制备
将正极极片、隔离膜、负极极片按顺序堆叠并卷绕得到电极组件，将电极组件放入外包装中，加入上述电解液，经封装、静置化成、整形等工序后，得到二次电池。
实施例7至15
负极活性材料颗粒的制备
将15kg SiO 2、7kg Si混合均匀后于置于流速为v 1L/min的乙炔气流中，控制反应体系以5℃/min的升温速率升温至1300℃，保温5h，降温后得到未包覆的含碳的硅氧复合物颗粒；
对未包覆的含碳的硅氧复合物颗粒进行表面包覆处理，得到包覆后的含碳的硅氧复合颗粒。
上述包覆后的含碳的硅氧复合物颗粒即为实施例7至15的负极活性材料颗粒。
其中，实施例7至11的表面包覆处理过程包括：将未包覆的含碳的硅氧复合物颗粒放置在第一混合气流中，控制第一混合气流以5℃/min的升温速率升温至1000℃，保温2小时后，将第一混合气流更换为第二混合气流，控制第二混合气流以5℃/min的升温速率升温至1000℃，保温2小时。其中，第一混合气流为流速为1.5L/min的甲烷与流速为2L/min的氩气混合而成的气流，第二混合气流为流速为0.5L/min的丙烯与流速为2L/min的氩气混合而成的气流。
其中，实施例12、13的表面包覆处理过程包括：将未包覆的含碳的硅氧复合物颗 粒放置在第三混合气流中，控制第三混合气流以5℃/min的升温速率升温至T℃，保温1.5小时。其中，第三混合气流为流速为0.5L/min的乙炔与流速为2L/min的氩气混合而成的气流。实施例12中，T＝800。实施例13中，T＝1000。
其中，实施例14的表面包覆处理过程包括：将未包覆的含碳的硅氧复合物颗粒与MeT n在有机溶剂(乙醇)和去离子水的存在下形成混合溶液，干燥所述混合溶液得到粉末，然后将粉末在约250℃至900℃下烧结约0.5至24小时。其中，Me包括Mg、Al、Ti、Zn、Ni、Mn、V、Cr、Co或Zr中的至少一种，T包括甲氧基、乙氧基、异丙氧基或卤素中的至少一种，n为1、2、3或4。
其中，实施例15的表面包覆处理过程包括：将未包覆的含碳的硅氧复合物颗粒和导电聚合物在溶剂中高速分散1至12小时，得到悬浮液，然后去除所述悬浮液中的溶剂。其中，导电聚合物包括聚偏氟乙烯及其衍生物、羧甲基纤维素及其衍生物、聚乙烯基吡咯烷酮及其衍生物、聚乙烯醇及其衍生物、聚丙烯酸及其衍生物、聚丁苯橡胶、聚丙烯酰胺、聚酰亚胺、PEDOT：PSS及其衍生物、聚酰胺酰亚胺中的一种或多种，溶剂为乙醇、甲醇、异丙醇或者上述物质以任意比例混合得到的溶剂。
实施例7至15中乙炔气流的流速v 1如表1所示。
实施例7至15中负极极片、正极极片、电解液、隔离膜与二次电池的制备过程与实施例1至6相同。
对比例1
负极活性材料颗粒的制备
将15kg SiO 2、7kg Si混合均匀后于真空环境中，控制反应体系以5℃/min的升温速率升温至1300℃，保温5h，得到对比例1的负极活性材料颗粒。
对比例1中负极极片、正极极片、电解液、隔离膜与二次电池的制备过程与实施例1至6相同。
对比例2至6
负极活性材料颗粒的制备
将15kg SiO 2、7kg Si混合均匀后于氩气气流中，控制反应体系以5℃/min的升温速率升温至1300℃，保温5h，得到硅氧复合物颗粒；
对上述硅氧复合物颗粒进行表面包覆处理，得到负极活性材料颗粒。
其中，对比例2的表面包覆处理过程与实施例7至11相同；对比例3的表面包覆处理过程与实施例12相同；对比例4的表面包覆处理过程与实施例13相同；对比例5的表面包覆处理过程与实施例14相同；对比例6的表面包覆处理过程与实施例15相同。
对比例2至6中负极极片、正极极片、电解液、隔离膜与二次电池的制备过程与实施例1至6相同。
对比例7
基于实施例7至11中负极活性材料颗粒的制备过程，以及实施例1至6中的负极极片、正极极片、电解液、隔离膜与二次电池的制备过程，根据表1中所示调整乙炔气流的流速v 1，制备对比例7的负极活性材料颗粒、负极极片、正极极片、电解液、隔离膜与二次电池。
对比例8
基于实施例1至6中负极活性材料颗粒、负极极片、正极极片、电解液、隔离膜与二次电池的制备过程，根据表1中所示调整乙炔气流的流速v 1，制备对比例8的负极活性材料颗粒、负极极片、正极极片、电解液、隔离膜与二次电池。
测试部分
负极活性材料颗粒的测试
(1)负极活性材料颗粒体相碳含量测试
负极活性材料颗粒体相碳含量定义为基于负极活性材料颗粒的总质量计，负极活性材料颗粒体相中掺杂的碳元素的质量百分含量。
测试仪器：DK-606碳硫分析仪
在坩埚底部加入0.8g钨锡铁三合一助熔剂，使其均匀覆盖坩埚底部；加入0.5g负极活性材料粉末，所述负极活性材料粉末由负极活性材料颗粒研磨得到；在所述负极活性材料粉末表面均匀覆盖0.8g钨锡铁三合一助熔剂；用坩埚夹将坩埚放在石英坩埚托上，用高频红外碳硫分析仪进行测试，其中，测试的参数设置为：预吹氧时间为20s，顶吹氧时间为50s，吹氧流量为1.8L/min，碳截止电平为10％，分析时间为20-50s，分析氧流量为2.0L/min。
(2)负极活性材料颗粒的XRD测试
测试仪器：X’Pert Pro MPD X射线衍射仪
将适量负极活性材料粉末装入样品架的凹槽中，用角匙将负极活性材料粉末摊平后用载玻片轻压样品表面，使粉末表面与样品架表面的高度保持一致，进行XRD测试。其中，XRD测试的辐射源为Cu靶材，测试的参数设置为：管电压为40kV，管电流为30mA，扫描速度为8°/min，2θ范围为10°-80°。所得XRD图中，2θ在28.3±0.5°范围内的最高特征衍射峰的强度为I 3，2θ在22.5±0.3°范围内的最高特征峰的强度为I 4。
(3)负极活性材料颗粒的Raman测试
测试仪器：HORIBA LabRAM HR Evolution高分辨拉曼光谱仪
将少量负极活性材料粉末置于载玻片上，用载玻片将粉末轻轻压平后，进行Raman测试，其中，以Ar离子激光器为光源，激发波长为532nm。所得Raman图中位移在1300cm -1和1580cm -1附近的峰强度分别为I D和I G。
(4)负极活性材料颗粒的截面元素分布测试
测试仪器：Leica EM TIC 3X-Ion Beam Slope Cutter、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、能谱仪(EDS)。
将负极活性材料颗粒颗粒洒在导电胶的铜箔上，裁剪成断面，采用等离子抛光机(Leica EM TIC 3X-Ion Beam Slope Cutter)抛光。随后将铜箔放入扫描电子显微镜(SEM)中寻找到切开的负极活性材料颗粒，采用采聚焦离子束(FIB)将上述负极活性材料颗粒沿断面的垂直方向切割，得到含有负极活性材料颗粒截面的薄片后，采用透射电子显微镜(TEM)和能谱仪(EDS)测量选定区域中碳、氧和硅中碳的比例。
负极极片的XRD测试
测试仪器：X’Pert Pro MPD X射线衍射仪
将负极极片制备成二次电池；在温度为21±5℃，湿度≤1.7％的干燥房内，进行10次充放电循环后，将电池充电至满充状态后，对二次电池进行拆解，取出负极极片；将 负极极片于碳酸二甲酯中浸泡1h后取出并烘干；将烘干后的负极极片裁成长宽均为0.5cm的方形试片，并在所述方形试片的两个侧贴上透明胶，以隔绝空气；对方形试片进行XRD测试，其中，测试辐射源为Cu靶材，测试的参数设置为：管电压为40kV，管电流为30mA，扫描速度为8°/min，2θ范围为10°-80°。所得XRD测试图中，2θ在31.9±0.5°范围内的最高特征衍射峰的强度为I 1，2θ在21.5±0.5°范围内的最高特征峰的强度为I 2。
二次电池的测试
(1)二次电池的循环容量保持率测试
25℃下，将二次电池以0.7C恒流充电到4.48V，恒压充电到0.025C，静置5分钟后以0.5C放电到3.0V，此为一个循环充放电过程，记录此时的放电容量，即为第1圈放电容量，此为一个循环充放电过程，记录此时的放电容量，即为初始容量。将二次电池按照上述方法进行循环充放电测试，记录每一循环后的放电容量，并以每一循环的放电容量与初始容量做比值，得到二次电池的循环容量保持率测试图。
(2)二次电池满充膨胀率测试
用螺旋测微器测量制备好的二次电池的厚度，记为D 1。25℃下，将二次电池进行以下循环：以0.7C恒流充电到4.48V，恒压充电到0.025C，静置5分钟后以0.5C放电到3.0V。循环n次后、二次电池处于满充状态的情况下，用螺旋测微计测试此时二次电池的厚度，记为D n。二次电池满充膨胀率P n＝[(D n-D 1)/D 1]×100％。二次电池循环500次的满充膨胀率P 500＝[(D 500-D 1)/D 1]×100％。
以二次电池的循环次数为横坐标、满充膨胀率为纵坐标，记录二次电池在不同循环次数下对应的满充膨胀率，得到二次电池的满充膨胀率测试图。
负极活性材料颗粒的测试结果详见表1，负极极片的XRD测试结果以及二次电池的测试结果详见表2。表1及表2中，“/”表示未进行相应的处理，或相应的参数无法测得。
表1
序号 v 1 体相碳含量/％ I 3/I 4 I D/I G
实施例1 0.5 1.2 1.8 /
实施例2 1.0 2.6 1.5 /
实施例3 1.5 5.5 1.4 /
实施例4 2.0 7.1 1.7 /
实施例5 2.5 9.4 1.4 /
实施例6 3.0 10.8 1.1 /
实施例7 1.0 1.2 2.3 1.5
实施例8 1.5 2.6 2.1 1.6
实施例9 2.0 5.5 1.3 1.5
实施例10 2.5 7.1 1.2 1.5
实施例11 3.0 9.4 0.9 1.6
实施例12 1.5 2.6 2.0 1.5
实施例13 1.5 2.6 2.1 1.3
实施例14 1.5 2.6 1.9 /
实施例15 1.5 2.6 1.7 /
对比例1 / 0 3.6 /
对比例2 / 0 2.6 1.5
对比例3 / 0 2.5 0.9
对比例4 / 0 2.6 1.1
对比例5 / 0 2.7 /
对比例6 / 0 2.6 /
对比例7 0.5 0.9 2.4 1.4
对比例8 / 0 3.1 /
表2
序号 I 1/I 2 500次循环容量保持率/％ P 500/％
实施例1 1.0 82 10.1
实施例2 1.3 83 9.4
实施例3 1.9 84 9.3
实施例4 2.1 83 9.1
实施例5 2.4 83 8.8
实施例6 2.5 86 8.6
实施例7 1.1 85 9.3
实施例8 1.8 86 8.9
实施例9 2.7 90 8.7
实施例10 2.9 85 8.5
实施例11 3.0 84 8.4
实施例12 1.6 85 8.6
实施例13 2.0 82 9.0
实施例14 2.4 83 9.5
实施例15 2.8 84 10.3
对比例1 0.3 62 20.5
对比例2 0.9 59 12.1
对比例3 0.7 77 19.7
对比例4 0.6 72 16.4
对比例5 0.5 78 15.3
对比例6 0.4 70 17.1
对比例7 0.5 80 10.8
对比例8 3.2 64 18.0
负极极片的I 1/I 2值满足1≤I 1/I 2≤3时，能够为电池提供良好的循环保持率及膨胀率。这可能是由于1≤I 1/I 2≤3时，负极极片中的特定成分有利于增强电化学反应的传质过程，对Si微晶的膨胀也有一定的限制作用。
对比实施例12和13的测试结果可知，降低包覆温度条件，负极活性材料颗粒的I 3/I 4值减小，这可能意味着颗粒内部形成的硅微晶具有更小的尺寸，从而能够进一步减弱负极活性材料在嵌锂和脱锂过程中的体积膨胀，进而提升二次电池的循环稳定性。
通过实施例1至6与对比例1的对比、实施例7至15与对比例2至6的对比，可知：若不在硅氧复合物颗粒的体相中掺杂碳元素，硅氧复合物颗粒会具有更大的I 3/I 4值。这说明硅微晶在高温包覆条件下尺寸增大明显，且硅微晶在循环过程中也会逐渐长大，从而引起负极活性材料颗粒的明显膨胀，甚至导致颗粒破碎，因此会导致二次电池的体积膨胀和循环性能恶化。在硅氧复合物颗粒内部掺杂碳元素，能够有效抑制硅微晶的尺寸增长，从而降低二次电池的体积膨胀、提升二次电池的循环稳定性。
综上所述，在硅氧复合物颗粒的体相中掺杂碳元素，不仅能够抑制高温包覆过程中负极活性材料颗粒内部硅微晶的尺寸增长，而且还会抑制负极活性材料颗粒在嵌锂时的体积膨胀程度，并增加电化学反应过程中的传质过程。此外，控制负极极片的XRD测试图中I 1/I 2的值在本申请的范围内，二次电池的循环容量保持率能够得到显著的提升。
以上所述，仅为本申请的具体实施方式，但本申请的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本申请揭露的技术范围内，可轻易想到各种等效的修改或替换，这些修改或替换都应涵盖在本申请的保护范围之内。因此，本申请的保护范围应以权利要求的保护范围为准。

Claims (10)

  1. 一种负极极片，包括负极集流体以及位于所述负极集流体至少一个侧的负极活性材料层，
    所述负极活性材料层包括含碳的硅氧复合物颗粒，
    其中，所述负极极片的X射线衍射图满足：1≤I 1/I 2≤3，其中，I 1为2θ＝31.9±0.5°处的最高特征衍射峰的强度，I 2为2θ＝21.5±0.5°处的最高特征衍射峰的强度。
  2. 根据权利要求1所述的负极极片，其中，所述含碳的硅氧复合物颗粒的X射线衍射图满足：I 3/I 4≤2，其中，I 3为2θ＝28.3±0.5°处的最高特征衍射峰的强度，I 4为2θ＝22.5±0.3°处的最高特征衍射峰的强度。
  3. 根据权利要求1所述的负极极片，其中，所述含碳的硅氧复合物颗粒的拉曼光谱满足：I D＞I G，其中，I D为D频带峰的强度，I G为G频带峰的强度，可选地，1.1≤I D/I G≤2.0。
  4. 根据权利要求1所述的负极极片，其中，在所述负极活性材料层包括含碳的硅氧复合物颗粒的任意区域中，基于碳、硅和氧的总质量，所述碳的含量为0.5％至10％。
  5. 根据权利要求1-4任一项所述的负极极片，其中，所述含碳的硅氧复合物颗粒表面的至少部分区域还包括包覆层，所述包覆层包含导电聚合物、碳材料以及氧化物MeO z中的至少一者，其中，Me为金属元素，z＝0.5至3；
    所述负极极片满足如下至少一者：
    (1)所述导电聚合物包括聚偏氟乙烯及其衍生物、羧甲基纤维素及其衍生物、聚乙烯基吡咯烷酮及其衍生物、聚乙烯醇及其衍生物、聚丙烯酸及其衍生物、丁苯橡胶、聚丙烯酰胺、聚酰亚胺、PEDOT：PSS及其衍生物、聚酰胺酰亚胺中的一种或多种；
    (2)所述碳材料包括碳纤维、碳纳米管、石墨烯、石墨及无定形碳中的一种或多种；
    (3)Me包括Mg、Al、Ti、Zn、Ni、Mn、V、Cr、Co及Zr中的至少一者。
  6. 根据权利要求5所述的负极极片，其中，所述包覆层的厚度为0.1nm至10nm，可选地为1nm至3nm。
  7. 根据权利要求1-4任一项所述的负极极片，其中，所述含碳的硅氧复合物颗粒的体积平均粒径D v50为2.5μm至10μm，所述含碳的硅氧复合物颗粒的线性平均粒径D n10与所述D v50满足：0.3≤Dn 10/Dv 50≤0.6。
  8. 根据权利要求1-4任一项所述的负极极片，其中，所述含碳的硅氧复合物颗粒在5000kg压力下的粉末压实密度为1.21g/cm 3至1.50g/cm 3。
  9. 一种电化学装置，包括根据权利要求1-8任一项所述的负极极片。
  10. 根据权利要求9所述的电化学装置，其为锂离子电池。
PCT/CN2022/083535 2022-03-29 2022-03-29 负极极片、电化学装置及电子设备 Ceased WO2023184127A1 (zh)

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