WO2023193562A1 - 负极片及锂离子电池 - Google Patents

负极片及锂离子电池 Download PDF

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Publication number
WO2023193562A1
WO2023193562A1 PCT/CN2023/080005 CN2023080005W WO2023193562A1 WO 2023193562 A1 WO2023193562 A1 WO 2023193562A1 CN 2023080005 W CN2023080005 W CN 2023080005W WO 2023193562 A1 WO2023193562 A1 WO 2023193562A1
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Prior art keywords
negative electrode
lithium
film layer
particles
electrode film
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PCT/CN2023/080005
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English (en)
French (fr)
Inventor
张保海
彭冲
李俊义
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珠海冠宇电池股份有限公司
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Priority to EP23784126.7A priority Critical patent/EP4428975A1/en
Publication of WO2023193562A1 publication Critical patent/WO2023193562A1/zh
Priority to US18/740,175 priority patent/US20240332514A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—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
    • 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
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • 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
    • 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
    • H01M4/626—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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present disclosure relates to the field of battery technology, and in particular, to a negative electrode sheet and a lithium-ion battery.
  • a lithium-ion battery includes a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte.
  • the negative electrode sheet includes a metal sheet and a functional layer covering the metal sheet.
  • the functional layer is formed by a mixture of graphite particles and silicon particles.
  • Embodiments of the present disclosure provide a negative electrode sheet, a lithium-ion battery and a preparation method of the negative electrode sheet to solve the technical problem of reduced lithium-ion fast charging capability in related technologies.
  • a negative electrode sheet including:
  • a first negative electrode film layer is attached to the surface of the negative electrode current collector; and the active material of the first negative electrode film layer includes silicon particles and hard carbon particles; and the first negative electrode film layer includes a lithium replenishing agent;
  • a second negative electrode film layer is attached to the surface of the first negative electrode film layer; and the active material of the second negative electrode film layer includes graphite particles.
  • the beneficial effects of the embodiments of the present disclosure are: by sequentially arranging the third A negative electrode film layer and a second negative electrode film layer, that is, the first negative electrode film layer is attached to the surface of the negative electrode current collector, the second negative electrode film layer is attached to the surface of the first negative electrode film layer, and the activity of the first negative electrode film layer
  • the material includes silicon particles and hard carbon particles.
  • the active material of the second negative electrode film layer includes graphite particles, that is, the negative electrode film layer is divided into two layers.
  • the active material of the negative electrode film layer close to the negative electrode current collector includes silicon particles and hard carbon particles.
  • the active material of another negative electrode film layer away from the negative electrode current collector includes graphite particles, so that when lithium ions move to the negative electrode sheet, some lithium ions are first embedded in the graphite particles in the second negative electrode film layer, and the remaining lithium Ions are embedded in the first negative electrode film layer. Since some lithium ions are first embedded in the second negative electrode film layer, the concentration of lithium ions moving to the first negative electrode film layer is reduced and the speed becomes slow, so that the lithium ions have enough time to be embedded. In silicon particles and hard carbon particles, it reduces the aggregation of lithium ions at silicon particles and nearby hard carbon particles, thereby alleviating the phenomenon of uneven distribution of lithium ion concentration, that is, reducing the precipitation of lithium and improving the stability of lithium ions.
  • the lithium replenishing agent includes metallic lithium powder and/or lithium peroxide.
  • the particle size of the hard carbon particles is smaller than the particle size of the silicon particles, and the outer walls of the silicon particles are coated by the hard carbon particles.
  • the D50 particle diameter of the silicon particles in the first negative electrode film layer is 6 ⁇ m-10 ⁇ m, and the D90 particle diameter is 18 ⁇ m-22 ⁇ m.
  • the hard carbon particles are spherical particles, and the particle size of the hard carbon particles is 0.5 ⁇ m-2 ⁇ m.
  • the D10 particle diameter of the graphite particles in the second negative electrode film layer is 3 ⁇ m-6 ⁇ m
  • the D50 particle diameter is 11 ⁇ m-14 ⁇ m
  • the D90 particle diameter is 22 ⁇ m ⁇ D90 ⁇ 29 ⁇ m.
  • the ratio of the D90 particle size of the graphite particles to the D90 particle size of the silicon particles is 1.0-1.5.
  • the ratio of the thickness of the first negative electrode film layer to the thickness of the second negative electrode film layer is 1:9-9:1.
  • the mass ratio between the lithium replenishing agent and the silicon particles is 1% to 30%.
  • a lithium-ion battery includes a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte.
  • the negative electrode sheet is the negative electrode sheet described in any one of the above.
  • Figure 1 is a schematic diagram of a first negative electrode film layer and a second negative electrode film layer in a negative electrode sheet provided by an embodiment of the present disclosure
  • Figure 2 is a schematic structural diagram of hard carbon particles, silicon particles, mixed materials and graphite particles provided by an embodiment of the present disclosure
  • FIG. 3 is a flow chart of a method for preparing a negative electrode sheet according to an embodiment of the present disclosure.
  • Negative current collector 100.
  • First negative electrode film layer 210.
  • Hard carbon particles 220.
  • Silicon particles 230.
  • Mixed material 300.
  • Second negative electrode film layer 310. Graphite particles.
  • lithium-ion batteries have become the power source for various devices. People's performance requirements for lithium-ion batteries have also been further improved. The requirement for lithium-ion batteries to have a longer life is an important indicator of lithium-ion batteries.
  • a lithium-ion battery includes a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte; the negative electrode sheet includes a metal sheet and a functional layer covering the metal sheet.
  • this functional layer is made of a mixture of graphite and silicon. Because the lithium storage capacity of silicon is much greater than that of graphite, it can increase the energy density of lithium-ion batteries, thereby improving the battery life and life of lithium-ion batteries. .
  • a negative electrode sheet which includes a negative electrode current collector, and a first negative electrode film layer and a second negative electrode film layer are sequentially provided on the surface of the negative electrode current collector, that is, the first negative electrode film layer is attached to On the surface of the negative electrode current collector, the second negative electrode film layer is attached to the surface of the first negative electrode film layer, and the active material of the first negative electrode film layer includes silicon particles and hard carbon particles, and the second negative electrode film layer
  • the active material includes graphite particles, that is, the negative electrode film layer is divided into two layers.
  • the active material of the negative electrode film layer close to the negative electrode current collector includes a mixture of silicon particles and hard carbon particles, and the active material of the other negative electrode film layer away from the negative electrode current collector is Graphite particles are included, so that when lithium ions move to the negative electrode sheet, some lithium ions are first embedded in the graphite particles in the second negative electrode film layer, and the remaining lithium ions are embedded in the first negative electrode film layer. Since some lithium ions are embedded first In the second negative electrode film layer, the concentration of lithium ions moving to the first negative electrode film layer is reduced and the speed is slowed down, so that the lithium ions have enough time to be embedded in the silicon particles and hard carbon particles, thereby reducing the concentration of lithium ions in the silicon particles.
  • the aggregation density at the particles and nearby hard carbon particles reduces the uneven distribution of lithium ion concentration, that is, reduces the precipitation of lithium and improves the endurance of lithium-ion batteries.
  • the dynamic performance of hard carbon particles is significantly better than that of silicon particles and graphite particles, the mixed use of silicon particles and hard carbon particles can effectively improve the dynamic performance of lithium-ion batteries, thus improving the efficiency of lithium-ion batteries.
  • the charging speed solves the technical problem of reduced fast charging capability of lithium-ion batteries in related technologies.
  • embodiments of the present disclosure provide a negative electrode sheet, including a negative electrode current collector 100, a first negative electrode film layer 200 attached to the surface of the negative electrode current collector 100; and an active material of the first negative electrode film layer 200 It includes silicon particles 220 and hard carbon particles 210; the second negative electrode film layer 300 is attached to the surface of the first negative electrode film layer 200; and the active material of the second negative electrode film layer 300 includes graphite particles 310.
  • the negative electrode current collector 100 can be a copper foil, which mainly plays a conductive role and serves as a carrier of the negative electrode film layer, and the thickness of the copper foil can be 4-15 ⁇ m, for example, the thickness of the copper foil can be 4 ⁇ m, 7 ⁇ m, 11 ⁇ m or 15 ⁇ m.
  • the copper foil may be one of a homogeneous copper foil, a porous copper foil or a copper foil with a carbon coating layer.
  • the first negative electrode film layer 200 may be a film layer obtained by coating the first negative electrode film layer 200 slurry on the surface of the negative electrode current collector 100 and drying it.
  • the slurry of the first negative electrode film layer 200 may include NMP (1-methyl 2-pyrrolidone) solvent, that is, the silicon particles 220 and the hard carbon particles 210 are mixed uniformly through the NMP solvent to form a slurry, and the slurry is applied to on copper foil,
  • NMP (1-methyl 2-pyrrolidone) solvent that is, the silicon particles 220 and the hard carbon particles 210 are mixed uniformly through the NMP solvent to form a slurry, and the slurry is applied to on copper foil,
  • the first negative electrode film layer 200 having an active material mixed with silicon particles 220 and hard carbon particles 210 is formed.
  • the second negative electrode film layer 300 can be coated on the surface of the first negative electrode film layer 200 through the second negative electrode film layer 300 slurry, and the film layer can be obtained by drying.
  • the slurry of the second negative electrode film layer 300 may include an NMP solvent, that is, the graphite particles 310 are mixed into a slurry through the NMP solvent, and the slurry is applied on the copper foil, thereby forming a third active material having the graphite particles 310 .
  • the hard carbon particles 210 refer to carbon that is difficult to be graphitized and are thermal decomposition products of high molecular polymers.
  • the graphite particles 310 may include one or more of artificial graphite, natural graphite, mesophase carbon microspheres, soft carbon, hard carbon, and organic polymer compound carbon; the silicon particles 220 may include silicon oxide materials, One or more of silicon carbide materials and nano-silicon materials.
  • the negative electrode sheet provided in this embodiment is divided into two layers by dividing the negative electrode film layer.
  • the active material of the negative electrode film layer close to the negative electrode current collector 100 includes a mixture of silicon particles 220 and hard carbon particles 210 , and the other layer is far away from the negative electrode current collector 100 .
  • the active material of the negative electrode film layer 100 includes graphite particles 310, so that when lithium ions move to the negative electrode sheet, some lithium ions are first embedded in the graphite particles 310 in the second negative electrode film layer 300, and the remaining lithium ions are embedded in the first In the negative electrode film layer 200, because some lithium ions are first embedded in the second negative electrode film layer 300, the concentration of lithium ions moving to the first negative electrode film layer 200 is reduced and the speed becomes slow, so that the lithium ions have enough time to be embedded in the silicon.
  • the particle size of hard carbon particles 210 is smaller than the particle size of silicon particles 220 .
  • the outer periphery of the silicon particle 220 can be coated by the hard carbon particle 210 , that is, the hard carbon particle 210 surrounds the silicon particle 220 and is attached to the outer periphery of the silicon particle 220 , so that the silicon particle 220 can be completely covered by the hard carbon particle 210 Covered or partially covered.
  • the D50 particle diameter of the silicon particles 220 is 6 ⁇ m-10 ⁇ m, and the D90 particle diameter is 18 ⁇ m-20 ⁇ m; for example, the D50 of the silicon particles 220 may be 6 ⁇ m, 8 ⁇ m, or 10 ⁇ m; the D90 of the silicon particles 220 may be 18 ⁇ m, 19 ⁇ m, or 20 ⁇ m.
  • the particle size of the hard carbon particles 210 is 0.5 ⁇ m-2 ⁇ m.
  • the particle size of the hard carbon particles 210 may be 0.5 ⁇ m, 1.5 ⁇ m, or 2 ⁇ m.
  • D50 refers to the particle diameter at which the cumulative distribution of particles is 50%, also called the median diameter or median particle diameter. This is a typical value indicating the particle size. This value accurately divides the whole into two equal parts, that is Say 50% of the particles are above this value and 50% are below this value. If the D50 of a sample is 6 ⁇ m, it means that among the particles of all particle sizes that make up the sample, particles larger than 6 ⁇ m account for 50%, and particles smaller than 6 ⁇ m also account for 50%.
  • D90 refers to the particle size at which the cumulative distribution of particles is 90%, that is, the volume content of particles smaller than this size accounts for 90% of all particles.
  • the main function of using large-diameter silicon particles 220 and small-diameter hard carbon particles 210 in combination is to further improve the dynamic performance of the negative electrode sheet.
  • the silicon particles 220 have poor dynamic properties, especially the D90 silicon particles 220, which have larger particle sizes and poor dynamic properties. Therefore, using hard carbon particles 210 to coat the D90 silicon particles 220 can effectively improve the dynamic performance of the silicon particles 220 and improve the lithium deposition around the silicon particles 220, thereby effectively increasing the charging speed of the lithium-ion battery.
  • using small-diameter hard carbon particles 210 can make the outer periphery of the silicon particles 220 coated with more hard carbon particles 210 , thereby more effectively improving the dynamic performance of the silicon particles 220 .
  • the dynamic properties of the hard carbon particles 210 are significantly better than those of the silicon particles 220 and the graphite particles 310 , the lithium ions on the periphery of the silicon particles 220 can be quickly embedded into the hard carbon particles 210 , thus effectively improving the performance of the silicon particles 220
  • the surrounding lithium is deposited; thus, the dynamic performance of the negative electrode sheet is effectively improved, the fast charging capability of the lithium-ion battery is improved, and the battery life and life of the lithium-ion battery are effectively improved.
  • the hard carbon particles 210 may be spherical particles. Using spherical particles as the hard carbon particles 210 can enable the silicon particles 220 to be coated with more hard carbon particles 210 on the periphery, thereby further improving the kinetic performance of the lithium-ion battery. .
  • the mass proportion of the silicon particles 220 in the first negative electrode film layer 200 may be 0.1%-30%.
  • the mass proportion of silicon particles 220 can be 0.1%, 5%, 10%, 20% or 30%, and its specific content can be set according to actual conditions.
  • the first negative electrode film layer 200 further includes a lithium replenishing agent for increasing the content of lithium ions in the first negative electrode film layer 200 .
  • the mass ratio between the lithium replenishing agent and the silicon particles 220 may be 1% to 30%.
  • the mass ratio between the lithium replenishing agent and the silicon particles may be 1%, 5%, 10%, 15%, 25% or 30%.
  • the main reason for adding lithium replenishing agent is that the content of lithium ions embedded and extracted from the silicon particles 220 during the first charge and discharge is different. Usually, more lithium ions are embedded and less extracted (commonly known as eating lithium); after depreciation As a result, the capacity of the lithium-ion battery decreases after the first charge and discharge, resulting in a decrease in the energy density of the lithium-ion battery.
  • the purpose of replenishing lithium in the first negative electrode film layer 200 containing the silicon particles 220 is to remove the lithium particles that the silicon particles 220 will eat in advance. It is first placed in the first negative electrode film layer 200, so that the lithium eaten by the silicon particles 220 can be replenished during the first charge and discharge, which is beneficial to improving the problem of reduced capacity of the lithium-ion battery.
  • the hard carbon particles 210 can improve the dynamic performance of the lithium-ion battery, the first effect of the hard carbon particles 210 is low, which seriously affects the capacity of the lithium-ion battery. Therefore, the first negative electrode film layer 200 needs to be replenished with lithium.
  • the lithium replenishing agent may be metal lithium powder, such as SLMP (stabilized lithium metal powder), lithium peroxide and other lithium replenishing agents.
  • the lithium replenishing agent to the first negative electrode film layer 200, that is, adding the lithium replenishing agent to a layer close to the negative electrode current collector 100, it is avoided that the negative electrode film layer to which the lithium replenishing agent is added is in direct contact with the separator.
  • the second negative electrode film layer 300 By bonding the second negative electrode film layer 300 to the separator, the technical problem of non-adhesion between the negative electrode sheet and the separator due to the addition of lithium replenishing agent is solved.
  • the first negative electrode film layer 200 may also include a first conductive agent, a first binder and a first thickener, and the mixed material 230, the first conductive agent, the first binder and the first thickener mass
  • the ratios are respectively 75wt%-99wt%: 0.1wt%-5wt%: 0.1wt%-5wt%: 0.5wt%-5wt%.
  • the mass ratio of the mixed material 230, the first conductive agent, the first binder and the first thickener may be, 75wt%: 0.1wt%: 0.1wt%: 0.5wt%, 85wt%: 2wt% : 3wt%: 2.5wt%, 96.9wt%: 0.5wt%: 1.3wt%: 1.3wt% or 99wt%: 5wt%: 5wt%: 5wt%: 5wt%.
  • the first conductive agent may be one or more of conductive carbon black, carbon fiber, Ketjen black, acetylene black, carbon nanotubes and graphene.
  • the first thickener may be sodium carboxymethylcellulose or lithium carboxymethylcellulose.
  • the first binder can be a water-based binder, for example, it can be styrene-butadiene rubber, nitrile rubber, butadiene rubber, modified styrene-butadiene rubber, sodium polyacrylate, water-based polyacrylonitrile copolymer or polyacrylate. one or several mixtures.
  • the second negative electrode film layer 300 also includes a second conductive agent, a second binder and a second thickening agent. agent, and the mass ratios of the graphite particles 310, the second conductive agent, the second binder and the second thickener are respectively 75wt%-99wt%: 0.1wt%-5wt%: 0.1wt%-5wt%: 0.5wt% -5wt%.
  • the mass ratio of the graphite particles 310, the second conductive agent, the second binder and the second thickener may be, 75wt%: 0.1wt%: 0.1wt%: 0.5wt%, 85wt%: 2wt% : 3wt%: 2.52wt%, 96.9wt%: 0.5wt%: 1.3wt%: 1.3wt% or 99wt%: 5wt%: 5wt%: 5wt%: 5wt%.
  • the second conductive agent may be one or more of conductive carbon black, carbon fiber, Ketjen black, acetylene black, carbon nanotubes and graphene.
  • the second thickener may be sodium carboxymethylcellulose or lithium carboxymethylcellulose.
  • the second binder can be a water-based binder, for example, it can be styrene-butadiene rubber, nitrile rubber, butadiene rubber, modified styrene-butadiene rubber, sodium polyacrylate, water-based polyacrylonitrile copolymer or polyacrylate. one or several mixtures.
  • the ratio of the thickness d1 of the first negative electrode film layer 200 to the thickness d2 of the second negative electrode film layer 300 may be 1:9-9:1.
  • the ratio of the thickness d1 of the first negative electrode film layer 200 to the thickness d2 of the second negative electrode film layer 300 may be 1:9, 5:5 or 9:1, and the thickness d1 of the first negative electrode film layer 200 may be 44 ⁇ m, and the thickness d2 of the second negative electrode film layer 300 may be 56 ⁇ m.
  • the ratio of the D90 of the graphite particles 310 in the second negative electrode film layer 300 to the D90 of the silicon particles 220 is 1.0-1.5. It can be seen that the particle size of the graphite particles 310 is larger. By dividing the graphite particles 310 Select larger particles. On the one hand, large particles can improve compaction; on the other hand, large particles of graphite particles 310 can have more gaps between them, thereby increasing the porosity of the negative electrode sheet and thus improving the battery core protection.
  • the liquid volume reduces the surface polarization of the negative electrode sheet and improves the dynamic performance of the negative electrode sheet, thereby further improving the battery life and life of the lithium-ion battery.
  • An embodiment of the present disclosure also provides a lithium ion battery, which includes a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, and the negative electrode sheet is the negative electrode sheet in the above embodiment.
  • the first negative electrode film layer 200 and the second negative electrode film layer 300 are sequentially disposed on the surface of the negative electrode current collector, that is, the first negative electrode film layer 100 is attached to the surface of the negative electrode current collector 100.
  • the second negative electrode film layer 300 is attached to the surface of the first negative electrode film layer 200 , and the active material of the first negative electrode film layer 200 includes silicon particles 220 and hard carbon particles 210 , and the active material of the second negative electrode film layer 300 includes graphite particles.
  • the negative electrode film layer is divided into two layers, in which the active material of the negative electrode film layer close to the negative electrode current collector includes a mixture of silicon particles 220 and hard carbon particles 210, and the active material of the other negative electrode film layer far away from the negative electrode current collector 100 includes Graphite particles 310, so that when lithium ions move to the negative electrode sheet, some lithium ions are first embedded in the second negative electrode film layer In the graphite particles in 300, the remaining lithium ions are embedded in the first negative electrode film layer 200.
  • the concentration of lithium ions moving to the first negative electrode film layer 200 is reduced and The speed becomes slower, thereby allowing lithium ions to have enough time to be embedded in the silicon particles and hard carbon particles, thereby reducing the aggregation of lithium ions at the silicon particles 220 and the nearby hard carbon particles 210, thereby alleviating the uneven distribution of lithium ions.
  • This is a uniform phenomenon, which reduces the precipitation of lithium and improves the endurance of lithium-ion batteries.
  • the dynamic performance of hard carbon particles 210 is significantly better than that of silicon particles 220 and graphite particles 310, the mixed use of silicon particles 220 and hard carbon particles 210 can effectively improve the dynamic performance of lithium-ion batteries, thereby It improves the charging speed of lithium-ion batteries and solves the technical problem of reduced lithium-ion fast charging capabilities in related technologies.
  • an embodiment of the present disclosure also provides a method for preparing a negative electrode sheet, including:
  • the method further includes baking the negative electrode sheet at a temperature of 80°C-100°C for a certain period of time, rolling the negative electrode sheet, and placing the rolled negative electrode sheet at a temperature of 100-120°C and then baking it. After baking for a certain period of time, the negative electrode sheet is obtained.
  • a certain amount of graphite particles 310 and silicon particles 220 are obtained: wherein the particle size of the hard carbon particles 210 is 1 ⁇ m; the particle size D50 of the silicon particle size is 7 ⁇ m, and the particle size D90 is 19 ⁇ m; and the D10 size of the graphite particle 310 is The particle size is 6 ⁇ m, the particle size of D50 is 12 ⁇ m, and the particle size of D90 is 25 ⁇ m.
  • the hard carbon particles 210 and the silicon particles 220 are taken according to a mass ratio of 95:5, and the two are mixed to obtain a mixed material 230 .
  • the first negative electrode film layer 200 slurry To prepare the first negative electrode film layer 200 slurry, mix the mixture material 230, the first conductive agent, the first binder, and the first thickener evenly to obtain the first negative electrode film layer 200 slurry.
  • the mixed material 230, the first conductive agent, the first binder, and the first thickener are added to the mixing tank at a mass ratio of 96.9wt%: 0.5wt%: 1.3wt%: 1.3wt%, The above ratio is the dry material mass ratio; at the same time, a certain amount of SLMP (stabilized lithium metal powder) is added to the above materials, where the added amount of SLMP (stabilized lithium metal powder) is 10% of the silicon particle 220 content. And use NMP solvent to prepare the first negative electrode film layer 200 slurry, and the solid content in this slurry is 42%.
  • the first conductive agent in this embodiment can be conductive carbon black
  • the first thickener can be sodium carboxymethylcellulose
  • the first binder can be water-emulsion styrene-butadiene rubber
  • the hard carbon particles 210 can be It is artificial graphite.
  • the graphite particles 310, the second conductive agent, the second binder, and the second thickener are evenly mixed to obtain the second negative electrode film layer 300 slurry.
  • the second negative electrode film layer 300 slurry is prepared.
  • the above ratio is the dry material mass ratio, and the solid content in this slurry is 42%.
  • the second conductive agent in this embodiment can be conductive carbon black
  • the second thickener can be sodium carboxymethylcellulose
  • the second binder can be water-emulsion styrene-butadiene rubber
  • the hard carbon particles 210 can be It is artificial graphite.
  • the negative electrode current collector 100 of the film layer 200 slurry and the second negative electrode film layer 300 slurry is dried.
  • a coating machine is used to coat the first negative electrode film layer 200 slurry containing silicon particles on the surface of the negative electrode current collector 100, and the second negative electrode film layer 300 of pure graphite particles 310 containing no silicon particles is coated on the surface of the negative electrode current collector 100. Apply on the surface of the first negative electrode film layer 200 slurry. Then dry it in a 5-stage oven Drying, the temperatures of each oven section are 60°C, 80°C, 110°C, 110°C, and 100°C respectively. After drying, the thickness of the second negative electrode film layer 300 can be 55um, and the thickness of the second negative electrode film layer 300 can be 55um. The ratio of the thickness of the first negative electrode film layer 200 to the thickness of the second negative electrode film layer 300 is 5:5.
  • the negative electrode sheet is baked at 80°C-100°C for a certain period of time. This process can fully volatilize the remaining NMP solvent in the negative electrode sheet, thereby increasing the porosity of the negative electrode sheet and improving the power of the negative electrode sheet. academic performance. Then, the negative electrode sheet is rolled, and the rolled negative electrode sheet is placed at 100-120° C. and baked for a certain period of time to obtain the negative electrode sheet.
  • lithium cobalt oxide as the positive active material, add the positive active material, conductive agent and thickener into the stirring tank at a mass ratio of 97.2:1.5:1.3, and add NMP (1-methyl 2-pyrrolidone) solvent Stir thoroughly and pass the mixed slurry through a screen to finally prepare the positive electrode slurry.
  • the solid content of the positive electrode slurry is 70% to 75%, and then a coater is used to coat the slurry on the positive electrode current collector.
  • the positive electrode current collector can be aluminum foil, and it is dried at 120°C to obtain the positive electrode sheet. .
  • the negative electrode sheet prepared above, the positive electrode sheet, and the separator are rolled together to form a core, packaged with aluminum plastic film, baked to remove moisture, and then injected with electrolyte.
  • the battery core can be obtained by using a hot-pressing process.
  • Embodiment 1 The difference between this embodiment and Embodiment 1 is that the added amount of SLMP (stabilized lithium metal powder) in the first negative electrode film layer 200 is 5% of the content of the silicon particles 220 .
  • SLMP stabilized lithium metal powder
  • the difference between this embodiment and Embodiment 1 is that the addition amount of SLMP (stabilized lithium metal powder) in the first negative electrode film layer 200 is 20% of the content of the silicon particles 220 .
  • SLMP stabilized lithium metal powder
  • Embodiment 1 The difference between this embodiment and Embodiment 1 is that the ratio of the content of hard carbon particles 210 to the content of silicon particles 220 in the first negative electrode film layer 200 is 90:10.
  • Embodiment 1 The difference between this embodiment and Embodiment 1 is that the hard carbon particles in the first negative electrode film layer 200
  • the particle size of 210 is 2 ⁇ m.
  • Embodiment 1 The difference between this embodiment and Embodiment 1 is that the D50 particle size of the silicon particles 220 in the first negative electrode film layer 200 is 6 ⁇ m, and the D90 particle size is 18 ⁇ m.
  • Embodiment 1 The difference between this embodiment and Embodiment 1 is that the particle size of D10 in the graphite particles 310 is 4 ⁇ m, the particle size of D50 is 11 ⁇ m, and the particle size of D90 is 23 ⁇ m.
  • Embodiment 1 The difference between this embodiment and Embodiment 1 is that the particle size of D10 in the graphite particles 310 is 4 ⁇ m, the particle size of D50 is 14 ⁇ m, and the particle size of D90 is 28 ⁇ m.
  • Embodiment 1 The difference between this embodiment and Embodiment 1 is that no lithium replenishing agent is added to the first negative electrode film layer 200 .
  • the negative electrode film layer has a one-layer structure, that is, the active material includes silicon particles 220 and graphite particles 310, which are mixed and then coated on the negative electrode current collector 100 to form a negative electrode film layer.
  • Negative plate the particle size of D10 in the graphite particles 310 is 6 ⁇ m, the particle size of D50 is 12 ⁇ m, and the particle size of D90 is 25 ⁇ m.
  • the active material in the first negative electrode film layer 200 includes silicon particles 220 and graphite particles 310
  • the active material in the second negative electrode film layer 300 includes graphite particles 310, that is, the first negative electrode
  • the active materials in the film layer 200 and the second negative electrode film layer 300 both include graphite particles 310 .
  • the particle diameter of D10 is 6 ⁇ m
  • the particle diameter of D50 is 12 ⁇ m
  • the particle diameter of D90 is 25 ⁇ m.
  • Each battery cell prepared above was subjected to 1.2C step charging/0.7C discharge at 25°C, and the battery was disassembled at different cycles to confirm the lithium deposition on the negative electrode surface of the battery.
  • the disassembly results and energy density are as follows:
  • Table 1 shows the main relevant parameters of Examples 1-9 and Comparative Examples 1-2.
  • the degree of lithium precipitation on the surface of the negative electrode sheet is represented by 0, 1, 2, 3, 4, and 5.
  • 0 no lithium precipitation
  • 5 represents severe lithium precipitation
  • 1, 2, 3, and 4 represent different degrees of lithium precipitation. , the larger the number, the more serious the degree of lithium precipitation.
  • Examples 1 to 3 are the effects of the amount of lithium replenishing agent in the first negative electrode film layer 200 on the lithium deposition of the negative electrode sheet, that is, when the amount of lithium replenishing agent added is 5% and 10 %, when the lithium-ion battery undergoes 500T (cycle) charge and discharge, no lithium is precipitated on the surface of the negative electrode sheet; when the amount of lithium replenishing agent reaches 20%, when the lithium-ion battery undergoes 500T (cycle) charge and discharge, During discharge, the degree of lithium precipitation on the surface of the negative electrode sheet is 1.
  • the amount of lithium supplement has a certain impact on the battery capacity retention rate and expansion rate.
  • the addition amount of lithium replenishing agent is 10%, 5% and 20%
  • the capacity retention rates of the lithium-ion battery are 87.04%, 85.52% and 82.65% respectively
  • the expansion rates of the lithium-ion battery are 9.17%, 9.39%, and 9.54% respectively.
  • Example 9 the added amount of lithium replenishing agent is 0.
  • the capacity retention rate of the lithium ion battery is 82.36%
  • the lithium ion battery undergoes 700T (cycle) charge and discharge.
  • the expansion rate of lithium-ion batteries is 9.89% respectively.
  • the capacity retention rate of lithium-ion batteries can be improved by adding lithium replenishing agent. but, When too much lithium replenishing agent is added, the capacity retention rate of the battery will be reduced and the expansion rate will increase. Therefore, an appropriate amount of lithium replenishing agent should be added to obtain a lithium-ion battery with excellent comprehensive performance.
  • Example 1 and Example 4 it can be seen from Example 1 and Example 4 that when the ratio of the silicon particles 220 to the first graphite particles 310 in the first negative electrode film layer 200 reaches 10:90, the lithium ion battery undergoes 500T (cycle) charge and discharge. When , the degree of lithium precipitation on the surface of the negative electrode sheet is 1. When the lithium-ion battery undergoes 700T (cycle) charge and discharge, the capacity retention rate of the lithium-ion battery is 80.47%; when the lithium-ion battery undergoes 700T (cycle) charge and discharge, the expansion rate of the lithium-ion battery is 10.09% respectively.
  • Embodiment 1 and Embodiment 5 when the particle size of the hard carbon particles 210 in the first negative electrode film layer 200 is larger, that is, when the particle size of the hard carbon particles 210 reaches 2 ⁇ m, the lithium ion battery passes through the battery.
  • the degree of lithium precipitation on the surface of the negative electrode sheet is 0.
  • the capacity retention rate of the lithium-ion battery is 82.98%; when the lithium-ion battery undergoes 700T (cycle) charge and discharge, the expansion rate of the lithium-ion battery is 9.62%.
  • Embodiment 1 and Embodiment 6 that when the particle size of the silicon particles 220 in the first negative electrode film layer 200 is smaller, that is, the particle size D50 of the silicon particles 220 reaches 6 ⁇ m, and the particle size D90 reaches 18 ⁇ m. , that is, when the particle size of the silicon particles 220 decreases accordingly, and when the lithium-ion battery undergoes 500T (cycle) charge and discharge, the degree of lithium precipitation on the surface of the negative electrode sheet is 0.
  • the capacity retention rate of the lithium-ion battery is 88.52%; when the lithium-ion battery undergoes 700T (cycle) charge and discharge, the expansion rate of the lithium-ion battery is 9.06%.
  • Embodiment 1 and 7 when the particle size of the carbon particles in the second negative electrode film layer 300 is smaller, that is, the particle size D10 of the graphite particle 310 reaches 4 ⁇ m, the particle size D50 reaches 11 ⁇ m, and the particle size D90 reaches 23 ⁇ m.
  • the degree of lithium precipitation on the surface of the negative electrode sheet is 0.
  • the capacity retention rate of the lithium-ion battery is 89.92%; when the lithium-ion battery undergoes 700T (cycle) charge and discharge, the expansion rate of the lithium-ion battery is 8.77%.
  • Example 1 and Example 8 it can be seen from Example 1 and Example 8 that when the particle size of the carbon particles in the second negative electrode film layer 300 is larger, that is, the particle size D10 of the graphite particle 310 reaches 4 ⁇ m, the particle size D50 reaches 14 ⁇ m, and the particle size D90 reaches At 28 ⁇ m, when the lithium-ion battery undergoes 500T (cycle) charge and discharge, the degree of lithium precipitation on the surface of the negative electrode sheet is 0. When the lithium-ion battery undergoes 700T (cycle) charge and discharge, the capacity retention rate of the lithium-ion battery is 79.47%; when the lithium-ion battery undergoes 700T (cycle) charge and discharge, the expansion rate of the lithium-ion battery is 11.09%.
  • the capacity retention rate of the lithium-ion battery shows an obvious downward trend
  • the volume expansion rate also shows an obvious increasing trend. Therefore, although the graphite particles 310 in the second negative electrode film layer 300 have a larger particle size, they can increase the porosity of the negative electrode sheet, thereby increasing the liquid retention capacity of the battery core, reducing the surface polarization of the negative electrode sheet, and improving the dynamic performance of the negative electrode sheet. This further improves the battery life and battery life of lithium-ion batteries.
  • the number of carbon particles in the second negative electrode film layer 300 will be significantly reduced, which will in turn lead to a significant reduction in the amount of lithium ions embedded in the second negative electrode film layer 300, resulting in more carbon particles.
  • Lithium ions accumulate near the silicon particles 220, thereby affecting the capacity retention rate and expansion rate of the lithium-ion battery.
  • Comparative Example 1 when the slurry mixed with silicon particles 220 and graphite particles 310 is applied to the negative electrode current collector to form a negative electrode film layer, the lithium ion battery undergoes 500T (cycle) charge and discharge. , the surface lithium precipitation degree of the negative electrode sheet is 5; when the lithium-ion battery undergoes 700T (cycle) charge and discharge, the capacity retention rate of the lithium-ion battery is 65.32%; when the lithium-ion battery undergoes 700T (cycle) charge and discharge, the lithium The expansion rate of the ion battery was 17.65% respectively.
  • Comparative Example 2 Compared Comparative Example 2 with Comparative Example 1, although the overall performance of the lithium-ion battery can be improved to a certain extent by dividing the negative electrode film layer into two layers, the lithium deposition situation is still serious, and the capacity of the lithium-ion battery is still relatively serious. The retention rate is still low, and the expansion rate of lithium-ion batteries is large.
  • first and second are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of indicated technical features. Therefore, features defined as “first”, “second” and “third” may explicitly or implicitly include at least one of these features.
  • “plurality” means at least two, such as two, three, etc., unless otherwise explicitly and specifically limited.
  • connection In the embodiments of the present disclosure, unless otherwise clearly stated and limited, the terms “installation”, “connection”, “connection”, “fixing” and other terms should be understood in a broad sense. For example, it can be a fixed connection or a fixed connection. Detachable connection, or integration; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be an internal connection between two elements or an interactive relationship between two elements, unless There are clear limitations. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present disclosure can be understood according to specific circumstances.
  • the first feature "on” or “below” the second feature may be that the first and second features are in direct contact, or the first and second features are in intermediate contact. Indirect media contact.
  • the terms “above”, “above” and “above” the first feature is above the second feature may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is higher in level than the second feature.
  • "Below”, “below” and “beneath” the first feature to the second feature may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature has a smaller horizontal height than the second feature.
  • references to the terms “one embodiment,” “some embodiments,” “an example,” “specific examples,” or “some examples” or the like means that specific features are described in connection with the embodiment or example.
  • structures, materials or features are included in at least one embodiment or example of embodiments of the present disclosure.
  • the schematic expressions of the above terms are not necessarily directed to the same embodiment or example.
  • the specific features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
  • those skilled in the art may combine and combine different embodiments or examples and features of different embodiments or examples described in this specification unless they are inconsistent with each other.

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Abstract

本公开实施例涉及电池技术领域，具体涉及一种负极片及锂离子电池，用以解决石墨颗粒和硅颗粒混合的功能层易出现析锂现象，从而影响锂离子电池的续航和寿命的技术问题，该负极片包括负极集流体，第一负极膜层贴于负极集流体的表面上；且第一负极膜层的活性物质包括硅颗粒和硬碳颗粒；第二负极膜层贴于第一负极膜层的表面上，第二负极膜层的活性物质包括石墨颗粒，从而使得当锂离子移动至负极片处时，部分锂离子先嵌入第二负极膜层中，剩余的锂离子嵌入第一负极膜层中，进而降低了锂的析出，同时硬碳颗粒能够提高锂离子电池的动力学性能，由此提高了锂离子电池充电速度，解决了相关技术中锂离子快充能力降低的技术问题。

Description

负极片及锂离子电池
本申请要求于2022年4月7日提交中国专利局、申请号为202210360693.X、申请名称为“负极片及锂离子电池”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本公开涉及电池技术领域，尤其涉及一种负极片及锂离子电池。
背景技术
近年来，随着便携式电子产品销量呈现爆发式增长，锂离子电池已经成为各种设备的电源。相关技术中，锂离子电池包括正极片、负极片、隔膜和电解液，负极片包括金属片以及覆盖在金属片上的功能层，功能层由石墨颗粒和硅颗粒混合形成。
然而，在锂离子电池充放电的过程中，采用石墨颗粒和硅颗粒混合形成的功能层的锂离子电池的快充能力降低，进而影响了锂离子电池在大电流充放电下的充放电性能。
申请内容
本公开实施例提供一种负极片、锂离子电池及负极片的制备方法，用以解决相关技术中锂离子快充能力降低的技术问题。
本公开实施例解决上述技术问题的方案如下：
一种负极片，包括，
负极集流体；
第一负极膜层，其贴于所述负极集流体的表面上；且所述第一负极膜层的活性物质包括硅颗粒和硬碳颗粒；且所述第一负极膜层包括补锂剂；
第二负极膜层，其贴于所述第一负极膜层的表面上；且所述第二负极膜层的活性物质包括石墨颗粒。
本公开实施例的有益效果是：通过在负极集流体的表面上依次设置第 一负极膜层和第二负极膜层，即第一负极膜层贴于负极集流体的表面上，第二负极膜层贴于第一负极膜层的表面上，且第一负极膜层的活性物质包括硅颗粒和硬碳颗粒，第二负极膜层的活性物质包括石墨颗粒，即将负极膜层分成了两层，其中靠近负极集流体的负极膜层的活性物质包括硅颗粒和硬碳颗粒的混合物，另一远离负极集流体的负极膜层的活性物质包括石墨颗粒，从而使得当锂离子移动至负极片处时，部分锂离子先嵌入第二负极膜层中的石墨颗粒内，剩余的锂离子嵌入第一负极膜层中，由于部分锂离子先嵌入第二负极膜层中，使得移动至第一负极膜层处的锂离子浓度降低且速度变缓慢，从而使得锂离子具有足够的时间嵌入硅颗粒和硬碳颗粒中，进而降低了锂离子在硅颗粒处及其附近硬碳颗粒处的聚集，进而减轻了锂离子浓度分布不均的现象，即降低了锂的析出，改善了锂离子电池的续航能力。同时，由于硬碳颗粒的动力学性能明显优于硅颗粒和石墨颗粒，由此通过采用硅颗粒和硬碳颗粒混合使用，能够有效的提高锂离子电池的动力学性能，从而提高了锂离子电池充电速度，解决了相关技术中锂离子电池快充能力降低的技术问题。
在一种可能的实现方式中，所述补锂剂包括金属锂粉和/或过氧化锂。
在一种可能的实现方式中，所述硬碳颗粒的粒径小于所述硅颗粒的粒径，且所述硅颗粒的外壁被所述硬碳颗粒包覆。
在一种可能的实现方式中，所述第一负极膜层中的硅颗粒的D50的粒径为6μm-10μm、D90的粒径为18μm-22μm。
在一种可能的实现方式中，所述硬碳颗粒为球形颗粒，所述硬碳颗粒的粒径为0.5μm-2μm。
在一种可能的实现方式中，所述第二负极膜层中的石墨颗粒的D10的粒径为3μm-6μm、D50的粒径为11μm-14μm、D90的粒径为22μm<D90<29μm。
在一种可能的实现方式中，所述石墨颗粒的D90的粒径与所述硅颗粒的D90的粒径之比为1.0-1.5。
在一种可能的实现方式中，所述第一负极膜层的厚度与所述第二负极膜层的厚度之比为1:9-9:1。
在一种可能的实现方式中，所述补锂剂与所述硅颗粒之间的质量比为1％～30％。
一种锂离子电池，其包括正极片、负极片、隔膜和电解液，所述负极片为以上任一项所述的负极片。
附图说明
图1为本公开实施例提供的一种负极片中的第一负极膜层和第二负极膜层的示意图；
图2为本公开实施例提供的硬碳颗粒、硅颗粒、混合物料及石墨颗粒的结构示意图；
图3为本公开实施例提供的负极片的制备方法的流程图。
附图标记说明：
100、负极集流体；200、第一负极膜层；210、硬碳颗粒；220、硅颗
粒；230、混合物料；300、第二负极膜层；310、石墨颗粒。
具体实施方式
近年来，随着便携式电子产品销量呈现爆发式增长，锂离子电池已经成为各种设备的电源。人们对锂离子电池的性能要求也进一步提高，要求锂离子电池具备较长的寿命是作为锂离子电池的一项重要指标。
相关技术中，锂离子电池包括正极片、负极片、隔膜和电解液；其中负极片包括金属片以及覆盖在金属片上的功能层。为了提高锂离子电池的能量密度，此功能层由石墨和硅混合而成，因为硅的储锂量远大于石墨，从而能够提升锂离子电池的能量密度，进而能够提高锂离子电池的续航和寿命。
然而，在锂离子电池充放电的过程中，由于硅及氧化硅材料和石墨材料导电性及储锂量差异，同时因硅材料导电性差，最终使得硅材料和石墨材料掺混后的负极片的动力学性能降低，由此导致锂离子电池快充能力的降低，进而影响其在大电流充放电下的充放电性能。
有鉴于此，本公开实施例提供了一种负极片，其包括负极集流体，且在负极集流体的表面上依次设置第一负极膜层和第二负极膜层，即第一负极膜层贴于负极集流体的表面上，第二负极膜层贴于第一负极膜层的表面上，且第一负极膜层的活性物质包括硅颗粒和硬碳颗粒，第二负极膜层的 活性物质包括石墨颗粒，即将负极膜层分成了两层，其中靠近负极集流体的负极膜层的活性物质包括硅颗粒和硬碳颗粒的混合物，另一远离负极集流体的负极膜层的活性物质包括石墨颗粒，从而使得当锂离子移动至负极片处时，部分锂离子先嵌入第二负极膜层中的石墨颗粒内，剩余的锂离子嵌入第一负极膜层中，由于部分锂离子先嵌入第二负极膜层中，使得移动至第一负极膜层处的锂离子浓度降低且速度变缓慢，从而使得锂离子具有足够的时间嵌入硅颗粒和硬碳颗粒中，进而降低了锂离子在硅颗粒处及其附近硬碳颗粒处的聚集密度，进而减轻了锂离子浓度分布不均的现象，即降低了锂的析出，改善了锂离子电池的续航能力。同时，由于硬碳颗粒的动力学性能明显优于硅颗粒和石墨颗粒，由此通过采用硅颗粒和硬碳颗粒混合使用，能够有效的提高锂离子电池的动力学性能，从而提高了锂离子电池充电速度，解决了相关技术中锂离子电池快充能力降低的技术问题。
为了使本申请实施例的上述目的、特征和优点能够更加明显易懂，下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行清楚、完整地描述。显然，所描述的实施例仅仅是本申请的一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有作出创造性劳动的前提下所获得的所有其它实施例，均属于本申请保护的范围。
参考图1和图2，本公开实施例提供了一种负极片，包括负极集流体100，第一负极膜层200贴于负极集流体100的表面上；且第一负极膜层200的活性物质包括硅颗粒220和硬碳颗粒210；第二负极膜层300贴于第一负极膜层200的表面上；且第二负极膜层300的活性物质包括石墨颗粒310。
其中，负极集流体100可以为铜箔，其主要是起导电作用，同时作为负极膜层的载体，且铜箔的厚度可以为4-15μm，例如铜箔的厚度可以为4μm、7μm、11μm或15μm。其中，铜箔可以为均质铜箔、多孔铜箔或带涂炭层的铜箔中的一种。
示例性地，第一负极膜层200可以是通过第一负极膜层200浆料涂于负极集流体100的表面上，且通过烘干后得到的膜层。其中，第一负极膜层200浆料可以包括NMP(1-甲基2-吡咯烷酮)溶剂，即通过NMP溶剂将硅颗粒220和硬碳颗粒210混合均匀形成浆料，并将此浆料涂于铜箔上， 从而形成具有硅颗粒220和硬碳颗粒210混合的活性物质的第一负极膜层200。
示例性地，第二负极膜层300可以是通过第二负极膜层300浆料涂于第一负极膜层200的表面上，且可以通过烘干后得到膜层。其中，第二负极膜层300浆料可以包括NMP溶剂，即通过NMP溶剂将石墨颗粒310和成浆料，并将此浆料涂于铜箔上，从而形成具有石墨颗粒310的活性物质的第二负极膜层300。
需要说明的是，硬碳颗粒210是指难以被石墨化的碳，是高分子聚合物的热分解产物。
示例性地，石墨颗粒310可以包括人造石墨、天然石墨、中间相碳微球、软碳、硬碳、有机聚合物化合物碳中的一种或多种；硅颗粒220可以包括氧化亚硅材料、碳化硅材料、纳米硅材料中的一种或多种。
本实施例中提供的负极片，通过将负极膜层分成了两层，其中靠近负极集流体100的负极膜层的活性物质包括硅颗粒220和硬碳颗粒210的混合物，另一远离负极集流体100的负极膜层的活性物质包括石墨颗粒310，从而使得当锂离子移动至负极片处时，部分锂离子先嵌入第二负极膜层300中的石墨颗粒310内，剩余的锂离子嵌入第一负极膜层200中，由于部分锂离子先嵌入第二负极膜层300中，使得移动至第一负极膜层200处的锂离子浓度降低且速度变缓慢，从而使得锂离子具有足够的时间嵌入硅颗粒220和硬碳颗粒210中，进而降低了锂离子在硅颗粒220处及其硬碳颗粒210处的聚集密度，进而减轻了锂离子浓度分布不均的现象，即降低了锂的析出，改善了锂离子电池的续航能力。同时，由于硬碳颗粒210的动力学性能明显优于硅颗粒220和石墨颗粒310，由此通过采用硅颗粒220和硬碳颗粒210混合使用，能够有效的提高锂离子电池的动力学性能，从而提高了锂离子电池充电速度，解决了相关技术中锂离子电池快充能力降低的技术问题。
在一些实施例中，硬碳颗粒210的粒径小于硅颗粒220的粒径。
示例性地，硅颗粒220的外周可以被硬碳颗粒210包覆，即硬碳颗粒210围绕硅颗粒220一周，且贴附于硅颗粒220的外周，使得硅颗粒220可以被硬碳颗粒210完全包覆或部分包覆。
示例性地，硅颗粒220的D50的粒径为6μm-10μm、D90的粒径为 18μm-20μm；例如，硅颗粒220的D50可以为6μm、8μm或10μm；硅颗粒220的D90可以为18μm、19μm或20μm。硬碳颗粒210的粒径为0.5μm-2μm，例如，硬碳颗粒210的粒径可以为0.5μm、1.5μm或2μm。
其中，D50是指颗粒累积分布为50％的粒径，也叫中位径或中值粒径，这是一个表示粒度大小的典型值，该值准确地将总体划分为二等份，也就是说有50％的颗粒超过此值，有50％的颗粒低于此值。如果一个样品的D50＝6μm，说明在组成该样品的所有粒径的颗粒中，大于6μm的颗粒占50％，小于6μm的颗粒也占50％。
D90是指颗粒累积分布为90％的粒径，即小于此粒径的颗粒体积含量占全部颗粒的90％
本实施例中采用大粒径的硅颗粒220和小粒径的硬碳颗粒210相配合的主要作用是进一步提高负极片的动力学性能。因为，硅颗粒220动力学性能差，尤其是D90的硅颗粒220，其粒径较大且动力学性能较差。由此，使用硬碳颗粒210包覆在D90硅颗粒220周围可以有效提高硅颗粒220动力学性能，改善硅颗粒220周围析锂的情况，从而能够有效的提高锂离子电池的充电速度。同时，采用小粒径的硬碳颗粒210能够使得硅颗粒220的外周包覆较多的硬碳颗粒210，从而能够更加有效的提高硅颗粒220动力学性能。换言之，由于硬碳颗粒210的动力学性能明显优于硅颗粒220和石墨颗粒310，从而使得硅颗粒220外周的锂离子能够快速的嵌入硬碳颗粒210内，因此能够有效的改善了硅颗粒220周围析锂的情况；由此，有效的提高了负极片的动力学性能，提高了锂离子电池的快充能力，并有效的提高锂离子电池的续航和寿命。
在一些实施例中，硬碳颗粒210可以为球形颗粒，硬碳颗粒210采用球形颗粒能够使得硅颗粒220的外周包覆较多的硬碳颗粒210，从而能够进一步提高锂离子电池的动力学性能。
在一些实施例中，第一负极膜层200中的硅颗粒220的质量占比可以为0.1％-30％。示例性地，硅颗粒220质量占比可以为0.1％、5％、10％、20％或30％，其具体的含量可以根据实际情况进行设定。
在一些实施例中，第一负极膜层200中还包括补锂剂，用于增加第一负极膜层200中锂离子的含量。另外，补锂剂与硅颗粒220之间的质量比可以为1％～30％，示例性地，补锂剂与硅颗粒之间的质量比可以为1％、5％、 10％、15％、25％或30％。
其中，需要说明的是添加补锂剂的主要原因是，硅颗粒220在首次充放电时嵌入和脱出的锂离子含量不一样，通常锂离子嵌入的多脱出的少(俗称吃锂)；折旧后导致锂离子电池首次充放电后锂离子电池的容量降低，导致锂离子电池能量密度降低；对含有硅颗粒220的第一负极膜层200补锂是为了提前把硅颗粒220要吃掉的锂粒子先放在第一负极膜层200中，从而在第一次充放电时可以补充被硅颗粒220吃掉的锂，有利于改善锂离子电池容量降低的问题。
同时，虽然硬碳颗粒210能改善锂离子电池的动力学性能，但是硬碳颗粒210的首效较低，其严重影响锂离子电池的容量，因此需要对第一负极膜层200进行补锂，来提升硬碳颗粒210的首效，进而提升第一负极膜层200的容量。示例性地，补锂剂可以为金属锂粉，例如SLMP(稳定化锂金属粉末)、过氧化锂等补锂剂。
同时，通过将补锂剂加入到第一负极膜层200中，即将补锂剂加入到靠近负极集流体100的一层，从而避免了添加补锂剂的负极膜层直接与隔膜接触，而是通过第二负极膜层300与隔膜相粘接，解决了因加入补锂剂，而导致负极片与隔膜不粘结的技术问题。
另外，第一负极膜层200还可以包括第一导电剂、第一粘结剂和第一增稠剂，且混合物料230、第一导电剂、第一粘结剂和第一增稠剂质量比分别为75wt％-99wt％：0.1wt％-5wt％：0.1wt％-5wt％：0.5wt％-5wt％。示例性地，混合物料230、第一导电剂、第一粘结剂和第一增稠剂的质量比可以为，75wt％：0.1wt％：0.1wt％：0.5wt％，85wt％：2wt％：3wt％：2.5wt％，96.9wt％：0.5wt％：1.3wt％：1.3wt％或者99wt％：5wt％：5wt％：5wt％。
示例性地，第一导电剂可以为导电碳黑、碳纤维、科琴黑、乙炔黑、碳纳米管和石墨烯中的一种或多种。
第一增稠剂可以为羧甲基纤维素钠或羧甲基纤维素锂。
第一粘结剂可以为水性粘结剂，例如，可以为丁苯橡胶、丁腈橡胶、丁二烯橡胶、改性丁苯橡胶、聚丙烯酸钠、水性聚丙烯腈共聚物或聚丙烯酸酯中的一种或者几种混合物。
另外，第二负极膜层300还包括第二导电剂、第二粘结剂和第二增稠 剂，且石墨颗粒310、第二导电剂、第二粘结剂和第二增稠剂质量比分别为75wt％-99wt％：0.1wt％-5wt％：0.1wt％-5wt％：0.5wt％-5wt％。示例性地，石墨颗粒310、第二导电剂、第二粘结剂和第二增稠剂的质量比可以为，75wt％：0.1wt％：0.1wt％：0.5wt％，85wt％：2wt％：3wt％：2.52wt％，96.9wt％：0.5wt％：1.3wt％：1.3wt％或者99wt％：5wt％：5wt％：5wt％。
示例性地，第二导电剂可以为导电碳黑、碳纤维、科琴黑、乙炔黑、碳纳米管和石墨烯中的一种或多种。
第二增稠剂可以为羧甲基纤维素钠或羧甲基纤维素锂。
第二粘结剂可以为水性粘结剂，例如，可以为丁苯橡胶、丁腈橡胶、丁二烯橡胶、改性丁苯橡胶、聚丙烯酸钠、水性聚丙烯腈共聚物或聚丙烯酸酯中的一种或者几种混合物。
在一些实施例中，第一负极膜层200的厚度d1与第二负极膜层300的厚度d2之比可以为1：9-9：1。示例性地，第一负极膜层200的厚度d1与第二负极膜层300的厚度d2之比可以为1：9、5：5或9：1，第一负极膜层200的厚度d1可以为44μm，第二负极膜层300的厚度d2可以为56μm。
在一些实施例中，第二负极膜层300中的石墨颗粒310的D90与硅颗粒220的D90之比为1.0-1.5，由此可知，石墨颗粒310的粒径较大，通过将石墨颗粒310选为较大颗粒，其一方面大颗粒可以提高压实；另一方面，大颗粒的石墨颗粒310之间可以具有较多的缝隙，从而能够提高负极片的孔隙率，进而能够提高电芯保液量，降低负极片表面极化，提高负极片动力学性能，由此进一步提高了锂离子电池的电池的续航和寿命。
本公开实施例还提供了一种锂离子电池，其包括正极片、负极片、隔膜和电解液，且负极片为上述实施例中的负极片。
本实施例提供的锂离子电池，通过在负极集流体的表面上依次设置第一负极膜层200和第二负极膜层300，即第一负极膜层100贴于负极集流体100的表面上，第二负极膜层300贴于第一负极膜层200的表面上，且第一负极膜层200的活性物质包括硅颗粒220和硬碳颗粒210，第二负极膜层300的活性物质包括石墨颗粒310，即将负极膜层分成了两层，其中靠近负极集流体的负极膜层的活性物质包括硅颗粒220和硬碳颗粒210的混合物，另一远离负极集流体100的负极膜层的活性物质包括石墨颗粒310，从而使得当锂离子移动至负极片处时，部分锂离子先嵌入第二负极膜层 300中的石墨颗粒内，剩余的锂离子嵌入第一负极膜层200中，由于部分锂离子先嵌入第二负极膜层300中，使得移动至第一负极膜层200处的锂离子浓度降低且速度变缓慢，从而使得锂离子具有足够的时间嵌入硅颗粒和硬碳颗粒中，进而降低了锂离子在硅颗粒220处及其附近硬碳颗粒210处的聚集，进而减轻了锂离子浓度分布不均的现象，即降低了锂的析出，改善了锂离子电池的续航能力。同时，由于硬碳颗粒210的动力学性能明显优于硅颗粒220和石墨颗粒310，由此通过采用硅颗粒220和硬碳颗粒210混合使用，能够有效的提高锂离子电池的动力学性能，从而提高了锂离子电池充电速度，解决了相关技术中锂离子快充能力降低的技术问题。
如图3所示，本公开实施例还提供了一种负极片的制备方法，包括，
S1：获取硬碳颗粒210、硅颗粒220和石墨颗粒310，并将硬碳颗粒210与硅颗粒220进行混合组成混合物料230；
S2：将混合物料230、第一导电剂、第一粘结剂、第一增稠剂混合均匀，以得到第一负极膜层200浆料；
S3：将石墨颗粒310、第二导电剂、第二粘结剂、第二增稠剂混合均匀，以得到第二负极膜层300浆料；
S4：将第一负极膜层200浆料涂敷在负极集流体100的表面上，将第二负极膜层300浆料涂敷在所述第一负极膜层200浆料表面上；
S5：对涂有第一负极膜层200浆料和第二负极膜层300浆料的所述负极集流体100进行烘干。
需要说明的是，以上制备方法可以按照以上顺序进行，也可以按照实际需要进行调换。
在一些实施例中，还包括，将负极片在80℃-100℃温度下进行烘烤一定时间后，将负极片进行辊压，将辊压后的负极片放置于100-120℃下再烘烤一定时间后，得到负极片。
为了能够更好的说明一种负极片、锂离子电池及其制备方法，下面将结合对比例和实施例进行详细说明。
实施例1
(一)负极片的制备
获取硬碳颗粒210、硅颗粒220和石墨颗粒310，并将所述硬碳颗粒210与所述硅颗粒220进行混合组成混合物料230；
示例性地，获取一定量的石墨颗粒310和硅颗粒220：其中，硬碳颗粒210的粒径为1μm；硅粒径的粒径D50为7μm，D90的粒径为19μm；石墨颗粒310的D10粒径为6μm、D50的粒径为12μm、D90的粒径为25μm。
将硬碳颗粒210与硅颗粒220按照质量比为95:5取料，并将两者进行混合后得到混合物料230。
(2)浆料制备
第一负极膜层200浆料的制备，将混合物料230、第一导电剂、第一粘结剂、第一增稠剂混合均匀，以得到第一负极膜层200浆料。
示例性地，将混合物料230、第一导电剂、第一粘结剂、第一增稠剂按96.9wt％：0.5wt％：1.3wt％：1.3wt％的质量比加入到搅拌罐中，以上比例为干料质量比；同时取一定量的SLMP(稳定化锂金属粉末)加入到上述物料中，其中，SLMP(稳定化锂金属粉末)加入量为硅颗粒220含量的10％。且用NMP溶剂配成第一负极膜层200浆料，且此浆料中固含量为42％。同时，本实施例中的第一导电剂可以为导电炭黑，第一增稠剂可以为羧甲基纤维素钠，第一粘结剂可以为水乳型丁苯橡胶，硬碳颗粒210可以为人造石墨。
第二负极膜层300浆料的制备，将石墨颗粒310、第二导电剂、第二粘结剂、第二增稠剂混合均匀，以得到第二负极膜层300浆料。
将石墨颗粒310、第二导电剂、第二增稠剂、第二粘结剂按96.9wt％：0.5wt％：1.3wt％：1.3wt％的质量比加入到搅拌罐中，且用NMP溶剂配成第二负极膜层300浆料，以上比例为干料质量比，且此浆料中固含量为42％。同时，本实施例中的第二导电剂可以为导电炭黑，第二增稠剂可以为羧甲基纤维素钠，第二粘结剂可以为水乳型丁苯橡胶，硬碳颗粒210可以为人造石墨。
(3)负极片的制备
将第一负极膜层200浆料涂敷在负极集流体100的表面上，将第二负极膜层300浆料涂敷在第一负极膜层200浆料的表面上；对涂有第一负极膜层200浆料和第二负极膜层300浆料的负极集流体100进行烘干。
示例性地，利用涂布机将含硅颗粒的第一负极膜层200浆料涂敷于负极集流体100的的表面上，不含硅颗粒的纯石墨颗粒310的第二负极膜层300涂敷于第一负极膜层200浆料的表面上。然后将其以5段烘箱进行干 燥，每段烤箱的温度分别为60℃、80℃、110℃、110℃、100℃，干燥后第二负极膜层300的厚度可以为55um，第二负极膜层300的厚度可以为55um，使得第一负极膜层200的层厚与第二负极膜层300的厚度之比为5：5。重复涂布完成负极集流体100的另一侧的双层膜层，从而使得负极集流体100的两侧的表面上均涂有两层负极膜层；利用辊压机进行加压处理，使得负极片的压实密度可以为1.75g/cm2，从而完成负极片的制备。
另外，在进行辊压前，负极片在80℃-100℃温度下进行烘烤一定时间后，此过程能够充分挥发负极片中残留的NMP溶剂，从而能够提高负极片孔隙率，提升负极片动力学性能。然后，将负极片进行辊压，将辊压后的负极片放置于100-120℃下再烘烤一定时间后，得到所述负极片。
(二)正极极片的制备
以钴酸锂为正极活性材料，将正极活性材料、导电剂及增稠剂按照质量比为97.2：1.5：1.3的质量比加入到搅拌罐中，加入NMP(1-甲基2-吡咯烷酮)溶剂进行充分搅拌，并将此混合后的浆料过筛网，最终配成正极浆料。其中，正极浆料固含量为70％～75％，再利用涂布机将浆料涂覆到正极集流体上，正极集流体可以为铝箔，在120℃温度下烘干，即得到正极极片。
(三)组装电芯
将上述制备的负极片和正极片、隔膜一起卷绕形成卷芯，用铝塑膜包装，烘烤去除水分后注入电解液，采用热压化成工艺化成即可得到电芯。
实施例2
本实施例与实施例1不同的地方在于：第一负极膜层200中SLMP(稳定化锂金属粉末)加入量为硅颗粒220含量的5％。
实施例3
本实施例与实施例1不同的地方在于：第一负极膜层200中SLMP(稳定化锂金属粉末)加入量为硅颗粒220含量的20％。
实施例4
本实施例与实施例1不同的地方在于：第一负极膜层200中硬碳颗粒210的含量与硅颗粒220含量之比为90:10。
实施例5
本实施例与实施例1不同的地方在于：第一负极膜层200中硬碳颗粒 210的粒径为2μm。
实施例6
本实施例与实施例1不同的地方在于：第一负极膜层200中硅颗粒220的D50的粒径为6μm，D90的粒径为18μm。
实施例7
本实施例与实施例1不同的地方在于：石墨颗粒310中D10的粒径为4μm，D50的粒径为11μm，D90的粒径为23μm。
实施例8
本实施例与实施例1不同的地方在于：石墨颗粒310中D10的粒径为4μm，D50的粒径为14μm，D90的粒径为28μm。
实施例9
本实施例与实施例1不同的地方在于：第一负极膜层200中未添加补锂剂。
对比例1
本实施例与实施例1不同的地方在于：负极膜层为一层结构，即活性物质包括硅颗粒220和石墨颗粒310，其混合后涂于负极集流体100上形成具有一层负极膜层的负极片。其中，石墨颗粒310中D10的粒径为6μm，D50的粒径为12μm，D90的粒径为25μm。
对比例2
本实施例与实施例1不同的地方在于：第一负极膜层200中的活性物质包括硅颗粒220和石墨颗粒310，第二负极膜层300中的活性物质包括石墨颗粒310，即第一负极膜层200和第二负极膜层300中的活性物质均包括石墨颗粒310。其中，石墨颗粒310的中D10的粒径为6μm，D50的粒径为12μm，D90的粒径为25μm。
对上述制备的每种电芯在25℃条件下进行1.2C阶梯充电/0.7C放电，并在不同循环次数下拆解电池确认电池负极表面析锂情况，拆解结果和能量密度如下：
表1给出实施例1-9和对比例1-2主要相关参数表
在表格中，负极片表面析锂程度用0、1、2、3、4、5来表示，0代表不析锂，5代表严重析锂，1、2、3、4代表不同的析锂程度，数字越大代表析锂程度越严重。
由表1可以看出，实施例1至实施例3是第一负极膜层200中补锂剂加入量而对负极片析锂情况的影响，即当补锂剂的加入量为5％和10％时，在锂离子电池经过500T(周期)的充放电时，负极片的表面均未有锂析出；当补锂剂的加入量达到20％时，在锂离子电池经过500T(周期)的充放电时，负极片的表面锂析出程度为1。
同时，还可以看出补锂剂的加入量对电池容量的保持率和膨胀率具有一定的影响。当补锂剂的加入量为10％、5％和20％时，在锂离子电池经过700T(周期)的充放电时，锂离子电池的容量保持率分别为87.04％、85.52％、82.65％；锂离子电池经过700T(周期)的充放电时，锂离子电池的膨胀率分别为9.17％、9.39％、9.54％。
在实施例9中，补锂剂的加入量为0，其在锂离子电池经过700T(周期)的充放电时，锂离子电池的容量保持率82.36％；锂离子电池经过700T(周期)的充放电时，锂离子电池的膨胀率分别为9.89％。
由上可知，通过添加补锂剂能够提高锂离子电池的容量保持率。但是， 当补锂剂加入过多是，会导致电池的容量保持率降低，膨胀率增大。由此，应加入适量的补锂剂才能够得到得到综合性能较优异的锂离子电池。
由实施例1和实施4可以看出，当第一负极膜层200中硅颗粒220与第一石墨颗粒310含量之比达到10：90时，锂离子电池经过电池经过500T(周期)的充放电时，负极片的表面锂析出程度为1。在锂离子电池经过700T(周期)的充放电时，锂离子电池的容量保持率为80.47％；锂离子电池经过700T(周期)的充放电时，锂离子电池的膨胀率分别为10.09％。
由此可知，当硅颗粒220含量较多时，会增大负极片表面析锂的程度，同时还能够降低锂离子电池的容量保持率，并能够增大锂离子电池的膨胀率。因此，选择加入适量的硅颗粒220才能够有效提高锂离子电池的综合性能。
由实施例1和实施例5可以看出，当第一负极膜层200中的硬碳颗粒210的粒径较大时，即硬碳颗粒210的粒径达到2μm时，锂离子电池经过电池经过500T(周期)的充放电时，负极片的表面锂析出程度为0。在锂离子电池经过700T(周期)的充放电时，锂离子电池的容量保持率为82.98％；锂离子电池经过700T(周期)的充放电时，锂离子电池的膨胀率分别为9.62％。
由此可知，当硬碳颗粒210较大时，会降低锂离子电池的容量保持率，并能够增大锂离子电池的膨胀率。因为，硬碳颗粒210的粒径较大时无法有效的包覆硅颗粒220，由此无法有效的改善硅颗粒220的动力学性能，即无法有效的改善锂离子电池的动力学性能。
由实施例1和实施例6可以看出，当第一负极膜层200中的硅颗粒220的粒径较小时，即硅颗粒220的粒径D50的粒径达到6μm、D90的粒径达到18μm时，即硅颗粒220的粒径相应减小时，锂离子电池经过电池经过500T(周期)的充放电时，负极片的表面锂析出程度为0。在锂离子电池经过700T(周期)的充放电时，锂离子电池的容量保持率为88.52％；锂离子电池经过700T(周期)的充放电时，锂离子电池的膨胀率分别为9.06％。
由此可知，硅颗粒220的粒径适当减小时，锂离子电池的析锂情况及体积膨胀率均未有明显变化，但是锂离子电池的容量保持率有一定的提升。因此，可以通过适当的减小硅颗粒220的粒径，能够使得锂离子电池在保持析锂情况及体积膨胀率基本不变的前提下，使其容量保持率提高。
由实施例1和实施例7可以看出，当第二负极膜层300中的碳颗粒的粒径较小时，即石墨颗粒310的粒径D10达到4μm、D50达到11μm、D90的粒径达到23μm时，锂离子电池经过电池经过500T(周期)的充放电时，负极片的表面锂析出程度为0。在锂离子电池经过700T(周期)的充放电时，锂离子电池的容量保持率为89.92％；锂离子电池经过700T(周期)的充放电时，锂离子电池的膨胀率分别为8.77％。
由此可知，石墨颗粒310的粒径适当减小时，锂离子电池的析锂情况及体积膨胀率均未有明显变化，但是锂离子电池的容量保持率有一定的提升。因此，可以通过适当的减小石墨颗粒310的粒径，能够使得锂离子电池在保持析锂情况及体积膨胀率基本不变的前提下，使其容量保持率提高。
由实施例1和实施例8可以看出，当第二负极膜层300中的碳颗粒的粒径较大时，即石墨颗粒310的粒径D10达到4μm、D50达到14μm、D90的粒径达到28μm时，锂离子电池经过电池经过500T(周期)的充放电时，负极片的表面锂析出程度为0。在锂离子电池经过700T(周期)的充放电时，锂离子电池的容量保持率为79.47％；锂离子电池经过700T(周期)的充放电时，锂离子电池的膨胀率分别为11.09％。
由此可知，当第二负极膜层300中碳颗粒的粒径较大时，锂离子电池的容量保持率呈较明显的下降趋势，同时体积膨胀率也呈交明显的增大趋势。因此，第二负极膜层300中的石墨颗粒310虽然粒径较大能够提高负极片的孔隙率，进而能够提高电芯保液量，降低负极片表面极化，提高负极片动力学性能，由此进一步提高了锂离子电池的电池的续航和寿命。但是，当其粒径过大时，会导致第二负极膜层300中的碳颗粒数量明显的减少，进而导致第二负极膜层300中嵌入的锂离子量明显降低，由此导致较多的锂离子聚集在硅颗粒220附近，从而影响了锂离子电池的容量保持率和膨胀率。
由对比例1可以看出，当将硅颗粒220和石墨颗粒310混合的浆料涂于负极集流体上形成一层负极膜层时，其锂离子电池经过电池经过500T(周期)的充放电时，负极片的表面锂析出程度为5；在锂离子电池经过700T(周期)的充放电时，锂离子电池的容量保持率为65.32％；锂离子电池经过700T(周期)的充放电时，锂离子电池的膨胀率分别为17.65％。
由此，通过实施例1至实施例7与对比例1相比较可知，通过采用本 公开实施例的结构能够有效的降低锂离子的析出程度，并能够明显的提高锂离子电池的容量保持率，降低锂离子电池的膨胀率。
由对比例2可以看出，当在第一负极膜层200和第二负极膜层300之间均选用石墨颗粒310，且石墨颗粒310未进行筛分时，锂离子电池经过电池经过500T(周期)的充放电时，负极片的表面锂析出程度为4；在锂离子电池经过700T(周期)的充放电时，锂离子电池的容量保持率为69.17％；锂离子电池经过700T(周期)的充放电时，锂离子电池的膨胀率分别为15.31％。
由此，由对比例2与对比例1相比较，虽然通过将负极膜层分成两层能够使得锂离子电池的综合性能有一定的改善，但是析锂情况仍然比较严重，同时锂离子电池的容量保持率仍较低，且锂离子电池的膨胀率较大。
进一步，通过实施例1至实施例9与对比例2相比较可知，通过采用本公开实施例的结构能够有效的降低锂离子的析出程度，并能够明显的提高锂离子电池的容量保持率，降低锂离子电池的膨胀率。即，通过将第一负极膜层200中的活性物质选用硬碳颗粒210和硅颗粒220，能够更加有效的提高负极片动力学性能，由此进一步提高了锂离子电池的电池的续航和寿命。
在本公开实施例的描述中，需要理解的是，术语“中心”、“纵向”、“横向”、“长度”、“宽度”、“厚度”、“上”、“下”、“前”、“后”、“左”、“右”、“竖直”、“水平”、“顶”、“底”“内”、“外”、“顺时针”、“逆时针”、“轴向”、“径向”、“周向”等指示的方位或位置关系为基于附图所示的方位或位置关系，仅是为了便于描述本公开实施例和简化描述，而不是指示或暗示所指的装置或元件必须具有特定的方位、以特定的方位构造和操作，因此不能理解为对本公开实施例的限制。
此外，术语“第一”、“第二”仅用于描述目的，而不能理解为指示或暗示相对重要性或者隐含指明所指示的技术特征的数量。由此，限定有“第一”、“第二”“第三”的特征可以明示或者隐含地包括至少一个该特征。在本公开实施例的描述中，“多个”的含义是至少两个，例如两个，三个等，除非另有明确具体的限定。
在本公开实施例中，除非另有明确的规定和限定，术语“安装”、“相连”、“连接”、“固定”等术语应做广义理解，例如，可以是固定连接，也可以是 可拆卸连接，或成一体；可以是机械连接，也可以是电连接；可以是直接相连，也可以通过中间媒介间接相连，可以是两个元件内部的连通或两个元件的相互作用关系，除非另有明确的限定。对于本领域的普通技术人员而言，可以根据具体情况理解上述术语在本公开实施例中的具体含义。
在本公开实施例中，除非另有明确的规定和限定，第一特征在第二特征“上”或“下”可以是第一和第二特征直接接触，或第一和第二特征通过中间媒介间接接触。而且，第一特征在第二特征“之上”、“上方”和“上面”可是第一特征在第二特征正上方或斜上方，或仅仅表示第一特征水平高度高于第二特征。第一特征在第二特征“之下”、“下方”和“下面”可以是第一特征在第二特征正下方或斜下方，或仅仅表示第一特征水平高度小于第二特征。
在本说明书的描述中，参考术语“一个实施例”、“一些实施例”、“示例”、“具体示例”、或“一些示例”等的描述意指结合该实施例或示例描述的具体特征、结构、材料或者特点包含于本公开实施例的至少一个实施例或示例中。在本说明书中，对上述术语的示意性表述不必须针对的是相同的实施例或示例。而且，描述的具体特征、结构、材料或者特点可以在任一个或多个实施例或示例中以合适的方式结合。此外，在不相互矛盾的情况下，本领域的技术人员可以将本说明书中描述的不同实施例或示例以及不同实施例或示例的特征进行结合和组合。
尽管上面已经示出和描述了本公开实施例的实施例，可以理解的是，上述实施例是示例性地，不能理解为对本公开实施例的限制，本领域的普通技术人员在本公开实施例的范围内可以对上述实施例进行变化、修改、替换和变型。

Claims (10)

  1. 一种负极片，其特征在于，包括，
    负极集流体；
    第一负极膜层，其贴于所述负极集流体的表面上；且所述第一负极膜层的活性物质包括硅颗粒和硬碳颗粒；且所述第一负极膜层包括补锂剂；
    第二负极膜层，其贴于所述第一负极膜层的表面上；且所述第二负极膜层的活性物质包括石墨颗粒。
  2. 根据权利要求1所述的负极片，其特征在于，所述补锂剂包括金属锂粉和/或过氧化锂。
  3. 根据权利要求1或2所述的负极片，其特征在于，所述硬碳颗粒的粒径小于所述硅颗粒的粒径，且所述硅颗粒的外壁被所述硬碳颗粒包覆。
  4. 根据权利要求1所述的负极片，其特征在于，所述第一负极膜层中的硅颗粒的D50的粒径为6μm-10μm、D90的粒径为18μm-22μm。
  5. 根据权利要求1所述的负极片，其特征在于，所述硬碳颗粒为球形颗粒，所述硬碳颗粒的粒径为0.5μm-2μm。
  6. 根据权利要求1所述的负极片，其特征在于，所述第二负极膜层中的石墨颗粒的D10的粒径为3μm-6μm、D50的粒径为11μm-14μm、D90的粒径为22μm<D90<29μm。
  7. 根据权利要求1-6任一项所述的负极片，其特征在于，所述石墨颗粒的D90的粒径与所述硅颗粒的D90的粒径之比为1.0-1.5。
  8. 根据权利要求1所述的负极片，其特征在于，所述第一负极膜层的厚度与所述第二负极膜层的厚度之比为1:9-9:1。
  9. 根据权利要求2所述的负极片，其特征在于，所述补锂剂与所述硅颗粒的质量比为1％～30％。
  10. 一种锂离子电池，其特征在于，其包括正极片、负极片、隔膜和电解液，所述负极片为以上权利要求1-9任一项所述的负极片。
PCT/CN2023/080005 2022-04-07 2023-03-07 负极片及锂离子电池 WO2023193562A1 (zh)

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