WO2021082291A1 - 负极材料、包括其的负极及负极的制备方法 - Google Patents

负极材料、包括其的负极及负极的制备方法 Download PDF

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WO2021082291A1
WO2021082291A1 PCT/CN2020/072938 CN2020072938W WO2021082291A1 WO 2021082291 A1 WO2021082291 A1 WO 2021082291A1 CN 2020072938 W CN2020072938 W CN 2020072938W WO 2021082291 A1 WO2021082291 A1 WO 2021082291A1
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negative electrode
silicon
electrode material
fluorinated
lithium
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PCT/CN2020/072938
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English (en)
French (fr)
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张成波
鲁宇浩
谢远森
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宁德新能源科技有限公司
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Priority to EP20883580.1A priority Critical patent/EP4040538A1/en
Publication of WO2021082291A1 publication Critical patent/WO2021082291A1/zh
Priority to US17/700,891 priority patent/US20220216465A1/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
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • 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
    • 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
    • H01M4/5835—Comprising fluorine or fluoride salts
    • 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
    • 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 relates to the field of electrochemistry, in particular to a negative electrode material, a negative electrode including the same, and a method for preparing the negative electrode.
  • silicon has an unusually high theoretical capacity, so in recent years, research on silicon as an anode material has exploded.
  • silicon is currently used as a negative electrode material, although it can increase the energy density, its cycle stability needs to be further improved.
  • the failure of silicon anode materials mainly stems from the following aspects: huge volume expansion after silicon intercalation; and the silicon surface has a high reaction activity with the electrolyte, which makes the thickness of the SEI solid interface film continue to increase, thereby continuously depleting reversible Lithium causes capacity degradation.
  • the present application provides a negative electrode material, a negative electrode including the same, and a preparation method of the negative electrode in an attempt to at least some extent solve at least one problem existing in the related field.
  • the present application provides a negative electrode material, which includes a silicon-containing material, wherein the negative electrode prepared from the negative electrode material is used as a working electrode, metal lithium is used as a counter electrode, and an electrolyte containing a lithium ion conductive material The constituted battery is charged and discharged.
  • the negative electrode material is delithiated
  • the ratio B/A of the maximum value B of the differential value dQ/dV between 0.4V-0.55V and the maximum value A of the differential value dQ/dV between 0.2V-0.35V is about 1.0-3.0.
  • the present application also provides a method for preparing a negative electrode, which includes: forming a negative electrode including a negative electrode material; and performing the steps of lithium insertion and delithiation on the negative electrode, wherein the negative electrode material includes a silicon-containing material.
  • the material includes at least one of pure silicon, silicon carbon, micron silicon alloy, or silicon oxide, wherein in the steps of lithium insertion and delithiation, the negative electrode is used as the working electrode, the metal lithium is used as the counter electrode, and the lithium ion conductive material is included.
  • a battery composed of an electrolyte is charged and discharged.
  • the ratio of the maximum value B of the differential value dQ/dV between 0.4V-0.55V and the maximum value A of the differential value dQ/dV between 0.2V-0.35V and B/A is about 1.0- 3.0.
  • the negative electrode material controls the lithium insertion depth of the negative electrode so that the ratio B/A is about 1.0-3.0.
  • the silicon-containing material includes at least one of pure silicon, silicon carbon, silicon alloy, or silicon oxide.
  • the ratio B/A is about 2.0-3.0.
  • silicon oxide is silicon oxide represented by the general formula SiO x , where 0 ⁇ x ⁇ 2.
  • At least a part of the outer surface of the SiO x particles is coated with carbon.
  • the median diameter of the SiO x particles is 1 ⁇ m ⁇ D50 ⁇ 10 ⁇ m.
  • the specific surface area of the SiO x particles is less than 5 m 2 /g.
  • the negative electrode material further includes a fluorocarbon
  • the fluorocarbon includes at least one of fluorinated graphite, fluorinated hard carbon, fluorinated soft carbon, fluorinated carbon tube, or fluorinated graphene.
  • the weight percentage of the fluorocarbon is less than or equal to about 20%.
  • the pure silicon includes at least one of microparticles, nanoparticles, nanowires, nanofilms, or nanospheres.
  • the present application also provides a negative electrode, which includes any one of the aforementioned negative electrode materials.
  • the present application also provides an electrochemical device, which includes any one of the foregoing negative electrodes.
  • the present application also provides an electronic device, which includes any one of the electrochemical devices described above.
  • FIG. 1 is a scanning electron microscope (SEM) image of negative electrode material particles including micron silicon and fluorinated graphite according to Example 1.
  • SEM scanning electron microscope
  • FIG. 2 is an SEM-EDS (Scanning Electron Microscope-Energy Spectrum) image of fluorine in the negative electrode material of Example 1.
  • SEM-EDS Scnning Electron Microscope-Energy Spectrum
  • FIG. 3 is an SEM-EDS image of carbon element in the negative electrode material of Example 1.
  • FIG. 4 is an SEM-EDS image of silicon element in the negative electrode material of Example 1.
  • Example 5 is a graph showing the V-dQ/dV curve of Example 1, Example 3 and Comparative Example 1 when delithiating the negative electrode.
  • FIG. 6 is a graph showing the delithiation curves of Example 1, Example 3 and Comparative Example 1.
  • FIG. 7 is a graph of the cycle performance of Example 1, Example 3 and Comparative Example 1.
  • FIG. 7 is a graph of the cycle performance of Example 1, Example 3 and Comparative Example 1.
  • the terms “approximately”, “substantially”, “substantially” and “about” are used to describe and illustrate small changes.
  • the term can refer to an example in which the event or situation occurs precisely and an example in which the event or situation occurs very closely.
  • the term can refer to a range of variation less than or equal to ⁇ 10% of the stated 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%.
  • the difference between two values is less than or equal to ⁇ 10% of the average value of the value (for example, 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%), then the two values can be considered "substantially" the same.
  • 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 the listed items Any combination of. For example, if items A and B are listed, then the phrase “at least one of A and B” means only A; only B; or A and B. In another example, if 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 (exclude B); B and C (exclude A); or all of A, B, and C.
  • Project A can contain a single component or multiple components.
  • Project B can contain a single component or multiple components.
  • Item C can contain a single component or multiple components.
  • this application charges and discharges the battery composed of the negative electrode material including the silicon-containing material as the working electrode, the metal lithium as the counter electrode, and the electrolyte containing the lithium ion conductive material, and draws A graph of the relationship (V-dQ/dV) between the differential value dQ/dV obtained by differentiating the charge and discharge capacity Q by the working electrode potential V and the working electrode potential V.
  • V-dQ/dV the maximum value of the differential value dQ/dV between about 0.2V and about 0.35V
  • the differential value dQ/dV between about 0.4V and about 0.55V is The maximum value is B.
  • the inventors of the present application discovered that by screening silicon-containing materials with a ratio B/A of about 1.0 to about 3.0, the cycle performance of the negative electrode material including silicon-containing materials can be significantly improved.
  • the inventors of the present application found that by selectively controlling the degree of lithium insertion of the negative electrode including the negative electrode material, so that the ratio B/A is about 1.0 to about 3.0, the cycle performance of the negative electrode material can be greatly improved.
  • the inventors of the present application discovered that the introduction of carbon fluoride into the negative electrode material including the silicon-containing material can further improve the cycle performance of the negative electrode material.
  • the application provides a negative electrode material, a negative electrode including the negative electrode material, and a preparation method of the negative electrode.
  • the present application also provides an electrochemical device and an electronic device including the negative electrode material.
  • the present application provides a negative electrode material, which includes a silicon-containing material, wherein the battery composed of the negative electrode material as a working electrode, metal lithium as a counter electrode, and an electrolyte containing lithium ion conductive material is between 0 and 2V.
  • the maximum value B of the differential value dQ/dV between about 0.4V-0.55V and about
  • the ratio B/A of the maximum value A of the differential value dQ/dV between 0.2V-0.35V is about 1.0-3.0.
  • the ratio B/A may be about 1.0-1.8, about 1.4-1.7, or about 2.0-2.5, for example, may be approximately 1.0, 1.2, 1.4, 1.6, 1.8, 2.0, 2.1, 2.2, 2.3, 2.4 , 2.5, 2.6, 2.7, 2.8, 2.9 and 3.0 or any two of these ratios.
  • the silicon-containing material includes at least one of pure silicon, silicon carbon, silicon alloy, or silicon oxide.
  • the silicon oxide is silicon oxide represented by the general formula SiO x , where 0 ⁇ x ⁇ 2.
  • the negative electrode material includes SiO x particles, and the median diameter of the SiO x particles is about 1 ⁇ m ⁇ D50 ⁇ about 10 ⁇ m.
  • the median diameter D50 of the SiO x particles may be about 2 ⁇ m, about 3 ⁇ m, about 4 ⁇ m, about 5 ⁇ m, about 6 ⁇ m, about 7 ⁇ m, about 8 ⁇ m, about 9 ⁇ m, or about 10 ⁇ m, or any two of these values.
  • the outer surface of the SiO x particles may be coated with carbon.
  • the specific surface area of the SiO x particles is less than about 5 m 2 /g.
  • the ratio of SiO x surface area of the particles of less than about 4m 2 / g, or about 2m 2 / g and the like.
  • the silicon-containing material includes pure silicon, and the pure silicon may be at least one of microparticles, random nanoparticles, nanowires, nanofilms, or nanospheres.
  • the silicon-containing material includes a silicon alloy
  • the silicon alloy includes at least one of a silicon-iron alloy, a silicon-aluminum alloy, a silicon-nickel alloy, or a silicon-iron-aluminum alloy.
  • the negative electrode material may further include fluorocarbon, and the fluorocarbon includes at least one of fluorinated graphite, fluorinated hard carbon, fluorinated soft carbon, fluorinated carbon tube, or fluorinated graphene.
  • the fluorocarbon may be on the surface of the silicon-containing material.
  • the carbon fluoride will react in situ around or on the surface of the silicon-containing material particles to form a graphene-like sheet layer and a lithium fluoride coating layer, and a graphene-like sheet layer
  • the conductivity of the negative electrode can be increased, and the lithium fluoride coating layer can be used as an SEI solid interface film and can protect the surface of the silicon-containing negative electrode active material particles, thereby further improving the cycle performance of the negative electrode material.
  • the weight percentage of the fluorocarbon is less than or equal to about 20%. In some embodiments, based on the total weight of the negative electrode material, the weight percentage of fluorocarbon is less than or equal to about 5%, less than or equal to about 10%, less than or equal to about 15%, from about 5% to about 10%. %, about 5% to about 15%, about 5% to about 15%, about 10% to about 20%, etc.
  • the present application provides a negative electrode, and the negative electrode includes any one of the aforementioned negative electrode materials.
  • the negative electrode in addition to the negative electrode material, may further include a binder.
  • the binder improves the bond between the particles of the negative electrode material and the bond between the negative electrode material and the current collector.
  • the binder includes, but is not limited to: polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyfluoro Ethylene, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene butadiene rubber, acrylic (ester) styrene butadiene Rubber, epoxy resin, nylon, etc.
  • the negative electrode in addition to the negative electrode material and the binder, may further include a conductive agent.
  • the conductive agent includes, but is not limited to, carbon-based materials, metal-based materials, conductive polymers, or mixtures thereof.
  • the carbon-based material is selected from natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or any combination thereof.
  • the metal-based material is selected from metal powder, metal fiber, copper, nickel, aluminum, silver.
  • the conductive polymer is a polyphenylene derivative.
  • the present application also provides a method for preparing a negative electrode, which includes: forming a negative electrode including a negative electrode material; and performing the steps of lithium insertion and delithiation on the negative electrode, wherein the negative electrode material includes a silicon-containing material, and the silicon-containing material It includes at least one of pure silicon, silicon carbon, silicon alloy, or silicon oxide, wherein in the steps of lithium insertion and delithiation, the negative electrode is used as a working electrode, metal lithium is used as a counter electrode, and lithium ion conductive A battery composed of an electrolyte of a sexual substance is charged and discharged.
  • the silicon-containing negative electrode material can be screened so that the ratio B/A is about 1.0 to about 3.0.
  • the negative electrode material whose screened ratio B/A is about 1.0 to about 3.0 is used to prepare the negative electrode, so that the negative electrode has good cyclability.
  • the ratio B/A can be about 1.0 to about 3.0 by controlling the lithium insertion depth of the negative electrode. By selectively controlling the lithium insertion depth of the negative electrode, the ratio B/A can still be about 1.0 to about 3.0 without screening the silicon-containing negative electrode material, so that the negative electrode has good cyclability.
  • a combination of screening silicon-containing negative electrode materials and controlling the lithium insertion depth of the negative electrode can be used to make the ratio B/A about 1.0 to about 3.0.
  • the step of forming a negative electrode including a negative electrode material includes: mixing a silicon-containing material and a fluorocarbon to form a negative electrode material, and homogenizing the negative electrode material with a conductive agent and a binder in a certain ratio to obtain a negative electrode slurry Then, the above-mentioned negative electrode slurry is coated on a negative electrode current collector (for example, a copper current collector), dried and rolled to obtain a negative electrode.
  • a negative electrode current collector for example, a copper current collector
  • controlling the lithium insertion depth of the negative electrode includes: determining a lithium insertion capacity Q1 of 100% SOC (State of Charge), selecting a suitable charging process and controlling the first charging capacity to x% Q1 to achieve Lithium insertion depth of x%SOC.
  • the embodiments of the present application also provide an electrochemical device including the anode material of the present application.
  • the electrochemical device may be any device that undergoes an electrochemical reaction, and specific examples thereof include all kinds of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors.
  • the electrochemical device is a lithium secondary battery, including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.
  • the electrochemical device includes the above-mentioned positive electrode, a negative electrode, and a separator provided between the positive electrode and the negative electrode.
  • the electrochemical device is a lithium ion battery.
  • the lithium ion battery includes a positive electrode containing a positive electrode material, a negative electrode containing a negative electrode material, an electrolyte, and a separator between the positive electrode and the negative electrode, wherein the negative electrode material is the above The negative electrode material.
  • the positive electrode current collector can be aluminum foil or nickel foil, and the negative electrode current collector can be copper foil or nickel foil.
  • the cathode material may include lithium cobalt oxide (LiCoO 2 ), lithium nickel cobalt manganese (NCM) ternary material, lithium iron phosphate (LiFePO 4 ), lithium manganese oxide (LiMn 2 O 4 ), or their random combination.
  • LiCoO 2 lithium cobalt oxide
  • NCM lithium nickel cobalt manganese
  • LiFePO 4 lithium iron phosphate
  • LiMn 2 O 4 lithium manganese oxide
  • the electrochemical device of the present application is provided with a separator between the positive electrode and the negative electrode to prevent short circuits.
  • the material and shape of the isolation membrane used in the electrochemical device of the present application are not particularly limited, and it may be any technology disclosed in the prior art.
  • the isolation membrane includes a polymer or an inorganic substance formed of a material that is stable to an electrolyte.
  • the electrochemical device manufactured from the anode material described in this application is suitable for electronic devices in various fields.
  • the electrochemical device of the present application is not particularly limited, and it can be used for any purpose known in the prior art.
  • the electrochemical device of the present application can be used in, but not limited to, notebook computers, pen-input computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, and headsets.
  • FIG. 1 is the negative electrode active material of Example 1 SEM image.
  • Figure 1 is the negative electrode active material of Example 1 SEM image.
  • Homogenize the negative electrode material at the ratio of negative electrode material: conductive agent: binder 8:1:1 to obtain negative electrode slurry, and then coat the obtained negative electrode slurry on a copper current collector, dry and roll it to obtain a negative electrode .
  • the prepared negative electrode and the metal lithium as the counter electrode are assembled with a button half-cell. Charge and discharge the assembled button half-cell, and control the lithium insertion depth of the negative electrode to 25% SOC.
  • Discharge at a constant current of 0.05C to 5mV then change to a current of 50 ⁇ A and continue to discharge to 5mV, and then discharge to 5mV with a current of 10 ⁇ A.
  • the discharge capacity at this time is regarded as the lithium insertion capacity Q of 100% SOC.
  • controlling the lithium insertion depth to 25% SOC can be achieved by inserting lithium at a constant current of 0.05C for 5 hours so that the first charging capacity is 25%Q.
  • Example 2 The preparation method of Example 2 is the same as that of Example 1, except that Example 2 controls the lithium insertion depth of the negative electrode to 35% SOC, and the ratio B/A is 1.06.
  • Example 3 The preparation method of Example 3 is the same as that of Example 1, except that Example 3 controls the lithium insertion depth of the negative electrode to 40% SOC, and the ratio B/A is 1.74.
  • Example 4 The preparation method of Example 4 is the same as that of Example 1, except that Example 4 controls the lithium insertion depth of the negative electrode to 43% SOC, and the ratio B/A is 1.4.
  • Example 5 The preparation method of Example 5 is the same as that of Example 1, except that Example 5 controls the lithium insertion depth of the negative electrode to 48% SOC, and the ratio B/A is 2.3.
  • Example 6 The preparation method of Example 6 is the same as that of Example 1, except that Example 6 controls the lithium insertion depth of the negative electrode to 50% SOC, and the ratio B/A is 1.
  • Example 7 The preparation method of Example 7 is the same as that of Example 1, except that Example 7 controls the lithium insertion depth of the negative electrode to 55% SOC, and the ratio B/A is 2.8.
  • Example 8 The preparation method of Example 8 is the same as that of Example 1, except that the negative electrode of Example 8 does not contain fluorinated graphite, and the lithium insertion depth of the negative electrode is controlled to 55% SOC, and the ratio B/A is 2.7.
  • Example 9 The preparation method of Example 9 is the same as that of Example 1, except that the negative electrode of Example 9 does not contain fluorinated graphite, and the lithium insertion depth of the negative electrode is controlled to 48% SOC, and the ratio B/A is 2.2.
  • Example 10 The preparation method of Example 10 is the same as that of Example 1, except that the negative electrode of Example 10 does not contain fluorinated graphite, and the lithium insertion depth of the negative electrode is controlled to 25% SOC, and the ratio B/A is 2.0.
  • Example 12 The preparation method of Example 12 is the same as that of Example 11. The difference is that Example 12 controls the lithium insertion depth of the negative electrode to 65% SOC, and the ratio B/A is 1.29.
  • Comparative Example 1 The preparation method of Comparative Example 1 is the same as that of Example 1, except that Comparative Example 1 controls the lithium insertion depth of the negative electrode to 73% SOC, and the ratio B/A is 0.84.
  • Comparative Example 2 The preparation method of Comparative Example 2 is the same as that of Example 1, except that Comparative Example 2 controls the lithium insertion depth of the negative electrode to 100% SOC, and the ratio B/A is 24.
  • Comparative Example 3 The preparation method of Comparative Example 3 is the same as that of Example 1, except that Comparative Example 3 controls the lithium insertion depth of the negative electrode to 10% SOC, and the ratio B/A is 0.4.
  • the prepared negative electrode and the metal lithium as the counter electrode are assembled with a button half-cell.
  • the assembled button half-cell was discharged to 5mV at a constant current at a rate of 0.05C, then changed to a current of 50 ⁇ A and continued to discharge to 5mV, and then discharged with a current of 10 ⁇ A to 5mV.
  • Comparative Example 2 (including 90% of the capacity in the same discharge process of the fluorinated graphite negative electrode) is recorded as 90% SOC. Plot the V-dQ/dV curve, energize the negative electrode in the delithiation direction at a rate of 0.05C, the differential value between 0.4V-0.55V and the maximum value B of dQ/dV and the differential value dQ/ between 0.2V-0.35V The ratio B/A of the maximum value A of dV is 10.
  • Comparative Example 5 The preparation method of Comparative Example 5 is the same as that of Example 11. The difference is that Comparative Example 5 controls the lithium insertion depth of the negative electrode to 85% SOC, and the ratio B/A is 0.60.
  • Example 6 The preparation method of Example 6 is the same as that of Example 11, except that Comparative Example 6 controls the lithium insertion depth of the negative electrode to 98% SOC, and the ratio B/A is 0.56.
  • the above charging and discharging cycle test was repeated for 20 cycles to test the cycle performance of the lithium ion battery.
  • the test results of Example 1 to Example 10 and Comparative Example 1 to Comparative Example 4 are shown in Table 1 below.
  • the test results of Example 11 and Example 12, and Comparative Example 5 and Comparative Example 6 are shown in Table 2 below.
  • the negative electrode material includes micron silicon and fluorinated graphite
  • controlling the lithium insertion depth of the negative electrode so that the ratio B/A is in the range of 1.0-3.0 can well improve the battery cycle. performance.
  • FIG. 1 is a scanning electron microscope (SEM) image of negative electrode material particles including micron silicon and fluorinated graphite according to Example 1.
  • FIG. Figures 2, 3, and 4 are SEM-EDS images of fluorine, carbon, and silicon in the negative electrode material of Example 1. Figures 2 to 4 illustrate that the surface of micron silicon is evenly coated with a layer of fluorine. Graphite material.
  • Figure 5 shows the V-dQ/dV curves of Example 1, Example 3 and Comparative Example 1 when the negative electrode was delithiated, where A represents the strongest peak between 0.2V-0.35V, and B represents 0.4 The strongest peak between V-0.55V.
  • Figure 6 shows the delithiation curves obtained by discharging the negative electrodes with a given lithium insertion depth of Example 1, Example 3 and Comparative Example 1, and Figure 6 illustrates that different B/A values have different delithiation capacities. This is related to controlling the lithium insertion capacity.
  • FIG. 7 shows the cycle performance curve diagram of 20 cycles of charging and discharging cycle test of Example 1, Example 3 and Comparative Example 1.
  • Example 1 As shown in Figure 7, comparing Example 1, Example 3 and Comparative Example 1, it can be seen that when the ratio B/A is in the range of 1.0-3.0, the discharge capacity retention rate after 20 cycles of the battery can still be maintained at Above 95%, the battery cycle performance of Examples 1 and 3 is significantly better than that of Comparative Example 1. This application significantly improves the cycle performance of the battery by controlling the B/A in the range of 1.0-3.0.
  • the test results in Table 2 show that silicon oxide (for example, SiO x particles) can also achieve similar effects to micron silicon. That is, when the negative electrode material includes silicon oxide and carbon fluoride, controlling the lithium insertion depth of the negative electrode so that the ratio B/A is in the range of 1.0-3.0 can well improve the cycle performance of the battery.
  • silicon oxide for example, SiO x particles
  • references to “some embodiments”, “partial embodiments”, “one embodiment”, “another example”, “examples”, “specific examples” or “partial examples” throughout the specification mean At least one embodiment or example in this application includes the specific feature, structure, material, or characteristic described in the embodiment or example. Therefore, descriptions appearing in various places throughout the specification, such as: “in some embodiments”, “in embodiments”, “in one embodiment”, “in another example”, “in an example “In”, “in a specific example” or “exemplified”, which are not necessarily quoting the same embodiment or example in this application.
  • the specific features, structures, materials or characteristics herein can be combined in one or more embodiments or examples in any suitable manner.

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Abstract

一种负极材料、包括其的负极及负极的制备方法。负极材料包括含硅材料，含硅材料包括纯硅、硅碳、硅合金、硅氧化物中的至少一种，负极材料中进一步包含碳氟化物。对由负极材料制备的负极作为工作电极、金属锂作为对电极和包含锂离子导电性物质的电解质构成的电池进行充放电，在绘制工作电极电势V对充放电容量Q进行微分而得到的微分值dQ/dV与工作电极电势V之间的关系曲线图的情况下，在对负极材料进行脱锂方向通电时，0.4V-0.55V之间的微分值dQ/dV的最大值B与0.2V-0.35V之间的微分值dQ/dV的最大值A的比值B/A为1.0-3.0。

Description

负极材料、包括其的负极及负极的制备方法 技术领域
本申请涉及电化学领域，具体地涉及一种负极材料、包括其的负极及负极的制备方法。
背景技术
随着便携式电子产品及通讯电子设备等的快速发展，对具有高能量密度的二次电池的需求日益迫切。相比于传统的石墨类负极材料，硅具有异常高的理论容量，所以近年来，对硅作为负极材料的研究呈爆发式增长。当前硅作为负极材料，虽然能使能量密度得以提高，但其循环稳定性还有待进一步改进。硅负极材料的失效主要源于以下几个方面：硅嵌锂后巨大的体积膨胀；以及硅表面与电解液具有较高的反应活性，使得SEI固体界面膜的厚度持续增加，从而不断地消耗可逆锂，导致容量衰减。
因此，开发一种能量密度高且循环性能优异的负极材料迫在眉睫。
发明内容
本申请提供一种负极材料、包括其的负极及负极的制备方法以试图在至少某种程度上解决至少一个存在于相关领域中的问题。
根据本申请的实施例，本申请提供了一种负极材料，其包括：含硅材料，其中，对由负极材料制备的负极作为工作电极、金属锂作为对电极和包含锂离子导电性物质的电解质构成的电池进行充放电，在绘制工作电极电势V对充放电容量Q进行微分而得到的微分值dQ/dV与工作电极电势V之间的关系曲线图的情况下，在对负极材料进行脱锂方向通电时，0.4V-0.55V之间的微分值dQ/dV的最大值B与0.2V-0.35V之间的微分值dQ/dV的最大值A的比值B/A为约1.0-3.0。
根据本申请的实施例，本申请还提供了一种负极的制备方法，其包括：形成包括负极材料的负极；对负极进行嵌锂和脱锂的步骤，其中负极材料包括含硅材料，含硅材料包括纯硅、硅碳、微米硅合金或硅氧化物中的至少一种，其中在嵌锂和脱锂的步骤中， 将负极作为工作电极、金属锂作为对电极和包含锂离子导电性物质的电解质构成的电池进行充放电，在绘制工作电极电势V对充放电容量Q进行微分而得到的微分值dQ/dV与工作电极电势V之间的关系曲线图的情况下，在对负极材料进行脱锂方向通电时，0.4V-0.55V之间的微分值dQ/dV的最大值B与0.2V-0.35V之间的微分值dQ/dV的最大值A的比值B/A为约1.0-3.0。
根据本申请的实施例，负极材料通过控制负极的嵌锂深度使比值B/A为约1.0-3.0。
根据本申请的实施例，含硅材料包括纯硅、硅碳、硅合金或硅氧化物中的至少一种。
根据本申请的实施例，当含硅材料包括硅氧化物时，比值B/A为约2.0-3.0。
根据本申请的实施例，硅氧化物是以通式SiO x所表示的氧化硅，其中0＜x＜2。
根据本申请的实施例，SiO x颗粒的外表面的至少一部分包覆有碳。
根据本申请的实施例，SiO x颗粒的中位径1μm＜D50＜10μm。
根据本申请的实施例，SiO x颗粒的比表面积小于5m 2/g。
根据本申请的实施例，负极材料还包括碳氟化物，碳氟化物包含氟化石墨、氟化硬碳、氟化软碳、氟化碳管或氟化石墨烯中的至少一种。
根据本申请的实施例，基于负极材料的总重量，碳氟化物的重量百分含量小于或等于约20％。
根据本申请的实施例，所述纯硅包括微米颗粒、纳米颗粒、纳米线、纳米薄膜或纳米球中的至少一种。
根据本申请的实施例，本申请还提供了一种负极，其包括上述任意一种负极材料。
根据本申请的实施例，本申请还提供了一种电化学装置，其包括上述任意一种负极。
根据本申请的实施例，本申请还提供了一种电子装置，其包括上述任意一种电化学装置。
本申请实施例的额外层面及优点将部分地在后续说明中描述、显示、或是经由本申请实施例的实施而阐释。
附图说明
在下文中将简要地说明为了描述本申请实施例或现有技术所必要的附图以便于描述本申请的实施例。显而易见地，下文描述中的附图仅只是本申请中的部分实施例。对本领域技术人员而言，在不需要创造性劳动的前提下，依然可以根据这些附图中所例示的结构来获得其他实施例的附图。
图1是根据实施例1的包括微米硅和氟化石墨的负极材料颗粒的扫描电子显微镜(SEM)图。
图2是关于实施例1的负极材料的氟元素的SEM-EDS(扫描电子显微镜-能谱)图。
图3是关于实施例1的负极材料的碳元素的SEM-EDS图。
图4是关于实施例1的负极材料的硅元素的SEM-EDS图。
图5是实施例1、实施例3和对比例1的对负极进行脱锂时的V-dQ/dV曲线图。
图6是实施例1、实施例3和对比例1的脱锂曲线图。
图7是实施例1、实施例3和对比例1的循环性能曲线图。
具体实施方式
本申请的实施例将会被详细的描示在下文中。在本申请说明书全文中，将相同或相似的组件以及具有相同或相似的功能的组件通过类似附图标记来表示。在此所描述的有关附图的实施例为说明性质的、图解性质的且用于提供对本申请的基本理解。本申请的实施例不应该被解释为对本申请的限制。
如本文中所使用，术语“大致”、“大体上”、“实质”及“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％。举例来说，如果两个数值之间的差值小于或等于所述值的平均值的±10％(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％)，那么可认为所述两个数值“大体上”相同。
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。
在具体实施方式及权利要求书中，由术语“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。
为了探究包括含硅材料的负极材料的循环性能，本申请对包括含硅材料的负极材料作为工作电极、金属锂作为对电极和包含锂离子导电性物质的电解质构成的电池进行充放电，并绘制工作电极电势V对充放电容量Q进行微分而得到的微分值dQ/dV与所述工作电极电势V之间的关系(V-dQ/dV)曲线图。在对所述负极材料进行脱锂方向通电时，约0.2V-约0.35V之间的微分值dQ/dV的最大值为A，约0.4V-约0.55V之间的微分值dQ/dV的最大值为B。
本申请的发明人研究发现，通过筛选比值B/A为约1.0-约3.0的含硅材料，可以使得包括含硅材料的负极材料的循环性能显著提高。
本申请的发明人研究发现，通过有选择地控制包括所述负极材料的负极的嵌锂程度，使得比值B/A为约1.0-约3.0，可以极大地改善负极材料的循环性能。
另外，本申请的发明人研究发现，在包括含硅材料的负极材料中引入碳氟化物，可以进一步改善负极材料的循环性能。
下面将详细描述本申请的发明，但本申请不限于以下说明。
本申请提供了一种负极材料、包括所述负极材料的负极及负极的制备方法。并且，本申请还提供了包括所述负极材料的电化学装置和电子装置。
一、负极材料
本申请提供了一种负极材料，其包括含硅材料，其中，对由所述负极材料作为工作电极、金属锂作为对电极和包含锂离子导电性物质的电解质构成的电池在0-2V之间进 行充放电，在绘制V-dQ/dV曲线图的情况下，在对所述负极材料进行脱锂方向通电时，约0.4V-0.55V之间的微分值dQ/dV的最大值B与约0.2V-0.35V之间的微分值dQ/dV的最大值A的比值B/A为约1.0-3.0。
在一些实施例中，比值B/A可以为约1.0-1.8、约1.4-1.7或约2.0-2.5，例如可以大致为1.0、1.2、1.4、1.6、1.8、2.0、2.1、2.2、2.3、2.4、2.5、2.6、2.7、2.8、2.9和3.0或这些比值中任意两个组成的范围。
在一些实施例中，含硅材料包括纯硅、硅碳、硅合金或硅氧化物中的至少一种。在一些实施例中，硅氧化物是以通式SiO x所表示的氧化硅，其中0＜x＜2。在一些实施例中，负极材料包括SiO x颗粒，所述SiO x颗粒的中位径约1μm＜D50＜约10μm。例如，在一些实施例中，SiO x颗粒的中位径D50可以是约2μm、约3μm、约4μm、约5μm、约6μm、约7μm、约8μm、约9μm或约10μm或这些值中任意两个组成的范围。在一些实施例中，所述SiO x颗粒的外表面的至少一部分可以被碳包覆。在一些实施例中，所述SiO x颗粒的比表面积小于约5m 2/g。例如，在一些实施例中，SiO x颗粒的比表面积小于约4m 2/g或约2m 2/g等。
在一些实施例中，含硅材料包括纯硅，纯硅可以是微米颗粒、无规则的纳米颗粒、纳米线、纳米薄膜或纳米球中的至少一种。
在一些实施例中，含硅材料包括硅合金，所述硅合金包括硅铁合金、硅铝合金、硅镍合金或硅铁铝合金中的至少一种。
在一些实施例中，负极材料还可以包括碳氟化物，碳氟化物包含氟化石墨、氟化硬碳、氟化软碳、氟化碳管或氟化石墨烯中的至少一种。在一些实施例中，碳氟化物可以在含硅材料的表面。在对包括负极材料的负极首次充电或嵌锂的过程中，碳氟化物会在含硅材料颗粒周围或表面原位反应生成类石墨烯片层及氟化锂包覆层，类石墨烯片层可以增加负极的导电性，而氟化锂包覆层可以作为SEI固体界面膜并且可以对含硅负极活性物质颗粒的表面起到保护作用，因此进一步改善了负极材料的循环性能。
在一些实施例中，基于负极材料的总重量，碳氟化物的重量百分含量小于或等于约20％。在一些实施例中，基于所述负极材料的总重量，碳氟化物的重量百分含量小于或等于约5％、小于或等于约10％、小于或等于约15％、约5％-约10％、约5％-约15％、约5％-约15％、约10％-约20％等。
二、负极及其制备方法
本申请提供了一种负极，所述负极包括上述任意一种负极材料。
在一些实施例中，除了负极材料，负极还可以包括粘结剂。粘合剂提高负极材料颗粒彼此间的结合和负极材料与集流体的结合。在一些实施例中，粘合剂包括，但不限于：聚乙烯醇、羧甲基纤维素、羟丙基纤维素、二乙酰基纤维素、聚氯乙烯、羧化的聚氯乙烯、聚氟乙烯、含亚乙基氧的聚合物、聚乙烯吡咯烷酮、聚氨酯、聚四氟乙烯、聚偏1，1-二氟乙烯、聚乙烯、聚丙烯、丁苯橡胶、丙烯酸(酯)化的丁苯橡胶、环氧树脂、尼龙等。
在一些实施例中，除了负极材料和粘结剂，负极还可以包括导电剂。导电剂包括但不限于基于碳的材料、基于金属的材料、导电聚合物或它们的混合物。在一些实施例中，基于碳的材料选自天然石墨、人造石墨、碳黑、乙炔黑、科琴黑、碳纤维或其任意组合。在一些实施例中，基于金属的材料选自金属粉、金属纤维、铜、镍、铝、银。在一些实施例中，导电聚合物为聚亚苯基衍生物。本申请还提供了一种负极的制备方法，其包括：形成包括负极材料的负极；对所述负极进行嵌锂和脱锂的步骤，其中所述负极材料包括含硅材料，所述含硅材料包括纯硅、硅碳、硅合金或硅氧化物中的至少一种，其中在所述嵌锂和脱锂的步骤中，将所述负极作为工作电极、金属锂作为对电极和包含锂离子导电性物质的电解质构成的电池进行充放电，在绘制V-dQ/dV曲线图的情况下，在对所述负极材料进行脱锂方向通电时，0.4V-0.55V之间的微分值dQ/dV的最大值B与0.2V-0.35V之间的微分值dQ/dV的最大值A的比值B/A为1.0-3.0。
在一些实施例中，可以通过筛选含硅负极材料，使得比值B/A为约1.0-约3.0。将这种筛选的比值B/A为约1.0-约3.0的负极材料用于制备负极，从而使负极具有良好的循环性。
在一些实施例中，可以通过控制所述负极的嵌锂深度使比值B/A为约1.0-约3.0。通过有选择地控制负极的嵌锂深度，可以在不筛选含硅负极材料的情况下依旧使比值B/A为约1.0-约3.0，从而使负极具有良好的循环性。
在一些实施例中，还可以通过采用筛选含硅负极材料和控制负极的嵌锂深度两种手段相结合的方式来使比值B/A为约1.0-约3.0。
在一些实施例中，形成包括负极材料的负极的步骤包括：混合含硅材料和碳氟化物以形成负极材料，按一定的比例将负极材料与导电剂和粘结剂进行匀浆以到负极浆料，然后将上述负极浆料涂覆在负极集流体(例如，铜集流体)上，进行烘干并进行辊压，得到负极。
在一些实施例中，控制所述负极的嵌锂深度包括：确定100％SOC(State of Charge，电荷状态)的嵌锂容量Q1，选择合适的充电流程并控制首次充电容量为x％Q1以实现x％SOC的嵌锂深度。
三、电化学装置
本申请的实施例还提供了包括本申请的负极材料的电化学装置。所述电化学装置可以是发生电化学反应的任何装置，它的具体实例包括所有种类的一次电池、二次电池、燃料电池、太阳能电池或电容。特别地，该电化学装置是锂二次电池，包括锂金属二次电池、锂离子二次电池、锂聚合物二次电池或锂离子聚合物二次电池。所述电化学装置包括上述正极、负极以及设置在正极和负极之间的隔离膜。
在一些实施例中，所述电化学装置为锂离子电池，锂离子电池包括含有正极材料的正极、含有负极材料的负极、电解质以及位于正极和负极之间的隔离膜，其中负极材料为上文所述负极材料。正极集流体可以为铝箔或镍箔，负极集流体可为铜箔或镍箔。
在一些实施例中，正极材料可以包括钴酸锂(LiCoO 2)、锂镍钴锰(NCM)三元材料、磷酸亚铁锂(LiFePO 4)、锰酸锂(LiMn 2O 4)或它们的任意组合。
在一些实施例中，本申请的电化学装置在正极与负极之间设有隔离膜以防止短路。本申请的电化学装置中使用的隔离膜的材料和形状没有特别限制，其可为任何现有技术中公开的技术。在一些实施例中，隔离膜包括由对电解液稳定的材料形成的聚合物或无机物等。
四、电子装置
由本申请所述的负极材料制造的电化学装置适用于各种领域的电子装置。
本申请的电化学装置的用途没有特别限定，其可用于现有技术中已知的任何用途。在一个实施例中，本申请的电化学装置可用于，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。
五、实施例
以下，举出实施例和对比例对本申请进一步具体地进行说明，但只要不脱离其主旨，则本申请并不限定于这些实施例。
实施例1
将10克微米硅(D50约4μm)与0.5克氟化石墨(即氟化石墨的质量百分含量为4.8％)经球磨混合后以形成负极材料(图1为实施例1的负极活性物质的SEM图)。按负极材料∶导电剂∶粘结剂＝8∶1∶1的比例进行匀浆得到负极浆料，然后将所得负极浆料涂覆在铜集流体上，进行烘干并进行辊压，得到负极。将制备的负极与作为对电极的金属锂进行扣式半电池组装。对组装后的扣式半电池进行充放电，控制负极的嵌锂深度为25％SOC。绘制V-dQ/dV曲线图，对负极进行0.05C倍率脱锂方向通电，0.4V-0.55V之间的微分值dQ/dV的最大值B与0.2V-0.35V之间的微分值dQ/dV的最大值A的比值B/A为2.14。
以0.05C的倍率恒流放电至5mV，然后改为50μA的电流继续放电至5mV，再用10μA的电流放电至5mV，此时的放电容量作为100％SOC的嵌锂容量Q。可以采用多种方式控制嵌锂深度。例如，控制嵌锂深度为25％SOC可以通过在固定电流为0.05C倍率下恒流嵌锂5小时以使首次充电容量为25％Q来实现。
实施例2
实施例2与实施例1的制备方法一致，不同之处在于实施例2控制负极的嵌锂深度为35％SOC，比值B/A为1.06。
实施例3
实施例3与实施例1的制备方法一致，不同之处在于实施例3控制负极的嵌锂深度为40％SOC，比值B/A为1.74。
实施例4
实施例4与实施例1的制备方法一致，不同之处在于实施例4控制负极的嵌锂深度为43％SOC，比值B/A为1.4。
实施例5
实施例5与实施例1的制备方法一致，不同之处在于实施例5控制负极的嵌锂深度为48％SOC，比值B/A为2.3。
实施例6
实施例6与实施例1的制备方法一致，不同之处在于实施例6控制负极的嵌锂深度为50％SOC，比值B/A为1。
实施例7
实施例7与实施例1的制备方法一致，不同之处在于实施例7控制负极的嵌锂深度为55％SOC，比值B/A为2.8。
实施例8
实施例8与实施例1的制备方法一致，不同之处在于实施例8负极中不含氟化石墨，且控制负极的嵌锂深度为55％SOC，比值B/A为2.7。
实施例9
实施例9与实施例1的制备方法一致，不同之处在于实施例9负极中不含氟化石墨，且控制负极的嵌锂深度为48％SOC，比值B/A为2.2。
实施例10
实施例10与实施例1的制备方法一致，不同之处在于实施例10负极中不含氟化石墨，且控制负极的嵌锂深度为25％SOC，比值B/A为2.0。
实施例11
将10克SiO x(0＜x＜2，D50为6μm，比表面积为2m 2/g)与0.5克氟化石墨(即氟化石墨的质量百分含量为4.8％)经球磨混合后以形成负极材料。按负极材料∶导电剂∶粘结剂＝8∶1∶1的比例进行匀浆得到负极浆料，然后将所得负极浆料涂覆在铜集流体上，进行烘干并进行辊压，得到负极。将制备的负极与作为对电极的金属锂进行扣式半电池组装。对组装后的扣式半电池进行充放电，控制负极的嵌锂深度为50％SOC。绘制V-dQ/dV曲线图，对负极进行0.05C倍率脱锂方向通电，0.4V-0.55V之间的微分值dQ/dV的最大值B与0.2V-0.35V之间的微分值dQ/dV的最大值A的比值B/A为2。
实施例12
实施例12与实施例11的制备方法一致，不同之处在于实施例12控制负极的嵌锂深度为65％SOC，比值B/A为1.29。
对比例1
对比例1与实施例1的制备方法一致，不同之处在于对比例1控制负极的嵌锂深度 为73％SOC，比值B/A为0.84。
对比例2
对比例2与实施例1的制备方法一致，不同之处在于对比例2控制负极的嵌锂深度为100％SOC，比值B/A为24。
对比例3
对比例3与实施例1的制备方法一致，不同之处在于对比例3控制负极的嵌锂深度为10％SOC，比值B/A为0.4。
对比例4
将10克微米硅(D50约4μm)作为负极材料，按负极材料∶导电剂∶粘结剂＝8∶1∶1的比例进行匀浆得到负极浆料，然后将所得负极浆料涂覆在铜集流体上，进行烘干并进行辊压，得到负极。将制备的负极与作为对电极的金属锂进行扣式半电池组装。对组装后的扣式半电池以0.05C的倍率恒流放电至5mV，然后改为50μA的电流继续放电至5mV，再用10μA的电流放电至5mV，此时的放电容量为对比例2(包含氟化石墨的负极)的相同放电流程时容量的90％，记为90％SOC。绘制V-dQ/dV曲线图，对负极进行0.05C倍率脱锂方向通电，0.4V-0.55V之间的微分值dQ/dV的最大值B与0.2V-0.35V之间的微分值dQ/dV的最大值A的比值B/A为10。
对比例5
对比例5与实施例11的制备方法一致，不同之处在于对比例5控制负极的嵌锂深度为85％SOC，比值B/A为0.60。
对比例6
实施例6与实施例11的制备方法一致，不同之处在于对比例6控制负极的嵌锂深度为98％SOC，比值B/A为0.56。
电池的测试方法和结果
对给定嵌锂深度的实施例1-实施例12和对比例1-对比例6进行放电以得到相应的电压V1，然后以0.05C的倍率恒流放电至对应的电压V1，再改为50μA电流进行放电至此电压V1，最后使用10μA电流进行放电至此电压V1结束放电；以0.05C的倍率恒流充电至1.2V即完成1个充放电循环。重复进行上述充放电循环测试20圈以测试锂离子电池的循环性能。实施例1-实施例10和对比例1-对比例4的测试结果如下表1所示。 实施例11和实施例12以及对比例5和对比例6的测试结果如下表2所示。
表1
Figure PCTCN2020072938-appb-000001
表2
Figure PCTCN2020072938-appb-000002
根据表1的测试结果可以得知，当负极材料包括微米硅和氟化石墨时，控制负极的嵌锂深度，使比值B/A在1.0-3.0的范围内，可以很好地改善电池的循环性能。
图1是根据实施例1的包括微米硅和氟化石墨的负极材料颗粒的扫描电子显微镜(SEM)图。图2、图3和图4分别是关于实施例1的负极材料的氟元素、碳元素和硅元素的SEM-EDS图，图2至图4说明微米硅的表面均匀地包覆了一层氟化石墨材料。
图5示出了实施例1、实施例3和对比例1的对负极进行脱锂时的V-dQ/dV曲线图，其中A代表0.2V-0.35V之间的最强峰，B代表0.4V-0.55V之间的最强峰。图6示出了 对实施例1、实施例3和对比例1的给定嵌锂深度的负极进行放电所得的脱锂曲线图，图6说明了不同的B/A值具有不同的脱锂容量，这与控制嵌锂容量有关。图7示出了对实施例1、实施例3和对比例1进行充放电循环测试20圈的循环性能曲线图。如图7所示，对比实施例1、实施例3和对比例1可以得知，当比值B/A在1.0-3.0的范围内时，电池循环20圈后的放电容量保持率仍可以保持在95％以上，实施例1和3的电池循环性能明显优于对比例1。本申请通过控制B/A在1.0-3.0的范围内，显著地提高电池的循环性能。
表2的测试结果表明，硅氧化物(例如，SiO x颗粒)也可以实现与微米硅相似的效果。即，当负极材料包括硅氧化物和碳氟化物时，控制负极的嵌锂深度，使比值B/A在1.0-3.0的范围内，可以很好地改善电池的循环性能。
整个说明书中对“一些实施例”、“部分实施例”、“一个实施例”、“另一举例”、“举例”、“具体举例”或“部分举例”的引用，其所代表的意思是在本申请中的至少一个实施例或举例包含了该实施例或举例中所描述的特定特征、结构、材料或特性。因此，在整个说明书中的各处所出现的描述，例如：“在一些实施例中”、“在实施例中”、“在一个实施例中”、“在另一个举例中”，“在一个举例中”、“在特定举例中”或“举例“，其不必然是引用本申请中的相同的实施例或示例。此外，本文中的特定特征、结构、材料或特性可以以任何合适的方式在一个或多个实施例或举例中结合。
尽管已经演示和描述了说明性实施例，本领域技术人员应该理解上述实施例不能被解释为对本申请的限制，并且可以在不脱离本申请的精神、原理及范围的情况下对实施例进行改变，替代和修改。

Claims (15)

  1. 一种负极材料，其包括：含硅材料，
    其中，对由所述负极材料制备的负极作为工作电极、金属锂作为对电极和包含锂离子导电性物质的电解质构成的电池进行充放电，在绘制工作电极电势V对充放电容量Q进行微分而得到的微分值dQ/dV与所述工作电极电势V之间的关系曲线图的情况下，在对所述负极材料进行脱锂方向通电时，0.4V-0.55V之间的微分值dQ/dV的最大值B与0.2V-0.35V之间的微分值dQ/dV的最大值A的比值B/A为1.0-3.0。
  2. 根据权利要求1所述的负极材料，所述含硅材料包括纯硅、硅碳、硅合金或硅氧化物中的至少一种。
  3. 根据权利要求2所述的负极材料，所述硅氧化物是以通式SiO x所表示的氧化硅，其中0＜x＜2。
  4. 根据权利要求3所述的负极材料，所述SiO x颗粒的外表面的至少一部分包覆有碳。
  5. 根据权利要求3所述的负极材料，所述SiO x颗粒的中位径1μm＜D50＜10μm。
  6. 根据权利要求3所述的负极材料，所述SiO x颗粒的比表面积小于5m 2/g。
  7. 根据权利要求1所述的负极材料，其还包括碳氟化物，所述碳氟化物是氟化石墨、氟化硬碳、氟化软碳、氟化碳管或氟化石墨烯中的至少一种。
  8. 根据权利要求7所述的负极材料，基于所述负极材料的总重量，所述碳氟化物的重量百分含量小于或等于20％。
  9. 根据权利要求2所述的负极材料，所述纯硅包括微米颗粒、纳米颗粒、纳米线、纳米薄膜或纳米球中的至少一种。
  10. 一种负极，其包括如权利要求1-9任一项所述的负极材料。
  11. 一种电化学装置，其包括如权利要求10所述的负极。
  12. 一种电子装置，其包括如权利要求11所述的电化学装置。
  13. 一种负极的制备方法，其包括：
    形成包括负极材料的负极；
    对所述负极进行嵌锂和脱锂的步骤，
    其中所述负极材料包括含硅材料，所述含硅材料包括包括纯硅、硅碳、硅合金或硅氧化物中的至少一种，
    其中在所述嵌锂和脱锂的步骤中，将所述负极作为工作电极、金属锂作为对电极和包含锂离子导电性物质的电解质构成的电池进行充放电，在绘制工作电极电势V对充放电容量Q进行微分而得到的微分值dQ/dV与所述工作电极电势V之间的关系曲线图的情况下，在对所述负极材料进行脱锂方向通电时，0.4V-0.55V之间的微分值dQ/dV的最大值B与0.2V-0.35V之间的微分值dQ/dV的最大值A的比值B/A为1.0-3.0。
  14. 根据权利要求13所述的制备方法，其中所述负极材料通过控制所述负极的嵌锂深度使比值B/A为1.0-3.0。
  15. 根据权利要求13所述的制备方法，其中所述负极材料还包括碳氟化物，所述碳氟化物是氟化石墨、氟化硬碳、氟化软碳、氟化碳管或氟化石墨烯中的至少一种，基于所述负极材料的总重量，所述碳氟化物的重量百分含量小于或等于20％。
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