WO2023213122A1 - 用于锂电池的负极片及包含其的锂离子二次电池 - Google Patents

用于锂电池的负极片及包含其的锂离子二次电池 Download PDF

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WO2023213122A1
WO2023213122A1 PCT/CN2023/078541 CN2023078541W WO2023213122A1 WO 2023213122 A1 WO2023213122 A1 WO 2023213122A1 CN 2023078541 W CN2023078541 W CN 2023078541W WO 2023213122 A1 WO2023213122 A1 WO 2023213122A1
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negative electrode
electrode sheet
silicon oxide
graphite
battery
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French (fr)
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周燕
王丽
李于利
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Murata Manufacturing Co Ltd
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Murata Manufacturing Co Ltd
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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
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
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    • 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
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • 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
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • H—ELECTRICITY
    • 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
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—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
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • 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 invention relates to the field of lithium-ion secondary batteries, and specifically, to a negative electrode sheet for a lithium-ion battery and a lithium-ion secondary battery containing the same.
  • the existing technology has combined graphite and silicon oxide as the negative active material, and the silicon oxide used is carbon-coated silicon oxide.
  • silicone oxide After silicone oxide is coated with carbon, it improves the first efficiency and cycle performance of lithium-ion batteries to a certain extent, but correspondingly reduces the first capacity of the battery, increases the negative electrode expansion effect of the battery, and increases the material cost, and silicone oxide
  • the uniformity of the silicon-carbon coating layer is difficult to control, resulting in increased side reactions between the battery negative electrode and the electrolyte.
  • the main purpose of the present invention is to provide a negative electrode sheet for lithium batteries and a lithium ion secondary battery containing the same, so as to solve the problem of using the negative electrode sheet of the existing technology to cause the capacity and cycle performance of the lithium ion battery to decrease, and the negative electrode expansion rate to be relatively high. Big question.
  • the present invention provides a negative electrode sheet for a lithium battery.
  • the negative electrode sheet includes a current collector and a negative electrode material.
  • the negative electrode material includes graphite, oxide without carbon coating. Silicon SiOx and conductive agent containing carbon nanotubes, where 1.6>x>0.
  • the silicon oxide is in an amorphous state or a low crystalline state.
  • the content of SiO 2 in the silicon oxide is ⁇ 55% by mole (changed from 60% to ⁇ 55%), preferably ⁇ 45%.
  • the size of Si crystals in the silicone oxide is ⁇ 5 nm, preferably ⁇ 1nm.
  • the XRD half-peak width of the SiO 2 crystal in the silicon oxide at 2 ⁇ is 26-27° is less than 1.5°.
  • the particle size D 50 of silicon oxide is 1 ⁇ m ⁇ D 50 ⁇ 10 ⁇ m, and when the particle size D 50 of silicon oxide is 4 ⁇ m ⁇ D 50 ⁇ 10 ⁇ m, particles with a particle size ⁇ 2 ⁇ m Accounting for 20%-50%, or when the particle size D50 of silica is 2 ⁇ m ⁇ D50 ⁇ 4 ⁇ m, particles with a particle size ⁇ 2 ⁇ m account for 70%-80%.
  • the specific surface area of silicon oxide is 1-5 m 2 /g.
  • the length of the carbon nanotubes is 1-30 ⁇ m and the diameter is 1-20 ⁇ m, wherein the aspect ratio of the carbon nanotubes is 1:1-10:1, preferably 3:1-10:1. .
  • the amount of carbon nanotubes in the negative electrode material is 0.005%-1% by weight, preferably 0.02%-0.2%.
  • the graphite in the negative electrode sheet is selected from natural graphite, artificial graphite or their mixture, and the D/G of the graphite is in the range of 0.04-1, preferably 0.3-0.9,
  • the electrical conductivity of graphite is >1s/cm when the bulk density is 1.6-1.7g/ cm3 , and >40s/cm when the bulk density is 2.2.-2.3g/cm3.
  • the negative electrode sheet also contains a binder, the binder includes PVDF, PAA, SBR, CMC binder or a combination thereof, based on the total solid weight of the negative electrode material, the binder The amount of the agent in the negative electrode material is 2% to 4% by weight.
  • the conductive agent also includes conductive carbon black, conductive graphite, vapor-grown carbon fiber or a combination thereof. Based on the total solid weight of the negative electrode material, the amount of the conductive agent in the negative electrode material is 1 by weight. %-3%.
  • a lithium ion secondary battery including a positive electrode sheet, the negative electrode sheet in the above aspects of the present invention, a separator and an electrolyte.
  • the negative electrode sheet for lithium ion batteries of the present invention and the lithium ion secondary battery containing the same, the effect of improving the electrochemical performance of the lithium ion battery, especially the capacity, cycle performance and expansion rate, is achieved.
  • Figure 1 is a photograph comparing the dispersion properties in water of a non-carbon-coated silica material according to the present invention (right side) and a carbon-coated silica material (left side) of the prior art;
  • Figure 2 shows a lithium battery containing a prior art carbon-coated silicon oxide material (left) and a lithium battery containing an uncarbon-coated silicon oxide material according to the present invention (right) and different contents of carbon nanoparticles Graph of primary and secondary capacities and primary efficiency of tube lithium batteries.
  • Figure 3 is a diagram showing a lithium battery containing a prior art carbon-coated silicon oxide material (the lowermost polyline SiO Capacity of lithium batteries with silicon materials (the upper three broken lines in the left and right pictures, SiO X -0.1% SWCNT, SiO X -0.05 % SWCNT, SiO and capacity retention graphs.
  • Figure 4 is a diagram showing a lithium battery containing a prior art carbon-coated silicon oxide material (the lowermost polyline SiO Charts of the cycle performance of lithium batteries of silicon materials (the upper three broken lines of the left and right pictures: SiO X -0.1 % SWCNT, SiO
  • the prior art uses a combination of graphite and silicon oxide as the negative active material of a lithium battery, and the silicon oxide used in the prior art is carbon-coated silicon oxide. After silicone oxide is coated with carbon, the first capacity is reduced, the expansion effect of the electrode is increased, and the material cost is increased. Moreover, the uniformity of the carbon coating layer is difficult to control, resulting in increased side reactions with the electrolyte.
  • the present invention provides a negative electrode sheet for lithium batteries, in which the active material silicon oxide is mixed with uncoated silicon oxide and a small amount of carbon nanotubes with good conductivity.
  • the material is used to replace the carbon-coated silicon oxide material to improve the electrochemical performance of the carbon-coated silicon oxide material in the prior art.
  • a negative electrode sheet for a lithium battery includes a current collector and a negative electrode material.
  • the negative electrode material includes graphite, non-carbon-coated silicon oxide SiOx and a negative electrode sheet containing Conductive agent for carbon nanotubes, where 1.6>x>0.
  • the inventor unexpectedly discovered that in the negative electrode material of the lithium battery, the combined use of silicon oxide without carbon coating and carbon nanotubes greatly improves the wettability of the electrolyte to the negative electrode and greatly improves the performance of the lithium battery. The discharge capacity, rate performance and cycle performance are improved, while the battery cost is reduced.
  • the silicon oxide material without carbon coating has a smaller specific surface area and internal crystalline silicon size. Using it as an active material can reduce the expansion of the negative electrode plate and reduce side reactions with the electrolyte.
  • the carbon layer on the surface of carbon-coated silicon oxide is hydrophobic, and the hydrophobicity of uncoated silicon oxide is weaker than that of carbon-coated silicon oxide. Therefore, in Better dispersion in water. Improving the dispersion of negative electrode materials can help improve the electrochemical performance of the battery, the consistency and safety of the battery. In addition, since silicone oxide without carbon coating has better wettability with water, the electrode slurry made from it has better processability and coating uniformity.
  • the silicon oxide without carbon coating according to the present invention does not have problems such as initial capacity decrease, increased expansion of the negative electrode plate, and increased side reactions caused by the carbon coating layer.
  • the discharge capacity, rate performance and cycle performance are also improved compared to the existing carbon-coated silicon oxide materials.
  • silicone oxide is in an amorphous or low crystalline state.
  • the content of SiO2 in the silica is ⁇ 55% by mole, preferably ⁇ 45%.
  • the size of the Si crystals in the silicone oxide is ⁇ 5 nm, preferably ⁇ 1 nm.
  • the XRD of the SiO 2 crystal in the silicon oxide has a half-peak width of ⁇ 1.5° at a 2 ⁇ of 26-27°.
  • the grain size in silicon oxide is too large, it will cause a significant volume effect, which will cause the negative electrode plate to expand in the battery, thereby affecting the electrochemical performance.
  • the content of silicon dioxide is too much, it will reduce the initial capacity, efficiency and rate performance of the battery.
  • the particle size D 50 of the silicon oxide is 1 ⁇ m ⁇ D 50 ⁇ 10 ⁇ m, and when the particle size D 50 of the silicon oxide is 4 ⁇ m ⁇ D 50 ⁇ 10 ⁇ m, the particles have a particle size ⁇ 2 ⁇ m. Accounting for 20%-50%, or when the particle size D 50 of silica is 2 ⁇ m ⁇ D 50 ⁇ 4 ⁇ m, particles with a particle size ⁇ 2 ⁇ m account for 70%-80%.
  • the particle size of silicon oxide within the above range can alleviate the expansion of the negative electrode material during battery charging and improve the cycle life of the battery. If the particle size is too large, it will cause a significant volume effect, exacerbating the expansion of the negative electrode during battery charging. If the particle size is too small, the negative active material particles will not be easily dispersed, which will affect the dispersion performance of the slurry, and It may lead to increased battery side reactions.
  • the specific surface area of silica is 1-5 m 2 /g.
  • the non-carbon-coated silicon oxide material of the present invention has a small specific surface area, and using it as an active material can reduce the expansion of the pole piece and the side reactions with the electrolyte. On the contrary, when the specific surface area of silica is too large, side reactions will increase.
  • the length of the carbon nanotube is 1-30 ⁇ m and the diameter is 1-20 ⁇ m, wherein the aspect ratio of the carbon nanotube is 1:1-10:1, preferably 3:1-10:1 .
  • the carbon nanotubes are single-walled carbon nanotubes.
  • Carbon nanotubes have strong electrical conductivity, which can improve the conductivity of the negative electrode. At the same time, they also have excellent lithium insertion performance in lithium-ion batteries. Therefore, using carbon nanotubes for the negative electrode material of the present invention can improve the electrochemical performance of the battery. At the same time, if the length of the carbon nanotubes is too short, the active materials cannot be well connected and the conductive network cannot be effectively constructed, thereby affecting the electrochemical performance; if the length of the carbon nanotubes is too large and the diameter is too small, agglomeration will occur. Affects its dispersion performance in the negative electrode slurry and the electrochemical performance of the battery.
  • the amount of carbon nanotubes in the negative electrode material is 0.005%-1% by weight, preferably 0.02%-0.2%, based on the total solid weight of the negative electrode material.
  • using a combination of carbon nanotubes and uncoated silicon oxide (a mixture of the two) in amounts within the scope of the present invention can improve the first cycle capacity and cycle 2 capacity of the battery. and efficiency, rate and cycle performance.
  • the graphite in the negative electrode sheet is selected from natural graphite, artificial graphite or a mixture thereof, and the D/G of the graphite is in the range of 0.04-1, preferably 0.3-0.9, and the conductivity of the graphite is in the range of 0.04-1, preferably 0.3-0.9.
  • the body density is 1.6-1.7g/ cm3 , it will be >1s/cm, and when the body density is 2.2.-2.3g/cm3 , it will be >40s/cm.
  • the D/G of graphite refers to the D peak (D-band) and G of the Raman spectrum of graphite.
  • the G peak of the Raman spectrum is a typical Raman peak of bulk crystalline graphite. It is near the wavelength of 1585cm -1 , which is the basic vibration mode of graphite crystal.
  • the negative electrode slurry also contains a binder.
  • the binder includes PVDF, PAA, SBR, CMC binders or any combination of two or more of them. Based on the total content of the negative electrode material The amount of the binder in the negative electrode material is 2% to 4% by weight based on solid weight.
  • the conductive agent also includes conductive carbon black, conductive graphite, vapor-grown carbon fiber, or combinations thereof. Based on the total solid weight of the negative electrode material, the amount of the conductive agent in the negative electrode material is 1 by weight. %-3%.
  • a lithium ion secondary battery including a positive electrode sheet, the negative electrode sheet in the above aspects of the invention, a separator, and an electrolyte.
  • the lithium ion secondary battery of the present invention is prepared by the following steps.
  • Preparation of negative electrode sheet Stir the negative electrode active material, conductive agent, binder and solvent to prepare negative electrode slurry. The negative electrode slurry is then applied to the negative electrode current collector, dried and stamped to form a negative electrode sheet.
  • Battery assembly Stack the prepared negative electrode sheet, separator, lithium sheet, and battery shell in sequence, inject 100ml of electrolyte, seal and assemble into a half-battery.
  • the lithium ion battery used in the examples was prepared by the following steps.
  • the slurry of the negative electrode sheet is composed of active materials, binders, conductive agents, solvents, etc. Based on solid weight, the active material accounts for 95%-97%, the binder 2%-4%, and the conductive agent 1%-3%.
  • the active material consists of 75%-95% graphite and 5%-25% silica oxide of the present invention.
  • Graphite is natural graphite or artificial graphite or a mixture of both.
  • the D/G of graphite used is 0.04-1, preferably 0.3-0.9; the electrical conductivity of graphite satisfies: when the bulk density is 1.6-1.7g/ cm3 , the electrical conductivity is >1s/cm, and the bulk density is 2.2-2.3g/ When cm 3 , the conductivity is >40s/cm.
  • the adhesive is one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), and polyimide (PI) type adhesives, with PAA type adhesive being preferred.
  • the conductive agent is a mixture of conductive carbon black, conductive graphite, vapor-phase grown carbon fiber and carbon nanotubes. Carbon nanotubes account for 0.005%-1% by solid weight, preferably 0.02%-0.2%.
  • the content reaches the state of stretchable film.
  • the negative electrode slurry is coated on the copper foil, dried, and punched.
  • the prepared negative electrode sheet is placed in a vacuum drying oven to dry for 5 hours and then taken out for battery assembly.
  • the electrochemical performance of the fabricated battery was tested by the following method.
  • Capacity test Use a charge and discharge rate of 0.1C and a charge and discharge voltage range of 0V-1.5V to cycle the battery twice to obtain the first capacity and first efficiency and the second cycle capacity and efficiency.
  • Rate test Discharge the fully charged battery at different currents (0.2C, 0.5C, 1C, 2C, 5C), measure the discharge capacity at the corresponding current, and divide the discharge capacity by the first capacity to obtain the corresponding current. Capacity retention rate.
  • Cycle test Charge the battery after the capacity test at a current of 0.1C, and then use a current of 1C to perform a charge and discharge cycle test to test the capacity retention rate of the battery after 100 cycles.
  • Charge and discharge cut-off voltage 0V-1.5V.
  • Negative electrode piece expansion rate test Disassemble the battery after the cycle, take out the negative electrode piece and rinse it with dimethyl carbonate (DMC). After natural drying, use a thickness tester to conduct a thickness test. According to the thickness change before and after the cycle Calculation:
  • Expansion rate (thickness of the negative electrode sheet after 100 cycles - thickness of the negative electrode sheet before cycling)/(thickness of the negative electrode sheet before cycling - thickness of the copper foil).
  • Lithium-ion batteries were prepared using 0.03wt%, 0.05wt% and 0.1wt% single-walled carbon nanotubes respectively by the method described in the preparation examples.
  • a lithium ion battery is prepared by using the method described in the preparation example, using commercially available carbon-coated silicon oxide material instead of the silicon oxide and carbon nanotubes of the present invention.
  • the lithium-ion battery prepared above was subjected to capacity, rate and cycle tests according to the methods described in the test examples.
  • Examples 1-20 are lithium ion batteries prepared using the negative electrode material of the present invention.
  • Comparative Example 1-2 is a lithium-ion battery prepared using the anode material of the present invention that does not contain carbon nanotubes.
  • Comparative Examples 3-4 are lithium ion batteries prepared using commercially available carbon-coated silicon oxide materials.
  • a lithium ion battery was prepared by the method described in the Preparation Example using silicon oxide, graphite and carbon nanotubes having the parameters listed in Tables 1-3 below, and the prepared lithium ion battery was tested according to the method described in the Test Example carry out testing. The test results are shown in Table 4.
  • Graphite conductivity Tested using the PRCD1100 powder conductivity and compaction density tester from Yuaneng Technology. Take about 1g of graphite powder and place it in the equipment mold, apply pressure, and record the changes in conductivity and volume density with pressure.
  • Si grain size obtained by testing and fitting using a D8 XRD instrument from Bruker. Perform XRD scanning on the sample in the range of 2 ⁇ of 10°-80°, and then fit the part of the sample in the range of 2 ⁇ of 25°-32° to obtain the half-peak width of the Si(111) peak, and use the Scherrer formula to calculate Si Grain size.
  • Crystal SiO 2 half-peak width obtained by XRD test fitting. Perform XRD scanning on the sample in the range of 2 ⁇ of 10°-80°, and then fit the part in the range of 2 ⁇ of 26°-27° to obtain the half-peak width of crystal SiO2 .
  • SiO 2 content Use XPS to test, and perform Ar ion etching on the sample. When the etching depth is about 300nm, the silicon peak of XPS is simulated by peak splitting to obtain the content of tetravalent silicon SiO 2 .
  • Silicon oxide particle size tested using the LA-960 laser particle size analyzer from Horiba, and counting the number of particles with a particle size ⁇ 2 ⁇ m based on the number distribution.
  • Specific surface area Use the ASAP2020 specific surface area meter from Micromeritics to test using the N adsorption method.
  • the battery made of the negative electrode material of the present invention has obvious improvements, especially in the second cycle efficiency, 5C discharge rate and cycle retention rate, which is once again proved
  • the combination of uncoated silica and carbon nanotubes of the present invention has improved electrochemical performance.
  • Si grain size O in Table 2 represents the case where crystalline Si does not exist.

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Abstract

本申请提供了一种用于锂电池的负极片及包含其的锂离子二次电池。具体地，本发明提供了一种用于锂电池的负极片，该负极片包括集流体和负极材料，该负极材料包含石墨、未经碳包覆的氧化亚硅SiOx和含有碳纳米管的导电剂，其中1.6>x>0，以及包含该负极片的锂离子二次电池。通过本发明的用于锂电池的负极片及包含其的锂离子二次电池，实现了改善锂离子二次电池的电化学性能的效果。

Description

用于锂电池的负极片及包含其的锂离子二次电池 技术领域
本发明涉及锂离子二次电池领域，具体而言，涉及一种用于锂离子电池的负极片及包含其的锂离子二次电池。
背景技术
近年来，随着电子技术的不断更新，人们对用于支持电子设备的能源供应的电池装置的需求也在不断增加。现如今，需要能够存储更多电量且能够输出高功率的电池。传统铅酸电池以及镍氢电池等已经不能满足新型电子制品的需求。因此，锂电池引起了人们的广泛关注。在对锂电池的开发过程中，已经较为有效地提高了其容量和性能。
为了提高锂离子电池的能量密度，现有技术已经将石墨与氧化亚硅合并使用作为负极活性物质，使用的氧化亚硅为碳包覆的氧化硅。氧化亚硅经碳包覆后，在一定程度上提高了锂离子电池的首次效率及循环性能，但相应降低了电池的首次容量，增加了电池的负极膨胀效应且增加了材料成本，并且氧化亚硅碳包覆层的均匀性难以控制，导致电池负极与电解质的副反应增多。
发明内容
本发明的主要目的在于提供一种用于锂电池的负极片及包含其的锂离子二次电池，以解决使用现有技术的负极片导致锂离子电池的容量、循环性能下降，负极膨胀率较大的问题。
为了实现上述目的，根据本发明的一个方面，本发明提供了一种用于锂电池的负极片，该负极片包括集流体和负极材料，该负极材料包含石墨、未经碳包覆的氧化亚硅SiOx和含有碳纳米管的导电剂，其中1.6＞x＞0。
进一步地，在上述负极片中，氧化亚硅处于非晶态或低结晶态。
进一步地，在上述负极片中，氧化亚硅中的SiO2的含量按摩尔计＜55％(由60％改为＜55％)优选＜45％。
进一步地，在上述负极片中，当氧化亚硅处于低晶态时，氧化亚硅中的Si晶体的尺寸≤5nm，优选≤1nm。
进一步地，在上述负极片中，当氧化亚硅处于低晶态时，氧化亚硅中的SiO2晶体的XRD在2θ为26-27°处的半峰宽＜1.5°。
进一步地，在上述负极片中，氧化亚硅的粒径D50为1μm＜D50＜10μm，并且当氧化亚硅的粒径D50为4μm＜D50＜10μm时，粒径＜2μm的颗粒占20％-50％，或者当氧化亚硅的粒径D50为2μm＜D50＜4μm时，粒径＜2μm的颗粒占70％-80％。
进一步地，在上述负极片中，氧化亚硅的比表面积为1-5m2/g。
进一步地，在上述负极片中，碳纳米管的长度为1-30μm，直径为1-20μm，其中碳纳米管的长径比为1∶1-10∶1，优选3∶1-10∶1。
进一步地，在上述负极片中，基于负极材料的总固体重量，碳纳米管在负极材料中的量为按重量计0.005％-1％，优选0.02％-0.2％。
进一步地，在上述负极片中，负极片中的石墨选自天然石墨、人造石墨或它们的混合物，并且石墨的D/G在0.04-1，优选0.3-0.9的范围内， 石墨的电导率在体密度为1.6-1.7g/cm3时＞1s/cm，在体密度为2.2.-2.3g/cm3时＞40s/cm。
进一步地，在上述负极片中，负极片还包含粘结剂，该粘结剂包括PVDF、PAA、SBR、CMC类粘结剂或它们的组合，基于该负极材料的总固体重量，该粘结剂在负极材料中的量为按重量计2％-4％。
进一步地，在上述负极片中，导电剂还包括导电炭黑、导电石墨、气相生长碳纤维或它们的组合，基于该负极材料的总固体重量，导电剂在负极材料中的量为按重量计1％-3％。
根据本发明的另一方面，提供了一种锂离子二次电池，包括正极片、本发明的上述各个方面中的负极片、隔膜以及电解液。
通过本发明的用于锂离子电池的负极片及包含其的锂离子二次电池，实现了改善锂离子电池的电化学性能，尤其是容量、循环性能和膨胀率的效果。
附图说明
构成本申请的一部分的说明书附图用来提供对本发明的进一步理解，本发明的示意性实施例及其说明用于解释本发明，并不构成对本发明的不当限定。在附图中：
图1是根据本发明的未经碳包覆的氧化亚硅材料(右侧)与现有技术的碳包覆的氧化亚硅材料(左侧)在水中的分散性能对比的照片；
图2是显示含有现有技术的碳包覆的氧化亚硅材料的锂电池(左侧)与根据本发明的含有未经碳包覆的氧化亚硅材料(右侧)以及不同含量的碳纳米管的锂电池的首次和二次容量以及首次效率的图表。
图3是显示含有现有技术的碳包覆的氧化亚硅材料(左图和右图的最下面的折线SiOX/C)的锂电池与根据本发明的含有未经碳包覆的氧化亚硅材料(左图和右图的上面三条折线SiOX-0.1％SWCNT、SiOX-0.05％SWCNT、SiOX-0.03％SWCNT)以及不同含量的碳纳米管的锂电池在不同放电倍率下的容量和容量保持率的图表。
图4是显示含有现有技术的碳包覆的氧化亚硅材料(左图和右图的最下面的折线SiOX/C)的锂电池与根据本发明的含有未经碳包覆的氧化亚硅材料(左图和右图的上面三条折线SiOX-0.1％SWCNT、SiOX-0.05％SWCNT、SiOX-0.03％SWCNT)以及不同含量的碳纳米管的锂电池的循环性能的图表。
具体实施方式
需要说明的是，在不冲突的情况下，本申请中的实施例及实施例中的特征可以相互组合。下面将参考附图并结合实施例来详细说明本发明。
如在背景技术部分中所说明的，现有技术将石墨与氧化亚硅合并使用作为锂电池的负极活性物质，现有技术使用的氧化亚硅为碳包覆的氧化硅。氧化亚硅经碳包覆后降低了首次容量，增加了电极的膨胀效应且增加了材料成本，并且碳包覆层的均匀性难以控制，导致与电解质的副反应增多。
针对上述问题，本发明提供了一种用于锂电池的负极片，其中活性物质氧化亚硅用未经包覆的氧化亚硅搭配少量导电性好的碳纳米管的混合 物来取代碳包覆的氧化亚硅材料，以改善现有技术中碳包覆的氧化亚硅材料的电化学性能。
根据本申请的一个典型的实施方式，提供了一种用于锂电池的负极片，该负极片包括集流体和负极材料，该负极材料包含石墨、未经碳包覆的氧化亚硅SiOx和含有碳纳米管的导电剂，其中1.6＞x＞0。
本发明人出乎意料地发现，在锂电池的负极材料中，未经碳包覆的氧化亚硅与碳纳米管的配合使用，大幅提高了电解液对于负极的浸润性，大大提高了锂电池的放电容量，倍率性能及循环性能，同时降低了电池成本。另外，未经碳包覆的氧化亚硅材料具有较小的比表面积和内部晶体硅尺寸，将其作为活性物质可以降低负极极片的膨胀并减少与电解质的副反应。
例如，如图1中所显示的，分别取3g碳包覆的氧化亚硅材料及未经碳包覆的氧化亚硅材料置于两个不同容器中，然后加入30g水搅拌至粉体分散开。观察粉体在水中的分散状态。在相同的浆料分散条件下，与现有技术的碳包覆的氧化亚硅材料相比，根据本发明的未经碳包覆的氧化亚硅在水中的分散性明显更好，不存在碳包覆的氧化亚硅在水中出现的结块团聚等问题。尽管不希望被理论束缚，但认为碳包覆的氧化亚硅表面的碳层为疏水性的，而未经碳包覆的氧化亚硅的疏水性弱于碳包覆的氧化亚硅，因此在水中分散性更好。改进负极材料的分散性有助于提高电池的电化学性能，电池的一致性及安全性。另外，由于未经碳包覆的氧化亚硅与水的润湿性更好，由其制造的电极浆料具有较好的加工性和涂覆均匀性。
另外，由于不存在碳包覆层，根据本发明的未经碳包覆的氧化亚硅不存在因碳包覆层导致的首次容量下降，负极极片膨胀增加和副反应增加等问题。同时配合具有良好导电性的碳纳米管材料作为导电剂，相对于现有技术的碳包覆的氧化亚硅材料也提高了放电容量，倍率性能及循环性能。
在本申请的一些实施方式中，氧化亚硅处于非晶态或低结晶态。
在本申请的一些实施方式中，氧化亚硅中的SiO2的含量按摩尔计＜55％，优选＜45％。
在优选的实施方式中，当氧化亚硅处于低晶态时，氧化亚硅中的Si晶体的尺寸≤5nm，优选≤1nm。
在优选的实施方式中，当氧化亚硅处于低晶态时，氧化亚硅中的SiO2晶体的XRD在2θ为26-27°处的半峰宽＜1.5°。
发明人发现，氧化亚硅材料中少量硅的存在可以提高电池的初始效率，少量二氧化硅的存在可以降低在电池充电过程中的膨胀，从而提高电池稳定性和电池循环特性。然而，若氧化亚硅中的晶粒尺寸太大，则会导致显著的体积效应，其在电池中会导致负极极片膨胀加剧，进而影响电化学性能。同时，如二氧化硅的含量过多，则会降低电池的首次容量，效率及倍率性能。
在本申请的一些实施方式中，氧化亚硅的粒径D50为1μm＜D50＜10μm，并且当氧化亚硅的粒径D50为4μm＜D50＜10μm时，粒径＜2μm的颗粒占20％-50％，或者当氧化亚硅的粒径D50为2μm＜D50＜4μm时，粒径＜2μm的颗粒占70％-80％。
发明人发现，在上述范围内的氧化亚硅的粒径可以缓解负极材料在电池充电过程中的膨胀，提高电池的循环寿命。如果粒径太大，则会导致显著的体积效应，加剧在电池充电过程中的负极极片膨胀，如果粒径太小，则负极活性材料颗粒不易分散，其会影响浆料的分散性能，并且可能导致电池副反应增多。
在本申请的一些实施方式中，氧化亚硅的比表面积为1-5m2/g。
如上所述，本发明的未经碳包覆的氧化亚硅材料具有较小的比表面积，将其作为活性物质可以降低极片的膨胀以及与电解质的副反应。相反，当氧化亚硅的比表面积过大时，副反应会增多。
在本申请的一些实施方式中，碳纳米管的长度为1-30μm，直径为1-20μm，其中碳纳米管的长径比为1∶1-10∶1，优选3∶1-10∶1。
在优选的实施方式中，碳纳米管为单壁碳纳米管。
碳纳米管具有较强的导电性，其可以提高负极的导电性，同时其在锂离子电池中还具有优异的嵌锂性能。因此将碳纳米管用于本发明的负极材料可以改善电池的电化学性能。同时，若碳纳米管的长度过短，则不能很好地连接活性物质，无法有效地构筑导电网络，进而影响电化学性能；若碳纳米管长度过大且直径过小，则会发生团聚，影响其在负极浆料中的分散性能及电池的电化学性能。
在本申请的一些实施方式中，基于负极材料的总固体重量，碳纳米管在负极材料中的量为按重量计0.005％-1％，优选0.02％-0.2％。
如下文的实施例中详细描述的，使用本发明范围内的量的碳纳米管与未包覆的氧化亚硅的组合(二者的混合物)，可以改善电池的首次容量，第2圈的容量及效率，倍率及循环性能。
在本申请的一些实施方式中，负极片中的石墨选自天然石墨、人造石墨或它们的混合物，并且石墨的D/G在0.04-1，优选0.3-0.9的范围内，石墨的电导率在体密度为1.6-1.7g/cm3时＞1s/cm，在体密度为2.2.-2.3g/cm3时＞40s/cm。其中石墨的D/G是指石墨的拉曼光谱的D峰(D-band)和G 峰(G-band)的峰强度之比，其中石墨的拉曼光谱的D峰为石墨的sp2引起的无序化峰，源自石墨碳晶态边缘的振动，在波长1360-1附近；石墨的拉曼光谱的G峰是体相晶态石墨的典型拉曼峰，在波长1585cm-1附近，其是石墨晶体的基本振动模式。
在本申请的一些实施方式中，负极浆料中还包含粘结剂，该粘结剂包括PVDF、PAA、SBR、CMC类粘结剂或它们二种以上的任意组合，基于该负极材料的总固体重量，该粘结剂在负极材料中的量为按重量计2％-4％。
在本申请的一些实施方式中，导电剂还包括导电炭黑、导电石墨、气相生长碳纤维或它们的组合，基于该负极材料的总固体重量，导电剂在负极材料中的量为按重量计1％-3％。
根据本方面的另一个典型的实施方式，提供了一种锂离子二次电池，包括正极片、本发明的上述各个方面中的负极片、隔膜以及电解液。
在本发明的具体的实施方式中，本发明的锂离子二次电池通过以下步骤制备。
负极片的制备：将负极活性物质、导电剂、粘结剂和溶剂搅拌以制备负极浆料。然后将负极浆料涂布到负极集电体上，干燥并冲压成型以形成负极片。
电解液的配制：将有机溶剂、锂盐和添加剂混合以制备电解液。
电池组装：将制备的负极片，隔膜，锂片，电池壳依次叠放并注入100ml电解液，封口后组装为半电池。
以下结合具体实施例对本发明作进一步详细描述，这些实施例不应理解为用来限制本发明所要求保护的范围。
制备实施例
通过以下步骤制备实施例中使用的锂离子电池。
负极极片的浆料由活性物质、粘结剂、导电剂、溶剂等组成。以固体重量计，活性物质占比95％-97％，粘结剂2％-4％，导电剂1％-3％。活性物质由75％-95％的石墨与5％-25％的本发明的氧化亚硅。石墨为天然石墨或人造石墨或两者的混合物。采用的石墨的D/G为0.04-1，优选0.3-0.9；石墨的电导率满足：在体密度为1.6-1.7g/cm3时电导率＞1s/cm，体密度为2.2-2.3g/cm3时电导率＞40s/cm。粘结剂为丁苯橡胶(SBR)，聚丙烯酸(PAA)，聚酰亚胺(PI)型粘结剂中的一种或多种，优选PAA型粘结剂。导电剂为导电炭黑，导电石墨，气相生长碳纤维与碳纳米管的混合物。碳纳米管以固体重量计占比0.005％-1％，优选0.02％-0.2％。
具体地，将12.8wt％的氧化亚硅与82.2wt％的石墨进行预混，至混合均匀，然后加入所需粘结剂总量50wt％的粘结剂，搅拌混合均匀，再加入1.2wt％的导电炭黑搅拌至混合均匀，然后加入剩余质量的50wt％的粘结剂，搅拌混合，加入碳纳米管(碳纳米管的量如以下具体实施例所描述)搅拌混合，最后加入水调节固含量至可拉膜状态。将负极浆料涂敷在铜箔上，烘干、冲切，将制成的负极片放置在真空干燥箱中干燥5h后取出用于组装电池。
测试实施例
通过以下方法测试制成的电池的电化学性能。
容量测试：使用0.1C的充放电倍率，0V-1.5V的充放电电压范围，对电池循环2次获取首次容量及首次效率和第2圈的容量及效率。
倍率测试：将充满电的电池在不同的电流(0.2C、0.5C、1C、2C、5C)下进行放电，测量相应的电流下的放电容量，并用放电容量除以首次容量得到相应的电流下容量保持率。
循环测试：将容量测试结束后的电池在0.1C电流下充电，然后使用1C电流进行充放电循环测试，测试100周循环后电池的容量保持率。充放电截止电压：0V-1.5V。
负极极片膨胀率测试：将循环结束后的电池进行拆解，取出负极极片并用碳酸二甲酯(DMC)冲洗干净，自然晾干后采用厚度测试仪进行厚度测试，根据循环前后的厚度变化进行计算：
膨胀率＝(100周循环后的负极极片厚度-循环前负极极片厚度)/(循环前负极极片厚度-铜箔厚度)。
本发明负极材料与现有技术的比较
通过制备实施例中描述的方法，分别使用0.03wt％、0.05wt％和0.1wt％的单壁碳纳米管制备锂离子电池。另一方面，通过制备实施例中描述的方法，使用市售的碳包覆的氧化亚硅材料代替本发明的氧化亚硅与碳纳米管制备锂离子电池。对以上制备的锂离子电池根据测试实施例描述的方法进行容量，倍率及循环测试。
以上测试的结果在图2-4中示出。由图2-4可以看出，与市售的碳包覆的氧化亚硅材料相比，使用本发明的未包覆的氧化亚硅与单壁碳纳米管的组合在首次容量，第2圈的容量及效率，倍率及循环性能方面具有明显优势。该结果证明了与碳包覆的氧化亚硅材料相比，本发明的未包覆的氧化亚硅与碳纳米管的组合在电化学性能方面获得了改善。
氧化亚硅、石墨和碳纳米管参数的影响
通过以下实施例说明氧化亚硅、石墨和碳纳米管的各种参数对电池性能的影响。其中实施例1-20是使用本发明的负极材料制备的锂离子电池。 对比例1-2是使用不含碳纳米管的本发明的负极材料制备的锂离子电池。对比例3-4是使用市售的碳包覆的氧化亚硅材料制备的锂离子电池。通过制备实施例中描述的方法，使用具有下表1-3中列出的参数的氧化亚硅、石墨和碳纳米管制备锂离子电池，并对制备的锂离子电池根据测试实施例描述的方法进行测试。测试结果如表4所示。
其中表1-4中显示的各项参数的测试方法如下：
石墨的D/G：采用来自Renishaw的inViaQontor拉曼光谱仪进行测试，测试范围为50-3000cm-1。
石墨电导率：采用来自元能科技的PRCD1100型粉体电导率及压实密度测试仪进行测试。取1g左右的石墨粉体置于设备模具中，施加压力，记录电导率及体密度随压力的变化。
Si晶粒尺寸：采用来自Bruker的D8型XRD仪器测试拟合得出。对样品在2θ为10°-80°范围内进行XRD扫描，然后对2θ为25°-32°范围内的部分进行拟合得到Si(111)峰的半峰宽，使用谢乐公式计算得到Si晶粒尺寸。
晶体SiO2半峰宽：采用XRD测试拟合得出。对样品在2θ为10°-80°范围内进行XRD扫描，然后对2θ为26°-27°范围内的部分进行拟合得到晶体SiO2的半峰宽。
SiO2含量：采用XPS进行测试，对样品进行Ar离子刻蚀，刻蚀深度为300nm左右时对XPS的硅峰进行分峰模拟得出四价硅SiO2的含量。
氧化亚硅粒径：采用来自Horiba的LA-960型激光粒度仪进行测试，以数量分布为基准统计粒径＜2μm颗粒数量。
比表面积：使用来自Micromeritics的ASAP2020型比表面积仪，采用N2吸附法进行测试。
表1：各实施例中使用的负极材料中石墨的参数
表2：各实施例中使用的负极材料中氧化亚硅的参数

表3：各实施例中使用的负极材料中碳纳米管的参数

表4：各实施例1-20和对比例1-4的锂离子电池的性能

由表4可以看出，首先，与对比例1-4相比，由本发明的负极材料制成的电池特别是在第2圈效率、5C放电倍率和循环保持率方面有明显的改进，再次证明与碳包覆的氧化亚硅材料相比，本发明的未包覆的氧化亚硅与碳纳米管的组合在电化学性能方面获得了改善。
关于石墨的参数对电池性能的影响，由实施例13至15可以看出，当石墨具有本发明范围内的D/G和电导率时，在第2圈效率、5C放电倍率、循环保持率和负极极片膨胀率方面有较好的性能。
关于SiO2含量对电池性能的影响，通过实施例3与实施例8和对比例4和5的比较可以看出，当SiO2含量高于本发明的范围时，除负极极片膨胀率外，电池的其他各项性能均有劣化。
关于Si晶粒尺寸对电池性能的影响，通过实施例6和10与实施例1、2、12和对比例3和6的比较可以看出，当Si晶粒尺寸高于本发明的范围时，电池的各项性能均有劣化，特别是负极极片膨胀率有明显劣化。应注意，在表2中Si晶粒尺寸为O代表不存在晶体Si的情况。
关于晶体SiO2在26-27°处的半峰宽对电池性能的影响，通过实施例3、4和5以及实施例9和10之间的比较可以看出，较低的半峰宽导致电池的首次和第2圈容量及5C放电倍率方面的改善。应注意，在表2中半峰宽为O代表不存在晶体SiO2的情况。
关于氧化亚硅粒径对电池性能的影响，通过实施例3和7之间的比较可以看出，本发明范围内的粒径＜2μm的颗粒比例导致5C放电倍率、循环保持率和膨胀率方面的明显改善。通过实施例9、10和11之间的比较 可以看出，本发明范围内的粒径＜2μm的颗粒比例导致首次和第2圈容量及5C放电倍率方面的改善。
关于比表面积对电池性能的影响，通过本发明实施例和对比例3之间的比较可以看出，高于本发明范围内的氧化亚硅比表面积导致电极膨胀率的劣化。
关于碳纳米管的参数对电池性能的影响，由实施例16至20可以看出，当碳纳米管的含量低于或高于本发明的范围时，电池的首次容量、第2圈容量、第2圈效率和5C放电倍率显著劣化。当碳纳米管的尺寸和长径比超出本发明的范围时，电池的各项性能，尤其是5C放电倍率和膨胀率劣化。
总之，通过使用根据本发明的未包覆的氧化亚硅与碳纳米管的组合作为负极材料，与根据现有技术的碳包覆的氧化亚硅材料相比，获得了电池的电化学性能的改善。
以上所描述的仅为本发明的优选实施例，并不用于限制本发明，对于本领域的技术人员来说，本发明可以有各种更改和变化。凡在本发明的精神和原则之内，所作的任何修改、等同替换、改进等，均应包含在本发明的保护范围之内。

Claims (13)

  1. 一种用于锂电池的负极片，其特征在于，所述负极片包括集流体和负极材料，所述负极材料包含石墨、未经碳包覆的氧化亚硅SiOx和含有碳纳米管的导电剂，其中1.6>x>0。
  2. 根据权利要求1所述的负极片，其特征在于，所述氧化亚硅处于非晶态或低结晶态。
  3. 根据权利要求1所述的负极片，其特征在于，所述氧化亚硅中的SiO2的含量按摩尔计<55％，优选<45％。
  4. 根据权利要求2所述的负极片，其特征在于，当所述氧化亚硅处于低晶态时，所述氧化亚硅中的Si晶体的尺寸≤5nm，优选≤1nm。
  5. 根据权利要求2或3所述的负极片，其特征在于，当所述氧化亚硅处于低晶态时，所述氧化亚硅中的SiO2晶体的XRD在2θ为26-27°处的半峰宽<1.5°。
  6. 根据权利要求1-4中任一项所述的负极片，其特征在于，所述氧化亚硅的粒径D50为1μm<D50<10μm，并且当所述氧化亚硅的粒径D50为4μm<D50<10μm时，粒径<2μm的颗粒占20％-50％，或者当所述氧化亚硅的粒径D50为2μm<D50<4μm时，粒径<2μm的颗粒占70％-80％。
  7. 根据权利要求1-4中任一项所述的负极片，其特征在于，所述氧化亚硅的比表面积为1-5m2/g。
  8. 根据权利要求1-4中任一项所述的负极片，其特征在于，所述碳纳米管的长度为1-30μm，直径为1-20μm，其中所述碳纳米管的长径比为1:1-10:1，优选3:1-10:1。
  9. 根据权利要求1-4中任一项所述的负极片，其特征在于，基于所述负极材料的总固体重量，所述碳纳米管在所述负极材料中的量为按重量计0.005％-1％，优选0.02％-0.2％。
  10. 根据权利要求1-4中任一项所述的负极片，其特征在于，所述负极片中的所述石墨选自天然石墨、人造石墨或它们的混合物，并且所述石墨的拉曼光谱的D峰与G峰的峰强度之比D/G在0.04-1，优选0.3-0.9的范围内，所述石墨的电导率在体密度为1.6-1.7g/cm3时>1s/cm，在体密度为2.2.-2.3g/cm3时>40s/cm。
  11. 根据权利要求1-4中任一项所述的负极片，其特征在于，所述负极片还包含粘结剂，所述粘结剂包括PVDF、PAA、SBR、CMC类粘结剂或它们两种以上的任意组合，基于所述负极材料的总固体重量，所述粘结剂在所述负极材料中的量为按重量计2％-4％。
  12. 根据权利要求1-4中任一项所述的负极片，其特征在于，所述导电剂还包括导电炭黑、导电石墨、气相生长碳纤维或它们两种以上的任意组合，基于所述负极材料的总固体重量，所述导电剂在所述负极材料中的量为按重量计1％-3％。
  13. 一种锂离子二次电池，包括正极片、负极片、隔膜以及电解液，其特征在于，所述负极片为权利要求1-12中任一项所述的负极片。
PCT/CN2023/078541 2022-05-06 2023-02-27 用于锂电池的负极片及包含其的锂离子二次电池 Ceased WO2023213122A1 (zh)

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