WO2021185014A1 - 负极活性材料及使用其的电化学装置和电子装置 - Google Patents

负极活性材料及使用其的电化学装置和电子装置 Download PDF

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WO2021185014A1
WO2021185014A1 PCT/CN2021/076186 CN2021076186W WO2021185014A1 WO 2021185014 A1 WO2021185014 A1 WO 2021185014A1 CN 2021076186 W CN2021076186 W CN 2021076186W WO 2021185014 A1 WO2021185014 A1 WO 2021185014A1
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active material
negative electrode
electrode active
bet
negative
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PCT/CN2021/076186
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English (en)
French (fr)
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冯鹏洋
蔡余新
董佳丽
谢远森
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宁德新能源科技有限公司
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Priority to JP2022552970A priority Critical patent/JP2023516413A/ja
Priority to EP21770876.7A priority patent/EP3968415A4/en
Priority to KR1020227035947A priority patent/KR20220147692A/ko
Publication of WO2021185014A1 publication Critical patent/WO2021185014A1/zh
Priority to US17/708,288 priority patent/US20220223865A1/en

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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M4/36Selection of substances as active materials, active masses, active liquids
    • H01M4/58Selection 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
    • H01M4/583Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M4/36Selection of substances as active materials, active masses, active liquids
    • H01M4/58Selection 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
    • H01M4/583Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01BNON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00Carbon; Compounds thereof
    • C01B32/20Graphite
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01BNON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00Carbon; Compounds thereof
    • C01B32/20Graphite
    • C01B32/205Preparation
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M4/13Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01PINDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00Crystal-structural characteristics
    • C01P2002/70Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01PINDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00Particle morphology
    • C01P2004/60Particles characterised by their size
    • C01P2004/61Micrometer sized, i.e. from 1-100 micrometer
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01PINDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00Physical properties of inorganic compounds
    • C01P2006/12Surface area
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00Secondary cells; Manufacture thereof
    • H01M10/05Accumulators with non-aqueous electrolyte
    • H01M10/052Li-accumulators
    • H01M10/0525Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M2004/021Physical characteristics, e.g. porosity, surface area
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M2004/026Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027Negative electrodes
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10Energy storage using batteries

Definitions

  • This application relates to the field of energy storage, in particular to a negative electrode active material and an electrochemical device and an electronic device using the same.
  • Electrochemical devices for example, lithium-ion batteries
  • Small-sized lithium-ion batteries are generally used as power sources for driving portable electronic communication devices (for example, camcorders, mobile phones, or notebook computers, etc.), especially high-performance portable devices.
  • portable electronic communication devices for example, camcorders, mobile phones, or notebook computers, etc.
  • medium-sized and large-sized lithium batteries with high output characteristics have been developed for use in electric vehicles (EV) and large-scale energy storage systems (ESS).
  • EV electric vehicles
  • ESS large-scale energy storage systems
  • the present application attempts to solve at least one problem existing in related fields at least to some extent by providing a negative electrode active material, an electrochemical device and an electronic device using the same.
  • the present application provides a negative active material, wherein the negative active material has a median particle diameter D 1 v50, and the negative active material has a median particle diameter D 2 v50 under a pressure of 1 t, And D 2 v50/D 1 v50 is not less than 0.8. In some embodiments, the D 2 v50/D 1 v50 of the negative active material is not less than 0.9. In some embodiments, the D 2 v50/D 1 v50 of the negative active material is 0.8, 0.85, 0.9, 0.95, or 1.0.
  • the negative active material has a specific surface area BET 1 , and the BET 1 is 0.6 m 2 /g to 2.0 m 2 /g, and the negative active material has a specific surface area BET 2 under a pressure of 1 t, And (BET 2 -BET 1 )/BET 1 ⁇ 1.
  • the BET 1 is 0.7 m 2 /g to 1.8 m 2 /g.
  • the BET 1 is 0.8 m 2 /g to 1.6 m 2 /g.
  • the BET 1 is 0.6m 2 / g, 0.7m 2 / g, 0.8m 2 / g, 0.9m 2 / g, 1.0m 2 / g, 1.1m 2 / g, 1.2m 2 /g,1.3m 2 /g,1.4m 2 /g,1.5m 2 /g,1.6m 2 /g,1.7 m 2 /g,1.8m 2 /g,1.9m 2 / g or 2.0m 2 / g .
  • the negative active material includes graphite particles, and the graphite particles satisfy at least one of the conditions (a) to (c):
  • D 1 v50 is 10 ⁇ m to 25 ⁇ m
  • the grain size La of the graphite particles in the horizontal direction is 160 nm to 165 nm
  • the grain size Lc of the graphite particles in the vertical direction is 30 nm to 32 nm.
  • the D 1 v50 of the graphite particles is 15 ⁇ m to 20 ⁇ m. In some embodiments, the D 1 v50 of the graphite particles is 10 ⁇ m, 12 ⁇ m, 15 ⁇ m, 18 ⁇ m, 20 ⁇ m, 22 ⁇ m, or 25 ⁇ m.
  • D 1 v90/D 1 v10 of the graphite particles is less than 3.0. In some embodiments, D 1 v90/D 1 v10 of the graphite particles is less than 2.5. In some embodiments, D 1 v90/D 1 v10 of the graphite particles is less than 2.0.
  • the grain size La of the graphite particles in the horizontal direction is 160 nm, 161 nm, 162 nm, 163 nm, 164 nm, or 165 nm
  • the grain size Lc of the graphite particles in the vertical direction is 30nm, 31nm or 32nm.
  • the present application provides an electrochemical device comprising a negative electrode including a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer including the negative electrode active material according to the present application .
  • the anode active material layer satisfies at least one of conditions (d) to (f):
  • the anode active material layer contains carbon element and oxygen element, and the ratio of the content of the carbon element to the content of the oxygen element is 2:3 to 990:1;
  • the porosity of the anode active material layer is 20% to 30%.
  • the ratio of the content of the carbon element to the content of the oxygen element is 1:1 to 800:1. In some embodiments, the ratio of the content of the carbon element to the content of the oxygen element is 5:1 to 500:1. In some embodiments, the ratio of the content of the carbon element to the content of the oxygen element is 10:1 to 300:1. In some embodiments, the ratio of the content of the carbon element to the content of the oxygen element is 50:1 to 100:1. In some embodiments, the ratio of the content of the carbon element to the content of the oxygen element is 2:3, 1:1, 5:1, 10:1, 20:1, 50:1, 100:1, 200:1, 300:1, 400:1, 500:1, 600:1, 700:1, 800:1, 900:1 or 990:1.
  • the C004/C110 of the negative active material layer is 6.0 to 10.0. In some embodiments, the C004/C110 of the negative active material layer is 7.0 to 8.0.
  • the porosity of the negative active material layer is 20% to 25%. In some embodiments, the porosity of the negative active material layer is 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, or 30%.
  • the electrochemical device is in a fully discharged state, and the peak area C004' of the (004) plane and the peak area C110 of the (110) plane of the negative electrode active material are determined by X-ray diffraction pattern measurement.
  • the ratio of'C004'/C110' is 6.8 to 17.2.
  • the C004'/C110' of the negative active material is 7.0 to 16.6.
  • the C004'/C110' of the negative active material is 10.0 to 16.0.
  • the C004'/C110' of the negative active material is 11.0 to 15.5.
  • the negative electrode active material when the electrochemical device is fully discharged, has a median particle diameter D a v50, and the negative electrode active material has a median particle diameter D b v50 under a pressure of 1 t, And D b v50/D a v50 is not less than 0.9.
  • the D b v50/D a v50 of the negative active material is not less than 0.91.
  • the D b v50/D a v50 of the negative active material is 0.92, 0.95, 0.98, or 1.0.
  • the median diameter D a v50 of the negative electrode active material is 8 ⁇ m to 20 ⁇ m. In some embodiments, the D a v50 of the negative active material is 10 ⁇ m to 15 ⁇ m. In some embodiments, the D a v50 of the negative active material is 8 ⁇ m, 10 ⁇ m, 12 ⁇ m, 15 ⁇ m, 18 ⁇ m, or 20 ⁇ m.
  • the negative electrode active material in the fully discharged state of the electrochemical device, has a specific surface area BET a , the negative electrode active material has a specific surface area BET b under a pressure of 1 t, and (BET b -BET a )/BET a ⁇ 0.6.
  • the present application provides an electronic device, which includes the electrochemical device according to the present application.
  • Fig. 1 shows the expansion percentage of the lithium ion battery according to Example 22 and Comparative Example 1 of the present application at 45° C. with the number of cycles.
  • a list of items connected by the term "at least one of” can mean any combination of the listed items. 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 element or multiple elements.
  • Project B can contain a single element or multiple elements.
  • Project C can contain a single element or multiple elements.
  • Dv50 refers to the particle size of the negative electrode active material that reaches 50% of the cumulative volume from the small particle size side in the volume-based particle size distribution, that is, the volume of the negative electrode active material smaller than this particle size accounts for the negative electrode 50% of the total volume of active material.
  • Dv10 refers to the particle size of the negative electrode active material that reaches 10% of the cumulative volume from the small particle size side in the volume-based particle size distribution, that is, the volume of the negative electrode active material smaller than this particle size accounts for the negative electrode 10% of the total volume of active material.
  • Dv90 refers to the particle size of the negative electrode active material that reaches 90% of the cumulative volume from the small particle size side in the volume-based particle size distribution, that is, the volume of the negative electrode active material smaller than this particle size accounts for 90% of the total volume of the negative active material.
  • the Dv50, Dv10, and Dv90 of the negative electrode active material can be measured by a method known in the art, for example, by a laser particle size analyzer (for example, a Malvern particle size tester).
  • a laser particle size analyzer for example, a Malvern particle size tester.
  • full discharge state refers to the constant current of the electrochemical device at a discharge current of 1C (that is, the current value at which the theoretical capacity is completely discharged within 1 hour) in an environment of 25°C Discharge to the state where the voltage is 3.0V.
  • the electrochemical device of the present application is in a 50% state of charge (SOC).
  • an electrochemical device a lithium ion battery is taken as an example below
  • the intercalation of lithium ions will cause the electrochemical device to expand, which is particularly serious at high temperatures.
  • Increasing the degree of recombination of negative electrode active materials is one of the means to improve the cycle performance of lithium ion batteries.
  • the primary particles of the negative electrode active material can be compounded to form secondary particles by using a high-viscosity binder or increasing the amount of the binder. The application achieves the balance between the high capacity of the lithium ion battery and the thickness expansion during cycling by improving the strength of the secondary particles.
  • the present application provides a negative active material, wherein the negative active material has a median particle diameter D 1 v50, the negative active material has a median particle diameter D 2 v50 under a pressure of 1 t, and D 2 v50/D 1 v50 is not less than 0.8.
  • the D 2 v50/D 1 v50 of the negative active material is not less than 0.9.
  • the D 2 v50/D 1 v50 of the negative active material is 0.8, 0.85, 0.9, 0.95, or 1.0.
  • the D 2 v50/D 1 v50 of the negative active material can reflect the change rate of the particle size of the negative active material after being compressed.
  • the ratio of the broken particles to the total negative electrode active material particles (ie, the particle crushing rate ) Is lower, the strength of the negative electrode active material is higher, so that the cross-section of the negative electrode active material that is not coated with the binder is reduced by pressure, which can reduce the formation of solid electrolyte interface (SEI) film, which helps to improve lithium
  • SEI solid electrolyte interface
  • the D 2 v50/D 1 v50 of the negative active material is within the above range, the negative active material has high strength, which helps to achieve a balance between high gram capacity and low cycle thickness expansion rate of the lithium ion battery.
  • the negative electrode active material of the present application can be obtained by the following method: adding a high-viscosity additive to the primary particles of the negative electrode active material to obtain a mixture, and sintering the mixture to obtain secondary particles of the negative electrode active material, wherein the high-viscosity additive includes oil At least one of high-temperature asphalt, coal-based high-temperature asphalt, or resin polymer material, based on the total weight of the negative active material, the content of the high-viscosity additive is not more than 30 wt%.
  • the median particle diameter D 1 v50 of the negative active material is 10 ⁇ m to 25 ⁇ m. In some embodiments, the D 1 v50 of the negative active material is 15 ⁇ m to 20 ⁇ m. In some embodiments, the D 1 v50 of the negative active material is 10 ⁇ m, 12 ⁇ m, 15 ⁇ m, 18 ⁇ m, 20 ⁇ m, 22 ⁇ m, or 25 ⁇ m.
  • the median particle diameter D 2 v50 of the negative electrode active material under a pressure of 1 t is 8 ⁇ m to 20 ⁇ m. In some embodiments, the D 2 v50 of the negative active material is 10 ⁇ m to 15 ⁇ m. In some embodiments, the D 2 v50 of the negative active material is 8 ⁇ m, 10 ⁇ m, 12 ⁇ m, 15 ⁇ m, 18 ⁇ m, or 20 ⁇ m.
  • D 1 v90 and D 1 v10 of the negative active material satisfy D 1 v90/D 1 v10 less than 3.5. In some embodiments, the D 1 v90/D 1 v10 of the negative active material is less than 3.0. In some embodiments, the D 1 v90/D 1 v10 of the negative active material is less than 2.5. In some embodiments, the D 1 v90/D 1 v10 of the negative active material is less than 2.0.
  • the negative active material includes crystal grains, and by X-ray diffraction, the crystal grain size La of the crystal grains along the horizontal direction is 160 nm to 165 nm, and the crystal grain size of the crystal grains along the vertical direction is from 160 nm to 165 nm. Lc is 30nm to 32nm.
  • the negative active material includes crystal grains. By X-ray diffraction, the crystal grains have a crystal grain size La along a horizontal direction of 161 nm to 164 nm, and the crystal grains have a crystal grain size Lc along a vertical direction. From 30.5nm to 31.5nm.
  • the grain size La of the graphite particles in the horizontal direction is 160 nm, 161 nm, 162 nm, 163 nm, 164 nm, or 165 nm
  • the grain size Lc of the graphite particles in the vertical direction is 30nm, 31nm or 32nm.
  • the negative active material includes graphite particles having the same D 1 v50, D 2 v50, D 1 v90, and D 1 v10 as the negative active material.
  • the negative active material is graphite particles.
  • the negative active material has a specific surface area BET 1 , and the BET 1 is 0.6 m 2 /g to 2.0 m 2 /g, and the negative active material has a specific surface area BET 2 under a pressure of 1 t, And (BET 2 -BET 1 )/BET 1 ⁇ 1.
  • the negative electrode active material satisfies (BET 2 -BET 1 )/BET 1 ⁇ 1, the growth rate of the specific surface area of the negative electrode active material after pressure is not more than 100% compared with the negative electrode active material without pressure.
  • SEI solid electrolyte interface
  • the BET 1 is 0.7 m 2 /g to 1.8 m 2 /g. In some embodiments, the BET 1 is 0.8 m 2 /g to 1.6 m 2 /g. In some embodiments, the BET 1 is 0.6m 2 / g, 0.7m 2 / g, 0.8m 2 / g, 0.9m 2 / g, 1.0m 2 / g, 1.1m 2 / g, 1.2m 2 /g,1.3m 2 /g,1.4m 2 /g,1.5m 2 /g,1.6m 2 /g,1.7m 2 /g,1.8m 2 /g,1.9m 2 / g or 2.0m 2 / g .
  • the specific surface area BET 2 of the negative active material under a pressure of 1 t is 1.2 m 2 /g to 4.0 m 2 /g.
  • the BET 2 of the negative active material is 1.5 m 2 /g to 3.0 m 2 /g.
  • the parameters of the negative electrode active material under 1t pressure can be obtained by referring to the steps in the National Standard of the People's Republic of China GB/T24533-2009.
  • the specific surface area of the negative electrode active material can be obtained by the following method:
  • a specific surface area analyzer such as Tristar II 3020M
  • the present application also provides an electrochemical device, which includes a negative electrode including a negative electrode current collector and a negative electrode active material layer.
  • the anode active material layer includes the anode active material according to the present application.
  • the anode active material layer includes carbon element and oxygen element, and the ratio of the content of the carbon element to the content of the oxygen element is 2:3 to 990:1. In some embodiments, the ratio of the content of the carbon element to the content of the oxygen element is 1:1 to 800:1. In some embodiments, the ratio of the content of the carbon element to the content of the oxygen element is 5:1 to 500:1. In some embodiments, the ratio of the content of the carbon element to the content of the oxygen element is 10:1 to 300:1. In some embodiments, the ratio of the content of the carbon element to the content of the oxygen element is 50:1 to 100:1.
  • the ratio of the content of the carbon element to the content of the oxygen element is 2:3, 1:1, 5:1, 10:1, 20:1, 50:1, 100:1, 200:1, 300:1, 400:1, 500:1, 600:1, 700:1, 800:1, 900:1 or 990:1.
  • the ratio of the content of the carbon element in the negative active material layer to the content of the oxygen element is within the above range, the particle size and the graphitization degree of the negative active material particles are within a suitable range, which helps to improve the lithium ion battery The capacity and cyclic thickness expansion rate.
  • the ratio of the peak area C004 of the (004) plane and the peak area C110 of the (110) plane of the negative electrode active material layer measured by X-ray diffraction pattern C004/C110 is 5.7 to 11.2.
  • the C004/C110 value of the negative electrode active material layer measured by X-ray diffraction pattern can reflect the anisotropy of the negative electrode active material particles. The smaller the C004/C110 value, the smaller the anisotropy, which helps to improve the cyclic thickness expansion rate of lithium-ion batteries.
  • the C004/C110 of the negative active material layer is 6.0 to 10.0.
  • the C004/C110 of the negative active material layer is 7.0 to 8.0.
  • the porosity of the negative active material layer is 20% to 30%. In some embodiments, the porosity of the negative active material layer is 20% to 25%. In some embodiments, the porosity of the negative active material layer is 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, or 30%.
  • the electrochemical device is in a fully discharged state, and the peak area C004' of the (004) plane and the peak area C110 of the (110) plane of the negative electrode active material are determined by X-ray diffraction pattern measurement.
  • the ratio of'C004'/C110' is 6.8 to 17.2.
  • the C004'/C110' of the negative active material is 7.0 to 16.5.
  • the C004'/C110' of the negative active material is 10.0 to 15.0.
  • the C004'/C110' of the negative active material is 12.0 to 14.0.
  • the negative electrode active material when the electrochemical device is fully discharged, has a median particle diameter D a v50, and the negative electrode active material has a median particle diameter D b v50 under a pressure of 1 t, And D b v50/D a v50 is not less than 0.9.
  • the D b v50/D a v50 of the negative electrode active material can reflect the degree of particle crushing of the negative electrode active material in the electrochemical device in a fully discharged state after being compressed.
  • the D b v50/D a v50 of the negative electrode active material is 0.92, 0.95, 0.98, or 1.0.
  • the median diameter D a v50 of the negative electrode active material is 8 ⁇ m to 20 ⁇ m. In some embodiments, the D a v50 of the negative active material is 10 ⁇ m to 15 ⁇ m. In some embodiments, the D a v50 of the negative active material is 8 ⁇ m, 10 ⁇ m, 12 ⁇ m, 15 ⁇ m, 18 ⁇ m, or 20 ⁇ m.
  • the negative electrode active material when the electrochemical device is fully discharged, has a median particle diameter D b v50 of 7.2 ⁇ m to 18 ⁇ m under a pressure of 1 t.
  • the D b v50 of the negative active material is 8 ⁇ m to 15 ⁇ m.
  • the D b v50 of the negative active material is 7.2 ⁇ m, 8 ⁇ m, 10 ⁇ m, 12 ⁇ m, 15 ⁇ m, or 18 ⁇ m.
  • the negative electrode active material in the fully discharged state of the electrochemical device, has a specific surface area BET a , the negative electrode active material has a specific surface area BET b under a pressure of 1 t, and (BET b -BET a )/BET a ⁇ 0.6.
  • the negative electrode active material satisfies (BET b -BET a )/BET a ⁇ 0.6
  • the growth rate of the specific surface area of the negative electrode active material after pressure is less than 60% compared with the negative electrode active material without pressure.
  • the specific surface area of the negative electrode active material in the electrochemical device in the fully discharged state conforms to the above relationship, it can reflect that the strength of the negative electrode active material is higher.
  • the specific surface area BET a of the negative electrode active material is 0.6 m 2 /g to 2.0 m 2 /g. In some embodiments, the BET a of the negative active material is 0.8 m 2 /g to 1.5 m 2 /g. In some embodiments, the BET a of the negative active material is 1.0 m 2 /g to 1.2 m 2 /g.
  • the anode active material for the BET a 0.6m 2 /g,0.7m 2 /g,0.8m 2 /g,0.9m 2 /g,1.0m 2 /g,1.1m 2 / g , 1.2m 2 /g,1.3m 2 /g,1.4m 2 /g,1.5m 2 /g,1.6m 2 /g,1.7m 2 /g,1.8m 2 /g,1.9m 2 / g or 2.0 m 2 /g.
  • the specific surface area BET b of the negative electrode active material under a pressure of 1 t is 0.96 m 2 /g to 3.2 m 2 /g.
  • the BET 2 of the negative active material is 1.0 m 2 /g to 3.0 m 2 /g.
  • the BET 2 of the negative active material is 1.5 m 2 /g to 2.0 m 2 /g.
  • the negative electrode active material BET 2 is 0.96m 2 /g,1.0m 2 /g,1.2m 2 /g,1.5m 2 /g,1.8m 2 /g,2.0m 2 / g , 2.2m 2 /g,2.5m 2 /g,2.8m 2 /g,3.0m 2 / g or 3.2m 2 / g.
  • the negative current collector used in the present application may be selected from copper foil, nickel foil, stainless steel foil, titanium foil, foamed nickel, foamed copper, polymer substrates coated with conductive metals, and combinations thereof .
  • the negative electrode further includes a conductive layer.
  • the conductive material of the conductive layer may include any conductive material as long as it does not cause a chemical change.
  • conductive materials include carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanotubes, graphene, etc.), metal-based materials (e.g., metal Powder, metal fibers, etc., such as copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof.
  • the negative electrode further includes a binder, and the binder is selected from at least one of the following: polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, and diacetyl cellulose , Polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, poly Propylene, styrene butadiene rubber, acrylic (ester) styrene butadiene rubber, epoxy resin or nylon, etc.
  • the binder is selected from at least one of the following: polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, and diacetyl cellulose , Polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone
  • the negative electrode can be manufactured by any method known in the prior art.
  • the negative electrode can be made into a slurry by adding a binder and a solvent to the negative active material, and adding thickeners, conductive materials, fillers, etc. as needed, and coating the slurry on the current collector. It is formed by pressing after drying.
  • the negative electrode active material layer may be formed using methods such as an evaporation method, a sputtering method, and a plating method.
  • the positive electrode includes a positive electrode current collector and a positive electrode active material provided on the positive electrode current collector.
  • the specific types of positive electrode active materials are not subject to specific restrictions, and can be selected according to requirements.
  • the positive active material includes a compound that reversibly intercalates and deintercalates lithium ions.
  • the positive active material may include a composite oxide containing lithium and at least one element selected from cobalt, manganese, and nickel.
  • the positive electrode active material is selected from lithium cobalt oxide (LiCoO 2 ), lithium nickel manganese cobalt ternary material, lithium manganate (LiMn 2 O 4 ), lithium nickel manganese oxide (LiNi 0.5 Mn 1.5 O 4 ) , One or more of lithium iron phosphate (LiFePO 4 ).
  • the positive electrode active material layer may have a coating on the surface, or may be mixed with another compound having a coating.
  • the coating may include oxides of coating elements, hydroxides of coating elements, oxyhydroxides of coating elements, oxycarbonates of coating elements, and hydroxycarbonates of coating elements ( At least one coating element compound selected from hydroxycarbonate).
  • the compound used for the coating may be amorphous or crystalline.
  • the coating element contained in the coating may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, F, or a mixture thereof.
  • the coating can be applied by any method as long as the method does not adversely affect the performance of the positive electrode active material.
  • the method may include any coating method well-known to those of ordinary skill in the art, such as spraying, dipping, and the like.
  • the positive electrode active material layer further includes a binder, and optionally further includes a positive electrode conductive material.
  • the binder improves the bonding of the positive electrode active material particles to each other, and also improves the bonding of the positive electrode active material to the current collector.
  • binders include polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinyl chloride Vinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene butadiene rubber, acrylic (ester) styrene butadiene rubber, epoxy resin, nylon, etc.
  • the positive electrode active material layer includes a positive electrode conductive material, thereby imparting conductivity to the electrode.
  • the positive electrode conductive material may include any conductive material as long as it does not cause a chemical change.
  • Non-limiting examples of positive electrode conductive materials include carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.), metal-based materials (e.g., metal powder, metal fiber, etc., Including, for example, copper, nickel, aluminum, silver, etc.), conductive polymers (for example, polyphenylene derivatives), and mixtures thereof.
  • the positive electrode current collector used in the electrochemical device according to the present application may be aluminum (Al), but is not limited thereto.
  • the electrolyte that can be used in the embodiments of the present application may be an electrolyte known in the prior art.
  • the electrolyte that can be used in the electrolyte of the embodiments of the present application includes, but is not limited to: inorganic lithium salts, such as LiClO 4 , LiAsF 6 , LiPF 6 , LiBF 4 , LiSbF 6 , LiSO 3 F, LiN(FSO 2 ) 2, etc.; Fluorine-containing organic lithium salts, such as LiCF 3 SO 3 , LiN(FSO 2 )(CF 3 SO 2 ), LiN(CF 3 SO 2 ) 2 , LiN(C 2 F 5 SO 2 ) 2 , cyclic 1,3- Lithium hexafluoropropane disulfonimide, lithium cyclic 1,2-tetrafluoroethane disulfonimide, LiN (CF 3 SO 2 ) (C 4 F 9 SO 2 ), LiC (CF 3 SO 2
  • Lithium salt containing dicarboxylic acid complex such as bis(oxalato) lithium borate, difluorooxalic acid Lithium borate, tris(oxalato)lithium, difluorobis(oxala
  • the electrolyte includes a combination of LiPF 6 and LiBF 4.
  • the electrolyte includes a combination of an inorganic lithium salt such as LiPF 6 or LiBF 4 and a fluorine-containing organic lithium salt such as LiCF 3 SO 3 , LiN(CF 3 SO 2 ) 2 , and LiN(C 2 F 5 SO 2 ) 2 .
  • the concentration of the electrolyte is in the range of 0.8 mol/L to 3 mol/L, for example, in the range of 0.8 mol/L to 2.5 mol/L, in the range of 0.8 mol/L to 2 mol/L, 1 mol/L Within the range of L to 2mol/L, for example, 1mol/L, 1.15mol/L, 1.2mol/L, 1.5mol/L, 2mol/L or 2.5mol/L.
  • Solvents that can be used in the electrolyte of the embodiments of the present application include, but are not limited to: carbonate compounds, ester-based compounds, ether-based compounds, ketone-based compounds, alcohol-based compounds, aprotic solvents, or combinations thereof.
  • carbonate compounds include, but are not limited to, linear carbonate compounds, cyclic carbonate compounds, fluorocarbonate compounds, or combinations thereof.
  • chain carbonate compounds include, but are not limited to, diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethylene propyl carbonate ( EPC), ethyl methyl carbonate (MEC) and their combinations.
  • DEC diethyl carbonate
  • DMC dimethyl carbonate
  • DPC dipropyl carbonate
  • MEC methyl propyl carbonate
  • EPC ethylene propyl carbonate
  • MEC ethyl methyl carbonate
  • cyclic carbonate compound are ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinyl ethylene carbonate (VEC), and combinations thereof.
  • fluorocarbonate compound examples include fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate Fluoroethylene, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, carbonic acid 1,2 -Difluoro-1-methylethylene, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate, and combinations thereof.
  • FEC fluoroethylene carbonate
  • 1,2-difluoroethylene carbonate 1,1-difluoroethylene carbonate
  • 1,1,2-trifluoroethylene carbonate Fluoroethylene, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, carbonic acid 1,2 -Difluoro-1-methylethylene, 1,1,2-trifluoro-2-methylethylene carbonate,
  • ester-based compounds include, but are not limited to, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, ⁇ -butyrolactone, decanolide, Valerolactone, mevalonolactone, caprolactone, methyl formate, and combinations thereof.
  • ether-based compounds include, but are not limited to, dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane Alkanes, ethoxymethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, and combinations thereof.
  • ketone-based compounds include, but are not limited to, cyclohexanone.
  • alcohol-based compounds include, but are not limited to, ethanol and isopropanol.
  • aprotic solvents include, but are not limited to, dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl- 2-pyrrolidone, formamide, dimethylformamide, acetonitrile, nitromethane, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate esters and combinations thereof.
  • a separator is provided between the positive electrode and the negative electrode to prevent short circuits.
  • the material and shape of the isolation film that can be used in the embodiments of the present application are not particularly limited, and they can 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 the electrolyte of the present application.
  • the isolation film may include a substrate layer and a surface treatment layer.
  • the substrate layer is a non-woven fabric, film or composite film with a porous structure, and the material of the substrate layer is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate and polyimide.
  • a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric, or a polypropylene-polyethylene-polypropylene porous composite film can be selected.
  • the porous structure can improve the heat resistance, oxidation resistance and electrolyte infiltration performance of the isolation membrane, and enhance the adhesion between the isolation membrane and the pole piece.
  • a surface treatment layer is provided on at least one surface of the substrate layer.
  • the surface treatment layer may be a polymer layer or an inorganic substance layer, or a layer formed by a mixed polymer and an inorganic substance.
  • the inorganic layer includes inorganic particles and a binder.
  • the inorganic particles are selected from alumina, silica, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, ceria, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, One or a combination of yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate.
  • the binder is selected from polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, One or a combination of polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene.
  • the polymer layer contains a polymer, and the material of the polymer is selected from polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride, poly At least one of (vinylidene fluoride-hexafluoropropylene).
  • the electrochemical device of the present application includes 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 application also provides an electronic device, which includes the electrochemical device according to the application.
  • the electrochemical device of the present application is not particularly limited, and it can be used in any electronic device 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.
  • the coke was crushed so that the median particle diameter Dv50 was in the range of 3 ⁇ m to 10 ⁇ m, and then a binder pitch with a softening point of 100-300°C was added (the addition amount of pitch in Examples 1-16 and 18-39 was 15wt%, The addition amount of asphalt in Example 17 is 5wt%).
  • the mixture of the two is put into the granulation equipment for granulation, during which it is continuously stirred and heated to 500°C to 1000°C, and then the graphitization process (where the graphitization temperature is controlled at 2000°C to 3500°C), the following implementation is obtained
  • the graphite anode active material used in the example.
  • the coke is crushed so that the median particle diameter Dv50 is in the range of 3 ⁇ m to 10 ⁇ m, and placed in a granulation equipment for granulation. During the process, it is continuously stirred and heated to 500°C to 1000°C, and then the graphitization process (where the graphitization temperature Controlled at 2000°C to 3500°C) to obtain the graphite negative electrode active material used in Comparative Example 1.
  • the graphite negative electrode active material, styrene butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC) prepared above are dispersed in deionized water at a weight ratio of 97.7:1.2:1.1, fully stirred and mixed uniformly to obtain negative electrode slurry.
  • the negative electrode slurry is coated on the negative electrode current collector, dried, and cold pressed to form a negative electrode active material layer, and then cut pieces and welded tabs to obtain the negative electrode.
  • Graphite particles of different particle sizes can be obtained by crushing and grading the raw materials using any known technology.
  • LiCoO 2 lithium cobaltate
  • acetylene black acetylene black
  • PVDF polyvinylidene fluoride
  • NMP N-methylpyrrolidone
  • ethylene carbonate (EC), propylene carbonate (PC) and diethyl carbonate (DEC) were mixed in a weight ratio of 1:1:1, and LiPF 6 was added and mixed uniformly. Add 3% of fluoroethylene carbonate and mix uniformly to obtain an electrolyte, in which the concentration of LiPF 6 is 1.15 mol/L.
  • a 12 ⁇ m thick polyethylene (PE) porous polymer film is used as the separator.
  • the electrolyte is vacuum encapsulated, standing, forming, shaping, capacity testing and other processes to obtain a lithium-ion battery.
  • TristarII3020M Use a specific surface area analyzer (TristarII3020M) to measure the specific surface area of the negative electrode active material by the nitrogen adsorption/desorption method: dry the negative electrode active material sample in a vacuum drying oven, then put it into a sample tube and measure it in the analyzer.
  • 0.05C refers to the current value under 0.05 times the design gram capacity
  • 0.1C refers to the current value under 0.1 times the design gram capacity.
  • the cyclic thickness expansion rate corresponding to the number of cyclic turns (H n -H 0 )/H 0 ⁇ 100%.
  • Table 1 shows the influence of the characteristics of the negative active material on the gram capacity and cycle thickness expansion rate of the lithium ion battery during the preparation of the negative active material.
  • the lithium ion battery when preparing the negative active material, an appropriate amount of high-viscosity binder is added so that the D 2 v50/D 1 v50 of the negative active material is not less than 0.8, and the lithium ion battery has a high gram capacity. At the same time, it also has a low cycle thickness expansion rate, achieving a balance between high gram capacity and low cycle thickness expansion rate.
  • the median diameter D 1 v50 of the negative active material gradually increases in the range of 10 ⁇ m to 25 ⁇ m, the median diameter of the negative active material under a pressure of 1t D 2 v50 and D 1 v50 ratio D 2 v50 / D 1 v50 reduced, the negative electrode active material (BET 2 -BET 1) / BET 1 is increased, the weight of carbon to oxygen ratio of the elements is increased, so that the lithium ion battery The gram capacity increases, and the cyclic thickness expansion rate decreases.
  • Table 2 shows the influence of D 1 v90/D 1 v10 and C004/C110 of the negative active material on the first-time efficiency and cycle thickness expansion rate of lithium-ion batteries. Except for the parameters listed in Table 2, the conditions of Examples 21-39 are the same as those of Example 8.
  • the results show that when the D 1 v90/D 1 v10 of the negative electrode active material is less than 3.5, the first-time efficiency of the lithium-ion battery is significantly increased.
  • the D 1 v90/D 1 v10 of the negative electrode active material gradually decreases in the range of less than 3.5, the first-time efficiency of the lithium-ion battery does not change much, and the cycle thickness expansion rate gradually decreases.
  • the C004/C110 of the negative active material layer gradually decreases in the range of 5.7 to 18, the grain size La of the graphite particles decreases, Lc increases, and the porosity increases, and the cycle thickness expansion rate of the lithium ion battery gradually decreases. The efficiency dropped slightly for the first time.
  • the lithium-ion battery has a balanced initial efficiency and cycle thickness expansion rate.
  • Table 3 shows the influence of the characteristics of the negative electrode active material of the lithium-ion battery on the first-time efficiency and cycle thickness expansion rate of the lithium-ion battery under the fully discharged state.
  • Figure 1 shows the cyclic thickness expansion rate of the lithium ion batteries of Example 8 and Comparative Example 1 with the number of cycles. The results show that compared with Comparative Example 1, the lithium ion battery of Example 8 has a significantly lower cycle thickness expansion rate. With the increase of the number of cycles, the greater the difference in the expansion rate of the cycle thickness between the two.
  • references to “embodiments”, “parts of embodiments”, “one embodiment”, “another example”, “examples”, “specific examples” or “partial examples” throughout the specification mean that 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 “exemplary”, 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

本申请涉及一种负极活性材料及使用其的电化学装置和电子装置。具体而言,本申请提供一种负极活性材料,其中所述负极活性材料具有中值粒径D 1v50,所述负极活性材料在1t压力下具有中值粒径D 2v50,且D 2v50/D 1v50为不小于0.8。本申请的负极活性材料有助于实现电化学装置的高容量和高循环膨胀性能的平衡。

Description

负极活性材料及使用其的电化学装置和电子装置 技术领域
本申请涉及储能领域,具体涉及一种负极活性材料及使用其的电化学装置和电子装置。
背景技术
电化学装置(例如,锂离子电池)由于具有环境友好、工作电压高、比容量大和循环寿命长等优点而被广泛应用,已成为当今世界最具发展潜力的新型绿色化学电源。小尺寸锂离子电池通常用作驱动便携式电子通讯设备(例如,便携式摄像机、移动电话或者笔记本电脑等)的电源,特别是高性能便携式设备的电源。近年来,具有高输出特性的中等尺寸和大尺寸锂例子电池被发展应用于电动汽车(EV)和大规模储能系统(ESS)。随着锂离子电池的广泛应用,其循环性能已成为亟待解决的关键技术问题。改进电极中的活性材料是解决上述问题的研究方向之一。
有鉴于此,确有必要提供一种改进的负极活性材料及使用其的电化学装置和电子装置。
发明内容
本申请通过提供一种负极活性材料及使用其的电化学装置和电子装置以试图在至少某种程度上解决至少一种存在于相关领域中的问题。
根据本申请的一个方面,本申请提供了一种负极活性材料,其中所述负极活性材料具有中值粒径D 1v50,所述负极活性材料在1t压力下具有中值粒径D 2v50,且D 2v50/D 1v50为不小于0.8。在一些实施例中,所述负极活性材料的D 2v50/D 1v50为不小于0.9。在一些实施例中,所述负极活性材料的D 2v50/D 1v50为0.8、0.85、0.9、0.95或1.0。
根据本申请的实施例,所述负极活性材料具有比表面积BET 1,所述BET 1为0.6m 2/g至2.0m 2/g,所述负极活性材料在1t压力下具有比表面积BET 2,且(BET 2-BET 1)/BET 1≤1。在一些实施例中,所述BET 1为0.7m 2/g至1.8m 2/g。在一些实施例中,所述BET 1为0.8m 2/g至1.6m 2/g。在一些实施例中,所述BET 1为0.6m 2/g、0.7m 2/g、0.8m 2/g、0.9m 2/g、1.0m 2/g、1.1m 2/g、1.2m 2/g、1.3m 2/g、1.4m 2/g、1.5m 2/g、1.6m 2/g、1.7 m 2/g、1.8m 2/g、1.9m 2/g或2.0m 2/g。
根据本申请的实施例,所述负极活性材料包括石墨颗粒,所述石墨颗粒满足条件(a)至(c)中的至少一者:
(a)D 1v50为10μm至25μm;
(b)D 1v90与D 1v10满足D 1v90/D 1v10小于3.5;
(c)通过X射线衍射法,所述石墨颗粒沿水平方向的晶粒尺寸La为160nm至165nm,所述石墨颗粒沿垂直方向的晶粒尺寸Lc为30nm至32nm。
在一些实施例中,所述石墨颗粒的D 1v50为15μm至20μm。在一些实施例中,所述石墨颗粒的D 1v50为10μm、12μm、15μm、18μm、20μm、22μm或25μm。
在一些实施例中,所述石墨颗粒的D 1v90/D 1v10小于3.0。在一些实施例中,所述石墨颗粒的D 1v90/D 1v10小于2.5。在一些实施例中,所述石墨颗粒的D 1v90/D 1v10小于2.0。
在一些实施例中,通过X射线衍射法,所述石墨颗粒沿水平方向的晶粒尺寸La为160nm、161nm、162nm、163nm、164nm或165nm,所述石墨颗粒沿垂直方向的晶粒尺寸Lc为30nm、31nm或32nm。
根据本申请的另一个方面,本申请提供一种电化学装置,其包含负极,所述负极包括负极集流体和负极活性材料层,所述负极活性材料层包括根据本申请所述的负极活性材料。
根据本申请的实施例,所述负极活性材料层满足条件(d)至(f)中的至少一者:
(d)所述负极活性材料层包含碳元素和氧元素,所述碳元素的含量与所述氧元素的含量的比为2:3至990:1;
(e)由X射线衍射图谱测定得到的所述负极活性材料层的(004)面的峰面积C004和(110)面的峰面积C110的比值C004/C110为5.7至18;
(f)所述负极活性材料层的孔隙率为20%至30%。
在一些实施例中,所述碳元素的含量与所述氧元素的含量的比为1:1至800:1。在一些实施例中,所述碳元素的含量与所述氧元素的含量的比为5:1至500:1。在一些实施例中,所述碳元素的含量与所述氧元素的含量的比为10:1至300:1。在一些实施例中,所述碳元素的含量与所述氧元素的含量的比为50:1至100:1。在一些实施例中,所述碳元素的含量与所述氧元素的含量的比为2:3、1:1、5:1、10:1、20:1、50:1、100:1、200:1、300:1、400:1、500:1、600:1、700:1、800:1、900:1或990:1。
在一些实施例中,所述负极活性材料层的C004/C110为6.0至10.0。在一些实施例中,所述负极活性材料层的C004/C110为7.0至8.0。
在一些实施例中,所述负极活性材料层的孔隙率为20%至25%。在一些实施例中,所述负极活性材料层的孔隙率为20%、21%、22%、23%、24%、25%、26%、27%、28%、29%或30%。
根据本申请的实施例,所述电化学装置在满放状态下,由X射线衍射图谱测定得到的所述负极活性材料的(004)面的峰面积C004'和(110)面的峰面积C110'的比值C004'/C110'为6.8至17.2。在一些实施例中,所述负极活性材料的C004'/C110'为7.0至16.6。在一些实施例中,所述负极活性材料的C004'/C110'为10.0至16.0。在一些实施例中,所述负极活性材料的C004'/C110'为11.0至15.5。
根据本申请的实施例,所述电化学装置在满放状态下,所述负极活性材料具有中值粒径D av50,所述负极活性材料在1t压力下具有中值粒径D bv50,且D bv50/D av50为不小于0.9。在一些实施例中,所述负极活性材料的D bv50/D av50为不小于0.91。在一些实施例中,所述负极活性材料的D bv50/D av50为0.92、0.95、0.98或1.0。
根据本申请的实施例,所述电化学装置在满放状态下,所述负极活性材料的中值粒径D av50为8μm至20μm。在一些实施例中,所述负极活性材料的D av50为10μm至15μm。在一些实施例中,所述负极活性材料的D av50为8μm、10μm、12μm、15μm、18μm或20μm。
根据本申请的实施例,所述电化学装置在满放状态下,所述负极活性材料具有比表面积BET a,所述负极活性材料在1t压力下具有比表面积BET b,且(BET b-BET a)/BET a<0.6。
根据本申请的又一个方面,本申请提供了一种电子装置,其包括根据本申请所述的电化学装置。
本申请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果来获得其他实施例的附图。
图1展示了根据本申请实施例22和对比例1的锂离子电池在45℃下的随循环次数的膨胀百分比。
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。
在具体实施方式及权利要求书中,由术语“中的至少一种”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中的至少一种”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中的至少一种”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可包含单个元件或多个元件。项目B可包含单个元件或多个元件。项目C可包含单个元件或多个元件。
如本文中所使用,“Dv50”指的是负极活性材料在体积基准的粒度分布中从小粒径侧起达到体积累积50%的粒径,即,小于此粒径的负极活性材料的体积占负极活性材料总体积的50%。
如本文中所使用,“Dv10”指的是负极活性材料在体积基准的粒度分布中从小粒径侧起达到体积累积10%的粒径,即,小于此粒径的负极活性材料的体积占负极活性材料总体积的10%。
如本文中所使用,“Dv90”指的是负极活性材料在体积基准的粒度分布中从小粒径侧起达到体积累积90%的粒径,,即,小于此粒径的负极活性材料的体积占负极活性材料总体积的90%。
负极活性材料的Dv50、Dv10和Dv90可以用本领域公知的方法进行测定,例如用激光粒度分析仪(例如,马尔文粒度测试仪)测定。
如本文中所使用,“满放状态”指的是在25℃的环境中,将电化学装置在1C(即,在1小时内完全放掉理论容量的电流值)的放电电流下进行恒流放电至电压为3.0V所达到的状态。
除非有特别说明,本申请的电化学装置处于50%荷电状态(SOC)下。
在电化学装置(下文以锂离子电池为例)的循环过程中,锂离子的嵌入会导致电化学装置发生膨胀,这种现象在高温情况下尤为严重。提高负极活性材料(例如,石墨颗粒)的复合程度是改善锂离子电池的循环性能的手段之一。通过使用高粘性的粘结剂或 提高粘结剂的用量可使负极活性材料的一次颗粒复合形成二次颗粒。本申请通过改善二次颗粒的强度实现了锂离子电池的高容量和循环过程中厚度膨胀的平衡。
具体来说,本申请提供了一种负极活性材料,其中所述负极活性材料具有中值粒径D 1v50,所述负极活性材料在1t压力下具有中值粒径D 2v50,且D 2v50/D 1v50为不小于0.8。在一些实施例中,所述负极活性材料的D 2v50/D 1v50为不小于0.9。在一些实施例中,所述负极活性材料的D 2v50/D 1v50为0.8、0.85、0.9、0.95或1.0。负极活性材料的D 2v50/D 1v50可反映出负极活性材料在受压后的颗粒粒径变化率。负极活性材料的D 2v50/D 1v50越大,负极活性材料在受压后的颗粒破碎程度越小,颗粒破碎数量越少,破碎颗粒占总负极活性材料颗粒的比率(即,颗粒破碎率)越低,负极活性材料的强度越高,使得负极活性材料由受压产生的未涂覆粘结剂的断面减少,由此可减少固体电解质界面(SEI)膜的形成,有助于改善锂离子电池的容量、首次效率和循环厚度膨胀率。当负极活性材料的D 2v50/D 1v50在上述范围内时,负极活性材料具有高强度,其有助于实现锂离子电池的高克容量和低循环厚度膨胀率的平衡。
本申请的负极活性材料可通过以下方法得到:在负极活性材料的一次颗粒中添加高粘性添加剂,得到混合物,烧结所述混合物,得到负极活性材料的二次颗粒,其中所述高粘性添加剂包括油系高温沥青、煤系高温沥青或树脂高分子材料中的至少一种,基于所述负极活性材料的总重量,所述高粘性添加剂的含量为不大于30wt%。
根据本申请的实施例,所述负极活性材料的中值粒径D 1v50为10μm至25μm。在一些实施例中,所述负极活性材料的D 1v50为15μm至20μm。在一些实施例中,所述负极活性材料的D 1v50为10μm、12μm、15μm、18μm、20μm、22μm或25μm。
根据本申请的实施例,所述负极活性材料在1t压力下的中值粒径D 2v50为8μm至20μm。在一些实施例中,所述负极活性材料的D 2v50为10μm至15μm。在一些实施例中,所述负极活性材料的D 2v50为8μm、10μm、12μm、15μm、18μm或20μm。
根据本申请的实施例,所述负极活性材料的D 1v90与D 1v10满足D 1v90/D 1v10小于3.5。在一些实施例中,所述负极活性材料的D 1v90/D 1v10小于3.0。在一些实施例中,所述负极活性材料的D 1v90/D 1v10小于2.5。在一些实施例中,所述负极活性材料的D 1v90/D 1v10小于2.0。
根据本申请的实施例,所述负极活性材料包括晶粒,通过X射线衍射法,所述晶粒沿水平方向的晶粒尺寸La为160nm至165nm,所述晶粒沿垂直方向的晶粒尺寸Lc为30nm至32nm。在一些实施例中,所述负极活性材料包括晶粒,通过X射线衍射法, 所述晶粒沿水平方向的晶粒尺寸La为161nm至164nm,所述晶粒沿垂直方向的晶粒尺寸Lc为30.5nm至31.5nm。在一些实施例中,通过X射线衍射法,所述石墨颗粒沿水平方向的晶粒尺寸La为160nm、161nm、162nm、163nm、164nm或165nm,所述石墨颗粒沿垂直方向的晶粒尺寸Lc为30nm、31nm或32nm。
根据本申请的实施例,所述负极活性材料包括石墨颗粒,所述石墨颗粒具有与所述负极活性材料相同的D 1v50、D 2v50、D 1v90和D 1v10。在一些实施例中,所述负极活性材料为石墨颗粒。
根据本申请的实施例,所述负极活性材料具有比表面积BET 1,所述BET 1为0.6m 2/g至2.0m 2/g,所述负极活性材料在1t压力下具有比表面积BET 2,且(BET 2-BET 1)/BET 1≤1。当所述负极活性材料满足(BET 2-BET 1)/BET 1≤1时,相较于未受压的负极活性材料,受压后的负极活性材料比表面积增长率不大于100%。负极活性材料的比表面积增长率越小,负极活性材料的强度越高,负极活性材料由受压产生的未涂覆粘结剂的断面减少,形成的固体电解质界面(SEI)膜减少,有助于改善锂离子电池的容量、首次效率和循环厚度膨胀率。
在一些实施例中,所述BET 1为0.7m 2/g至1.8m 2/g。在一些实施例中,所述BET 1为0.8m 2/g至1.6m 2/g。在一些实施例中,所述BET 1为0.6m 2/g、0.7m 2/g、0.8m 2/g、0.9m 2/g、1.0m 2/g、1.1m 2/g、1.2m 2/g、1.3m 2/g、1.4m 2/g、1.5m 2/g、1.6m 2/g、1.7m 2/g、1.8m 2/g、1.9m 2/g或2.0m 2/g。
根据本申请的实施例,所述负极活性材料在1t压力下的比表面积BET 2为1.2m 2/g至4.0m 2/g。在一些实施例中,所述负极活性材料的BET 2为1.5m 2/g至3.0m 2/g。在一些实施例中,所述负极活性材料的BET 2为1.2m 2/g、1.5m 2/g、2m 2/g、2.5m 2/g、3m 2/g、3.5m 2/g或4.0m 2/g。
负极活性材料在1t压力下的参数可参考中华人民共和国国家标准GB/T24533-2009中的步骤得到。
负极活性材料的比表面积可通过以下方法得到:
使用比表面积分析仪(例如TristarⅡ3020M),通过氮吸附/脱附法测量负极活性材料的比表面积:将负极活性材料样品在真空干燥箱中烘干,然后装入样品管中在分析仪中测量。本申请还提供了一种电化学装置,其包含负极,所述负极包括负极集流体和负极活性材料层。
负极
在本申请的电化学装置中,所述负极活性材料层包括根据本申请所述的负极活性材料。
根据本申请的实施例,所述负极活性材料层包含碳元素和氧元素,所述碳元素的含量与所述氧元素的含量的比为2:3至990:1。在一些实施例中,所述碳元素的含量与所述氧元素的含量的比为1:1至800:1。在一些实施例中,所述碳元素的含量与所述氧元素的含量的比为5:1至500:1。在一些实施例中,所述碳元素的含量与所述氧元素的含量的比为10:1至300:1。在一些实施例中,所述碳元素的含量与所述氧元素的含量的比为50:1至100:1。在一些实施例中,所述碳元素的含量与所述氧元素的含量的比为2:3、1:1、5:1、10:1、20:1、50:1、100:1、200:1、300:1、400:1、500:1、600:1、700:1、800:1、900:1或990:1。当负极活性材料层中的碳元素的含量与所述氧元素的含量的比在上述范围内时,负极活性材料颗粒的粒径和石墨化度在适合的范围内,有助于改善锂离子电池的容量和循环厚度膨胀率。
根据本申请的实施例,在所述负极活性材料层中,由X射线衍射图谱测定得到的所述负极活性材料层的(004)面的峰面积C004和(110)面的峰面积C110的比值C004/C110为5.7至11.2。由X射线衍射图谱测定得到的所述负极活性材料层的C004/C110值可反映出负极活性材料颗粒的各向异性。C004/C110值越小,各向异性越小,有助于改善锂离子电池的循环厚度膨胀率。在一些实施例中,所述负极活性材料层的C004/C110为6.0至10.0。在一些实施例中,所述负极活性材料层的C004/C110为7.0至8.0。
根据本申请的实施例,所述负极活性材料层的孔隙率为20%至30%。在一些实施例中,所述负极活性材料层的孔隙率为20%至25%。在一些实施例中,所述负极活性材料层的孔隙率为20%、21%、22%、23%、24%、25%、26%、27%、28%、29%或30%。
根据本申请的实施例,所述电化学装置在满放状态下,由X射线衍射图谱测定得到的所述负极活性材料的(004)面的峰面积C004'和(110)面的峰面积C110'的比值C004'/C110'为6.8至17.2。在一些实施例中,所述负极活性材料的C004'/C110'为7.0至16.5。在一些实施例中,所述负极活性材料的C004'/C110'为10.0至15.0。在一些实施例中,所述负极活性材料的C004'/C110'为12.0至14.0。当负极活性材料的C004'/C110'时,处于满放状态下的电化学装置中的负极活性材料颗粒的各向异性依然较低,其可反映出负极活性材料具有高强度。
根据本申请的实施例,所述电化学装置在满放状态下,所述负极活性材料具有中值 粒径D av50,所述负极活性材料在1t压力下具有中值粒径D bv50,且D bv50/D av50为不小于0.9。负极活性材料的D bv50/D av50可反映出处于满放状态下的电化学装置中的负极活性材料在受压后的颗粒破碎程度。负极活性材料的D bv50/D av50越大,处于满放状态下的电化学装置中的负极活性材料在受压后的颗粒破碎程度越小,颗粒破碎数量越少,破碎颗粒占总负极活性材料颗粒的比率(即,颗粒破碎率)越低,负极活性材料的强度越高。当负极活性材料的D bv50/D av50在上述范围内时,处于满放状态下的电化学装置中的负极活性材料依然具有高强度,其有助于进一步提升锂离子电池的首次效率并降低其循环厚度膨胀率。在一些实施例中,所述负极活性材料的D bv50/D av50为0.92、0.95、0.98或1.0。
根据本申请的实施例,所述电化学装置在满放状态下,所述负极活性材料的中值粒径D av50为8μm至20μm。在一些实施例中,所述负极活性材料的D av50为10μm至15μm。在一些实施例中,所述负极活性材料的D av50为8μm、10μm、12μm、15μm、18μm或20μm。
根据本申请的实施例,所述电化学装置在满放状态下,所述负极活性材料在1t压力下具有中值粒径D bv50为7.2μm至18μm。在一些实施例中,所述负极活性材料的D bv50为8μm至15μm。在一些实施例中,所述负极活性材料的D bv50为7.2μm、8μm、10μm、12μm、15μm或18μm。
根据本申请的实施例,所述电化学装置在满放状态下,所述负极活性材料具有比表面积BET a,所述负极活性材料在1t压力下具有比表面积BET b,且(BET b-BET a)/BET a<0.6。当所述负极活性材料满足(BET b-BET a)/BET a<0.6时,相较于未受压的负极活性材料,受压后的负极活性材料比表面积增长率小于60%。当处于满放状态下的电化学装置中的负极活性材料的比表面积符合上述关系时,可反映出负极活性材料的强度较高。
根据本申请的实施例,所述电化学装置在满放状态下,所述负极活性材料的比表面积BET a为0.6m 2/g至2.0m 2/g。在一些实施例中,所述负极活性材料的BET a为0.8m 2/g至1.5m 2/g。在一些实施例中,所述负极活性材料的BET a为1.0m 2/g至1.2m 2/g。在一些实施例中,所述负极活性材料的BET a为0.6m 2/g、0.7m 2/g、0.8m 2/g、0.9m 2/g、1.0m 2/g、1.1m 2/g、1.2m 2/g、1.3m 2/g、1.4m 2/g、1.5m 2/g、1.6m 2/g、1.7m 2/g、1.8m 2/g、1.9m 2/g或2.0m 2/g。
根据本申请的实施例,所述电化学装置在满放状态下,所述负极活性材料在1t压力下的比表面积BET b为0.96m 2/g至3.2m 2/g。在一些实施例中,所述负极活性材料的 BET 2为1.0m 2/g至3.0m 2/g。在一些实施例中,所述负极活性材料的BET 2为1.5m 2/g至2.0m 2/g。在一些实施例中,所述负极活性材料的BET 2为0.96m 2/g、1.0m 2/g、1.2m 2/g、1.5m 2/g、1.8m 2/g、2.0m 2/g、2.2m 2/g、2.5m 2/g、2.8m 2/g、3.0m 2/g或3.2m 2/g。
根据本申请的实施例,用于本申请所述的负极集流体可以选自铜箔、镍箔、不锈钢箔、钛箔、泡沫镍、泡沫铜、覆有导电金属的聚合物基底和它们的组合。
根据本申请的实施例,所述负极进一步包括导电层。在一些实施例中,所述导电层的导电材料可以包括任何导电材料,只要它不引起化学变化。导电材料的非限制性示例包括基于碳的材料(例如,天然石墨、人造石墨、碳黑、乙炔黑、科琴黑、碳纤维、碳纳米管、石墨烯等)、基于金属的材料(例如,金属粉、金属纤维等,例如铜、镍、铝、银等)、导电聚合物(例如,聚亚苯基衍生物)和它们的混合物。
根据本申请的实施例,所述负极进一步包括粘结剂,所述粘结剂选自以下的至少一种: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、环氧树脂或尼龙等。
根据本申请的实施例,负极可通过现有技术中已知的任何方法制造。在一些实施例中,负极可以通过在负极活性材料中加入粘合剂和溶剂并根据需要加入增稠剂、导电材料、填充材料等而制成浆料,将该浆料其涂布于集流体上,干燥后进行压制而形成。
根据本申请的实施例,当负极包括合金材料时,可使用蒸镀法、溅射法、镀敷法等方法形成负极活性材料层。
正极
正极包括正极集流体和设置在所述正极集流体上的正极活性材料。正极活性材料的具体种类均不受到具体的限制,可根据需求进行选择。
根据本申请的实施例,正极活性材料包括可逆地嵌入和脱嵌锂离子的化合物。在一些实施例中,正极活性材料可以包括复合氧化物,所述复合氧化物含有锂以及从钴、锰和镍中选择的至少一种元素。在又一些实施例中,正极活性材料选自钴酸锂(LiCoO 2)、锂镍锰钴三元材料、锰酸锂(LiMn 2O 4)、镍锰酸锂(LiNi 0.5Mn 1.5O 4)、磷酸铁锂(LiFePO 4)中的一种或几种。
根据本申请的实施例,正极活性材料层可以在表面上具有涂层,或者可以与具有涂层的另一化合物混合。所述涂层可以包括从涂覆元素的氧化物、涂覆元素的氢氧化物、 涂覆元素的羟基氧化物、涂覆元素的碳酸氧盐(oxycarbonate)和涂覆元素的羟基碳酸盐(hydroxycarbonate)中选择的至少一种涂覆元素化合物。用于涂层的化合物可以是非晶的或结晶的。在涂层中含有的涂覆元素可以包括Mg、Al、Co、K、Na、Ca、Si、Ti、V、Sn、Ge、Ga、B、As、Zr、F或它们的混合物。可以通过任何方法来施加涂层,只要所述方法不对正极活性材料的性能产生不利影响即可。例如,所述方法可以包括对本领域普通技术人员来说众所周知的任何涂覆方法,例如喷涂、浸渍等。
根据本申请的实施例,正极活性材料层还包含粘合剂,并且可选地还包括正极导电材料。
粘合剂提高正极活性材料颗粒彼此间的结合,并且还提高正极活性材料与集流体的结合。粘合剂的非限制性示例包括聚乙烯醇、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。
正极活性材料层包括正极导电材料,从而赋予电极导电性。所述正极导电材料可以包括任何导电材料,只要它不引起化学变化。正极导电材料的非限制性示例包括基于碳的材料(例如,天然石墨、人造石墨、碳黑、乙炔黑、科琴黑、碳纤维等)、基于金属的材料(例如,金属粉、金属纤维等,包括例如铜、镍、铝、银等)、导电聚合物(例如,聚亚苯基衍生物)和它们的混合物。
用于根据本申请的电化学装置的正极集流体可以是铝(Al),但不限于此。
电解液
可用于本申请实施例的电解液可以为现有技术中已知的电解液。可用于本申请实施例的电解液中的电解质包括、但不限于:无机锂盐,例如LiClO 4、LiAsF 6、LiPF 6、LiBF 4、LiSbF 6、LiSO 3F、LiN(FSO 2) 2等;含氟有机锂盐,例如LiCF 3SO 3、LiN(FSO 2)(CF 3SO 2)、LiN(CF 3SO 2) 2、LiN(C 2F 5SO 2) 2、环状1,3-六氟丙烷二磺酰亚胺锂、环状1,2-四氟乙烷二磺酰亚胺锂、LiN(CF 3SO 2)(C 4F 9SO 2)、LiC(CF 3SO 2) 3、LiPF 4(CF 3) 2、LiPF 4(C 2F 5) 2、LiPF 4(CF 3SO 2) 2、LiPF 4(C 2F 5SO 2) 2、LiBF 2(CF 3) 2、LiBF2(C2F5)2、LiBF 2(CF 3SO 2) 2、LiBF 2(C 2F 5SO 2) 2;含二羧酸配合物锂盐,例如双(草酸根合)硼酸锂、二氟草酸根合硼酸锂、三(草酸根合)磷酸锂、二氟双(草酸根合)磷酸锂、四氟(草酸根合)磷酸锂等。另外,上述电解质可以单独使用一种,也可以同时使用两种或两种以上。例如,在一些实施例中,电解质包括LiPF 6和LiBF 4的组合。在一些实施例中,电解质包括LiPF 6或LiBF 4 等无机锂盐与LiCF 3SO 3、LiN(CF 3SO 2) 2、LiN(C 2F 5SO 2) 2等含氟有机锂盐的组合。
在一些实施例中,电解质的浓度在0.8mol/L至3mol/L的范围内,例如0.8mol/L至2.5mol/L的范围内、0.8mol/L至2mol/L的范围内、1mol/L至2mol/L的范围内、又例如为1mol/L、1.15mol/L、1.2mol/L、1.5mol/L、2mol/L或2.5mol/L。
可用于本申请实施例的电解液中的溶剂包括,但不限于:碳酸酯化合物、基于酯的化合物、基于醚的化合物、基于酮的化合物、基于醇的化合物、非质子溶剂或它们的组合。
碳酸酯化合物的实例包括,但不限于,链状碳酸酯化合物、环状碳酸酯化合物、氟代碳酸酯化合物或它们的组合。
链状碳酸酯化合物的实例包括,但不限于,碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸甲乙酯(MEC)及它们的组合。所述环状碳酸酯化合物的实例为碳酸亚乙酯(EC)、碳酸亚丙酯(PC)、碳酸亚丁酯(BC)、碳酸乙烯基亚乙酯(VEC)及它们的组合。所述氟代碳酸酯化合物的实例为碳酸氟代亚乙酯(FEC)、碳酸1,2-二氟亚乙酯、碳酸1,1-二氟亚乙酯、碳酸1,1,2-三氟亚乙酯、碳酸1,1,2,2-四氟亚乙酯、碳酸1-氟-2-甲基亚乙酯、碳酸1-氟-1-甲基亚乙酯、碳酸1,2-二氟-1-甲基亚乙酯、碳酸1,1,2-三氟-2-甲基亚乙酯、碳酸三氟甲基亚乙酯及它们的组合。
基于酯的化合物的实例包括,但不限于,乙酸甲酯、乙酸乙酯、乙酸正丙酯、乙酸叔丁酯、丙酸甲酯、丙酸乙酯、γ-丁内酯、癸内酯、戊内酯、甲瓦龙酸内酯、己内酯、甲酸甲酯及它们的组合。
基于醚的化合物的实例包括,但不限于,二丁醚、四甘醇二甲醚、二甘醇二甲醚、1,2-二甲氧基乙烷、1,2-二乙氧基乙烷、乙氧基甲氧基乙烷、2-甲基四氢呋喃、四氢呋喃及它们的组合。
基于酮的化合物的实例包括,但不限于,环己酮。
基于醇的化合物的实例包括,但不限于,乙醇和异丙醇。
非质子溶剂的实例包括,但不限于,二甲亚砜、1,2-二氧戊环、环丁砜、甲基环丁砜、1,3-二甲基-2-咪唑烷酮、N-甲基-2-吡咯烷酮、甲酰胺、二甲基甲酰胺、乙腈、硝基甲烷、磷酸三甲酯、磷酸三乙酯、磷酸三辛酯、和磷酸酯及它们的组合。
隔离膜
在一些实施例中,正极与负极之间设有隔离膜以防止短路。可用于本申请的实施例 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,隔离膜包括由对本申请的电解液稳定的材料形成的聚合物或无机物等。
例如,隔离膜可包括基材层和表面处理层。基材层为具有多孔结构的无纺布、膜或复合膜,基材层的材料选自聚乙烯、聚丙烯、聚对苯二甲酸乙二醇酯和聚酰亚胺中的至少一种。具体的,可选用聚丙烯多孔膜、聚乙烯多孔膜、聚丙烯无纺布、聚乙烯无纺布或聚丙烯-聚乙烯-聚丙烯多孔复合膜。多孔结构可以提升隔离膜的耐热性能、抗氧化性能和电解质浸润性能,增强隔离膜与极片之间的粘接性。
基材层的至少一个表面上设置有表面处理层,表面处理层可以是聚合物层或无机物层,也可以是混合聚合物与无机物所形成的层。
无机物层包括无机颗粒和粘结剂,无机颗粒选自氧化铝、氧化硅、氧化镁、氧化钛、二氧化铪、氧化锡、二氧化铈、氧化镍、氧化锌、氧化钙、氧化锆、氧化钇、碳化硅、勃姆石、氢氧化铝、氢氧化镁、氢氧化钙和硫酸钡中的一种或几种的组合。粘结剂选自聚偏氟乙烯、偏氟乙烯-六氟丙烯的共聚物、聚酰胺、聚丙烯腈、聚丙烯酸酯、聚丙烯酸、聚丙烯酸盐、聚乙烯呲咯烷酮、聚乙烯醚、聚甲基丙烯酸甲酯、聚四氟乙烯和聚六氟丙烯中的一种或几种的组合。
聚合物层中包含聚合物,聚合物的材料选自聚酰胺、聚丙烯腈、丙烯酸酯聚合物、聚丙烯酸、聚丙烯酸盐、聚乙烯呲咯烷酮、聚乙烯醚、聚偏氟乙烯、聚(偏氟乙烯-六氟丙烯)中的至少一种。
应用
本申请的电化学装置包括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。
本申请另提供了一种电子装置,其包括根据本申请的电化学装置。
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电子装置。在一些实施例中,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。
下面以锂离子电池为例并且结合具体的实施例说明锂离子电池的制备,本领域的技术人员将理解,本申请中描述的制备方法仅是实例,其他任何合适的制备方法均在本申请的范围内。
实施例
以下说明根据本申请的锂离子电池的实施例和对比例进行性能评估。
一、锂离子电池的制备
1、负极的制备
将焦炭破碎使其中值粒径Dv50在3μm至10μm的范围内,然后加入软化点为100-300℃的粘结剂沥青(实施例1-16和18-39中沥青的添加量为15wt%,实施例17中沥青的添加量为5wt%)。将两者的混合物置入造粒设备中进行造粒,期间不停搅拌并加热至500℃至1000℃,然后进行石墨化工艺(其中石墨化温度控制在2000℃至3500℃),得到以下实施例中使用的石墨负极活性材料。
将焦炭破碎使其中值粒径Dv50在3μm至10μm的范围内,置入造粒设备中进行造粒,期间不停搅拌并加热至500℃至1000℃,然后进行石墨化工艺(其中石墨化温度控制在2000℃至3500℃),得到对比例1中使用的石墨负极活性材料。
将上述制备的石墨负极活性材料、丁苯橡胶(SBR)和羧甲基纤维素钠(CMC)按照重量比97.7:1.2:1.1分散于去离子水中,充分搅拌混合均匀,得到负极浆料。将负极浆料涂覆在负极集流体上,烘干,冷压形成负极活性材料层,再经过裁片、焊接极耳,得到负极。
不同粒径的石墨颗粒可采用任何已知技术对原料进行破碎分级得到。
2、正极的制备
将钴酸锂(LiCoO 2)、乙炔黑、聚偏二氟乙烯(PVDF)按重量比96:2:2在适量的N-甲基吡咯烷酮(NMP)中充分搅拌混合均匀后,涂覆于正极集流体铝箔上,烘干,冷压形成正极活性材料层,再经过裁片、焊接极耳,得到正极。
3、电解液的制备
在干燥氩气环境下,将碳酸乙烯酯(EC)、碳酸丙烯酯(PC)和碳酸二乙酯(DEC)以1:1:1的重量比混合,加入LiPF 6混合均匀。加入3%的氟代碳酸乙烯酯,混合均匀后得到电解液,其中LiPF 6的浓度为1.15mol/L。
4、隔离膜的制备
以12μm厚的聚乙烯(PE)多孔聚合物薄膜作为隔离膜。
5、锂离子电池的制备
将正极、隔离膜、负极按顺序叠好,使隔离膜处于正极和负极之间起到隔离的作用,然后卷绕电池、焊接极耳、置于外包装箔铝塑膜中,注入上述制备好的电解液,经过真空封装、静置、化成、整形、容量测试等工序,获得锂离子电池。
二、测试方法
1、负极活性材料的粒径的测试方法
使用马尔文粒度测试仪测量负极活性材料的粒径:将负极活性材料样品分散在分散剂乙醇中,超声30分钟后,将样品加入到马尔文粒度测试仪内,测试负极活性材料的Dv50、Dv10和Dv90。
2、负极活性材料的比表面积的测试方法
使用比表面积分析仪(TristarⅡ3020M),通过氮吸附/脱附法测量负极活性材料的比表面积:将负极活性材料样品在真空干燥箱中烘干,然后装入样品管中在分析仪中测量。
3、锂离子电池的克容量的测试方法
将锂离子电池以0.05C放电至5.0mV,以50μA放电至5.0mV,以10μA放电至5.0mV,以0.1C充电至2.0V,记录此时锂离子电池的容量,记为克容量。0.05C指的是0.05倍设计克容量下的电流值,0.1C指的是0.1倍设计克容量下的电流值。
4、锂离子电池的循环厚度膨胀率的测试方法
在45℃下,用万分尺测试锂离子电池在初始半充电状态下的厚度,记为H 0。将锂离子电池以1.5C倍率充放电循环500圈,期间每循环50圈后,测量锂离子电池在满充状态下的厚度,记为H n。通过下式计算锂离子电池的循环厚度膨胀率:
对应循环圈数的循环厚度膨胀率=(H n-H 0)/H 0×100%。
5、锂离子电池的首次效率的测试方法
将锂离子电池以0.5C充电至4.45V,记录首次充电容量C,然后以0.5C放电至3.0V,记录其放电容量D。通过下式计算锂离子电池的首次效率CE:
CE=D/C。
三、测试结果
表1展示了制备负极活性材料过程中负极活性材料的特性对锂离子电池的克容量和循环厚度膨胀率的影响。
表1
Figure PCTCN2021076186-appb-000001
如对比例1所示,在制备负极活性材料时没有添加高粘性粘结剂,负极活性材料为一次颗粒,没有复合形成二次颗粒,所得到的锂离子电池虽具有较高的克容量,但负极活性材料的各向异性较大,导锂离子电池的循环厚度膨胀率较高,总体性能较差。
如实施例1-20所示,在制备负极活性材料时添加适当量的高粘性粘结剂使得负极活性材料的D 2v50/D 1v50不小于0.8,锂离子电池既具有较高的克容量,同时还具有较低的循环厚度膨胀率,实现了高克容量和低循环厚度膨胀率的平衡。
在高粘性粘结剂的含量的一定的情况下,当负极活性材料的中值粒径D 1v50在10μm至25μm的范围内逐渐增大时,负极活性材料在1t压力下的中值粒径D 2v50与D 1v50 的比值D 2v50/D 1v50降低,负极活性材料的(BET 2-BET 1)/BET 1增大,碳元素与氧元素的重量比增大,使得锂离子电池的克容量增加,循环厚度膨胀率降低。当负极活性材料的比表面积满足BET 1在0.6m 2/g至2.0m 2/g的范围内且(BET 2-BET 1)/BET 1≤1和/或负极活性材料层中碳元素与氧元素的含量比在2:3至990:1的范围内时,可实现高克容量和低循环厚度膨胀率的进一步平衡。
表2展示了负极活性材料的D 1v90/D 1v10和C004/C110对锂离子电池的首次效率和循环厚度膨胀率的影响。除表2中所列参数以外,实施例21-39与实施例8的条件一致。
表2
Figure PCTCN2021076186-appb-000002
结果表明,当负极活性材料的D 1v90/D 1v10小于3.5时,锂离子电池的首次效率显著升高。当负极活性材料的D 1v90/D 1v10在小于3.5的范围内逐渐减小时,锂离子电池的首次效率变化不大,循环厚度膨胀率逐渐降低。当负极活性材料层的C004/C110在5.7至18的范围内逐渐减小时,石墨颗粒的晶粒尺寸La减小,Lc增大,孔隙率增大,锂离子电池的循环厚度膨胀率逐渐下降,首次效率略有下降。总体上,当负极活性材料 满足D 1v90/D 1v10小于3.5、C004/C110在5.7至18的范围内、La为160nm至165nm、Lc为30nm至32nm和/或孔隙率为20%至30%时,锂离子电池具有平衡的首次效率和循环厚度膨胀率。
表3展示了锂离子电池在满放状态下负极活性材料的特性对锂离子电池的首次效率和循环厚度膨胀率的影响。
表3
Figure PCTCN2021076186-appb-000003
结果表明,在锂离子电池的满放状态下,负极活性材料的D bv50/D av50和负极活性材料的(BET b-BET a)/BET a会影响锂离子电池的首次效率的提升,同时会影响锂离子电池的循环厚度膨胀率。
图1展示了实施例8和对比例1的锂离子电池随循环圈数的循环厚度膨胀率。结果表明,相比于对比例1,实施例8的锂离子电池具有显著更低的循环厚度膨胀率。随着循环圈数的增加,两者的循环厚度膨胀率的差异越大。
整个说明书中对“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 (10)

  1. 一种负极活性材料,其中所述负极活性材料具有中值粒径D 1v50,所述负极活性材料在1t压力下具有中值粒径D 2v50,且D 2v50/D 1v50为不小于0.8。
  2. 根据权利要求1所述的负极活性材料,其中所述负极活性材料具有比表面积BET 1,所述BET 1为0.6m 2/g至2.0m 2/g,所述负极活性材料在1t压力下具有比表面积BET 2,且(BET 2-BET 1)/BET 1≤1。
  3. 根据权利要求1所述的负极活性材料,其中所述负极活性材料包括石墨颗粒,所述石墨颗粒满足条件(a)至(c)中的至少一者:
    (a)D 1v50为10μm至25μm;
    (b)D 1v90与D 1v10满足D 1v90/D 1v10小于3.5;
    (c)通过X射线衍射法,所述石墨颗粒沿水平方向的晶粒尺寸La为160nm至165nm,所述石墨颗粒沿垂直方向的晶粒尺寸Lc为30nm至32nm。
  4. 一种电化学装置,其包含负极,所述负极包括负极集流体和负极活性材料层,所述负极活性材料层包括权利要求1-3中任一权利要求所述的负极活性材料。
  5. 根据权利要求4所述的电化学装置,其中所述负极活性材料层满足条件(d)至(f)中的至少一者:
    (d)所述负极活性材料层包含碳元素和氧元素,所述碳元素的含量与所述氧元素的含量的重量比为2:3至990:1;
    (e)由X射线衍射图谱测定得到的所述负极活性材料层的(004)面的峰面积C004和(110)面的峰面积C110的比值C004/C110为5.7至18;
    (f)所述负极活性材料层的孔隙率为20%至30%。
  6. 根据权利要求4所述的电化学装置,其中所述电化学装置在满放状态下,由X射线衍射图谱测定得到的所述负极活性材料层的(004)面的峰面积C004'和 (110)面的峰面积C110'的比值C004'/C110'为6.8至17.2。
  7. 根据权利要求4所述的电化学装置,其中所述电化学装置在满放状态下,所述负极活性材料具有中值粒径D av50,所述负极活性材料在1t压力下具有中值粒径D bv50,且D bv50/D av50为不小于0.9。
  8. 根据权利要求4所述的电化学装置,其中所述电化学装置在满放状态下,所述负极活性材料的中值粒径D av50为8μm至20μm。
  9. 根据权利要求4所述的电化学装置,其中所述电化学装置在满放状态下,所述负极活性材料具有比表面积BET a,所述负极活性材料在1 t压力下具有比表面积BET b,且(BET b-BET a)/BET a<0.6。
  10. 一种电子装置,其包括根据权利要求4-9中任一权利要求所述的电化学装置。
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