WO2022268046A1 - 负极活性材料、二次电池和电子装置 - Google Patents

负极活性材料、二次电池和电子装置 Download PDF

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Publication number
WO2022268046A1
WO2022268046A1 PCT/CN2022/100001 CN2022100001W WO2022268046A1 WO 2022268046 A1 WO2022268046 A1 WO 2022268046A1 CN 2022100001 W CN2022100001 W CN 2022100001W WO 2022268046 A1 WO2022268046 A1 WO 2022268046A1
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negative electrode
active material
electrode active
satisfies
lithium
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PCT/CN2022/100001
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English (en)
French (fr)
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唐佳
何丽红
谢远森
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宁德新能源科技有限公司
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Priority to EP22827539.2A priority Critical patent/EP4310955A1/en
Publication of WO2022268046A1 publication Critical patent/WO2022268046A1/zh
Priority to US18/193,996 priority patent/US20230261189A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—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
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • 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 application relates to the technical field of energy storage, in particular to a negative electrode active material, a secondary battery and an electronic device.
  • lithium-ion battery industry has entered a period of rapid growth, and the industrial scale has grown rapidly.
  • lithium-ion batteries are widely used in notebook computers, mobile phones, and new energy electric vehicles. high demands. Ensuring safety performance can enhance product competitiveness. Improving energy density performance can improve battery life and improve user experience comfort.
  • the present application attempts to solve at least one problem existing in the related art to at least some extent by providing a negative electrode active material and a secondary battery and an electronic device using the same.
  • the present application provides a negative electrode active material, wherein the negative electrode active material particles satisfy the following relationship: 0.1 ⁇ AR 10 ⁇ 0.2, 0.2 ⁇ AR 50 ⁇ 0.4, wherein the particle volume cumulative distribution is 10
  • the width-to-length ratio of the negative electrode active material is AR 10
  • the width-to-length ratio of the negative electrode active material is AR 50 when the cumulative particle volume distribution is 50%.
  • the negative electrode active material satisfies 0.4 ⁇ AR 90 ⁇ 0.8, where AR 90 represents the width-to-length ratio of the negative electrode active material when the particle volume cumulative distribution is 90% in particle size distribution.
  • AR 90 represents the width-to-length ratio of the negative electrode active material when the particle volume cumulative distribution is 90% in particle size distribution.
  • the elongated particles in the negative electrode active material within the above range have a higher proportion, which can accelerate the rapid deintercalation of lithium ions and improve the rate performance of the secondary battery.
  • the negative electrode active material satisfies at least one of the conditions (a) to (d): (a) the negative electrode active material satisfies 1.5 ⁇ Dv99/Dv50 ⁇ 4.5; (b) the The gram capacity of the negative active material is ⁇ 355mAh/g; (c) the ratio of the diffraction peak area C004 of the 004 crystal plane of the negative active material to the diffraction peak area C110 of the 110 crystal plane satisfies 10 ⁇ C004/C110 ⁇ 40; (d) The compacted density of the negative electrode active material is ⁇ 1.90g/cm 3 .
  • the negative electrode active material satisfies 1.5 ⁇ Dv99/Dv50 ⁇ 4.5.
  • the prepared negative electrode since the long diameter of the particles is arranged perpendicular to the current collector, when the particle size of the negative electrode active material is too large, the prepared negative electrode is easy to produce bumps on the surface of the negative electrode active material layer after a certain pressure treatment. On the one hand, the bumps will affect The appearance of the negative electrode sheet, on the other hand, is easy to precipitate lithium, which affects the cycle performance of the battery, and the particles are too large to be conducive to the insertion and extraction of lithium ions.
  • the ratio of the diffraction peak area C004 of the 004 crystal plane to the diffraction peak area C110 of the 110 crystal plane of the negative active material satisfies 10 ⁇ C004/C110 ⁇ 40.
  • the C004/C110 of the negative electrode active material is within the above range, which is more conducive to the intercalation and extraction of lithium ions.
  • the compacted density of the negative electrode active material is ⁇ 1.90 g/cm 3 .
  • the compaction density of the negative electrode active material is related to the pressure that the negative electrode material can withstand after being prepared into the negative electrode. Materials with high compaction density are conducive to the preparation of batteries with high volumetric energy density.
  • the negative electrode active material includes artificial graphite.
  • the artificial graphite includes at least one of needle coke artificial graphite, petroleum coke artificial graphite or pitch artificial graphite.
  • the present application provides a secondary battery, which includes a positive electrode, a separator, an electrolyte, and a negative electrode, the negative electrode includes a negative electrode current collector and a negative electrode active material layer, and the negative electrode active material layer includes a first The negative electrode active material described in the aspect.
  • the negative electrode includes negative electrode active material particles whose angle ⁇ between the long axis direction and the negative electrode current collector satisfies 45° ⁇ 90°.
  • the negative electrode active material particles are arranged on the current collector at a certain angle between the long diameter and the current collector, and the angle of arrangement is ⁇ 45°, so that in the process of lithium intercalation In this way, the path of lithium ions intercalating into the negative electrode active material layer is greatly shortened, which can effectively increase the lithium intercalation speed of lithium ions.
  • the negative electrode includes negative electrode active material particles whose angle ⁇ between the major axis direction and the current collector satisfies 55° ⁇ 85°. According to some embodiments of the present application, in the negative electrode active material layer, the angle ⁇ between the long axis direction of the negative electrode active material and the negative electrode current collector satisfies 45° ⁇ 90°.
  • the angle ⁇ between the long axis direction of the negative electrode active material and the negative electrode current collector satisfies 55° ⁇ 85°.
  • the negative electrode satisfies at least one of the conditions (e) to (f): (e) The ratio of the diffraction peak area C004 of the 004 crystal plane of the negative electrode to the diffraction peak area C004 of the 110 crystal plane satisfies C004 /C110 ⁇ 15; (f) The electrolyte soaking time of the negative electrode ⁇ 2min.
  • the C004/C110 of the negative electrode within the above range is more conducive to the intercalation and extraction of lithium ions.
  • the present application provides an electronic device, which includes the secondary battery described in the second aspect.
  • the negative electrode active material when the aspect ratio distribution of the negative electrode active material satisfies 0.1 ⁇ AR10 ⁇ 0.2 and 0.2 ⁇ AR50 ⁇ 0.4, most of the particles of the negative electrode active material are elongated. At this time, the negative electrode active material has a higher gram capacity, which can Accelerate the rapid deintercalation of lithium ions, and can release the stress on the negative active material particles in all directions evenly during the process of intercalation and extraction of lithium ions. While obtaining high energy density, it can control the expansion of the negative electrode sheet and improve the performance of lithium ions. Fast charge and discharge performance of the battery.
  • FIG. 1 is a schematic diagram of the arrangement of negative electrode active materials on a current collector according to an embodiment of the present application.
  • FIG. 2 is a schematic diagram of the lithium ion intercalation graphite layer of the negative electrode according to the embodiment of the present application.
  • a list of items to which the terms "at least one of”, “at least one of”, “at least one of” or other similar terms are concatenated can mean any combination of the listed items. For example, if the items A and B are listed, the phrase “at least one of A or B” means A only; only B; or A and B. In another example, if the items A, B, and C are listed, the phrase "at least one of A, B, or C” means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C.
  • Item A may comprise a single component or multiple components.
  • Item B may comprise a single component or multiple components.
  • Item C may comprise a single component or multiple components.
  • this application selects easily graphitizable precursors to increase the gram capacity of the negative electrode active material to meet the energy density requirements
  • the morphology of the negative electrode active material particles is controlled to be slender, equipped with magnetization technology, so that the particles are arranged in a certain direction on the current collector, and the expansion of the negative electrode sheet can be controlled while obtaining high energy density.
  • the present application provides a negative electrode active material, the negative electrode active material satisfies the following relationship: 0.1 ⁇ AR 10 ⁇ 0.2, 0.2 ⁇ AR 50 ⁇ 0.4, wherein the width-to-length ratio of the negative electrode active material when the particle volume cumulative distribution is 10% AR 10 , the width-to-length ratio of the negative electrode active material when the particle volume cumulative distribution is 50% is AR 50 .
  • the "aspect ratio" of the negative active material refers to the ratio of the wide diameter to the long diameter of the negative active material particles.
  • the aspect ratio of the negative active material can be obtained by dynamic particle image analysis (for example, using a Sipatec QICPIC dynamic particle image analyzer).
  • the "broad diameter” of the negative electrode active material particle refers to the minimum value between parallel lines tangent to the projected image of the particle.
  • the “major axis” of the negative active material particle refers to the maximum value between parallel lines tangent to the projected image of the particle.
  • AR n refers to the width-to-length ratio of the particles of the negative electrode active material corresponding to when the particle volume cumulative distribution of the negative electrode active material is n%.
  • AR 10 indicates the width-to-length ratio of the particles of the negative electrode active material when the particle volume cumulative distribution of the negative electrode active material is 10%.
  • AR 50 indicates the width-to-length ratio of the particles of the negative electrode active material when the particle volume cumulative distribution of the negative electrode active material is 50%.
  • AR 90 indicates the width-to-length ratio of the particles of the negative electrode active material when the particle volume cumulative distribution of the negative electrode active material is 90%.
  • the negative electrode active material includes primary particles.
  • AR 10 may be 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19 and any value therebetween.
  • AR 50 may be 0.22, 0.24, 0.26, 0.28, 0.30, 0.31, 0.33, 0.35, 0.39 and any value therebetween.
  • the negative electrode active material satisfies 0.4 ⁇ AR 90 ⁇ 0.8, where AR 90 represents the width-to-length ratio of the negative electrode active material when the particle volume cumulative distribution is 90% in particle size distribution.
  • AR 90 may be 0.45, 0.48, 0.53, 0.55, 0.57, 0.60, 0.63, 0.65, 0.70, 0.75 and any value therebetween. Within this range, the proportion of elongated particles in the negative electrode active material is relatively high, which can accelerate the rapid deintercalation of lithium ions and improve the rate performance of the secondary battery.
  • the negative electrode active material satisfies 1.3 ⁇ AR 90 /AR 50 ⁇ 3.5.
  • AR 90 /AR 50 may be 1.4, 1.5, 1.7, 1.9, 2.0, 2.3, 2.5, 2.7, 2.9, 3.0, 3.2, 3.5 and any value therebetween. Controlling the distribution of the width-to-length ratio of the negative electrode active material particles within this range can further increase the deintercalation speed of lithium ions, improve the rate performance of the secondary battery, and improve the deformation of the negative electrode.
  • the negative electrode active material satisfies: 1.5 ⁇ AR 90 /AR 50 ⁇ 3, which can further increase the deintercalation speed of lithium ions, improve the deformation of the negative electrode and improve the rate performance of the secondary battery.
  • the aspect ratio distribution of the negative electrode active material of the present application satisfies 0.1 ⁇ AR 10 ⁇ 0.2, 0.2 ⁇ AR 50 ⁇ 0.4, 0.4 ⁇ AR 90 ⁇ 0.8, most of the prepared negative electrode active material particles are elongated, within this range
  • the gram capacity of the inner negative electrode active material is high.
  • the transmission path in the lithium ion transmission process can be reduced, the rapid deintercalation of lithium ions can be accelerated, and the negative electrode active material particles can The stress received during the insertion and extraction of lithium ions is evenly released in all directions to achieve the effect of improving deformation.
  • the negative electrode active material satisfies 1.5 ⁇ Dv99/Dv50 ⁇ 4.5.
  • Dv99/Dv50 can be 1.8, 2.0, 2.2, 2.5, 2.7, 3.0, 3.3, 3.5, 3.8, 4.0, 4.3 and any value between them.
  • the prepared negative electrode is easy to produce bumps on the surface of the negative electrode active material layer after a certain pressure treatment, and the bumps will affect the negative electrode on the one hand.
  • too large particles are not conducive to the intercalation and extraction of lithium ions. Therefore, it is necessary to control the particle size of the negative electrode active material within the above-mentioned range.
  • the negative electrode active material satisfies: 2 ⁇ Dv99/Dv50 ⁇ 4, which can further improve the intercalation and extraction of lithium ions and improve the cycle performance of the battery.
  • the gram capacity of the negative electrode active material is ⁇ 355mAh/g. In some embodiments of the present application, the gram capacity of the negative electrode active material is 355mAh/g to 370mAh/g. In some embodiments of the present application, the gram capacity of the negative electrode active material may be 358mAh/g, 360mAh/g, 362mAh/g, 365mAh/g, 368mAh/g, 370mAh/g and any value therebetween.
  • the ratio of the 004 crystal plane diffraction peak area C004 to the 110 crystal plane diffraction peak area C110 of the negative active material measured by X-ray diffraction method satisfies 10 ⁇ C004/C110 ⁇ 40, for example C004/C110 Can be 12, 15, 17, 20, 23, 25, 28, 30, 33, 35, 37, 39 and any value in between.
  • the C004/C110 of the negative electrode active material is within the above range, which is more conducive to the intercalation and extraction of lithium ions.
  • the ratio of the diffraction peak area C004 of the 004 crystal plane of the negative active material to the diffraction peak area C110 of the 110 crystal plane satisfies 10 ⁇ C004/C110 ⁇ 30, which further accelerates the insertion and extraction of lithium ions and reduces the The expansion of the battery and improve the cycle performance of the battery.
  • the compacted density of the negative electrode active material is ⁇ 1.90 g/cm 3 .
  • the compacted density of the negative active material is powder compacted density.
  • the compacted density of the negative electrode active material under the test pressure of 5t is ⁇ 1.90g/cm 3
  • the compacted density of the negative electrode active material is related to the pressure that the negative electrode material can withstand after being prepared into a negative electrode. High Materials with a compacted density are beneficial for the preparation of batteries with high volumetric energy density.
  • the negative electrode active material includes artificial graphite.
  • the artificial graphite includes at least one of needle coke artificial graphite, petroleum coke artificial graphite, or pitch artificial graphite.
  • at least a portion of the surface of the negative active material contains an amorphous carbon layer.
  • the raw material of the artificial graphite includes at least one of needle coke, petroleum coke, and pitch, and the raw material is pulverized to a certain particle size and then subjected to a graphitization treatment at a temperature greater than or equal to 2800°C to obtain the artificial graphite. .
  • the present application provides a negative electrode, which includes a negative electrode current collector and a negative electrode active material layer, and the negative electrode active material layer contains the negative electrode active material described in the first aspect.
  • the negative electrode includes negative electrode active material particles whose angle ⁇ between the long axis direction and the negative electrode current collector satisfies 45° ⁇ 90°.
  • the negative electrode active material includes particles whose angle ⁇ between the major diameter direction and the negative electrode current collector satisfies 50° ⁇ 90°.
  • the included angle ⁇ is 45°, 50°, 55°, 60°, 65°, 70°, 80°, 85°, 90° and any value therebetween.
  • the included angle ⁇ in this application is the acute angle or right angle among the included angles between the long diameter direction of the particles and the negative electrode current collector, as shown in Figure 1, the included angle distribution can be measured by a polarizing microscope.
  • the negative electrode includes negative electrode active material particles whose angle ⁇ between the long axis direction and the negative electrode current collector satisfies 50° ⁇ 85°. In some embodiments of the present application, the negative electrode includes negative electrode active material particles whose angle ⁇ between the major axis direction and the negative electrode current collector satisfies 55° ⁇ 85°.
  • the angle ⁇ between the long axis direction of the negative electrode active material particles and the negative electrode current collector satisfies 45° ⁇ 90°.
  • the angle ⁇ between the long axis direction of the negative electrode active material particles and the negative electrode current collector of at least 50% of the negative electrode satisfies 45° ⁇ 90°, such as at least 60%, at least 70%, at least 80° % or at least 90% of the angle ⁇ between the long axis direction of the negative electrode active material particles and the negative electrode current collector satisfies 45° ⁇ 90°.
  • the angle ⁇ between the long axis direction of the negative electrode active material particles and the negative electrode current collector satisfies 50° ⁇ 85°. According to some embodiments of the present application, in the negative electrode, the angle ⁇ between the long axis direction of the negative electrode active material and the negative electrode current collector satisfies 55° ⁇ 85°. According to some embodiments of the present application, in the negative electrode, the angle ⁇ between the major axis direction of the negative electrode active material and the negative electrode current collector satisfies 65° ⁇ 90°. In some implementations, in the negative electrode, the angle ⁇ between the major axis direction of the negative electrode active material particles and the current collector is 90°, that is, the major axis direction of the negative electrode active material is perpendicular to the current collector.
  • Negative electrode active material particles are stacked layer by layer on the surface of the current collector with a certain porosity between the particles according to different orientations to form a negative electrode active material layer.
  • the long side of the elongated particles tends to be parallel to the current collector, and the short side tends to be perpendicular to the direction of the current collector. Such a distribution makes it difficult for lithium ions to intercalate through the gaps between particles.
  • the particles of the negative electrode active material are arranged on the current collector at a certain angle between the long diameter and the current collector, and the angle of arrangement is ⁇ 45°.
  • the path of lithium ions intercalated into the graphite layer is greatly shortened, which can effectively increase the lithium intercalation speed of lithium ions.
  • the angle between the long axis and the current collector is ⁇ 45°, as shown in Figure 2 during lithium intercalation, lithium ions are embedded in the negative electrode active material layer from the short axis direction, so it is perpendicular to The expansion in the negative direction is greatly reduced.
  • the ratio of the diffraction peak area C004 of the 004 crystal plane of the negative electrode to the diffraction peak area C110 of the 110 crystal plane measured by X-ray diffraction method satisfies C004/C110 ⁇ 15, for example, C004/C110 can be 5, 7, 8, 9, 10, 11, 12, 13, 14, 15 and any value in between.
  • the ratio of the diffraction peak area C004 of the 004 crystal plane to the diffraction peak area C004 of the 110 crystal plane of the negative electrode satisfies C004/C110 ⁇ 13.
  • the C004/C110 of the negative electrode within the above range is more conducive to the intercalation and extraction of lithium ions.
  • the C004/C110 of the negative electrode is smaller than the C004/C110 of the negative electrode active material.
  • a special method is used to make the long-diameter particles form an angle of 45° to 90° with the direction parallel to the current collector, so that the ratio of C004/C110 of the negative electrode becomes smaller, which is more conducive to the deintercalation of lithium ions.
  • the wettability of the electrolyte in the negative electrode is good, satisfying the wettability time ⁇ 2min.
  • the negative electrode includes a negative electrode current collector and a negative electrode active material layer, wherein the negative electrode active material layer is disposed on at least one surface of the negative electrode current collector, and the negative electrode active material layer includes any of the foregoing A negative electrode active material.
  • the negative electrode active material layer further includes a binder
  • the binder includes polyvinylidene fluoride, a copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate , polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinyl pyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene, styrene-butadiene rubber, acrylate and One or more of epoxy resins.
  • the negative electrode further includes a conductive coating between the negative active material layer and the current collector, the conductive coating includes carbon fiber, Ketjen black, acetylene black, carbon nanotubes and graphite One or more of conductive agents such as alkene.
  • the current collector of the negative electrode may include at least one of copper foil, aluminum foil, nickel foil, or a carbon-based current collector.
  • the preparation method of the negative electrode of the present application includes coating the slurry containing the negative electrode active material on the current collector in the presence of a magnetic field.
  • the method includes coating the slurry containing the negative electrode active material on the current collector under the condition of the presence of a magnetic field, so that the long axis direction of the negative electrode active material is aligned with the direction of the negative electrode current collector.
  • the included angle ⁇ satisfies 45° ⁇ 85°.
  • the magnetic induction of the magnetic field is 3000Gs to 7200Gs.
  • a certain amount of magnetic induction is applied when the negative electrode slurry is coated on the current collector, for example, the intensity is 3000Gs to 7200Gs, and the negative active material particles after the magnetic induction treatment can be They are arranged on the current collector in such a way that the short diameter is parallel to the current collector and the long diameter is perpendicular to the current collector.
  • This treatment can effectively arrange the lithium intercalation end faces of negative active materials such as graphite in a direction parallel to the current collector, thereby increasing the lithium intercalation speed of lithium ions.
  • the secondary battery pack of the present application includes 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 secondary battery of the present application includes a positive electrode, the negative electrode described in the second aspect, a separator, and an electrolyte.
  • the secondary battery is disassembled under 50% SOC state to obtain the negative electrode sheet, and the thickness of the negative electrode sheet is measured using a micrometer.
  • the average value of 14 points is tested, and the Compared with the negative electrode sheet in the uncharged state, the increase rate of the thickness of the negative electrode sheet is ⁇ 15%.
  • the battery thickness increase is ⁇ 5%, and the battery thickness is measured with a micrometer.
  • the ratio retention rate of the capacity obtained by charging at 5C to the capacity obtained by charging at 0.5C under the condition of 25°C of the secondary battery is ⁇ 90%.
  • the negative electrode in the secondary battery of the present application includes the negative electrode described in the second aspect.
  • Materials, constitutions, and manufacturing methods of the positive electrode that can be used in the embodiments of the present application include any technology disclosed in the prior art.
  • the positive electrode includes a current collector and a positive electrode active material layer on the current collector.
  • the positive electrode active material includes, but is not limited to: lithium cobalt oxide (LiCoO 2 ), lithium nickel cobalt manganese (NCM) ternary material, lithium ferrous phosphate (LiFePO 4 ) or lithium manganese oxide (LiMn 2 O 4 ).
  • the positive active material layer further includes a binder, and optionally includes a 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.
  • the binder includes: polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers , polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylic (ester) styrene-butadiene rubber, epoxy resin or nylon, etc.
  • conductive materials include, but are not limited to: carbon-based materials, metal-based materials, conductive polymers, and mixtures thereof.
  • the carbon-based material is selected from natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or any combination thereof.
  • the metal-based material is selected from metal powder, metal fiber, copper, nickel, aluminum or silver.
  • the conductive polymer is a polyphenylene derivative.
  • the current collector may include, but not limited to: aluminum foil.
  • the electrolyte that can be used in the embodiments of the present application can be the electrolyte known in the prior art.
  • the electrolyte includes an organic solvent, a lithium salt, and additives.
  • the organic solvent of the electrolytic solution according to the present application can be any organic solvent known in the prior art that can be used as a solvent for the electrolytic solution.
  • the electrolyte used in the electrolytic solution according to the present application is not limited, and it may be any electrolyte known in the prior art.
  • the additive of the electrolytic solution according to the present application may be any additive known in the prior art as an additive to the electrolytic solution.
  • the organic solvents include, but are not limited to: ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propyl propionate, or ethyl propionate.
  • EC ethylene carbonate
  • PC propylene carbonate
  • DEC diethyl carbonate
  • EMC ethyl methyl carbonate
  • DMC dimethyl carbonate
  • propyl propionate or ethyl propionate.
  • the lithium salts include, but are not limited to: lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium difluorophosphate (LiPO 2 F 2 ), bistrifluoromethanesulfonylimide Lithium LiN(CF 3 SO 2 ) 2 (LiTFSI), lithium bis(fluorosulfonyl)imide Li(N(SO 2 F) 2 )(LiFSI), lithium bisoxalate borate LiB(C 2 O 4 ) 2 (LiBOB ) or lithium difluorooxalate borate LiBF 2 (C 2 O 4 ) (LiDFOB).
  • LiPF 6 lithium hexafluorophosphate
  • LiBF 4 lithium tetrafluoroborate
  • LiPO 2 F 2 lithium difluorophosphate
  • LiTFSI bistrifluoromethanesulfonylimide Lithium LiN(CF 3 SO 2 )
  • the lithium salt concentration in the electrolyte is: 0.5 mol/L to 3 mol/L, 0.5 mol/L to 2 mol/L, or 0.8 mol/L to 1.5 mol/L.
  • the additives include, but are not limited to: vinylene carbonate (VC), ethylene carbonate (VEC), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC) , 1,3-propane sultone (PS), vinyl sulfate (DTD), 1,3-dioxane, maleic anhydride, adiponitrile, succinonitrile, 1,3,5-pentanetri Nitrile, 1,3,6-Hexanetrinitrile.
  • VC vinylene carbonate
  • VEC ethylene carbonate
  • FEC fluoroethylene carbonate
  • DFEC difluoroethylene carbonate
  • PS 1,3-propane sultone
  • DTD vinyl sulfate
  • 1,3-dioxane maleic anhydride
  • adiponitrile succinonitrile
  • succinonitrile 1,3,5-pentanetri Nitrile
  • 1,3,6-Hexanetrinitrile 1,3,
  • the material and shape of the separator used in the secondary battery of the present application are not particularly limited, and it may be any technology disclosed in the prior art.
  • the separator includes a polymer or an inorganic material formed of a material stable to the electrolyte of the present application.
  • a release film may include a substrate layer and a surface treatment layer.
  • the substrate layer is non-woven fabric, film or composite film with a porous structure, and the material of the substrate layer is at least one selected from polyethylene, polypropylene, polyethylene terephthalate and polyimide.
  • polypropylene porous film, polyethylene porous film, polypropylene non-woven fabric, polyethylene non-woven fabric or polypropylene-polyethylene-polypropylene porous composite film can be selected.
  • At least one surface of the substrate layer is provided with a surface treatment layer, and the surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing polymers and inorganic materials.
  • the inorganic layer includes inorganic particles and a binder, and the inorganic particles are selected from aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium oxide, tin oxide, cerium oxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, At least one of yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide and barium sulfate.
  • the binder is selected from polyvinylidene fluoride, copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinyl pyrrolidone, polyvinyl alkoxy , polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene at least one.
  • Polymer is contained in the polymer layer, and the material of polymer is selected from polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinyl pyrrolidone, polyvinyl alkoxide, polyvinylidene fluoride, At least one of poly(vinylidene fluoride-hexafluoropropylene).
  • the present application further provides an electronic device, which includes the secondary battery described in the third aspect of the present application.
  • electronic devices of the present application include, but are not limited to, notebook computers, pen-input computers, mobile computers, e-book players, cellular phones, portable fax machines, portable copiers, portable printers, headsets , VCR, LCD TV, Portable Cleaner, Portable CD Player, Mini Disc, Transceiver, Electronic Notepad, Calculator, Memory Card, Portable Recorder, Radio, Backup Power, Motor, Automobile, Motorcycle, Assisted Bicycle, Bicycle , Lighting appliances, toys, game consoles, clocks, electric tools, flashlights, cameras, large household batteries and lithium-ion capacitors, etc.
  • the negative electrode active material graphite, styrene-butadiene rubber (abbreviated as SBR) and sodium carboxymethyl cellulose (abbreviated as CMC) are fully stirred and mixed in deionized water solvent according to the weight ratio of 95:2:3 to form a uniform negative electrode Slurry; this slurry is coated on the current collector copper foil that is pre-coated with undercoat (such as carbon black), the thickness of undercoat is 1.5 ⁇ m to 3 ⁇ m, and the coating weight of negative electrode slurry is Xmg/ mm 2 (coating weight 0.032 mg/mm 2 to 0.120 mg/mm 2 , eg 0.032 mg/mm 2 , 0.055 mg/mm 2 , 0.070 mg/mm 2 , 0.090 mg/mm 2 , 0.120 mg/mm 2 ) , the double-sided coating thickness of the negative electrode slurry is Y ⁇ m (the coating thickness is between 70 ⁇ m and 150 ⁇ m, such as 70 ⁇ m, 90
  • the preparation method of graphite is as follows:
  • the graphitization equipment can be any one of the Acheson furnace, the inner series graphitization furnace and the continuous graphitization furnace.
  • the material of the graphitization furnace is crushed to the required particle size (Dv50 is 6 ⁇ m to 10 ⁇ m);
  • the width-to-length ratio of the negative electrode active material graphite is controlled by the following method: during the preparation of the negative electrode active material graphite, the prepared graphite enters the shaping zone through the feeding system for grinding, so that the particle surface has edges and corners, thereby controlling the width and length of the particle ratio and sphericity. Then the ground particles are classified through the self-separation classification zone to obtain the required distribution of particles.
  • Lithium cobaltate (LiCoO 2 ), acetylene black, and polyvinylidene fluoride (PVDF) are fully stirred and mixed in an appropriate amount of N-methylpyrrolidone (NMP) solvent at a weight ratio of 96:2:2 to form a uniform Positive electrode slurry.
  • NMP N-methylpyrrolidone
  • EC ethylene carbonate
  • DEC diethyl carbonate
  • PC propylene carbonate
  • a 7 ⁇ m thick polyethylene (PE) porous polymer film was used as the separator.
  • the positive electrode, separator, and negative electrode in order, so that the separator is between the positive electrode and the negative electrode to play the role of isolation, and then wind up to obtain the bare cell; after welding the tabs, place the bare cell in the outer packaging foil aluminum plastic
  • the above-mentioned prepared electrolyte is injected into the dried bare cells, and after vacuum packaging, standing, formation, shaping, capacity testing and other processes, a soft-packed lithium-ion battery is obtained.
  • the aspect ratio distribution of the negative electrode active material was tested using the new Patek QICPIC dynamic particle image analyzer.
  • the test standard refers to GB/T 24533-2009 "Graphite Anode Materials for Lithium Ion Batteries”.
  • the specific test method is to weigh a sample of 1.0000 ⁇ 0.0500g and place it in the test mold (CARVER#3619 (13mm), and then place the sample in the test equipment.
  • the test equipment is Sansi Zongheng UTM7305, and the test tonnage is 0.3t to 5.0t.
  • the compacted density in the application is the measured compacted density when it is 5t.
  • the polarizing microscope operates as follows:
  • Image acquisition process Axio imager upright microscope (manufactured by Carl Zeiss AG, Imagine A2) was used for image acquisition, AxioCam MRc5 digital camera was connected to polarized light microscope with a connector, and polarized light microscope images were taken with a shutter time of 1.6 seconds. Images captured by the camera are automatically transferred to the computer.
  • Image analysis process an image of 1200 pixels ⁇ 1600 pixels is selected as the analysis object (which corresponds to a field of view of 480 ⁇ m ⁇ 540 ⁇ m).
  • the Multiphase software that comes with AxioVision was used for analysis. After importing the collected photos into the software, click on a point of a certain orientation on the image, and then all areas that are consistent with the gray value and color value of the measurement object are also selected; use the same method to select points of other orientations, Regions with different orientations and different colors can be obtained.
  • AxioVision's automatic calculation software (Axio Vision SE64Rel.4.9)
  • the data of different particle angles in the image and the proportion of different angles are measured, and the long diameter of the negative electrode active material particles is obtained according to the measured results.
  • the particle size test method refers to GB/T 19077-2016.
  • the specific process is to weigh 1g of the sample, mix it with 20mL of deionized water and a small amount of dispersant evenly, place it in an ultrasonic device for 5 minutes, and then pour the solution into the sampling system Hydro 2000SM for testing.
  • the testing equipment used is the Mastersizer produced by Malvern. 3000.
  • Particle size measurement is accomplished by measuring the intensity of scattered light as a laser beam passes through a dispersed particle sample during testing. The data is then used analytically to calculate the particle size distribution forming the scatter spectrum.
  • the refractive index of the particles used in the test is 1.8, one sample is tested three times, and the particle size is finally taken as the average value of the three tests.
  • the test conditions are as follows: CuK ⁇ radiation is used for X-rays, and CuK ⁇ radiation is removed by filters or monochromators.
  • the working voltage of the X-ray tube is 30kV to 35kV, and the working current is 15mA to 20mA.
  • the scanning speed of the counter is 1/4(°)/min.
  • the scanning range of the diffraction angle 2 ⁇ is from 53° to 57°.
  • the scanning range of diffraction angle 2 ⁇ is 75° to 79°.
  • the peak area obtained from the (004) plane diffraction pattern is denoted as C004.
  • the peak area obtained from the (110) plane diffraction pattern was denoted as C110.
  • the ratio of C004/C110 of the negative electrode active material layer was calculated.
  • the C004/C110 test method of the negative electrode active material is the same as the C004/C110 test method of the negative electrode, the only difference is that the negative electrode active material needs to be placed in a glass sheet with grooves and compacted first, and then replace the negative electrode.
  • the negative electrode active material layer samples were prepared as complete discs. Thirty samples were tested for each example or comparative example, each sample having a volume of about 0.35 cm 3 .
  • the porosity of the negative electrode active material layer was tested according to the standard "GB/T24586-2009 Determination of Apparent Density, True Density and Porosity of Iron Ore".
  • the lithium-ion battery was connected to the Bio-Logic VMP3B electrochemical workstation produced by the French Bio-Roger Company for testing, with a frequency range of 30mHz to 50kHz and an amplitude of 5mV. After collecting the data, the impedance complex plane diagram was used to analyze the data, and the lithium ion liquid phase transfer impedance (Rion) was obtained.
  • 5C discharge capacity preservation rate 5C discharge capacity/0.1C discharge capacity ⁇ 100%.
  • the DCR mentioned in this application refers to the direct current resistance of a lithium-ion battery at 10% state of charge (SOC).
  • the disassembled negative electrode is golden yellow as a whole, and gray can be observed in a very small part; and the area of the gray area is less than 2%, it is determined that lithium is not eluting.
  • the disassembled negative electrode appears gray as a whole, and golden yellow can be observed in some positions; and the area of the gray area is between 20% and 60%, it is judged as lithium precipitation.
  • a copper wire was additionally inserted as a reference electrode, and lithium was plated on the negative electrode with a current of 20 ⁇ A for 6 hours to obtain a three-electrode lithium-ion battery.
  • the three-electrode lithium-ion battery was connected to the Bio-Logic VMP3B electrochemical workstation produced by the French Bio-Roger Company for testing, with a frequency range of 30mHz to 50kHz and an amplitude of 5mV.
  • the impedance complex plane diagram is used to analyze the data to obtain the charge transfer impedance (Rct) of the lithium-ion battery.
  • the treated negative electrode was made into a lithium-ion battery according to the preparation steps of the lithium-ion battery, and the lithium-ion battery was charged to 3.95V (ie, 50% SOC) with a constant current of 0.7C after standing still for 5 minutes at 25°C.
  • the lithium ion battery is disassembled under dry conditions to obtain the disassembled negative electrode. Record the negative electrode thickness of at least 14 points, take the average value, and record it as T2. Calculate the expansion rate of the negative electrode along the Z direction by the following formula:
  • Expansion rate in Z direction (T2-T1)/T1 ⁇ 100%.
  • the lithium-ion battery was charged at a constant current of 0.7C to 4.45V after standing still at 45°C for 5 minutes, then charged at a constant voltage of 4.45V to 0.05C, and stood still for 5 minutes.
  • the thickness of the lithium-ion battery at three points is tested by the MMC test method, and the average value is recorded as MMC 0 .
  • the lithium-ion battery was discharged to 3.0V at a constant current of 0.5C, and stood still for 5 minutes. Repeat the above charge and discharge cycle 50 times, recorded as MMC 50 (50 represents the number of cycles).
  • the cyclic expansion rate of the lithium-ion battery at 45 °C was calculated by the following formula:
  • Cycle expansion rate (45°C) (MMC x -MMC 0 )/MMC 0 x 100%.
  • the above-mentioned MMC test method is: use a micrometer tester (manufactured by Mitutoyo, Japan, model: MDC-25SX) to measure the thickness of the lithium-ion battery near the negative electrode tab, measure three different positions for each sample, and take the average value. Recorded as MMC thickness.
  • Table 1 shows the aspect ratio distribution of graphite particles, the magnitude of the magnetic flux applied during the coating process to the gram capacity, the graphite particle powder C004/C110, the negative pole piece C004/C110, the angle between the long diameter direction of the particle and the current collector , the growth rate of the thickness of the negative pole piece in the Z-axis direction and the influence of the DC resistance (DCR) of the lithium-ion battery 1 .
  • the negative electrode active materials used in Example 1 to Example 26 are all the same raw material, the raw material is needle coke, obtained by sintering at 3000°C, the Dv50 of the negative electrode active material particles is 8 ⁇ m, and the Dv99 is 27 ⁇ m.
  • the ⁇ angle is the angle between the long diameter direction of the negative electrode active material particles in the negative electrode and the current collector, and the measured angle value is the average value of all particle angles.
  • Example 1 As shown in Table 1, from Example 1 to Example 26, as the width-to-length ratio of the negative electrode active material particles increases, the gram capacity gradually decreases, and the powder C004/C110 also gradually decreases. And the smaller the width-to-length ratio, the greater the required magnetic flux. This is because the shape of the particles with a small width-to-length ratio is elongated as shown in Figure 1, and for long-striped particles, the particles are on the negative pole during coating. On-chip stacking tends to align parallel to the direction of the current collector. When the long sides of the particles on the negative electrode sheet are parallel to the current collector, lithium ions need to travel through a longer path to intercalate into the graphite layer during the process of deintercalating lithium.
  • the negative electrode sheet C004/C110 is smaller than the powder.
  • Example 1 to Example 6, Example 7 to Example 9, Example 10 to Example 12, Example 13 to Example 18, Example 19 to Example 24 that when the negative electrode active material When the AR 90 size of the particle is fixed, the powder C004/C110 value is affected with the increase of AR 10 or with the increase of AR 50 , because the increase of particle AR 10 or the increase of AR 50 indicates the shape of the particle It tends to be spherical, so the C004/C110 of the powder measured by XRD changes.
  • the change law of C004/C110 of the negative pole piece decreases with the increase of AR 10 and AR 50 , the change rate is much smaller. And the change of expansion affects the change of C004/C110 of the negative electrode sheet.
  • the material with larger AR 10 has a larger angle between the direction of the long diameter of the particle and the direction of the current collector, which indicates that more long diameters and The direction of the current collectors is arranged vertically, which can effectively shorten the transfer path of lithium ions and reduce the expansion of the negative electrode sheet, so the growth rate of the thickness of the negative electrode sheet is significantly reduced.
  • Example 25 Compared with Example 24 and Example 25, the AR 90 of the negative electrode active material particles of Example 25 is too large, and under the same magnetic flux conditions, the angle between the long diameter of the particles of Example 25 and the current collector decreases instead, which is Because when the proportion of spherical particles is too large, the arrangement of particles changes after a certain magnetic flux is applied, but the change is very small.
  • the AR 10 of the negative electrode active material particles is only 0.05, indicating that some of the particles are very elongated, so it is necessary to apply a very large magnetic field to control the ratio of C004/C110 at a certain level. within range.
  • Comparative Example 2 It can be seen from Comparative Example 2 that the AR 10 , AR 50 and AR 90 of the negative electrode active material particles in Comparative Example 2 are relatively large, and the shape of the particles is more round, so the required magnetic flux is very small. But the grammability of the material is also low.
  • This application is aimed at graphite with strong acicularity and high gram capacity. After controlling its width-to-length ratio within a certain range, it can apply the required magnetic flux to adjust its arrangement on the negative electrode sheet to obtain high energy density and control the negative electrode at the same time. Expansion of the pole piece.
  • Table 2 shows the comparison of powder C004/C110, negative pole piece C004/C110 and battery with different widths and lengths and particle size ratios when the coated negative pole piece is treated with a magnetic flux of 5000Gs under different particle size conditions. performance impact.
  • the ⁇ angle is the angle between the particle long diameter direction of the negative electrode plate and the current collector, and the measured angle value is the average value of all the particle angles.
  • the width-to-length ratio of the particles is similar, and the particle size distribution of the particles is different.
  • the larger the particle size distribution the larger the powder C004/C110, so the negative electrode sheet C004/C110 is larger, and the corresponding battery
  • the performance is that the expansion rate along the Z axis is large.
  • the width-to-length ratio of the negative electrode active material particles in Comparative Example 3 is smaller than AR 10.
  • the pole piece C004/C110 is still very large, so the expansion of the battery along the Z-axis is large, and because some particles are too long, It is not conducive to the deintercalation of lithium ions, so it is easy to precipitate lithium under certain rate conditions.
  • Table 3 shows the effect of different width-to-length ratios of particles on battery performance when the coated negative pole piece is treated with a magnetic flux of 5000Gs.
  • the porosity of the prepared negative electrode active material layer increases, so the electrolyte soaking time of the negative pole piece shorten.
  • the width-to-length ratio of the negative electrode active material increases, and the lithium ion transfer resistance (Rion), charge transfer resistance (Rct) and DC resistance (DCR) of the lithium ion battery containing the material decrease, and the discharge capacity at 5C rate remains The higher the rate.
  • the width-to-length ratio of the negative electrode active material is the smallest.

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Abstract

本申请涉及一种负极活性材料、二次电池和电子装置，所述负极活性材料颗粒满足如下关系：0.1≤AR 10＜0.2，0.2≤AR 50＜0.4，其中，颗粒体积累积分布为10％时负极活性材料的宽长比为AR 10，颗粒体积累积分布为50％时负极活性材料的宽长比为AR 50。包含本申请的负极活性材料的锂离子电池能够在保证高能量密度性能(容量，首效，压实密度)的同时满足安全性、循环及循环膨胀的要求。

Description

负极活性材料、二次电池和电子装置
相关申请的交叉引用
本申请基于申请号为202110687403.8、申请日为2021年06月21日，发明名称为“负极活性材料、二次电池和电子装置”的中国专利申请提出，并要求该中国专利申请的优先权，该中国专利申请的全部内容通过引用整体并入本申请。
技术领域
本申请涉及储能技术领域，尤其涉及一种负极活性材料、二次电池和电子装置。
背景技术
锂离子电池产业步入了高速成长期，产业规模增长迅猛。锂离子电池作为一种新型高能绿色电池，被广泛的应用于笔记本电脑、移动电话和新能源电动车等领域广泛应用，这对锂离子电池能量密度、循环寿命、成本以及安全性等提出了更高的要求。保证安全性能，可以提升产品的竞争力。提高能量密度性能，能够提升电池续航时间，进而提高用户体验的舒适度。
随着手机、笔记本等电子设备越来越薄，对电池在循环过程中膨胀要求越来越高。如何通过合理设计一种负极，从而得到兼顾高能量密度性能(容量、首效、压实密度)、循环寿命和安全性能的锂离子二次电池是目前行业内普遍面临的问题。
发明内容
本申请通过提供一种负极活性材料及使用其的二次电池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。
根据本申请的第一方面，本申请提供了一种负极活性材料，其中所述负极活性材料颗粒满足如下关系：0.1≤AR 10＜0.2，0.2≤AR 50＜0.4，其中颗粒体积累积分布为10％时负极活性材料的宽长比为AR 10，颗粒体积累积分布为50％时负极活性材料的宽长比为AR 50。
根据本申请的一些实施方式，所述负极活性材料满足0.4≤AR 90≤0.8，AR 90表示 在颗粒粒型分布中，颗粒体积累积分布为90％时负极活性材料的宽长比。上述范围内的负极活性材料中细长型颗粒占比较高，可加快锂离子的快速脱嵌，提高二次电池的倍率性能。
根据本申请的一些实施方式，1.3＜AR 90/AR 50＜3.5。控制负极活性材料颗粒宽长比分布在此范围内，可进一步提高锂离子的脱嵌速度，提高二次电池的倍率性能，改善负极的形变。
根据本申请的一些实施方式，所述负极活性材料满足条件(a)至(d)中的至少一种：(a)所述负极活性材料满足1.5≤Dv99/Dv50≤4.5；(b)所述负极活性材料的克容量≥355mAh/g；(c)所述负极活性材料的004晶面衍射峰面积C004与110晶面衍射峰面积C110的比值满足10≤C004/C110≤40；(d)所述负极活性材料的压实密度≥1.90g/cm 3。
根据本申请的一些实施方式，所述负极活性材料满足1.5≤Dv99/Dv50≤4.5。本申请中由于颗粒长径垂直于集流体排布，当负极活性材料的颗粒粒度太大时，制备的负极经过一定压力处理后易于在负极活性材料层表面产生凸点，凸点一方面会影响负极极片的外观，另一方面容易析锂，影响电池的循环性能，并且颗粒太大也不利于锂离子的嵌入和脱出。
根据本申请的一些实施方式，所述负极活性材料的004晶面衍射峰面积C004与110晶面衍射峰面积C110的比值满足10≤C004/C110≤40。负极活性材料的C004/C110在上述范围内，更有利于锂离子的嵌入和脱出。
根据本申请的一些实施方式，负极活性材料的压实密度≥1.90g/cm 3。负极活性材料的压实密度与制备成负极后的负极材料可承受的压力相关，高压实密度的材料有利于制备高体积能量密度的电池。
根据本申请的一些实施方式，所述负极活性材料包括人造石墨。
在本申请的一些实施例中，所述人造石墨包含针状焦人造石墨、石油焦人造石墨或沥青人造石墨中的至少一种。
根据本申请的第二方面，本申请提供了二次电池，其包括正极、隔离膜、电解液和负极，所述负极包含负极集流体和负极活性材料层，所述负极活性材料层包含第一方面所述的负极活性材料。
根据本申请的一些实施方式，所述负极包含长径方向与负极集流体的夹角θ满足45°≤θ≤90°的负极活性材料颗粒。根据本申请的一些实施方式，负极中，负极活性材料颗粒如图1所示，长径与集流体呈一定的角度排布在集流体上，排布的角度≥45°，这样在嵌锂过程中使得锂离子嵌入到负极活性材料层中的路径大大缩短，可以有效的提升锂离子的嵌锂速度。同时，在嵌锂的过程中由于长径与集流体所呈的锐角≥45°，因此嵌锂时 如图2所示，锂离子从短径方向嵌入到负极活性材料层中，因此垂直于负极方向的膨胀大大减小。
在本申请的一些实施方式中，所述负极包含长径方向与集流体的夹角θ满足55°≤θ≤85°的负极活性材料颗粒。根据本申请的一些实施方式，所述负极活性材料层中，负极活性材料的长径方向与负极集流体的夹角θ满足45°≤θ≤90°。
根据本申请的一些实施方式，所述负极活性材料层中，负极活性材料的长径方向与负极集流体的夹角θ满足55°≤θ≤85°。
根据本申请的一些实施方式，所述负极满足条件(e)至(f)中的至少一种：(e)负极的004晶面衍射峰面积C004与110晶面衍射峰面积C004的比值满足C004/C110≤15；(f)负极的电解液浸润时间≤2min。负极的C004/C110在上述范围内更有利于锂离子的嵌入和脱出。
根据本申请的第三方面，本申请提供了一种电子装置，其包含第二方面所述的二次电池。
本申请中的负极活性材料的宽长比分布满足0.1≤AR10＜0.2，0.2≤AR50＜0.4时，负极活性材料颗粒大部分为细长型，此时负极活性材料具有较高的克容量，可加快锂离子的快速脱嵌，并且可以使负极活性材料颗粒在锂离子嵌入和脱出的过程中受到的应力朝各个方向均匀释放，在获得高能量密度的同时控制负极极片的膨胀，改善锂离子电池的快速充放电性能。
附图说明
图1为本申请的实施方式的负极活性材料在集流体上的排布示意图。
图2为本申请的实施方式的负极的锂离子嵌入石墨层示意图。
具体实施方式
为使本申请的目的、技术方案和优点更加清楚，下面将结合实施例对本申请的技术方案进行清楚、完整地描述，显然，所描述的实施例是本申请一部分实施例，而不是全部的实施例。在此所描述的有关实施例为说明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。本领域技术人员基于本申请提供的技术方案及所给出的实施例，所获得的所有其他实施例，都属于本申请保护的范围。
除非另有说明，本申请中使用的术语具有本领域技术人员通常所理解的公知含义。除非另有说明，本申请中提到的各参数的数值可以用本领域常用的各种测量方法进行测量 (例如，可以按照在本申请的实施例中给出的方法进行测试)。
术语“中的至少一者”、“中的至少一个”、“中的至少一种”或其他相似术语所连接的项目的列表可意味着所列项目的任何组合。例如，如果列出项目A及B，那么短语“A或B中的至少一者”意味着仅A；仅B；或A及B。在另一实例中，如果列出项目A、B及C，那么短语“A、B或C中的至少一者”意味着仅A；或仅B；仅C；A及B(排除C)；A及C(排除B)；B及C(排除A)；或A、B及C的全部。项目A可包含单个组分或多个组分。项目B可包含单个组分或多个组分。项目C可包含单个组分或多个组分。
为保证高能量密度性能(容量，首效，压实密度)的同时满足安全性、循环及循环膨胀，本申请一方面通过选取易石墨化前驱体，提升负极活性材料克容量，满足能量密度需求，另一方面同时控制负极活性材料颗粒形貌为细长型，搭载磁化技术，使颗粒在集流体上按一定的方向排布，可以在获得高能量密度的同时控制负极极片的膨胀，从而大大改善锂离子电池的快速充放电性能。
一、负极活性材料
本申请提供了一种负极活性材料，所述负极活性材料满足如下关系：0.1≤AR 10＜0.2，0.2≤AR 50＜0.4，其中，颗粒体积累积分布为10％时负极活性材料的宽长比为AR 10，颗粒体积累积分布为50％时负极活性材料的宽长比为AR 50。
如本文中所使用，负极活性材料的“宽长比”指的是负极活性材料颗粒的宽径与长径的比值。负极活性材料的宽长比可通过动态颗粒图像分析(例如，使用新帕泰克QICPIC动态颗粒图像分析仪)获得。负极活性材料颗粒的“宽径”指的是与颗粒的投影图像相切的平行线之间的最小数值。负极活性材料颗粒的“长径”指的是与颗粒的投影图像相切的平行线之间的最大数值。负极活性材料的宽长比较小时，负极活性材料颗粒呈细长形状。
如本文中所使用，“AR n”指的是当负极活性材料的颗粒体积累计分布为n％时所对应的负极活性材料颗粒的宽长比。“AR 10”表示当负极活性材料的颗粒体积累计分布为10％时所对应的负极活性材料颗粒的宽长比。“AR 50”表示当负极活性材料的颗粒体积累计分布为50％时所对应的负极活性材料颗粒的宽长比。“AR 90”表示当负极活性材料的颗粒体积累计分布为90％时所对应的负极活性材料颗粒的宽长比。
根据本申请的一些实施方式，所述负极活性材料包含一次颗粒。
根据本申请的一些实施方式，AR 10可以为0.11、0.12、0.13、0.14、0.15、0.16、 0.17、0.18、0.19以及它们之间的任意值。在本申请的一些实施例中，AR 50可以为0.22、0.24、0.26、0.28、0.30、0.31、0.33、0.35、0.39以及它们之间的任意值。
根据本申请的一些实施方式，所述负极活性材料满足0.4≤AR 90≤0.8，AR 90表示在颗粒粒型分布中，颗粒体积累积分布为90％时负极活性材料的宽长比。在本申请的一些实施例中，AR 90可以为0.45、0.48、0.53、0.55、0.57、0.60、0.63、0.65、0.70、0.75以及它们之间的任意值。在此范围内负极活性材料中细长型颗粒占比较高，可加快锂离子的快速脱嵌，提高二次电池的倍率性能。
根据本申请的一些实施方式，所述负极活性材料满足1.3＜AR 90/AR 50＜3.5。在本申请的一些实施例中，AR 90/AR 50可以为1.4、1.5、1.7、1.9、2.0、2.3、2.5、2.7、2.9、3.0、3.2、3.5以及它们之间的任意值。控制负极活性材料颗粒宽长比分布此范围内，可进一步提高锂离子的脱嵌速度，提高二次电池的倍率性能，改善负极的形变。
根据本申请的一些实施方式，所述负极活性材料满足：1.5≤AR 90/AR 50≤3，可进一步提高锂离子的脱嵌速度，改善负极的形变和提高二次电池的倍率性能。
本申请的负极活性材料的宽长比分布满足0.1≤AR 10＜0.2，0.2≤AR 50＜0.4，0.4≤AR 90≤0.8时，制备的负极活性材料颗粒大部分为细长型，在此范围内负极活性材料的克容量高。当负极活性材料颗粒的长径与平行于集流体的方向呈45°至90°时，可降低锂离子传输过程中的传输路径，加快锂离子的快速脱嵌，并且可以使负极活性材料颗粒在锂离子嵌入和脱出的过程中受到的应力朝各个方向均匀释放，以达到改善变形的效果。
根据本申请的一些实施方式，所述负极活性材料满足1.5≤Dv99/Dv50≤4.5。在本申请的一些实施方式中，Dv99/Dv50可以为1.8、2.0、2.2、2.5、2.7、3.0、3.3、3.5、3.8、4.0、4.3以及它们之间的任意值。本申请中当负极活性材料颗粒长径垂直于集流体排布，颗粒粒度太大时，制备的负极经过一定压力处理后易于在负极活性材料层表面产生凸点，凸点一方面会影响负极极片的外观，另一方面容易析锂影响电池的循环性能。并且颗粒太大也不利于锂离子的嵌入和脱出。因此需要将负极活性材料颗粒粒度控制在上述的范围内。
根据本申请的一些实施方式，所述负极活性材料满足：2≤Dv99/Dv50≤4，可进一步提高锂离子的嵌入和脱出，改善电池的循环性能。
根据本申请的一些实施方式，所述负极活性材料的克容量≥355mAh/g。在本申请 的一些实施例中，所述负极活性材料的克容量为355mAh/g至370mAh/g。在本申请的一些实施例中，所述负极活性材料的克容量可以为358mAh/g、360mAh/g、362mAh/g、365mAh/g、368mAh/g、370mAh/g以及它们之间的任意值。
根据本申请的一些实施方式，通过X射线衍射法测得的负极活性材料的004晶面衍射峰面积C004与110晶面衍射峰面积C110的比值满足10≤C004/C110≤40，例如C004/C110可以为12、15、17、20、23、25、28、30、33、35、37、39以及它们之间的任意值。负极活性材料的C004/C110在上述范围内，更有利于锂离子的嵌入和脱出。
根据本申请的一些实施方式，所述负极活性材料的004晶面衍射峰面积C004与110晶面衍射峰面积C110的比值满足10≤C004/C110≤30，进一步加速锂离子的嵌入和脱出，降低电池的膨胀和改善电池的循环性能。
根据本申请的一些实施方式，负极活性材料的压实密度≥1.90g/cm 3。在一些实施例中，负极活性材料的压实密度为粉末压实密度。在一些实施例中，所述负极活性材料在5t的测试压力下的压实密度≥1.90g/cm 3，负极活性材料的压实密度与制备成负极后的负极材料可承受的压力相关，高压实密度的材料有利于制备高体积能量密度的电池。
根据本申请的一些实施方式，所述负极活性材料包括人造石墨。在一些实施例中，所述人造石墨包含针状焦人造石墨、石油焦人造石墨或沥青人造石墨中的至少一种。在一些实施例中，所述负极活性材料的表面的至少一部分含有无定形碳层。在一些实施例中，所述人造石墨的原料包含针状焦、石油焦、沥青中的至少一种，所述原料经粉碎至一定粒度后经过大于等于2800℃的石墨化处理得到所述人造石墨。
二、负极
本申请提供了一种负极，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含第一方面所述的负极活性材料。
根据本申请的一些实施方式，所述负极包含长径方向与负极集流体的夹角θ满足45°≤θ≤90°的负极活性材料颗粒。在一些实施方式，所述负极活性材料包含长径方向与负极集流体的夹角θ满足50°≤θ≤90°的颗粒。在一些实施例中，夹角θ为45°、50°、55°、60°、65°、70°、80°、85°、90°以及它们之间的任意值。本申请中所述夹角θ为颗粒的长径方向与负极集流体的夹角中的锐角或直角，如图1所示，夹角分布可通过偏光显微镜测得。
在本申请的一些实施方式，所述负极包含长径方向与负极集流体的夹角θ满足50°≤θ≤85°的负极活性材料颗粒。在本申请的一些实施例中，所述负极包含长径方向与负极集流体的夹角θ满足55°≤θ≤85°的负极活性材料颗粒。
根据本申请的一些实施方式，所述负极中，负极活性材料颗粒的长径方向与负极集流体的夹角θ满足45°≤θ≤90°。在一些实施例中，所述负极中至少50％的负极活性材料颗粒的长径方向与负极集流体的夹角θ满足45°≤θ≤90°，例如至少60％、至少70％、至少80％或至少90％的负极活性材料颗粒的长径方向与负极集流体的夹角θ满足45°≤θ≤90°。
根据本申请的一些实施例，所述负极中，负极活性材料颗粒的长径方向与负极集流体的夹角θ满足50°≤θ≤85°。根据本申请的一些实施例，所述负极中，负极活性材料的长径方向与负极集流体的夹角θ满足55°≤θ≤85°。根据本申请的一些实施例，所述负极中，负极活性材料的长径方向与负极集流体的夹角θ满足65°≤θ≤90°。在一些实施中，负极中，负极活性材料颗粒的长径方向与集流体的夹角θ为90°，即负极活性材料的长径方向与集流体垂直。
负极活性材料颗粒与颗粒之间呈一定的孔隙率按不同的取向一层一层堆积在集流体表面形成负极活性材料层。常规工艺制备负极时细长颗粒易于长边与集流体平行，短边易于垂直于集流体方向，这样的分布导致锂离子不易于在颗粒与颗粒之间的缝隙通过嵌入。根据本申请的一些实施方式，本申请的负极中，负极活性材料颗粒如图1所示，长径与集流体呈一定的角度排布在集流体上，排布的角度≥45°，这样在嵌锂过程中使得锂离子嵌入到石墨层中的路径大大缩短，可以有效的提升锂离子的嵌锂速度。同时，在嵌锂的过程中由于长径与集流体所呈的夹角≥45°，因此嵌锂时如图2所示，锂离子从短径方向嵌入到负极活性材料层中，因此垂直于负极方向的膨胀大大减小。
根据本申请的一些实施方式，通过X射线衍射法测得的负极的004晶面衍射峰面积C004与110晶面衍射峰面积C110的比值满足C004/C110≤15，例如C004/C110可以为5、7、8、9、10、11、12、13、14、15以及它们之间的任意值。在一些实施例中，所述负极的004晶面衍射峰面积C004与110晶面衍射峰面积C004的比值满足C004/C110≤13。负极的C004/C110在上述范围内更有利于锂离子的嵌入和脱出。在本申请的一些实施例中，负极的C004/C110小于负极活性材料的C004/C110。本申请中通过特殊的方式使得长径颗粒与平行于集流体的方向呈45°至90°的角度，这样负极的C004/C110 的比值变小，从而更有利于锂离子的脱嵌。
根据本申请的一些实施方式，电解液在所述负极中的浸润性良好，满足浸润时间≤2min。
根据本申请的一些实施方式，所述负极包括负极集流体和负极活性材料层，其中所述负极活性材料层设置于所述负极集流体的至少一个表面上，所述负极活性材料层包括前述任一种负极活性材料。
在一些实施例中，所述负极活性材料层还包括粘结剂，所述粘结剂包括聚偏氟乙烯、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、羧甲基纤维素钠、聚乙烯呲咯烷酮、聚乙烯醚、聚甲基丙烯酸甲酯、聚四氟乙烯及聚六氟丙烯、丁苯橡胶、丙烯酸酯和环氧树脂中的一者或多者。
在一些实施例中，所述负极还包括位于所述负极活性材料层和所述集流体之间的导电涂层，所述导电涂层包括碳纤维、科琴黑、乙炔黑、碳纳米管和石墨烯等导电剂中的一者或多者。在一些实施例中，负极的集流体可以包括铜箔、铝箔、镍箔或碳基集流体中的至少一种。
根据本申请的一些实施方式，本申请负极的制备方法包括将包含负极活性材料的浆料在磁场存在的条件下，涂覆于集流体上。在本申请的一些实施例中，所述方法包括将包含负极活性材料的浆料在磁场存在的条件下，涂覆于集流体上，使得所述负极活性材料的长径方向与负极集流体的夹角θ满足45°≤θ≤85°。在一些实施例中，所述磁场的磁感应强度为3000Gs至7200Gs。
在一些实施例中，利用石墨的逆磁性性能，在负极浆料涂覆在集流体上时施加一定量的磁感应强度，例如强度为3000Gs至7200Gs，经过该磁感应强度处理后的负极活性材料颗粒可以以短径平行于集流体，长径与集流体垂直的方式排布在集流体上。通过这种处理可有效的使负极活性材料例如石墨的嵌锂端面沿平行于集流体的方向排布，从而提升锂离子的嵌锂速度。
三、二次电池
本申请的二次电池包锂二次电池，包括锂金属二次电池、锂离子二次电池、锂聚合物二次电池或锂离子聚合物二次电池。在一些实施例中，本申请的二次电池包括正极、第二方面所述的负极、隔离膜和电解液。
在一些实施例中，所述二次电池50％SOC状态下拆解得到负极极片，负极极片的厚度 使用万分尺测量，为了确保测量的代表性，测试14个点取平均值，所述负极极片与未充电状态的负极极片比较，负极极片厚度的增加率≤15％。
在一些实施例中，所述二次电池循环50圈后测得的电池厚度与50％SOC状态下测试的电池厚度比较，电池厚度的增加值≤5％，电池厚度采用千分尺测量。
在一些实施例中，所述二次电池在25℃的条件下采用5C充电得到的容量与0.5C充电得到的容量比值保持率≥90％。
1、负极
本申请的二次电池中的负极包括第二方面所述的负极。
2、正极
可用于本申请的实施例中正极的材料、构成和其制造方法包括任何现有技术中公开的技术。
根据本申请的一些实施方式，正极包括集流体和位于该集流体上的正极活性材料层。根据本申请的一些实施方式，正极活性材料包括，但不限于：钴酸锂(LiCoO 2)、锂镍钴锰(NCM)三元材料、磷酸亚铁锂(LiFePO 4)或锰酸锂(LiMn 2O 4)。
根据本申请的一些实施方式，正极活性材料层还包括粘合剂，并且可选地包括导电材料。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。在一些实施方式中，粘结剂包括：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、环氧树脂或尼龙等。
根据本申请的一些实施方式，导电材料包括，但不限于：基于碳的材料、基于金属的材料、导电聚合物和它们的混合物。在一些实施例中，基于碳的材料选自天然石墨、人造石墨、碳黑、乙炔黑、科琴黑、碳纤维或其任意组合。在一些实施例中，基于金属的材料选自金属粉、金属纤维、铜、镍、铝或银。在一些实施例中，导电聚合物为聚亚苯基衍生物。
根据本申请的一些实施方式，集流体可以包括，但不限于：铝箔。
3、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。
在一些实施例中，所述电解液包括有机溶剂、锂盐和添加剂。根据本申请的电解液的 有机溶剂可为现有技术中已知的任何可作为电解液的溶剂的有机溶剂。根据本申请的电解液中使用的电解质没有限制，其可为现有技术中已知的任何电解质。根据本申请的电解液的添加剂可为现有技术中已知的任何可作为电解液添加剂的添加剂。
在一些实施例中，所述有机溶剂包括，但不限于：碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸二乙酯(DEC)、碳酸甲乙酯(EMC)、碳酸二甲酯(DMC)、丙酸丙酯或丙酸乙酯。
在一些实施例中，所述锂盐包括，但不限于：六氟磷酸锂(LiPF 6)、四氟硼酸锂(LiBF 4)、二氟磷酸锂(LiPO 2F 2)、双三氟甲烷磺酰亚胺锂LiN(CF 3SO 2) 2(LiTFSI)、双(氟磺酰)亚胺锂Li(N(SO 2F) 2)(LiFSI)、双草酸硼酸锂LiB(C 2O 4) 2(LiBOB)或二氟草酸硼酸锂LiBF 2(C 2O 4)(LiDFOB)。
在一些实施例中，所述电解液中锂盐的浓度为：0.5mol/L至3mol/L、0.5mol/L至2mol/L或0.8mol/L至1.5mol/L。
在一些实施例中，所述添加剂包括，但不限于：碳酸亚乙烯酯(VC)、碳酸乙烯亚乙酯(VEC)、氟代碳酸乙烯酯(FEC)、二氟代碳酸乙烯酯(DFEC)、1,3-丙烷磺内酯(PS)、硫酸乙烯酯(DTD)、1,3-二氧六环、马来酸酐、己二腈、丁二腈、1,3,5-戊烷三腈、1,3,6-己烷三腈。
4、隔离膜
本申请的二次电池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。
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至少一种。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、聚乙烯烷氧、聚甲基丙烯酸甲酯、聚四氟乙烯和聚六氟丙烯中的至少一 种。
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、聚乙烯烷氧、聚偏氟乙烯、聚(偏氟乙烯-六氟丙烯)中的至少一种。
四、电子装置
本申请进一步提供了一种电子装置，其包括本申请第三方面所述的二次电池。
本申请的电子设备或装置没有特别限定。在一些实施例中，本申请的电子设备包括但不限于，笔记本电脑、笔输入型计算机、移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、电子记事本、计算器、存储卡、便携式录音机、收音机、备用电源、电机、汽车、摩托车、助力自行车、自行车、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机、家庭用大型蓄电池和锂离子电容器等。
实施例
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
将负极活性材料石墨、丁苯橡胶(简写为SBR)和羧甲基纤维素钠(简写为CMC)按照重量比95:2:3在去离子水溶剂中充分搅拌混合，使其形成均匀的负极浆料；将此浆料涂覆于预先涂覆有底涂层(如炭黑)的集流体铜箔上，底涂层的厚度为1.5μm至3μm，负极浆料的涂布重量为Xmg/mm 2(涂布重量为0.032mg/mm 2至0.120mg/mm 2，例如0.032mg/mm 2、0.055mg/mm 2、0.070mg/mm 2、0.090mg/mm 2、0.120mg/mm 2)，负极浆料的双面涂布厚度为Yμm(涂布厚度为70μm至150μm之间，例如70μm、90μm、110μm、130μm、150μm)，在涂覆过程中施加一定的磁通量改变颗粒在集流体上的排布，施加的磁通量大小为3000Gs至7200Gs。烘干后冷压、裁片、焊接极耳，得到负极，也称为负极极片。
石墨的制备方法如下所示：
(1)将石墨前驱体(筛选强针状性原料)采用高效粉碎设备将颗粒粉碎至一定的粒度，然后将粉碎后的颗粒送入分级设备，通过设备的离心分离效果将颗粒的粒度控制在一定的范围内，然后将粉碎后的颗粒送入石墨化炉中进行石墨化，石墨化设备可以为艾奇逊炉、内串式石墨化炉和连续式石墨化炉中的任意一种，进入石墨化炉的物料破碎至所需颗 粒粒度(Dv50为6μm至10μm)；和
(2)在2800℃至3200℃进行石墨化，石墨化后收集得到所需石墨。通过控制前驱体粒径和石墨化温度调整石墨参数。
负极活性材料石墨的宽长比通过如下方式控制：在负极活性材料石墨的制备过程中，将制备好的石墨通过进料系统进入整形区进行打磨，使颗粒表面具有棱角，从而控制颗粒的宽长比和球形度。随后将打磨后的颗粒通过自分流分级区进行分级，得到所需分布的颗粒。
2、正极的制备
将钴酸锂(LiCoO 2)、乙炔黑和聚偏二氟乙烯(PVDF)按重量比96:2:2在适量的N-甲基吡咯烷酮(NMP)溶剂中充分搅拌混合，使其形成均匀的正极浆料。将此浆料涂覆于正极集流体铝箔上，烘干、冷压、裁片、分切后，得到正极。
3、电解液的制备
在含水量<10ppm的氩气气氛手套箱中，将碳酸乙烯酯(简写为EC)、碳酸二乙酯(简写为DEC)和碳酸丙烯酯(简写为PC)按照3:4:3的质量比混合均匀，再将充分干燥的锂盐LiPF 6溶解于上述非水溶剂，最后加入3wt％的氟代碳酸乙烯酯、2wt％的1,3-丙烷磺内酯、2wt％的丁二腈，配成电解液。
4、隔离膜的制备
以7μm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，然后卷绕得到裸电芯；焊接极耳后将裸电芯置于外包装箔铝塑膜中，将上述制备好的电解液注入到干燥后的裸电芯中，经过真空封装、静置、化成、整形、容量测试等工序，获得软包锂离子电池。
二、测试方法
1、负极活性材料的宽长比分布的测试方法
使用新帕泰克QICPIC动态颗粒图像分析仪测试负极活性材料的宽长比分布。
2、负极活性材料的压实密度的测试方法
测试标准参照GB/T 24533-2009《锂离子电池石墨类负极材料》。具体测试方法为称量1.0000±0.0500g的样品置于测试模具(CARVER#3619(13mm)中，然后将样品置于 测试设备中，测试设备为三思纵横UTM7305，测试吨位0.3t至5.0t，本申请中压实密度均为5t时测得的压实密度。压实密度的计算公式为：压实密度＝负极活性材料质量/负极活性材料受力面积/样品的厚度。
3、负极中颗粒长径与集流体夹角的测试方式
负极离子研磨(CP)样品制备流程：
将上述负极极片裁剪为0.5cm×1cm大小，使用导电胶将裁剪好的负极极片黏贴在1cm×1.5cm大小的硅片载体上，然后使用氩离子抛光(参数：8KV的加速电压，每个样品4h)对负极极片的一端进行处理，得到负极CP样品。氩离子抛光是利用高压电场使氩气电离产生离子态，产生的氩离子在加速电压的作用下，高速轰击负极极片表面，对负极极片进行逐层剥蚀而达到抛光的效果。
负极CP制样完成后，利用偏光显微镜对其进行分析。
偏光显微镜操作如下：
图像采集过程：采用Axio imager正置显微镜(Carl Zeiss AG制造、Imagine A2)进行图像采集，将AxioCam MRc5数码相机用连接件与偏振光显微镜连接，以快门时间1.6秒拍摄偏振光显微镜图像，由数码照相机捕捉到的图像自动传输至电脑。
图像分析过程：选取1200像素×1600像素的图像作为解析对象(其相当于480μm×540μm的视野)。采用AxioVision自带的Multiphase软件进行分析。将采集的照片导入到软件后，点击图像上某个取向的点，则所有和测量对象的灰度值和颜色值一致的区域随即也被选定；采用相同的方法选中其他的取向的点，即可得到不同取向不同颜色的区域。利用AxioVision的自动计算软件(Axio Vision SE64Rel.4.9)，测得图像中不同颗粒夹角的数据以及不同夹角所占的比例，根据测得的结果得到负极活性材料颗粒长径。
4、负极活性材料颗粒粒度(Dv50和Dv99)的测试方法
颗粒粒度测试方法参照GB/T 19077-2016。具体流程为称量样品1g与20mL去离子水和微量分散剂混合均匀，置于超声设备中超声5min后将溶液倒入进样系统Hydro 2000SM中进行测试，所用测试设备为马尔文公司生产的Mastersizer 3000。测试过程中当激光束穿过分散的颗粒样品时，通过测量散射光的强度来完成粒度测量。然后数据用于分析计算形成该散射光谱图的颗粒粒度分布。测试所用颗粒折射率为1.8，一个样品测试三次，颗粒粒度最终取三次测试的平均值。
5、负极活性材料层的C004/C110的测试方法
按照中华人民共和国机械行业标准JB/T 4220-2011《人造石墨的点阵参数测定方法》测试负极活性材料层的X射线衍射图谱中的(004)面衍射线图形和(110)面衍射线图形。试验条件如下：X射线采用CuKα辐射，CuKα辐射由滤波片或单色器除去。X射线管的工作电压为30kV至35kV，工作电流为15mA至20mA。计数器的扫描速度为1/4(°)/min。在记录004衍射线图形时，衍射角2θ的扫描范围为53°至57°。在记录110衍射线图形时，衍射角2θ的扫描范围为75°至79°。由(004)面衍射线图形得到的峰面积记为C004。由(110)面衍射线图形得到的峰面积记为C110。计算负极活性材料层的C004/C110的比值。负极活性材料的C004/C110测试方法同负极的C004/C110测试方法，不同之处仅在于采用负极活性材料需先置于有凹槽的玻璃片中压实，然后替代负极。
6、负极活性材料层的孔隙率的测试方法
将负极活性材料层样品制备成完整圆片。每个实施例或对比例测试30个样品，每个样品体积为约0.35cm 3。根据《GB/T24586-2009铁矿石表观密度真密度和孔隙率的测定》标准进行测试负极活性材料层的孔隙率。
7、负极的浸润时间的测试方法
取长50mm、宽50mm的实施例或对比例中制备的负极样品。在干燥条件下，将上述“电解液的制备”中制得的电解液取5mL滴在样品表面，开始计时。待样品表面电解液液滴消失，停止计时。计时时间记为负极的浸润时间。每个实施例或对比例测试30个样品，取平均值。
或将电池以0.1C放电至电压为3V之后拆解电池，取出负极，在70℃条件下烘干，将得到的负极极片裁剪为长50mm、宽50mm的样品，在干燥条件下，将实施例或对比例中使用的电解液滴5mL在样品表面，开始计时。待样品表面电解液液滴消失，停止计时。计时时间记为负极的浸润时间。每个实施例或对比例测试30个样品，取平均值。
8、锂离子液相传递阻抗(Rion)的测试方法
将锂离子电池接入法国比奥罗杰公司生产的Bio-Logic VMP3B电化学工作站进行测试，频率范围为30mHz至50kHz，振幅为5mV。采集数据后采用阻抗复平面图对数据进行分析，得到锂离子液相传递阻抗(Rion)。
9、锂离子电池的5C放电容量保存率的测试方法
将锂离子电池在25℃下静止5分钟后以0.7C的电流恒流充电至4.45V，再以4.45V的恒压充电至0.05C，静置5分钟，然后以0.5C恒流放电至3.0V，静止5分钟。重复上述 充放电过程，以0.1C进行放电，记录锂离子电池的0.1C放电容量，然后以5C进行放电，记录锂离子电池的5C放电容量。通过下式锂离子电池的5C放电容量保存率：
5C放电容量保存率＝5C放电容量/0.1C放电容量×100％。
10、锂离子电池的直流电阻(DCR)的测试方法
在25℃下，将锂离子电池以1.5C恒流充电至4.45V，再以4.45V恒压充电至0.05C，静置30分钟。以0.1C放电10秒，记录电压值为U1，以1C放电360秒，记录电压值为U2。重复充放电步骤5次。“1C”是在1小时内将锂离子电池容量完全放完的电流值。
通过下式计算锂离子电池在25℃下的直流电阻R：
R＝(U2-U1)/(1C-0.1C)。
采用基本相同的方法测试锂离子电池在0℃下的直流电阻，区别仅在于操作温度为0℃。
除非有特别说明，本申请所述的DCR指的是锂离子电池在10％荷电状态(SOC)下的直流电阻。
11、锂离子电池的析锂现象的判断方法
取被测锂离子电池在0℃测试温度下，静置5分钟，以0.8C的电流恒流充电至4.45V，再以4.45V的电压恒压充电至0.05C；静置5分钟，再以0.5C的电流恒流放电至3.0V，静置5分钟。重复上述充放电流程10次后，将电池满充，于干燥房内拆解，拍照记录负极的状态。
根据以下标准判断锂离子电池的析锂程度：
当拆解后的负极整体呈现金黄色，极少部分可观察到灰色；且灰色区域的面积<2％，则判定为不析锂。
当拆解后的负极大部分呈现金黄色，部分位置可观察到灰色；且灰色区域的面积在2％至20％之间，则判定为轻微析锂。
当拆解后的负极整体呈现为灰色，部分位置可观察到金黄色；且灰色区域的面积在20％至60％之间，则判定为析锂。
当拆解后的负极整体呈现灰色且灰色区域的面积＞60％时，则判定为严重析锂。
12、锂离子电池的电荷转移阻抗(Rct)的测试方法
在上述制备锂离子电池的过程中额外接入铜丝作为参比电极，并以20μA的电流在负极镀锂6小时，得到三电极锂离子电池。
将三电极锂离子电池接入法国比奥罗杰公司生产的Bio-Logic VMP3B电化学工作站进行测试，频率范围为30mHz至50kHz，振幅为5mV。采集数据后采用阻抗复平面图对数据进行分析，得到锂离子电池的电荷转移阻抗(Rct)。
13、负极极片沿Z方向厚度增长率测试方法
测试经过冷压处理的负极的厚度，记为T1。将处理后的负极按照锂离子电池的制备步骤制成锂离子电池，将锂离子电池在25℃下静止5分钟后以0.7C的电流恒流充电至3.95V(即，50％SOC)。在干燥条件下拆解锂离子电池，得到拆解后的负极。记录至少14个点的负极厚度，取平均值，记为T2。通过下式计算负极沿Z方向的膨胀率：
Z方向的膨胀率＝(T2-T1)/T1×100％。
14、电池Z轴方向膨胀率
将锂离子电池在45℃下静止5分钟后以0.7C的电流恒流充电至4.45V，再以4.45V的恒压充电至0.05C，静置5分钟。通过MMC测试方法测试锂离子电池三个位置点的厚度，取平均值记为MMC 0。然后将锂离子电池以0.5C的电流恒流放电至3.0V，静止5分钟。重复上述充放电循环50次，记为MMC 50(50代表循环次数)。
通过下式计算锂离子电池在45℃下的循环膨胀率：
循环膨胀率(45℃)＝(MMC x-MMC 0)/MMC 0×100％。
如上所述的MMC测试方法为：使用千分尺测试仪(日本Mitutoyo制造，型号：MDC-25SX)测量靠近负极极耳处的锂离子电池的厚度，每个样品测量三个不同位置，取平均值，记为MMC厚度。
三、测试结果
表1展示了石墨颗粒的宽长比分布、在涂布过程中施加的磁通量的大小对克容量、石墨颗粒粉末C004/C110、负极极片C004/C110、颗粒长径方向与集流体所呈角度、负极极片Z轴方向厚度的增长率以及锂离子电池1的直流阻抗(DCR)的影响。实施例1至实施例26中所用负极活性材料均为同一原料，原料为针状焦，通过3000℃烧结得到，负极活性材料颗粒的Dv50均为8μm，Dv99均为27μm。
表1
Figure PCTCN2022100001-appb-000001
注:θ角为负极中负极活性材料颗粒长径方向与集流体的夹角，所测得夹角值为所有颗粒夹角的平 均值。
如表1所示，实施例1至实施例26，随着负极活性材料颗粒的宽长比的增加，其克容量逐渐减小，粉末C004/C110也逐渐减小。且宽长比越小所需的磁通量越大，这是因为宽长比小的颗粒形貌为如图1所示偏长条形，而对于长条形的颗粒，涂布时颗粒在负极极片上堆积趋向于平行于集流体的方向排布。当负极极片上颗粒的长边平行于集流体时，在脱嵌锂的过程中锂离子需要穿过更长的路径才能嵌入石墨层中。而在涂布的过程中对负极极片施加一定量的磁通量，利用石墨本身的逆磁性，石墨颗粒则会因为磁场的存在而调整排布方向。通过控制施加磁场的大小控制石墨颗粒在负极极片上的排布，负极极片C004/C110相较于粉末反而减小。
通过实施例1至实施例6、实施例7至实施例9、实施例10至实施例12、实施例13至实施例18、实施例19至实施例24的数据可以看出，当负极活性材料颗粒的AR 90的大小固定不变时，随着AR 10的增加或者随着AR 50的增加，其粉末C004/C110值受到影响，这是因为颗粒AR 10增加或者AR 50增加表明颗粒的形貌趋向于类球形，因此XRD测得的粉末的C004/C110产生变化。而在负极极片层面，由于涂布过程中引入了磁场，因此负极极片的C004/C110的变化规律虽然也随着AR 10和AR 50的增加而减小，但是其变化率却小很多。并且膨胀的变化影响负极极片的C004/C110的变化。
如实施例23和实施例24所示，当施加的磁场大小相同时，AR 10较大的材料，颗粒长径方向与集流体方向所呈的夹角较大，这表明更多的长径与集流体方向呈垂直排布，这样可以有效缩短锂离子的传递路径，降低负极极片膨胀，因此负极极片的厚度增长率明显减小。
实施例24和实施例25相比，实施例25的负极活性材料颗粒的AR 90偏大，在相同的磁通量条件下，实施例25的颗粒长径与集流体的夹角反而减小，这是因为当类球型颗粒占比过多时，施加一定的磁通量后颗粒的排布虽然发生改变，但是变化非常小。同样的如对比例1所示，负极活性材料颗粒的AR 10仅为0.05，表明一部分颗粒形貌是非常细长的，因此需要施加非常大的磁场才能将其C004/C110的比值控制在一定的范围内。
从对比例2可以看出，对比例2的负极活性材料颗粒的的AR 10，AR 50和AR 90都较大，颗粒的形貌偏于圆润，因此所需的磁通量非常小。但是该材料的克容量也很低。本申请针对强针状性克容量高的石墨，将其宽长比控制在一定的范围内后对其施加所需的磁通量调整其在负极极片上的排布可以获得高能量密度的同时控制负极极片的膨胀。
表2展示的是在不同颗粒粒径条件下，使用5000Gs的磁通量对涂布负极极片进行处理时，颗粒的不同宽长和颗粒粒度比对粉末C004/C110与负极极片C004/C110以及电池性能的影响。
表2
Figure PCTCN2022100001-appb-000002
注:θ角为负极极片的颗粒长径方向与集流体的夹角，所测得夹角值为所有颗粒夹角的平均值。
如实施例27和实施例30，实施例28和实施例29所示，颗粒粒度分布相同，宽长比不同的负极活性材料，当宽长比偏大时，粉末C004/C110偏小，相同的磁通量条件下负极极片的C004/C110越小，负极活性材料颗粒的长径与集流体的夹角越大，反馈到电池性能则为电池沿Z轴的膨胀较小。这是因为宽长比大的颗粒比较圆润，越容易在磁场下旋转至垂直于集流体方向排布。
如实施例30和实施例31所示，颗粒的宽长比类似，颗粒的粒度分布不同，颗粒粒径分布越大，粉末C004/C110越大，因此负极极片C004/C110大，对应的电池性能则是沿Z轴的膨胀增长率大。
对比例3的负极活性材料颗粒的宽长比AR 10小，在一定的磁通量作用下，极片C004/C110仍然很大，因此电池沿Z轴的膨胀大，且由于部分颗粒长径太长，不利于锂离子的脱嵌，因此在一定的倍率条件下容易析锂。
表3展示的是使用5000Gs的磁通量对涂布的负极极片进行处理时，颗粒的不同宽长比对电池性能的影响。
表3
Figure PCTCN2022100001-appb-000003
如实施例39至实施例43所示，宽长比越大的材料，在相同的磁通量处理条件下，所制备得到的负极活性物质层的孔隙率增大，因此负极极片的电解液浸润时间缩短。同时，负极活性材料的宽长比增大，包含该材料的锂离子电池的锂离子传递阻抗(Rion)、电荷转移阻抗(Rct)和直流电阻(DCR)减小，5C倍率下的放电容量保持率越大。而对于实施例45，其负极活性材料的宽长比最小，因此在同样的磁通量处理条件下，由于部分颗粒仍平行于集流体排布，负极活性物质层的孔隙率较小，电解液进入负极极片的浸润时间较长，锂离子穿过石墨颗粒嵌入石墨层间的阻抗也较大。因此在实际应用过程中需同时调控磁通量和颗粒的长径比以及颗粒的粒径以便发挥最好的性能。

Claims (12)

  1. 一种负极活性材料，其中所述负极活性材料颗粒满足如下关系：0.1≤AR 10＜0.2，0.2≤AR 50＜0.4，
    其中颗粒体积累积分布为10％时负极活性材料的宽长比为AR 10，颗粒体积累积分布为50％时负极活性材料的宽长比为AR 50。
  2. 根据权利要求1所述的负极活性材料，其中，0.4≤AR 90≤0.8，AR 90表示在颗粒粒型分布中，颗粒体积累积分布为90％时负极活性材料的宽长比。
  3. 根据权利要求2所述的负极活性材料，其中，1.3＜AR 90/AR 50＜3.5。
  4. 根据权利要求1所述的负极活性材料，其中，所述负极活性材料满足条件(a)至(d)中的至少一种：
    (a)所述负极活性材料满足1.5≤Dv99/Dv50≤4.5；
    (b)所述负极活性材料的克容量≥355mAh/g；
    (c)所述负极活性材料的004晶面衍射峰面积C004与110晶面衍射峰面积C110的比值满足10≤C004/C110≤40；
    (d)所述负极活性材料的压实密度≥1.90g/cm 3。
  5. 根据权利要求1至4中任一项所述的负极活性材料，其中，所述负极活性材料满足条件(1)至(3)中的至少一者：
    (1)1.5≤AR 90/AR 50≤3；
    (2)2≤Dv99/Dv50≤4；
    (3)所述负极活性材料的004晶面衍射峰面积C004与110晶面衍射峰面积C110的比值满足10≤C004/C110≤30。
  6. 根据权利要求1所述的负极活性材料，其中，包含人造石墨，所述人造石墨包含针状焦人造石墨、石油焦人造石墨或沥青人造石墨中的至少一种。
  7. 一种二次电池，其包括正极、隔离膜、电解液和负极，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含如权利要求1至6中任一项所述的负极活性材料。
  8. 根据权利要求7所述的二次电池，其中，所述负极包含长径方向与所述负极集流体的夹角θ满足45°≤θ≤90°的负极活性材料颗粒。
  9. 根据权利要求7所述的二次电池，其中，所述负极的004晶面衍射峰面积C004与110晶面衍射峰面积C004的比值满足C004/C110≤15。
  10. 根据权利要求7所述的二次电池，其中，所述负极的电解液浸润时间≤2min。
  11. 根据权利要求7至10中任一项所述的二次电池，其中，所述负极满足条件(4)和(6)中的至少一者：
    (4)所述负极包含长径方向与所述负极集流体的夹角θ满足55°≤θ≤85°的负极活性材料颗粒；
    (5)所述负极的004晶面衍射峰面积C004与110晶面衍射峰面积C004的比值满足C004/C110≤13；
    (6)所述负极中至少50％的负极活性材料颗粒的长径方向与负极集流体的夹角θ满足45°≤θ≤90°。
  12. 一种电子装置，其包含如权利要求7至11中任一项所述的二次电池。
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