WO2024036485A1 - Negative electrode active material, manufacturing method, secondary battery, and electrical device - Google Patents

Negative electrode active material, manufacturing method, secondary battery, and electrical device Download PDF

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WO2024036485A1
WO2024036485A1 PCT/CN2022/112832 CN2022112832W WO2024036485A1 WO 2024036485 A1 WO2024036485 A1 WO 2024036485A1 CN 2022112832 W CN2022112832 W CN 2022112832W WO 2024036485 A1 WO2024036485 A1 WO 2024036485A1
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lithium
graphite
active material
coating layer
negative active
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PCT/CN2022/112832
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French (fr)
Chinese (zh)
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俸靖杰
李星
张辰辰
王朴
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宁德时代新能源科技股份有限公司
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Priority to PCT/CN2022/112832 priority Critical patent/WO2024036485A1/en
Publication of WO2024036485A1 publication Critical patent/WO2024036485A1/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
    • 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
    • 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 lithium batteries, and in particular to a negative active material, a manufacturing method, a secondary battery and an electrical device.
  • lithium-ion batteries are widely used in energy storage power systems such as hydraulic, thermal, wind and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, Military equipment, aerospace and other fields. Due to the great development of lithium-ion batteries, higher requirements have been put forward for their energy density, cycle performance and safety performance.
  • SEI film solid electrolyte interface film
  • the components of the SEI film are inorganic lithium salts in the inner layer, including Li 2 CO 3 , Li 2 O, and LiF, and organic lithium salts in the outer layer, including lithium alkyl esters.
  • SEI film has a crucial impact on the performance of electrode materials.
  • the formation of the SEI film consumes part of the active lithium, which increases the irreversible capacity of the first charge and discharge and reduces the charge and discharge efficiency of the electrode material; on the other hand, the SEI film is insoluble in organic solvents and can exist stably in organic electrolyte solutions.
  • solvent molecules cannot pass through this passivation film, which can effectively prevent the co-embedding of solvent molecules and avoid the damage to the electrode material caused by the co-embedding of solvent molecules, thus greatly improving the cycle performance and service life of the electrode. Therefore, finding effective ways to improve the performance of SEI membranes has always been a research hotspot in the world's electrochemistry community.
  • This application was made in view of the above issues, and its purpose is to provide a negative active material whose internal pores and particle surfaces are coated with lithium salts, so that the negative active material has higher structural stability, thereby effectively The first Coulombic efficiency and cycle stability of the corresponding battery are greatly improved.
  • a first aspect of the present application provides a negative active material, which includes graphite particles with internal pores and a lithium salt coating layer coating the internal pores of the graphite particles and the outer surface of the particles, wherein the interior of the graphite particles
  • the weight ratio of the lithium element in the pores to the lithium element on the outer surface of the graphite particles is 1 to 10:1.
  • the negative active material of the present application is coated with lithium salt in both its internal pores and particle surface, and reaches a specific weight ratio of lithium element in the internal pores to lithium element on the outer surface of the graphite particles, wherein the coating layer
  • the lithium salt component is part of the SEI film component formed spontaneously in the lithium ion electrochemical system, and the coating layer can inhibit the active sites, thereby reducing the consumption of active lithium during the first formation of the SEI film of the corresponding battery; due to
  • the internal pores of the negative active material are also coated with lithium salt, so that after the internal pores of the graphite are subsequently exposed due to expansion and contraction of the cycle volume, the graphite surface can be protected and the consumption of lithium salt can be further reduced. Therefore, when the negative active material is used as the negative electrode of a lithium-ion battery, it can effectively improve the first Coulombic efficiency and cycle stability of the lithium-ion battery.
  • the lithium salt coating layer meets at least one of the following characteristics:
  • the content of the lithium salt coating layer is 0.01%-6%, based on the total weight of the negative active material
  • the thickness of the lithium salt coating layer in the internal pores of the graphite particles is 1-20 nm, and the thickness of the lithium salt coating layer on the outer surface of the graphite particles is 1-30 nm.
  • the negative active material satisfies at least one of the following characteristics:
  • the graphite is natural graphite
  • the lithium salt is an inorganic lithium salt, optionally one or more selected from the group consisting of carbonate, lithium oxide, lithium phosphate and lithium fluoride.
  • the structural stability of the negative active material is further improved, thereby effectively improving the first Coulombic efficiency and cycle stability of the corresponding battery.
  • the average volume particle diameter D v50 of the negative active material is 10-30 ⁇ m.
  • the structural stability of the negative active material is further improved, thereby effectively improving the first Coulombic efficiency and cycle stability of the corresponding battery.
  • the coating amount of the carbon coating layer is 0.2-10%, based on the total amount of the negative active material Weight scale. Therefore, by adding a carbon coating layer between the graphite and lithium salt coating layers, the instability of the surface after the internal pores of the particles are exposed is further suppressed, and the structural stability of the negative electrode active material is improved, thereby effectively improving the corresponding The first Coulombic efficiency and cycle stability of the battery.
  • a second aspect of the application provides a method for preparing a negative active material, which includes:
  • the negative active material includes graphite with internal pores and a lithium salt coating layer covering the internal pores and outer surface of the graphite, wherein the weight ratio of the lithium element in the internal pores of the graphite to the lithium element on the outer surface of the graphite is 1 ⁇ 10:1.
  • the method of the present application successively coats the flake graphite and the shaped spherical graphite to obtain a negative active material in which the internal pores and the outer surface of the graphite are coated with lithium salt, in which the surface of the coated flake graphite is shaped. Finally, the internal pore surface of spherical graphite is formed.
  • the resulting negative active material has higher surface stability, thereby effectively improving the first Coulombic efficiency and cycle stability of the corresponding battery.
  • carbon coating or surface treatment is performed between steps (1) and (2) or between steps (3) and (4).
  • steps (1) and (2) or between steps (3) and (4) are further suppressed, and the surface stability of the negative active material is improved, thereby effectively improving the first Coulombic efficiency and cycle stability of the corresponding battery.
  • steps (3) and (4) carbon coating or surface treatment is performed.
  • graphite surface defects and activity of active sites are further suppressed, and the surface stability of the negative active material is improved, thereby effectively improving the first Coulombic efficiency and cycle stability of the corresponding battery.
  • the lithium-containing raw material includes at least one of lithium carbonate, lithium hydroxide, lithium carboxylate, lithium sulfate, lithium fluoride, and lithium phosphate, optionally Contains at least one of lithium carbonate, lithium acetate, lithium citrate, lithium oxalate, lithium sulfate, lithium fluoride, and lithium phosphate. Therefore, the type of lithium salt in the coating layer is further optimized to improve the surface stability of the negative active material, thereby effectively improving the first Coulombic efficiency and cycle stability of the corresponding battery.
  • step (2) includes: preparing lithium-containing raw materials into corresponding solutions; dispersing the flake graphite in the solution to obtain a mixture; filtering, drying and dispersing the mixture, A solid powder is obtained; the solid powder is sintered at 300-900°C for 0.5-8 hours under a protective atmosphere or vacuum to form a lithium salt coating layer on the surface of the flake graphite.
  • the quality of the flake graphite surface coating layer is further optimized, and the surface stability of the negative active material is improved, thereby effectively improving the first Coulombic efficiency and cycle stability of the corresponding battery.
  • a third aspect of the present application also provides a secondary battery, characterized in that:
  • the secondary battery thus obtained has improved first Coulombic efficiency and cycle stability.
  • a fourth aspect of the present application provides an electrical device, including a secondary battery selected from the second aspect of the present application.
  • the internal pores and particle surfaces of the negative active material of the present application are coated with lithium salts, so that the negative active material has higher structural stability, thereby effectively improving the first Coulombic efficiency and cycle stability of the corresponding battery.
  • Figure 1 is an SEM image of a cross-section of natural graphite coated with the negative active material in Example 1 of the present application;
  • Figure 2 is an SEM image of a cross section of existing artificial graphite.
  • FIG. 3 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG. 4 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 1 .
  • FIG. 5 is a schematic diagram of a power consumption device using a secondary battery as a power source according to an embodiment of the present application.
  • Secondary battery 51. Housing; 52. Electrode assembly; 53. Cover plate; 6. Electrical device.
  • Ranges disclosed herein are defined in terms of lower and upper limits. A given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive of the endpoints, and may be arbitrarily combined, that is, any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, understand that ranges of 60-110 and 80-120 are also expected. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-5.
  • the numerical range “a-b” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers.
  • the numerical range “0-5" means that all real numbers between "0-5" have been listed in this article, and "0-5" is just an abbreviation of these numerical combinations.
  • a certain parameter is an integer ⁇ 2
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • step (c) means that step (c) may be added to the method in any order.
  • the method may include steps (a), (b) and (c). , may also include steps (a), (c) and (b), may also include steps (c), (a) and (b), etc.
  • condition "A or B” is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists) ; Or both A and B are true (or exist).
  • a solid electrolyte interface film (SEI film) will be formed on the surface of the negative electrode during the first charging process.
  • the reaction stops until the SEI film completely covers the surface of the negative electrode.
  • the components of the SEI film are inorganic lithium salts in the inner layer, including Li 2 CO 3 , Li 2 O, and LiF, and organic lithium salts in the outer layer, including lithium alkyl esters.
  • the formation of SEI film has a crucial impact on the performance of electrode materials.
  • the formation of the SEI film consumes part of the active lithium, which increases the irreversible capacity of the first charge and discharge and reduces the charge and discharge efficiency of the electrode material; on the other hand, the SEI film is insoluble in organic solvents and can exist stably in organic electrolyte solutions. Moreover, solvent molecules cannot pass through this passivation film, which can effectively prevent the co-embedding of solvent molecules and avoid the damage to the electrode material caused by the co-embedding of solvent molecules, thus greatly improving the cycle performance and service life of the electrode. Therefore, finding effective ways to improve the performance of SEI membranes has always been a research hotspot in the world's electrochemistry community.
  • the negative active material of the first aspect of the present invention is pre-coated with lithium salts that constitute a part of the SEI film on both its internal pores and particle surfaces, and achieves a specific lithium element in the internal pores and lithium on the outer surface of the graphite particles.
  • the weight ratio of the elements reduces the consumption of active lithium during the first formation of the SEI film of the corresponding battery; since the internal pores of the negative active material are also coated with lithium salts, subsequent internal pores of graphite can be generated due to cycle volume. After being exposed due to expansion and contraction, the graphite surface is protected and further reduces lithium salt consumption. Therefore, when the negative active material is used as the negative electrode of a lithium-ion battery, it can effectively improve the first Coulombic efficiency and cycle stability of the lithium-ion battery.
  • the first aspect of the present application provides a negative active material, which includes graphite particles having internal pores and a lithium salt coating layer coating the internal pores of the graphite particles and the outer surface of the particles, wherein the graphite particles
  • the weight ratio of the lithium element in the internal pores to the lithium element on the outer surface of the graphite particles is 1 to 10:1, preferably 1 to 5:1, and more preferably 2 to 3:1.
  • the negative active material of the present application is coated with lithium salt in both its internal pores and particle surface, and reaches a specific weight ratio of lithium element in the internal pores to lithium element on the outer surface of the graphite particles, wherein the coating layer
  • the lithium salt component is part of the SEI film component formed spontaneously in the lithium ion electrochemical system, and the coating layer can inhibit the active sites, thereby reducing the consumption of active lithium during the first formation of the SEI film of the corresponding battery; due to
  • the internal pores of the negative active material are also coated with lithium salt, so that after the internal pores of the graphite are subsequently exposed due to expansion and contraction of the cycle volume, the graphite surface can be protected and the consumption of lithium salt can be further reduced. Therefore, when the negative active material is used as the negative electrode of a lithium-ion battery, it can effectively improve the first Coulombic efficiency and cycle stability of the lithium-ion battery.
  • the term "internal pores” includes pores or gaps inside graphite particles that are connected or disconnected from the outside air, see Figure 1 .
  • the lithium salt coating layer of the internal pores is obtained by first coating the surface of the flake graphite with lithium salt, and then shaping the lithium salt coating layer on the surface of the flake graphite to form the lithium salt coating layer on the surface of the internal pores of the spherical graphite. get.
  • the content of the lithium salt coating layer is 0.01%-6%, preferably 1%-5.2%, more preferably 2.7-5.15%, based on the total weight of the negative active material.
  • the thickness of the lithium salt coating layer in the internal pores of the graphite particles is 1-20 nm, preferably 2-25 nm, and further preferably 5-12 nm; the thickness of the lithium salt coating layer on the outer surface of the graphite particles is It is 1-30nm, preferably 2-25nm, further preferably 5-12nm.
  • At least 70%, preferably 90%, further preferably 95%, further preferably 98% and most preferably 100% of the surface of the internal pores of the graphite particles are covered by a lithium salt coating layer, based on the interior of the graphite particles. Surface area of all pores.
  • the graphite is natural graphite, and its specific surface area is 2 to 15 m 2 /g.
  • the lithium salt is an inorganic lithium salt, optionally one or more selected from the group consisting of carbonate, lithium oxide, lithium phosphate and lithium fluoride, further optionally selected from the group consisting of lithium carbonate, lithium oxide and fluoride.
  • the inorganic lithium salt is usually preferably a component in the SEI film formed spontaneously in a lithium battery or a component that plays the same role as the SEI film formed spontaneously, that is, it can conduct lithium ions but cannot conduct electrons.
  • the natural graphite has a large specific surface area and many surface active sites, and will consume more active lithium during the first formation of the SEI film.
  • the negative active material of the present application of natural graphite with a lithium salt coating layer on both the internal pores and the external surface is used in a lithium-ion battery, it can not only reduce the consumption of active lithium during the first formation process, but also reduce the subsequent internal pores of the natural graphite due to the After the cycle volume expands and contracts and is exposed, the surface of the natural graphite is protected and the consumption of lithium salt is further reduced; thus, the structural stability of the negative active material is further improved, thereby effectively improving the first Coulombic efficiency and cycle stability of the corresponding battery. sex.
  • the average volume particle diameter D v50 of the negative active material is 10-30 ⁇ m, preferably 14-18 ⁇ m.
  • the average volume particle size Dv50 is the particle size corresponding to when the cumulative volume distribution percentage of the sample reaches 50%; it is measured using a laser particle size analyzer such as the Mastersizer 3000 laser particle size analyzer of Malvern Instruments Co., Ltd. in the UK.
  • the structural stability of the negative active material is further improved, thereby effectively improving the first Coulombic efficiency and cycle stability of the corresponding battery.
  • the coating amount of the carbon coating layer is 0.2-10%, preferably 0.5-3%, It is further preferably 1.5-2.5%, more preferably 1.78-2.08%, based on the total weight of the negative active material. Therefore, by adding a carbon coating layer between the graphite and lithium salt coating layers, the instability of the surface after the internal pores of the particles are exposed is further suppressed, and the structural stability of the negative electrode active material is improved, thereby effectively improving the corresponding The first Coulombic efficiency and cycle stability of the battery.
  • the coating layer such as a lithium salt coating layer or a carbon coating layer
  • the coating layer is uniformly or patchyly coated on the outer surface of the graphite particles.
  • the area of the coating layer accounts for more than 80% of the surface area of the particles, preferably more than 90%, and further more than 97%.
  • the coating layer can fill the pores, or it can only cover the surface of the pores.
  • a second aspect of the application provides a method for preparing a negative active material, which includes:
  • the negative active material includes graphite with internal pores and a lithium salt coating layer covering the internal pores and outer surface of the graphite, wherein the weight ratio of the lithium element in the internal pores of the graphite to the lithium element on the outer surface of the graphite is 1 ⁇ 10:1.
  • the method of the present application successively coats the flake graphite and the shaped spherical graphite to obtain a negative active material in which the internal pores and the outer surface of the graphite are coated with lithium salt, in which the surface of the coated flake graphite is shaped. Finally, the internal pore surface of spherical graphite is formed.
  • the resulting negative active material has higher surface stability, thereby effectively improving the first Coulombic efficiency and cycle stability of the corresponding battery.
  • the flake graphite is natural flake graphite, its plane size is about 50-200 ⁇ m, measured according to a scanning electron microscope; its fixed carbon content is 99.5%, measured according to a high-frequency infrared carbon and sulfur analyzer .
  • the negative active material includes all technical features described in the first aspect of the invention.
  • carbon coating or surface treatment is performed between steps (1) and (2) or between steps (3) and (4).
  • steps (1) and (2) or between steps (3) and (4) graphite surface defects and activity of active sites are further suppressed, and the surface stability of the negative active material is improved, thereby effectively improving the first Coulombic efficiency and cycle stability of the corresponding battery.
  • steps (3) and (4) carbon coating or surface treatment is performed.
  • graphite surface defects and activity of active sites are further suppressed, and the surface stability of the negative active material is improved, thereby effectively improving the first Coulombic efficiency and cycle stability of the corresponding battery.
  • the step of carbon coating includes mixing (eg stirring) the material to be coated and the carbonaceous material in a heating device such as a heating furnace at a temperature of 150-300°C for 10-60 minutes, and then The obtained mixture is placed in a sintering device and carbonized under an inert gas atmosphere at a temperature of 900-1500°C and a pressure of 0.05-0.2MPa, optionally normal pressure such as 0.1MPa, for 1-10 hours, preferably 4-6 hours, a carbon-coated material was obtained.
  • the carbonaceous material includes one or more of asphalt, phenolic resin, epoxy resin, sucrose, and glucose, preferably asphalt and phenolic resin.
  • the inert gas includes one or more of nitrogen, argon, helium, etc., preferably nitrogen.
  • the surface treatment includes surface oxidation, wherein the surface oxidation includes soaking the powder in strong oxidant solutions such as nitric acid and hydrogen peroxide for oxidation and high-temperature heat treatment in air and oxygen.
  • strong oxidant solutions such as nitric acid and hydrogen peroxide for oxidation and high-temperature heat treatment in air and oxygen.
  • the lithium-containing raw material includes at least one of lithium carbonate, lithium hydroxide, lithium carboxylate, lithium sulfate, lithium fluoride, and lithium phosphate, optionally Contains at least one of lithium carbonate, lithium acetate, lithium citrate, lithium oxalate, lithium sulfate, lithium fluoride, and lithium phosphate, and optionally further contains at least one of lithium carbonate, lithium acetate, lithium citrate, and lithium fluoride. kind. Therefore, the type of lithium salt in the coating layer is further optimized to improve the surface stability of the negative active material, thereby effectively improving the first Coulombic efficiency and cycle stability of the corresponding battery.
  • step (2) includes: preparing lithium-containing raw materials into corresponding solutions; dispersing the flake graphite in the solution to obtain a mixture; filtering, drying and dispersing the mixture, A solid powder is obtained; the solid powder is sintered at 300-900°C for 0.5-8 hours under a protective atmosphere or vacuum to form a lithium salt coating layer on the surface of the flake graphite.
  • the quality of the flake graphite surface coating layer is further optimized, and the surface stability of the negative active material is improved, thereby effectively improving the first Coulombic efficiency and cycle stability of the corresponding battery.
  • step (2) in the solution of the lithium-containing raw material, the solvent used is water or ethanol; the concentration of the lithium-containing raw material is 10-50% by weight, based on the solution Total weight.
  • the flake graphite is dispersed in the solution by stirring at 500-1200rpm, preferably 600-1000rpm using a stirring and mixing device to obtain a mixture; wherein the weight ratio of flake graphite to lithium-containing raw materials is 1:0.01-0.5 , preferably 1:0.05-0.2.
  • a vacuum filter to filter the mixture at room temperature under a pressure of 0.002-0.05MPa, preferably 0.008-0.012mPa, and dry it in a drying oven at a temperature of 50-150°C, preferably 80-100°C for 3-12 hours, 4 -8 hours, and use an airflow disperser to disperse for 0.5-5 hours, preferably 1-3 hours, to obtain a solid powder; the solid powder is heated at 300-900°C, preferably 400-900°C, under a protective atmosphere or vacuum. Sintering for 0.5-8h, preferably 0.5-5h, forms a lithium salt coating layer on the surface of the flake graphite, and then naturally cools to room temperature.
  • the lithium salt contains The composition of the coating is usually lithium carbonate; when the solid powder is sintered at 750-900°C for 0.5-3h, the lithium salt coating is usually composed of lithium carbonate and lithium oxide. When the sintering temperature is high or long enough, the lithium salt coating may even end up consisting solely of lithium oxide.
  • step (3) the flake graphite obtained in step (2) is shaped to obtain spherical graphite with an average volume particle diameter Dv50 of 5-40 ⁇ m, wherein the average volume particle diameter Dv50 is measured as above narrate.
  • step (3) includes sequentially crushing and shaping the flake graphite obtained in step (2) in an airflow crushing and shaping machine, and dispersing in an airflow dispersing machine for 0.5-5 hours, preferably 1-3 hours, Sieve in a vibrating screening machine to obtain spherical graphite particles with an average volume particle size Dv50 of 5-40 ⁇ m.
  • the surface of the coated flake graphite forms the surface of the internal pores of the spherical particles, and further, the surface lithium salt coating layer of the flake graphite also forms the surface coating of the internal pores of the spherical particles. Cladding. It should be noted that it is not excluded that the surface lithium salt coating layer of the flake graphite will also form a coating layer on a part of the external surface of the spherical particles, and this part of the external surface area of the spherical particles does not account for more than 40% of the surface area of the particles.
  • the spherical graphite is coated with a lithium-containing raw material so that a lithium salt coating layer is formed on the surface of the spherical graphite to obtain the negative active material.
  • lithium-containing raw materials are prepared into corresponding solutions; the spherical graphite is dispersed in the solution to obtain a mixture; the mixture is filtered, dried and dispersed to obtain solid powder; the solid is The powder is sintered at 300-900°C for 0.5-8 hours under a protective atmosphere or vacuum to form a lithium salt coating layer on the surface of the spherical graphite.
  • the lithium-containing raw materials described in step (4) are as described in step (2), and may be the same as or different from those described in step (4). Other technical features required in step (4) are as described in step (2).
  • a third aspect of the present application also provides a secondary battery, characterized in that:
  • the secondary battery thus obtained has improved first Coulombic efficiency and cycle stability.
  • a fourth aspect of the present application provides an electrical device, including a secondary battery selected from the second aspect of the present application.
  • a secondary battery is provided.
  • a secondary battery typically includes a positive electrode plate, a negative electrode plate, an electrolyte and a separator.
  • active ions are inserted and detached back and forth between the positive and negative electrodes.
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • the isolation film is placed between the positive electrode piece and the negative electrode piece. It mainly prevents the positive and negative electrodes from short-circuiting and allows ions to pass through.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector.
  • the positive electrode film layer includes the positive electrode active material of the first aspect of the present application.
  • the positive electrode current collector has two surfaces opposite in its own thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • the metal foil aluminum foil can be used.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer.
  • the composite current collector can be formed by forming a metal material on a polymer material substrate.
  • metal materials include but are not limited to aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.
  • Polymer material substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE) ) etc.
  • the cathode active material may include cathode active materials known in the art for batteries.
  • the cathode active material may include at least one of the following materials: an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and their respective modified compounds.
  • the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials of batteries can also be used. Only one type of these positive electrode active materials may be used alone, or two or more types may be used in combination.
  • lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO 2 ), lithium nickel oxides (such as LiNiO 2 ), lithium manganese oxides (such as LiMnO 2 , LiMn 2 O 4 ), lithium Nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1/3 Co 1/3 Mn 1/3 O 2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (can also be abbreviated to NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (can also be abbreviated to NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (can also be abbreviated to NCM 622 ), LiNi At least one of 0.8 Co 0.1 Mn 0.1 O 2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as Li Li
  • the olivine structure contains Examples of lithium phosphates may include, but are not limited to, lithium iron phosphate (such as LiFePO 4 (also referred to as LFP)), composites of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), lithium manganese phosphate and carbon. At least one of composite materials, lithium iron manganese phosphate, and composite materials of lithium iron manganese phosphate and carbon.
  • the weight ratio of the positive electrode active material in the positive electrode film layer is 80-100% by weight, based on the total weight of the positive electrode film layer count.
  • the positive electrode film layer optionally further includes a binder.
  • the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene At least one of ethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • the weight ratio of the binder in the positive electrode film layer is 0-20% by weight, based on the total weight of the positive electrode film layer.
  • the positive electrode film layer optionally further includes a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the weight ratio of the conductive agent in the positive electrode film layer is 0-20% by weight, based on the total weight of the positive electrode film layer.
  • the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components in a solvent (such as N -methylpyrrolidone), forming a positive electrode slurry, wherein the solid content of the positive electrode slurry is 40-80wt%, the viscosity at room temperature is adjusted to 5000-25000mPa ⁇ s, and the positive electrode slurry is coated on the surface of the positive electrode current collector , dried and cold-pressed by a cold rolling mill to form a positive electrode piece; the unit area density of the positive electrode powder coating is 150-350 mg/m 2 , and the compacted density of the positive electrode piece is 3.0-3.6g/cm 3 , optionally 3.3 -3.5g/cm 3 .
  • the calculation formula of the compacted density is
  • Compaction density coating surface density / (thickness of electrode piece after extrusion - thickness of current collector).
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector.
  • the negative electrode film layer includes the negative electrode active material prepared according to the first aspect of the present invention or according to the second aspect of the present invention.
  • the negative electrode current collector has two opposite surfaces in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • the metal foil copper foil can be used.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base material.
  • the composite current collector can be formed by forming a metal material on a polymer material substrate.
  • metal materials include but are not limited to copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.
  • polymer material substrates include but are not limited to polypropylene (PP), polyethylene terephthalate Glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE) and other base materials.
  • the weight ratio of the negative active material in the negative electrode film layer is 70-100% by weight, based on the total weight of the negative electrode film layer.
  • the negative electrode film layer optionally further includes a binder.
  • the binder can be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), polysodium acrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), poly At least one of methacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • SBR styrene-butadiene rubber
  • PAA polyacrylic acid
  • PAAS polysodium acrylate
  • PAM polyacrylamide
  • PVA polyvinyl alcohol
  • SA sodium alginate
  • PMAA methacrylic acid
  • CMCS carboxymethyl chitosan
  • the negative electrode film layer optionally further includes a conductive agent.
  • the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the weight ratio of the conductive agent in the negative electrode film layer is 0-20% by weight, based on the total weight of the negative electrode film layer.
  • the negative electrode film layer optionally includes other auxiliaries, such as thickeners (such as sodium carboxymethylcellulose (CMC-Na)) and the like.
  • the weight ratio of the other additives in the negative electrode film layer is 0-15% by weight, based on the total weight of the negative electrode film layer.
  • the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative active materials, conductive agents, binders and any other components in a solvent (such as deionized water), forming a negative electrode slurry, wherein the solid content of the negative electrode slurry is 30-70wt%, and the viscosity at room temperature is adjusted to 2000-10000mPa ⁇ s; the obtained negative electrode slurry is coated on the negative electrode current collector, After the drying process and cold pressing, such as against rollers, the negative electrode piece is obtained.
  • the negative electrode powder coating unit area density is 75-220mg/m 2
  • the negative electrode plate compacted density is 1.2-2.0g/m 3 .
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • the type of electrolyte in this application can be selected according to needs.
  • the electrolyte can be liquid, gel, or completely solid.
  • the electrolyte is an electrolyte solution.
  • the electrolyte solution includes electrolyte salts and solvents.
  • the electrolyte salt may be selected from lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), bisfluorosulfonyl Lithium amine (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoromethanesulfonate borate (LiDFOB), lithium difluoromethane borate (LiBOB), lithium difluorophosphate (LiPO 2 F 2 ), lithium difluorodioxalate phosphate (LiDFOP) and lithium tetrafluorooxalate phosphate (LiTFOP).
  • the concentration of the electrolyte salt is usually 0.5-5mol/L.
  • the solvent may be selected from fluoroethylene carbonate (FEC), ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC) ), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), methyl formate (MF), methyl acetate Ester (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB) , one or more of ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and diethyl
  • FEC
  • the electrolyte optionally further includes additives.
  • additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain properties of the battery, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.
  • the secondary battery further includes a separator film.
  • a separator film There is no particular restriction on the type of isolation membrane in this application. Any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be used.
  • the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation film can be a single-layer film or a multi-layer composite film, with no special restrictions. When the isolation film is a multi-layer composite film, the materials of each layer can be the same or different, and there is no particular limitation.
  • the thickness of the isolation film is 6-40 ⁇ m, optionally 12-20 ⁇ m; the porosity is 30-60%, and the pore diameter is 100 nm-1.0 ⁇ m.
  • the positive electrode piece, the negative electrode piece and the separator film can be made into an electrode assembly through a winding process or a lamination process.
  • the secondary battery may include an outer packaging.
  • the outer packaging can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag.
  • the material of the soft bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
  • FIG. 3 shows a square-structured secondary battery 5 as an example.
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity.
  • the housing 51 has an opening communicating with the accommodation cavity, and the cover plate 53 can cover the opening to close the accommodation cavity.
  • the positive electrode piece, the negative electrode piece and the isolation film can be formed into the electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the containing cavity.
  • the electrolyte soaks into the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.
  • secondary batteries can be assembled into battery modules, and the number of secondary batteries contained in the battery module can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery module.
  • the above-mentioned battery modules can also be assembled into a battery pack.
  • the number of battery modules contained in the battery pack can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery pack.
  • a fourth aspect of the present application provides an electrical device, including a secondary battery, a battery module or a battery pack selected from the second aspect of the present application.
  • the secondary battery, battery module, or battery pack may be used as a power source for the electrical device, or may be used as an energy storage unit for the electrical device.
  • the electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, and electric golf carts). , electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited to these.
  • a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.
  • FIG. 5 is an electrical device as an example.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc.
  • a battery pack or battery module can be used.
  • the device may be a mobile phone, a tablet, a laptop, etc.
  • the device is usually required to be thin and light, and a secondary battery can be used as a power source.
  • step (2) Add 10kg of 3wt% lithium acetate aqueous solution to the equipment in step (1) and stir at 1200rpm for 5 hours to completely disperse the flake natural graphite. Then use a vacuum filter to filter under a pressure of 0.01 mPa, dry the filtrate in a drying oven at a temperature of 90°C for 6 hours, and then use an airflow disperser to disperse the obtained solid for 2 hours. Finally, the solid was put into a tube furnace, sintered under nitrogen at 450°C for 5 hours at normal pressure, and then naturally cooled to room temperature to obtain Li 2 CO 3 -coated flake natural graphite.
  • step (3) The Li 2 CO 3- coated flake natural graphite obtained in step (2) is sequentially crushed and shaped in an airflow crushing and shaping machine, dispersed in an airflow dispersing machine for 2 hours, and screened in a vibrating screening machine. points to obtain spherical graphite particles with a Dv50 of 20 ⁇ m.
  • the average volume particle size Dv50 of the negative active material is 17 ⁇ m; its SEM image is shown in Figure 1.
  • Other relevant product parameters are summarized in Table 1.
  • step (2) the amount of lithium acetate solution is 10kg of 8wt% lithium acetate aqueous solution, and in step (4), the amount of lithium acetate solution is 10kg of 1wt% of lithium acetate aqueous solution.
  • step (2) the amount of lithium acetate solution is 10kg of 1wt% lithium acetate aqueous solution
  • the amount of lithium acetate solution is 10kg of 8wt% of lithium acetate aqueous solution.
  • step (3i) surface treatment is performed: soak the spherical graphite particles in 80% hydrogen peroxide aqueous solution for 3 hours, then filter, and then sinter. The furnace was maintained at a temperature of 400°C for 1 hour under an oxygen atmosphere, and then cooled naturally.
  • the lithium content in the negative active material particles can be measured by inductively coupled plasma atomic emission spectrometry (ICP).
  • ICP inductively coupled plasma atomic emission spectrometry
  • the concentrated nitric acid is used as a digestion reagent.
  • the graphene and the internal lithium salt can be completely dissolved using the microwave digestion method.
  • the lithium content obtained by the ICP test is the lithium content in the internal pores.
  • the lithium element content within Li is also obtained at the same time as the total carbon content; from this, the weight ratio of the lithium element in the internal pores of the graphite particles to the lithium element on
  • the negative active material of Preparation Example 1, thickener sodium carboxymethylcellulose, adhesive styrene-butadiene rubber, and conductive agent carbon black were mixed according to a mass ratio of 96:1:1:2, and deionized water was added.
  • the organic solvent is a mixed solution containing ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC), where the volume ratio of EC, EMC and DEC is 20:20:60.
  • EC ethylene carbonate
  • EMC ethyl methyl carbonate
  • DEC diethyl carbonate
  • the concentration of lithium salt is 1mol/L.
  • Stack the positive electrode sheet, isolation film, and negative electrode sheet in order so that the isolation film plays an isolation role between the positive and negative electrode sheets then roll it into a square bare cell, put it into the aluminum-plastic film, and then heat it at 80 After baking at °C to remove water, 10g of the corresponding non-aqueous electrolyte is injected, sealed, and after standing, hot and cold pressing, formation, clamping, volume separation and other processes, a finished battery with a capacity of 4000mAh is obtained.
  • the secondary battery of Examples 2-11 and the secondary battery of Comparative Example 1 are similar to the secondary battery of Example 1, but use the negative active material of the corresponding preparation example.
  • 1C current constant current charging to 3.65V continue constant voltage charging until the charging current is less than 0.05C and then cut off, record the charging capacity C11; pause for 5 minutes; 1C current constant current discharge to 2.5V, record the discharge capacity C12; pause for 5 minutes.
  • the above is the first charge and discharge cycle of the battery, which is repeated until the battery has cycled 300 times, and the discharge capacity C3002 is recorded.
  • the negative active material of the present application can effectively improve the first Coulombic efficiency and cycle stability of the corresponding battery; for example, the first Coulombic efficiency of the corresponding secondary battery can reach more than 89%, 300 The capacity retention rate after lap can reach more than 95%.

Abstract

The present application relates to a negative electrode active material, which comprises graphite particles having internal pores and a lithium salt coating layer coating the internal pores of the graphite particles and particle outer surfaces, wherein the weight ratio of a lithium element in the internal pores of the graphite particles to a lithium element on the graphite particle outer surfaces is 1-10:1. The present application relates to a manufacturing method for the negative electrode active material, a corresponding secondary battery, and an electrical device. The internal pores and particle surfaces of the negative electrode active material are all coated with lithium salts, so that the negative electrode active material has higher structural stability, thereby effectively improving the first coulombic efficiency and the cycling stability of the corresponding battery.

Description

负极活性材料、制法、二次电池和用电装置Negative active material, production method, secondary battery and electrical device 技术领域Technical field
本申请涉及锂电池技术领域，尤其涉及一种负极活性材料、制法、二次电池和用电装置。The present application relates to the technical field of lithium batteries, and in particular to a negative active material, a manufacturing method, a secondary battery and an electrical device.
背景技术Background technique
近年来，随着锂离子电池的应用范围越来越广泛，锂离子电池广泛应用于水力、火力、风力和太阳能电站等储能电源***，以及电动工具、电动自行车、电动摩托车、电动汽车、军事装备、航空航天等多个领域。由于锂离子电池取得了极大的发展，因此对其能量密度、循环性能和安全性能等也提出了更高的要求。锂离子电池在组装完成后，在首次充电过程中负极表面会形成固体电解质界面膜(SEI膜)，直到SEI膜完全包覆在负极表面反应停止，这就是锂离子电池的化成过程。SEI膜的成分为内层无机锂盐，包括Li 2CO 3、Li 2O和LiF，外层成分为有机锂盐，包括烷基酯锂等。 In recent years, as the application range of lithium-ion batteries has become more and more extensive, lithium-ion batteries are widely used in energy storage power systems such as hydraulic, thermal, wind and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, Military equipment, aerospace and other fields. Due to the great development of lithium-ion batteries, higher requirements have been put forward for their energy density, cycle performance and safety performance. After the lithium-ion battery is assembled, a solid electrolyte interface film (SEI film) will be formed on the surface of the negative electrode during the first charging process. The reaction stops until the SEI film completely covers the surface of the negative electrode. This is the formation process of the lithium-ion battery. The components of the SEI film are inorganic lithium salts in the inner layer, including Li 2 CO 3 , Li 2 O, and LiF, and organic lithium salts in the outer layer, including lithium alkyl esters.
SEI膜的形成对电极材料的性能产生至关重要的影响。一方面，SEI膜的形成消耗了部分活性锂，使得首次充放电不可逆容量增加，降低了电极材料的充放电效率；另一方面，SEI膜具有有机溶剂不溶性，在有机电解质溶液中能稳定存在，并且溶剂分子不能通过该层钝化膜，从而能有效防止溶剂分子的共嵌入，避免了因溶剂分子共嵌入对电极材料造成的破坏，因而大大提高了电极的循环性能和使用寿命。因此，寻找改善SEI膜性能的有效途径，一直都是世界电化学界研究的热点。The formation of SEI film has a crucial impact on the performance of electrode materials. On the one hand, the formation of the SEI film consumes part of the active lithium, which increases the irreversible capacity of the first charge and discharge and reduces the charge and discharge efficiency of the electrode material; on the other hand, the SEI film is insoluble in organic solvents and can exist stably in organic electrolyte solutions. Moreover, solvent molecules cannot pass through this passivation film, which can effectively prevent the co-embedding of solvent molecules and avoid the damage to the electrode material caused by the co-embedding of solvent molecules, thus greatly improving the cycle performance and service life of the electrode. Therefore, finding effective ways to improve the performance of SEI membranes has always been a research hotspot in the world's electrochemistry community.
发明内容Contents of the invention
本申请是鉴于上述课题而进行的，其目的在于，提供一种负极活性材料，其内部孔隙和颗粒表面均被锂盐包覆，使得所述负极活性材料具有更高的结构稳定性，从而有效地提高相应的电池的首次库伦效率和循环稳定性。This application was made in view of the above issues, and its purpose is to provide a negative active material whose internal pores and particle surfaces are coated with lithium salts, so that the negative active material has higher structural stability, thereby effectively The first Coulombic efficiency and cycle stability of the corresponding battery are greatly improved.
为了达到上述目的，本申请的第一方面提供了一种负极活性材料，其包含具有内部孔隙的石墨颗粒以及包覆在石墨颗粒内部孔隙和颗粒外表面的锂盐包覆层，其中石墨颗粒内部孔隙中的锂元素与石墨颗粒外表面的锂元素的重量比为1～10:1。In order to achieve the above objects, a first aspect of the present application provides a negative active material, which includes graphite particles with internal pores and a lithium salt coating layer coating the internal pores of the graphite particles and the outer surface of the particles, wherein the interior of the graphite particles The weight ratio of the lithium element in the pores to the lithium element on the outer surface of the graphite particles is 1 to 10:1.
由此，本申请的负极活性材料在其内部孔隙和颗粒表面均包覆锂盐，并达到特定的内部孔隙中的锂元素与石墨颗粒外表面的锂元素的重量比，其中所述包覆层的锂盐成分属于锂离子电化学体系中自发形成的SEI膜成分的一部分，并且包覆层能够抑制活性位点，从而能在相应电池的首次化成形成SEI膜过程中减少活性锂的消耗；由于所述负极活性材料的内部孔隙也进行锂盐包覆，所以能在后续石墨内部孔隙因循环体积发生膨胀收缩而暴露后，保护石墨表面并进一步减少锂盐消耗。因此，所述负极活性材料用于锂离子电池负极时能够有效地提高锂离子电池的首次库伦效率和循环稳定性。Therefore, the negative active material of the present application is coated with lithium salt in both its internal pores and particle surface, and reaches a specific weight ratio of lithium element in the internal pores to lithium element on the outer surface of the graphite particles, wherein the coating layer The lithium salt component is part of the SEI film component formed spontaneously in the lithium ion electrochemical system, and the coating layer can inhibit the active sites, thereby reducing the consumption of active lithium during the first formation of the SEI film of the corresponding battery; due to The internal pores of the negative active material are also coated with lithium salt, so that after the internal pores of the graphite are subsequently exposed due to expansion and contraction of the cycle volume, the graphite surface can be protected and the consumption of lithium salt can be further reduced. Therefore, when the negative active material is used as the negative electrode of a lithium-ion battery, it can effectively improve the first Coulombic efficiency and cycle stability of the lithium-ion battery.
在任意实施方式中，所述锂盐包覆层满足如下特征中的至少一个：In any embodiment, the lithium salt coating layer meets at least one of the following characteristics:
(1)所述锂盐包覆层的含量为0.01％-6％，基于负极活性材料的总重量计；(1) The content of the lithium salt coating layer is 0.01%-6%, based on the total weight of the negative active material;
(2)所述石墨颗粒内部孔隙的锂盐包覆层的厚度为1-20nm，所述石墨颗粒外表面的锂盐包覆层的厚度为1-30nm。由此，通过限定锂盐包覆的上述参数，进一步提高了所述负极活性材料的结构稳定性，从而有效地提高相应的电池的首次库伦效率和循环稳定性。(2) The thickness of the lithium salt coating layer in the internal pores of the graphite particles is 1-20 nm, and the thickness of the lithium salt coating layer on the outer surface of the graphite particles is 1-30 nm. Thus, by defining the above parameters of lithium salt coating, the structural stability of the negative active material is further improved, thereby effectively improving the first Coulombic efficiency and cycle stability of the corresponding battery.
在任意实施方式中，所述负极活性材料满足如下特征中的至少一个：In any embodiment, the negative active material satisfies at least one of the following characteristics:
(1)所述石墨为天然石墨；(1) The graphite is natural graphite;
(2)所述锂盐为无机锂盐，可选地为选自碳酸盐、氧化锂、磷酸锂和氟化锂中的一种或多种。(2) The lithium salt is an inorganic lithium salt, optionally one or more selected from the group consisting of carbonate, lithium oxide, lithium phosphate and lithium fluoride.
由此，通过进一步限定石墨和锂盐的种类，进一步提高了所述负极活性材料的结构稳定性，从而有效地提高相应的电池的首次库伦效率和循环稳定性。Thus, by further limiting the types of graphite and lithium salt, the structural stability of the negative active material is further improved, thereby effectively improving the first Coulombic efficiency and cycle stability of the corresponding battery.
在任意实施方式中，所述负极活性材料的平均体积粒径D v50为10-30μm。 In any embodiment, the average volume particle diameter D v50 of the negative active material is 10-30 μm.
由此，通过进一步负极活性材料的平均体积粒径，进一步提高了所述负极活性材料的结构稳定性，从而有效地提高相应的电池的首次库伦效率和循环稳定性。Thus, by further increasing the average volume particle size of the negative active material, the structural stability of the negative active material is further improved, thereby effectively improving the first Coulombic efficiency and cycle stability of the corresponding battery.
在任意实施方式中，在石墨与锂盐包覆层之间，还存在碳包覆层；可选地，所述碳包覆层的包覆量为0.2-10％，基于负极活性材料的总重量计。由此，通过在石墨与锂盐包覆层之间增加碳包覆层，进一步抑制颗粒内部孔隙暴露后表面的不稳定性，提高了所述负极活性材料的结构稳定性，从而有效地提高相应的电池的首次库伦效率和循环稳定性。In any embodiment, there is also a carbon coating layer between the graphite and the lithium salt coating layer; optionally, the coating amount of the carbon coating layer is 0.2-10%, based on the total amount of the negative active material Weight scale. Therefore, by adding a carbon coating layer between the graphite and lithium salt coating layers, the instability of the surface after the internal pores of the particles are exposed is further suppressed, and the structural stability of the negative electrode active material is improved, thereby effectively improving the corresponding The first Coulombic efficiency and cycle stability of the battery.
本申请的第二方面提供一种制备负极活性材料的方法，其包括：A second aspect of the application provides a method for preparing a negative active material, which includes:
(1)提供鳞片石墨；(1) Provide flake graphite;
(2)使用含锂原料包覆鳞片石墨，使得在鳞片石墨表面形成锂盐包覆层；(2) Use lithium-containing raw materials to coat the flake graphite so that a lithium salt coating layer is formed on the surface of the flake graphite;
(3)对步骤(2)中获得的鳞片石墨进行整形，得到球形石墨；(3) Shape the flake graphite obtained in step (2) to obtain spherical graphite;
(4)使用含锂原料包覆所述球形石墨，使得球形石墨表面形成锂盐包覆层，得到所述负极活性材料；(4) Use lithium-containing raw materials to coat the spherical graphite so that a lithium salt coating layer is formed on the surface of the spherical graphite to obtain the negative active material;
其中所述负极活性材料，其包含具有内部孔隙的石墨以及包覆在石墨内部孔隙和外表面的锂盐包覆层，其中石墨内部孔隙中的锂元素与石墨外表面的锂元素的重量比为1～10:1。The negative active material includes graphite with internal pores and a lithium salt coating layer covering the internal pores and outer surface of the graphite, wherein the weight ratio of the lithium element in the internal pores of the graphite to the lithium element on the outer surface of the graphite is 1～10:1.
由此，本申请的方法通过先后对鳞片石墨以及整形后的球形石墨进行包覆，得到石墨内部孔隙和外表面均被包覆锂盐的负极活性材料，其中包覆的鳞片石墨的表面在整形后形成球形石墨的内部孔隙表面。所得的负极活性材料的表面稳定性更高，从而有效地提高相应的电池的首次库伦效率和循环稳定性。Therefore, the method of the present application successively coats the flake graphite and the shaped spherical graphite to obtain a negative active material in which the internal pores and the outer surface of the graphite are coated with lithium salt, in which the surface of the coated flake graphite is shaped. Finally, the internal pore surface of spherical graphite is formed. The resulting negative active material has higher surface stability, thereby effectively improving the first Coulombic efficiency and cycle stability of the corresponding battery.
在任意实施方式中，在步骤(1)与(2)之间或在步骤(3)与(4)之间，进行碳包覆或表面处理。由此，进一步抑制石墨表面缺陷和活性位点的活性，提高所述负极活性材料的表面稳定性更高，从而有效地提高相应的电池的首次库伦效率和循环稳定性。In any embodiment, carbon coating or surface treatment is performed between steps (1) and (2) or between steps (3) and (4). As a result, graphite surface defects and activity of active sites are further suppressed, and the surface stability of the negative active material is improved, thereby effectively improving the first Coulombic efficiency and cycle stability of the corresponding battery.
在任意实施方式中，在步骤(3)与(4)之间，进行碳包覆或表面处理。由此，进一步抑制石墨表面缺陷和活性位点的活性，提高所述负极活性材料的表面稳定性更高，从而有效地提高相应的电池的首次库伦效率和循环稳定性。In any embodiment, between steps (3) and (4), carbon coating or surface treatment is performed. As a result, graphite surface defects and activity of active sites are further suppressed, and the surface stability of the negative active material is improved, thereby effectively improving the first Coulombic efficiency and cycle stability of the corresponding battery.
在任意实施方式中，在步骤(2)中，所述含锂原料包含碳酸锂、氢氧化锂、锂的羧酸盐、硫酸锂、氟化锂、磷酸锂中的至少一种，可选地包含碳酸锂、乙酸锂、柠檬酸锂、草酸锂、硫酸锂、氟化锂、磷酸锂中的至少一种。由此，进一步优选包覆层的锂盐种类，提高所述负极活性材料的表面稳定性更高，从而有效地提高相应的电池的首次库伦效率和循环稳定性。In any embodiment, in step (2), the lithium-containing raw material includes at least one of lithium carbonate, lithium hydroxide, lithium carboxylate, lithium sulfate, lithium fluoride, and lithium phosphate, optionally Contains at least one of lithium carbonate, lithium acetate, lithium citrate, lithium oxalate, lithium sulfate, lithium fluoride, and lithium phosphate. Therefore, the type of lithium salt in the coating layer is further optimized to improve the surface stability of the negative active material, thereby effectively improving the first Coulombic efficiency and cycle stability of the corresponding battery.
在任意实施方式中，步骤(2)包括：将含锂原料制备成相应的溶液；将所述鳞片石墨分散在所述溶液中，得到混合物；将所述混合物进行过滤、烘干和打散，得到固体粉末；将所述固体粉末在保护气氛或真空下300-900℃烧结0.5-8h，在鳞片石墨表面形成锂盐包覆层。由此，进一步优化鳞片石墨表面包覆层质量，提高所述负极活性材料的表面稳定性更高，从而有效地提高相应的电池的首次库伦效率和循环稳定性。In any embodiment, step (2) includes: preparing lithium-containing raw materials into corresponding solutions; dispersing the flake graphite in the solution to obtain a mixture; filtering, drying and dispersing the mixture, A solid powder is obtained; the solid powder is sintered at 300-900°C for 0.5-8 hours under a protective atmosphere or vacuum to form a lithium salt coating layer on the surface of the flake graphite. As a result, the quality of the flake graphite surface coating layer is further optimized, and the surface stability of the negative active material is improved, thereby effectively improving the first Coulombic efficiency and cycle stability of the corresponding battery.
本申请的第三方面还提供一种二次电池，其特征在于，A third aspect of the present application also provides a secondary battery, characterized in that:
包括本申请的第一方面所述的负极活性材料或根据本申请的第二方面所述的方法制备的负极活性材料。由此获得的二次电池具有改善的首次库伦效率和循环稳定性。It includes the negative active material described in the first aspect of the present application or the negative active material prepared according to the method described in the second aspect of the present application. The secondary battery thus obtained has improved first Coulombic efficiency and cycle stability.
本申请的第四方面提供一种用电装置，包括选自本申请的第二方面的二次电池。A fourth aspect of the present application provides an electrical device, including a secondary battery selected from the second aspect of the present application.
本申请的负极活性材料内部孔隙和颗粒表面均被锂盐包覆，使得所述负极活性材料具有更高的结构稳定性，从而有效地提高了相应的电池的首次库伦效率和循环稳定性。The internal pores and particle surfaces of the negative active material of the present application are coated with lithium salts, so that the negative active material has higher structural stability, thereby effectively improving the first Coulombic efficiency and cycle stability of the corresponding battery.
附图说明Description of drawings
图1为本申请的实施例1的负极活性材料被包覆的天然石墨的切面的SEM图；Figure 1 is an SEM image of a cross-section of natural graphite coated with the negative active material in Example 1 of the present application;
图2为现有的人造石墨的切面的SEM图Figure 2 is an SEM image of a cross section of existing artificial graphite.
图3是本申请一实施方式的二次电池的示意图。FIG. 3 is a schematic diagram of a secondary battery according to an embodiment of the present application.
图4是图1所示的本申请一实施方式的二次电池的分解图。FIG. 4 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 1 .
图5是本申请一实施方式的二次电池用作电源的用电装置的示意图。FIG. 5 is a schematic diagram of a power consumption device using a secondary battery as a power source according to an embodiment of the present application.
附图标记说明：Explanation of reference symbols:
5、二次电池；51、壳体；52、电极组件；53、盖板；6、用电装置。5. Secondary battery; 51. Housing; 52. Electrode assembly; 53. Cover plate; 6. Electrical device.
具体实施方式Detailed ways
以下，适当地参照附图详细说明具体公开了本申请的负极活性材料、其制备方法、二次电池和用电装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。Hereinafter, embodiments specifically disclosing the negative electrode active material of the present application, its preparation method, secondary battery, and power consumption device will be described in detail with reference to the accompanying drawings as appropriate. However, unnecessary detailed explanations may be omitted. For example, detailed descriptions of well-known matters may be omitted, or descriptions of substantially the same structure may be repeated. This is to prevent the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application, and are not intended to limit the subject matter described in the claims.
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的 任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。"Ranges" disclosed herein are defined in terms of lower and upper limits. A given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive of the endpoints, and may be arbitrarily combined, that is, any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, understand that ranges of 60-110 and 80-120 are also expected. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-5. In this application, unless otherwise stated, the numerical range "a-b" represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed in this article, and "0-5" is just an abbreviation of these numerical combinations. In addition, when stating that a certain parameter is an integer ≥ 2, it is equivalent to disclosing that the parameter is an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。If there is no special description, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。If there is no special description, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions.
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。If there is no special instructions, all steps of the present application can be performed sequentially or randomly, and are preferably performed sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, mentioning that the method may also include step (c) means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c). , may also include steps (a), (c) and (b), may also include steps (c), (a) and (b), etc.
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。If there is no special explanation, the words "include" and "include" mentioned in this application represent open expressions, which may also be closed expressions. For example, "comprising" and "comprising" may mean that other components not listed may also be included or included, or only the listed components may be included or included.
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。In this application, the term "or" is inclusive unless otherwise specified. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists) ; Or both A and B are true (or exist).
锂离子电池在组装完成后，在首次充电过程中负极表面会形成固体电解质界面膜(SEI膜)，直到SEI膜完全包覆在负极表面反应停止，这就是锂离子电池的化成过程。SEI膜的成分为内层无机锂盐，包括Li 2CO 3、Li 2O和LiF，外层成分为有机锂盐，包括烷基酯锂等。SEI膜的形成对电极材料的性能产生至关重要的影响。一方面，SEI膜的形成消耗了部分活性锂，使得首次充放电不可逆容量增加，降低了电极材料的充放电效率；另一方面，SEI膜具有有机溶剂不溶性，在有机电解质溶液中能稳定存在，并且溶剂分子不能通过该层钝化膜，从而能有效防止溶剂分子的共嵌入，避免了因溶剂分子共嵌入对电极材料造成的破坏，因而大大提高了电极的循环性能和使用寿命。因此，寻找改善SEI膜性能的有效途径，一直都是世界电化学界研究的热点。发明人研究发 现本发明的第一方面的负极活性材料通过预先在其内部孔隙和颗粒表面均包覆构成SEI膜一部分的锂盐并达到特定的内部孔隙中的锂元素与石墨颗粒外表面的锂元素的重量比，使得在相应电池的首次化成形成SEI膜过程中活性锂的消耗减少；由于所述负极活性材料的内部孔隙也进行锂盐包覆，所以能在后续石墨内部孔隙因循环体积发生膨胀收缩而暴露后，保护石墨表面并进一步减少锂盐消耗。因此，所述负极活性材料用于锂离子电池负极时能够有效地提高锂离子电池的首次库伦效率和循环稳定性。 After the lithium-ion battery is assembled, a solid electrolyte interface film (SEI film) will be formed on the surface of the negative electrode during the first charging process. The reaction stops until the SEI film completely covers the surface of the negative electrode. This is the formation process of the lithium-ion battery. The components of the SEI film are inorganic lithium salts in the inner layer, including Li 2 CO 3 , Li 2 O, and LiF, and organic lithium salts in the outer layer, including lithium alkyl esters. The formation of SEI film has a crucial impact on the performance of electrode materials. On the one hand, the formation of the SEI film consumes part of the active lithium, which increases the irreversible capacity of the first charge and discharge and reduces the charge and discharge efficiency of the electrode material; on the other hand, the SEI film is insoluble in organic solvents and can exist stably in organic electrolyte solutions. Moreover, solvent molecules cannot pass through this passivation film, which can effectively prevent the co-embedding of solvent molecules and avoid the damage to the electrode material caused by the co-embedding of solvent molecules, thus greatly improving the cycle performance and service life of the electrode. Therefore, finding effective ways to improve the performance of SEI membranes has always been a research hotspot in the world's electrochemistry community. The inventor found through research that the negative active material of the first aspect of the present invention is pre-coated with lithium salts that constitute a part of the SEI film on both its internal pores and particle surfaces, and achieves a specific lithium element in the internal pores and lithium on the outer surface of the graphite particles. The weight ratio of the elements reduces the consumption of active lithium during the first formation of the SEI film of the corresponding battery; since the internal pores of the negative active material are also coated with lithium salts, subsequent internal pores of graphite can be generated due to cycle volume. After being exposed due to expansion and contraction, the graphite surface is protected and further reduces lithium salt consumption. Therefore, when the negative active material is used as the negative electrode of a lithium-ion battery, it can effectively improve the first Coulombic efficiency and cycle stability of the lithium-ion battery.
负极活性材料Negative active material
在一些实施方式中，本申请的第一方面提供了一种负极活性材料，其包含具有内部孔隙的石墨颗粒以及包覆在石墨颗粒内部孔隙和颗粒外表面的锂盐包覆层，其中石墨颗粒内部孔隙中的锂元素与石墨颗粒外表面的锂元素的重量比为1～10:1，优选1～5:1，进一步优选2～3:1。In some embodiments, the first aspect of the present application provides a negative active material, which includes graphite particles having internal pores and a lithium salt coating layer coating the internal pores of the graphite particles and the outer surface of the particles, wherein the graphite particles The weight ratio of the lithium element in the internal pores to the lithium element on the outer surface of the graphite particles is 1 to 10:1, preferably 1 to 5:1, and more preferably 2 to 3:1.
由此，本申请的负极活性材料在其内部孔隙和颗粒表面均包覆锂盐，并达到特定的内部孔隙中的锂元素与石墨颗粒外表面的锂元素的重量比，其中所述包覆层的锂盐成分属于锂离子电化学体系中自发形成的SEI膜成分的一部分，并且包覆层能够抑制活性位点，从而能在相应电池的首次化成形成SEI膜过程中减少活性锂的消耗；由于所述负极活性材料的内部孔隙也进行锂盐包覆，所以能在后续石墨内部孔隙因循环体积发生膨胀收缩而暴露后，保护石墨表面并进一步减少锂盐消耗。因此，所述负极活性材料用于锂离子电池负极时能够有效地提高锂离子电池的首次库伦效率和循环稳定性。Therefore, the negative active material of the present application is coated with lithium salt in both its internal pores and particle surface, and reaches a specific weight ratio of lithium element in the internal pores to lithium element on the outer surface of the graphite particles, wherein the coating layer The lithium salt component is part of the SEI film component formed spontaneously in the lithium ion electrochemical system, and the coating layer can inhibit the active sites, thereby reducing the consumption of active lithium during the first formation of the SEI film of the corresponding battery; due to The internal pores of the negative active material are also coated with lithium salt, so that after the internal pores of the graphite are subsequently exposed due to expansion and contraction of the cycle volume, the graphite surface can be protected and the consumption of lithium salt can be further reduced. Therefore, when the negative active material is used as the negative electrode of a lithium-ion battery, it can effectively improve the first Coulombic efficiency and cycle stability of the lithium-ion battery.
所述术语“内部孔隙”包括石墨颗粒内部的与外界空气联通或不连通的孔或缝隙，参见图1。所述内部孔隙的锂盐包覆层通过先对鳞片石墨的表面进行锂盐包覆，然后整形使得鳞片石墨的表面的锂盐包覆层形成球形石墨的内部孔隙表面的锂盐包覆层来得到。The term "internal pores" includes pores or gaps inside graphite particles that are connected or disconnected from the outside air, see Figure 1 . The lithium salt coating layer of the internal pores is obtained by first coating the surface of the flake graphite with lithium salt, and then shaping the lithium salt coating layer on the surface of the flake graphite to form the lithium salt coating layer on the surface of the internal pores of the spherical graphite. get.
在一些实施方式中，所述锂盐包覆层的含量为0.01％-6％，优选1％-5.2％，更优选2.7-5.15％，基于负极活性材料的总重量计。In some embodiments, the content of the lithium salt coating layer is 0.01%-6%, preferably 1%-5.2%, more preferably 2.7-5.15%, based on the total weight of the negative active material.
在一些实施方式中，所述石墨颗粒内部孔隙的锂盐包覆层的厚度为1-20nm，优选2-25nm、进一步优选5-12nm；所述石墨颗粒外表面的锂盐包覆层的厚度为1-30nm，优选2-25nm、进一步优选5-12nm。由此，通过限定锂盐包覆的上述参数，进一步提高了所述负极活性材料的结构稳定性，从而有效地提高相应的电池的首次库伦效率和循环稳定性。In some embodiments, the thickness of the lithium salt coating layer in the internal pores of the graphite particles is 1-20 nm, preferably 2-25 nm, and further preferably 5-12 nm; the thickness of the lithium salt coating layer on the outer surface of the graphite particles is It is 1-30nm, preferably 2-25nm, further preferably 5-12nm. Thus, by defining the above parameters of lithium salt coating, the structural stability of the negative active material is further improved, thereby effectively improving the first Coulombic efficiency and cycle stability of the corresponding battery.
在一些实施方式中，所述石墨颗粒内部孔隙的表面至少70％、优选90％、进一步优选95％，更进一步优选98％以及最优选100％被锂盐包覆层包覆，基于石墨颗粒内部全部孔隙的表面积计。In some embodiments, at least 70%, preferably 90%, further preferably 95%, further preferably 98% and most preferably 100% of the surface of the internal pores of the graphite particles are covered by a lithium salt coating layer, based on the interior of the graphite particles. Surface area of all pores.
在一些实施方式中，所述石墨为天然石墨，其比表面积为2～15m 2/g。所述锂盐为无机锂盐，可选地为选自碳酸盐、氧化锂、磷酸锂和氟化锂中的一种或多种，进一步可选为选自碳酸锂、氧化锂和氟化锂中的一种或多种。所述无机锂盐通常优选为锂电池自发形成的SEI膜中的成分或者与自发形成的SEI膜起到相同作用的成分，即其能够传导锂离子，不会传导电子。所述天然石墨比表面积大，表面活性位点多，在首次形成SEI膜过程中会消耗更多的活性锂。本申请的天然石墨内部孔隙和外部表面都具有锂盐包覆层的负极活性材料在应用于锂离子电池时既能在首次化成过程中减少活性锂的消耗，又能在后续天然石墨内部孔隙因循环体积发生膨胀收缩而暴露后，保护天然石墨表面并进一步减少锂盐消耗；由此，进一步提高了所述负极活性材料的结构稳定性，从而有效地提高相应的电池的首次库伦效率和循环稳定性。 In some embodiments, the graphite is natural graphite, and its specific surface area is 2 to 15 m 2 /g. The lithium salt is an inorganic lithium salt, optionally one or more selected from the group consisting of carbonate, lithium oxide, lithium phosphate and lithium fluoride, further optionally selected from the group consisting of lithium carbonate, lithium oxide and fluoride. One or more types of lithium. The inorganic lithium salt is usually preferably a component in the SEI film formed spontaneously in a lithium battery or a component that plays the same role as the SEI film formed spontaneously, that is, it can conduct lithium ions but cannot conduct electrons. The natural graphite has a large specific surface area and many surface active sites, and will consume more active lithium during the first formation of the SEI film. When the negative active material of the present application of natural graphite with a lithium salt coating layer on both the internal pores and the external surface is used in a lithium-ion battery, it can not only reduce the consumption of active lithium during the first formation process, but also reduce the subsequent internal pores of the natural graphite due to the After the cycle volume expands and contracts and is exposed, the surface of the natural graphite is protected and the consumption of lithium salt is further reduced; thus, the structural stability of the negative active material is further improved, thereby effectively improving the first Coulombic efficiency and cycle stability of the corresponding battery. sex.
在一些实施方式中，所述负极活性材料的平均体积粒径D v50为10-30μm，优选14-18μm。平均体积粒径Dv50为样品的体积累计分布百分数达到50％时对应的粒径；其是以采用激光粒度分析仪例如英国马尔文仪器有限公司的Mastersizer 3000型激光粒度分析仪测定。 In some embodiments, the average volume particle diameter D v50 of the negative active material is 10-30 μm, preferably 14-18 μm. The average volume particle size Dv50 is the particle size corresponding to when the cumulative volume distribution percentage of the sample reaches 50%; it is measured using a laser particle size analyzer such as the Mastersizer 3000 laser particle size analyzer of Malvern Instruments Co., Ltd. in the UK.
由此，通过进一步负极活性材料的平均体积粒径，进一步提高了所述负极活性材料的结构稳定性，从而有效地提高相应的电池的首次库伦效率和循环稳定性。Thus, by further increasing the average volume particle size of the negative active material, the structural stability of the negative active material is further improved, thereby effectively improving the first Coulombic efficiency and cycle stability of the corresponding battery.
在一些实施方式中，在石墨与锂盐包覆层之间，还存在碳包覆层；可选地，所述碳包覆层的包覆量为0.2-10％，优选0.5-3％，进一步优选1.5-2.5％，更优选1.78-2.08％，基于负极活性材料的总重量计。由此，通过在石墨与锂盐包覆层之间增加碳包覆层，进一步抑制颗粒内部孔隙暴露后表面的不稳定性，提高了所述负极活性材料的结构稳定性，从而有效地提高相应的电池的首次库伦效率和循环稳定性。In some embodiments, there is a carbon coating layer between the graphite and the lithium salt coating layer; optionally, the coating amount of the carbon coating layer is 0.2-10%, preferably 0.5-3%, It is further preferably 1.5-2.5%, more preferably 1.78-2.08%, based on the total weight of the negative active material. Therefore, by adding a carbon coating layer between the graphite and lithium salt coating layers, the instability of the surface after the internal pores of the particles are exposed is further suppressed, and the structural stability of the negative electrode active material is improved, thereby effectively improving the corresponding The first Coulombic efficiency and cycle stability of the battery.
在一些优选的实施方式中，对于石墨颗粒外表面的包覆层，所述包覆层，例如锂盐包覆层或碳包覆层，均匀地或者呈斑块状包覆在石墨颗粒外表面。当包覆层呈斑块状包覆在石墨颗粒外部表面时，包覆层面积占颗粒表面积的80％以上，优选90％以上，进一步97％以上。In some preferred embodiments, for the coating layer on the outer surface of the graphite particles, the coating layer, such as a lithium salt coating layer or a carbon coating layer, is uniformly or patchyly coated on the outer surface of the graphite particles. . When the coating layer is coated on the outer surface of the graphite particles in patchy form, the area of the coating layer accounts for more than 80% of the surface area of the particles, preferably more than 90%, and further more than 97%.
在一些优选的实施方式中，对于石墨颗粒内部孔隙的包覆层，其包覆层可以填满 孔隙，也可以仅包覆孔隙表面。In some preferred embodiments, for the coating layer of the internal pores of the graphite particles, the coating layer can fill the pores, or it can only cover the surface of the pores.
本申请的第二方面提供一种制备负极活性材料的方法，其包括：A second aspect of the application provides a method for preparing a negative active material, which includes:
(1)提供鳞片石墨；(1) Provide flake graphite;
(2)使用含锂原料包覆鳞片石墨，使得在鳞片石墨表面形成锂盐包覆层；(2) Use lithium-containing raw materials to coat the flake graphite so that a lithium salt coating layer is formed on the surface of the flake graphite;
(3)对步骤(2)中获得的鳞片石墨进行整形，得到球形石墨；(3) Shape the flake graphite obtained in step (2) to obtain spherical graphite;
(4)使用含锂原料包覆所述球形石墨，使得球形石墨表面形成锂盐包覆层，得到所述负极活性材料；(4) Use lithium-containing raw materials to coat the spherical graphite so that a lithium salt coating layer is formed on the surface of the spherical graphite to obtain the negative active material;
其中所述负极活性材料，其包含具有内部孔隙的石墨以及包覆在石墨内部孔隙和外表面的锂盐包覆层，其中石墨内部孔隙中的锂元素与石墨外表面的锂元素的重量比为1～10:1。The negative active material includes graphite with internal pores and a lithium salt coating layer covering the internal pores and outer surface of the graphite, wherein the weight ratio of the lithium element in the internal pores of the graphite to the lithium element on the outer surface of the graphite is 1～10:1.
由此，本申请的方法通过先后对鳞片石墨以及整形后的球形石墨进行包覆，得到石墨内部孔隙和外表面均被包覆锂盐的负极活性材料，其中包覆的鳞片石墨的表面在整形后形成球形石墨的内部孔隙表面。所得的负极活性材料的表面稳定性更高，从而有效地提高相应的电池的首次库伦效率和循环稳定性。Therefore, the method of the present application successively coats the flake graphite and the shaped spherical graphite to obtain a negative active material in which the internal pores and the outer surface of the graphite are coated with lithium salt, in which the surface of the coated flake graphite is shaped. Finally, the internal pore surface of spherical graphite is formed. The resulting negative active material has higher surface stability, thereby effectively improving the first Coulombic efficiency and cycle stability of the corresponding battery.
在一些优选的实施方式中，所述鳞片石墨为天然鳞片石墨，其平面尺寸约为50-200μm，根据扫描电子显微镜测量；其固定碳含量为99.5％，根据高频红外碳硫分析仪进行测定。In some preferred embodiments, the flake graphite is natural flake graphite, its plane size is about 50-200 μm, measured according to a scanning electron microscope; its fixed carbon content is 99.5%, measured according to a high-frequency infrared carbon and sulfur analyzer .
所述负极活性材料包括本发明的第一方面中所述的所有技术特征。The negative active material includes all technical features described in the first aspect of the invention.
在一些实施方式中，在步骤(1)与(2)之间或在步骤(3)与(4)之间，进行碳包覆或表面处理。由此，进一步抑制石墨表面缺陷和活性位点的活性，提高所述负极活性材料的表面稳定性更高，从而有效地提高相应的电池的首次库伦效率和循环稳定性。In some embodiments, carbon coating or surface treatment is performed between steps (1) and (2) or between steps (3) and (4). As a result, graphite surface defects and activity of active sites are further suppressed, and the surface stability of the negative active material is improved, thereby effectively improving the first Coulombic efficiency and cycle stability of the corresponding battery.
在一些实施方式中，在步骤(3)与(4)之间，进行碳包覆或表面处理。由此，进一步抑制石墨表面缺陷和活性位点的活性，提高所述负极活性材料的表面稳定性更高，从而有效地提高相应的电池的首次库伦效率和循环稳定性。In some embodiments, between steps (3) and (4), carbon coating or surface treatment is performed. As a result, graphite surface defects and activity of active sites are further suppressed, and the surface stability of the negative active material is improved, thereby effectively improving the first Coulombic efficiency and cycle stability of the corresponding battery.
在一些实施方式中，所述碳包覆的步骤包括将待包覆的材料与含碳材料在加热设备例如加热炉中在150-300℃温度下进行混合(例如搅拌)10-60min，然后将得到的混合物置于烧结设备中在900-1500℃的温度下在0.05-0.2MPa，可选地为常压例如0.1MPa的压力下在惰性气体气氛下碳化1-10小时，优选为4-6小时，得到碳包覆的材料。其 中所述含碳材料包括沥青、酚醛树脂、环氧树脂、蔗糖、葡萄糖中的一种或多种，优选沥青、酚醛树脂。所述惰性气体包括氮气、氩气、氦气等的一种或多种，优选氮气。In some embodiments, the step of carbon coating includes mixing (eg stirring) the material to be coated and the carbonaceous material in a heating device such as a heating furnace at a temperature of 150-300°C for 10-60 minutes, and then The obtained mixture is placed in a sintering device and carbonized under an inert gas atmosphere at a temperature of 900-1500°C and a pressure of 0.05-0.2MPa, optionally normal pressure such as 0.1MPa, for 1-10 hours, preferably 4-6 hours, a carbon-coated material was obtained. The carbonaceous material includes one or more of asphalt, phenolic resin, epoxy resin, sucrose, and glucose, preferably asphalt and phenolic resin. The inert gas includes one or more of nitrogen, argon, helium, etc., preferably nitrogen.
在一些实施方式中，所述表面处理包括表面氧化，其中表面氧化包括将粉料浸泡于硝酸、过氧化氢等强氧化剂溶液进行氧化和在空气、氧气下高温热处理。In some embodiments, the surface treatment includes surface oxidation, wherein the surface oxidation includes soaking the powder in strong oxidant solutions such as nitric acid and hydrogen peroxide for oxidation and high-temperature heat treatment in air and oxygen.
在一些实施方式中，在步骤(2)中，所述含锂原料包含碳酸锂、氢氧化锂、锂的羧酸盐、硫酸锂、氟化锂、磷酸锂中的至少一种，可选地包含碳酸锂、乙酸锂、柠檬酸锂、草酸锂、硫酸锂、氟化锂、磷酸锂中的至少一种，进一步可选包含碳酸锂、乙酸锂、柠檬酸锂、氟化锂中的至少一种。由此，进一步优选包覆层的锂盐种类，提高所述负极活性材料的表面稳定性更高，从而有效地提高相应的电池的首次库伦效率和循环稳定性。In some embodiments, in step (2), the lithium-containing raw material includes at least one of lithium carbonate, lithium hydroxide, lithium carboxylate, lithium sulfate, lithium fluoride, and lithium phosphate, optionally Contains at least one of lithium carbonate, lithium acetate, lithium citrate, lithium oxalate, lithium sulfate, lithium fluoride, and lithium phosphate, and optionally further contains at least one of lithium carbonate, lithium acetate, lithium citrate, and lithium fluoride. kind. Therefore, the type of lithium salt in the coating layer is further optimized to improve the surface stability of the negative active material, thereby effectively improving the first Coulombic efficiency and cycle stability of the corresponding battery.
在一些实施方式中，步骤(2)包括：将含锂原料制备成相应的溶液；将所述鳞片石墨分散在所述溶液中，得到混合物；将所述混合物进行过滤、烘干和打散，得到固体粉末；将所述固体粉末在保护气氛或真空下300-900℃烧结0.5-8h，在鳞片石墨表面形成锂盐包覆层。由此，进一步优化鳞片石墨表面包覆层质量，提高所述负极活性材料的表面稳定性更高，从而有效地提高相应的电池的首次库伦效率和循环稳定性。In some embodiments, step (2) includes: preparing lithium-containing raw materials into corresponding solutions; dispersing the flake graphite in the solution to obtain a mixture; filtering, drying and dispersing the mixture, A solid powder is obtained; the solid powder is sintered at 300-900°C for 0.5-8 hours under a protective atmosphere or vacuum to form a lithium salt coating layer on the surface of the flake graphite. As a result, the quality of the flake graphite surface coating layer is further optimized, and the surface stability of the negative active material is improved, thereby effectively improving the first Coulombic efficiency and cycle stability of the corresponding battery.
在一些优选的实施方式中，在步骤(2)中，在所述含锂原料的溶液中，所用的溶剂为水或乙醇；含锂原料的浓度为10-50重量％，基于所述溶液的总重量计。将所述鳞片石墨利用搅拌混合装置通过在500-1200rpm、优选600-1000rpm转速下的搅拌来分散在所述溶液中，得到混合物；其中鳞片石墨与含锂原料的重量比为1:0.01-0.5，优选1：0.05-0.2。将所述混合物使用真空抽滤机在室温在0.002-0.05MPa，优选0.008-0.012mPa压力下过滤，用干燥箱在50-150℃、优选80-100℃温度下烘干3-12小时、4-8小时，并利用气流式打散机打散0.5-5小时、优选1-3小时，得到固体粉末；将所述固体粉末在保护气氛或真空下300-900℃、优选400-900℃下烧结0.5-8h，优选0.5-5h，在鳞片石墨表面形成锂盐包覆层，然后自然冷却至室温。In some preferred embodiments, in step (2), in the solution of the lithium-containing raw material, the solvent used is water or ethanol; the concentration of the lithium-containing raw material is 10-50% by weight, based on the solution Total weight. The flake graphite is dispersed in the solution by stirring at 500-1200rpm, preferably 600-1000rpm using a stirring and mixing device to obtain a mixture; wherein the weight ratio of flake graphite to lithium-containing raw materials is 1:0.01-0.5 , preferably 1:0.05-0.2. Use a vacuum filter to filter the mixture at room temperature under a pressure of 0.002-0.05MPa, preferably 0.008-0.012mPa, and dry it in a drying oven at a temperature of 50-150°C, preferably 80-100°C for 3-12 hours, 4 -8 hours, and use an airflow disperser to disperse for 0.5-5 hours, preferably 1-3 hours, to obtain a solid powder; the solid powder is heated at 300-900°C, preferably 400-900°C, under a protective atmosphere or vacuum. Sintering for 0.5-8h, preferably 0.5-5h, forms a lithium salt coating layer on the surface of the flake graphite, and then naturally cools to room temperature.
在一些优选的实施方式中，在步骤(2)中，对于碳酸锂、锂的羧酸盐作为含锂原料，当将所述固体粉末在300-750℃下烧结3-8h时，锂盐包覆层的组成通常为碳酸锂；当将所述固体粉末在750-900℃下烧结0.5-3h时，锂盐包覆层通常由碳酸锂和氧化锂组成。当烧结温度足够高或长时，锂盐包覆层最终甚至可能仅由氧化锂组成。In some preferred embodiments, in step (2), for lithium carbonate and lithium carboxylate as lithium-containing raw materials, when the solid powder is sintered at 300-750°C for 3-8 hours, the lithium salt contains The composition of the coating is usually lithium carbonate; when the solid powder is sintered at 750-900°C for 0.5-3h, the lithium salt coating is usually composed of lithium carbonate and lithium oxide. When the sintering temperature is high or long enough, the lithium salt coating may even end up consisting solely of lithium oxide.
在一些实施方式中，在步骤(3)中，对步骤(2)中获得的鳞片石墨进行整形， 得到平均体积粒径Dv50为5-40μm的球形石墨，其中平均体积粒径Dv50测量方法如上所述。具体而言，步骤(3)包括将步骤(2)中获得的鳞片石墨依次在气流式粉碎整形机中粉碎和整形，在气流式打散机打散0.5-5小时、优选1-3小时，在振动筛分机中筛分，得到平均体积粒径Dv50为5-40μm的球形石墨颗粒。在该步骤中，所述被包覆的鳞片石墨的表面形成了所述球形颗粒的内部孔隙的表面，进而，鳞片石墨的表面锂盐包覆层也形成所述球形颗粒的内部孔隙的表面包覆层。应当注意，不排除鳞片石墨的表面锂盐包覆层也会形成球形颗粒的外部表面的一部分的包覆层，球形颗粒的这部分外部表面积占比不超过颗粒表面积的40％。In some embodiments, in step (3), the flake graphite obtained in step (2) is shaped to obtain spherical graphite with an average volume particle diameter Dv50 of 5-40 μm, wherein the average volume particle diameter Dv50 is measured as above narrate. Specifically, step (3) includes sequentially crushing and shaping the flake graphite obtained in step (2) in an airflow crushing and shaping machine, and dispersing in an airflow dispersing machine for 0.5-5 hours, preferably 1-3 hours, Sieve in a vibrating screening machine to obtain spherical graphite particles with an average volume particle size Dv50 of 5-40 μm. In this step, the surface of the coated flake graphite forms the surface of the internal pores of the spherical particles, and further, the surface lithium salt coating layer of the flake graphite also forms the surface coating of the internal pores of the spherical particles. Cladding. It should be noted that it is not excluded that the surface lithium salt coating layer of the flake graphite will also form a coating layer on a part of the external surface of the spherical particles, and this part of the external surface area of the spherical particles does not account for more than 40% of the surface area of the particles.
在一些实施方式中，在步骤(4)中，使用含锂原料包覆所述球形石墨，使得球形石墨表面形成锂盐包覆层，得到所述负极活性材料。具体而言，将含锂原料制备成相应的溶液；将所述球形石墨分散在所述溶液中，得到混合物；将所述混合物进行过滤、烘干和打散，得到固体粉末；将所述固体粉末在保护气氛或真空下300-900℃烧结0.5-8h，在球形石墨表面形成锂盐包覆层。其中步骤(4)中所述含锂原料如步骤(2)中所述，可与步骤(4)中所述的相同或不同。步骤(4)的所需其他技术特征如步骤(2)中所述。In some embodiments, in step (4), the spherical graphite is coated with a lithium-containing raw material so that a lithium salt coating layer is formed on the surface of the spherical graphite to obtain the negative active material. Specifically, lithium-containing raw materials are prepared into corresponding solutions; the spherical graphite is dispersed in the solution to obtain a mixture; the mixture is filtered, dried and dispersed to obtain solid powder; the solid is The powder is sintered at 300-900°C for 0.5-8 hours under a protective atmosphere or vacuum to form a lithium salt coating layer on the surface of the spherical graphite. The lithium-containing raw materials described in step (4) are as described in step (2), and may be the same as or different from those described in step (4). Other technical features required in step (4) are as described in step (2).
本申请的第三方面还提供一种二次电池，其特征在于，A third aspect of the present application also provides a secondary battery, characterized in that:
包括本申请的第一方面所述的负极活性材料或根据本申请的第二方面所述的方法制备的负极活性材料。由此获得的二次电池具有改善的首次库伦效率和循环稳定性。It includes the negative active material described in the first aspect of the application or the negative active material prepared according to the method described in the second aspect of the application. The secondary battery thus obtained has improved first Coulombic efficiency and cycle stability.
本申请的第四方面提供一种用电装置，包括选自本申请的第二方面的二次电池。A fourth aspect of the present application provides an electrical device, including a secondary battery selected from the second aspect of the present application.
以下适当参照附图对本申请的二次电池和用电装置进行说明。The secondary battery and electric device of the present application will be described below with appropriate reference to the drawings.
本申请的一个实施方式中，提供一种二次电池。In one embodiment of the present application, a secondary battery is provided.
通常情况下，二次电池包括正极极片、负极极片、电解质和隔离膜。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。电解质在正极极片和负极极片之间起到传导离子的作用。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使离子通过。Typically, a secondary battery includes a positive electrode plate, a negative electrode plate, an electrolyte and a separator. During the charging and discharging process of the battery, active ions are inserted and detached back and forth between the positive and negative electrodes. The electrolyte plays a role in conducting ions between the positive and negative electrodes. The isolation film is placed between the positive electrode piece and the negative electrode piece. It mainly prevents the positive and negative electrodes from short-circuiting and allows ions to pass through.
正极极片Positive electrode piece
正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，所述正极膜层包括本申请第一方面的正极活性材料。The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector. The positive electrode film layer includes the positive electrode active material of the first aspect of the present application.
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜层设置在 正极集流体相对的两个表面的其中任意一者或两者上。As an example, the positive electrode current collector has two surfaces opposite in its own thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
在一些实施方式中，所述正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料形成在高分子材料基材上而形成。其中，金属材料包括但不限于铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等。高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil can be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material on a polymer material substrate. Among them, metal materials include but are not limited to aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc. Polymer material substrates (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE) ) etc.)
在一些实施方式中，正极活性材料可包含本领域公知的用于电池的正极活性材料。作为示例，正极活性材料可包括以下材料中的至少一种：橄榄石结构的含锂磷酸盐、锂过渡金属氧化物及其各自的改性化合物。但本申请并不限定于这些材料，还可以使用其他可被用作电池正极活性材料的传统材料。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。其中，锂过渡金属氧化物的示例可包括但不限于锂钴氧化物(如LiCoO 2)、锂镍氧化物(如LiNiO 2)、锂锰氧化物(如LiMnO 2、LiMn 2O 4)、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物(如LiNi 1/3Co 1/3Mn 1/3O 2(也可以简称为NCM 333)、LiNi 0.5Co 0.2Mn 0.3O 2(也可以简称为NCM 523)、LiNi 0.5Co 0.25Mn 0.25O 2(也可以简称为NCM 211)、LiNi 0.6Co 0.2Mn 0.2O 2(也可以简称为NCM 622)、LiNi 0.8Co 0.1Mn 0.1O 2(也可以简称为NCM 811)、锂镍钴铝氧化物(如LiNi 0.85Co 0.15Al 0.05O 2)及其改性化合物等中的至少一种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂(如LiFePO 4(也可以简称为LFP))、磷酸铁锂与碳的复合材料、磷酸锰锂(如LiMnPO 4)、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料中的至少一种。所述正极活性材料在正极膜层中的重量比为80-100重量％，基于正极膜层的总重量计。 In some embodiments, the cathode active material may include cathode active materials known in the art for batteries. As an example, the cathode active material may include at least one of the following materials: an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials of batteries can also be used. Only one type of these positive electrode active materials may be used alone, or two or more types may be used in combination. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO 2 ), lithium nickel oxides (such as LiNiO 2 ), lithium manganese oxides (such as LiMnO 2 , LiMn 2 O 4 ), lithium Nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1/3 Co 1/3 Mn 1/3 O 2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (can also be abbreviated to NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (can also be abbreviated to NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (can also be abbreviated to NCM 622 ), LiNi At least one of 0.8 Co 0.1 Mn 0.1 O 2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O 2 ) and its modified compounds. The olivine structure contains Examples of lithium phosphates may include, but are not limited to, lithium iron phosphate (such as LiFePO 4 (also referred to as LFP)), composites of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), lithium manganese phosphate and carbon. At least one of composite materials, lithium iron manganese phosphate, and composite materials of lithium iron manganese phosphate and carbon. The weight ratio of the positive electrode active material in the positive electrode film layer is 80-100% by weight, based on the total weight of the positive electrode film layer count.
在一些实施方式中，正极膜层还可选地包括粘结剂。作为示例，所述粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。所述粘结剂在正极膜层中的重量比为0-20重量％，基于正极膜层的总重量计。In some embodiments, the positive electrode film layer optionally further includes a binder. As examples, the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene At least one of ethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin. The weight ratio of the binder in the positive electrode film layer is 0-20% by weight, based on the total weight of the positive electrode film layer.
在一些实施方式中，正极膜层还可选地包括导电剂。作为示例，所述导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至 少一种。所述导电剂在正极膜层中的重量比为0-20重量％，基于正极膜层的总重量计。In some embodiments, the positive electrode film layer optionally further includes a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers. The weight ratio of the conductive agent in the positive electrode film layer is 0-20% by weight, based on the total weight of the positive electrode film layer.
在一些实施方式中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分，例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料，其中所述正极浆料固含量为40-80wt％，室温下的粘度调整到5000-25000mPa·s，将正极浆料涂覆在正极集流体的表面，烘干后经过冷轧机冷压后形成正极极片；正极粉末涂布单位面密度为150-350mg/m 2，正极极片压实密度为3.0-3.6g/cm 3，可选为3.3-3.5g/cm 3。所述压实密度的计算公式为 In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components in a solvent (such as N -methylpyrrolidone), forming a positive electrode slurry, wherein the solid content of the positive electrode slurry is 40-80wt%, the viscosity at room temperature is adjusted to 5000-25000mPa·s, and the positive electrode slurry is coated on the surface of the positive electrode current collector , dried and cold-pressed by a cold rolling mill to form a positive electrode piece; the unit area density of the positive electrode powder coating is 150-350 mg/m 2 , and the compacted density of the positive electrode piece is 3.0-3.6g/cm 3 , optionally 3.3 -3.5g/cm 3 . The calculation formula of the compacted density is
压实密度＝涂布面密度/(挤压后极片厚度-集流体厚度)。Compaction density = coating surface density / (thickness of electrode piece after extrusion - thickness of current collector).
负极极片Negative pole piece
负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，所述负极膜层包括本发明的第一方面或根据本发明的第二方面制备的负极活性材料。The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector. The negative electrode film layer includes the negative electrode active material prepared according to the first aspect of the present invention or according to the second aspect of the present invention.
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜层设置在负极集流体相对的两个表面中的任意一者或两者上。As an example, the negative electrode current collector has two opposite surfaces in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
在一些实施方式中，所述负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料形成在高分子材料基材上而形成。其中，金属材料包括但不限于铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等，高分子材料基材包括但不限于聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等基材。In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, copper foil can be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base material. The composite current collector can be formed by forming a metal material on a polymer material substrate. Among them, metal materials include but are not limited to copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc., and polymer material substrates include but are not limited to polypropylene (PP), polyethylene terephthalate Glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE) and other base materials.
在一些实施方式中，所述负极活性材料在负极膜层中的重量比为70-100重量％，基于负极膜层的总重量计。In some embodiments, the weight ratio of the negative active material in the negative electrode film layer is 70-100% by weight, based on the total weight of the negative electrode film layer.
在一些实施方式中，负极膜层还可选地包括粘结剂。所述粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。所述粘结剂在负极膜层中的重量比为0-30重量％，基于负极膜层的总重量计。In some embodiments, the negative electrode film layer optionally further includes a binder. The binder can be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), polysodium acrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), poly At least one of methacrylic acid (PMAA) and carboxymethyl chitosan (CMCS). The weight ratio of the binder in the negative electrode film layer is 0-30% by weight, based on the total weight of the negative electrode film layer.
在一些实施方式中，负极膜层还可选地包括导电剂。导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。所述导电剂在负极膜层中的重量比为0-20重量％，基于负极膜层的总重量计。In some embodiments, the negative electrode film layer optionally further includes a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers. The weight ratio of the conductive agent in the negative electrode film layer is 0-20% by weight, based on the total weight of the negative electrode film layer.
在一些实施方式中，负极膜层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。所述其他助剂在负极膜层中的重量比为0-15重量％，基于负极膜层的总重量计。In some embodiments, the negative electrode film layer optionally includes other auxiliaries, such as thickeners (such as sodium carboxymethylcellulose (CMC-Na)) and the like. The weight ratio of the other additives in the negative electrode film layer is 0-15% by weight, based on the total weight of the negative electrode film layer.
在一些实施方式中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极活性材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极浆料，其中所述负极浆料固含量为30-70wt％，室温下的粘度调整到2000-10000mPa·s；将所得到的负极浆料涂覆在负极集流体上，经过干燥工序，冷压例如对辊，得到负极极片。负极粉末涂布单位面密度为75-220mg/m 2，负极极片压实密度1.2-2.0g/m 3。 In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative active materials, conductive agents, binders and any other components in a solvent (such as deionized water), forming a negative electrode slurry, wherein the solid content of the negative electrode slurry is 30-70wt%, and the viscosity at room temperature is adjusted to 2000-10000mPa·s; the obtained negative electrode slurry is coated on the negative electrode current collector, After the drying process and cold pressing, such as against rollers, the negative electrode piece is obtained. The negative electrode powder coating unit area density is 75-220mg/m 2 , and the negative electrode plate compacted density is 1.2-2.0g/m 3 .
电解质electrolyte
电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以是液态的、凝胶态的或全固态的。The electrolyte plays a role in conducting ions between the positive and negative electrodes. There is no specific restriction on the type of electrolyte in this application, and it can be selected according to needs. For example, the electrolyte can be liquid, gel, or completely solid.
在一些实施方式中，所述电解质采用电解液。所述电解液包括电解质盐和溶剂。In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes electrolyte salts and solvents.
在一些实施方式中，电解质盐可选自六氟磷酸锂(LiPF 6)、四氟硼酸锂(LiBF 4)、高氯酸锂(LiClO 4)、六氟砷酸锂(LiAsF 6)、双氟磺酰亚胺锂(LiFSI)、双三氟甲磺酰亚胺锂(LiTFSI)、三氟甲磺酸锂(LiTFS)、二氟草酸硼酸锂(LiDFOB)、二草酸硼酸锂(LiBOB)、二氟磷酸锂(LiPO 2F 2)、二氟二草酸磷酸锂(LiDFOP)及四氟草酸磷酸锂(LiTFOP)中的一种或几种。所述电解质盐的浓度通常为0.5-5mol/L。 In some embodiments, the electrolyte salt may be selected from lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), bisfluorosulfonyl Lithium amine (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoromethanesulfonate borate (LiDFOB), lithium difluoromethane borate (LiBOB), lithium difluorophosphate (LiPO 2 F 2 ), lithium difluorodioxalate phosphate (LiDFOP) and lithium tetrafluorooxalate phosphate (LiTFOP). The concentration of the electrolyte salt is usually 0.5-5mol/L.
在一些实施方式中，溶剂可选自氟代碳酸乙烯酯(FEC)、碳酸亚乙酯(EC)、碳酸亚丙基酯(PC)、碳酸甲乙酯(EMC)、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)、碳酸亚丁酯(BC)、甲酸甲酯(MF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸甲酯(MB)、丁酸乙酯(EB)、1,4-丁内酯(GBL)、环丁砜(SF)、二甲砜(MSM)、甲乙砜(EMS)及二乙砜(ESE)中的一种或几种。In some embodiments, the solvent may be selected from fluoroethylene carbonate (FEC), ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC) ), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), methyl formate (MF), methyl acetate Ester (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB) , one or more of ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and diethyl sulfone (ESE) kind.
在一些实施方式中，所述电解液还可选地包括添加剂。例如添加剂可以包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。In some embodiments, the electrolyte optionally further includes additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain properties of the battery, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.
隔离膜Isolation film
在一些实施方式中，二次电池中还包括隔离膜。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。In some embodiments, the secondary battery further includes a separator film. There is no particular restriction on the type of isolation membrane in this application. Any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be used.
在一些实施方式中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。In some embodiments, the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation film can be a single-layer film or a multi-layer composite film, with no special restrictions. When the isolation film is a multi-layer composite film, the materials of each layer can be the same or different, and there is no particular limitation.
在一些实施方式中，所述隔离膜的厚度为6-40μm，可选为12-20μm；孔隙率为30-60％，孔径为100nm-1.0μm。In some embodiments, the thickness of the isolation film is 6-40 μm, optionally 12-20 μm; the porosity is 30-60%, and the pore diameter is 100 nm-1.0 μm.
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。In some embodiments, the positive electrode piece, the negative electrode piece and the separator film can be made into an electrode assembly through a winding process or a lamination process.
在一些实施方式中，二次电池可包括外包装。该外包装可用于封装上述电极组件及电解质。In some embodiments, the secondary battery may include an outer packaging. The outer packaging can be used to package the above-mentioned electrode assembly and electrolyte.
在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。In some embodiments, the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag. The material of the soft bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图3是作为一个示例的方形结构的二次电池5。This application has no particular limitation on the shape of the secondary battery, which can be cylindrical, square or any other shape. For example, FIG. 3 shows a square-structured secondary battery 5 as an example.
在一些实施方式中，参照图4，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53能够盖设于所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔内。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或多个，本领域技术人员可根据具体实际需求进行选择。In some embodiments, referring to FIG. 4 , the outer package may include a housing 51 and a cover 53 . The housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity. The housing 51 has an opening communicating with the accommodation cavity, and the cover plate 53 can cover the opening to close the accommodation cavity. The positive electrode piece, the negative electrode piece and the isolation film can be formed into the electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is packaged in the containing cavity. The electrolyte soaks into the electrode assembly 52 . The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.
在一些实施方式中，二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为一个或多个，具体数量本领域技术人员可根据电池模块的应用和容量进行选择。In some embodiments, secondary batteries can be assembled into battery modules, and the number of secondary batteries contained in the battery module can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery module.
在一些实施方式中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以为一个或多个，具体数量本领域技术人员可根据电池包的应用和容量进行选择。In some embodiments, the above-mentioned battery modules can also be assembled into a battery pack. The number of battery modules contained in the battery pack can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery pack.
本申请的第四方面提供一种用电装置，包括选自本申请的第二方面的二次电池、电池模块或电池包。所述二次电池、电池模块、或电池包可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电装置可以包括移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能***等，但不限于此。A fourth aspect of the present application provides an electrical device, including a secondary battery, a battery module or a battery pack selected from the second aspect of the present application. The secondary battery, battery module, or battery pack may be used as a power source for the electrical device, or may be used as an energy storage unit for the electrical device. The electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, and electric golf carts). , electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited to these.
作为所述用电装置，可以根据其使用需求来选择二次电池、电池模块或电池包。As the power-consuming device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.
图5是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。Figure 5 is an electrical device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the secondary battery for the electrical device, a battery pack or battery module can be used.
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用二次电池作为电源。As another example, the device may be a mobile phone, a tablet, a laptop, etc. The device is usually required to be thin and light, and a secondary battery can be used as a power source.
实施例Example
为了使本申请所解决的技术问题、技术方案及有益效果更加清楚，以下将结合实施例和附图对本申请进行进一步详细说明。显然，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。以下对至少一个示例性实施例的描述实际上仅仅是说明性的，决不作为对本申请及其应用的任何限制。基于本申请中的实施例，本领域普通技术人员在没有付出创造性劳动前提下所获得的所有其他实施例都属于本申请保护的范围。In order to make the technical problems, technical solutions and beneficial effects solved by this application clearer, this application will be further described in detail below with reference to the embodiments and drawings. Obviously, the described embodiments are only some of the embodiments of the present application, but not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the present application and its applications. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of this application.
实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。If specific techniques or conditions are not specified in the examples, the techniques or conditions described in literature in the field or product instructions will be followed. If the manufacturer of the reagents or instruments used is not indicated, they are all conventional products that can be purchased commercially.
一、制备实施例1. Preparation Example
负极活性材料的制备Preparation of negative active materials
制备实施例1Preparation Example 1
(1)向带有搅拌装置的混合机中，加入10kg平面尺寸为100μm的鳞片天然石墨。(1) Add 10kg of natural graphite flakes with a plane size of 100μm into a mixer equipped with a stirring device.
(2)向步骤(1)设备中加入10kg的3wt％的乙酸锂水溶液，在1200rpm下搅拌5小时，使鳞片天然石墨完全分散。然后使用真空抽滤机在0.01mPa压力下过滤，将滤出物在干燥箱中在90℃温度下烘干6小时，然后将所得固体利用气流式打散机打散2小 时。最后将固体放入管式炉中，在氮气下在450℃下常压烧结5h，自然冷却至室温，得到Li 2CO 3包覆的鳞片天然石墨。 (2) Add 10kg of 3wt% lithium acetate aqueous solution to the equipment in step (1) and stir at 1200rpm for 5 hours to completely disperse the flake natural graphite. Then use a vacuum filter to filter under a pressure of 0.01 mPa, dry the filtrate in a drying oven at a temperature of 90°C for 6 hours, and then use an airflow disperser to disperse the obtained solid for 2 hours. Finally, the solid was put into a tube furnace, sintered under nitrogen at 450°C for 5 hours at normal pressure, and then naturally cooled to room temperature to obtain Li 2 CO 3 -coated flake natural graphite.
(3)将步骤(2)中获得的Li 2CO 3包覆的鳞片天然石墨依次在气流式粉碎整形机中粉碎和整形，在气流式打散机打散2小时，在振动筛分机中筛分，得到Dv50为20μm的球形石墨颗粒。 (3) The Li 2 CO 3- coated flake natural graphite obtained in step (2) is sequentially crushed and shaped in an airflow crushing and shaping machine, dispersed in an airflow dispersing machine for 2 hours, and screened in a vibrating screening machine. points to obtain spherical graphite particles with a Dv50 of 20 μm.
(3i)将球形颗粒与沥青在加热机中在200℃下在常压下600rpm下进行搅拌混合30min，然后将所得混合物置于烧结炉中在1200℃在N2气氛下碳化5小时，得到碳包覆的球形颗粒。(3i) Stir the spherical particles and asphalt in a heating machine at 200°C and 600rpm under normal pressure for 30 minutes, and then place the resulting mixture in a sintering furnace for carbonization at 1200°C in an N2 atmosphere for 5 hours to obtain a carbon package covered spherical particles.
(4)在带有搅拌装置的混合机中，取10kg上述碳包覆后的球形颗粒加入10kg的3wt％的乙酸锂水溶液，在1200rpm下搅拌5小时。然后使用真空抽滤机在0.01mPa压力下过滤，将滤出物在干燥箱中在90℃温度下烘干6小时，然后将所得固体利用气流式打散机打散2小时。最后将固体放入管式炉中，在氮气下在450℃下常压烧结5h，，得到所述负极活性材料，其为Li 2CO 3包覆外表面和内部孔隙的球形天然石墨。 (4) In a mixer with a stirring device, add 10 kg of the above carbon-coated spherical particles to 10 kg of 3 wt% lithium acetate aqueous solution, and stir at 1200 rpm for 5 hours. Then use a vacuum filter to filter under a pressure of 0.01 mPa, dry the filtrate in a drying oven at a temperature of 90°C for 6 hours, and then use an airflow disperser to disperse the obtained solid for 2 hours. Finally, the solid was put into a tube furnace and sintered under nitrogen at 450°C for 5 hours at normal pressure to obtain the negative active material, which is spherical natural graphite with Li 2 CO 3 coating the outer surface and internal pores.
其中所述负极活性材料的平均体积粒径Dv50为17μm；其SEM图像见图1。其他相关的产品参数汇总于表1。The average volume particle size Dv50 of the negative active material is 17 μm; its SEM image is shown in Figure 1. Other relevant product parameters are summarized in Table 1.
制备实施例2Preparation Example 2
重复制备实施例1的步骤进行，区别在于，在步骤(2)和(4)中的烧结温度均提高至750℃，烧结1h。该温度下Li2CO3开始分解为Li2O和CO2，将人工SEI膜的成分调整Li 2CO3和Li 2O共存的状态。 Repeat the steps of Preparation Example 1, except that the sintering temperature in steps (2) and (4) is increased to 750°C and the sintering is performed for 1 hour. At this temperature, Li2CO3 begins to decompose into Li2O and CO2, and the composition of the artificial SEI film is adjusted to a state where Li 2 CO3 and Li 2 O coexist.
制备实施例3Preparation Example 3
重复制备实施例1的步骤进行，区别在于，在步骤(2)和(4)中的烧结温度均提高至850℃，烧结1h。Repeat the steps of Preparation Example 1, except that the sintering temperature in steps (2) and (4) is increased to 850°C and the sintering is performed for 1 hour.
制备实施例4Preparation Example 4
重复制备实施例1的步骤进行，区别在于，不包括步骤(3i)。The steps of Preparation Example 1 were repeated, except that step (3i) was not included.
制备实施例5Preparation Example 5
重复制备实施例1的步骤进行，区别在于，在步骤(2)和(4)中的乙酸锂替换为柠檬酸锂。Repeat the steps of Preparation Example 1, except that the lithium acetate in steps (2) and (4) is replaced by lithium citrate.
制备实施例6Preparation Example 6
重复制备实施例1的步骤进行，区别在于，在步骤(2)和(4)中，将乙酸锂替换 为碳酸锂，并且在打散后不进行烧结步骤。因碳酸锂在水中溶解度很小，改为加入10kg饱和碳酸锂水溶液，重复步骤(2)2次。Repeat the steps of Preparation Example 1, except that in steps (2) and (4), lithium acetate is replaced by lithium carbonate, and the sintering step is not performed after dispersion. Because the solubility of lithium carbonate in water is very small, add 10kg of saturated lithium carbonate aqueous solution instead, and repeat step (2) twice.
制备实施例7Preparation Example 7
重复制备实施例1的步骤进行，区别分别在于，在步骤(2)中乙酸锂溶液的用量为10kg的8wt％的乙酸锂水溶液，在步骤(4)中乙酸锂溶液的用量为10kg的1wt％的乙酸锂水溶液。Repeat the steps of Preparation Example 1, except that in step (2), the amount of lithium acetate solution is 10kg of 8wt% lithium acetate aqueous solution, and in step (4), the amount of lithium acetate solution is 10kg of 1wt% of lithium acetate aqueous solution.
制备实施例8Preparation Example 8
重复制备实施例1的步骤进行，区别分别在于，在步骤(2)中乙酸锂溶液的用量为10kg的1wt％的乙酸锂水溶液，在步骤(4)中乙酸锂溶液的用量为10kg的8wt％的乙酸锂水溶液。Repeat the steps of Preparation Example 1, except that in step (2), the amount of lithium acetate solution is 10kg of 1wt% lithium acetate aqueous solution, and in step (4), the amount of lithium acetate solution is 10kg of 8wt% of lithium acetate aqueous solution.
制备实施例9Preparation Example 9
重复制备实施例1的步骤进行，区别在于，在步骤(2)和(4)中，乙酸锂的浓度分别设为1wt％。Repeat the steps of Preparation Example 1, except that in steps (2) and (4), the concentrations of lithium acetate are set to 1 wt% respectively.
制备实施例10Preparation Example 10
重复制备实施例1的步骤进行，区别在于，在步骤(2)和(4)中，乙酸锂的浓度分别设为5wt％。Repeat the steps of Preparation Example 1, except that in steps (2) and (4), the concentrations of lithium acetate are set to 5 wt% respectively.
实施例11Example 11
重复制备实施例1的步骤进行，区别在于，在进行步骤(3i)之前，先进行表面处理：将球形石墨颗粒浸泡于80％的过氧化氢水溶液中浸泡3h时间，然后过滤，再置于烧结炉中在氧气气氛下在400℃温度下保持1小时，然后自然冷却。Repeat the steps of Preparation Example 1. The difference is that before step (3i), surface treatment is performed: soak the spherical graphite particles in 80% hydrogen peroxide aqueous solution for 3 hours, then filter, and then sinter. The furnace was maintained at a temperature of 400°C for 1 hour under an oxygen atmosphere, and then cooled naturally.
对比例1Comparative example 1
重复制备实施例1的步骤进行，区别在于，不进行步骤(2)。The steps of Preparation Example 1 were repeated, except that step (2) was not carried out.
以上各实施例和对比例的相关参数汇总于表1中。The relevant parameters of each of the above embodiments and comparative examples are summarized in Table 1.
测试方法Test Methods
负极活性材料中包覆层锂元素测试方法Test method for lithium element in coating layer of negative electrode active material
负极活性材料颗粒中锂的含量可用电感耦合等离子体原子发射光谱法(ICP)进行测量。将负极活性材料加入盐酸溶液中，盐酸作为消解试剂，只将外层锂盐溶解，无法溶解负极活性材料的内部锂盐包覆层和石墨烯，此时ICP测出的锂含量为外表面锂 含量Li 外。将溶解掉外部锂盐的负极活性材料加入浓硝酸中，浓硝酸作为消解试剂，采用微波消解法能够将石墨烯以及内部的锂盐完全溶解，此时ICP测试得到的锂含量为内部孔隙中的锂元素含量Li 内，同时也得到了总碳含量；由此，计算得到石墨颗粒内部孔隙中的锂元素与石墨颗粒外表面的锂元素的重量比(Li 内：Li 外)。 The lithium content in the negative active material particles can be measured by inductively coupled plasma atomic emission spectrometry (ICP). Add the negative active material to the hydrochloric acid solution. Hydrochloric acid is used as a digestion reagent. It only dissolves the outer lithium salt and cannot dissolve the internal lithium salt coating layer and graphene of the negative active material. At this time, the lithium content measured by ICP is the outer surface lithium. The content is exceptional . Add the negative active material that has dissolved the external lithium salt into concentrated nitric acid. The concentrated nitric acid is used as a digestion reagent. The graphene and the internal lithium salt can be completely dissolved using the microwave digestion method. At this time, the lithium content obtained by the ICP test is the lithium content in the internal pores. The lithium element content within Li is also obtained at the same time as the total carbon content; from this, the weight ratio of the lithium element in the internal pores of the graphite particles to the lithium element on the outer surface of the graphite particles ( inside Li: outside Li) is calculated.
表1 各实施例和对比例制备方法和产品的相关参数Table 1 Relevant parameters of preparation methods and products of each embodiment and comparative example
Figure PCTCN2022112832-appb-000001
Figure PCTCN2022112832-appb-000001
二、应用实施例2. Application examples
实施例1Example 1
1)正极极片的制备1) Preparation of positive electrode plate
将正极活性材料磷酸铁锂、导电炭黑SP及粘结剂PVDF按照重量比98:1:1分散至溶剂NMP中进行混合均匀，得到正极浆料；将正极浆料均匀涂布于正极集流体铝箔上，经烘干、冷压后，得到正极极片，其单位面积的涂覆量为0.27g/1540.25mm 2。 Disperse the cathode active material lithium iron phosphate, conductive carbon black SP and binder PVDF into the solvent NMP in a weight ratio of 98:1:1 and mix evenly to obtain a cathode slurry; apply the cathode slurry evenly to the cathode current collector On the aluminum foil, after drying and cold pressing, the positive electrode piece was obtained, and the coating amount per unit area was 0.27g/1540.25mm 2 .
2)负极极片的制备2) Preparation of negative electrode piece
将制备实施例1的负极活性材料、增稠剂羧甲基纤维素钠、粘接剂丁苯橡胶、导电剂炭黑，按照质量比96：1：1：2进行混合，加入去离子水，在真空搅拌机作用下获得负极浆料；将负极浆料均匀涂覆在铜箔上；将铜箔在室温晾干后转移至120℃烘箱干燥1h，然后过冷压、分切得到负极片，其单位面积的涂覆量为0.17g/1540.25mm 2。 The negative active material of Preparation Example 1, thickener sodium carboxymethylcellulose, adhesive styrene-butadiene rubber, and conductive agent carbon black were mixed according to a mass ratio of 96:1:1:2, and deionized water was added. Obtain the negative electrode slurry under the action of a vacuum mixer; apply the negative electrode slurry evenly on the copper foil; dry the copper foil at room temperature and then transfer it to a 120°C oven to dry for 1 hour, then supercool press and cut to obtain the negative electrode sheet, which The coating amount per unit area is 0.17g/1540.25mm 2 .
3)隔离膜3) Isolation film
选用12μm厚的孔隙率为50％的聚丙烯隔离膜。Choose a 12 μm thick polypropylene isolation film with a porosity of 50%.
4)电解液的制备4) Preparation of electrolyte
有机溶剂为含有碳酸亚乙酯(EC)、碳酸甲乙酯(EMC)和碳酸二乙酯(DEC)的混液，其中，EC、EMC和DEC的体积比为20:20:60。在含水量<10ppm的氩气气氛手套箱中，将充分干燥的锂盐LiPF6溶解于有机溶剂中，混合均匀，获得电解液。其中，锂盐的浓度为1mol/L。The organic solvent is a mixed solution containing ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC), where the volume ratio of EC, EMC and DEC is 20:20:60. In an argon atmosphere glove box with a water content of <10 ppm, dissolve the fully dry lithium salt LiPF6 in the organic solvent and mix evenly to obtain an electrolyte. Among them, the concentration of lithium salt is 1mol/L.
5)电池的制备5) Preparation of battery
将正极片、隔离膜、负极片按顺序叠好，使隔离膜处于正、负极片之间起到隔离的作用，再卷绕成方形的裸电芯后，装入铝塑膜，然后在80℃下烘烤除水后，注入10g相应的非水电解液、封口，经静置、热冷压、化成、夹具、分容等工序后，得到容量为4000mAh的成品电池。Stack the positive electrode sheet, isolation film, and negative electrode sheet in order so that the isolation film plays an isolation role between the positive and negative electrode sheets, then roll it into a square bare cell, put it into the aluminum-plastic film, and then heat it at 80 After baking at ℃ to remove water, 10g of the corresponding non-aqueous electrolyte is injected, sealed, and after standing, hot and cold pressing, formation, clamping, volume separation and other processes, a finished battery with a capacity of 4000mAh is obtained.
实施例2-11的二次电池和对比例1的二次电池与实施例1的二次电池制备方法相似，但是使用对应的制备实施例的负极活性材料。The secondary battery of Examples 2-11 and the secondary battery of Comparative Example 1 are similar to the secondary battery of Example 1, but use the negative active material of the corresponding preparation example.
三、电池性能测试3. Battery performance test
循环性能测试Cycle performance test
将电池置于60℃烘箱中，静置2h，待电池温度保持60℃进行充放电测试。1/3C电流恒流充电到3.65V，继续恒压充电，直至充电电流小于0.05C后截止，记录充电容量C01；暂停5min；1/3C电流恒流放电到2.0V，记录放电容量C02。Place the battery in a 60°C oven and let it stand for 2 hours. When the battery temperature remains at 60°C, charge and discharge tests are performed. Charge with a constant current of 1/3C to 3.65V, continue constant voltage charging until the charging current is less than 0.05C, then record the charging capacity C01; pause for 5 minutes; discharge with a constant current of 1/3C to 2.0V, record the discharge capacity C02.
1C电流恒流充电到3.65V，继续恒压充电，直至充电电流小于0.05C后截止，记录充电容量C11；暂停5min；1C电流恒流放电到2.5V，记录放电容量C12；暂停5min。以上为电池的第一个充放电循环，不断重复，直至电池循环300圈后，记录放电容量C3002。1C current constant current charging to 3.65V, continue constant voltage charging until the charging current is less than 0.05C and then cut off, record the charging capacity C11; pause for 5 minutes; 1C current constant current discharge to 2.5V, record the discharge capacity C12; pause for 5 minutes. The above is the first charge and discharge cycle of the battery, which is repeated until the battery has cycled 300 times, and the discharge capacity C3002 is recorded.
首次库伦效率＝C02/C01；First Coulomb efficiency = C02/C01;
300圈容量保持率＝C3002/C12Capacity retention rate after 300 cycles = C3002/C12
三、各实施例、对比例测试结果3. Test results of each embodiment and comparative example
按照上述方法分别制备各实施例和对比例的电池，并测量各项性能参数，结果见下表2。Batteries of each example and comparative example were prepared according to the above method, and various performance parameters were measured. The results are shown in Table 2 below.
表2 各实施例和对比例的性能测试Table 2 Performance tests of each embodiment and comparative example
Figure PCTCN2022112832-appb-000002
Figure PCTCN2022112832-appb-000002
通过上述实施例和对比例可得知，本申请的负极活性材料有效地提高相应的电池的首次库伦效率和循环稳定性；例如，相应的二次电池的首次库伦效率可达到89％以上，300圈后的容量保持率可达到95％以上。It can be known from the above examples and comparative examples that the negative active material of the present application can effectively improve the first Coulombic efficiency and cycle stability of the corresponding battery; for example, the first Coulombic efficiency of the corresponding secondary battery can reach more than 89%, 300 The capacity retention rate after lap can reach more than 95%.
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。It should be noted that the present application is not limited to the above-described embodiment. The above-mentioned embodiments are only examples. Within the scope of the technical solution of the present application, embodiments that have substantially the same structure as the technical idea and exert the same functions and effects are included in the technical scope of the present application. In addition, within the scope that does not deviate from the gist of the present application, various modifications that can be thought of by those skilled in the art are made to the embodiments, and other forms constructed by combining some of the constituent elements of the embodiments are also included in the scope of the present application. .

Claims (12)

  1. 一种负极活性材料，其包含具有内部孔隙的石墨颗粒以及包覆在石墨颗粒内部孔隙和颗粒外表面的锂盐包覆层，其中石墨颗粒内部孔隙中的锂元素与石墨颗粒外表面的锂元素的重量比为1～10:1。An anode active material, which includes graphite particles with internal pores and a lithium salt coating layer coating the internal pores of the graphite particles and the outer surface of the particles, wherein the lithium element in the internal pores of the graphite particles and the lithium element on the outer surface of the graphite particles The weight ratio is 1~10:1.
  2. 根据权利要求1所述的负极活性材料，其特征在于，所述锂盐包覆层满足如下特征中的至少一个：The negative active material according to claim 1, wherein the lithium salt coating layer meets at least one of the following characteristics:
    (1)所述锂盐包覆层的含量为0.01％-6％，基于负极活性材料的总重量计；(1) The content of the lithium salt coating layer is 0.01%-6%, based on the total weight of the negative active material;
    (2)所述石墨颗粒内部孔隙的锂盐包覆层的厚度为1-20nm，所述石墨颗粒外表面的锂盐包覆层的厚度为1-30nm。(2) The thickness of the lithium salt coating layer in the internal pores of the graphite particles is 1-20 nm, and the thickness of the lithium salt coating layer on the outer surface of the graphite particles is 1-30 nm.
  3. 根据权利要求1或2所述的负极活性材料，其特征在于，其满足如下特征中的至少一个：The negative active material according to claim 1 or 2, characterized in that it satisfies at least one of the following characteristics:
    (1)所述石墨为天然石墨；(1) The graphite is natural graphite;
    (2)所述锂盐为无机锂盐，可选地为选自碳酸盐、氧化锂、磷酸锂和氟化锂中的一种或多种。(2) The lithium salt is an inorganic lithium salt, optionally one or more selected from the group consisting of carbonate, lithium oxide, lithium phosphate and lithium fluoride.
  4. 根据权利要求1-3中任一项所述的负极活性材料，其特征在于，所述负极活性材料的平均体积粒径D v50为10-30μm。 The negative active material according to any one of claims 1 to 3, wherein the average volume particle diameter Dv50 of the negative active material is 10-30 μm.
  5. 根据权利要求1-4中任一项所述的负极活性材料，其特征在于，在石墨与锂盐包覆层之间，还存在碳包覆层；可选地，所述碳包覆层的包覆量为0.2-10％，基于负极活性材料的总重量计。The negative active material according to any one of claims 1 to 4, characterized in that there is also a carbon coating layer between the graphite and the lithium salt coating layer; optionally, the carbon coating layer The coating amount is 0.2-10% based on the total weight of the negative active material.
  6. 一种制备负极活性材料的方法，其包括：A method of preparing negative active material, which includes:
    (1)提供鳞片石墨；(1) Provide flake graphite;
    (2)使用含锂原料包覆鳞片石墨，使得在鳞片石墨表面形成锂盐包覆层；(2) Use lithium-containing raw materials to coat the flake graphite so that a lithium salt coating layer is formed on the surface of the flake graphite;
    (3)对步骤(2)中获得的鳞片石墨进行整形，得到球形石墨；(3) Shape the flake graphite obtained in step (2) to obtain spherical graphite;
    (4)使用含锂原料包覆所述球形石墨，使得球形石墨表面形成锂盐包覆层，得到所述负极活性材料；(4) Use lithium-containing raw materials to coat the spherical graphite so that a lithium salt coating layer is formed on the surface of the spherical graphite to obtain the negative active material;
    其中所述负极活性材料，其包含具有内部孔隙的石墨以及包覆在石墨内部孔隙和外表面的锂盐包覆层，其中石墨内部孔隙中的锂元素与石墨外表面的锂元素的重量比为1～10:1。The negative active material includes graphite with internal pores and a lithium salt coating layer covering the internal pores and outer surface of the graphite, wherein the weight ratio of the lithium element in the internal pores of the graphite to the lithium element on the outer surface of the graphite is: 1～10:1.
  7. 根据权利要求6所述的方法，其特征在于，在步骤(1)与(2)之间或在步骤 (3)与(4)之间，进行碳包覆或表面处理。The method of claim 6, wherein carbon coating or surface treatment is performed between steps (1) and (2) or between steps (3) and (4).
  8. 根据权利要求6或7所述的方法，其特征在于，在步骤(3)与(4)之间，进行碳包覆或表面处理。The method according to claim 6 or 7, characterized in that, between steps (3) and (4), carbon coating or surface treatment is performed.
  9. 根据权利要求6-8中任一项所述的方法，其特征在于，在步骤(2)中，所述含锂原料包含碳酸锂、氢氧化锂、锂的羧酸盐、硫酸锂、氟化锂和磷酸锂中的至少一种，可选地包含碳酸锂、乙酸锂、柠檬酸锂、草酸锂、硫酸锂、氟化锂和磷酸锂中的至少一种。The method according to any one of claims 6 to 8, characterized in that, in step (2), the lithium-containing raw material includes lithium carbonate, lithium hydroxide, lithium carboxylate, lithium sulfate, fluoride At least one of lithium and lithium phosphate optionally includes at least one of lithium carbonate, lithium acetate, lithium citrate, lithium oxalate, lithium sulfate, lithium fluoride and lithium phosphate.
  10. 根据权利要求6-9中任一项所述的方法，其特征在于，步骤(2)包括：将含锂原料制备成相应的溶液；将所述鳞片石墨分散在所述溶液中，得到混合物；将所述混合物进行过滤、烘干和打散，得到固体粉末；将所述固体粉末在保护气氛或真空下300-900℃烧结0.5-8h，在鳞片石墨表面形成锂盐包覆层。The method according to any one of claims 6 to 9, characterized in that step (2) includes: preparing lithium-containing raw materials into corresponding solutions; dispersing the flake graphite in the solution to obtain a mixture; The mixture is filtered, dried and dispersed to obtain a solid powder; the solid powder is sintered at 300-900°C for 0.5-8 hours under a protective atmosphere or vacuum to form a lithium salt coating layer on the surface of the flake graphite.
  11. 一种二次电池，其特征在于，A secondary battery characterized by:
    包括权利要求1-5中任一项所述的负极活性材料或根据权利要求6-10中任一项所述的方法制备的负极活性材料。It includes the negative active material according to any one of claims 1 to 5 or the negative active material prepared according to the method according to any one of claims 6 to 10.
  12. 一种用电装置，其特征在于，包括选自权利要求11所述的二次电池。An electrical device, characterized in that it includes a secondary battery selected from the group consisting of claim 11.
PCT/CN2022/112832 2022-08-16 2022-08-16 Negative electrode active material, manufacturing method, secondary battery, and electrical device WO2024036485A1 (en)

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