WO2023082157A1 - 一种二次电池和用电装置 - Google Patents

一种二次电池和用电装置 Download PDF

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Publication number
WO2023082157A1
WO2023082157A1 PCT/CN2021/130166 CN2021130166W WO2023082157A1 WO 2023082157 A1 WO2023082157 A1 WO 2023082157A1 CN 2021130166 W CN2021130166 W CN 2021130166W WO 2023082157 A1 WO2023082157 A1 WO 2023082157A1
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Prior art keywords
negative electrode
active material
artificial graphite
electrode active
secondary battery
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PCT/CN2021/130166
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English (en)
French (fr)
Inventor
游兴艳
吴益扬
王育文
廖婵
武宝珍
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Contemporary Amperex Technology Co Ltd
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Contemporary Amperex Technology Co Ltd
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Priority to CN202180094525.4A priority Critical patent/CN117015870A/zh
Priority to EP21943313.3A priority patent/EP4207372A4/en
Priority to PCT/CN2021/130166 priority patent/WO2023082157A1/zh
Priority to US18/176,265 priority patent/US20230231134A1/en
Publication of WO2023082157A1 publication Critical patent/WO2023082157A1/zh
Anticipated expiration legal-status Critical
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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
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the field of electrochemistry, in particular to a secondary battery and an electrical device.
  • secondary batteries Due to the advantages of high energy density, long cycle life and no memory effect, secondary batteries are widely used in wearable devices, smart phones, drones, electric vehicles and large energy storage equipment. It is a new type of green chemical power source with development potential, but it also puts forward higher requirements for the comprehensive performance of the secondary battery, such as having a long service life and good rate performance at the same time. Therefore, how to simultaneously maintain the service life and rate performance of the secondary battery has become an urgent problem to be solved.
  • the present application was made in view of the above-mentioned problems, and an object thereof is to improve both the storage life and the rate performance of a secondary battery.
  • the present application provides a secondary battery and an electrical device.
  • the first aspect of the present application provides a secondary battery, which includes a negative electrode sheet, the negative electrode sheet includes a negative electrode current collector, a first negative electrode material layer and a second negative electrode material layer, the first negative electrode material layer is located Between the negative electrode current collector and the second negative electrode material layer, the first negative electrode material layer includes a first negative electrode active material, and the second negative electrode material layer includes a second negative electrode active material, wherein the first negative electrode material layer includes a second negative electrode active material.
  • the negative active material includes artificial graphite A and artificial graphite B, the artificial graphite A includes secondary particles and the surface of the artificial graphite A has an amorphous carbon coating, the artificial graphite B includes primary particles and the artificial graphite The surface of B does not have an amorphous carbon coating layer.
  • the present application arranges the first negative electrode material layer and the second negative electrode material layer on the negative electrode current collector, and regulates the first negative electrode active material in the first negative electrode material layer, so that the first negative electrode active material includes artificial graphite A and Artificial graphite B can improve the rate performance and prolong the service life of the secondary battery.
  • the first negative electrode active material satisfies at least one of the following conditions: (1) the volume median particle diameter Dv50 is 13 ⁇ m-18 ⁇ m, optionally 15 ⁇ m-16 ⁇ m; (2) the particle size distribution satisfies 1 ⁇ (Dv90-Dv10)/Dv50 ⁇ 1.6, optional 1.1 ⁇ (Dv90-Dv10)/Dv50 ⁇ 1.5; (3) degree of graphitization is 92.8%-94.8%, optional 93.5%-94.5%; (4 ) The specific surface area is 1.0m 2 /g-1.6m 2 /g, optionally 1.05m 2 /g-1.3m 2 /g; (5) The compacted density of the powder is 1.6g/cm 3 -1.85g/cm 3 , 1.7g/cm 3 -1.8g/cm 3 is optional.
  • the first negative electrode active material satisfies at least one of the above conditions, which is beneficial to simultaneously improve the storage performance (for example, prolong storage life) and rate performance of the secondary
  • the artificial graphite A satisfies at least one of the following conditions: (1) the volume median particle diameter Dv50 is 14 ⁇ m-20 ⁇ m, optionally 16 ⁇ m-18 ⁇ m; (2) the particle size distribution satisfies 0.8 ⁇ ( Dv90-Dv10)/Dv50 ⁇ 1.7, optionally, 0.9 ⁇ (Dv90-Dv10)/Dv50 ⁇ 1.4; (3) the degree of graphitization is 91.0%-92.8%, optionally 91.5%-92.5%; (4) The specific surface area is 0.8m 2 /g-1.1m 2 /g, optional 0.9m 2 /g-1m 2 /g; (5) The compacted density of the powder is 1.5g/cm 3 -1.8g/cm 3 , Optionally 1.6g/cm 3 -1.8g/cm 3 ; (6) based on the quality of the first negative electrode active material, the mass percentage of the artificial graphite A is 10%-70%, optionally 30% %-50%; (7) The mass percentage of the
  • the artificial graphite B satisfies at least one of the following conditions: (1) the volume median particle diameter Dv50 is 12 ⁇ m-16 ⁇ m, optionally 15 ⁇ m-16 ⁇ m; the particle size distribution satisfies 0.5 ⁇ (Dv90-Dv10 )/Dv50 ⁇ 1.5; Optionally, 0.7 ⁇ (Dv90-Dv10)/Dv50 ⁇ 1.1; (2) The degree of graphitization is 93.5%-95.5%, optionally 94.0%-95.0%; (3) The specific surface area is 1.1m 2 /g-1.6m 2 /g, optional 1.3m 2 /g-1.5m 2 /g; (4) powder compacted density 1.6g/cm 3 -1.85g/cm 3 , optional 1.6g/cm 3 -1.8g/cm 3 ; (5) based on the quality of the first negative electrode active material, the mass percentage of the artificial graphite B is 30%-90%, optionally 40%-70% %.
  • the artificial graphite B is
  • the secondary battery satisfies at least one of the following conditions: (1) the volume median particle diameter Dv50 of the second negative electrode active material is less than or equal to the volume median of the first negative electrode active material Value particle diameter Dv50; Optionally, the ratio of the volume median particle diameter Dv50 of the second negative electrode active material to the volume median particle diameter Dv50 of the first negative electrode active material is 0.5-1; (2) the first negative electrode active material The ratio of the particle size distribution (DV90-DV10)/DV50 of the two negative electrode active materials to the particle size distribution (DV90-DV10)/DV50 of the first negative electrode active material is 0.8-1.1; (3) the ratio of the second negative electrode active material The degree of graphitization is less than the degree of graphitization of the first negative active material; optionally, the ratio of the degree of graphitization of the second negative active material to the degree of graphitization of the first negative active material is 0.95-0.99; (4) The specific surface area of the second negative electrode active material is less than the specific surface area of the first negative electrode active material;
  • the second negative electrode active material includes artificial graphite C, the artificial graphite C includes secondary particles and the surface of the artificial graphite C has an amorphous carbon coating;
  • the mass ratio of the amorphous carbon coating layer to the artificial graphite C is 2%-8%, optionally 4%-6%.
  • the second negative electrode material layer includes artificial graphite C, and the amorphous carbon coated with artificial graphite C is conducive to lithium ion intercalation and improves the rate performance of the secondary battery.
  • the synergistic effect of the first negative electrode material layer and the second negative electrode material layer Under this condition, the storage performance and rate performance of the secondary battery can be further improved.
  • the second negative electrode active material includes artificial graphite C, and the Dv50 of the artificial graphite C is less than the Dv50 of the artificial graphite A; optionally, the Dv50 of the artificial graphite C is the same as that of the artificial graphite
  • the ratio of Dv50 of A is 0.5-1.
  • the secondary battery meets at least one of the following conditions: (1) the ratio of the degree of graphitization of the artificial graphite C to the artificial graphite A is 0.95 to 1; (2) the artificial graphite The ratio of C to the specific surface area of the artificial graphite A is 0.93 to 1; (3) The ratio of the compacted density of the artificial graphite A to the artificial graphite C powder is 1.01-1.3. If the secondary battery satisfies at least one of the above conditions, it is beneficial to simultaneously improve the storage performance and rate performance of the secondary battery.
  • the compacted density of the first negative electrode material layer is greater than the compacted density of the second negative electrode material layer; the compacted density of the first negative electrode material layer is 1.6g/cm 3 -1.8g /cm 3 , optionally 1.6g/cm 3 -1.75g/cm 3 ; the compacted density of the second negative electrode material layer is 1.3g/cm 3 -1.6g/cm 3 , optionally 1.4g/cm 3 -1.6g/cm 3 .
  • the mass ratio of the first negative electrode material layer to the second negative electrode material layer is 2:3 to 3:2.
  • the first negative electrode active material and the second negative electrode active material both include a silicon-based material, and based on the mass of the first negative electrode active material, the mass percentage of the silicon-based material is denoted as X; Based on the mass of the second negative electrode active material, the mass percentage of the silicon-based material is denoted as Y; the secondary battery satisfies: X ⁇ Y; optionally, X ⁇ 5%, optionally, Y ⁇ 10%.
  • the introduction of the silicon-based material can increase the gram capacity of the first negative electrode active material and the second negative electrode active material, thereby helping to increase the energy density of the secondary battery.
  • the second aspect of the present application provides an electric device, including the secondary battery selected from the second aspect of the present application.
  • the application provides a secondary battery and an electrical device.
  • the secondary battery includes a negative electrode sheet, and the negative electrode sheet includes a negative electrode current collector, a first negative electrode material layer, and a second negative electrode material layer.
  • the first negative electrode material layer is located in the negative electrode collector. Between the fluid and the second negative electrode material layer, the first negative electrode material layer includes the first negative electrode active material, and the second negative electrode material layer includes the second negative electrode active material.
  • the present application arranges the first negative electrode material layer and the second negative electrode material layer on the negative electrode current collector, and regulates the first negative electrode active material in the first negative electrode material layer, so that the first negative electrode active material includes artificial graphite A and artificial graphite B , can simultaneously improve the energy density and rate performance of the secondary battery, and have a longer service life.
  • any product or method of the present application does not necessarily need to achieve all the above-mentioned advantages at the same time.
  • Fig. 1 is a schematic cross-sectional structure diagram of a negative electrode sheet according to an embodiment of the present application
  • FIG. 2 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • Fig. 3 is an exploded view of the secondary battery according to an embodiment of the present application shown in Fig. 2;
  • FIG. 4 is a schematic diagram of a battery module according to an embodiment of the present application.
  • FIG. 5 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • Fig. 6 is an exploded view of the battery pack according to an embodiment of the present application shown in Fig. 5;
  • FIG. 7 is a schematic diagram of an electrical device in which a secondary battery is used as a power source according to an embodiment of the present application.
  • ranges disclosed herein are defined in terms of lower and upper limits, and 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 and may be combined in any combination, ie 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, it is understood that ranges of 60-110 and 80-120 are contemplated. Additionally, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, 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" indicates that all real numbers between "0-5" have been listed in this article, and "0-5" is only an abbreviated representation of the combination of these values.
  • 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 in sequence, and may also include steps (b) and (a) performed in sequence.
  • 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) and so on.
  • the “comprising” and “comprising” mentioned in this application mean open or closed.
  • the “comprising” and “comprising” may mean that other components not listed may be included or included, or only listed components may be included or included.
  • the term "or” is inclusive unless otherwise stated.
  • the phrase "A or B” means “A, B, or both A and B.” More specifically, the condition "A or B” is satisfied by either of the following: 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).
  • the application provides a secondary battery and power device.
  • the present application is explained by taking the lithium ion battery as an example of the secondary battery, but the secondary battery of the present application is not limited to the lithium ion battery.
  • the present application proposes a secondary battery.
  • the secondary battery includes a negative electrode sheet.
  • the negative electrode sheet includes a negative electrode current collector 21, a first negative electrode material layer 22 and a second Negative electrode material layer 23, the first negative electrode material layer 22 is positioned between the negative electrode current collector 21 and the second negative electrode material layer 23, the first negative electrode material layer 22 includes the first negative electrode active material (not shown in the figure), the second negative electrode material Layer 23 includes a second negative electrode active material (not shown in the figure), wherein the first negative electrode active material includes artificial graphite A and artificial graphite B, the artificial graphite A includes secondary particles and the surface of the artificial graphite A has an amorphous carbon package. Coating layer, artificial graphite B includes primary particles and the surface of artificial graphite B does not have an amorphous carbon coating layer.
  • the first negative electrode active material includes The artificial graphite A and the artificial graphite B can simultaneously improve the rate performance of the secondary battery and prolong the service life.
  • the surface of artificial graphite A has an amorphous carbon coating layer, which can increase the insertable sites of lithium ions, and the lattice spacing is relatively large, and lithium intercalation is relatively fast, which makes artificial graphite A
  • the artificial graphite B has a regular graphite crystal structure, has few structural defects, and has a high compaction density, which is beneficial to improving the energy density and life of the secondary battery. Therefore, under the synergistic effect of the artificial graphite A and the artificial graphite B, while ensuring the energy density, the rate performance of the secondary battery can be improved at the same time, and the service life can be extended.
  • the volume median particle diameter Dv50 of the first negative electrode active material is 13 ⁇ m-18 ⁇ m, optionally 15 ⁇ m-16 ⁇ m.
  • the rate performance of the secondary battery when the Dv50 of the first negative electrode active material is too large (for example greater than 18 ⁇ m), it is easy to affect the flatness of the first negative electrode material layer, thereby affecting the safety performance of the secondary battery.
  • the particle size distribution of the first negative electrode active material satisfies 1 ⁇ (Dv90-Dv10)/Dv50 ⁇ 1.6, optionally 1.1 ⁇ (Dv90-Dv10)/Dv50 ⁇ 1.5.
  • the applicant found that adjusting the value of (Dv90-Dv10)/Dv50 of the first negative electrode active material within the above-mentioned range is beneficial to simultaneously improve the rate performance and safety performance.
  • the present application has no special limitation on the Dv90 and Dv10 of the first negative electrode active material, as long as the above particle size range is satisfied, for example, the Dv90 of the first negative electrode active material is 24 ⁇ m-28 ⁇ m, and the Dv10 is 5 ⁇ m-12 ⁇ m.
  • the degree of graphitization of the first negative electrode active material is 92.8%-94.8%, optionally 93.5%-94.5%.
  • the applicant has found that the degree of graphitization can reflect the regularity of the internal structure of the material, etc., and when the graphitization of the first negative electrode active material is too low (for example, lower than 92.8%), it indicates that the artificial graphite A in the negative electrode active material is carbonized If the amount is high, side reactions will increase during use, which in turn will affect the storage and cycle life of the secondary battery; when the graphitization of the first negative electrode active material is too high (for example, greater than 94.8%), the rate performance will deteriorate, and at the same time make The preparation difficulty of the first negative electrode active material increases, and the production cost also increases. By regulating the degree of graphitization of the first negative electrode active material within the above range, it is beneficial to improve the storage performance and rate performance of the secondary battery and control its cost.
  • the specific surface area of the first negative electrode active material is 1.0m 2 /g-1.6m 2 /g, optionally 1.05m 2 /g-1.3m 2 /g.
  • the powder compacted density of the first negative electrode active material is 1.6 g/cm 3 -1.85 g/cm 3 , optionally 1.7 g/cm 3 -1.8 g/cm 3 .
  • the applicant has found that when the compacted density of the powder of the first negative electrode active material is too small (for example, less than 1.6g/cm 3 ), the particles of the first negative electrode active material are not tightly packed between the particles, and in the cycle process of the secondary battery In the middle, it is easy to form the problem that the first negative electrode material layer is damaged, which affects the service life of the secondary battery; when the powder compaction density of the first negative electrode active material is too large (for example, greater than 1.85g/cm 3 ), the first negative electrode The particles of the active material are packed too tightly, which affects the deintercalation process of lithium ions, thereby affecting the rate performance of the secondary battery.
  • the powder compacted density refers to the density of the powder of the corresponding material after being processed under 2T pressure.
  • the volume median particle diameter Dv50 of the artificial graphite A is 14 ⁇ m-20 ⁇ m, optionally 16 ⁇ m-18 ⁇ m. The applicant found that adjusting the Dv50 of the artificial graphite A within the above range is beneficial to improve the rate performance and safety performance of the secondary battery.
  • the particle size distribution of artificial graphite A satisfies 0.8 ⁇ (Dv90-Dv10)/Dv50 ⁇ 1.7, alternatively, 0.9 ⁇ (Dv90-Dv10)/Dv50 ⁇ 1.4.
  • the applicant found that by adjusting the value of (Dv90-Dv10)/Dv50 of artificial graphite A within the above range, it is beneficial to improve the rate performance and safety performance of the secondary battery.
  • the present application has no special limitation on Dv90 and Dv10 of artificial graphite A, as long as the above particle size range is met, for example, Dv90 of artificial graphite A is 25 ⁇ m-27 ⁇ m, and Dv10 is 7 ⁇ m-11 ⁇ m.
  • the degree of graphitization of artificial graphite A is 91.0%-92.8%, optionally 91.5%-92.5%.
  • the specific surface area of the artificial graphite A is 0.8m 2 /g-1.1m 2 /g, optionally 0.9m 2 /g-1m 2 /g.
  • the powder compacted density of artificial graphite A is 1.5 g/cm 3 -1.8 g/cm 3 , optionally 1.6 g/cm 3 -1.8 g/cm 3 .
  • the applicant found that by adjusting the powder compaction density of graphite A within the above range, it is beneficial to increase the compaction difference between the first negative electrode material layer and the second negative electrode material layer, and improve the performance of the secondary battery. rate performance, cycle performance and storage performance.
  • the mass ratio of the amorphous carbon coating layer in the artificial graphite A to the artificial graphite A is 1%-5%, optionally 3%-4%. The applicant found that by regulating the mass ratio of the amorphous carbon coating layer in the artificial graphite A to the artificial graphite A within the above range, the active sites of the first negative electrode active material are increased, which is beneficial to increase the rate of the secondary battery performance.
  • the mass percentage of artificial graphite A is 10%-70%, optionally 30%-50%.
  • the content of artificial graphite A was too high (such as higher than 70%) the content of artificial graphite B decreased, the first negative electrode material layer compacted deterioration, and surface defects increased simultaneously, and side reactions also increased thereupon, affecting secondary battery Storage life and cycle performance.
  • the volume median diameter Dv50 of artificial graphite B is 12 ⁇ m-16 ⁇ m, optionally 15 ⁇ m-16 ⁇ m; the particle size distribution satisfies 0.5 ⁇ (Dv90-Dv10)/Dv50 ⁇ 1.5; optionally, 0.7 ⁇ ( Dv90-Dv10)/Dv50 ⁇ 1.1.
  • the present application has no special limitation on Dv90 and Dv10 of artificial graphite B, as long as the above particle size range is satisfied, for example, Dv90 of artificial graphite B is 25 ⁇ m-30 ⁇ m, and Dv10 is 5 ⁇ m-10 ⁇ m.
  • the degree of graphitization of artificial graphite B is 93.5%-95.5%, optionally 94.0%-95.0%.
  • the specific surface area of the artificial graphite B is 1.1m 2 /g-1.6m 2 /g, optionally 1.3m 2 /g-1.5m 2 /g. The applicant found that by regulating the specific surface area of the artificial graphite B within the above range, it is beneficial to improve the storage performance of the secondary battery.
  • the powder compacted density of the artificial graphite B is 1.6 g/cm 3 -1.85 g/cm 3 , optionally 1.6 g/cm 3 -1.8 g/cm 3 .
  • the mass percentage of artificial graphite B is 30%-90%, optionally 40%-70%.
  • the applicant has found that when the mass percentage of artificial graphite B is too low (for example, less than 30%), the content of artificial graphite A is too high, which will deteriorate the compactness of the first negative electrode material layer and affect the storage performance of the secondary battery. ; When the content of artificial graphite B is too high (for example, higher than 90%), the content of artificial graphite A is reduced, which will affect the rate performance of the secondary battery.
  • the volume median particle diameter Dv50 of the second negative electrode active material in the secondary battery is less than or equal to the volume median particle diameter Dv50 of the first negative electrode active material, and the first negative electrode material layer and the second negative electrode can be regulated
  • the compaction of the material layers differentiates the compaction, and the compaction of the first negative electrode material layer is greater than that of the second material layer, which is convenient for improving the wettability of the electrolyte to the first negative electrode material layer.
  • the ratio of the volume median particle diameter Dv50 of the second negative electrode active material to the volume median particle diameter Dv50 of the first negative electrode active material is 0.5-1.
  • the Dv50 of the second negative electrode active material may be 6.5 ⁇ m-18 ⁇ m.
  • the ratio of the particle size distribution (DV90-DV10)/DV50 of the second negative electrode active material in the secondary battery to the particle size distribution ( DV 90- DV 10)/ DV 50 of the first negative electrode active material 0.8-1.1.
  • the degree of graphitization of the second negative electrode active material in the secondary battery is smaller than that of the first negative electrode active material, so that the kinetic advantages of the second negative electrode active material can be fully utilized.
  • the ratio of the graphitization degree of the second negative electrode active material to the graphitization degree of the first negative electrode active material is 0.95-0.99. The applicant found that by adjusting the ratio of the graphitization degree of the second negative electrode active material to the graphitization degree of the first negative electrode active material within the above range, it is beneficial to improve the rate performance of the secondary battery and control its cost.
  • the degree of graphitization of the second negative electrode active material may be 90%-92.12%.
  • the specific surface area of the second negative electrode active material in the secondary battery is smaller than the specific surface area of the first negative electrode active material, which can reasonably control the exposed area of the entire negative electrode sheet.
  • the ratio of the specific surface area of the second negative electrode active material to the specific surface area of the first negative electrode active material is 0.6-0.8. The applicant found that by adjusting the ratio of the specific surface area of the second negative electrode active material to the specific surface area of the first negative electrode active material within the above range, it is beneficial to improve the service life and rate performance of the secondary battery.
  • the specific surface area of the second negative active material may be 0.7m 2 /g-1m 2 /g.
  • the powder compacted density of the second negative electrode active material in the secondary battery is less than the powder compacted density of the first negative electrode active material, which can increase the density of the first negative electrode material layer and the second negative electrode material layer.
  • the difference in compaction is beneficial for the electrolyte to pass through the low-pressure dense second negative electrode active material to reach the first negative electrode material layer more smoothly, so as to bring out the excellent kinetic performance of the first negative electrode active material.
  • the ratio of the powder compacted density of the second negative electrode active material to the powder compacted density of the first negative electrode active material is 0.6-0.95.
  • the powder tap density of the second negative electrode active material may be 1.3 g/cm 3 -1.65 g/cm 3 .
  • the second negative electrode active material includes artificial graphite C
  • the artificial graphite C includes secondary particles and the surface of the artificial graphite C has an amorphous carbon coating; the amorphous carbon coating in the artificial graphite C is the same as the artificial graphite C.
  • the mass ratio of graphite C is 2%-8%, optionally 4%-6%.
  • the second negative electrode material layer including artificial graphite C is beneficial to improve the rate performance of the secondary battery, so that under the synergistic effect of the first negative electrode material layer and the second negative electrode material layer, the storage performance and rate performance of the secondary battery can be further improved.
  • the second negative electrode active material includes artificial graphite C
  • the Dv50 of artificial graphite C is smaller than the Dv50 of artificial graphite A, which can make the second negative electrode material layer denser than the first negative electrode material layer.
  • the ratio of Dv50 of artificial graphite C to Dv50 of artificial graphite A is 0.5-1. The applicant found that by adjusting the ratio of Dv50 of artificial graphite C to Dv50 of artificial graphite A within the above range, it is beneficial to simultaneously improve the rate performance and safety performance of the secondary battery.
  • the Dv50 of artificial graphite C may be 7 ⁇ m-13 ⁇ m.
  • the ratio of the degree of graphitization of the artificial graphite C to the artificial graphite A in the secondary battery is 0.95-1.
  • the graphitization degree of artificial graphite C may be 91%-92%.
  • the ratio of the specific surface area of artificial graphite C to artificial graphite A in the secondary battery is 0.93 to 1.
  • the specific surface area of artificial graphite C may be 0.7m 2 /g-1.1m 2 /g.
  • the ratio of the compacted density of the artificial graphite A to the artificial graphite C powder in the secondary battery is 1.01-1.3.
  • the applicant found that adjusting the ratio of the powder compacted density of artificial graphite A to artificial graphite C within the above range is beneficial to improve the rate performance, cycle performance and storage performance of the secondary battery.
  • the powder compacted density of artificial graphite C may be 1.3g/cm 3 -1.6g/cm 3 .
  • the compaction density of the first negative electrode material layer is greater than the compaction density of the second negative electrode material layer, so that the electrolyte can fully infiltrate the first negative electrode material layer and the second negative electrode material layer, and fully utilize the first negative electrode material layer.
  • the performance of the material layer and the second negative electrode material layer so as to simultaneously improve the rate performance and energy density of the electrochemical device.
  • the compacted density of the first negative electrode material layer is 1.6g/cm 3 -1.8g/cm 3 , optionally 1.6.g/cm 3 -1.75g/cm 3 ; the compacted density of the second negative electrode material layer is 1.3g /cm 3 -1.6g/cm 3 , optionally 1.4g/cm 3 -1.6g/cm 3 .
  • the mass ratio of the first negative electrode material layer to the second negative electrode material layer is 2:3 to 3:2.
  • the applicant found that when the mass ratio of the first negative electrode material layer and the second negative electrode material layer is too small (for example, less than 2:3), that is, the quality of the first negative electrode material layer is small, and the quality of the second negative electrode material layer is relatively small. Large, will affect the storage life of the secondary battery; when the mass ratio of the first negative electrode material layer and the second negative electrode material layer is too large (for example, greater than 3:2), that is, the quality of the first negative electrode material layer is large, the second negative electrode material layer The quality of the two negative electrode material layers is small, which will affect the rate performance of the secondary battery. By regulating the mass ratio of the first negative electrode material layer and the second negative electrode material layer within the above range, it is beneficial to simultaneously improve the rate performance and energy density of the secondary battery.
  • both the first negative electrode active material and the second negative electrode active material include a silicon-based material, based on the mass of the first negative electrode active material, the mass percentage of the silicon-based material is denoted as X; based on the second negative electrode active material The mass percentage of silicon-based materials is recorded as Y; the secondary battery satisfies: X ⁇ Y; optionally, X ⁇ 5%, optionally, Y ⁇ 10%, optionally X ⁇ 2%, Y ⁇ 6%.
  • the introduction of the silicon-based material increases the gram capacity of the first negative electrode active material or the second negative electrode active material, thereby increasing the energy density of the secondary battery.
  • natural graphite may also be included in the first negative electrode active material.
  • the present application has no special restrictions on the preparation methods of the artificial graphite A and the artificial graphite C, as long as the purpose of the present application can be achieved.
  • the preparation method may include but not limited to the following steps: first pretreat the coke raw material to remove impurities, then pyrolyze and granulate to obtain secondary particles, and then perform graphitization treatment, after screening and testing, the surface is coated with pitch, high-temperature carbonization, Artificial graphite A or artificial graphite C was obtained.
  • the present application has no particular limitation on the particle size of the secondary particles, as long as the purpose of the present application can be achieved, for example, the volume median particle diameter Dv50 of the secondary particles is 10 ⁇ m-20 ⁇ m.
  • the present application has no particular limitation on the temperature and time of the above-mentioned graphitization treatment, as long as the purpose of the application can be achieved, for example, the temperature of the graphitization treatment is 2400°C-3000°C, and the time of the graphitization treatment is 20h-30h.
  • This application has no special limitation on the temperature and time of high-temperature carbonization, as long as the purpose of this application can be achieved, for example, the temperature of high-temperature carbonization is 700°C-1500°C, and the time of high-temperature carbonization is 7h-15h.
  • the present application has no special limitation on the preparation method of the artificial graphite B, as long as the purpose of the present application can be achieved.
  • the preparation method may include but not limited to the following steps: the coke raw material is firstly pretreated to remove impurities, then pyrolytically granulated to obtain primary particles, then graphitized, and artificial graphite B is obtained after screening and testing.
  • the present application has no particular limitation on the particle size of the primary particles, as long as the purpose of the present application can be achieved, for example, the volume median particle diameter Dv50 of the primary particles is 12 ⁇ m-16 ⁇ m.
  • the present application has no particular limitation on the temperature and time of the above-mentioned graphitization treatment, as long as the purpose of the application can be achieved, for example, the temperature of the graphitization treatment is 2400°C-3000°C, and the time of the graphitization treatment is 18h-30h.
  • the structure (such as core and cladding layer) of artificial graphite A or artificial graphite C in this application can be tested using equipment and methods known in the art.
  • the following steps can be followed: select a micro-grid with a certain diameter (such as a diameter of 3mm), clamp the edge of the micro-grid with pointed tweezers, and place its film side up (observing the shiny side under the light, That is, the film surface), gently lay it flat on the white filter paper; take an appropriate amount of graphite particle sample (such as 1g) into a beaker filled with an appropriate amount of ethanol, and perform ultrasonic oscillation for 10min-30min; absorb it with a glass capillary, and then drop 2-3 Drop the sample to be tested onto the microgrid; after baking in the oven for 5 minutes, place the microgrid dripped with the sample to be tested on the sample stage, and use a transmission electron microscope (such as Hitachi HF-3300S Cs-corrected STEM) at a certain A transmission electron microscope (TEM)
  • Dv10, Dv50, and Dv90 in this application are all parameters known in the art, and can be measured using a laser particle size analyzer (such as Malvern Master Size 3000) with reference to the national standard GB/T 19077-2016 ("Particle Size Distribution Laser Diffraction Method") .
  • Dv10 refers to the particle size corresponding to when the cumulative volume distribution percentage of the measured material reaches 10%
  • Dv50 refers to the corresponding particle size when the cumulative volume distribution percentage of the measured material reaches 50%
  • Dv90 refers to the cumulative volume of the measured material The particle size corresponding to when the distribution percentage reaches 90%.
  • the degree of graphitization in the present application is a well-known meaning in the art, and can be tested by methods known in the art.
  • an X-ray diffractometer such as Bruker D8 Discover
  • the test method refers to the standard JIS K 0131-1996 ("General Rules for X-ray Diffraction Measurement and Analysis"), JB/T 4220-2011 (“Artificial graphite lattice Parameter Determination Method") and GB/T 24533-2019 ("Graphite Anode Materials for Lithium-ion Batteries”).
  • the copper target can be used as the anode target
  • the CuK ⁇ ray is used as the radiation source
  • the wavelength of the ray is
  • the scanning 2 ⁇ angle range is 20°-80°, and the scanning rate can be 4°/min.
  • the specific surface area in the present application is a well-known meaning in the art, and can be tested by methods known in the art. For example, you can refer to the national standard GB/T 19587-2017 ("Gas Adsorption BET Method for Determination of Specific Surface Area of Solid Matter"), use the nitrogen adsorption specific surface area analysis test method to test, and use the BET (Brunauer Emmett Teller) method to calculate, in which nitrogen adsorption
  • the specific surface area analysis test can be tested by the Tri-Star 3020 specific surface area pore size analysis tester of the American Micromeritics company.
  • the powder compacted density in this application is a well-known meaning in the art, and can be tested by methods known in the art.
  • the compacted density of the powder below, the compacted density of the powder M/(H ⁇ S).
  • a secondary battery typically includes a positive pole piece, a negative pole piece, an electrolyte, and a separator.
  • active ions are intercalated and extracted back and forth between the positive electrode and the negative electrode.
  • the electrolyte plays the role of conducting ions between the positive pole piece and the negative pole piece.
  • the separator is arranged between the positive pole piece and the negative pole piece, which mainly plays a role in preventing the short circuit of the positive and negative poles, and at the same time allows ions to pass through.
  • the positive pole piece includes a positive current collector and a positive film layer arranged on at least one surface of the positive current collector.
  • the positive electrode current collector has two opposing surfaces in its own thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposing surfaces of the positive electrode current collector.
  • the positive electrode current collector can be a metal foil or a composite current collector.
  • aluminum foil can be used as the metal foil.
  • the composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base.
  • the composite current collector can be formed by forming metal materials (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalic acid It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene glycol ester
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the positive electrode active material may be a positive electrode active material known in the art for batteries.
  • the positive active material may include at least one of the following materials: olivine-structured lithium-containing phosphate, lithium transition metal oxide, and their respective modified compounds.
  • the present application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials of batteries can also be used. These positive electrode active materials may be used alone or in combination of two or more.
  • 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 (also abbreviated as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (also abbreviated as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (also abbreviated as 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
  • the olivine structure contains Examples of lithium phosphates may include, but are not limited to, lithium iron phosphate (such as LiFePO 4 (also may be abbreviated as LFP)), composite materials of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), lithium manganese phosphate and carbon At least one of a composite material, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon.
  • lithium iron phosphate such as LiFePO 4 (also may be abbreviated as LFP)
  • composite materials of lithium iron phosphate and carbon such as LiMnPO 4
  • LiMnPO 4 lithium manganese phosphate and carbon
  • the positive electrode film layer may further optionally include 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 positive electrode film layer may also optionally include 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 positive electrode sheet can be prepared in the following manner: the above-mentioned components used to prepare the positive electrode sheet, such as positive electrode active material, conductive agent, binder and any other components, are dispersed in a solvent (such as N -methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.
  • a solvent such as N -methylpyrrolidone
  • the negative electrode collector has two opposing surfaces in its own thickness direction, and the first negative electrode material layer and the second negative electrode material layer are disposed on any one or both of the two opposing surfaces of the negative electrode current collector.
  • the negative electrode current collector of the negative electrode sheet can be a metal foil or a composite current collector.
  • copper foil can be used as the metal foil.
  • the composite current collector may include a base layer of polymer material and a metal layer formed on at least one surface of the base material of polymer material.
  • Composite current collectors can be formed by metal materials (copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyethylene terephthalic acid It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • the first negative electrode material layer and the second negative electrode material layer optionally further include a binder.
  • the binder can be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), poly At least one of methacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the first negative electrode material layer and the second negative electrode material layer optionally further include a conductive agent.
  • the conductive agent can be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the first negative electrode material layer and the second negative electrode material layer may optionally include other additives, such as thickeners (such as carboxymethylcellulose sodium (CMC-Na)) and the like.
  • thickeners such as carboxymethylcellulose sodium (CMC-Na)
  • the negative electrode sheet can be prepared in the following manner: the above-mentioned components for preparing the negative electrode sheet, such as the first negative electrode active material, a conductive agent, a binder, and any other components are dispersed in a solvent (such as In deionized water), the first negative electrode slurry is formed; the second negative electrode active material, conductive agent, binder and any other components are dispersed in a solvent (such as deionized water) to form the second negative electrode slurry; A negative electrode slurry is coated on the negative electrode current collector, and the negative electrode current collector containing the first negative electrode material layer is obtained after drying; then the second negative electrode slurry is coated on the first negative electrode material layer, dried, cold pressed After the process, the negative electrode sheet can be obtained.
  • a solvent such as In deionized water
  • the electrolyte plays the role of conducting ions between the positive pole piece and the negative pole piece.
  • the present application has no specific limitation on the type of electrolyte, which can be selected according to requirements.
  • electrolytes can be liquid, gel or all solid.
  • the electrolyte is an electrolytic solution.
  • the electrolyte solution includes an electrolyte salt and a solvent.
  • the electrolyte salt may be selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, trifluoromethane At least one of lithium sulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium difluorooxalate borate, lithium difluorodifluorooxalatephosphate and lithium tetrafluorooxalatephosphate.
  • the solvent may be selected from ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, Butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate At least one of ester, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • the electrolyte may optionally include additives.
  • additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain performances of the battery, such as additives that improve battery overcharge performance, additives that improve high-temperature or low-temperature performance of batteries, and the like.
  • a separator is further included in the secondary battery.
  • the present application has no particular limitation on the type of the isolation membrane, and any known porous structure isolation membrane with good chemical stability and mechanical stability can be selected.
  • the material of the isolation film can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the separator can be a single-layer film or a multi-layer composite film, without any particular limitation. When the separator is a multilayer composite film, the materials of each layer may be the same or different, and there is no particular limitation.
  • the positive pole piece, the negative pole piece and the separator can be made into an electrode assembly through a winding process or a lamination process.
  • the secondary battery may include an outer package.
  • the outer package can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard case, such as a hard plastic case, aluminum case, steel case, and the like.
  • 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 case may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
  • FIG. 2 shows a square-shaped 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 a side plate connected to the bottom plate, and the bottom plate and the side plates enclose to form an accommodating cavity.
  • the housing 51 has an opening communicating with the accommodating cavity, and the cover plate 53 can cover the opening to close the accommodating cavity.
  • the positive pole piece, the negative pole piece and the separator can be formed into an electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the accommodating cavity. Electrolyte is infiltrated in 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.
  • the secondary battery can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.
  • FIG. 4 is a battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 .
  • the plurality of secondary batteries 5 may be fixed by fasteners.
  • the battery module 4 may also include a case having a housing space in which a plurality of secondary batteries 5 are accommodated.
  • the above-mentioned battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.
  • FIGS. 5 and 6 show the battery pack 10 as an example.
  • a battery box and a plurality of battery modules 4 disposed in the battery box may be included in the battery pack 10 .
  • the battery box includes an upper box body 11 and a lower box body 12 , the upper box body 11 can cover the lower box body 12 and form a closed space for accommodating the battery module 4 .
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • the present application also provides an electric device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application.
  • the secondary battery, battery module, or battery pack can be used as a power source of the electric device, and can also be used as an energy storage unit of the electric device.
  • the electric devices may include mobile devices (such as mobile phones, notebook computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, etc.) , electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but not limited thereto.
  • a secondary battery, a battery module or a battery pack can be selected according to its use requirements.
  • FIG. 7 is an example of an electrical device.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • a battery pack or a battery module may be used.
  • a device may be a cell phone, tablet, laptop, or the like.
  • the device is generally required to be light and thin, and a secondary battery can be used as a power source.
  • the positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O 2 , the conductive agent conductive carbon black, and the binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 98:1:1, and then N-methylpyrrolidone (NMP) was added as The solvent was stirred under the action of a vacuum mixer until the system was uniform, and a positive electrode slurry with a solid content of 75 wt% was obtained.
  • the positive electrode slurry is evenly coated on one surface of aluminum foil with a thickness of 13 ⁇ m, dried at 90°C, and cold-pressed to obtain a positive electrode sheet with a positive active material layer thickness of 114 ⁇ m, and then undergoes lug forming, slitting, etc. The process obtains the positive electrode sheet.
  • Artificial graphite A The coke raw material is firstly pretreated to remove impurities, then pyrolytically granulated to obtain secondary particles with a Dv50 of 15 ⁇ m, and then graphitized at 3000°C for 24 hours, then coated with pitch, and carbonized at 800°C for 10 hours. Artificial graphite A was obtained. Among them, the Dv50 of artificial graphite A is 16 ⁇ m, Dv90 is 26 ⁇ m, Dv10 is 7 ⁇ m, the degree of graphitization is 92.5%, the specific surface area is 0.9m 2 /g, and the compacted density of powder is 1.7g/cm 3 . The mass ratio of the coating layer to artificial graphite A is 3%.
  • Artificial graphite B Coke raw materials are firstly pretreated to remove impurities, then pyrolytically granulated to obtain primary particles with a Dv50 of 14 ⁇ m, and then graphitized at 2800°C for 20 hours to obtain artificial graphite B.
  • Artificial graphite C The coke raw material is firstly pretreated to remove impurities, then pyrolytically granulated to obtain secondary particles with a Dv50 of 10 ⁇ m, and then graphitized at 3000°C for 24 hours, then coated with pitch, and carbonized at 1000°C for 15 hours.
  • the Dv50 of artificial graphite C is 12 ⁇ m
  • Dv90 is 20 ⁇ m
  • Dv10 is 6.5 ⁇ m
  • the degree of graphitization is 91.8%
  • the specific surface area is 0.86m 2 /g
  • the compacted density of powder is 1.6g/cm 3
  • artificial graphite C The mass ratio of the middle coating layer to the artificial graphite C is 5%.
  • Preparation of the first negative electrode slurry artificial graphite A and artificial graphite B are mixed according to a mass ratio of 1:9 to obtain the first negative electrode active material (the mass percentage of artificial graphite A is 10%), and the first negative electrode active Material, conductive agent conductive carbon black, carboxymethyl cellulose (CMC), binder SBR are mixed according to the mass ratio of 96.8:0.8:1.2:1.2, add deionized water as a solvent, and stir under the action of a vacuum mixer until the system is uniform shape to obtain the first negative electrode slurry with a solid content of 66 wt%.
  • the mass percentage of artificial graphite A is 10%
  • the first negative electrode active Material, conductive agent conductive carbon black, carboxymethyl cellulose (CMC), binder SBR are mixed according to the mass ratio of 96.8:0.8:1.2:1.2, add deionized water as a solvent, and stir under the action of a vacuum mixer until the system is uniform shape to obtain the first negative electrode slurry with a solid
  • the Dv50 of the first negative electrode active material is 15 ⁇ m
  • Dv90 is 25 ⁇ m
  • Dv10 is 5.7 ⁇ m
  • the degree of graphitization is 94%
  • the specific surface area is 1.2 m 2 /g
  • the powder compacted density is 1.7 g/cm 3 .
  • Preparation of the second negative electrode slurry mix the second negative electrode active material artificial graphite C, conductive agent conductive carbon black, carboxymethyl cellulose (CMC), and binder SBR according to the mass ratio 96.8:0.8:1.1:1.3, add Deionized water was used as a solvent, and was stirred under the action of a vacuum mixer until the system was uniform, and a second negative electrode slurry with a solid content of 66 wt% was obtained.
  • CMC carboxymethyl cellulose
  • the Dv50 of the second negative electrode active material is 12 ⁇ m
  • Dv90 is 20 ⁇ m
  • Dv10 is 6.5 ⁇ m
  • the degree of graphitization is 91.8%
  • the specific surface area is 0.86m 2 /g
  • the powder compacted density is 1.6g/cm 3 .
  • the mass ratio of the first negative electrode material layer to the second negative electrode material layer is 2:3, the compacted density of the first negative electrode material layer is 1.7 g/cm 3 , and the compacted density of the second negative electrode material layer is 1.6 g/cm 3 . cm 3 , the compacted density of the negative pole piece is 1.65g/cm 3 .
  • the non-aqueous organic solvent ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate are mixed according to a volume ratio of 1:1:1 to obtain an electrolyte solvent, and then the lithium salt LiPF 6 is dissolved in In the mixed solvent, an electrolyte solution with a lithium salt concentration of 1 mol/L is configured.
  • the polyethylene film is selected as the separator, and the appropriate size is obtained by cutting according to the size of the positive pole piece and the negative pole piece before use.
  • Example 1-2 to Example 1-4 are the same as Example 1-1 except that the mass percentages of artificial graphite A and artificial graphite B are adjusted as shown in Table 1.
  • Example 2-1 to Example 2-4 are the same as Example 2-1 except that the Dv50 of the first negative electrode active material, artificial graphite A and artificial graphite B is adjusted as shown in Table 2.
  • Example 3-1 to Example 3-4 are the same as Example 3-1 except that the degree of graphitization of the first negative electrode active material, artificial graphite A and artificial graphite B is adjusted as shown in Table 3.
  • Example 4-1 to Example 4-4 are the same as Example 4-1 except that the degree of graphitization of the first negative electrode active material, artificial graphite A and artificial graphite B is adjusted as shown in Table 4.
  • Example 5-1 to Example 5-4 are the same as Example 5-1 except that the degree of graphitization of the first negative electrode active material, artificial graphite A and artificial graphite B is adjusted as shown in Table 5.
  • Embodiment 6-1 to embodiment 6-4 in addition to adjusting the ratio of the second negative electrode active material Dv50 to the first negative electrode active material Dv50, the Dv50 of the first negative electrode active material and the second negative electrode active material as shown in Table 6, The rest are the same as in Example 6-1.
  • Embodiment 7-1 to embodiment 7-4 in addition to adjusting the graphitization degree of the second negative electrode active material and the ratio of the graphitization degree of the first negative electrode active material as shown in Table 7, the first negative electrode active material and the second negative electrode active material Except the degree of graphitization, the others are the same as in Example 1-1.
  • Example 8-1 to Example 8-4 are the same as Example 1-1 except that the values of X and Y are adjusted as shown in Table 8.
  • Comparative Example 1-1 and Comparative Example 1-2 are the same as Example 1-1 except that the mass percentages of artificial graphite A and artificial graphite B are adjusted as shown in Table 1.
  • Comparative Example 2-1 and Comparative Example 2-2 are the same as Example 2-1 except that Dv50 of the first negative electrode active material, artificial graphite A and artificial graphite B is adjusted as shown in Table 2.
  • Comparative Example 3-1 and Comparative Example 3-2 are the same as Example 3-1 except that the degree of graphitization of the first negative electrode active material, artificial graphite A and artificial graphite B is adjusted as shown in Table 3.
  • Comparative Example 4-1 and Comparative Example 4-2 are the same as Example 4-1 except that the degree of graphitization of the first negative electrode active material, artificial graphite A and artificial graphite B is adjusted as shown in Table 4.
  • Comparative Example 5-1 and Comparative Example 5-2 are the same as Example 5-1 except that the degree of graphitization of the first negative electrode active material, artificial graphite A and artificial graphite B is adjusted as shown in Table 5.
  • Comparative example 6-1 and comparative example 6-2 in addition to adjusting the ratio of the second negative electrode active material Dv50 to the first negative electrode active material Dv50, the Dv50 of the first negative electrode active material and the second negative electrode active material as shown in Table 6, The rest are the same as in Example 6-1.
  • Comparative example 7-1 and comparative example 7-2 except adjusting the graphitization degree of the second negative electrode active material and the ratio of the graphitization degree of the first negative electrode active material as shown in Table 7, the first negative electrode active material and the second negative electrode active material Except the graphitization degree, all the other are identical with embodiment 7-4.
  • Comparative Example 8-1 and Comparative Example 8-2 are the same as Example 1-1 except that the values of X and Y are adjusted as shown in Table 8.
  • the lithium-ion batteries prepared in the above examples and comparative examples were subjected to the following performance tests, and the preparation parameters and performance data of each example are shown in Tables 1-8.
  • Fully charge at 1C then disassemble the negative electrode sheet to observe the lithium deposition on the surface of the negative electrode sheet, if there is no lithium deposition, then fully charge with (n+0.1)C, test again, and increase in increments until the lithium deposition on the negative electrode surface , subtracting 0.1C from the rate at this time is the maximum charging capacity of the lithium-ion battery.
  • the battery is fully charged to 97% state of charge (SOC), stored at 60°C, and the capacity decays to 80% cut-off, and the storage time at this time is recorded, wherein the target storage time is 280 days, and the calculation examples and comparative examples are respectively compared with The ratio of the target storage time is recorded as the storage life. Wherein, the target storage life is 100%.
  • SOC state of charge
  • Example 1-1 to Example 1-4, Comparative Example 1-1 and Comparative Example 1-2 that when the negative electrode sheet of the lithium-ion battery includes the first negative electrode material layer and the second negative electrode material layer, and the first negative electrode material layer includes artificial graphite A and artificial graphite B at the same time, and the second negative electrode material layer includes artificial graphite C, utilizing the high kinetics of artificial graphite A and artificial graphite C, and the high storage performance of artificial graphite C , the obtained lithium-ion battery has a longer storage life and a higher charging rate, that is, it has good comprehensive performance.
  • Example 2-1 to Example 2-4, Comparative Example 2-1 and Comparative Example 2-2 that when the Dv50 of the first negative electrode active material is within the scope of the present application, the obtained lithium Ion batteries have better overall performance.
  • Example 3-1 to Example 3-4, Comparative Example 3-1 and Comparative Example 3-2 that when the graphitization of the first negative electrode active material is too low, although the rate of the lithium ion battery The performance is slightly improved, but the storage life will be deteriorated; when the graphitization of the first negative electrode active material is too high, it will affect the rate performance of the lithium-ion battery.
  • the degree of graphitization of the first negative electrode active material is within the scope of the present application, it is beneficial to balance the rate performance and storage life of the lithium-ion battery, and the obtained lithium-ion battery has better comprehensive performance.
  • Example 4-1 to Example 4-4, Comparative Example 4-1 and Comparative Example 4-2 that when the degree of graphitization of artificial graphite B is constant, artificial graphite A graphite Within the scope of the present application, the resulting lithium-ion battery has better overall performance.
  • Comparative Example 5-1 and Comparative Example 5-2 it can be seen that when the degree of graphitization of artificial graphite A is constant, the degree of graphitization of artificial graphite B is within the scope of the present application Inside, the obtained lithium-ion battery has better comprehensive performance.
  • the degree of graphitization of artificial graphite A mainly affects the rate performance of lithium-ion batteries
  • the degree of graphitization of artificial graphite B mainly affects the storage life of lithium-ion batteries.
  • Example 6-1 to Example 6-4, Comparative Example 6-1 and Comparative Example 6-2 that when the ratio of the second negative active material Dv50 to the first negative active material Dv50 is too large When the ratio of the second negative electrode active material Dv50 to the first negative electrode active material Dv50 is too small, it will affect the rate performance and storage performance of the lithium ion battery at the same time. When the ratio of the second negative electrode active material Dv50 to the first negative electrode active material Dv50 is within the scope of the present application, the obtained lithium ion battery has better overall performance.
  • Example 7-1 to Example 7-4, Comparative Example 7-1 and Comparative Example 7-2 that when the graphitization degree of the second negative electrode active material is the same as that of the first negative electrode active material graphitization degree If the ratio is too small, the storage life of the lithium-ion battery will be affected; when the ratio of the degree of graphitization of the second negative electrode active material to the degree of graphitization of the first negative electrode active material is too large, the rate performance of the lithium-ion battery will be affected. When the ratio of the graphitization degree of the second negative electrode active material to the graphitization degree of the first negative electrode active material is within the scope of the present application, the obtained lithium ion battery has better overall performance.
  • Example 8-1 to Example 8-4 Comparative Example 8-1 and Comparative Example 8-2 that when both the first negative electrode active material and the second negative electrode active material include silicon-based materials, And the mass percentage of the silicon-based material is within the scope of the present application, and the obtained lithium-ion battery has good comprehensive performance. It can be seen from Example 8-1 to Example 8-4 that when the second negative electrode active material includes a silicon-based material and the first negative electrode active material does not include a silicon-based material, it is more beneficial to improve the overall performance of the lithium-ion battery.
  • the present application is not limited to the above-mentioned embodiments.
  • the above-mentioned embodiments are merely examples, and within the scope of the technical solutions of the present application, embodiments that have substantially the same configuration as the technical idea and exert the same effects are included in the technical scope of the present application.
  • various modifications conceivable by those skilled in the art are added to the embodiments, and other forms constructed by combining some components in the embodiments are also included in the scope of the present application. .

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Abstract

本申请提供了一种二次电池和用电装置，二次电池包括负极极片，负极极片包括负极集流体、第一负极材料层和第二负极材料层，第一负极材料层位于负极集流体和第二负极材料层之间，第一负极材料层包括第一负极活性材料，第二负极材料层包括第二负极活性材料，其中，第一负极活性材料包括人造石墨A和人造石墨B，人造石墨A包括二次颗粒且人造石墨A的表面具有无定形碳包覆层，人造石墨B包括一次颗粒且人造石墨B的表面不具有无定形碳包覆层。能够提高二次电池的倍率性能，且二次电池具有较长的使用寿命。

Description

一种二次电池和用电装置 技术领域
本申请涉及电化学领域，特别是涉及一种二次电池和用电装置。
背景技术
二次电池由于具有高能量密度、长循环寿命及无记忆效应等优点而被广泛应用于穿戴设备、智能手机、无人机、电动汽车及大型储能等设备等领域，已成为当今世界最具发展潜力的新型绿色化学电源，但也对二次电池的综合性能提出更高的要求，例如同时具有较长的使用寿命和良好的倍率性能。因此，如何同时二次电池的使用寿命和倍率性能成为亟待解决的问题。
发明内容
本申请是鉴于上述课题而进行的，其目的在于同时提高二次电池的存储寿命和倍率性能。
为了达到上述目的，本申请提供了一种二次电池和用电装置。
本申请的第一方面提供了一种二次电池，其包括负极极片，所述负极极片包括负极集流体、第一负极材料层和第二负极材料层，所述第一负极材料层位于所述负极集流体和所述第二负极材料层之间，所述第一负极材料层包括第一负极活性材料，所述第二负极材料层包括第二负极活性材料，其中，所述第一负极活性材料包括人造石墨A和人造石墨B，所述人造石墨A包括二次颗粒且所述人造石墨A的表面具有无定形碳包覆层，所述人造石墨B包括一次颗粒且所述人造石墨B的表面不具有无定形碳包覆层。
由此，本申请通过在负极集流体上设置第一负极材料层和第二负极材料层，并调控第一负极材料层中的第一负极活性材料，使得第一负极活性材料包括人造石墨A和人造石墨B，能够提高二次电池的倍率性能、延长使用寿命。
在任意实施方式中，所述第一负极活性材料满足以下条件中的至少一者：(1)体积中值粒径Dv50为13μm-18μm，可选为15μm-16μm；(2)粒度分布满足1≤(Dv90-Dv10)/Dv50≤1.6，可选为1.1≤(Dv90-Dv10)/Dv50≤1.5；(3)石墨化度为92.8％-94.8％，可选为93.5％-94.5％；(4)比表面积为1.0m 2/g-1.6m 2/g，可选为1.05m 2/g-1.3m 2/g；(5)粉体压实密度为1.6g/cm 3-1.85g/cm 3，可选为1.7g/cm 3-1.8g/cm 3。第一负极活性材料满足上述条件中的至少一者，有利于同时提高二次电池的存储性能(例如延长存储寿命)和倍率性能。
在任意实施方式中，所述人造石墨A满足以下条件中的至少一者：(1)体积中值粒径Dv50为14μm-20μm，可选为16μm-18μm；(2)粒度分布满足0.8≤(Dv90-Dv10)/Dv50≤1.7，可选地，0.9≤(Dv90-Dv10)/Dv50≤1.4；(3)石墨化度为91.0％-92.8％，可选为91.5％-92.5％；(4)比表面积为0.8m 2/g-1.1m 2/g，可选为0.9m 2/g-1m 2/g；(5)粉体压实密度为1.5g/cm 3-1.8g/cm 3，可选为1.6g/cm 3-1.8g/cm 3；(6)基于所述第一负极活性材料的质量，所述人造石墨A的质量百分含量为10％-70％，可选为30％-50％；(7)所述人造石墨A中的无定形碳包覆层与所述人造石墨A的质量比为1％-5％，可选为3％-4％。人造石墨A满足上述条件中的至少一者，保证存储寿命的同时，有利于提高二次电池的倍率性能。
在任意实施方式中，所述人造石墨B满足以下条件中的至少一者：(1)体积中值粒径Dv50为12μm-16μm，可选为15μm-16μm；粒度分布满足0.5≤(Dv90-Dv10)/Dv50≤1.5；可选地，0.7≤(Dv90-Dv10)/Dv50≤1.1；(2)石墨化度为93.5％-95.5％，可选为94.0％-95.0％；(3)比表面积为1.1m 2/g-1.6m 2/g，可选为1.3m 2/g-1.5m 2/g；(4)粉体压实密度为1.6g/cm 3-1.85g/cm 3，可选1.6g/cm 3-1.8g/cm 3；(5)基于所述第一负极活性材料的质量，所述人造石墨B的质量百分含量为30％-90％，可选为40％-70％。人造石墨B满足上述条件中的至少一者，保证倍率性能的同时，有利于延长二次电池的存储寿命。
在任意实施方式中，所述二次电池满足以下条件中的至少一者：(1)所述第二负极活性材料的体积中值粒径Dv50小于或等于所述第一负极活性材料的体积中值粒径Dv50；可选地，所述第二负极活性材料的体积中值粒径Dv50与述第一负极活性材料的体积中值粒径Dv50的比值为0.5-1；(2)所述第二负极活性材料的粒度分布(DV90-DV10)/DV50与所述第一负极活性材料的粒度分布(DV90-DV10)/DV50的比值为0.8-1.1；(3)所述第二负极活性材料的石墨化度小于所述第一负极活性材料的石墨化度；可选地，所述第二负极活性材料的石墨化度与所述第一负极活性材料的石墨化度的比值为0.95-0.99；(4)所述第二负极活性材料的比表面积小于所述第一负极活性材料的比表面积；可选地，所述第二负极活性材料的比表面积与第一负极活性材料的比表面积的比值为0.6m 2/g-0.8m 2/g；(5)所述第二负极活性材料的粉体压实密度小于所述第一负极活性材料的粉体压实密度；可选地，所述第负极活性材料的粉体压实密度与所述第一负极活性材料的粉体压实密度的比值为0.6-0.95。二次电池满足上述条件中的至少一者，有利于同时提高二次电池的存储性能和倍率性能。
在任意实施方式中，所述第二负极活性材料包括人造石墨C，所述人造石墨C包括二 次颗粒且所述人造石墨C的表面具有无定形碳包覆层；所述人造石墨C中的无定形碳包覆层与所述人造石墨C的质量比为2％-8％，可选为4％-6％。第二负极材料层包括人造石墨C，人造石墨C包覆的无定形碳有利于锂离子嵌入，提高二次电池的倍率性能，此外，在第一负极材料层和第二负极材料层的协同作用下，可以进一步提高二次电池的存储性能和倍率性能。
在任意实施方式中，所述第二负极活性材料包括人造石墨C，所述人造石墨C的Dv50小于所述人造石墨A的Dv50；可选地，所述人造石墨C的Dv50与所述人造石墨A的Dv50的比值为0.5-1。通过调控人造石墨C的Dv50与人造石墨A的Dv50的比值在上述范围内，有利于同时提高二次电池的倍率性能和安全性能。
在任意实施方式中，所述二次电池满足以下条件中的至少一者：(1)所述人造石墨C与所述人造石墨A石墨化度的比值0.95至1；(2)所述人造石墨C与所述人造石墨A比表面积的比值为0.93至1；(3)所述人造石墨A与所述人造石墨C粉体压实密度的比值为1.01-1.3。二次电池满足上述条件中的至少一者，有利于同时提高二次电池的存储性能和倍率性能。
在任意实施方式中，所述第一负极材料层的压实密度大于所述第二负极材料层的压实密度；所述第一负极材料层的压实密度为1.6g/cm 3-1.8g/cm 3，可选为1.6g/cm 3-1.75g/cm 3；所述第二负极材料层的压实密度为1.3g/cm 3-1.6g/cm 3，可选为1.4g/cm 3-1.6g/cm 3。通过调控第一负极材料层和第二负极材料层的压实密度在上述范围内，有利于充分利用第一负极活性材料高压密以及第二负极活性材料高动力学的特性，以同时提高二次电池的存储性能和倍率性能。
在任意实施方式中，所述第一负极材料层和所述第二负极材料层的质量比为2:3至3:2。通过调控第一负极材料层和第二负极材料层的质量比在上述范围内，有利于同时提高二次电池的倍率性能和存储性能。
在任意实施方式中，所述第一负极活性材料和第二负极活性材料均包括硅基材料，基于所述第一负极活性材料的质量，所述硅基材料的质量百分含量记为X；基于所述第二负极活性材料的质量，所述硅基材料的质量百分含量记为Y；所述二次电池满足：X＜Y；可选地，X≤5％，可选地，Y≤10％。硅基材料材料的引入，能够提高第一负极活性材料和第二负极活性材料的克容量，从而有利于提高二次电池的能量密度。通过调控第一负极材料层和第二负极材料层中的硅基颗粒的质量百分含量在上述范围内，能够保证倍率性能的 同时，进一步提高二次电池的能量密度。
本申请的第二方面提供了一种用电装置，包括选自本申请的第二方面的二次电池。
本申请的有益效果：
本申请提供了一种二次电池和用电装置，二次电池包括负极极片，负极极片包括负极集流体、第一负极材料层和第二负极材料层，第一负极材料层位于负极集流体和第二负极材料层之间，第一负极材料层包括第一负极活性材料，第二负极材料层包括第二负极活性材料。本申请通过在负极集流体上设置第一负极材料层和第二负极材料层，并调控第一负极材料层中的第一负极活性材料，使得第一负极活性材料包括人造石墨A和人造石墨B，能够同时提高二次电池的能量密度和倍率性能，以及具有较长的使用寿命。当然，实施本申请的任一产品或方法并不一定需要同时达到以上所述的所有优点。
附图说明
为了更清楚地说明本申请和现有技术的技术方案，下面对实施例和现有技术中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的一些实施例。
图1为本申请一实施方式的负极极片的剖面结构示意图；
图2是本申请一实施方式的二次电池的示意图；
图3是图2所示的本申请一实施方式的二次电池的分解图；
图4是本申请一实施方式的电池模块的示意图；
图5是本申请一实施方式的电池包的示意图；
图6是图5所示的本申请一实施方式的电池包的分解图；
图7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。
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的负极极片、正极极片、二次电池、电池模块、电池包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。
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。
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。
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。
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，可选是顺序进行的。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。
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。
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)。
本申请人在研究过程中发现，在提高二次电池的动力学性能(例如倍率性能)的同时，往往表面包覆物副反应增多，使得二次电池的存储寿命缩短或者循环性能下降，难以满足实际应用中的需求。为了同时提高二次电池的存储性能和倍率性能，提高二次电池的综合性能，例如更长的续航里程、更久的使用寿命，有鉴于此，本申请提供了一种二次电池和用电装置。
需要说明的是，本申请的具体实施方式中，以锂离子电池作为二次电池的例子来解释 本申请，但是本申请的二次电池并不仅限于锂离子电池。
本申请的一个实施方式中，本申请提出了一种二次电池，二次电池包括负极极片，如图1所示，负极极片包括负极集流体21、第一负极材料层22和第二负极材料层23，第一负极材料层22位于负极集流体21和第二负极材料层23之间，第一负极材料层22包括第一负极活性材料(图中未示出)，第二负极材料层23包括第二负极活性材料(图中未示出)，其中，第一负极活性材料包括人造石墨A和人造石墨B，人造石墨A包括二次颗粒且人造石墨A的表面具有无定形碳包覆层，人造石墨B包括一次颗粒且人造石墨B的表面不具有无定形碳包覆层。
本申请人在研究过程中发现，通过在负极集流体上设置第一负极材料层和第二负极材料层，并调控第一负极材料层中的第一负极活性材料，使得第一负极活性材料包括人造石墨A和人造石墨B，能够同时提高二次电池的倍率性能，延长使用寿命。
不限于任何理论，本申请人发现，人造石墨A的表面具有无定形碳包覆层，能够增加锂离子的可插入位点，且晶格间距比较大，嵌锂比较快，这使得人造石墨A有利于提高二次电池的倍率性能；人造石墨B具有规整的石墨晶体结构，结构缺陷少，压实密度大，有利于提高二次电池的能量密度及寿命。从而，在人造石墨A和人造石墨B的协同作用下，保证能量密度的同时，能够同时提高二次电池的倍率性能，并延长使用寿命。
在一些实施方式中，第一负极活性材料的体积中值粒径Dv50为13μm-18μm，可选为15μm-16μm。本申请人发现，当第一负极活性材料的Dv50过小时(例如小于13μm)，负极活性材料容易与电解液发生副反应，造成不可逆的损失，且恶化第一负极材料层压密，从而影响二次电池的倍率性能；当第一负极活性材料的Dv50过大时(例如大于18μm)，且容易影响第一负极材料层的平整性，进而影响二次电池的安全性能。通过调控第一负极活性材料的Dv50值在上述范围内，有利于同时提高倍率性能和安全性能。
在一些实施方式中，第一负极活性材料的粒度分布满足1≤(Dv90-Dv10)/Dv50≤1.6，可选为1.1≤(Dv90-Dv10)/Dv50≤1.5。本申请人发现，通过调控第一负极活性材料的(Dv90-Dv10)/Dv50的值在上述范围内，有利于同时提高倍率性能和安全性能。本申请对第一负极活性材料的Dv90和Dv10没有特别限制，只要满足上述粒径的范围即可，例如，第一负极活性材料的Dv90为24μm-28μm，Dv10为5μm-12μm。
在一些实施方式中，第一负极活性材料的石墨化度为92.8％-94.8％，可选为93.5％-94.5％。本申请人发现，石墨化度能够反映材料的内部结构的规整性等，当第一负 极活性材料的石墨化度过低时(例如低于92.8％)，表明负极活性材料中的人造石墨A炭化量高，使用过程中副反应增多，进而会影响二次电池的存储和循环寿命；当第一负极活性材料的石墨化度过高时(例如大于94.8％)，倍率性能会变差，同时使得第一负极活性材料的制备难度增加，生产成本也增加。通过调控第一负极活性材料的石墨化度在上述范围内，有利于提高二次电池的存储性能和倍率性能并控制其成本。
在一些实施方式中，第一负极活性材料的比表面积为1.0m 2/g-1.6m 2/g，可选为1.05m 2/g-1.3m 2/g。本申请人发现，当第一负极活性材料的比表面积过小时(例如小于1.0m 2/g)，不利于锂离子的脱嵌，从而影响二次电池的倍率性能；当第一负极活性材料的比表面积过大时(例如大于1.6m 2/g)，第一负极活性材料容易与电解液发生副反应，造成不可逆的损失，从而影响二次电池的使用寿命。通过调控第一负极活性材料的比表面积在上述范围内，有利于提高二次电池的使用寿命和倍率性能。
在一些实施方式中，第一负极活性材料的粉体压实密度为1.6g/cm 3-1.85g/cm 3，可选为1.7g/cm 3-1.8g/cm 3。本申请人发现，当第一负极活性材料的粉体压实密度过小时(例如小于1.6g/cm 3)，第一负极活性材料的颗粒与颗粒之间堆砌不紧密，在二次电池循环过程中，容易形成第一负极材料层被损坏的问题，影响二次电池的使用寿命；当第一负极活性材料的粉体压实密度过大时(例如大于1.85g/cm 3)，第一负极活性材料的颗粒与颗粒之间堆砌过于紧密，影响锂离子的脱嵌过程，进而影响二次电池的倍率性能。通过调控第一负极活性材料的粉体压实密度在上述范围内，有利于提高二次电池的倍率性能、延长使用寿命。在本申请中，粉体压实密度是指对应的材料的粉末在2T压力下处理后的密度。
在一些实施方式中，人造石墨A的体积中值粒径Dv50为14μm-20μm，可选为16μm-18μm。本申请人发现，通过调控人造石墨A的Dv50在上述范围内，有利于提高二次电池的倍率性能和安全性能。
在一些实施方式中，人造石墨A的粒度分布满足0.8≤(Dv90-Dv10)/Dv50≤1.7，可选地，0.9≤(Dv90-Dv10)/Dv50≤1.4。本申请人发现，通过调控人造石墨A的(Dv90-Dv10)/Dv50的值在上述范围内，有利于提高二次电池的倍率性能和安全性能。本申请对人造石墨A的Dv90和Dv10没有特别限制，只要满足上述粒径的范围即可，例如，人造石墨A的Dv90为25μm-27μm，Dv10为7μm-11μm。
在一些实施方式中，人造石墨A的石墨化度为91.0％-92.8％，可选为91.5％-92.5％。本申请人发现，通过调控人造石墨A的石墨化度在上述范围内，嵌锂通道适中，不会因为 表面缺陷过多，使得二次电池使用寿命衰减过快，从而有利于提高二次电池的使用寿命和倍率性能并控制其成本。
在一些实施方式中，人造石墨A的比表面积为0.8m 2/g-1.1m 2/g，可选为0.9m 2/g-1m 2/g。本申请人发现，通过调控人造石墨A的比表面积在上述范围内，人造石墨A表面的副反应在合理范围内，有利于提高二次电池的使用寿命。
在一些实施方式中，人造石墨A的粉体压实密度为1.5g/cm 3-1.8g/cm 3，可选为1.6g/cm 3-1.8g/cm 3。不限于任何理论，本申请人发现，通过调控石墨A的粉体压实密度在上述范围内，有利于增加第一负极材料层和第二负极材料层之间的压密差异，提高二次电池的倍率性能、循环性能和存储性能。
在一些实施方式中，人造石墨A中的无定形碳包覆层与人造石墨A的质量比为1％-5％，可选为3％-4％。本申请人发现，通过调控人造石墨A中的无定形碳包覆层与人造石墨A的质量比在上述范围内，增加了第一负极活性材料的活性位点，有利于提高二次电池的倍率性能。
在一些实施方式中，基于第一负极活性材料的质量，人造石墨A的质量百分含量为10％-70％，可选为30％-50％。本申请人发现，当人造石墨A的质量百分含量过低时(例如低于10％)，人造石墨B的含量过高，人造石墨B的嵌锂速度慢，会影响二次电池的倍率性能；当人造石墨A的含量过高时(例如高于70％)，人造石墨B的含量降低，第一负极材料层压密恶化，同时表面缺陷增多，副反应也随之增多，影响二次电池的存储寿命和循环性能。通过调控人造石墨A的质量百分含量在上述范围内，有利于同时提高二次电池的倍率性能、循环性能以及存储性能。
在一些实施方式中，人造石墨B的体积中值粒径Dv50为12μm-16μm，可选为15μm-16μm；粒度分布满足0.5≤(Dv90-Dv10)/Dv50≤1.5；可选地，0.7≤(Dv90-Dv10)/Dv50≤1.1。本申请人发现，通过调控人造石墨B的Dv50和(Dv90-Dv10)/Dv50的值在上述范围内，有利于提高二次电池的存储性能和安全性能。本申请对人造石墨B的Dv90和Dv10没有特别限制，只要满足上述粒径的范围即可，例如，人造石墨B的Dv90为25μm-30μm，Dv10为5μm-10μm。
在一些实施方式中，人造石墨B的石墨化度为93.5％-95.5％，可选为94.0％-95.0％。本申请人发现，通过调控人造石墨B的石墨化度在上述范围内，表面杂碳少，在保证倍率性能的同时，有利于提高二次电池的能量密度并控制其成本。
在一些实施方式中，人造石墨B的比表面积为1.1m 2/g-1.6m 2/g，可选为1.3m 2/g-1.5m 2/g。本申请人发现，通过调控人造石墨B的比表面积在上述范围内，有利于提高二次电池的存储性能。
在一些实施方式中，人造石墨B的粉体压实密度为1.6g/cm 3-1.85g/cm 3，可选为1.6g/cm 3-1.8g/cm 3。本申请人发现，通过调控石墨B的粉体压实密度在上述范围内，有利于提高二次电池的存储性能。
在一些实施方式中，基于第一负极活性材料的质量，人造石墨B的质量百分含量为30％-90％，可选为40％-70％。本申请人发现，当人造石墨B的质量百分含量过低时(例如低于30％)，人造石墨A的含量过高，恶化第一负极材料层压密，会影响二次电池的存储性能；当人造石墨B的含量过高时(例如高于90％)，人造石墨A的含量降低，会影响二次电池的倍率性能。通过调控人造石墨B的质量百分含量在上述范围内，有利于同时提高二次电池的倍率性能和存储性能。
在一些实施方式中，二次电池中的第二负极活性材料的体积中值粒径Dv50小于或等于第一负极活性材料的体积中值粒径Dv50，能够调控第一负极材料层和第二负极材料层的压密，使压密差异化，第一负极材料层压密大于第二材料层，便于提高电解液对第一负极材料层的浸润性。可选地，第二负极活性材料的体积中值粒径Dv50与述第一负极活性材料的体积中值粒径Dv50的比值为0.5-1。本申请人发现，通过调控第二负极活性材料的体积中值粒径Dv50小于或等于第一负极活性材料的体积中值粒径Dv50的比值在上述范围内，有利于保证第一负极材料层和第二负极材料层压密差异化，同时提高二次电池的倍率性能和安全性能。例如，第二负极活性材料的Dv50可以为6.5μm-18μm。
在一些实施方式中，二次电池中的第二负极活性材料的粒度分布(DV90-DV10)/DV50与第一负极活性材料的粒度分布(D V90-D V10)/D V50的比值为0.8-1.1。本申请人发现，通过调控第二负极活性材料的粒度分布(D V90-D V10)/D V50与第一负极活性材料的粒度分布(D V90-D V10)/D V50的比值在上述范围内，有利于同时提高二次电池的倍率性能和安全性能。
在一些实施方式中，二次电池中的第二负极活性材料的石墨化度小于第一负极活性材料的石墨化度，能够充分利用第二负极活性材料的动力学优势。可选地，第二负极活性材料的石墨化度与第一负极活性材料的石墨化度的比值为0.95-0.99。本申请人发现，通过调控第二负极活性材料的石墨化度与第一负极活性材料的石墨化度的比值在上述范围内，有 利于提高二次电池的倍率性能并控制其成本。例如，第二负极活性材料的石墨化度可以为90％-92.12％。
在一些实施方式中，二次电池中的第二负极活性材料的比表面积小于第一负极活性材料的比表面积，能够合理控制负极极片整体的裸露面积。可选地，第二负极活性材料的比表面积与第一负极活性材料的比表面积的比值为0.6-0.8。本申请人发现，通过调控第二负极活性材料的比表面积与第一负极活性材料的比表面积的比值在上述范围内，有利于提高二次电池的使用寿命和倍率性能。例如，第二负极活性材料的比表面积可以为0.7m 2/g-1m 2/g。
在一些实施方式中，二次电池中的第二负极活性材料的粉体压实密度小于第一负极活性材料的粉体压实密度，能够增大第一负极材料层和第二负极材料层的压密差异，有利于电解液更顺畅地经过低压密的第二负极活性材料，到达第一负极材料层，以将第一负极活性材料的优异的动力学性能发挥出来。可选地，第二负极活性材料的粉体压实密度与第一负极活性材料的粉体压实密度的比值为0.6-0.95。本申请人发现，通过调控第二负极活性材料的粉体压实密度与第一负极活性材料的粉体压实密度的比值在上述范围内，有利于提高二次电池的倍率性能、循环性能和存储性能。例如，第二负极活性材料的粉体振实密度可以为1.3g/cm 3-1.65g/cm 3。
在一些实施方式中，第二负极活性材料包括人造石墨C，人造石墨C包括二次颗粒且人造石墨C的表面具有无定形碳包覆层；人造石墨C中的无定形碳包覆层与人造石墨C的质量比为2％-8％，可选为4％-6％。第二负极材料层包括人造石墨C有利于提高二次电池的倍率性能，从而在第一负极材料层和第二负极材料层的协同作用下，可以进一步提高二次电池的存储性能和倍率性能。本申请人发现，通过调控人造石墨C中的无定形碳包覆层与人造石墨C的质量比在上述范围内，有利于提高二次电池的倍率性能。
在一些实施方式中，第二负极活性材料包括人造石墨C，人造石墨C的Dv50小于人造石墨A的Dv50，能够使第二负极材料层压密小于第一负极材料层压密。可选地，人造石墨C的Dv50与人造石墨A的Dv50的比值为0.5-1。本申请人发现，通过调控人造石墨C的Dv50与人造石墨A的Dv50的比值在上述范围内，有利于同时提高二次电池的倍率性能和安全性能。例如，人造石墨C的Dv50可以为7μm-13μm。
在一些实施方式中，二次电池中的人造石墨C与人造石墨A石墨化度的比值0.95-1。本申请人发现，通过调控人造石墨C与人造石墨A的石墨化度的比值在上述范围内，有利 于提高二次电池的存储性能和倍率性能并控制其成本。例如，人造石墨C的石墨化度可以为91％-92％。
在一些实施方式中，二次电池中的人造石墨C人造石墨A比表面积的比值为0.93至1。本申请人发现，通过调控人造石墨C与人造石墨A的比表面积的比值在上述范围内，有利于提高二次电池的倍率性能。例如，人造石墨C的比表面积可以为0.7m 2/g-1.1m 2/g。
在一些实施方式中，二次电池中的人造石墨A与人造石墨C粉体压实密度的比值为1.01-1.3。本申请人发现，通过调控人造石墨A与人造石墨C的粉体压实密度的比值在上述范围内，有利于提高二次电池的倍率性能、循环性能和存储性能。例如，人造石墨C的粉体压实密度可以为1.3g/cm 3-1.6g/cm 3。
在一些实施方式中，第一负极材料层的压实密度大于第二负极材料层的压实密度，从而，电解液可以充分浸润第一负极材料层和第二负极材料层，充分发挥第一负极材料层和第二负极材料层的性能，以同时提高电化学装置的倍率性能和能量密度。第一负极材料层的压实密度为1.6g/cm 3-1.8g/cm 3，可选为1.6.g/cm 3-1.75g/cm 3；第二负极材料层的压实密度为1.3g/cm 3-1.6g/cm 3，可选为1.4g/cm 3-1.6g/cm 3。本申请人发现，通过调控第一负极材料层和第二负极材料层的压实密度在上述范围内，有利于同时提高二次电池的能量密度和倍率性能。
在一些实施方式中，第一负极材料层和第二负极材料层的质量比为2:3至3:2。本申请人发现，当第一负极材料层和第二负极材料层的质量比过小时(例如小于2:3)，也即第一负极材料层的质量较小，第二负极材料层的质量较大，会影响二次电池的存储寿命；当第一负极材料层和第二负极材料层的质量比过大时(例如大于3:2)，也即第一负极材料层的质量较大，第二负极材料层的质量较小，会影响二次电池的倍率性能。通过调控第一负极材料层和第二负极材料层的质量比在上述范围内，有利于同时提高二次电池的倍率性能和能量密度。
在一些实施方式中，第一负极活性材料和第二负极活性材料均包括硅基材料，基于第一负极活性材料的质量，硅基材料的质量百分含量记为X；基于第二负极活性材料的质量，硅基材料的质量百分含量记为Y；二次电池满足：X＜Y；可选地，X≤5％，可选地，Y≤10％，可选为X≤2％，Y≤6％。硅基材料材料的引入，使得第一负极活性材料或第二负极活性材料的克容量发挥提高，从而能够提高二次电池的能量密度。通过调控第一负极材料层和第二负极材料层中的硅基颗粒的质量百分含量在上述范围内，在保证倍率性能的同时， 能够进一步提高二次电池的能量密度。
在一些实施方式中，第一负极活性材料中还可以包括天然石墨。
本申请对人造石墨A和人造石墨C的制备方法没有特别限制，只要能实现本申请的目的即可。例如，制备方法可以包括但不限于以下步骤：将焦原料首先进行预处理去除杂质，然后热解造粒得到二次颗粒，再进行石墨化处理，筛分检验之后表面包覆沥青，高温炭化，得到人造石墨A或人造石墨C。本申请对二次颗粒的粒径大小没有特别限制，只要能实现本申请的目的即可，例如，二次颗粒的体积中值粒径Dv50为10μm-20μm。本申请对上述石墨化处理的温度和时间没有特别限制，只要能实现本申请的目的即可，例如，石墨化处理的温度为2400℃-3000℃，石墨化处理的时间为20h-30h。本申请对高温炭化的温度和时间没有特别限制，只要能实现本申请的目的即可，例如，高温炭化的温度为700℃-1500℃，高温炭化的时间为7h-15h。
本申请对人造石墨B的制备方法没有特别限制，只要能实现本申请的目的即可。例如，制备方法可以包括但不限于以下步骤：焦原料首先进行预处理去除杂质，然后热解造粒得到一次颗粒，再进行石墨化处理，筛分检验之后获得人造石墨B。本申请对一次颗粒的粒径大小没有特别限制，只要能实现本申请的目的即可，例如，一次颗粒的体积中值粒径Dv50为12μm-16μm。本申请对上述石墨化处理的温度和时间没有特别限制，只要能实现本申请的目的即可，例如，石墨化处理的温度为2400℃-3000℃，石墨化处理的时间为18h-30h。
本申请中的人造石墨A或人造石墨C的结构(例如核和包覆层)可以采用本领域已知的设备和方法进行测试。作为示例，可以按照如下步骤操作：选择一定直径的微栅网(如直径3mm)，用尖头镊子夹住微栅网边缘，将其膜面朝上(在灯光下观察显示有光泽的面，即膜面)，轻轻平放在白色滤纸上；取适量石墨颗粒样品(如1g)加入盛有适量乙醇的烧杯中，进行超声振荡10min-30min；用玻璃毛细管吸取，然后滴2滴-3滴该待测样品到微栅网上；烘箱烘烤5min后，将滴有待测样品的微栅网放置到样品台上，用透射电子显微镜(如，日立HF-3300S Cs-corrected STEM)在一定放大倍率(例如60000倍)下进行测试，即可得到待测样品的透射电子显微镜(TEM)图，从TEM照片中则可以观察到核结构和包覆层结构。
本申请中的Dv10、Dv50、Dv90均为本领域公知的参数，可以参照国家标准GB/T 19077-2016(《粒度分布激光衍射法》)，使用激光粒度分析仪(如Malvern Master Size 3000)测定。其中，Dv10是指所测材料累计体积分布百分数达到10％时所对应的粒径；Dv50是 指所测材料累计体积分布百分数达到50％时所对应的粒径；Dv90是指所测材料累计体积分布百分数达到90％时所对应的粒径。
本申请中的石墨化度为本领域公知的含义，可以采用本领域已知的方法测试。例如可以使用X射线衍射仪(例如Bruker D8 Discover)，测试方法参考标准JIS K 0131-1996(《X射线衍射计测量分析的通用规则》)、JB/T 4220-2011(《人造石墨的点阵参数测定方法》)以及GB/T 24533-2019(《锂离子电池石墨类负极材料》)。具体地，先测出材料的d002大小，然后根据公式计算石墨化度(G)＝(0.344-d002)/(0.344-0.3354)×100％，得出所测材料的石墨化度，其中d002是指石墨晶体结构中的层间距，单位为nm。在X射线衍射分析测试中可以采用铜靶作为阳极靶，以CuKα射线为辐射源，射线波长
Figure PCTCN2021130166-appb-000001
扫描2θ角范围为20°-80°，扫描速率可以为4°/min。
本申请中的比表面积为本领域公知的含义，可采用本领域已知的方法测试。例如可以参照国家标准GB/T 19587-2017(《气体吸附BET法测定固态物质比表面积》)，采用氮气吸附比表面积分析测试方法测试，并用BET(Brunauer Emmett Teller)法计算得出，其中氮气吸附比表面积分析测试可以通过美国Micromeritics公司的Tri-Star 3020型比表面积孔径分析测试仪进行测试。
本申请中的粉体压实密度为本领域公知的含义，可采用本领域已知的方法测试。例如可参照国家标准GB/T 24533-2009(《锂离子电池石墨类负极材料》)，使用电子压力试验机(如UTM7305)测试：将质量为M的待测粉末样品放于压实专用模具上(底面积S)，设置不同压力(本申请中可采用2T)，保压30s，卸除压力，等待10s，在设备上读出该压力下粉末压实后的厚度H，计算可得该压力下的粉体压实密度，粉体压实密度＝M/(H×S)。
另外，以下适当参照附图对本申请的二次电池和用电装置，以及包含本申请二次电池的电池模块和电池包进行说明。
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。
[正极极片]
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。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。
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(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(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)上而形成。
在一些实施方式中，正极活性材料可采用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。
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。
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。
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；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
[负极极片]
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，第一负极材料层和第二负极材料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。
在一些实施方式中，所述负极极片的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(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(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)上而形成。
在一些实施方式中，第一负极材料层和第二负极材料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。
在一些实施方式中，第一负极材料层和第二负极材料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。
在一些实施方式中，第一负极材料层和第二负极材料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。
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，例如第一负极活性材料、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，形成第一负极浆料；第二负极活性材料、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，形成第二负极浆料；将第一负极浆料涂覆在负极集流体上，经烘干后得到含有第一负极材料层的负极集流体；然后在第一负极材料层上涂覆第二负极浆料，经烘干、冷压等工序后，即可得到负极极片。
[电解质]
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。
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。
在一些实施方式中，电解质盐可选自六氟磷酸锂、四氟硼酸锂、高氯酸锂、六氟砷酸 锂、双氟磺酰亚胺锂、双三氟甲磺酰亚胺锂、三氟甲磺酸锂、二氟磷酸锂、二氟草酸硼酸锂、二草酸硼酸锂、二氟二草酸磷酸锂及四氟草酸磷酸锂中的至少一种。
在一些实施方式中，溶剂可选自碳酸亚乙酯、碳酸亚丙酯、碳酸甲乙酯、碳酸二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、氟代碳酸亚乙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯、1,4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜中的至少一种。
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。
[隔离膜]
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。
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。
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。
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。
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。
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2是作为一个示例的方形结构的二次电池5。
在一些实施方式中，参照图3，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。
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。
图4是作为一个示例的电池模块4。参照图4，在电池模块4中，多个二次电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个二次电池5容纳于该容纳空间。
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。
图5和图6是作为一个示例的电池包10。参照图5和图6，在电池包10中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体11和下箱体12，上箱体11能够盖设于下箱体12，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
另外，本申请还提供一种用电装置，所述用电装置包括本申请提供的二次电池、电池模块、或电池包中的至少一种。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、储能系统等，但不限于此。
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。
图7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。
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。
实施例
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。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。
实施例1-1
<正极极片的制备>
将正极活性材料LiNi 0.8Co 0.1Mn 0.1O 2、导电剂导电碳黑、粘结剂聚偏氟乙烯(PVDF)按质量比98∶1∶1混合，然后加入N-甲基吡咯烷酮(NMP)作为溶剂，在真空搅拌机作用下搅拌至体系呈均一状，得到固含量为75wt％的正极浆料。将正极浆料均匀涂覆在厚度为13μm的铝箔的一个表面上，90℃条件下烘干，冷压后得到正极活性材料层厚度为114μm的正极极片，然后经过极耳成型、分切等工序得到正极极片。
<负极活性材料的制备>
人造石墨A：将焦原料首先进行预处理去除杂质，然后热解造粒得到Dv50为15μm的二次颗粒，再在3000℃石墨化处理24h，然后包覆沥青，在800℃高温炭化处理10h，得到人造石墨A。其中，人造石墨A的Dv50为16μm、Dv90为26μm、Dv10为7μm、石墨化度为92.5％、比表面积为0.9m 2/g、粉体压实密度为1.7g/cm 3，人造石墨A中的包覆层与人造石墨A的质量比为3％。
人造石墨B：焦原料首先进行预处理去除杂质，然后热解造粒得到Dv50为14μm的一次颗粒，再在2800℃石墨化处理20h，得到人造石墨B。
人造石墨C：将焦原料首先进行预处理去除杂质，然后热解造粒得到Dv50为10μm的二次颗粒，再在3000℃石墨化处理24h，然后包覆沥青，在1000℃高温炭化处理15h。其中，人造石墨C的Dv50为12μm、Dv90为20μm、Dv10为6.5μm、石墨化度为91.8％、比表面积为0.86m 2/g、粉体压实密度为1.6g/cm 3，人造石墨C中包覆层的质量与人造石墨C的质量比为5％。
<负极极片的制备>
第一负极浆料的制备：将人造石墨A和人造石墨B按照质量比为1:9进行混合得到第一负极活性材料(人造石墨A的质量百分含量为10％)，将第一负极活性材料、导电剂导电炭黑、羧甲基纤维素(CMC)、粘结剂SBR按照质量比96.8:0.8:1.2:1.2混合，加入去离子水作为溶剂，在真空搅拌机作用下搅拌至体系呈均一状，得到固含量为66wt％的第一负极浆料。其中，第一负极活性材料的Dv50为15μm、Dv90为25μm、Dv10为5.7μm、石墨化度为94％、比表面积为1.2m 2/g、粉体压实密度为1.7g/cm 3。
第二负极浆料的制备：将第二负极活性材料人造石墨C、导电剂导电炭黑、羧甲基纤维素(CMC)、粘结剂SBR按照质量比96.8:0.8:1.1:1.3混合，加入去离子水作为溶剂，在真空搅拌机作用下搅拌至体系呈均一状，得到固含量为66wt％的第二负极浆料。其中，第二负极活性材料的Dv50为12μm、Dv90为20μm、Dv10为6.5μm、石墨化度为91.8％、比表面积为0.86m 2/g、粉体压实密度为1.6g/cm 3。
将第一负极浆料涂覆在厚度为8μm的负极集流体铜箔的一个表面上，经烘干后得到含有第一负极材料层的负极集流体；然后在第一负极材料层上涂覆第二负极浆料，经110℃条件下烘干后得到含有第一负极材料层和第二负极材料层的负极集流体。在负极集流体的另一个表面上重复上述步骤，冷压后得到第一负极活性材料层厚度为54μm、第二负极活性材料层厚度为81μm的负极极片，然后经过极耳成型、分切等工序得到负极极片。其中，第一负极材料层和第二负极材料层的质量比为2:3，第一负极材料层的压实密度为1.7g/cm 3，第二负极材料层的压实密度为1.6g/cm 3，负极极片压实密度为1.65g/cm 3。
<电解液的制备>
在含水量小于10ppm的环境下，将非水有机溶剂碳酸乙烯酯、碳酸甲乙酯、碳酸二乙酯按照体积比1:1:1进行混合得到电解液溶剂，随后将锂盐LiPF 6溶解于混合后的溶剂中，配置成锂盐浓度为1mol/L的电解液。
<隔离膜的制备>
选择聚乙烯膜作为隔离膜，使用前根据正极极片和负极极片的尺寸经分切得到合适的尺寸。
<锂离子电池的制备>
将上述正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正极极片和负极极片之间起到隔离作用，然后卷绕得到电极组件；将电极组件置于外包装壳中，干燥后注入电解液，经过真空封装、静置、化成、整形等工序，得到锂离子电池。
实施例1-2至实施例1-4，除了按照表1所示调整人造石墨A和人造石墨B的质量百分含量以外，其余与实施例1-1相同。
实施例2-1至实施例2-4，除了按照表2所示调整第一负极活性材料、人造石墨A和人造石墨B的Dv50以外，其余与实施例2-1相同。
实施例3-1至实施例3-4，除了按照表3所示调整第一负极活性材料、人造石墨A和人造石墨B的石墨化度以外，其余与实施例3-1相同。
实施例4-1至实施例4-4，除了按照表4所示调整第一负极活性材料、人造石墨A和人造石墨B的石墨化度以外，其余与实施例4-1相同。
实施例5-1至实施例5-4，除了按照表5所示调整第一负极活性材料、人造石墨A和人造石墨B的石墨化度以外，其余与实施例5-1相同。
实施例6-1至实施例6-4，除了按照表6所示调整第二负极活性材料Dv50与第一负极活性材料Dv50的比值、第一负极活性材料和第二负极活性材料的Dv50以外，其余与实施例6-1相同。
实施例7-1至实施例7-4，除了按照表7所示调整第二负极活性材料石墨化度与第一负极活性材料石墨化度的比值、第一负极活性材料和第二负极活性材料的石墨化度以外，其余与实施例1-1相同。
实施例8-1至实施例8-4，除了按照表8所示调整X和Y的值以外，其余与实施例1-1相同。
对比例1-1和对比例1-2，除了按照表1所示调整人造石墨A和人造石墨B的质量百分含量以外，其余与实施例1-1相同。
对比例2-1和对比例2-2，除了按照表2所示调整第一负极活性材料、人造石墨A和人造石墨B的Dv50以外，其余与实施例2-1相同。
对比例3-1和对比例3-2，除了按照表3所示调整第一负极活性材料、人造石墨A和人造石墨B的石墨化度以外，其余与实施例3-1相同。
对比例4-1和对比例4-2，除了按照表4所示调整第一负极活性材料、人造石墨A和人造石墨B的石墨化度以外，其余与实施例4-1相同。
对比例5-1和对比例5-2，除了按照表5所示调整第一负极活性材料、人造石墨A和人造石墨B的石墨化度以外，其余与实施例5-1相同。
对比例6-1和对比例6-2，除了按照表6所示调整第二负极活性材料Dv50与第一负极活性材料Dv50的比值、第一负极活性材料和第二负极活性材料的Dv50以外，其余与实施例6-1相同。
对比例7-1和对比例7-2，除了按照表7所示调整第二负极活性材料石墨化度与第一负极活性材料石墨化度的比值、第一负极活性材料和第二负极活性材料的石墨化度以外，其余与实施例7-4相同。
对比例8-1和对比例8-2，除了按照表8所示调整X和Y的值以外，其余与实施例1-1 相同。
将上述实施例和对比例制备得到的锂离子电池进行如下性能测试，各实施例的制备参数及性能数据如表1-8所示。
充电能力测试：
在25℃下，将实施例和对比例制备得到锂离子电池以nC满充(例如n＝0.1、0.2、0.3、0.4、0.5)，以1C满放，如此循环10圈，再将锂离子电池以1C满充，然后拆解负极极片观察负极极片表面的析锂情况，若未析锂则以(n+0.1)C满充，再次进行测试，以此递增，直至负极表面析锂为止，以此时的倍率减去0.1C即为锂离子电池最大的充电能力。
能量密度(W)测试：
在25℃下，以0.33C倍率满充，以0.33C满放，循环3圈，取最后一圈放电能量(E)，使用电子天平称重锂离子电池的质量(m)，W＝E/m。
存储寿命测试：
将电池满充至97％荷电状态(SOC)，在60℃下存储，容量衰减到80％截止，记录此时的存储时间，其中目标存储时间为280天，计算实施例与对比例分别与目标存储时间的比值，记为存储寿命。其中，目标存储寿命则为100％。
循环性能测试：
在25℃下，将实施例和对比例制备的锂离子电池以3C倍率充电，以1C倍率放电，进行3％-97％SOC循环测试，直至锂离子电池的容量小于初始容量的80％，记录循环圈数，其中目标循环圈数2000圈，计算实施例与对比例分别与目标循环时间的比值，记为循环性能。其中，目标循环寿命则为100％。
表1
Figure PCTCN2021130166-appb-000002
注：表1中的“/”表示不存在对应的参数或物质。 表2
Figure PCTCN2021130166-appb-000003
表3
Figure PCTCN2021130166-appb-000004
表4
Figure PCTCN2021130166-appb-000005
表5
Figure PCTCN2021130166-appb-000006
表6
Figure PCTCN2021130166-appb-000007
表7
Figure PCTCN2021130166-appb-000008
表8
Figure PCTCN2021130166-appb-000009
参考表1，从实施例1-1至实施例1-4、对比例1-1和对比例1-2可以看出，当锂离子电池的负极极片包括第一负极材料层和第二负极材料层，且第一负极材料层同时包括人造石墨A和人造石墨B，第二负极材料层包括人造石墨C，利用人造石墨A和人造石墨C的高动力学，以及人造石墨C的高存储性能，得到的锂离子电池的存储寿命更长、充电倍率更高，也即具有良好的综合性能。
从实施例1-1至实施例1-4、对比例1-3和对比例1-4可以看出，当人造石墨A的质量 百分含量不在本申请的范围内，锂离子电池的存储寿命和倍率性能难以兼顾，其综合性能差于实施例得到的锂离子电池。当人造石墨A的质量百分含量在本申请的范围内，得到的锂离子电池具有更好的综合性能。
参考表2，从实施例2-1至实施例2-4、对比例2-1和对比例2-2可以看出，当第一负极活性材料的Dv50在本申请的范围内，得到的锂离子电池具有更好的综合性能。
参考表3，从实施例3-1至实施例3-4、对比例3-1和对比例3-2可以看出，当第一负极活性材料石墨化度过低，虽然锂离子电池的倍率性能略有提升，但是存储寿命会恶化；当第一负极活性材料石墨化度过高，会影响锂离子电池的倍率性能。当第一负极活性材料的石墨化度在本申请的范围内，有利于平衡锂离子电池的倍率性能和存储寿命，得到的锂离子电池具有更好的综合性能。
参考表4和表5，从实施例4-1至实施例4-4、对比例4-1和对比例4-2可以看出，当人造石墨B的石墨化度不变，人造石墨A石墨化度在本申请的范围内，得到的锂离子电池具有更好的综合性能。从实施例5-1至实施例5-4、对比例5-1和对比例5-2可以看出，当人造石墨A的石墨化度不变，人造石墨B石墨化度在本申请的范围内，得到的锂离子电池具有更好的综合性能。另外还可以看出，人造石墨A的石墨化度主要影响锂离子电池的倍率性能，人造石墨B的石墨化度主要影响锂离子电池的存储寿命。
参考表6，从实施例6-1至实施例6-4、对比例6-1和对比例6-2可以看出，当第二负极活性材料Dv50与第一负极活性材料Dv50的比值过大时，会影响锂离子电池的倍率性能；当第二负极活性材料Dv50与第一负极活性材料Dv50的比值过小时，会同时影响锂离子电池的倍率性能和存储性能。当第二负极活性材料Dv50与第一负极活性材料Dv50的比值在本申请的范围内，得到的锂离子电池具有更好的综合性能。
参考表7，从实施例7-1至实施例7-4、对比例7-1和对比例7-2可以看出，当第二负极活性材料石墨化度与第一负极活性材料石墨化度的比值过小时，会影响锂离子电池的存储寿命；当第二负极活性材料石墨化度与第一负极活性材料石墨化度的比值过大时，会影响锂离子电池的倍率性能。当第二负极活性材料石墨化度与第一负极活性材料石墨化度的比值在本申请的范围内，得到的锂离子电池具有更好的综合性能。
参考表8，从实施例8-1至实施例8-4、对比例8-1和对比例8-2可以看出，当第一负极活性材料和第二负极活性材料均包括硅基材料，且硅基材料的质量百分含量在本申请的范围内，得到的锂离子电池具有良好的综合性能。从实施例8-1至实施例8-4可以看出， 当第二负极活性材料包括硅基材料且第一负极活性材料不包括硅基材料时，更有利于提高锂离子电池的综合性能。
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。

Claims (12)

  1. 一种二次电池，其包括负极极片，所述负极极片包括负极集流体、第一负极材料层和第二负极材料层，所述第一负极材料层位于所述负极集流体和所述第二负极材料层之间，所述第一负极材料层包括第一负极活性材料，所述第二负极材料层包括第二负极活性材料，其中，
    所述第一负极活性材料包括人造石墨A和人造石墨B，所述人造石墨A包括二次颗粒且所述人造石墨A的表面具有无定形碳包覆层，所述人造石墨B包括一次颗粒且所述人造石墨B的表面不具有无定形碳包覆层。
  2. 根据权利要求1所述的二次电池，其中，所述第一负极活性材料满足以下条件中的至少一者：
    (1)体积中值粒径Dv50为13μm-18μm，可选为15μm-16μm；
    (2)粒度分布满足：1≤(Dv90-Dv10)/Dv50≤1.6，可选为1.1≤(Dv90-Dv10)/Dv50≤1.5；
    (3)石墨化度为92.8％-94.8％，可选为93.5％-94.5％；
    (4)比表面积为1.0m 2/g-1.6m 2/g，可选为1.05m 2/g-1.3m 2/g；
    (5)粉体压实密度为1.6g/cm 3-1.85g/cm 3，可选为1.7g/cm 3-1.8g/cm 3。
  3. 根据权利要求1或2所述的二次电池，其中，所述人造石墨A满足以下条件中的至少一者：
    (1)体积中值粒径Dv50为14μm-20μm，可选为16μm-18μm；
    (2)粒度分布满足：0.8≤(Dv90-Dv10)/Dv50≤1.7，可选地，0.9≤(Dv90-Dv10)/Dv50≤1.4；
    (3)石墨化度为91.0％-92.8％，可选为91.5％-92.5％；
    (4)比表面积为0.8m 2/g-1.1m 2/g，可选为0.9m 2/g-1m 2/g；
    (5)粉体压实密度为1.5g/cm 3-1.8g/cm 3，可选为1.6m 2/g-1.8m 2/g；
    (6)基于所述第一负极活性材料的质量，所述人造石墨A的质量百分含量为10％-70％，可选为30％-50％；
    (7)所述人造石墨A中的无定形碳包覆层与所述人造石墨A的质量比为1％-5％，可选为3％-4％。
  4. 根据权利要求1-3任一项所述的二次电池，其中，所述人造石墨B满足以下条件 中的至少一者：
    (1)体积中值粒径Dv50为12μm-16μm，可选为15μm-16μm；粒度分布满足0.5≤(Dv90-Dv10)/Dv50≤1.5；优选地，0.7≤(Dv90-Dv10)/Dv50≤1.1；
    (2)石墨化度为93.5％-95.5％，优选为94.0％-95.0％；
    (3)比表面积为1.1m 2/g-1.6m 2/g，优选为1.3m 2/g-1.5m 2/g；
    (4)粉体压实密度为1.6g/cm 3-1.85g/cm 3，优选为1.6g/cm 3-1.8g/cm 3；
    (5)基于所述第一负极活性材料的质量，所述人造石墨B的质量百分含量为30％-90％，可选为40％-70％。
  5. 根据权利要求1-4任一项所述的二次电池，其中，所述二次电池满足以下条件中的至少一者：
    (1)所述第二负极活性材料的体积中值粒径Dv50小于或等于所述第一负极活性材料的体积中值粒径Dv50；优选地，所述第二负极活性材料的体积中值粒径Dv50与述第一负极活性材料的体积中值粒径Dv50的比值为0.5-1；
    (2)所述第二负极活性材料的粒度分布(DV90-DV10)/DV50与所述第一负极活性材料的粒度分布(DV90-DV10)/DV50的比值为0.8-1.1；
    (3)所述第二负极活性材料的石墨化度小于所述第一负极活性材料的石墨化度；可选地，所述第二负极活性材料的石墨化度与所述第一负极活性材料的石墨化度的比值为0.95-0.99；
    (4)所述第二负极活性材料的比表面积小于所述第一负极活性材料的比表面积；可选地，所述第二负极活性材料的比表面积与第一负极活性材料的比表面积的比值为0.6 0.8；
    (5)所述第二负极活性材料的粉体压实密度小于所述第一负极活性材料的粉体压实密度；可选地，所述第二负极活性材料的粉体压实密度与所述第一负极活性材料的粉体压实密度的比值为0.67-0.95。
  6. 根据权利要求1-5任一项所述的二次电池，其中，所述第二负极活性材料包括人造石墨C，所述人造石墨C包括二次颗粒且所述人造石墨C的表面具有无定形碳包覆层；所述人造石墨C中的无定形碳包覆层与所述人造石墨C的质量比为2％-8％。
  7. 根据权利要求6所述的二次电池，其中，所述第二负极活性材料包括人造石墨C，所述人造石墨C的Dv50小于所述人造石墨A的Dv50；可选地，所述人造石墨C的Dv50与所述人造石墨A的Dv50的比值为0.5-1。
  8. 根据权利要求6-7任一项所述的二次电池，其中，所述二次电池满足以下条件中的至少一者：
    (1)所述人造石墨C与所述人造石墨A石墨化度的比值0.95-1；
    (2)所述人造石墨C与所述人造石墨A比表面积的比值为0.93-1；
    (3)所述人造石墨A与所述人造石墨C粉体压实密度的比值为1.01-1.3。
  9. 根据权利要求1-8任一项所述的二次电池，其中，所述第一负极材料层的压实密度大于所述第二负极材料层的压实密度；
    所述第一负极材料层的压实密度为1.6g/cm 3-1.8g/cm 3，可选为1.6g/cm 3-1.75g/cm 3；
    所述第二负极材料层的压实密度为1.3g/cm 3-1.6g/cm 3，可选为1.4g/cm 3-1.6g/cm 3。
  10. 根据权利要求1-9任一项所述的二次电池，其中，所述第一负极材料层和所述第二负极材料层的质量比为2:3至3:2。
  11. 根据权利要求1-10任一项所述的二次电池，其中，所述第一负极活性材料和所述第二负极活性材料均包括硅基材料，基于所述第一负极活性材料的质量，所述硅基材料的质量百分含量记为X；基于所述第二负极活性材料的质量，所述硅基材料的质量百分含量记为Y；
    所述二次电池满足：X＜Y；
    可选地，X≤5％；
    可选地，Y≤10％。
  12. 一种用电装置，其包括权利要求1-11任一项所述的二次电池。
PCT/CN2021/130166 2021-11-11 2021-11-11 一种二次电池和用电装置 Ceased WO2023082157A1 (zh)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2024250710A1 (zh) * 2023-06-08 2024-12-12 深圳海辰储能科技有限公司 一种负极极片、电池、电池包及用电设备
WO2025098303A1 (zh) * 2023-11-09 2025-05-15 宁德新能源科技有限公司 二次电池和用电设备
WO2025138121A1 (zh) * 2023-12-25 2025-07-03 惠州锂威新能源科技有限公司 一种负极活性材料及其制备方法和应用

Families Citing this family (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN119833580B (zh) * 2023-11-30 2025-09-02 宁德时代新能源科技股份有限公司 负极活性材料、负极极片、电池和用电装置
CN119852481B (zh) * 2023-11-30 2026-03-03 宁德时代新能源科技股份有限公司 二次电池以及用电装置
CN119852480A (zh) * 2023-11-30 2025-04-18 宁德时代新能源科技股份有限公司 二次电池以及用电装置
CN119852401A (zh) * 2023-12-07 2025-04-18 宁德时代新能源科技股份有限公司 石墨负极活性材料及其制备方法、含有其的二次电池和用电装置
CN119833585A (zh) * 2024-01-30 2025-04-15 宁德时代新能源科技股份有限公司 负极活性材料及其制备方法、以及包含其的负极极片、电池及用电装置
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CN121460572A (zh) * 2024-07-24 2026-02-03 万华化学集团电池科技有限公司 一种石墨负极活性材料及其制备方法和倍率性能的评价方法
CN119852319A (zh) * 2024-08-30 2025-04-18 宁德时代新能源科技股份有限公司 负极极片、二次电池、用电装置、人造石墨及其制备方法
WO2026065421A1 (zh) * 2024-09-30 2026-04-02 厦门新能安科技有限公司 一种负极极片、二次电池和用电设备
CN119833724A (zh) * 2025-02-17 2025-04-15 宁德时代新能源科技股份有限公司 锂离子二次电池及其制备方法、用电装置

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110867560A (zh) * 2018-08-28 2020-03-06 宁德时代新能源科技股份有限公司 一种负极极片及二次电池
CN110915033A (zh) * 2017-12-01 2020-03-24 株式会社Lg化学 用于锂二次电池的负极和包括该负极的锂二次电池
CN111129503A (zh) * 2018-10-31 2020-05-08 宁德时代新能源科技股份有限公司 一种负极极片以及二次电池
CN113410469A (zh) * 2018-10-31 2021-09-17 宁德时代新能源科技股份有限公司 一种负极极片和二次电池以及电动汽车

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103733391B (zh) * 2011-07-29 2016-05-18 丰田自动车株式会社 锂离子二次电池
CN106898738B (zh) * 2015-12-18 2019-07-23 华为技术有限公司 一种锂离子二次电池负极活性材料及制备方法、锂离子二次电池负极极片和锂离子二次电池
KR102519441B1 (ko) * 2017-12-22 2023-04-07 삼성에스디아이 주식회사 리튬 이차전지용 음극활물질, 이를 포함한 음극, 및 리튬 이차전지

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110915033A (zh) * 2017-12-01 2020-03-24 株式会社Lg化学 用于锂二次电池的负极和包括该负极的锂二次电池
CN110867560A (zh) * 2018-08-28 2020-03-06 宁德时代新能源科技股份有限公司 一种负极极片及二次电池
CN111129503A (zh) * 2018-10-31 2020-05-08 宁德时代新能源科技股份有限公司 一种负极极片以及二次电池
CN113410469A (zh) * 2018-10-31 2021-09-17 宁德时代新能源科技股份有限公司 一种负极极片和二次电池以及电动汽车

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of EP4207372A4 *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2024250710A1 (zh) * 2023-06-08 2024-12-12 深圳海辰储能科技有限公司 一种负极极片、电池、电池包及用电设备
WO2025098303A1 (zh) * 2023-11-09 2025-05-15 宁德新能源科技有限公司 二次电池和用电设备
WO2025138121A1 (zh) * 2023-12-25 2025-07-03 惠州锂威新能源科技有限公司 一种负极活性材料及其制备方法和应用

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