WO2025118596A1 - 二次电池及用电装置 - Google Patents

二次电池及用电装置 Download PDF

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Publication number
WO2025118596A1
WO2025118596A1 PCT/CN2024/104988 CN2024104988W WO2025118596A1 WO 2025118596 A1 WO2025118596 A1 WO 2025118596A1 CN 2024104988 W CN2024104988 W CN 2024104988W WO 2025118596 A1 WO2025118596 A1 WO 2025118596A1
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Prior art keywords
negative electrode
graphite material
secondary battery
film layer
graphite
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French (fr)
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马建军
何立兵
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Contemporary Amperex Technology Co Ltd
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Contemporary Amperex Technology Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • 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 disclosure relates to the field of battery technology, and in particular to a secondary battery and an electrical device.
  • secondary batteries have been widely used in energy storage power systems such as hydropower, thermal, wind and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.
  • An object of the present disclosure is to provide a secondary battery and an electric device, which can improve the cycle life of the secondary battery.
  • a first aspect of the present disclosure provides a secondary battery, characterized in that it includes a negative electrode plate, the negative electrode plate includes a negative electrode current collector and a negative electrode film layer formed on at least one surface of the negative electrode current collector, the negative electrode film layer includes a graphite material, and the tap density of the graphite material is 1.2g/cm 3 -1.4g/cm 3 ; and the difference between the compaction density of the negative electrode film layer and the tap density of the graphite material is greater than or equal to 0.15g/cm 3 .
  • the above-mentioned pole piece will have uneven local lithium ion concentration distribution when stored at high temperature or after multiple charge and discharge, resulting in lithium precipitation and capacity decay, and the capacity retention rate is greatly deteriorated.
  • the disclosed embodiments break the prejudice in the prior art by using a high tap density negative electrode film layer in combination with a high tap density graphite material.
  • the secondary battery can fully utilize the advantages of the high tap density graphite material with good cycle performance, and can also reduce the probability of severe black spots forming on the negative electrode after the battery is fully charged, and reduce the probability of the battery's performance "diving" after long-cycle cycling or high-temperature storage, thereby improving the battery's cycle stability and high-temperature storage stability.
  • the compaction density of the negative electrode film layer is less than or equal to 1.55 g/cm 3 and greater than or equal to 1.40g/ cm3 .
  • the compaction density of the electrode film layer within a reasonable range can not only reduce the probability of severe black spots forming on the electrode after the battery is fully charged, but also improve the integrity of the graphite material particles during the cold pressing process, maintain the pore structure inside the electrode and the lower electrode tortuosity, and take into account the long cycle stability and high dynamic performance of the secondary battery.
  • the graphite material includes primary particles.
  • the number of primary particles in the graphite material accounts for greater than or equal to 85% based on the total number of particles in the graphite material. In some exemplary embodiments, the number of primary particles in the graphite material accounts for 85%-100% based on the total number of particles in the graphite material.
  • primary particles can effectively reduce the grain boundary content, reduce the probability of side reactions between graphite materials and electrolytes, improve the uniformity of pole pieces, and improve the cycle stability of secondary batteries through a high proportion of primary particle content.
  • the Dv1 of the graphite material is 1.5 ⁇ m to 3.0 ⁇ m. In some embodiments, the Dv1 of the graphite material is 1.6 ⁇ m to 2.8 ⁇ m.
  • the graphite material has a Dv1 within a suitable range, which can not only make the negative electrode film layer have a certain proportion of fine powder, that is, small-particle graphite material, which is beneficial to improve the electrical contact of the negative electrode film layer, improve the kinetic performance, make the formation gas production end SOC earlier, reduce the probability of serious black spots in the battery preparation process and the probability of "diving" in the electrochemical performance of the battery during recycling or storage; it can also reduce the probability of small-particle graphite material blocking the pores of the negative electrode film layer, maintain normal pole piece pores so that the electrolyte has high wettability, reduce the risk of negative electrode lithium plating, and improve the battery's cycle stability and high-temperature storage stability.
  • the Dv50 of the graphite material is 12 ⁇ m to 16 ⁇ m. In some embodiments, the Dv50 of the graphite material is 13 ⁇ m to 15 ⁇ m.
  • the graphite material has a large volume distribution particle size Dv50, which is beneficial to the formation of a reasonable pore structure between the particles of the negative electrode film layer, which is beneficial to the electrolyte to fully infiltrate the negative electrode plate, reduce the possibility of local polarization of the plate, and reduce the impact of black spots on the negative electrode on the cycle life and storage stability of the battery.
  • the particle size distribution of the graphite material (Dv90-Dv10)/Dv50 is 1.2-1.7. In some embodiments, the particle size distribution of the graphite material (Dv90-Dv10)/Dv50 is 1.35-1.60.
  • Graphite materials with a particle size distribution within the above range can reduce the uneven distribution of active ions in the graphite material caused by the large difference in particle size, reduce the side reaction between small-particle graphite materials and electrolytes, and improve the cycle performance and storage stability of secondary batteries.
  • the specific surface area of the graphite material is 0.6 m 2 /g to 1.5 m 2 /g. In some embodiments, the specific surface area of the graphite material is 0.9 m 2 /g to 1.4 m 2 /g.
  • Graphite material has a small specific surface area, which can reduce the probability of side reactions between graphite material and electrolyte and improve the cycle performance and storage stability of the battery.
  • the oil absorption value of the graphite material does not exceed 45 ml/100 g. In some embodiments, the oil absorption value of the graphite material is 30 ml/100 g-45 ml/100 g.
  • the oil absorption value of graphite materials can reflect the dispersibility of graphite materials in negative electrode slurry to a certain extent.
  • the high oil absorption value of graphite materials means that the graphite materials need to be infiltrated with more dispersants, such as sodium carboxymethyl cellulose, during the dispersion process. The slurry is more likely to settle, resulting in unstable quality during the electrode coating process and uneven thickness of the electrode after cold pressing.
  • Graphite materials with oil absorption values within the above range can not only have good wettability for the electrolyte, so that the secondary battery has good dynamic performance and cycle stability; they can also maintain good particle dispersion during the stirring process and are not easily affected by graphite. Excessive adsorption of the dispersant by the material causes slurry sedimentation, which makes the electrode coating have a wider process window and the electrode has good uniformity.
  • the graphite material has a degree of graphitization of 88% to 93%. In some embodiments, the graphite material has a degree of graphitization of 89% to 92%.
  • Controlling the degree of graphitization within the above range can not only take into account the capacity of the graphite material, but also achieve a smaller volume change of the graphite active material during the charging process, which is beneficial to improving the cycle stability.
  • the surface density of the negative electrode film layer is 7 mg/cm 2 to 14 mg/cm 2 . In some embodiments, the surface density of the negative electrode film layer is 9 mg/cm 2 to 12 mg/cm 2 .
  • the graphite material includes artificial graphite.
  • a second aspect of the present disclosure provides an electric device, which includes the secondary battery of the first aspect of the present disclosure.
  • FIG. 1 is a schematic diagram of one embodiment of a secondary battery of the present disclosure.
  • FIG. 2 is an exploded schematic diagram of an embodiment of a secondary battery of the present disclosure.
  • FIG. 3 is a schematic diagram of an embodiment of a battery module of the present disclosure.
  • FIG. 4 is a schematic diagram of an embodiment of a battery pack of the present disclosure.
  • FIG. 5 is an exploded schematic diagram of the embodiment of the battery pack shown in FIG. 4 .
  • FIG. 6 is a schematic diagram of an embodiment of an electric device including the secondary battery of the present disclosure as a power source.
  • range disclosed in the present disclosure is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range.
  • the range defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60-120 and 80-110 is listed for a particular parameter, it is understood that a range of 60-110 and 80-120 is also expected.
  • the numerical range "ab” represents an abbreviation of any real number combination between a and b. , where a and b are both real numbers.
  • the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations.
  • a parameter is expressed as an integer ⁇ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.
  • the “include” and “comprising” mentioned in the present disclosure represent open or closed forms.
  • the “include” and “comprising” may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.
  • the term "or” is inclusive.
  • the phrase “A or B” means “A, B, or both A and B”. More specifically, any of the following conditions satisfies the condition "A or B”: 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 values of the parameters mentioned in the present disclosure can be measured using various test methods commonly used in the art, for example, they can be measured according to the test methods given in the present disclosure.
  • active ions refers to ions that can be intercalated and extracted back and forth between the positive electrode and the negative electrode of a secondary battery, including but not limited to lithium ions.
  • the terms “plurality” and “multiple” refer to two or more.
  • Lithium battery energy storage system is a device that uses lithium batteries for energy storage. It can store energy generated by renewable energy sources such as solar photovoltaics and wind power, and can also serve as an auxiliary facility for the power grid. Compared with power batteries, energy storage batteries pay more attention to the cycle life of batteries.
  • the present disclosure provides a secondary battery, including a negative electrode plate, wherein the negative electrode plate includes a negative electrode current collector A body and a negative electrode film layer formed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer comprises a graphite material, the tap density of the graphite material is 1.2 grams per centimeter 3 (g/cm 3 )-1.4g/cm 3 ; and the difference between the compaction density of the negative electrode film layer and the tap density of the graphite material is greater than or equal to 0.15g/cm 3 .
  • tapped density refers to the mass per unit volume of powder in a container measured after being tapped under specified conditions.
  • the tap density of the graphite material can be tested by a method known in the art.
  • GB/T 5162-2006 can be referred to and a powder tap density tester can be used for measurement.
  • the test instrument can be Dandong Better BT-301, and the test parameters are as follows: vibration frequency 250 ⁇ 15 times/minute, amplitude 3 ⁇ 0.2 millimeters (mm), vibration number 5000 times, and measuring cylinder 25 milliliters (mL).
  • the tap density of the graphite material is 1.2 g/cm 3 , 1.25 g/cm 3 , 1.3 g/cm 3 , 1.35 g/cm 3 , 1.4 g/cm 3 , or any range therebetween.
  • the compaction density of the negative electrode film layer can be tested by methods known in the art.
  • an electronic balance is used to weigh a negative electrode plate test sample with an area of S, and the weight is recorded as W1, and a micrometer is used to measure the thickness T1 of the negative electrode plate.
  • W1 the weight of the negative electrode plate test sample
  • T2 the thickness of the negative electrode current collector
  • the difference between the compaction density of the negative electrode film layer and the tap density of the graphite material is 0.15 g/cm 3 , 0.16 g/cm 3 , 0.17 g/cm 3 , 0.18 g/cm 3 , 0.19 g/cm 3 , 0.2 g/cm 3 , 0.21 g/cm 3 , 0.22 g/cm 3 , 0.23 g/cm 3 , 0.24 g/cm 3 , 0.25 g/cm 3 or any range therebetween.
  • the above-mentioned pole piece will have uneven local lithium ion concentration distribution when stored at high temperature or after multiple charge and discharge, resulting in lithium precipitation and capacity decay, and the capacity retention rate is greatly deteriorated.
  • the disclosed embodiments break the prejudice in the prior art by using a high tap density negative electrode film layer in combination with a high tap density graphite material.
  • the secondary battery can fully utilize the advantages of the high tap density graphite material with good cycle performance, and can also reduce the probability of severe black spots forming on the negative electrode after the battery is fully charged, and reduce the probability of the battery's performance "diving" after long-cycle cycling or high-temperature storage, thereby improving the battery's cycle stability and high-temperature storage stability.
  • the compaction density of the negative electrode film layer is less than or equal to 1.55 g/cm 3 and greater than or equal to 1.40 g/cm 3 .
  • the compaction density of the negative electrode film layer is 1.40 g/cm 3 , 1.43 g/cm 3 , 1.46 g/cm 3 , 1.49 g/cm 3 , 1.52 g/cm 3 , 1.55 g/cm 3 or any range therebetween.
  • the compaction density of the electrode film layer within a reasonable range can not only reduce the probability of severe black spots forming on the surface of the negative electrode after the battery is fully charged, but also improve the integrity of the graphite material particles during the cold pressing process, maintain the pore structure inside the electrode and the lower electrode tortuosity, and take into account the long cycle stability and high dynamic performance of the secondary battery.
  • the graphite material includes primary particles. In some embodiments, based on the total number of particles in the graphite material, the number of primary particles in the graphite material accounts for greater than or equal to 85%. In the method, based on the total number of particles of the graphite material, the number of primary particles in the graphite material accounts for 85%-100%.
  • primary particles refers to particles in a non-agglomerated state.
  • the percentage of primary particles in the graphite material can be tested by methods known in the art.
  • a test sample is randomly selected in the negative electrode film layer, and multiple test areas are randomly selected in the test sample. Images of the multiple test areas are acquired using a scanning electron microscope. The ratio of the number of graphite material particles with primary particle morphology in each image to the total number of graphite material particles is counted, and the average value of the multiple statistical results is the percentage of primary particles in the graphite material.
  • the number of primary particles in the graphite material accounts for 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100% or any range therebetween.
  • primary particles can effectively reduce the grain boundary content, reduce the probability of side reactions between graphite materials and electrolytes, improve the uniformity of the electrodes, and further improve the cycle stability of secondary batteries through a high proportion of primary particle content.
  • the Dv1 of the graphite material is 1.5 micrometers ( ⁇ m) to 3.0 ⁇ m. In some embodiments, the Dv1 of the graphite material is 1.6 ⁇ m to 2.8 ⁇ m.
  • Dv1 the average volume distribution number of the material reaches 1%, 50%, 90% and 10% in the particle size distribution curve.
  • the volume distribution particle sizes Dv1, Dv50, Dv90, and Dv10 of the graphite material can be tested by methods known in the art.
  • a laser particle size analyzer is used for the determination.
  • the testing instrument can be a Mastersizer 3000 laser particle size analyzer produced by Malvern Instruments Ltd., UK.
  • the Dv1 of the graphite material is 1.5 ⁇ m, 1.6 ⁇ m, 1.7 ⁇ m, 1.8 ⁇ m, 1.9 ⁇ m, 2.0 ⁇ m, 2.1 ⁇ m, 2.2 ⁇ m, 2.3 ⁇ m, 2.4 ⁇ m, 2.5 ⁇ m, 2.6 ⁇ m, 2.7 ⁇ m, 2.8 ⁇ m, 2.9 ⁇ m, 3.0 ⁇ m or any range therebetween.
  • the graphite material has a Dv1 within a suitable range, which can not only make the negative electrode film layer have a certain proportion of fine powder, that is, small-particle graphite material, which is beneficial to improve the electrical contact of the negative electrode film layer, improve the kinetic performance, make the formation gas production end SOC earlier, reduce the probability of serious black spots in the battery preparation process and the probability of "diving" in the electrochemical performance of the battery during recycling; it can also reduce the probability of small-particle graphite material blocking the pores of the negative electrode film layer, maintain normal pole piece pores so that the electrolyte has high wettability, reduce the risk of negative electrode lithium plating, and further improve the cycle stability of the battery.
  • the Dv50 of the graphite material is 12 ⁇ m to 16 ⁇ m. In some embodiments, the Dv50 of the graphite material is 13 ⁇ m to 15 ⁇ m.
  • the Dv50 of the graphite material is 12 ⁇ m, 13 ⁇ m, 14 ⁇ m, 15 ⁇ m, 16 ⁇ m, or any range therebetween.
  • the graphite material has a large volume distribution particle size Dv50, which is beneficial to the formation of a reasonable pore structure between the particles of the negative electrode film layer, which is beneficial to the electrolyte to fully infiltrate the negative electrode plate, reduce the possibility of local polarization of the plate, and reduce the impact of black spots on the negative electrode on the cycle life and storage stability of the battery.
  • the particle size distribution (Dv90-Dv10)/Dv50 of the graphite material is 1.2-1.7. In some embodiments, the particle size distribution (Dv90-Dv10)/Dv50 of the graphite material is 1.35-1.60.
  • the particle size distribution of the graphite material (Dv90-Dv10)/Dv50 is 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7 or any range therebetween.
  • Graphite materials with a particle size distribution within the above range can reduce the uneven distribution of active ions in the graphite material caused by the large difference in particle size, reduce the side reaction between small-particle graphite materials and electrolytes, and improve the cycle performance and storage stability of secondary batteries.
  • the graphite material has a specific surface area of 0.6 m 2 / g to 1.5 m 2 /g. In some embodiments, the graphite material has a specific surface area of 0.9 m 2 / g to 1.4 m 2 /g.
  • the specific surface area of the graphite material can be tested by methods known in the art.
  • the specific surface area analysis test method of nitrogen adsorption is used for testing, and the specific surface area is calculated by the BET (Brunauer Emmett Teller) method.
  • the testing instrument can be the Tri-Star 3020 specific surface area pore size analysis tester of Micromeritics, USA.
  • the specific surface area of the graphite material is 0.6 m2 /g, 0.7 m2 /g, 0.8 m2 /g, 0.9 m2/g, 1 m2 /g, 1.1 m2 /g, 1.2 m2 /g, 1.3 m2/g, 1.4 m2/g, 1.5 m2 /g, or any range therebetween.
  • Graphite material has a small specific surface area, which can reduce the probability of side reactions between graphite material and electrolyte and improve the cycle performance and storage stability of the battery.
  • the oil absorption value of the graphite material is less than or equal to 45 milliliters (ml)/100 grams (g). In some embodiments, the oil absorption value of the graphite material is 30 ml/100 g-45 ml/100 g.
  • oil absorption value refers to the volume of linseed oil that can be absorbed by 100g of graphite material. For example, if the oil absorption value of a graphite material is 40ml/100g, it means that 100g of the graphite material can absorb 40ml of linseed oil.
  • the oil absorption value of graphite material can be tested by methods and equipment known in the art, as shown below: obtain test oil and graphite material samples respectively, and set the torque threshold of the oil absorption value tester; add oil to the sample in the mixing chamber of the oil absorption value tester at a constant speed, and as the oil absorption of the sample increases, the viscosity of the mixture of the sample and the oil continues to increase. When the viscosity of the mixture reaches the preset torque threshold of the oil absorption value tester, stop and calculate the volume of oil absorbed by the sample per unit mass, which is the oil absorption value QI of the sample.
  • the test oil is linseed oil (DBP), and the torque threshold is 1 Newton (N).
  • the oil absorption value of the graphite material is 30ml/100g, 31ml/100g, 32ml/100g, 33ml/100g, 34ml/100g, 35ml/100g, 36ml/100g, 37ml/100g, 38ml/100g, 39ml/100g, 40ml/100g, 41ml/100g, 42ml/100g, 43ml/100g, 44ml/100g, 45ml/100g or any range therebetween.
  • the oil absorption value of graphite materials can reflect the dispersibility of graphite materials in negative electrode slurry to a certain extent.
  • a large oil absorption value of graphite materials means that the graphite materials need to be infiltrated with more dispersants, such as sodium carboxymethyl cellulose, during the dispersion process, and the slurry is more likely to settle, resulting in unstable quality during the electrode coating process and uneven thickness of the electrode after cold pressing.
  • Graphite materials with oil absorption values within the above range can not only have good wettability for the electrolyte, so that the secondary battery has good dynamic performance and cycle stability; they can also maintain good particle dispersion during the stirring process, and are not prone to slurry sedimentation due to excessive adsorption of dispersants by graphite materials, so that the electrode coating has a wider process window and the electrode has good uniformity.
  • the graphite material has a degree of graphitization of 88% to 93%. In some embodiments, the graphite material has a degree of graphitization of 89% to 92%.
  • degree of graphitization refers to an index measuring the degree to which carbon atoms form a close-packed hexagonal graphite crystal structure.
  • the graphitization degree of the graphite material can be tested by methods known in the art.
  • d 002 is the average interlayer spacing of the (002) crystal plane in the crystal structure of the graphite material expressed in nanometers (nm).
  • the graphite material has a degree of graphitization of 88%, 89%, 90%, 91%, 92%, 93%, or any range therebetween.
  • Controlling the degree of graphitization within the above range can not only take into account the capacity of the graphite material, but also achieve a smaller volume change of the graphite active material during the charging process, which is beneficial to further improve the cycle stability.
  • the surface density of the negative electrode film layer is 7 mg/cm 2 to 14 mg/cm 2 . In some embodiments, the surface density of the negative electrode film layer is 9 mg/cm 2 to 12 mg/cm 2 .
  • the area density of the negative electrode film layer is 7 mg/cm 2 , 8 mg/cm 2 , 9 mg/cm 2 , 10 mg/cm 2 , 11 mg/cm 2 , 12 mg/cm 2 , 13 mg/cm 2 , 14 mg/cm 2 or any range therebetween.
  • the graphite material includes synthetic graphite.
  • the preparation method of graphite material includes the following steps: providing raw materials, the raw materials include at least one of petroleum coke, needle coke, and asphalt coke, based on the total volume of the raw material structure, the volume of the mosaic structure and the regional structure in the raw material accounts for greater than or equal to 60%; processing the raw materials to obtain an intermediate product; and graphitizing the intermediate product to obtain a graphite material.
  • petroleum coke refers to the coke formed by high-temperature carbonization of petroleum residue or petroleum asphalt, which is called petroleum coke.
  • needle coke refers to coal tar pitch or petroleum pitch, which can produce coke with a needle-like texture after being carbonized in the liquid phase to form an anisotropic intermediate phase and then subjected to processes such as high-temperature carbonization.
  • pitch coke refers to a solid material produced by carbonizing coal tar pitch at high temperatures.
  • the feedstock comprises petroleum coke.
  • Petroleum coke has excellent anisotropy, which is conducive to the preparation of low-graphitization, low-expansion graphite materials, which is conducive to the long cycle life of the battery. At the same time, petroleum coke has high compaction density and high gram capacity, which is conducive to improving the energy density of the battery. In addition, the source of petroleum coke is more extensive, which is conducive to industrial production.
  • the above-mentioned raw materials usually include at least one of mosaic, regional and fiber structures.
  • isochromatic zone microstructures with a size less than 30 ⁇ m are judged as mosaic
  • isochromatic zone microstructures with a size greater than 30 ⁇ m are judged as regional
  • anisotropic strip-shaped isochromatic zones are judged as fiber structures.
  • the proportion of mosaic structure and regional structure in the raw material can be tested by methods known in the art.
  • the raw material is taken according to GB 1997-89, the raw material crushed to 1mm is mixed, 40g to 50g is shrunk, and 4g to 5g of 0.07mm to 1.0mm grade samples are taken by square hole sieve for slice making; powder coke and block coke optical slices are prepared according to MT 116.1-86, the diameter of the powder coke optical slice shall not be less than 22mm, and the volume occupied by the cement shall be less than 1/3; the sample is placed on a slide with cement, flattened, and then placed on the stage for focus, and the polarizer, detector, and microscope are adjusted after calibration. The mirror is biased to make it orthogonal.
  • the volume proportion of the mosaic structure and the regional structure in the raw material is 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100% or any numerical range therebetween.
  • Precursors in which the volume proportion of mosaic structure and regional structure in the raw materials is relatively high have higher isotropy, which is conducive to the preparation of graphite materials with low degree of graphitization, reduces the expansion rate of the lattice during the charge and discharge cycle, and improves the cycle stability of the battery.
  • the power of the graphitization process is 70% to 90% of the rated power of the equipment.
  • the power of the graphitization treatment is 70%, 75%, 80%, 85%, 90% of the rated power of the equipment, or any range of values therebetween.
  • the graphitization treatment equipment refers to any device capable of graphitization treatment, including but not limited to Acheson furnace, box furnace, inner series furnace, continuous graphitization, electric calcining furnace, medium frequency furnace, tubular furnace and other devices.
  • the rated power of graphitization treatment equipment produced by different manufacturers may be different, and can be selected according to actual conditions.
  • the graphitization processing power used in the present disclosure needs to be lower than the rated power of the graphitization processing equipment to achieve uniformity of the temperature field during the graphitization process, ensure the consistency of the material's gram capacity, and help improve the cycle life of the battery.
  • the maximum power of the graphitization process is 23,000 watts (W) to 25,000W.
  • the maximum power of the graphitization process is 23000 W, 23500 W, 24000 W, 24500 W, 25000 W, or any range therebetween.
  • the graphitization degree of the graphite material during the heat treatment process can be effectively controlled, which is beneficial to improving the cycle life of the battery.
  • the graphitization process is performed at a constant power time of 10 hours (h) to 50 h at maximum power.
  • the constant power time of the graphitization treatment at maximum power is 10 h, 13 h, 16 h, 19 h, 22 h, 25 h, 30 h, 35 h, 40 h, 45 h, 50 h, or any range therebetween.
  • the graphitization treatment equipment is an internal series furnace, and the graphitization treatment time at maximum power is 10h-30h.
  • the graphitization treatment equipment is an Acheson furnace, and the graphitization treatment time at maximum power is 30h-50h.
  • the appropriate graphitization treatment time is not easy to cause excessive rearrangement of the precursor, resulting in a high specific surface area of the graphite material after graphitization and deterioration of the cycle performance; it can also effectively increase the gram capacity of the graphite material, thereby facilitating the simultaneous improvement of the energy density and cycle life of the secondary battery.
  • the processing of raw materials specifically includes the following steps: crushing, shaping and grading the raw materials to obtain secondary raw materials; removing a certain proportion of fine powder in the secondary raw materials, the mass of the removed fine powder is 15%-45% of the total mass of the secondary raw materials, and obtaining a precursor, wherein the Dv50 of the fine powder is 3 ⁇ m-7 ⁇ m, and Dv99 is less than or equal to 30 ⁇ m.
  • a crusher such as a jaw crusher, can be used to crush the raw material.
  • the raw material can be crushed to a set particle size and then sieved, such as 3-20 Mesh sieve.
  • a shaping machine in the step of shaping the raw material, can be used to shape the crushed raw material.
  • the shaping process can reduce burrs on the surface of the crushed raw material, which is conducive to obtaining a rounded graphite material.
  • an air flow classifier in the step of classifying the raw materials, can be used to classify the shaped raw materials.
  • the induced air frequency can be greater than or equal to 20 Hz, and the classification frequency can be greater than or equal to 65 Hz. Classification can reduce the content of large particles and small particles in the precursor.
  • the proportion of fine powder removed from the secondary raw material is any value of 10%, 15%, 20%, 25%, 30%, 35% or a range consisting of any two values therein.
  • the volume distribution particle size Dv1 of the graphite material can be controlled within a suitable range, which can not only make the electrode have an excellent liquid absorption rate, the electrolyte can fully infiltrate the negative electrode, but also make the graphite particles have excellent electrical contact, thereby comprehensively improving the cycle performance of the battery.
  • the volume distribution particle size Dv50 of the precursor is 12 ⁇ m-18 ⁇ m.
  • the volume distribution particle size Dv50 of the precursor is 12 ⁇ m, 13 ⁇ m, 14 ⁇ m, 15 ⁇ m, 16 ⁇ m, 17 ⁇ m, 18 ⁇ m, or any range therebetween.
  • the (Dv90-Dv10)/Dv50 of the precursor is 1.3-2.0.
  • (Dv90-Dv10)/Dv50 of the precursor is 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, or any range therebetween.
  • Controlling the volume distribution particle size Dv50 or (Dv90-Dv10)/Dv50 of the precursor within a suitable range is beneficial to controlling the volume distribution particle size Dv50 or (Dv90-Dv10)/Dv50 of the graphite material within a suitable range, which can improve the cycle performance of the battery.
  • the secondary battery can be a lithium-ion battery, etc.
  • a secondary battery includes a positive electrode plate, a negative electrode plate, and an electrolyte, etc.
  • active ions are embedded and removed back and forth between the positive electrode plate and the negative electrode plate, and the electrolyte plays a role in conducting active ions between the positive electrode plate and the negative electrode plate.
  • the present disclosure has no particular restrictions on the type of the electrolyte, which can be selected according to actual needs.
  • the electrolyte can be selected from at least one of a solid electrolyte and a liquid electrolyte (i.e., an electrolyte).
  • Secondary batteries using electrolytes, as well as some secondary batteries using solid electrolytes may also include a separator, which is arranged between the positive electrode plate and the negative electrode plate to play an isolation role.
  • the negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector.
  • the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode film layer comprises the graphite material of the first aspect of the embodiment of the present disclosure or the graphite material prepared by the method described in the second aspect of the embodiment of the present disclosure, thereby enabling the secondary battery to have high first coulombic efficiency, high energy density, good cycle performance and storage stability.
  • the negative electrode film layer may further include other negative electrode active materials in addition to the above-mentioned graphite materials.
  • the other negative electrode active materials include but are not limited to one or more of conventional natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials and lithium titanate.
  • the silicon-based material may The tin-based material may include one or more of simple silicon, silicon oxide, silicon-carbon compound, silicon-nitrogen compound and silicon alloy material.
  • the tin-based material may include one or more of simple tin, tin oxide and tin alloy material.
  • the negative electrode film layer further includes a negative electrode conductive agent.
  • a negative electrode conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the negative electrode film layer further includes a negative electrode binder.
  • the negative electrode binder may include one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).
  • SBR styrene-butadiene rubber
  • SR-1B water-soluble unsaturated resin
  • aqueous acrylic resin e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS
  • PAM polyacrylamide
  • PVA polyvinyl alcohol
  • SA sodium alginate
  • CMCS carboxymethyl chitosan
  • the negative electrode film layer further comprises other additives.
  • the other additives may include a thickener, such as sodium carboxymethyl cellulose (CMC), a PTC thermistor material, and the like.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • a metal foil a copper foil may be used.
  • the composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer.
  • the metal material may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy.
  • the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS) and polyethylene (PE).
  • the negative electrode film layer is usually formed by coating the negative electrode slurry on the negative electrode current collector, drying and cold pressing.
  • the negative electrode slurry is usually formed by dispersing the negative electrode active material, conductive agent, binder and other additives in a solvent and stirring them uniformly.
  • the solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.
  • the negative electrode plate does not exclude other additional functional layers in addition to the negative electrode film layer.
  • the negative electrode plate described in the present disclosure further includes a conductive primer layer (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector; in some embodiments, the negative electrode plate described in the present disclosure further includes a protective layer covering the surface of the negative electrode film layer.
  • the positive electrode plate includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector.
  • the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • a metal foil aluminum foil may be used.
  • the composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer.
  • the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy.
  • the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS) and polyethylene (PE).
  • the positive electrode film layer generally comprises a positive electrode active material, a binder and a conductive agent.
  • the positive electrode film layer is generally formed by coating a positive electrode slurry on the positive electrode current collector, drying, and cold pressing.
  • the positive electrode slurry is generally formed by dispersing a positive electrode active material, a conductive agent, a binder, and any other components in a solvent and stirring them uniformly.
  • the solvent may be N-methylpyrrolidone (NMP), but is not limited thereto.
  • the binder for the positive electrode film layer may include
  • the conductive agent for the positive electrode film layer includes one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PTFE polytetrafluoroethylene
  • vinylidene fluoride-tetrafluoroethylene-propylene terpolymer vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer
  • the conductive agent for the positive electrode film layer includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the positive electrode active material may be a positive electrode active material for a secondary battery known in the art.
  • the positive electrode active material may include, but is not limited to, one or more of lithium-containing transition metal oxides, lithium-containing phosphates, and their respective modified compounds.
  • the lithium transition metal oxide may include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds.
  • lithium-containing phosphate may include, but are not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, a composite material of lithium iron manganese phosphate and carbon, and their respective modified compounds.
  • the positive electrode active material for the lithium ion battery may include one or more of a lithium transition metal oxide and a modified compound thereof of the general formula Li a Ni b Co c M d O e A f . 0.8 ⁇ a ⁇ 1.2, 0.5 ⁇ b ⁇ 1, 0 ⁇ c ⁇ 1, 0 ⁇ d ⁇ 1, 1 ⁇ e ⁇ 2, 0 ⁇ f ⁇ 1, M is selected from one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and A is selected from one or more of N, F, S and Cl.
  • a positive electrode active material for a lithium ion battery may include one or more of LiCoO 2 , LiNiO 2 , LiMnO 2 , LiMn 2 O 4 , LiNi 1/3 Co 1/3 Mn 1/3 O 2 (NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811), LiNi 0.85 Co 0.15 Al 0.05 O 2 , LiFePO 4 , and LiMnPO 4 .
  • the modified compound of each positive electrode active material may be a compound that performs doping modification and/or surface coating modification on the positive electrode active material.
  • the electrolyte is an electrolyte solution
  • the electrolyte solution includes an electrolyte salt and a solvent.
  • the type of the electrolyte salt is not particularly limited and can be selected according to actual needs.
  • the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium bisoxalatoborate (LiBOB), lithium difluorophosphate (LiPO 2 F 2 ), lithium difluorobisoxalatophosphate (LiDFOP), and lithium tetrafluorooxalatophosphate (LiTFOP).
  • LiPF 6 lithium hexafluorophosphate
  • LiBF 4 lithium perchlorate
  • the solvent may include ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), cyclopentane (SF), dimethyl sulfone (MSM), methyl ethyl sul
  • the electrolyte further includes additives.
  • the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain properties of the secondary battery, such as additives that improve the overcharge performance of the secondary battery, additives that improve the high temperature performance of the secondary battery, and additives that improve the low temperature power performance of the secondary battery.
  • the present disclosure 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 membrane may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation membrane may be a single-layer film or a multi-layer composite film. When the isolation membrane is a multi-layer composite film, the materials of each layer are the same or different.
  • the positive electrode sheet, the separator, and the negative electrode sheet can be formed into an electrode assembly by a winding process or a lamination process.
  • the secondary battery may include an outer package, which may be used to encapsulate the electrode assembly and the electrolyte.
  • the outer packaging can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging can also be a soft package, such as a bag-type soft package.
  • the material of the soft package can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT) and polybutylene succinate (PBS).
  • FIG1 is a secondary battery 5 of a square structure as an example.
  • the outer package may include a shell 51 and a cover plate 53.
  • the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity.
  • the shell 51 has an opening connected to the receiving cavity, and the cover plate 53 is used to cover the opening to close the receiving cavity.
  • the positive electrode sheet, the negative electrode sheet and the isolation film can form an electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is encapsulated in the receiving cavity.
  • the 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, which can be adjusted according to demand.
  • the preparation method of the secondary battery disclosed in the present invention is well known.
  • the positive electrode sheet, the separator, the negative electrode sheet and the electrolyte can be assembled to form a secondary battery.
  • the positive electrode sheet, the separator and the negative electrode sheet can be formed into an electrode assembly through a winding process or a lamination process, and the electrode assembly is placed in an outer package, and the electrolyte is injected after drying, and the secondary battery is obtained through vacuum packaging, standing, forming, shaping and other processes.
  • the secondary battery according to the present disclosure may be assembled into a battery module.
  • the battery module may contain multiple secondary batteries, and the specific number may be adjusted according to the application and capacity of the battery module.
  • FIG3 is a schematic diagram of 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. Of course, they may also be arranged in any other manner. Further, the plurality of secondary batteries 5 may be fixed by fasteners.
  • the battery module 4 may further include a housing having a receiving space, and the plurality of secondary batteries 5 may be received in the receiving space.
  • the battery modules described above may also be assembled into a battery pack, and the number of battery modules contained in the battery pack may be adjusted according to the application and capacity of the battery pack.
  • FIG4 and FIG5 are schematic diagrams of a battery pack 1 as an example.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3.
  • the upper box body 2 is used to cover the lower box body 3 and form a closed space for accommodating the battery module 4.
  • a plurality of battery modules 4 can be arranged in the battery box in any manner.
  • the present disclosure also provides an electric device, which includes at least one of the secondary battery, battery module, or battery pack of the present disclosure.
  • the secondary battery, battery module, or battery pack can be used as a power source for the electric device, and can also be used as an energy storage unit for the electric device.
  • the electric device can be, but is not limited to, a mobile device (such as a mobile phone, a tablet computer, a laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc.
  • the electrical device may select a secondary battery, a battery module or a battery pack according to its usage requirements.
  • Fig. 6 is a schematic diagram of an electric device as an example.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.
  • a battery pack or a battery module may be used.
  • the electric device may be a mobile phone, a tablet computer, a notebook computer, etc.
  • the electric device is usually required to be light and thin, and a secondary battery may be used as a power source.
  • the petroleum coke with mosaic and regional structures accounting for 63.1% is coarsely crushed; the coarsely crushed material is then crushed and sieved, and the sieved material is shaped and graded.
  • a certain amount of fine powder is removed to obtain a precursor, wherein the removed fine powder accounts for 17% of the total mass of the petroleum coke raw material.
  • the obtained precursor has a Dv50 particle size of 15.5 ⁇ m, and a particle size distribution (Dv90-Dv10)/Dv50 of 1.92; fine powder refers to components with a Dv50 of 3 ⁇ m-7 ⁇ m and a Dv99 of less than or equal to 30 ⁇ m.
  • the precursor was graphitized in an Acheson furnace at a temperature of 2800°C and a maximum power of 24000W. After 40 hours of treatment at the maximum power, the surface temperature of the Acheson furnace crucible was cooled to 400°C, the graphite crucible was taken out, and the graphite material was obtained after screening and demagnetization.
  • the tap density of the graphite material is 1.21 g/cm 3 , Dv1 is 1.8 ⁇ m, Dv50 is 14.6 ⁇ m, the particle size distribution (Dv90-Dv10)/Dv50 is 1.42, the specific surface area is 1.14 m 2 /g, and the degree of graphitization is 91.1%.
  • the preparation method of material 2-5 is similar to that of material 1, except that the proportion of fine powder removal and the particle size distribution of the precursor are adjusted.
  • the above-prepared material 1, conductive agent carbon black (Super P), binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose were fully stirred and mixed in an appropriate amount of solvent deionized water at a weight ratio of 95.4:1.8:1.0:1.8 to form a negative electrode slurry.
  • the negative electrode slurry was coated on both surfaces of the negative electrode current collector copper foil, and after drying and cold pressing, a negative electrode sheet was obtained.
  • the compaction density of the negative electrode film layer was 1.50g/ cm3 and the surface density was 9.4mg/ cm2 .
  • the positive electrode active material lithium iron phosphate (LFP), the conductive agent Super P, and the binder PVDF are mixed in a mass ratio of 97:1:2, and the solvent N-methylpyrrolidone NMP is added, and the system is stirred under the action of a vacuum mixer until the system is uniform to obtain a positive electrode slurry; the positive electrode slurry is evenly coated on the positive electrode current collector aluminum foil, and the positive electrode sheet is obtained after drying, cold pressing, and slitting.
  • the compaction density of the positive electrode film layer is 2.50g/ cm3 , and the surface density is 20mg/ cm2 .
  • Polypropylene film is used as the isolation membrane.
  • the positive electrode sheet, separator and negative electrode sheet are stacked in order, so that the separator is between the positive and negative electrode sheets to play an isolating role, and then wound to obtain an electrode assembly; the electrode assembly is placed in an outer package, and after drying, the electrolyte is injected, and after vacuum packaging, standing, forming, shaping and other processes, a lithium-ion battery is obtained.
  • the preparation method of the secondary battery is similar to that of Example 1, except that different graphite materials are used or the compaction density of the electrode film layer is adjusted, as shown in Table 2 for details.
  • the liquid-filled batteries prepared in the examples and comparative examples were charged at 0.33C, and the gas generated during the formation process was collected. When the total amount of gas did not increase, the corresponding SOC was recorded.
  • the batteries of the above embodiments and comparative examples were charged at a constant current of 0.33C to a voltage of 3.65V, and were disassembled in a drying room to observe whether there were black spots on the surface of the negative electrode plate; the total area of black spots/total area of the negative electrode plate ⁇ 1%, and the area of black spots in a single electrode plate/area of a single electrode plate ⁇ 8% were defined as primary black spots; 1% ⁇ total area of black spots/total area of the negative electrode plate ⁇ 3%, or 8% ⁇ area of black spots in a single electrode plate/area of a single electrode plate ⁇ 15% were defined as secondary black spots; the total area of black spots/total area of the negative electrode plate >3%, or the area of black spots in a single electrode plate/area of a single electrode plate >15%, were defined as tertiary black spots.
  • the batteries of the above embodiments and comparative examples were charged at a constant current of 1C to a voltage of 3.65V, then charged at a constant voltage of 3.65V to a current of 0.05C, and then discharged at a constant current of 1C to a voltage of 2.5V. This is a charge and discharge cycle.
  • the discharge capacity C1 of the first cycle is recorded. Repeat the charging and discharging cycle until the battery capacity decays to 80% of the initial capacity C1, and record the number of cycles.
  • the charge and discharge test was carried out, charging to 3.65V at a constant current of 0.5C, and then charging to a current of 0.05C at a constant voltage. After standing for 5 minutes, the secondary battery was discharged to 2.5V at a constant current of 0.5C, and the discharge capacity at this time was recorded, which was the initial discharge capacity. Then the fully charged battery cell was placed in an environment of 60°C for different periods of time, and the remaining capacity was tested at 25°C every 30 days. This is a storage cycle, and the discharge capacity this time is the discharge capacity after the first storage. Subsequently, the first storage test process was repeated, the discharge capacity value during the storage process was recorded, and the discharge capacity after 120 days/initial discharge capacity was used as the storage capacity retention rate for 120 days.
  • the batteries of the embodiments and comparative examples were prepared according to the above method, and various performance parameters were measured. The results are shown in the table below.
  • the negative electrode film layer includes a graphite material, and the tap density of the graphite material is 1.2g/cm 3 -1.4g/cm 3 ; and the difference between the compaction density of the negative electrode film layer and the tap density of the graphite material is greater than or equal to 0.15g/cm 3 , which can give full play to the advantages of the high tap density negative electrode material, improve the battery cycle stability, and reduce the severity of the negative electrode black spots, thereby improving the battery cycle stability and storage stability.
  • the formation SOC of the battery is further reduced and the cycle stability is further improved.
  • Formation is the process of charging the battery for the first time and activating the electrochemical reaction inside the battery. As the formation charge proceeds, lithium ions are deintercalated from the positive electrode material, transported through the diaphragm to the negative electrode by the electrolyte and embedded in the negative electrode material, thereby forming a potential difference between the positive and negative electrodes, and converting electrical energy into chemical energy of the battery.
  • an oxidation-reduction reaction occurs at the solid-liquid interface of the negative electrode and the electrolyte to generate a solid electrolyte interface film (SEI film).
  • SEI film solid electrolyte interface film

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Abstract

本公开提供一种二次电池及用电装置，二次电池包括负极极片，负极极片包括负极集流体以及形成于负极集流体至少一个表面上的负极膜层，负极膜层包括石墨材料，石墨材料的振实密度为1.2g/cm3-1.4g/cm3；且负极膜层的压实密度与石墨材料的振实密度的差值不小于0.15g/cm3。

Description

二次电池及用电装置
交叉引用
本公开引用于2023年12月7日递交的名称为“二次电池及用电装置”的第202311675944.4号中国专利申请，其通过引用被全部并入本公开。
技术领域
本公开涉及电池技术领域，尤其涉及一种二次电池及用电装置。
背景技术
近年来，二次电池被广泛应用于水力、火力、风力和太阳能电站等储能电源系统，以及电动工具、电动自行车、电动摩托车、电动汽车、军事装备、航空航天等多个领域。
随着用电装置续航能力要求的不断提高，对二次电池的循环寿命有了更为严苛的要求。如何能够进一步提高二次电池的循环寿命是本领域技术人员亟需解决的技术问题。
发明内容
本公开的目的在于提供一种二次电池和用电装置，其能使二次电池的循环寿命得到改善。
本公开第一方面提供一种二次电池，其特征在于，包括负极极片，负极极片包括负极集流体以及形成于负极集流体至少一个表面上的负极膜层，负极膜层包括石墨材料，石墨材料的振实密度为1.2g/cm3-1.4g/cm3；且负极膜层的压实密度与石墨材料的振实密度的差值大于等于0.15g/cm3。
申请人发现高振实密度的石墨材料在低压实密度的极片中易于产生严重黑斑的原因是源于高振实密度的石墨材料易于形成紧密堆积，在较低的冷压压力下极片就能实现预期的低压实密度，较低的冷压压力使得极片在压实过程中石墨材料间的孔隙过大，石墨材料间接触较差，在化成过程中石墨材料与电解液间的电化学反应不及时，负极膜层中产生的气体无法及时排出，阻止该区域石墨材料继续嵌锂，满充后易于在负极表面形成严重的黑斑。上述极片在高温存储或者在多次充放电后会出现局部锂离子浓度分布不均，造成析锂导致容量衰减，容量保持率大幅恶化。本公开实施例打破现有技术中的偏见，采用高压实密度负极膜层搭配高振实密度石墨材料，该二次电池既能够充分发挥高振实密度石墨材料循环性能好的优势，又能够降低电池满充后在负极形成严重黑斑的概率，减少电池在长周期循环或高温存储后性能“跳水”的概率，提高了电池的循环稳定性和高温存储稳定性。
在本公开的任意实施方式中，负极膜层的压实密度小于等于1.55g/cm3，且大于等于 1.40g/cm3。
合理范围内的极片膜层压实密度不但能够降低电池满充后极片形成严重的黑斑的概率，还能够提高石墨材料颗粒在冷压过程中的完整度，维持极片内部的孔隙结构和较低的极片迂曲度，兼顾二次电池长的循环稳定性和高的动力学性能。
在本公开的任意实施方式中，石墨材料包括一次颗粒。在一些实施例中，基于石墨材料的颗粒总数量计，石墨材料中一次颗粒的数量占比大于等于85％。在一些示例性实施例中，基于石墨材料的颗粒总数量计，石墨材料中一次颗粒的数量占比为85％-100％。
相比于二次颗粒，一次颗粒可以有效降低晶界含量，减少石墨材料与电解液副反应的发生概率，提高极片的均一性，通过高比例的一次颗粒含量改善二次电池的循环稳定性。
在本公开的任意实施方式中，石墨材料的Dv1为1.5μm-3.0μm。在一些实施例中，石墨材料的Dv1为1.6μm-2.8μm。
申请人发现石墨材料的Dv1粒径对二次电池的电化学表现具有重要影响。石墨材料具有合适范围内的Dv1既能够使得负极膜层中具有一定比例的细粉，即小粒径石墨材料，有利于提高负极膜层的电接触，改善动力学性能，使得化成产气截至SOC提前，降低电池制备过程中产生严重黑斑的概率和电池循环使用或存储时电化学表现发生“跳水”的概率；又可以减少小粒径石墨材料堵塞负极膜层孔隙的概率，维持正常的极片孔隙使得电解液具有高浸润性，降低负极析锂风险，改善电池的循环稳定性和高温存储稳定性。
在本公开的任意实施方式中，石墨材料的Dv50为12μm-16μm。在一些实施例中，石墨材料的Dv50为13μm-15μm。
该石墨材料具有大的体积分布粒径Dv50，有利于负极膜层的颗粒之间形成合理的孔道结构，有利于电解液充分浸润负极极片，减小极片局部极化的可能性，减少负极出现黑斑现象对电池的循环寿命和存储稳定性的影响。
在本公开的任意实施方式中，石墨材料的粒度分布(Dv90-Dv10)/Dv50为1.2-1.7。在一些实施例中，石墨材料的粒度分布(Dv90-Dv10)/Dv50为1.35-1.60。
粒度分布在上述范围内的石墨材料能够降低由于粒径差距较大引起的活性离子在石墨材料中分布不均匀，减少小粒径的石墨材料与电解液的副反应，改善二次电池的循环性能和存储稳定性。
在本公开的任意实施方式中，石墨材料的比表面积为0.6m2/g-1.5m2/g。在一些实施例中，石墨材料的比表面积为0.9m2/g-1.4m2/g。
石墨材料具有小的比表面积，能够减少石墨材料与电解液的副反应的发生概率，提高电池的循环性能和存储稳定性。
在本公开的任意实施方式中，石墨材料的吸油值不超过45ml/100g。在一些实施例中，石墨材料的吸油值为30ml/100g-45ml/100g。
石墨材料的吸油值能够在一定程度上反映石墨材料在负极浆料中的分散性。石墨材料的吸油值大，意味着石墨材料在分散过程中需要浸润更多的分散剂，如羧甲基纤维素钠，浆料更容易沉降，导致极片涂布过程质量不稳定，冷压后极片厚度不均匀。吸油值在上述范围内的石墨材料既能够对于电解液具有良好的浸润性，使得二次电池具有良好的动力学性能和循环稳定性；又能够在搅拌过程中维持好的颗粒分散度，不容易因石墨 材料对分散剂过多的吸附造成浆料沉降，使得极片涂布具有较宽的工艺窗口，极片具有良好的均一性。
在本公开的任意实施方式中，石墨材料的石墨化度为88％-93％。在一些实施例中，石墨材料的石墨化度为89％-92％。
控制石墨化程度在上述范围内既能够兼顾石墨材料的容量，又可以实现石墨活性材料在充电过程中较小的体积变化，有利于循环稳定性的提高。
在本公开的任意实施方式中，负极膜层的面密度为7mg/cm2～14mg/cm2。在一些实施例中，负极膜层的面密度为9mg/cm2～12mg/cm2。
在本公开的任意实施方式中，石墨材料包括人造石墨。
本公开第二方面提供一种用电装置，其包括本公开第一方面的二次电池。
附图说明
为了更清楚地说明本公开实施例的技术方案，下面将对本公开实施例中所需要使用的附图作简单地介绍。显而易见地，下面所描述的附图仅仅是本公开的一些实施方式，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据附图获得其他的附图。
图1是本公开的二次电池的一实施方式的示意图。
图2是本公开的二次电池的一实施方式的分解示意图。
图3是本公开的电池模块的一实施方式的示意图。
图4是本公开的电池包的一实施方式的示意图。
图5是图4所示的电池包的实施方式的分解示意图。
图6是包含本公开的二次电池作为电源的用电装置的一实施方式的示意图。
在附图中，附图未必按照实际的比例绘制。附图标记说明如下：1电池包，2上箱体，3下箱体，4电池模块，5二次电池，51壳体，52电极组件，53盖板。
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公开的二次电池及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公开而提供的，并不旨在限定权利要求书所记载的主题。
本公开所公开的“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。在本公开中，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，本公开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，并且这样的技术方案应被认为包含在本公开的公开内容中。
如果没有特别的说明，本公开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，并且这样的技术方案应被认为包含在本公开的公开内容中。
如果没有特别的说明，本公开的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本公开所提到的“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，在本公开中，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)。
如果没有特别的说明，本公开中使用的术语具有本领域技术人员通常所理解的公知含义。
如果没有特别的说明，本公开中提到的各参数的数值可以用本领域常用的各种测试方法进行测定，例如，可以按照本公开给出的测试方法进行测定。
如果没有特别的说明，在本公开中，术语“活性离子”是指能在二次电池正极和负极之间往返嵌入和脱出的离子，包括但不限于锂离子。
在本公开中，术语“多个”、“多种”是指两个或两种以上。
随着新能源行业的不断发展，锂电池储能系统得到了愈发广泛的关注。锂电池储能系统是一种利用锂电池进行能量储存的装置，它既可以存储太阳光伏、风能等可再生能源产生的能量，也可作为电网的辅助设施。相比于动力电池，储能电池更关注电池的循环寿命。为了追求电池的长循环寿命，研发人员通常会选择具有高振实密度的负极材料搭配以低的极片膜层压实密度，因为高振实密度的负极材料在极片冷压过程中受到的压力较小，有利于保持颗粒的完整性以及颗粒内部的低应力，降低副反应发生概率的同时维持极片的长周期孔道结构，保证嵌锂路径通畅、减小极化，提供电池在长循环周期的动力学性能，改善电池的循环寿命。但是，申请人在研发过程中发现，该负极极片在满充后易于在负极表面形成黑斑，对极片的外观和品质产生不利影响，且黑斑现象严重的极片在多次充放电后会导致局部锂离子浓度分布不均，造成析锂导致容量“跳水”，无法满足长循环寿命电池的使用需求和存储需求。
基于此，本公开提供了一种二次电池，包括负极极片，所述负极极片包括负极集流 体以及形成于所述负极集流体至少一个表面上的负极膜层，所述负极膜层包括石墨材料，所述石墨材料的振实密度为1.2克/厘米3(g/cm3)-1.4g/cm3；且所述负极膜层的压实密度与所述石墨材料的振实密度的差值大于等于0.15g/cm3。
在本文中，术语“振实密度”指在规定条件下容器中的粉末经振实后所测得的单位容积的质量。
本公开中，石墨材料的振实密度可以采用本领域已知的方法进行测试，作为示例，可参照GB/T 5162-2006，使用粉体振实密度测试仪进行测定。测试仪器可以采用丹东百特BT-301，测试参数如下：振动频率250±15次/分钟，振幅3±0.2毫米(mm)，振动次数5000次，量筒25毫升(mL)。
在一些实施方式中，所述石墨材料的振实密度为1.2g/cm3、1.25g/cm3、1.3g/cm3、1.35g/cm3、1.4g/cm3或任意二者间的数值范围。
本公开中，负极膜层的压实密度可以采用本领域已知的方法进行测试。作为示例，使用电子天平对面积为S的负极极片测试样品进行称重，重量记为W1，并使用万分尺测得负极极片的厚度T1。然后将上述称重后的极片膜层擦拭掉，称量负极集流体的重量，记为W2，并使用万分尺测得负极集流体的厚度T2。则负极膜层的压实密度PD＝(W1-W2)/[(T1-T2)×S]。
在一些实施方式中，所述负极膜层的压实密度与所述石墨材料的振实密度的差值为0.15g/cm3、0.16g/cm3、0.17g/cm3、0.18g/cm3、0.19g/cm3、0.2g/cm3、0.21g/cm3、0.22g/cm3、0.23g/cm3、0.24g/cm3、0.25g/cm3或任意二者间的数值范围。
申请人发现高振实密度的石墨材料在低压实密度的极片中易于产生严重黑斑的原因是源于高振实密度的石墨材料易于形成紧密堆积，在较低的冷压压力下极片就能实现预期的低压实密度，较低的冷压压力使得极片在压实过程中石墨材料间的孔隙过大，石墨材料间接触较差，在化成过程中石墨材料与电解液间的电化学反应不及时，负极膜层中产生的气体无法及时排出，阻止该区域石墨材料继续嵌锂，满充后易于在负极表面形成严重的黑斑。上述极片在高温存储或者在多次充放电后会出现局部锂离子浓度分布不均，造成析锂导致容量衰减，容量保持率大幅恶化。本公开实施例打破现有技术中的偏见，采用高压实密度负极膜层搭配高振实密度石墨材料，该二次电池既能够充分发挥高振实密度石墨材料循环性能好的优势，又能够降低电池满充后在负极形成严重黑斑的概率，减少电池在长周期循环或高温存储后性能“跳水”的概率，提高了电池的循环稳定性和高温存储稳定性。
在一些实施方式中，所述负极膜层的压实密度小于等于1.55g/cm3，且大于等于1.40g/cm3。
在一些实施方式中，所述负极膜层的压实密度为1.40g/cm3、1.43g/cm3、1.46g/cm3、1.49g/cm3、1.52g/cm3、1.55g/cm3或任意二者间的数值范围。
合理范围内的极片膜层压实密度不但能够降低电池满充后在负极极片表面形成严重的黑斑的概率，还能够提高石墨材料颗粒在冷压过程中的完整度，维持极片内部的孔隙结构和较低的极片迂曲度，兼顾二次电池长的循环稳定性和高的动力学性能。
在一些实施方式中，所述石墨材料包括一次颗粒。在一些实施例中，基于所述石墨材料的颗粒总数量计，所述石墨材料中一次颗粒的数量占比大于等于85％。在一些实施例 中，基于所述石墨材料的颗粒总数量计，石墨材料中一次颗粒的数量占比为85％-100％。
在本文中，术语“一次颗粒”指非团聚态的颗粒。
在本公开中，石墨材料中的一次颗粒数量占比可以采用本领域已知的方法进行测试，作为示例，在负极膜层中任取一个测试样品，在该测试样品中任取多个测试区域，采用扫描电子显微镜获取多个测试区域的图像，统计各个图像中一次颗粒形貌的石墨材料颗粒的个数占石墨材料颗粒总个数的比例，多个统计结果的平均值即为石墨材料中的一次颗粒的数量占比。
在一些实施方式中，基于所述石墨材料的颗粒总数量计，所述石墨材料中一次颗粒的数量占比为85％、86％、87％、88％、89％、90％、91％、92％、93％、94％、95％、96％、97％、98％、99％、100％或任意二者间的数值范围。
相比于二次颗粒，一次颗粒可以有效降低晶界含量，减少石墨材料与电解液副反应的发生概率，提高极片的均一性，通过高比例的一次颗粒含量进一步改善二次电池的循环稳定性。
在一些实施方式中，所述石墨材料的Dv1为1.5微米(μm)-3.0μm。在一些实施例中，石墨材料的Dv1为1.6μm-2.8μm。
在本文中，术语“Dv1”、“Dv50”、“Dv90”、“Dv10”分别指在粒度分布曲线中，材料累计体积分布数达到1％、50％、90％、10％时所对应的粒径。
本公开中，石墨材料的体积分布粒径Dv1、Dv50、Dv90、Dv10可以采用本领域已知的方法进行测试，作为示例，参照GB/T 19077-2016，采用激光粒度分析仪进行测定。测试仪器可以为英国马尔文仪器有限公司的Mastersizer 3000型激光粒度分析仪。
在一些实施方式中，所述石墨材料的Dv1为1.5μm、1.6μm、1.7μm、1.8μm、1.9μm、2.0μm、2.1μm、2.2μm、2.3μm、2.4μm、2.5μm、2.6μm、2.7μm、2.8μm、2.9μm、3.0μm或任意二者间的数值范围。
申请人发现石墨材料的Dv1粒径对二次电池的电化学表现具有重要影响。石墨材料具有合适范围内的Dv1既能够使得负极膜层中具有一定比例的细粉，即小粒径石墨材料，有利于提高负极膜层的电接触，改善动力学性能，使得化成产气截至SOC提前，降低电池制备过程中产生严重黑斑的概率和电池循环使用时电化学表现发生“跳水”的概率；又可以减少小粒径石墨材料堵塞负极膜层孔隙的概率，维持正常的极片孔隙使得电解液具有高浸润性，降低负极析锂风险，进一步改善电池的循环稳定性。
在一些实施方式中，所述石墨材料的Dv50为12μm-16μm。在一些实施例中，石墨材料的Dv50为13μm-15μm。
在一些实施方式中，所述石墨材料的Dv50为12μm、13μm、14μm、15m、16m或任意二者间的数值范围。
该石墨材料具有大的体积分布粒径Dv50，有利于负极膜层的颗粒之间形成合理的孔道结构，有利于电解液充分浸润负极极片，减小极片局部极化的可能性，减少负极出现黑斑现象对电池的循环寿命和存储稳定性的影响。
在一些实施方式中，所述石墨材料的粒度分布(Dv90-Dv10)/Dv50为1.2-1.7。在一些实施例中，石墨材料的粒度分布(Dv90-Dv10)/Dv50为1.35-1.60。
在一些实施方式中，所述石墨材料的粒度分布(Dv90-Dv10)/Dv50为1.2、1.25、 1.3、1.35、1.4、1.45、1.5、1.55、1.6、1.65、1.7或任意二者间的数值范围。
粒度分布在上述范围内的石墨材料能够降低由于粒径差距较大引起的活性离子在石墨材料中分布不均匀，减少小粒径的石墨材料与电解液的副反应，改善二次电池的循环性能和存储稳定性。
在一些实施方式中，石墨材料的比表面积为0.6米2/克(m2/g)-1.5m2/g。在一些实施例中，石墨材料的比表面积为0.9m2/g-1.4m2/g。
本公开中，石墨材料的比表面积可以采用本领域已知的方法进行测试，作为示例，参照GB/T 19587-2017，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。测试仪器可以为美国Micromeritics公司的Tri-Star 3020型比表面积孔径分析测试仪。
在一些实施方式中，石墨材料的比表面积为0.6m2/g、0.7m2/g、0.8m2/g、0.9m2/g、1m2/g、1.1m2/g、1.2m2/g、1.3m2/g、1.4m2/g、1.5m2/g或任意二者间的数值范围。
石墨材料具有小的比表面积，能够减少石墨材料与电解液的副反应的发生概率，提高电池的循环性能和存储稳定性。
在一些实施方式中，石墨材料的吸油值小于等于45毫升(ml)/100克(g)。在一些实施例中，石墨材料的吸油值为30ml/100g-45ml/100g。
在本文中，术语“吸油值”是指100g石墨材料所能吸收的亚麻仁油的体积。例如，石墨材料的吸油值为40ml/100g是指100g的石墨材料能够吸收40ml的亚麻仁油。
石墨材料的吸油值可以采用本领域已知的方法和设备进行测试，示例如下：分别获取测试用油和石墨材料样品，并设置吸油值测试仪的扭矩阈值；将油恒速加入到吸油值测试仪混合室内的样品上，随着样品吸油量的增加，样品与油的混合物的黏度不断增加，当混合物的黏度达到吸油值测试仪预设的扭矩阈值时，停止并计算出单位质量的样品吸收油的体积，该值即为该样品的吸油值QI。其中试用油为亚麻仁油(DBP)，所述扭矩阈值为1牛(N)。
在一些实施方式中，石墨材料的吸油值为30ml/100g、31ml/100g、32ml/100g、33ml/100g、34ml/100g、35ml/100g、36ml/100g、37ml/100g、38ml/100g、39ml/100g、40ml/100g、41ml/100g、42ml/100g、43ml/100g、44ml/100g、45ml/100g或任意二者间的数值范围。
石墨材料的吸油值能够在一定程度上反映石墨材料在负极浆料中的分散性。石墨材料的吸油值大，意味着石墨材料在分散过程中需要浸润更多的分散剂，如羧甲基纤维素钠，浆料更容易沉降，导致极片涂布过程质量不稳定，冷压后极片厚度不均匀。吸油值在上述范围内的石墨材料既能够对于电解液具有良好的浸润性，使得二次电池具有良好的动力学性能和循环稳定性；又能够在搅拌过程中维持好的颗粒分散度，不容易因石墨材料对分散剂过多的吸附造成浆料沉降，使得极片涂布具有较宽的工艺窗口，极片具有良好的均一性。
在一些实施方式中，石墨材料的石墨化度为88％-93％。在一些实施例中，石墨材料的石墨化度为89％-92％。
在本文中，术语“石墨化度”指衡量碳原子形成密排六方石墨晶体结构的程度的指标。
本公开中，石墨材料的石墨化度可以采用本领域已知的方法进行测试，作为示例， 使用X射线衍射仪(如BrukerD8Discover)进行测试，参考JISK0131-1996、JB/T4220-2011，得到石墨材料晶体结构中(002)晶面的平均层间距d002，然后根据公式g＝(0.344-d002)/(0.344-0.3354)×100％计算得出石墨化度。上式中，d002是以纳米(nm)表示的石墨材料晶体结构中(002)晶面的平均层间距。
在一些实施方式中，石墨材料的石墨化度为88％、89％、90％、91％、92％、93％或任意二者间的数值范围。
控制石墨化程度在上述范围内既能够兼顾石墨材料的容量，又可以实现石墨活性材料在充电过程中较小的体积变化，有利于循环稳定性的进一步提高。
在一些实施方式中，负极膜层的面密度为7毫克/厘米2(mg/cm2)-14mg/cm2。在一些实施例中，负极膜层的面密度为9mg/cm2～12mg/cm2。
本公开中，负极膜层的面密度可以采用本领域已知的方法进行测试。作为示例，取经冷压后的负极极片，冲切成面积为S1的小圆片，称其重量，记录为M1。然后将上述称重后的负极极片的负极膜层擦拭掉，称量负极集流体的重量，记录为M0，负极膜层的面密度＝(负极极片的重量M1-负极集流体的重量M0)/S1。
在一些实施方式中，负极膜层的面密度为7mg/cm2、8mg/cm2、9mg/cm2、10mg/cm2、11mg/cm2、12mg/cm2、13mg/cm2、14mg/cm2或任意二者间的数值范围。
在一些实施方式中，石墨材料包括人造石墨。
在一些实施方式中，石墨材料的制备方法包括以下步骤：提供原料，原料包括石油焦、针状焦、沥青焦中的至少一种，基于原料结构的总体积计，原料中镶嵌型结构和区域型结构体积占比大于等于60％；处理原料获得中间品；对中间品进行石墨化处理得到石墨材料。
本文中，术语“石油焦”指石油渣油或者石油沥青经过高温碳化后形成的焦，称为石油焦。
本文中，术语“针状焦”指煤焦油沥青或者石油沥青，经过液相碳化生成各向异性中间相后，再经过高温碳化等工艺，可以生成针状纹理的焦。
本文中，术语“沥青焦”指煤焦油沥青经过高温碳化后生成的固体材料。
在一些实施方式中，所述原料包括石油焦。
石油焦具有优异的各向异性，有利于制备低石墨度、低膨胀的石墨材料，有利于电池的长循环寿命，同时石油焦具有高压实密度和高克容量，利于提高电池的能量密度，另外石油焦的来源更广泛，利于工业化生产。
上述原料通常包括镶嵌型、区域型和纤维型结构中的至少一种。通常，根据焦料在偏光显微镜下的形态特征和等色区尺寸，将尺寸小于30μm的等色区显微结构判定为镶嵌型；将尺寸大于30μm的等色区显微结构判定为区域型，将各向异性的条带状等色区判定为纤维型结构。
本公开中，原料中镶嵌型结构和区域型结构占比可以采用本领域已知的方法进行测试，作为示例，按GB 1997-89规定取原料，将破碎到1mm的原料混匀，缩分出40g～50g，采用方孔筛取0.07mm～1.0mm级试样4g～5g用于制片；按MT 116.1-86规定制备粉焦及块焦光片，粉焦光片直径不得小于22mm，其中胶结物所占体积应小于1/3；将试样放置在带有胶泥的载片上压平后置于载物台上准焦，校正显微镜后调节起偏镜、检 偏镜、使之正交。插入石青检板(1λ)，使视域呈现一级红的干涉色；确定移动尺步长，保证400个以上有效测点均匀分布，点距以0.3mm～0.5mm、行距一般以0.5mm～0.8mm为宜。从试样的一端开始，判定十字丝交点下的显微结构类别，以镶嵌型结构和区域型结构光学组织的有效测点数除以统计的总的测试点数作为原料中镶嵌型结构和区域型结构的体积占比。
在一些实施方式中，基于所述原料结构的总体积计，所述原料中镶嵌型结构和区域型结构体积占比为60％、65％、70％、75％、80％、85％、90％、95％、100％或任意二者间的数值范围。
原料中镶嵌型结构和区域型结构体积占比较高的前驱体具有较高的各向同性，利于制备石墨化度较低的石墨材料，降低晶格在充放电循环过程中的膨胀率，提高电池的循环稳定性。
在一些实施方式中，石墨化处理的功率为设备额定功率的70％-90％。
在一些实施例中，石墨化处理的功率为设备额定功率的70％、75％、80％、85％、90％或任意二者间的数值范围。可以理解，石墨化处理设备是指任何能够进行石墨化处理的装置，包括但不限于艾奇逊炉、箱式炉、内串炉、连续石墨化、电煅炉、中频炉、管式炉等装置。其中，不同厂家生产的石墨化处理设备的额定功率可能不同，可以根据实际情况自行选取即可。
本公开采用的石墨化处理功率需要低于石墨化处理设备的额定功率，以实现石墨化处理过程中温度场的均匀性。确保材料克容量的一致性，有利于提高电池的循环寿命。
在一些实施方式中，石墨化处理的最大功率为23000瓦(W)-25000W。
在一些实施例中，石墨化处理的最大功率为23000W、23500W、24000W、24500W、25000W或任意二者间的数值范围。
通过控制石墨化处理的最大功率能够有效控制石墨材料在热处理过程中的石墨化度，有利于提高电池的循环寿命。
在一些实施方式中，石墨化处理在最大功率时的恒功率时间为10小时(h)-50h。
在一些实施方式中，石墨化处理在最大功率时的恒功率时间为10h、13h、16h、19h、22h、25h、30h、35h、40h、45h、50h或任意二者间的数值范围。
在一些实施方式中，石墨化处理设备为内串炉，石墨化处理在最大功率的时间为10h-30h。
在一些实施方式中，石墨化处理设备为艾奇逊炉，石墨化处理在最大功率的时间为30h-50h。
合适的石墨化处理时间既不容易导致前驱体发生过度重排，造成石墨化处理后的石墨材料比表面积偏高，循环性能恶化；又能有效提高石墨材料的克容量，从而利于二次电池的能量密度和循环寿命的同步提高。
在一些实施方式中，所述处理原料具体包括以下步骤：破碎、整形和分级所述原料，获得二次原料；去除二次原料中一定比例的细粉，去除的细粉质量为二次原料总质量的15％-45％，得到前驱体，其中，细粉的Dv50为3μm-7μm，且Dv99小于等于30μm。
在一些实施例中，将原料进行破碎处理的在步骤中，可以使用破碎机，如颚式破碎机对原料进行破碎处理。例如可以先将原料破碎至设定粒径后再进行过筛处理，如3-20 目筛网。
在一些实施例中，将原料进行整形处理的在步骤中，可以使用整形机对破碎后的原料进行整形处理。整形处理可以减少破碎后的原料表面的毛刺，利于获得圆润的石墨材料。
在一些实施例中，将原料进行分级处理的在步骤中，可以使用气流分级机对整形后的原料进行分级处理。在一些实施例中，引风频率可以大于等于20赫兹(Hz)，分级频率可以大于等于65Hz。分级处理可以降低前驱体中的大颗粒和小颗粒的含量。
在一些实施例中，基于二次原料的总质量计，去除二次原料中的细粉比例为10％、15％、20％、25％、30％、35％中的任意值或其中任意两值组成的范围。
通过控制去除细粉比例在合适范围内，可以控制石墨材料的体积分布粒径Dv1在合适范围内，既能使得极片具有优异的吸液速率，电解液能充分浸润负极极片，还能使得石墨颗粒与石墨颗粒之间具有优异的电接触，综合改善电池的循环性能。
在一些实施方式中，前驱体的体积分布粒径Dv50为12μm-18μm。
在一些实施例中，前驱体的体积分布粒径Dv50为12μm、13μm、14μm、15μm、16μm、17μm、18μm或任意二者间的数值范围。
在一些实施方式中，前驱体的(Dv90-Dv10)/Dv50为1.3-2.0。
在一些实施例中，前驱体的(Dv90-Dv10)/Dv50为1.3、1.4、1.5、1.6、1.7、1.8、1.9、2.0或任意二者间的数值范围。
控制前驱体的体积分布粒径Dv50或(Dv90-Dv10)/Dv50在合适范围内，利于控制石墨材料的体积分布粒径Dv50或(Dv90-Dv10)/Dv50在合适范围内，可以提高电池的循环性能。
本公开对二次电池种类没有特别的限制，例如，二次电池可以为锂离子电池等。通常情况下，二次电池包括正极极片、负极极片以及电解质等。在二次电池充放电过程中，活性离子在所述正极极片和所述负极极片之间往返嵌入和脱出，所述电解质在所述正极极片和所述负极极片之间起到传导活性离子的作用。本公开对所述电解质的种类没有特别的限制，可根据实际需求进行选择。例如，所述电解质可以选自固态电解质及液态电解质(即电解液)中的至少一种。采用电解液的二次电池、以及一些采用固态电解质的二次电池中，还可以包括隔离膜，所述隔离膜设置在所述正极极片和所述负极极片之间，起到隔离的作用。
[负极极片]
在一些实施例中，所述负极极片包括负极集流体以及设置在所述负极集流体至少一个表面上的负极膜层。例如，所述负极集流体具有在自身厚度方向相对的两个表面，所述负极膜层设置在所述负极集流体的两个相对表面中的任意一者或两者上。
在一些实施例中，所述负极膜层包括本公开实施方式第一方面的石墨材料或通过本公开实施方式第二方面所述的方法制备得到的石墨材料。由此能使二次电池兼顾高首次库伦效率、高能量密度以及良好的循环性能和存储稳定性。
在一些实施例中，所述负极膜层还可以进一步包括除了上述石墨材料以外的其他负极活性材料。在一些实施例中，所述其他负极活性材料包括但不限于常规天然石墨、人造石墨、软碳、硬碳、硅基材料、锡基材料和钛酸锂中的一种或多种。所述硅基材料可 包括单质硅、硅氧化物、硅碳复合物、硅氮复合物和硅合金材料中的一种或多种。所述锡基材料可包括单质锡、锡氧化物和锡合金材料中的一种或多种。
在一些实施例中，所述负极膜层还包括负极导电剂。本公开对所述负极导电剂的种类没有特别的限制，作为示例，所述负极导电剂可包括超导碳、导电石墨、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯和碳纳米纤维中的一种或多种。
在一些实施例中，所述负极膜层还包括负极粘结剂。本公开对所述负极粘结剂的种类没有特别的限制，作为示例，所述负极粘结剂可包括丁苯橡胶(SBR)、水溶性不饱和树脂SR-1B、水性丙烯酸类树脂(例如，聚丙烯酸PAA、聚甲基丙烯酸PMAA、聚丙烯酸钠PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)和羧甲基壳聚糖(CMCS)中的一种或多种。
在一些实施例中，所述负极膜层还包括其他助剂。作为示例，其他助剂可包括增稠剂，例如，羧甲基纤维素钠(CMC)、PTC热敏电阻材料等。
在一些实施例中，所述负极集流体可采用金属箔片或复合集流体。作为金属箔片的示例，可采用铜箔。所述复合集流体可包括高分子材料基层以及形成于所述高分子材料基层至少一个表面上的金属材料层。作为示例，所述金属材料可包括铜、铜合金、镍、镍合金、钛、钛合金、银和银合金中的一种或多种。作为示例，所述高分子材料基层可包括聚丙烯(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)和聚乙烯(PE)中的一种或多种。
所述负极膜层通常是将负极浆料涂布在负极集流体上，经干燥、冷压而成的。所述负极浆料通常是将负极活性材料、导电剂、粘结剂、其他助剂分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)或去离子水，但不限于此。
所述负极极片并不排除除了所述负极膜层之外的其他附加功能层。例如，在一些实施例中，本公开所述的负极极片还包括夹在所述负极集流体和所述负极膜层之间、设置在所述负极集流体表面的导电底涂层(例如由导电剂和粘结剂组成)；在一些实施例中，本公开所述的负极极片还包括覆盖在所述负极膜层表面的保护层。
[正极极片]
在一些实施例中，所述正极极片包括正极集流体以及设置在所述正极集流体至少一个表面的正极膜层。例如，所述正极集流体具有在自身厚度方向相对的两个表面，所述正极膜层设置于所述正极集流体的两个相对表面中的任意一者或两者上。
所述正极集流体可采用金属箔片或复合集流体。作为金属箔片的示例，可采用铝箔。所述复合集流体可包括高分子材料基层以及形成于所述高分子材料基层至少一个表面上的金属材料层。作为示例，所述金属材料可包括铝、铝合金、镍、镍合金、钛、钛合金、银和银合金中的一种或多种。作为示例，所述高分子材料基层可包括聚丙烯(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)和聚乙烯(PE)中的一种或多种。
所述正极膜层通常包含正极活性材料、粘结剂和导电剂。所述正极膜层通常是将正极浆料涂布在所述正极集流体上，经干燥、冷压而成的。所述正极浆料通常是将正极活性材料、导电剂、粘结剂以及任意的其他组分分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)，但不限于此。作为示例，用于正极膜层的粘结剂可包 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-六氟丙烯共聚物和含氟丙烯酸酯树脂中的一种或多种。作为示例，用于正极膜层的导电剂包括超导碳、导电石墨、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯和碳纳米纤维中的一种或多种。
所述正极活性材料可采用本领域公知的用于二次电池的正极活性材料。
当本公开的二次电池为锂离子电池时，所述正极活性材料所述正极活性材料可包括但不限于含锂过渡金属氧化物、含锂磷酸盐及其各自的改性化合物中的一种或多种。所述锂过渡金属氧化物的示例可包括但不限于锂钴氧化物、锂镍氧化物、锂锰氧化物、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、锂镍钴铝氧化物及其各自的改性化合物中的一种或多种。所述含锂磷酸盐的示例可包括但不限于磷酸铁锂、磷酸铁锂与碳的复合材料、磷酸锰锂、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及其各自的改性化合物中的一种或多种。
在一些实施例中，为了进一步提高二次电池的能量密度，用于锂离子电池的正极活性材料可以包括通式为LiaNibCocMdOeAf的锂过渡金属氧化物及其改性化合物中的一种或多种。0.8≤a≤1.2，0.5≤b<1，0<c<1，0<d<1，1≤e≤2，0≤f≤1，M选自Mn、Al、Zr、Zn、Cu、Cr、Mg、Fe、V、Ti和B中的一种或多种，A选自N、F、S和Cl中的一种或多种。
在一些实施例中，作为示例，用于锂离子电池的正极活性材料可包括LiCoO2、LiNiO2、LiMnO2、LiMn2O4、LiNi1/3Co1/3Mn1/3O2(NCM333)、LiNi0.5Co0.2Mn0.3O2(NCM523)、LiNi0.6Co0.2Mn0.2O2(NCM622)、LiNi0.8Co0.1Mn0.1O2(NCM811)、LiNi0.85Co0.15Al0.05O2、LiFePO4和LiMnPO4中的一种或多种。
在本公开中，上述各正极活性材料的改性化合物可以是对所述正极活性材料进行掺杂改性和/或表面包覆改性。
[电解质]
在一些实施例中，所述电解质采用电解液，所述电解液包括电解质盐和溶剂。
所述电解质盐的种类不受具体的限制，可根据实际需求进行选择。
当本公开的二次电池为锂离子电池时，作为示例，所述电解质盐可包括六氟磷酸锂(LiPF6)、四氟硼酸锂(LiBF4)、高氯酸锂(LiClO4)、六氟砷酸锂(LiAsF6)、双氟磺酰亚胺锂(LiFSI)、双三氟甲磺酰亚胺锂(LiTFSI)、三氟甲磺酸锂(LiTFS)、二氟草酸硼酸锂(LiDFOB)、二草酸硼酸锂(LiBOB)、二氟磷酸锂(LiPO2F2)、二氟二草酸磷酸锂(LiDFOP)和四氟草酸磷酸锂(LiTFOP)中的一种或多种。
所述溶剂的种类不受具体的限制，可根据实际需求进行选择。在一些实施例中，作为示例，所述溶剂可包括碳酸乙烯酯(EC)、碳酸亚丙酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸亚丁酯(BC)、氟代碳酸乙烯酯(FEC)、甲酸甲酯(MF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸甲酯(MB)、丁酸乙酯(EB)、1,4-丁内酯(GBL)、环丁砜(SF)、二甲砜(MSM)、甲乙砜(EMS)和二乙砜(ESE)中的一种或多种。
在一些实施例中，所述电解液还包括添加剂。例如，所述添加剂可以包括负极成膜添加剂，也可以包括正极成膜添加剂，还可以包括能够改善二次电池某些性能的添加剂，例如改善二次电池过充性能的添加剂、改善二次电池高温性能的添加剂、改善二次电池低温功率性能的添加剂等。
[隔离膜]
本公开对所述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。
在一些实施例中，所述隔离膜的材质可以包括玻璃纤维、无纺布、聚乙烯、聚丙烯和聚偏二氟乙烯中的一种或多种。所述隔离膜可以是单层薄膜，也可以是多层复合薄膜。所述隔离膜为多层复合薄膜时，各层的材料相同或不同。
在一些实施例中，所述正极极片、所述隔离膜和所述负极极片可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施例中，所述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。
在一些实施例中，外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。外包装也可以是软包，例如袋式软包。所述软包的材质可以是塑料，如聚丙烯(PP)、聚对苯二甲酸丁二醇酯(PBT)和聚丁二酸丁二醇酯(PBS)中的一种或多种。
本公开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。如图1是作为一个示例的方形结构的二次电池5。
在一些实施例中，如图2所示，外包装可包括壳体51和盖板53。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用于盖设所述开口，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。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几个，可根据需求来调节。
本公开的二次电池的制备方法是公知的。在一些实施例中，可将正极极片、隔离膜、负极极片和电解液组装形成二次电池。作为示例，可将正极极片、隔离膜、负极极片经卷绕工艺或叠片工艺形成电极组件，将电极组件置于外包装中，烘干后注入电解液，经过真空封装、静置、化成、整形等工序，得到二次电池。
在本公开的一些实施例中，根据本公开的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多个，具体数量可根据电池模块的应用和容量来调节。
图3是作为一个示例的电池模块4的示意图。如图3所示，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。
在一些实施例中，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。
在一些实施例中，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根据电池包的应用和容量进行调节。
图4和图5是作为一个示例的电池包1的示意图。如图4和图5所示，在电池包1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2和下箱体3， 上箱体2用于盖设下箱体3，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。
用电装置
本公开还提供一种用电装置，所述用电装置包括本公开的二次电池、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。所述用电装置可以但不限于是移动设备(例如手机、平板电脑、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。
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6是作为一个示例的用电装置的示意图。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。
作为另一个示例的用电装置可以是手机、平板电脑、笔记本电脑等。该用电装置通常要求轻薄化，可以采用二次电池作为电源。
实施例
下述实施例更具体地描述了本公开公开的内容，这些实施例仅仅用于阐述性说明，因为在本公开公开内容的范围内进行各种修改和变化对本领域技术人员来说是明显的。除非另有声明，以下实施例中所报道的所有份、百分比、和比值都是基于质量计，而且实施例中使用的所有试剂都可商购获得或是按照常规方法进行合成获得，并且可直接使用而无需进一步处理，以及实施例中使用的仪器均可商购获得。
材料1
将镶嵌型和区域型结构占比为63.1％的石油焦进行粗破；之后将粗碎后的物料破碎、过筛，对过筛后的物料进行整形、分级，在分级过程中去掉一定含量的细粉，得到前驱体，其中去除的细粉占石油焦原料总质量的17％，得到的前驱体Dv50粒径为15.5μm，粒径分布(Dv90-Dv10)/Dv50为1.92；细粉是指Dv50为3μm-7μm，且Dv99小于等于30μm的组分。
将前驱体用艾奇逊炉进行石墨化处理，石墨化处理温度为2800℃，石墨化处理的最大功率为24000W，保持最大功率下处理40h后，将艾奇逊炉坩埚表面温度降温至400℃，将石墨坩埚取出，筛分除磁后获得石墨材料。
石墨材料的振实密度为1.21g/cm3，Dv1为1.8μm，Dv50为14.6μm，粒度分布(Dv90-Dv10)/Dv50为1.42，比表面积为1.14m2/g，石墨化度为91.1％。
材料2-5
材料2-5的制备方法与材料1类似，不同之处在于调整了去除细粉的比例以及前驱体的粒径分布。
材料调整参数以及具体材料性质如表1所示。
表1

实施例1
将上述制备的材料1、导电剂炭黑(Super P)、粘结剂丁苯橡胶、增稠剂羧甲基纤维素钠按照重量比95.4:1.8:1.0:1.8在适量的溶剂去离子水中充分搅拌混合，形成负极浆料。将负极浆料涂布在负极集流体铜箔的两个表面上，经干燥、冷压后，获得负极极片。负极膜层的压实密度为1.50g/cm3，面密度为9.4mg/cm2。
将正极活性材料磷酸铁锂(LFP)、导电剂Super P、粘结剂PVDF按质量比97:1:2进行混合，加入溶剂N-甲基吡咯烷酮NMP，在真空搅拌机作用下搅拌至体系呈均一状，获得正极浆料；将正极浆料均匀涂覆在正极集流体铝箔上，经过干燥、冷压、分切得到正极极片。所述正极膜层的压实密度为2.50g/cm3，面密度为20mg/cm2。
在水含量＜10ppm的氩气气氛手套箱中，将碳酸二乙酯(DEC)、碳酸甲乙酯(EMC)、碳酸乙烯酯(EC)按照重量比1:1:1进行混合得到有机溶剂，然后将LiPF6溶解于上述有机溶剂中，配制成浓度为1.0mol/L的电解液，然后加入碳酸亚乙烯酯(VC)，VC的含量为电解液总质量的2％。
采用聚丙烯薄膜作为隔离膜。
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、负极极片之间起到隔离的作用，然后卷绕得到电极组件；将电极组件置于外包装中，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2-6和对比例1-2
二次电池的制备方法与实施例1类似，不同之处在于采用了不同的石墨材料或调整了极片膜层的压实密度，详见表2。
性能测试
(1)化成截至荷电态(SOC)测试
在25℃下，将实施例和对比例制备得到的注液后电池进行0.33C充电，收集化成过程中产生的气体，当气体总量不增加时记录对应的SOC。
(2)黑斑情况测试
在25℃下，将上述各实施例和对比例的电池以0.33C恒流充电至电压为3.65V，在干燥房中进行拆解，观察负极极片的表面是否存在黑斑；黑斑总面积/负极极片总面积≤1％，且，单个极片中黑斑面积/单个极片面积≤8％定义为一级黑斑；1％＜黑斑总面积/负极极片总面积≤3％，或者，8％＜单个极片中黑斑面积/单个极片面积≤15％定义为二级黑斑；黑斑总面积/负极极片总面积＞3％，或者，单个极片中黑斑面积/单个极片面积＞15％，定义为三级黑斑。
(3)二次电池的循环性能测试
在60℃下，将上述各实施例和对比例的电池以1C恒流充电至电压为3.65V，之后以3.65V恒压充电至电流为0.05C，然后将电池以1C恒流放电至电压为2.5V，此为一个充放 电过程，记录首次循环的放电容量C1。如此反复进行充电和放电循环，直到电池容量衰减为初始容量C1的80％，记录循环圈数。
(4)二次电池的120天存储稳定性测试
在25℃的环境中，进行充放电测试，以0.5C恒流充电至3.65V，然后恒压充电至电流为0.05C，静置5min之后，将二次电池以0.5C恒流放电至2.5V，记录此时的放电容量，即为初始放电容量。而后将电芯满充置于60℃的环境下放置不同时间，每隔30天取出在25℃测试剩余容量，此为一个存储周期，此次的放电容量即为第1次存储后的放电容量。随后，重复第1次存储测试流程，记录存储过程中的放电容量值，并以120天后的放电容量/初始放电容量作为120天的存储容量保持率。
测试结果
按照上述方法分别制备各实施例和对比例的电池，并测量各项性能参数，结果见下表。
表2
由实施例和对比例的对比可见，二次电池中，负极膜层包括石墨材料，石墨材料的振实密度为1.2g/cm3-1.4g/cm3；且负极膜层的压实密度与石墨材料的振实密度的差值大于等于0.15g/cm3，能够在充分发挥高振实密度负极材料的优势，提高电池循环稳定性的同时降低负极黑斑的严重程度，进而改善电池的循环稳定性和存储稳定性。
由实施例1-4可见，石墨材料的Dv1为1.5μm-3.0μm时，电池的化成截至SOC进一步降低，循环稳定性进一步提高。化成是电池首次充电并激活电池内部电化学反应的过程。随着化成充电进行，锂离子从正极材料中脱嵌，通过电解液输运穿过隔膜到达负极并嵌入负极材料，从而在正负极之间形成电势差，将电能转化为电池的化学能。在化成电压达到一定值时，负极和电解液的固液界面上发生氧化还原反应，生成固态电解质界面膜(SEI膜)。化成截至SOC越高，在化成过程中充入的电量越高，形成SEI膜所消耗的锂离子越多，在电池负极产生黑斑的严重程度越大且电池首效越低。降低电池的化成截至SOC有利于降低负极黑斑的严重程度，改善电池的循环稳定性和高温存储稳定性。
需要说明的是，本公开不限定于上述实施方式。上述实施方式仅为示例，在本公开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 含在本公开的技术范围内。此外，在不脱离本公开主旨的范围内，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公开的范围内。

Claims (12)

  1. 一种二次电池，其特征在于，包括负极极片，所述负极极片包括负极集流体以及形成于所述负极集流体至少一个表面上的负极膜层，所述负极膜层包括石墨材料，所述石墨材料的振实密度为1.2g/cm3-1.4g/cm3；且所述负极膜层的压实密度与所述石墨材料的振实密度的差值大于等于0.15g/cm3。
  2. 根据权利要求1所述的二次电池，其特征在于，所述负极膜层的压实密度小于等于1.55g/cm3，且大于等于1.40g/cm3。
  3. 根据权利要求1或2所述的二次电池，其特征在于，所述石墨材料包括一次颗粒；可选地，基于所述石墨材料的颗粒总数量计，所述石墨材料中一次颗粒的数量占比大于等于85％，可选为85％-100％。
  4. 根据权利要求1至3中任一项所述的二次电池，其特征在于，所述石墨材料的Dv1为1.5μm-3.0μm，可选为1.6μm-2.8μm。
  5. 根据权利要求1至4中任一项所述的二次电池，其特征在于，所述石墨材料的Dv50为12μm-16μm，可选为13μm-15μm。
  6. 根据权利要求1至5中任一项所述的二次电池，其特征在于，所述石墨材料的粒度分布(Dv90-Dv10)/Dv50为1.2-1.70，可选为1.35-1.60。
  7. 根据权利要求1至6中任一项所述的二次电池，其特征在于，所述石墨材料的比表面积为0.6m2/g-1.5m2/g，可选为0.9m2/g-1.4m2/g。
  8. 根据权利要求1至7中任一项所述的二次电池，其特征在于，所述石墨材料的吸油值小于等于45ml/100g，可选为30ml/100g-45ml/100g。
  9. 根据权利要求1至8中任一项所述的二次电池，其特征在于，所述石墨材料的石墨化度为88％-93％，可选为89％-92％。
  10. 根据权利要求1至9中任一项所述的二次电池，其特征在于，所述负极膜层的面密度为7mg/cm2～14mg/cm2，可选为9mg/cm2～12mg/cm2。
  11. 根据权利要求1至10中任一项所述的二次电池，其特征在于，所述石墨材料包括人造石墨。
  12. 一种用电装置，包括权利要求1-11中任一项所述的二次电池。
PCT/CN2024/104988 2023-12-07 2024-07-11 二次电池及用电装置 Pending WO2025118596A1 (zh)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110350178A (zh) * 2019-07-12 2019-10-18 漳州巨铭石墨材料有限公司 一种锂离子电池复合石墨负极材料的制备方法
CN113207313A (zh) * 2019-12-03 2021-08-03 宁德时代新能源科技股份有限公司 二次电池、装置、人造石墨及制备方法
CN114122329A (zh) * 2021-11-11 2022-03-01 珠海冠宇电池股份有限公司 一种负极片和包括该负极片的锂离子电池
CN114156446A (zh) * 2021-11-11 2022-03-08 珠海冠宇电池股份有限公司 一种负极活性材料及含有该负极活性材料的负极片和锂离子电池

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108807974B (zh) * 2018-06-29 2021-07-09 宁德时代新能源科技股份有限公司 锂离子电池
PL3958353T3 (pl) * 2020-04-30 2023-10-23 Contemporary Amperex Technology Co., Limited Bateria wtórna, sposób jej wytwarzania i urządzenie zawierające baterię wtórną
CN114709415B (zh) * 2020-12-04 2024-11-22 宁德新能源科技有限公司 石墨材料、二次电池和电子装置
WO2023115530A1 (zh) * 2021-12-24 2023-06-29 宁德时代新能源科技股份有限公司 人造石墨及其制备方法及包含该人造石墨的二次电池和用电装置

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110350178A (zh) * 2019-07-12 2019-10-18 漳州巨铭石墨材料有限公司 一种锂离子电池复合石墨负极材料的制备方法
CN113207313A (zh) * 2019-12-03 2021-08-03 宁德时代新能源科技股份有限公司 二次电池、装置、人造石墨及制备方法
CN114122329A (zh) * 2021-11-11 2022-03-01 珠海冠宇电池股份有限公司 一种负极片和包括该负极片的锂离子电池
CN114156446A (zh) * 2021-11-11 2022-03-08 珠海冠宇电池股份有限公司 一种负极活性材料及含有该负极活性材料的负极片和锂离子电池

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