WO2025112368A1 - 二次电池以及用电装置 - Google Patents

二次电池以及用电装置 Download PDF

Info

Publication number
WO2025112368A1
WO2025112368A1 PCT/CN2024/095322 CN2024095322W WO2025112368A1 WO 2025112368 A1 WO2025112368 A1 WO 2025112368A1 CN 2024095322 W CN2024095322 W CN 2024095322W WO 2025112368 A1 WO2025112368 A1 WO 2025112368A1
Authority
WO
WIPO (PCT)
Prior art keywords
carbon
based material
secondary battery
negative electrode
optionally
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/CN2024/095322
Other languages
English (en)
French (fr)
Inventor
吴凯
李远源
沈睿
陈永红
何立兵
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Contemporary Amperex Technology Co Ltd
Original Assignee
Contemporary Amperex Technology Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Contemporary Amperex Technology Co Ltd filed Critical Contemporary Amperex Technology Co Ltd
Publication of WO2025112368A1 publication Critical patent/WO2025112368A1/zh
Anticipated expiration legal-status Critical
Pending legal-status Critical Current

Links

Classifications

    • 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
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H01G11/32—Carbon-based
    • 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
    • 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 power, wind power and solar power stations, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, aerospace and other fields. As the application scope of secondary batteries becomes wider and wider, people have also put forward higher requirements for their performance.
  • the present disclosure is made in view of the above-mentioned problems, and its object is to provide a secondary battery and an electric device, wherein the secondary battery has high energy density while achieving excellent cycle performance and dynamic performance.
  • a first aspect of the present disclosure provides a secondary battery, comprising a negative electrode plate, the negative electrode plate comprising a negative electrode current collector and a negative electrode film layer located on at least one surface of the negative electrode current collector and comprising a negative electrode active material, wherein the negative electrode active material comprises a first carbon-based material and a second carbon-based material, the first carbon-based material having a pore structure, and ID / IG of the first carbon-based material is less than or equal to 0.280, wherein ID represents the D peak intensity at 1350 ⁇ 50cm -1 in the Raman spectrum, IG represents the G peak intensity at 1580 ⁇ 50cm -1 in the Raman spectrum, and the second carbon-based material is an amorphous carbon material.
  • the negative electrode active material in the negative electrode film layer include a first carbon-based material and a second carbon-based material at the same time, the first carbon-based material has a pore structure, the ID / IG of the first carbon-based material is less than or equal to 0.280, and the second carbon-based material is an amorphous carbon material, thereby enabling the negative electrode plate to have a high compaction density, low volume change performance and high active ion transmission rate, so that the secondary battery using the negative electrode plate can have a high energy density while taking into account excellent cycle performance and kinetic performance.
  • the ID / IG of the first carbon-based material is 0.155-0.220; thus, it is more conducive to the battery to have excellent energy density, cycle performance and kinetic performance.
  • the ID / IG of the second carbon-based material is less than or equal to 0.250, and optionally, the ID / IG of the second carbon-based material is less than or equal to 0.230. This is more conducive to the battery having both excellent cycle performance and higher energy density.
  • the Dv50 of the first carbon-based material is greater than the Dv50 of the second carbon-based material, thereby being more conducive to improving the energy density and kinetic performance of the battery.
  • the X-ray powder diffraction pattern of the first carbon-based material has diffraction peaks at 2 ⁇ diffraction angles of 26.5° ⁇ 0.2°, 44.5° ⁇ 0.2°, and 54.6° ⁇ 0.2°, and there is no obvious diffraction peak in the X-ray powder diffraction pattern of the second carbon-based material.
  • the secondary battery can have high energy density while taking into account excellent cycle performance and kinetic performance.
  • the first carbon-based material has lattice fringes in HR-TEM, and the second carbon-based material has no lattice fringes in HR-TEM.
  • the secondary battery can have high energy density while taking into account excellent cycle performance and kinetic performance.
  • the powder compaction density of the first carbon-based material under a pressure of 20000N is greater than the powder compaction density of the second carbon-based material under a pressure of 20000N. This is conducive to making the secondary battery have both high energy density and good kinetics. able.
  • the true density of the first carbon-based material is 2.22 g/cm 3 -2.27 g/cm 3 , and can be 2.23 g/cm 3 -2.26 g/cm 3 .
  • the first carbon-based material includes one or more pore structures with an area greater than or equal to 0.15 ⁇ m 2 , and optionally includes one or more pore structures with an area of 0.15 ⁇ m 2-2.0 ⁇ m 2.
  • the pore structure can reserve sufficient and stable expansion space for the volume change of the first carbon-based material and/or the second carbon-based material particles, reduce the risk of crushing the first carbon-based material and/or the second carbon-based material particles, reduce the occurrence of side reactions, and improve the cycle performance of the secondary battery.
  • the first carbon-based material includes an outer region and an inner region located inside the outer region
  • the outer region refers to a region extending from the particle surface of the first carbon-based material to the inside of the particle by a distance of 2.5 ⁇ m
  • the total pore area of the outer region is recorded as S1
  • the total pore area of the inner region is recorded as S2
  • S2>S1 optionally, 2.6 ⁇ S2/S1 ⁇ 450.7.
  • the pore area S1 of the outer region of the first carbon-based material is smaller than the pore area S2 of the inner region, indicating that the structure of the outer region of the carbon-based material is denser than that of the inner region, thereby enabling the secondary battery to better balance high energy density and good cycle performance.
  • the area of the pore structure in the outer region of the first carbon-based material is less than or equal to 0.15 ⁇ m2, optionally less than or equal to 0.13 ⁇ m2 , and/or, the inner region of the first carbon-based material includes one or more pore structures with an area greater than or equal to 0.15 ⁇ m2, optionally including one or more pore structures with an area of 0.15 ⁇ m2-2.0 ⁇ m2 .
  • the outer region of the first carbon-based material can have a dense structure, thereby effectively improving the structural stability of the first carbon-based material, avoiding the electrolyte from penetrating into the pore structure inside the first carbon-based material particles as much as possible, and thus effectively improving the cycle performance of the secondary battery.
  • the inner region of the first carbon-based material include a pore structure of the above size, on the one hand, sufficient and stable expansion space can be reserved for the volume change of the first carbon-based material particles, reducing the risk of crushing of the first carbon-based material particles, and reducing the occurrence of side reactions.
  • the compaction density of the negative electrode film layer can also be improved to buffer the volume change of the negative electrode film layer.
  • the powder compaction density of the first carbon-based material under a pressure of 20000N is 1.65g/cm 3 -2.0g/cm 3 , and can be 1.68g/cm 3 -1.98g/cm 3 , which is beneficial to improve the energy density of the secondary battery.
  • the volume distribution particle size Dv50 of the first carbon-based material is 8.0 ⁇ m-25.0 ⁇ m, and can be 10.0 ⁇ m-22.0 ⁇ m. In some embodiments, the volume distribution particle size Dv90 of the first carbon-based material is 16.0 ⁇ m-45.0 ⁇ m, and can be 16.5 ⁇ m-42.0 ⁇ m.
  • volume distribution particle size Dv50 and/or Dv90 of the first carbon-based material within the above range, it is beneficial to improve the transmission performance of active ions and electrons, thereby further improving the kinetic performance of the secondary battery. It can also reduce the occurrence of side reactions and improve the cycle performance of the secondary battery.
  • the particle size distribution (Dv90-Dv10)/Dv50 of the first carbon-based material is less than or equal to 1.55, and can be selected as 0.90-1.50.
  • the particle size distribution (Dv90-Dv10)/Dv50 of the first carbon-based material within the above range, its particle stacking performance is good, which is conducive to improving the compaction density of the negative electrode film layer, thereby further improving the energy density of the secondary battery; in addition, it is also conducive to adjusting the pore distribution of the negative electrode film layer, improving the active ion and electron transport performance, and improving the infiltration and retention characteristics of the negative electrode film layer to the electrolyte, thereby improving the kinetic performance and cycle performance of the secondary battery.
  • the tap density of the first carbon-based material is 0.85 g/cm 3 -1.30 g/cm 3 , and can be 0.90 g/cm 3 -1.25 g/cm 3 .
  • the graphitization degree of the first carbon-based material is greater than or equal to 95.5%, and can be 95.5%-98.0%.
  • the secondary battery can have a high energy density.
  • the first carbon-based material and/or the second carbon-based material include primary particles.
  • the number of the primary particles in the first carbon-based material accounts for greater than or equal to 80%
  • the number of the primary particles in the second carbon-based material accounts for greater than or equal to 80%.
  • the true density of the second carbon-based material is 1.95 g/cm 3 -2.22 g/cm 3 , and can be 1.97 g/cm 3 -2.21 g/cm 3 .
  • the specific surface area of the second carbon-based material is greater than or equal to 1.5 m 2 /g, and can be 1.9 m 2 /g-7.5 m 2 /g.
  • the Dv50 of the second carbon-based material is 4.0 ⁇ m-15.0 ⁇ m, and can be 5.0 ⁇ m-15.0 ⁇ m.
  • the powder compaction density of the second carbon-based material under a pressure of 20000 N is 0.85 g/cm 3 -1.35 g/cm 3 , and can be 0.90 g/cm 3 -1.30 g/cm 3 .
  • the powder compaction density of the second carbon-based material is lower than the powder compaction density of the first carbon-based material.
  • the tap density of the second carbon-based material is 0.80 g/cm 3 -1.20 g/cm 3 , and can be 0.83 g/cm 3 -1.15 g/cm 3 .
  • it is beneficial to have a suitable pore distribution in the negative electrode film layer improve the active ion transport performance, improve the wetting characteristics of the negative electrode film layer to the electrolyte, and thus improve the kinetic performance and cycle performance of the secondary battery.
  • the gram capacity of the second carbon-based material is 330 mAh/g-480 mAh/g, and can be 340 mAh/g-470 mAh/g.
  • At least part of the surface of the first carbon-based material and/or the second carbon-based material has a carbon coating layer.
  • the coating layer includes a carbon coating layer. This is conducive to improving the speed of active ion embedding into the negative electrode film layer, improving the active ion transport performance of the negative electrode film layer, and thus improving the kinetic performance of the secondary battery.
  • the content of the first carbon-based material in the negative electrode active material is greater than or equal to 40wt%, optionally 50wt%-80wt%.
  • the secondary battery has high energy density while having good processing performance, dynamic performance and cycle performance.
  • the negative electrode active material further comprises a silicon-based material, and optionally, in the negative electrode active material, the content of the silicon-based material is 3wt%-30wt%.
  • the silicon-based material has a higher lithium insertion potential, which is beneficial to improving the kinetic performance of the secondary battery; at the same time, it can also improve the negative electrode capacity, thereby further improving the energy density of the secondary battery.
  • the compaction density of the negative electrode film layer is 1.40g/cm 3 -1.70g/cm 3 , and can be 1.45g/cm 3 -1.67g/cm 3 , which is beneficial for the negative electrode film layer to have high capacity, high active ion and electron transport performance, and further beneficial for the secondary battery to have high energy density and good cycle performance and kinetic performance.
  • the surface density of the negative electrode film layer is 5.0mg/ cm2-25.0mg / cm2 , and can be 5.5mg/ cm2-22.5mg / cm2 . This is beneficial for the negative electrode film layer to have high capacity, high active ion and electron transport performance, and further beneficial for the secondary battery to have high energy density and good cycle performance and kinetic performance.
  • the thickness of the negative electrode film layer is 40 ⁇ m-120 ⁇ m, and optionally 45 ⁇ m-100 ⁇ m.
  • a second aspect of the present disclosure provides an electric device, which includes the secondary battery according to the first aspect of the present disclosure.
  • the secondary battery of the present disclosure has high energy density and has excellent cycle performance and kinetic performance.
  • FIG. 1 is a schematic diagram of a cross-sectional image of a particle of a first carbon-based material of the present disclosure.
  • FIG. 2 is a SEM image of an embodiment of a negative electrode sheet of the present disclosure.
  • FIG. 3 is a schematic diagram of an embodiment of a secondary battery of the present disclosure.
  • FIG. 4 is an exploded schematic diagram of an embodiment of a secondary battery of the present disclosure.
  • FIG. 5 is a schematic diagram of an embodiment of a battery module of the present disclosure.
  • FIG. 6 is a schematic diagram of an embodiment of a battery pack of the present disclosure.
  • FIG. 7 is an exploded schematic diagram of the embodiment of the battery pack shown in FIG. 6 .
  • FIG. 8 is a schematic diagram of an embodiment of an electric device including the secondary battery of the present disclosure as a power source.
  • “Scope” disclosed in the present disclosure is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range.
  • the scope limited in this way can be including end values or not including end values, and can be arbitrarily combined, that is, any lower limit can form a scope with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for a particular parameter, it is understood that the scope of 60-110 and 80-120 is also expected.
  • the numerical range "a-b" represents the abbreviation of any real number combination between a and b, wherein a and b are 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.
  • a first aspect of an embodiment of the present disclosure provides a secondary 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 located on at least one surface of the negative electrode current collector and including a negative electrode active material, wherein the negative electrode active material includes a first carbon-based material and a second carbon-based material, the first carbon-based material has a pore structure, and the ID / IG of the first carbon-based material is 0.152-0.280, wherein ID represents the Raman spectrum at 1350 IG represents the D peak intensity at 1580 ⁇ 50cm -1 , IG represents the G peak intensity at 1580 ⁇ 50cm -1 of the Raman spectrum, and the second carbon-based material is an amorphous carbon material.
  • the first carbon-based material has a pore structure means that the first carbon-based material has a pore structure that can be directly observed from a cross-sectional image (e.g., a scanning electron microscope image with a magnification of 1000 times), that is, the pore structure in the main structure used to prepare the first carbon-based material is not completely filled.
  • a cross-sectional image e.g., a scanning electron microscope image with a magnification of 1000 times
  • amorphous carbon materials For amorphous carbon materials, the interlayer spacing is large, which is conducive to the rapid deintercalation of active ions, and has a higher potential for lithium, which is conducive to improving the kinetic performance of the battery.
  • amorphous carbon materials have high surface activity and are prone to side reactions with electrolytes. During the first charge, they consume more active lithium ions, which reduces the active ions of the secondary battery, reduces the capacity of the secondary battery, and reduces the energy density of the secondary battery. Therefore, the application of amorphous carbon materials in batteries is limited.
  • the negative electrode active material disclosed in the present invention includes a first carbon-based material and a second carbon-based material amorphous carbon.
  • the first carbon-based material has a pore structure, which is equivalent to reserving a certain space inside the material, so that the compaction density of the pole piece is effectively improved during the preparation of the pole piece, thereby improving the energy density of the battery.
  • the ID / IG of the first carbon-based material is within a specific range, and the surface of the carbon-based material has less disordered carbon, so that the material has higher chemical stability, can reduce the occurrence of side reactions, and can effectively reduce the consumption of active ions during the first charge, which can further improve the battery energy density and cycle performance. As a result, the battery can have both higher energy density and cycle performance while having better dynamics.
  • the ID / IG of the first carbon-based material is 0.155-0.220; thereby, excellent energy density, cycle performance and kinetic performance can be better balanced.
  • the ID / IG of the second carbon-based material is less than or equal to 0.250, and optionally, the ID / IG of the second carbon-based material is less than or equal to -0.230.
  • the cycle performance and energy density of the battery can be further improved.
  • the X-ray powder diffraction pattern of the first carbon-based material has diffraction peaks at 2 ⁇ diffraction angles of 26.5° ⁇ 0.2°, 44.5° ⁇ 0.2°, and 54.6° ⁇ 0.2°. There is no obvious diffraction peak in the X-ray powder diffraction pattern of the second carbon-based material.
  • the HR-TEM spectrum of the first carbon-based material contains lattice fringes, which indicates that the carbon material has a crystalline structure.
  • the second carbon-based material may be soft carbon, or hard carbon.
  • the powder compaction density of the above-mentioned first carbon-based material under a pressure of 20000N is greater than the powder compaction density of the above-mentioned second carbon-based material under a pressure of 20000N.
  • the powder compaction density of the first carbon-based material is relatively large, which is beneficial to improving the compaction density of the negative electrode film layer and improving the energy density of the secondary battery.
  • the powder compaction density of the second carbon-based material is relatively small, which is beneficial to improving the porosity of the pole piece, improving the embedding and deintercalation of active ions, and thus improving the kinetic performance of the secondary battery. Therefore, by adjusting the powder compaction density of the first carbon-based material to be greater than the powder compaction density of the second carbon-based material, it is beneficial to make the secondary battery have both high energy density and good kinetic performance.
  • the true density of the first carbon-based material is greater than the true density of the second carbon-based material, which is beneficial for the secondary battery to have both high energy density and good kinetic performance.
  • the true density of the first carbon-based material is 2.22 g/cm 3 -2.27 g/cm 3 , and can be 2.23 g/cm 3 -2.26 g/cm 3 .
  • the energy density of the secondary battery can be further improved.
  • the volume distribution particle size Dv50 of the first carbon-based material is greater than the volume distribution particle size Dv50 of the second carbon-based material.
  • the tap density of the first carbon-based material is greater than the tap density of the second carbon-based material.
  • the processing performance of the battery can be further improved.
  • the first carbon-based material includes one or more pore structures with an area greater than or equal to 0.15 ⁇ m 2 , and optionally includes one or more pore structures with an area of 0.15 ⁇ m 2 -2.0 ⁇ m 2.
  • the first carbon-based material and/or the second carbon-based material include a pore structure with the above pore area, sufficient and stable expansion space can be reserved for the volume change of the first carbon-based material particles and/or the second carbon-based material, reducing the risk of crushing of the first carbon-based material and/or the second carbon-based material particles, reducing the occurrence of side reactions, and improving the cycle performance of the secondary battery.
  • the compaction density of the negative electrode film layer can also be increased, and the energy density of the secondary battery can be increased.
  • the first carbon-based material includes an outer region and an inner region located inside the outer region
  • the outer region refers to a region extending 2.5 ⁇ m from the particle surface of the first carbon-based material to the inside of the particle, in the cross-sectional view of the first carbon-based material, the total pore area of the outer region is recorded as S1 , the total pore area of the inner region is recorded as S2, and S2>S1.
  • inner region refers to the region other than the outer region in the material particle.
  • the first carbon-based material satisfies S2>S1
  • the structure of the outer region of the carbon-based material is denser than that of the inner region, and the first carbon-based material further has the following characteristics: the inner region has a large number of pores and/or a large pore size, while the outer region has a small number of pores and/or a small pore size.
  • the pore structure of the inner region of the first carbon-based material can reserve the required expansion space for the particle volume change, thereby reducing the particle breakage.
  • the risk of new interface generated by the first carbon-based material is reduced, the rebound rate of the thickness of the negative electrode film layer is reduced, and the occurrence of side reactions is reduced; the number of pores in the outer region of the first carbon-based material is small and/or the pore size is small, so that the first carbon-based material particles have a stable structure and the electrolyte is prevented from penetrating into the pore structure inside the first carbon-based material particles as much as possible, thereby further reducing the occurrence of side reactions and reducing the consumption of active ions by the formation of the SEI film inside the particles. Therefore, when the first carbon-based material satisfies S2>S1, the first coulomb efficiency of the secondary battery can be improved, and the cycle performance of the secondary battery can be further improved.
  • 2.6 ⁇ S2/S1 ⁇ 450.7 for example, 3 ⁇ S2/S1 ⁇ 430, 4 ⁇ S2/S1 ⁇ 400, 5 ⁇ S2/S1 ⁇ 350, 6 ⁇ S2/S1 ⁇ 300, 7 ⁇ S2/S1 ⁇ 250, 8 ⁇ S2/S1 ⁇ 200.
  • the total pore area S1 of the outer region and the total pore area S2 of the inner region of the first carbon-based material can be obtained by testing the cross-sectional image of the first carbon-based material.
  • Fig. 1 is a schematic diagram of a cross-sectional image of a particle of the first carbon-based material 100 of the present disclosure. As shown in Fig. 1, the region extending 2.5 ⁇ m from the particle surface of the first carbon-based material 100 to the inside of the particle is the outer region 101, and the region inside the outer region 101 is the inner region 102.
  • the pore area, S1, and S2 values of the first carbon-based material can be obtained by using a cross-section polisher (such as the IB-09010CP argon ion cross-section polisher produced by JEOL of Japan) to obtain the cross-section of the first carbon-based material; then, referring to JY/T010-1996, a scanning electron microscope (such as the Sigma 300 scanning electron microscope produced by ZEISS of Germany) is used to scan the cross-section of the first carbon-based material; finally, image processing software (such as AVIZO) is used to obtain the pore area of any hole in the first carbon-based material, as well as the total pore area S2 of the inner region and the total pore area S1 of the outer region, and thereby the value of S2/S1 is obtained.
  • a cross-section polisher such as the IB-09010CP argon ion cross-section polisher produced by JEOL of Japan
  • a scanning electron microscope such as the Sigma 300 scanning electron microscope produced by ZE
  • samples can be obtained from different regions of the negative electrode sheet in the secondary battery, and at least 5 positions (such as 5, 10, 15 or even more) are randomly selected from the sample to obtain cross sections using a cross-section polisher, and at least 10 particles (such as 10, 20, 50 or even more particles) are randomly selected from the scanning electron microscope images of each cross section.
  • the total pore area S2' and the total pore area S1' of the inner region of each particle cross section are obtained by image processing software according to the above definition, and the S2'/S1' value of each particle cross section is obtained.
  • the arithmetic mean of S2'/S1' of all the measured particle cross sections is calculated as the S2/S1 value of the first carbon-based material.
  • the area of the above-mentioned pore structure in the outer region of the above-mentioned first carbon-based material is less than or equal to 0.15 ⁇ m2 , and can be optionally less than or equal to 0.13 ⁇ m2 .
  • the inventors also found in further research that by controlling the area of the pore structure in the outer region of the first carbon-based material within the above-mentioned range, the outer region of the first carbon-based material can have a dense structure, thereby effectively improving the structural stability of the first carbon-based material, and avoiding the electrolyte from penetrating into the pore structure inside the first carbon-based material particles as much as possible, thereby effectively improving the cycle performance of the secondary battery.
  • the present disclosure is not intended to limit the area of all pore structures in the outer region of the first carbon-based material to be less than or equal to 0.15 ⁇ m2 .
  • the area of the pore structure can be controlled to be less than or equal to 0.15 ⁇ m2 for more than 95%, and optionally more than 99%.
  • the internal region of the first carbon-based material includes one or more pore structures with an area greater than or equal to 0.15 ⁇ m 2 , and optionally includes one or more pore structures with an area of 0.15 ⁇ m 2 -2.0 ⁇ m 2.
  • the inventors have also found in further research that by making the internal region of the first carbon-based material include pore structures of the above size, on the one hand, sufficient and stable expansion space can be reserved for the volume change of the first carbon-based material particles, reducing the risk of crushing of the first carbon-based material particles and reducing the occurrence of side reactions, and on the other hand, the compaction density of the negative electrode film layer can be improved to buffer the volume change of the negative electrode film layer.
  • the powder compaction density of the first carbon-based material under a pressure of 20000 N is 1.65 g/cm 3 -2.0 g/cm 3 , and can be 1.68 g/cm 3 -1.98 g/cm 3 .
  • the battery can better balance energy density and dynamic performance.
  • the volume distribution particle size Dv50 of the first carbon-based material is 8.0 ⁇ m-25.0 ⁇ m, and can be 10.0 ⁇ m-22.0 ⁇ m. In some embodiments, the volume distribution particle size Dv90 of the first carbon-based material is 16.0 ⁇ m-45.0 ⁇ m, and can be 16.5 ⁇ m-42.0 ⁇ m.
  • volume distribution particle size Dv50 and/or Dv90 of the first carbon-based material is within the above range, it is beneficial to improve the transmission performance of active ions and electrons, thereby further improving the kinetic performance of the secondary battery. In addition, it can also reduce the occurrence of side reactions and improve the cycle performance of the secondary battery.
  • the particle size distribution (Dv90-Dv10)/Dv50 of the first carbon-based material is less than or equal to 1.55, and can be optionally 0.90-1.50.
  • the particle size distribution (Dv90-Dv10)/Dv50 of the first carbon-based material is within the above range, its particle stacking performance is good, which is conducive to improving the compaction density of the negative electrode film layer, thereby further improving the energy density of the secondary battery; in addition, it is also conducive to adjusting the pore distribution of the negative electrode film layer, improving the active ion and electron transport performance, and improving the infiltration and retention characteristics of the negative electrode film layer to the electrolyte, thereby improving the kinetic performance and cycle performance of the secondary battery.
  • the tap density of the first carbon-based material is 0.85 g/cm 3 -1.30 g/cm 3 , and may be 0.90 g/cm 3 -1.25 g/cm 3 .
  • the tap density of the first carbon-based material is within the above range, it is beneficial to improve processing performance.
  • the graphitization degree of the first carbon-based material is greater than or equal to 95.5%, and can be 95.5%-98.0%. Adjusting the graphitization degree of the first carbon-based material within the above range can make the secondary battery have a higher energy density.
  • the particles of amorphous carbon materials are usually harder and have more edges and corners, poor processing performance, poor adhesion to the current collector, and require greater cold pressing pressure during pole piece processing, which can easily cause damage to the current collector.
  • the cold pressing pressure during pole piece processing can be reduced, thereby reducing damage to the current collector, reducing the risk of current collector cracking during battery cycling, and further improving the safety performance of the battery.
  • the first carbon-based material and/or the second carbon-based material include primary particles.
  • the number of the primary particles in the first carbon-based material is greater than or equal to 80%, for example, it can be 80%-100%, 85%-90%, 80%-90%, 80%-100%, 85%-90%, 80%-100%, 90%-100%, or 95%-100%.
  • the number of the primary particles in the second carbon-based material is greater than or equal to 80%, for example, it can be 80%-100%, 85%-90%, 80%-90%, 80%-100%, 85%-90%, 80%-100%, 90%-100%, or 95%-100%.
  • the first carbon-based material and/or the second carbon-based material contain an appropriate proportion of primary particles, which can make it have a higher structural stability and reduce the occurrence of side reactions, thereby improving the cycle performance of the secondary battery.
  • the true density of the second carbon-based material is 1.95 g/cm 3 -2.22 g/cm 3 , and can be 1.97 g/cm 3 -2.21 g/cm 3 .
  • the specific surface area of the second carbon-based material is greater than or equal to 1.5 m 2 /g, and can be 1.9 m 2 /g-7.5 m 2 /g.
  • the Dv50 of the second carbon-based material is 4.0 ⁇ m-15.0 ⁇ m, and can be 5.0 ⁇ m-15.0 ⁇ m.
  • the particle size distribution (Dv90-Dv10)/Dv50 of the second carbon-based material is less than or equal to 1.75, and can be selected as 1.1-1.75.
  • the particle size distribution (Dv90-Dv10)/Dv50 of the second carbon-based material is within the above range, its particle stacking performance is good, which is beneficial to improve the compaction density of the negative electrode film layer and the energy density of the secondary battery; in addition, it is also beneficial to form a reasonable pore structure between the particles of the negative electrode film layer, improve the active ion and electron transport performance in the negative electrode film layer, and thus improve the kinetic performance of the secondary battery.
  • the powder compaction density of the second carbon-based material under a pressure of 20000N is 0.85g/ cm3-1.35g / cm3 , and can be 0.90g/ cm3-1.30g / cm3 .
  • the powder compaction density of the second carbon-based material is lower than the powder compaction density of the first carbon-based material.
  • the tap density of the second carbon-based material is 0.80 g/cm 3 -1.20 g/cm 3 , and can be 0.83 g/cm 3 -1.15 g/cm 3 , which can make the secondary battery better balance the processing performance and the dynamic performance.
  • the gram capacity of the second carbon-based material is 330 mAh/g-480 mAh/g, and can be 340 mAh/g-470 mAh/g.
  • At least part of the surface of the first carbon-based material and/or the second carbon-based material has a carbon coating.
  • the coating includes a carbon coating.
  • more than 80% of the surface of the first carbon-based material and/or the second carbon substrate is covered with a carbon coating, and further, 90%-100% of the surface is covered with a carbon coating. This is conducive to improving the speed of active ion embedding into the negative electrode film layer, improving the active ion transport performance of the negative electrode film layer, and thus improving the kinetic performance of the secondary battery.
  • the coating layer of the first carbon-based material can be prepared as follows: the first carbon-based material is mixed with an organic carbon source and then carbonized to form a carbon coating layer on at least part of the surface of the particle.
  • the organic carbon source can be a carbon-containing material known in the art suitable for coating, for example, it can include one or more of coal tar, petroleum asphalt, epoxy resin, phenolic resin, high molecular polymer, etc.
  • the carbonization temperature is 900°C-1300°C.
  • the coating layer of the second carbon-based material can be prepared by the following method: Method 1: Depositing carbon material on the surface of the second carbon-based material at a temperature of 1200-1600°C by chemical vapor deposition, the gas is one of methane, ethylene, and acetylene; Method 2: Mixing the second carbon-based material with a coating agent and heat treating it at a temperature of 1600-2600°C, the coating agent is one or more of asphalt or polymer.
  • Method 1 Depositing carbon material on the surface of the second carbon-based material at a temperature of 1200-1600°C by chemical vapor deposition, the gas is one of methane, ethylene, and acetylene
  • Method 2 Mixing the second carbon-based material with a coating agent and heat treating it at a temperature of 1600-2600°C, the coating agent is one or more of asphalt or polymer.
  • the content of the first carbon-based material in the negative electrode active material is greater than or equal to 40wt%, optionally 50wt%-80wt%, for example, 55wt%-75wt%, 60wt%-70wt%.
  • the secondary battery can take into account high energy density, good kinetic performance and cycle performance.
  • the content of the second carbon-based material in the negative electrode active material can be 20wt%-50wt%, optionally 25wt%-45wt%, 30wt%-40wt%.
  • the negative electrode active material may further include, in addition to the first carbon-based material and the second silicon-based material
  • the negative electrode active materials may also include silicon-based materials, which have a higher lithium insertion potential. It is beneficial to improve the kinetic performance of the secondary battery; at the same time, it can also improve the negative electrode capacity, thereby further improving the energy density of the secondary battery.
  • the silicon-based material may include one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite and silicon alloy material.
  • the negative electrode active material in the negative electrode film layer further includes a silicon-based material
  • the content of the silicon-based material is 3wt%-30wt%, for example, 4wt%-25wt%, 5wt%-20wt%.
  • the negative electrode film layer may further include 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 may further include a negative electrode binder.
  • the negative electrode binder may include styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based 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
  • PAM polyacrylamide
  • PVA polyvinyl alcohol
  • SA sodium alginate
  • CMCS carboxymethyl chitosan
  • the negative electrode film layer may further include other additives.
  • the other additives may include a thickener, such as sodium carboxymethyl cellulose (CMC), a PTC thermistor material, and the like.
  • the compaction density of the negative electrode film is 1.40g/cm 3 -1.70g/cm 3 , and can be 1.45g/cm 3 -1.67g/cm 3 , which is beneficial for the negative electrode film to have high capacity, high active ion and electron transport performance, and further beneficial for the secondary battery to have high energy density and good cycle performance and kinetic performance.
  • the surface density of the negative electrode film is 5.0mg/ cm2-25.0mg / cm2 , and can be 5.5mg/ cm2-22.5mg / cm2 . This is beneficial for the negative electrode film to have high capacity, high active ion and electron transport performance, and further for the secondary battery to have high energy density and good cycle performance and kinetic performance.
  • the thickness of the negative electrode film layer is 40 ⁇ m-120 ⁇ m, and optionally 45 ⁇ m-100 ⁇ m.
  • 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 current collector has two surfaces opposite to each other in the thickness direction thereof, 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 parameters of the negative electrode film layer (such as compaction density, surface density, thickness, etc.) given in the present disclosure refer to the parameters of the negative electrode film layer on one side of the negative electrode current collector.
  • the parameters of the negative electrode film layer on either side satisfy the present disclosure, and are considered to fall within the protection scope of the present disclosure.
  • the negative electrode sheet may include other additional functional layers in addition to the negative electrode film layer.
  • the negative electrode sheet also 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 sheet also includes a protective layer covering the surface of the negative electrode film layer.
  • the ID / IG of a material can be tested using a Raman spectrometer, where ID represents the D peak intensity of the material's Raman spectrum at 1350 ⁇ 50cm -1 , and IG represents the G peak intensity of the material's Raman spectrum at 1580 ⁇ 50cm -1 .
  • the test conditions are: an excitation wavelength of 532nm, a grating of 600 lines, an objective lens of 50 times, an integration time of 10s, a cumulative number of times of 3, and a surface scan to obtain the D peak and G peak intensities of 100 points, calculate the ID / IG of the 100 points, remove the maximum and minimum 30 ID / IGs , and the average value of the remaining 40 points is the ID / IG of the material.
  • the test instrument can be a Horiba LabRAM HR800 Raman spectrometer.
  • the X-ray diffraction analysis test of the material can use a copper target as an anode target and CuK ⁇ rays as a radiation source with a ray wavelength of
  • the scanning 2 ⁇ angle range was 20°-80°, and the scanning rate was 4°/min.
  • the HR-TEM of a material can be tested by methods known in the art.
  • a focused ion beam FIB is used to slice the powder, the slice thickness is ⁇ 100 nm, and the test is performed under a transmission electron microscope.
  • the true density of a material is a well-known meaning in the art and can be tested using methods known in the art.
  • an exemplary test method is as follows: Place a clean and dry sample cup on a balance, reset it to zero, add a powder sample to the sample cup, about 1/2 of the volume of the sample cup, and record the sample mass. Place the sample cup with the sample in the true density tester, close the test system, and introduce helium according to the program.
  • whether there is a coating layer on the surface of a material can be determined by high-resolution transmission electron microscopy (HR-TEM).
  • HR-TEM high-resolution transmission electron microscopy
  • gram capacity has a meaning known in the art and can be tested by methods known in the art.
  • An exemplary test method is as follows: the sample powder is mixed with the conductive agent carbon black (Super P), the binder polyvinylidene fluoride (PVDF) in a mass ratio of 91.6:1.8:6.6 and the solvent N-methylpyrrolidone (NMP) to form a slurry; the prepared slurry is applied on the surface of the negative electrode current collector copper foil, and dried in an oven for use; ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent, and then LiPF 6 was dissolved in the above organic solvent to prepare an electrolyte with a concentration of 1 mol/L; then, a metal lithium sheet was used as a counter electrode and a polyethylene (PE) film was used as an isolation membrane, and the above electrolyte was assembled into a CR24
  • the specific surface area of a material has a well-known meaning in the art and can be measured using instruments and methods known in the art. For example, it can be tested with reference to GB/T 19587-2017 using a nitrogen adsorption specific surface area analysis test method and calculated using the BET (Brunauer Emmett Teller) method.
  • the test instrument can be a Tri-Star 3020 specific surface area pore size analysis tester from Micromeritics, USA.
  • the volume distribution particle sizes Dv10, Dv50, and Dv90 of materials are well-known in the art, and respectively represent the particle sizes corresponding to the cumulative volume distribution percentages of the materials reaching 10%, 50%, and 90%, and can be measured using instruments and methods known in the art. For example, it can be measured with a laser particle size analyzer with reference to GB/T 19077-2016.
  • the test instrument can be a Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.
  • the powder compaction density of a material is a well-known meaning in the art and can be measured using instruments and methods known in the art.
  • a material e.g., a first carbon-based material, a second carbon-based material, etc.
  • an electronic pressure testing machine e.g., a UTM7305 electronic pressure testing machine
  • An exemplary test method is as follows: weigh 1 g of sample powder, add it to a mold with a bottom area of 1.327 cm2 , pressurize it to 2000 kg, maintain the pressure for 30 seconds, then release the pressure, maintain for 10 seconds, and then record and calculate the powder compaction density of the material under a pressure of 20000N.
  • the tap density of a material has a well-known meaning in the art and can be measured using instruments and methods known in the art.
  • a material e.g., a first carbon-based material, a second carbon-based material, etc.
  • 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 ⁇ 0.2mm, vibration number 5000 times, and measuring cylinder 25mL.
  • the degree of graphitization of a material is a well-known meaning in the art and can be tested using instruments and methods known in the art.
  • an X-ray diffractometer e.g., Bruker D8 Discover
  • d 002 is the average interlayer spacing of the C(002) crystal plane in the crystal structure of the material expressed in nanometers (nm).
  • primary particles have a meaning known in the art.
  • Primary particles refer to non-agglomerated particles.
  • Agglomerated particles formed by two or more primary particles are secondary particles.
  • Primary particles can be distinguished by using a scanning electron microscope (SEM) image.
  • the number ratio of primary particles in the first carbon-based material and/or the second carbon-based material refers to: randomly selecting a test sample in the negative electrode film layer, randomly selecting multiple test areas in the test sample, using a scanning electron microscope to obtain images of the multiple test areas, and counting the number of first carbon-based materials with primary particle morphology in each image as a ratio of the total number of first carbon-based material particles, and the average value of multiple statistical results is the number ratio of primary particles in the first carbon-based material.
  • the compaction density of the negative electrode film layer is a well-known meaning in the art and can be tested by methods known in the art.
  • the compaction density of the negative electrode film layer the surface density of the negative electrode film layer / the thickness of the negative electrode film layer.
  • the thickness of the negative electrode film layer is a well-known meaning in the art and can be tested by methods known in the art, such as using a micrometer (e.g., Mitutoyo 293-100, with an accuracy of 0.1 ⁇ m).
  • Discharge the secondary battery for safety reasons, the secondary battery is generally fully discharged; disassemble the secondary battery and take out the negative electrode sheet, and soak the negative electrode sheet in dimethyl carbonate for a certain period of time (e.g., 2h-10h); then take out the negative electrode sheet and dry it at a certain temperature and time (e.g., 60°C, more than 4h), and take out the negative electrode sheet after drying.
  • a certain period of time e.g., 2h-10h
  • a certain temperature and time e.g., 60°C, more than 4h
  • the dried negative electrode sheet is baked at a certain temperature and time (for example, 400°C for more than 2h), and a region of the baked negative electrode sheet is selected to sample the negative electrode active material (a blade can be used to scrape the powder for sampling); the collected negative electrode active material is sieved (for example, sieved with a 200-mesh sieve), and finally a sample that can be used to test the parameters of the above-mentioned negative electrode active materials is obtained.
  • the first carbon-based material and the second carbon-based material can be distinguished by SEM.
  • FIG2 is a SEM image of an embodiment of the negative electrode sheet of the present disclosure, from which it can be seen that the first carbon-based material has a particle cross-section with obvious pores, and the second carbon-based material has a particle cross-section without pores.
  • the second carbon-based material mentioned above can be obtained through commercial purchase or prepared according to methods known in the art.
  • the first carbon-based material mentioned above can be prepared by the following method.
  • the preparation method of the first carbon-based material includes: step 1, providing a raw material having a plurality of pore structures; step 2, uniformly mixing the raw material and the filling material in a predetermined ratio, then keeping the mixture at a first temperature T 1 for a first time t 1 , and cooling to room temperature to obtain an intermediate; step 3, keeping the obtained intermediate at a second temperature T 2 for a second time t 2 , and obtaining the first carbon-based material.
  • the raw material used to prepare the first carbon-based material includes natural graphite.
  • Natural graphite generally refers to graphite formed naturally in nature, which does not need to be graphitized, and there are usually more closed-pore structures inside the natural graphite particles.
  • the natural graphite includes one or more of flake graphite, natural spherical graphite and microcrystalline graphite, and more optionally includes natural spherical graphite.
  • Natural spherical graphite refers to natural graphite with a spherical or quasi-spherical shape, and not all natural graphite particles are controlled to be ideal spheres.
  • natural spherical graphite with a desired particle size and morphology can be obtained by pre-treating flake graphite, and optionally, the pre-treatment includes crushing, classification, spheroidization, purification and other processes.
  • the volume distribution particle size Dv50 of the raw material may be 6.0 ⁇ m-25.0 ⁇ m.
  • the specific surface area of the raw material may be greater than or equal to 2.5 m 2 /g, and may be 2.5 m 2 /g-10.0 m 2 /g.
  • the specific surface area of the raw material is within the above range, it is beneficial to carry out subsequent filling treatment and obtain the first carbon-based material with the required specific surface area, and it is also beneficial for the first carbon-based material to have both high capacity and high first coulombic efficiency. In addition, it is also beneficial for the first carbon-based material to have better kinetic properties.
  • the softening point temperature of the filling material is 90°C-150°C.
  • the softening point temperature of the filling material is 94°C-146°C, 94°C-142°C, 94°C-138°C, 94°C-134°C, 94°C-130°C, 104°C-146°C, 104°C-142°C, 104°C-138°C, 104°C-134°C, 104°C-130°C.
  • the volume distribution particle size Dv50 of the filler material is less than or equal to 6 ⁇ m, and can be 1 ⁇ m-6 ⁇ m, 1 ⁇ m-5 ⁇ m, 2 ⁇ m-5 ⁇ m, 3 ⁇ m-5 ⁇ m. This is conducive to the filler material being melted by heat and filling into the pore structure of the raw material, and is also conducive to improving the dispersion uniformity of the filler material and the raw material.
  • the coking value of the above-mentioned filling material is 15%-40%, and can be optionally 18%-34%.
  • the coking value of the filling material has a meaning known in the art and can be measured using instruments and methods known in the art. For example, it can be measured with reference to GB/T 8727-2008.
  • the filling material includes one or more of coal tar, petroleum asphalt, polymer compounds and resins, and may optionally include one or more of coal tar and petroleum asphalt.
  • the mass ratio of the filler material to the raw material is (10-40):100, and may be (10-30):100, (10-25):100, (10-20):100, (12-30):100, (14-28):100, (15-25):100.
  • the mass ratio within the above-mentioned range as required to obtain the desired ID / IG value.
  • step 2 by adjusting one or more parameters such as the type, softening point, coking value, and addition amount of the filling material within the above-mentioned range, it is helpful to adjust the number and/or pore size of pores in the outer and inner regions of the first carbon-based material within a suitable range, which is helpful to adjust the S2/S1 of the first carbon-based material within a suitable range.
  • the viscosity of the filling material is not high after it is heated and melted, and it maintains good fluidity. At the same time, it is not easy to adhere to the raw material particles, which can reduce the agglomeration of the raw material particles in the subsequent preparation process. This can also reduce the problems of increased surface defects of the first carbon-based material particles and increased surface active sites due to the need to add a depolymerization step.
  • step 2 the heating process of uniformly mixing the raw material and the filling material in a predetermined ratio and then heating the temperature to the first temperature T1 may be a staged heating process.
  • the phased temperature increasing process includes a first temperature increasing process, a second temperature increasing process, and a third temperature increasing process.
  • the first temperature rising process is to raise the temperature to 200° C.-250° C. and keep the temperature at this temperature for 0.5 h-3 h.
  • the second temperature rising process is to rise the temperature to 450-550°C and keep the temperature at this temperature for 0-2 hours.
  • the holding time is 0 hours, it means that when the temperature rises to the range of 450-550°C, no holding treatment is performed, but the temperature continues to rise to the first temperature T 1 .
  • the third temperature increasing process is to increase the temperature to the first temperature T 1 and keep the temperature at the first time t 1 .
  • the temperature is first raised to 200°C-250°C. Since the heating temperature is higher than the softening point of the filling material, the filling material is melted and softened by the heat. Keeping it warm for 0.5h-3h allows it to flow and fill into the pore structure of the raw material; then the temperature is raised to 450°C-550°C. At this time, the melted and softened filling material undergoes a carbonization reaction, gradually forming a semi-coke state and turning into a viscous liquid or solid, thereby preventing the filling material from entering the entire pore structure of the raw material; finally, the temperature is raised to the first temperature. At this time, the filling material undergoes a carbonization reaction, thereby enabling the pore structure occupied by the filling material to be effectively filled.
  • the temperature is raised to the first temperature T 1 at a rate of 1°C/min-10°C/min.
  • the heating rate may be 1°C/min, 2°C/min, 3°C/min, 4°C/min, 5°C/min, 6°C/min, 7°C/min, 8°C/min, 9°C/min, 10°C/min or any range thereof.
  • the heating rate is 1.5°C/min-8°C/min, 1.5°C/min-6°C/min, 2°C/min-6°C/min, 2°C/min-5°C/min.
  • the heating rate of the first heating process may be 1°C/min-10°C/min, and may be 1.5°C/min-8°C/min, 1.5°C/min-6°C/min, 2°C/min-6°C/min, or 2°C/min-5°C/min.
  • the heating rate of the second heating process may be 1°C/min-10°C/min, and may be 2°C/min-8°C/min.
  • the heating rate of the third heating process may be 1°C/min-10°C/min, and may be 2°C/min-8°C/min.
  • the first temperature T1 is 700°C-1200°C.
  • the first temperature T1 can be 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1200°C or any range thereof.
  • the first temperature T1 is 750°C-1100°C, 800°C-1100°C, 850°C-1100°C, 900°C-1100°C, 850°C-1000°C.
  • the first time t1 is 1 hour to 5 hours.
  • the first time t1 can be 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours or any range thereof.
  • the first time t1 is 2 hours to 4 hours.
  • the heat treatment in step 2, can be carried out in a medium frequency furnace, a roller kiln, a rotary kiln, a push plate kiln, a vertical granulation kettle, a horizontal granulation kettle, a vertical reactor, a horizontal reactor or a drum furnace, etc., which can perform programmed temperature increase.
  • the heat treatment atmosphere may be a protective gas atmosphere.
  • the protective gas may include one or more of nitrogen, argon, and helium.
  • step 2 by adjusting one or more of the heating rate, the first temperature, the first time, the heating process, etc. within the above-mentioned range, it is helpful to adjust the number of pores and/or the pore size in the outer region and the inner region of the first carbon-based material within a suitable range, and then it is helpful to adjust the S2/S1 of the first carbon-based material within a suitable range.
  • the second temperature T2 is 2070°C-2700°C.
  • the second temperature T2 is 2070°C-2570°C, 2070°C-2510°C, 2070°C-2450°C, 2070°C-2360°C, 2140°C-2570°C, 2140°C-2510°C, 2140°C-2450°C, 2140°C-2360°C.
  • the second time t2 is 1.5h-6h.
  • the second time t1 can be 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h or any range thereof.
  • the second time t2 is 2h-5h.
  • the heat treatment may be performed in a medium frequency furnace, a box-type graphitization furnace, an Acheson graphitization furnace, a continuous graphitization furnace, or an inner-string graphitization furnace.
  • the medium frequency furnace and the continuous graphitization heat treatment atmosphere may be a protective gas atmosphere.
  • the protective gas may include one or more of argon and helium.
  • step 3 by adjusting one or more of the second temperature and the second time within the above range, it is beneficial to adjust the content of disordered carbon in the first carbon-based material within a suitable range, which is beneficial for the first carbon-based material to have a suitable degree of graphitization, interlayer spacing and ID / IG , etc.
  • the higher the second temperature the smaller the ID / IG of the first carbon material.
  • Those skilled in the art can make adjustments within the above-given temperature range as needed to obtain the desired ID / IG value.
  • the parameters of natural graphite such as S2/S1, graphitization degree, gram capacity, particle size, powder compaction density, tap density, and adsorption amount of linseed oil.
  • the first carbon-based material obtained above is mixed with an organic carbon source and then carbonized to obtain a particle size of at least A small portion of the surface forms a carbon coating layer.
  • the organic carbon source may be a carbon-containing material known in the art suitable for coating, for example, may include one or more of coal tar, petroleum tar, phenolic resin, coconut shell, etc.
  • the carbonization temperature is 900°C-1300°C.
  • the second carbon-based material is purchased through commercial channels.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector.
  • the positive electrode 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, an optional binder and an optional conductive agent.
  • the positive electrode film layer is generally formed by coating the positive electrode slurry on the positive electrode current collector, drying and cold pressing.
  • the positive electrode slurry is generally formed by dispersing the positive electrode active material, the optional conductive agent, the optional binder and any other components in a solvent and stirring evenly.
  • the solvent may be N-methylpyrrolidone (NMP), but is not limited thereto.
  • the binder for the positive electrode film layer may include 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
  • tetrafluoroethylene-hexafluoropropylene copolymer tetraflu
  • 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 above-mentioned 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 above-mentioned lithium transition metal oxides 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 phosphates 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 obtained by doping and/or surface coating the positive electrode active material.
  • the electrolyte is an electrolyte solution
  • the electrolyte solution includes an electrolyte salt and a solvent.
  • the types of the above electrolyte salts are not particularly limited and can be selected according to actual needs.
  • the above-mentioned 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
  • the above-mentioned solvents 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
  • glycine GBL
  • sulfolane SF
  • the electrolyte may further include 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 above-mentioned 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 made 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 package 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 above soft package can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT) and polybutylene succinate (PBS).
  • FIG3 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 are enclosed to form a receiving cavity.
  • the shell 51 has an opening connected to the receiving cavity, and the cover plate 53 is used to cover the above opening to close the above 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 above 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.
  • FIG5 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 are 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.
  • FIG6 and FIG7 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, wherein the upper box body 2 is used to cover the lower box body 3 and form a closed space for accommodating the battery modules 4.
  • the plurality of battery modules 4 may be arranged in the battery box in any manner.
  • the present disclosure also provides an electrical 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 electrical device, and can also be used as an energy storage unit for the electrical device.
  • the electrical 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 above-mentioned electrical devices can select secondary batteries, battery modules or battery packs according to their usage requirements.
  • Fig. 8 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.
  • Step 1 mechanically crush, classify, spheroidize and purify the flake graphite to obtain natural spherical graphite.
  • Step 2 mix the obtained natural spherical graphite with the filler petroleum asphalt in a ratio of 100:25, the softening point of the petroleum asphalt is 120°C and the coking value is 36%, and then place the mixed material in a programmable temperature rising device, heat it to 200°C and keep it for 1h (the first heating process), and then continue to heat it to 700°C and keep it for 2h (the third heating process), and then cool it to room temperature to obtain an intermediate.
  • Step 3 place the obtained intermediate in a graphitization furnace, perform a heat treatment at 2580°C, and then demagnetize and screen it to obtain a first carbon-based material.
  • the ID / IG value of the obtained first carbon-based material is 0.152, S2/S1 is 14.7, and DV50 is 18.3 ⁇ m.
  • the S2/S1 of the first carbon-based material is obtained by testing using the following method.
  • the sample preparation binder and the first carbon-based material powder are mixed evenly and then applied to the copper foil, dried at 60°C for 30 minutes for use; 5 samples to be tested are cut into 6mm ⁇ 6mm sizes at 5 different positions and pasted on the sample stage of the CP type argon ion cross-section polisher respectively; the samples are cut using a plasma beam to obtain the cross section of each sample.
  • the test instrument can be the IB-09010CP type argon ion cross-section polisher of Japan JEOL Company.
  • the cross sections of each sample of the first carbon-based material are scanned using a scanning electron microscope, and a scanned image is obtained by arbitrarily selecting an area in each cross section of the sample.
  • the test may refer to JY/T010-1996.
  • the test instrument may be a Sigma 300 scanning electron microscope from the German ZEISS company.
  • the area formed by extending 0.25 ⁇ m from the particle surface of the first carbon-based material to the inside of the particle is recorded as the external area, and the area inside the external area is recorded as the internal area.
  • Use image processing software to obtain the total pore area S1' of the external area of each particle cross section and the pore area S2' of the internal area of the first carbon-based material, and calculate the value of S2'/S1'; and calculate the arithmetic mean of S2'/S1' of all 20 particles as the value of S2/S1 of the first carbon-based material.
  • the image processing software can be AVIZO.
  • the preparation methods of materials 1-2 to 1-5 are similar to the preparation method of the above-mentioned material 1-1, except that the mixing ratio of natural spherical graphite and filler petroleum asphalt and the heat treatment temperature are adjusted so that the ID / IG value of the first carbon-based material is the value shown in Table 1.
  • the preparation methods of materials 1-6 to 1-10 are similar to the preparation method of the above-mentioned material 1-1, except that the softening point temperature, coking value, and mixing ratio of natural spherical graphite and filler petroleum asphalt of the filler material are adjusted as shown in Table 2, and the third heating process is adjusted so that the S2/S1 of the first carbon-based material is the value shown in Table 2.
  • the preparation method of material 1-11 is similar to the preparation method of the above-mentioned material 1-3, except that the particle size distribution Dv50 of the flake graphite after mechanical crushing, classification and spheroidization is adjusted to 10.2 ⁇ m.
  • coconut shell is used as raw material, heat treated at 600°C, crushed, alkaline impurity removed, and heat treated at 1000°C to obtain an amorphous carbon material. Then, the amorphous carbon is coated and heat treated, and the amorphous carbon and the coating agent are mixed in a mass ratio of 100:10 and heat treated at a temperature of 2450°C, wherein the coating agent is asphalt. After demagnetization and screening, a second carbon-based material is obtained. The ID / IG value of the obtained second carbon-based material is 0.17 and the Dv50 is 10.2 ⁇ m.
  • the preparation method is similar to the above-mentioned material 2-1, except that: the amount of the coating agent and the heat treatment temperature are adjusted as shown in Table 3 to obtain a second carbon-based material having the ID / IG shown in Table 3.
  • the preparation method is similar to the above-mentioned material 2-1, except that the particle size distribution Dv50 after crushing is adjusted to 14.5 ⁇ m.
  • Negative electrode sheet The negative electrode active material (a mixture of the above-mentioned material 1-1 (first carbon-based material) and material 2-1 (second carbon-based material) in a mass ratio of 70:30), conductive agent carbon black (Super P), thickener sodium carboxymethyl cellulose, and binder styrene-butadiene rubber in a weight ratio of 96.4:1:1.2:1.4 are fully stirred and mixed in an appropriate amount of solvent deionized water to form a negative electrode slurry.
  • the negative electrode slurry is coated on both surfaces of the negative electrode current collector copper foil, and after drying and cold pressing, a negative electrode sheet is obtained.
  • Positive electrode sheet LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523) was mixed with conductive agent carbon black (Super P) and binder polyvinylidene fluoride in a weight ratio of 96:2:2, and an appropriate amount of solvent NMP was added and stirred evenly to obtain a positive electrode slurry.
  • the positive electrode slurry was coated on both surfaces of the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet was obtained.
  • Electrolyte Ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent, and then LiPF6 is dissolved in the above organic solvent to prepare an electrolyte with a concentration of 1 mol/L.
  • Diaphragm Polypropylene film is used.
  • Preparation of secondary battery Place the positive electrode sheet and negative electrode sheet prepared above in order, so that the separator is between the positive electrode sheet and the negative electrode sheet to play an isolating role, and then wind to obtain an electrode assembly; place the electrode assembly in an outer package, dry it, and inject the electrolyte. The liquid is then vacuum packaged, left to stand, formed, and shaped to obtain a secondary battery.
  • Example 2-8 The battery preparation methods of Examples 2-8 are similar to those of Example 1, except that the first carbon-based material or the second carbon-based material selects materials with different ID / IG , as shown in Table 4 for details.
  • a secondary battery was assembled similarly to the preparation method of Example 1, except that the negative electrode active material only contained the second carbon-based material 2-1 used in Example 1.
  • the secondary battery is assembled similarly to the preparation method of Example 1, except that the negative electrode active material only contains the first carbon-based material 1-3.
  • the secondary battery was charged to 4.3V at 1/3C constant current, then charged to 0.05C at 4.3V constant voltage, left to stand for 5 minutes, and then discharged to 2.8V at 1/3C constant current, and the battery discharge energy was recorded.
  • the battery discharge energy divided by the battery weight is the battery weight energy density, in Wh/kg.
  • the measurement data is shown in Table 4.
  • the secondary battery was charged to 4.3V at a constant current of 0.33C, then charged to a current of 0.05C at a constant voltage, and after standing for 5 minutes, the secondary battery was discharged to 2.8V at a constant current of 0.33C, and its actual capacity was recorded as C0.
  • the secondary battery is charged with constant current at 1.0C0, 1.3C0, 1.5C0, 1.8C0, 2.0C0, 2.3C0, 2.5C0, 3.0C0 in turn to 4.3V or 0V negative electrode cut-off potential (whichever is reached first). After each charging is completed, it needs to be discharged to 2.8V at 1C0.
  • the negative electrode potential corresponding to charging to 10%, 20%, 30%, ..., 80% SOC (State of Charge) at different charging rates is recorded, and the charging rate-negative electrode potential curve under different SOC states is drawn. After linear fitting, the charging rate corresponding to the negative electrode potential of 0V under different SOC states is obtained.
  • the charging rate is the charging window under the SOC state, which is recorded as C10% SOC, C20% SOC, C30% SOC, C40% SOC, C50% SOC, C60% SOC, C70% SOC, and C80% SOC respectively.
  • the charging time T of the secondary battery from 10% SOC to 80% SOC is calculated according to the formula (60/C20% SOC+60/C30% SOC+60/C40% SOC+60/C50% SOC+60/C60% SOC+60/C70% SOC+60/C80% SOC) ⁇ 10% (assuming that the secondary battery does not deposit lithium), and the unit is min.
  • the prepared secondary battery was charged at 1C constant current to an upper cut-off voltage of 4.3V (corresponding to 100% SOC), then charged at a constant voltage to a current of 0.05C, and after standing for 5 minutes, the secondary battery was discharged at 1C constant current to a lower cut-off voltage of 2.8V (corresponding to 0% SOC), and the discharge capacity at this time was recorded, which was the discharge capacity of the first cycle.
  • the secondary battery was subjected to a cyclic charge and discharge test according to the above method, and the discharge capacity after each cycle was recorded.
  • Capacity retention rate (%) of secondary battery after 1000 cycles at 45° C. discharge capacity after 1000 cycles/discharge capacity at the first cycle ⁇ 100%.
  • the negative electrode active material in the negative electrode film layer include the first carbon-based material and the second carbon-based material disclosed at the same time, it is possible to have high energy density while taking into account excellent cycle performance and kinetic performance.
  • the ID / IG of the first carbon-based material in the range of 0.155-0.220, a secondary battery with better balance of energy density, cycle performance and kinetic performance can be obtained.
  • Example 9-13 The battery preparation methods of Examples 9-13 are similar to those of Example 1, except that the first carbon-based material selected is different materials S2/S1, and materials 1-6 to 1-10 are selected respectively, as shown in Table 5 for details.
  • Example 14 The battery preparation method of Example 14 is similar to that of Example 1, except that the first carbon-based material and the second carbon-based material are made of materials with different DV50 values, as shown in Table 6 for details.
  • the present disclosure is not limited to the above-mentioned embodiments.
  • the above-mentioned embodiments are merely examples, and embodiments having substantially the same structure as the technical idea and exerting the same effects within the scope of the technical solution of the present disclosure are all included in the technical scope of the present disclosure.
  • various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present disclosure.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Power Engineering (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Battery Electrode And Active Subsutance (AREA)
  • Secondary Cells (AREA)

Abstract

提供一种二次电池以及用电装置，该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位于所述负极集流体至少一个表面上且包括负极活性材料的负极膜层，其中，所述负极活性材料包括第一碳基材料和第二碳基材料，所述第一碳基材料具有孔结构，所述第一碳基材料的I D/I G小于等于0.280，I D表示拉曼光谱中在1350±50cm -1处的D峰强度，I G表示拉曼光谱中在1580±50cm -1处的G峰强度，所述第二碳基材料为无定形碳材料。

Description

二次电池以及用电装置
相关申请的交叉引用
本公开基于申请号为202311641312.6、申请日为2023年11月30日、发明名称为“二次电池以及用电装置”的中国专利申请提出，并要求该中国专利申请的优先权，该中国专利申请的全部内容在此引入本公开作为参考。
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以及用电装置。
背景技术
近年来，二次电池广泛应用于水力、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、航空航天等多个领域。随着二次电池的应用范围越来越广泛，人们对其性能也提出了更高的要求。
因此，如何使二次电池在具有高能量密度的同时，具有优异的循环性能以及动力学性能，成为本领域亟待解决的问题。
发明内容
本公开是鉴于上述课题而进行的，其目的在于，提供一种二次电池以及用电装置，该二次电池在具有高能量密度的同时，兼顾优异的循环性能和动力学性能。
本公开第一方面提供一种二次电池，包括负极极片，所述负极极片包括负极集流体以及位于所述负极集流体至少一个表面上且包括负极活性材料的负极膜层，其中，所述负极活性材料包括第一碳基材料和第二碳基材料，所述第一碳基材料具有孔结构，所述第一碳基材料的ID/IG小于等于0.280，其中，ID表示拉曼光谱中在1350±50cm-1处的D峰强度，IG表示拉曼光谱中在1580±50cm-1处的G峰强度，所述第二碳基材料为无定形碳材料。
通过使负极膜层中的负极活性材料同时包括第一碳基材料和第二碳基材料，所述第一碳基材料具有孔结构，所述第一碳基材料的ID/IG小于等于0.280，所述第二碳基材料为无定形碳材料，由此，能够使负极极片具有高压实密度、低体积变化性能和高活性离子传输速度，从而使采用该负极极片的二次电池能在具有高能量密度的同时，兼顾优异的循环性能以及动力学性能。
在一些实施方式中，所述第一碳基材料的ID/IG为0.155-0.220；由此，更有利于电池兼顾优异的能量密度、循环性能和动力学性能。
在一些实施方式中，所述第二碳基材料的ID/IG小于等于0.250，可选地，所述第二碳基材料的ID/IG小于等于0.230。由此，更有利于电池兼顾优异的循环性能和更高的能量密度。
在一些实施方式中，所述第一碳基材料的Dv50大于所述第二碳基材料的Dv50。由此，更有利于电池的能量密度和动力学性能的提高。
在一些实施方式中，所述第一碳基材料的X射线粉末衍射图谱在2θ衍射角为26.5°±0.2°、44.5°±0.2°、54.6°±0.2°处具有衍射峰，所述第二碳基材料的X射线粉末衍射图谱中不存在明显衍射峰。由此，通过使第一碳基材料中含有石墨而第二碳基材料为无定形碳，能够使二次电池在具有高能量密度的同时，兼顾优异的循环性能以及动力学性能。
在一些实施方式中，所述第一碳基材料在HR-TEM中有晶格条纹，所述第二碳基材料在HR-TEM中无晶格条纹。由此，通过使第一碳基材料中含有石墨而第二碳基材料为无定形碳，能够使二次电池在具有高能量密度的同时，兼顾优异的循环性能以及动力学性能。
在一些实施方式中，所述第一碳基材料在20000N压力下的粉体压实密度大于所述第二碳基材料在20000N压力下的粉体压实密度。由此，有利于使二次电池兼顾高能量密度和良好的动力学性 能。
在一些实施方式中，所述第一碳基材料的真实密度大于所述第二碳基材料的真实密度。第一碳基材料的真实密度较大，有利于提升负极膜层的压实密度，提升二次电池的能量密度。第二碳基材料的真实密度较小，提升活性离子的脱嵌，进而提升二次电池的动力学性能。因此，通过调节第一碳基材料的真实密度大于所述第二碳基材料的真实密度，有利于使二次电池兼顾高能量密度和良好的动力学性能。
在一些实施方式中，所述第一碳基材料的真实密度为2.22g/cm3-2.27g/cm3，可选为2.23g/cm3-2.26g/cm3。通过使第一碳基材料的真实密度在上述范围内且大于第二碳基材料，有利于提升二次电池的能量密度。
在一些实施方式中，所述第一碳基材料包括一个以上面积大于等于0.15μm2的孔结构，可选地包括一个以上面积为0.15μm2-2.0μm2的孔结构。通过使第一碳基材料和/或第二碳基材料包括上述孔面积的孔结构，所述孔结构可以为第一碳基材料和/或第二碳基材料颗粒体积变化预留足够且稳定的膨胀空间，降低第一碳基材料和/或第二碳基材料颗粒破碎风险，减少副反应的发生，改善二次电池的循环性能。
在一些实施方式中，所述第一碳基材料包括外部区域以及位于所述外部区域内侧的内部区域，所述外部区域是指从所述第一碳基材料的颗粒表面向颗粒内部延伸2.5μm的距离所构成的区域，在所述第一碳基材料的截面图中，所述外部区域的总孔面积记为S1，所述内部区域的总孔面积记为S2，并且S2>S1，可选地，2.6≤S2/S1≤450.7。第一碳基材料外部区域的孔面积S1小于内部区域的孔面积S2，说明该碳基材料外部区域的结构比内部区域更致密，由此，能够使二次电池更好地兼顾高能量密度以及良好的循环性能。
在一些实施方式中，所述第一碳基材料的外部区域中的所述孔结构的面积为小于等于0.15μm2，可选为小于等于0.13μm2，和/或，所述第一碳基材料的内部区域中包括一个以上面积大于等于0.15μm2的孔结构，可选地包括一个以上面积为0.15μm2-2.0μm2的孔结构。通过控制第一碳基材料的外部区域中的孔结构的面积在上述范围内，可以使第一碳基材料的外部区域具有密实结构，由此能够有效提升第一碳基材料的结构稳定性，尽可能避免电解液渗入到第一碳基材料颗粒内部的孔结构中，进而有效提升二次电池的循环性能。通过使第一碳基材料的内部区域包括上述大小的孔结构，一方面可以为第一碳基材料颗粒体积变化预留足够且稳定的膨胀空间，降低第一碳基材料颗粒破碎风险，减少副反应的发生，另一方面还可以提升负极膜层的压实密度，缓冲负极膜层的体积变化。
在一些实施方式中，所述第一碳基材料在20000N压力下的粉体压实密度为1.65g/cm3-2.0g/cm3，可选为1.68g/cm3-1.98g/cm3，由此，有利于提高二次电池的能量密度。
在一些实施方式中，所述第一碳基材料的体积分布粒径Dv50为8.0μm-25.0μm，可选为10.0μm-22.0μm。在一些实施方式中，所述第一碳基材料的体积分布粒径Dv90为16.0μm-45.0μm，可选为16.5μm-42.0μm。
通过使第一碳基材料的体积分布粒径Dv50和/或Dv90在上述范围内，有利于提升活性离子和电子的传输性能，从而能够进一步提升二次电池的动力学性能，另外还可以减少副反应的发生，提升二次电池的循环性能。
在一些实施方式中，所述第一碳基材料的粒度分布(Dv90-Dv10)/Dv50小于等于1.55，可选为0.90-1.50。通过使第一碳基材料的粒度分布(Dv90-Dv10)/Dv50在上述范围内，其颗粒堆积性能较好，有利于提升负极膜层的压实密度，从而能够进一步提升二次电池的能量密度；另外，还有利于调节负极膜层的孔隙分布，提升活性离子和电子传输性能，提升负极膜层对电解液的浸润和保持特性，从而提升二次电池的动力学性能和循环性能。
在一些实施方式中，所述第一碳基材料的振实密度为0.85g/cm3-1.30g/cm3，可选为0.90g/cm3-1.25g/cm3。通过使第一碳基材料的振实密度在上述范围内，有利于改善加工性能；还有利于负极膜层的颗粒之间形成合理的孔道结构，提升活性离子和电子传输性能，提升负极膜层对电解液的浸润和保持特性，进而提升二次电池的动力学性能和循环性能。
在一些实施方式中，所述第一碳基材料的石墨化度大于等于95.5％，可选为95.5％-98.0％。通过使第一碳基材料的石墨化度在上述范围内，能够使二次电池具有高能量密度。
在一些实施方式中，所述第一碳基材料和/或所述第二碳基材料包括一次颗粒。可选地，所述第一碳基材料中的所述一次颗粒的数量占比大于等于80％，所述第二碳基材料中的所述一次颗粒的数量占比大于等于80％。通过使第一碳基材料和/或第二碳基材料包含适当比例的一次颗粒，能使其具有较高的结构稳定性，还能减少副反应的发生，从而提升二次电池的循环性能。
在一些实施方式中，所述第二碳基材料的真实密度为1.95g/cm3-2.22g/cm3，可选为1.97g/cm3-2.21g/cm3。通过使第二碳基材料的真实密度在上述范围内且小于第一碳基材料，有利于提升二次电池的动力学性能。
在一些实施方式中，所述第二碳基材料的比表面积大于等于1.5m2/g，可选为1.9m2/g-7.5m2/g。通过使第二碳基材料的比表面积在上述范围内，有利于活性离子的快速脱嵌，从而能够进一步提升二次电池的动力学性能。
在一些实施方式中，所述第二碳基材料的Dv50为4.0μm-15.0μm，可选为5.0μm-15.0μm。通过使第二碳基材料的体积分布粒径Dv50在上述范围内，减少副反应的发生，提升二次电池的循环性能，另外，还有利于提升活性离子和电子的传输性能，从而能够进一步提升二次电池的动力学性能。
在一些实施方式中，所述第二碳基材料的粒度分布(Dv90-Dv10)/Dv50小于等于1.75，可选为1.1-1.75。第二碳基材料的粒度分布(Dv90-Dv10)/Dv50在上述范围内时，其颗粒堆积性能较好，有利于提升负极膜层的压实密度，提升二次电池的能量密度；另外，还有利于负极膜层的颗粒之间形成合理的孔道结构，提高负极膜层中活性离子和电子传输性能，进而提升二次电池的动力学性能。
在一些实施方式中，所述第二碳基材料在20000N压力下的粉体压实密度为0.85g/cm3-1.35g/cm3，可选为0.90g/cm3-1.30g/cm3。第二碳基材料的粉体压实密度低于第一碳基材料的粉体压实密度，通过使第二碳基材料的粉体压实密度在上述范围内，有利于提升负极膜层中活性离子传输性能，进而提升二次电池的动力学性能。
在一些实施方式中，所述第二碳基材料的振实密度为0.80g/cm3-1.20g/cm3，可选为0.83g/cm3-1.15g/cm3。通过使第二碳基材料的振实密度在上述范围内，有利于负极膜层中具有合适的孔隙分布，提升活性离子传输性能，提升负极膜层对电解液的浸润特性，进而提升二次电池的动力学性能和循环性能。
在一些实施方式中，所述第二碳基材料的克容量为330mAh/g-480mAh/g，可选为340mAh/g-470mAh/g。通过使第二碳基材料的克容量在上述范围内，能够提升二次电池的能量密度。
在一些实施方式中，所述第一碳基材料和/或所述第二碳基材料的至少部分表面具有碳包覆层。可选地，所述包覆层包括碳包覆层。由此，有利于提升活性离子嵌入负极膜层的速度，提升负极膜层的活性离子传输性能，进而提升二次电池的动力学性能。
在一些实施方式中，所述第一碳基材料在所述负极活性材料中的含量大于等于40wt％，可选地为50wt％-80wt％。通过使第一碳基材料的含量在上述范围内时，使得二次电池在具有高能量密度的同时，具有良好的加工性能、动力学性能和循环性能。
在一些实施方式中，所述负极活性材料还包括硅基材料，可选地，在所述负极活性材料中，所述硅基材料的含量为3wt％-30wt％。硅基材料具有更高的嵌锂电位，有利于提升二次电池的动力学性能；同时还能提升负极容量，从而还能进一步提升二次电池的能量密度。
在一些实施方式中，所述负极膜层的压实密度为1.40g/cm3-1.70g/cm3，可选为1.45g/cm3-1.67g/cm3。由此有利于负极膜层兼顾高容量、高活性离子和电子传输性能，进而有利于二次电池兼顾高能量密度以及良好的循环性能和动力学性能。
在一些实施方式中，所述负极膜层的面密度为5.0mg/cm2-25.0mg/cm2，可选为5.5mg/cm2-22.5mg/cm2。由此有利于负极膜层兼顾高容量、高活性离子和电子传输性能，进而有利于二次电池兼顾高能量密度以及良好的循环性能和动力学性能。
在一些实施方式中，所述负极膜层的厚度为40μm-120μm，可选45μm-100μm。
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。
发明效果
本公开的二次电池具有高能量密度，并且兼顾优异的循环性能和动力学性能。
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为本公开的第一碳基材料的颗粒的一截面图像的示意图。
图2为本公开的负极极片的一实施方式的SEM图。
图3是本公开的二次电池的一实施方式的示意图。
图4是本公开的二次电池的一实施方式的分解示意图。
图5是本公开的电池模块的一实施方式的示意图。
图6是本公开的电池包的一实施方式的示意图。
图7是图6所示的电池包的实施方式的分解示意图。
图8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，100第一碳基材料，101外部区域，102内部区域。
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。
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。
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。
目前，在提升二次电池的动力学性能、特别是快速充电性能时，大多通过降低负极膜层的面密度或降低负极膜层的压实密度的方式来提升负极的动力学性能。但是大量研究证明，以上提升负极动力学的方法仅一定程度上提升了电池充电初期的动力学性能，而且，上述方法往往带来二次电池的能量密度的明显降低。
由此，目前二次电池难以兼顾高能量密度以及良好的动力学性能和循环性能。
有鉴于此，本公开实施方式第一方面提供一种二次电池。
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]
本公开的二次电池中，负极极片包括负极集流体以及位于所述负极集流体至少一个表面上且包括负极活性材料的负极膜层，其中，所述负极活性材料包括第一碳基材料和第二碳基材料，所述第一碳基材料具有孔结构，所述第一碳基材料的ID/IG为0.152-0.280，其中，ID表示拉曼光谱在1350 ±50cm-1处的D峰强度，IG表示拉曼光谱在1580±50cm-1处的G峰强度，所述第二碳基材料为无定形碳材料。
在本公开中，“第一碳基材料具有孔结构”是指第一碳基材料具有可从截面图像(例如放大倍数为1000倍的扫描电子显微镜图像)直接观测的孔结构，即用于制备第一碳基材料的主体结构中的孔结构没有被完全填充。
对于无定形碳材料，其层间距较大，有利于活性离子的快速脱嵌，并且具有更高的对锂电位，有利于电池的动力学性能提高。但是，无定形碳材料表面活性较高，易与电解液发生副反应，首次充电时，消耗活性锂离子较多，使得二次电池活性离子减少，降低二次电池容量，使得二次电池能量密度降低。因此，无定形碳材料在电池中的应用受到限制。
本公开的负极活性材料同时包括第一碳基材料和第二碳基材料无定形碳，第一碳基材料具有孔结构，相当于在材料内部预留了一定空间，使得在极片制备过程中有效提高极片压实密度，从而提升电池的能量密度，且第一碳基材料的ID/IG在特定范围内，碳基材料表面具有较少的无序碳，使得材料具有较高的化学稳定性，能够减少副反应的发生，首次充电时，可有效降低活性离子的消耗，可以进一步提升电池能量密度和循环性能。由此，可以使得电池在具有较好动力学的前提下，同时兼顾较高的能量密度和循环性能。
在一些实施例中，上述第一碳基材料的ID/IG为0.155-0.220；由此，能够均衡性更好地获得优异的能量密度、循环性能和动力学性能。
在一些实施例中，上述第二碳基材料的ID/IG小于等于0.250，可选地，上述第二碳基材料的ID/IG小于等于-0.230。由此，电池的循环性能和能量密度可以进一步改善。在一些实施例中，上述第一碳基材料的X射线粉末衍射图谱在2θ衍射角为26.5°±0.2°、44.5°±0.2°、54.6°±0.2°处具有衍射峰。上述第二碳基材料的X射线粉末衍射图谱中没有明显的衍射峰。
上述第一碳基材料的HR-TEM图谱中有晶格条纹，代表了该碳材料具有晶体结构。
上述第二碳基材料的HR-TEM图谱中没有明显的晶格条纹，代表了该碳材料不具有晶体结构，通常该类材料被称为无定形碳。
在一些实施例中，第二碳基材料可以为软碳、或硬碳。
在一些实施例中，上述第一碳基材料在20000N压力下的粉体压实密度大于上述第二碳基材料在20000N压力下的粉体压实密度。第一碳基材料的粉体压实密度较大，有利于提升负极膜层的压实密度，提升二次电池的能量密度。第二碳基材料的粉体压实密度较小，有利于提升极片孔隙，提升活性离子的脱嵌，进而提升二次电池的动力学性能。因此，通过调节第一碳基材料的粉体压实密度大于所述第二碳基材料的粉体压实密度，有利于使二次电池兼顾高能量密度和良好的动力学性能。
在一些实施例中，第一碳基材料的真实密度大于第二碳基材料的真实密度。有利于使二次电池兼顾高能量密度和良好的动力学性能。
在一些实施例中，上述第一碳基材料的真实密度为2.22g/cm3-2.27g/cm3，可选为2.23g/cm3-2.26g/cm3。第一碳基材料的真实密度在上述范围内时，可以进一步提升二次电池的能量密度。
在一些实施方式中，所述第一碳基材料的体积分布粒径Dv50大于第二碳基材料的体积分布粒径Dv50。由此，可以进一步改善电池的能量密度，还有助于动力学性能的提高。
在一些实施例中，第一碳基材料的振实密度大于第二碳基材料的振实密度。由此，可以进一步改善电池的加工性能。
在一些实施例中，上述第一碳基材料包括一个以上面积大于等于0.15μm2的孔结构，可选地包括一个以上面积为0.15μm2-2.0μm2的孔结构。通过使第一碳基材料和/或第二碳基材料包括上述孔面积的孔结构，可以为第一碳基材料颗粒和/或第二碳基材料体积变化预留足够且稳定的膨胀空间，降低第一碳基材料和/或第二碳基材料颗粒破碎风险，减少副反应的发生，提升二次电池的循环性能，另外，还可以提升负极膜层的压实密度，提高二次电池的能量密度。
在一些实施例中，上述第一碳基材料包括外部区域以及位于上述外部区域内侧的内部区域，上述外部区域是指从上述第一碳基材料的颗粒表面向颗粒内部延伸2.5μm的距离所构成的区域，在上述第一碳基材料的截面图中，上述外部区域的总孔面积记为S1，上述内部区域的总孔面积记为S2，并且S2>S1。本公开中，“内部区域”是指在材料颗粒中除外部区域以外的区域。
当第一碳基材料满足S2>S1时，说明该碳基材料外部区域的结构比内部区域更致密，第一碳基材料进一步具有如下特征：内部区域的孔数量多和/或孔尺寸大，而外部区域的孔数量少和/或孔尺寸小。第一碳基材料内部区域的孔结构可为颗粒体积变化预留所需的膨胀空间，由此能够降低颗粒破 碎产生新界面的风险、降低负极膜层厚度反弹率，进而减少副反应的发生；第一碳基材料外部区域的孔数量少和/或孔尺寸小，由此可以使第一碳基材料颗粒具有稳定的结构，并尽可能避免电解液渗入到第一碳基材料颗粒内部的孔结构中，从而能够进一步减少副反应的发生，降低颗粒内部SEI膜成膜对活性离子的消耗。因此，当第一碳基材料满足S2>S1时，能够提升二次电池的首次库伦效率，并进一步改善二次电池的循环性能。
优选地，2.6≤S2/S1≤450.7，例如可以为3≤S2/S1≤430，4≤S2/S1≤400，5≤S2/S1≤350，6≤S2/S1≤300，7≤S2/S1≤250，8≤S2/S1≤200。发明人在进一步研究中发现，当S2/S1还满足在上述范围内时，能够使二次电池更好地兼顾高能量密度以及良好的循环性能。
在本公开中，第一碳基材料的外部区域的总孔面积S1和内部区域的总孔面积S2，可以通过第一碳基材料的截面图像进行测试得到。
图1是本公开的第一碳基材料100的颗粒的一截面图像的示意图。如图1所示，从第一碳基材料100的颗粒表面向颗粒内部延伸2.5μm的距离所构成的区域即为外部区域101，外部区域101内侧的区域即为内部区域102。
在本公开中，第一碳基材料的孔面积、S1、S2值可采用截面抛光仪(例如日本JEOL公司的IB-09010CP型氩离子截面抛光仪)获取第一碳基材料的截面；然后参考JY/T010-1996，使用扫描电子显微镜(例如德国ZEISS公司的Sigma 300型扫描电子显微镜)扫描第一碳基材料的截面；最后通过图像处理软件(例如AVIZO)分别获取第一碳基材料中的任意一个孔的孔面积；以及内部区域的总孔面积S2和外部区域的总孔面积S1，并由此获得S2/S1的值。示例性的，可以从二次电池中的负极极片的不同区域中获得样品，随机从样品上选取至少5个位置(如5个、10个、15个甚至更多)采用截面抛光仪获取截面，并从各截面的扫描电子显微镜的图像中随机选取至少10个颗粒(如10个、20个、50个甚至更多个颗粒)的截面，按上述定义用图像处理软件获取每个颗粒截面的内部区域的总孔面积S2’和外部区域的总孔面积S1’，并由此获得每个颗粒截面的S2’/S1’的值。计算所有被测颗粒截面的S2’/S1’的算数平均值，作为第一碳基材料的S2/S1值。
在一些实施例中，上述第一碳基材料的外部区域中的上述孔结构的面积为小于等于0.15μm2，可选为小于等于0.13μm2。发明人在进一步研究中还发现，通过控制第一碳基材料的外部区域中的孔结构的面积在上述范围内，可以使第一碳基材料的外部区域具有密实结构，由此能够有效提升第一碳基材料的结构稳定性，尽可能避免电解液渗入到第一碳基材料颗粒内部的孔结构中，进而有效提升二次电池的循环性能。当然，本公开并不意欲限制第一碳基材料的外部区域中的所有孔结构的面积均小于等于0.15μm2，例如，可控制95％以上，可选为99％以上的孔结构的面积小于等于0.15μm2。
在一些实施例中，上述第一碳基材料的内部区域中包括一个以上面积大于等于0.15μm2的孔结构，可选地包括一个以上面积为0.15μm2-2.0μm2的孔结构。发明人在进一步研究中还发现，通过使第一碳基材料的内部区域包括上述大小的孔结构，一方面可以为第一碳基材料颗粒体积变化预留足够且稳定的膨胀空间，降低第一碳基材料颗粒破碎风险，减少副反应的发生，另一方面还可以提升负极膜层的压实密度，缓冲负极膜层的体积变化。
在一些实施例中，上述第一碳基材料在20000N压力下的粉体压实密度为1.65g/cm3-2.0g/cm3，可选为1.68g/cm3-1.98g/cm3。第一碳基材料的粉体压实密度在上述范围内时，可以使电池更好的兼顾能量密度和动力学性能。
在一些实施例中，上述第一碳基材料的体积分布粒径Dv50为8.0μm-25.0μm，可选为10.0μm-22.0μm。在一些实施例中，上述第一碳基材料的体积分布粒径Dv90为16.0μm-45.0μm，可选为16.5μm-42.0μm。
第一碳基材料的体积分布粒径Dv50和/或Dv90在上述范围内时，有利于提升活性离子和电子的传输性能，从而能够进一步提升二次电池的动力学性能，另外还可以减少副反应的发生，提升二次电池的循环性能。
在一些实施例中，上述第一碳基材料的粒度分布(Dv90-Dv10)/Dv50小于等于1.55，可选为0.90-1.50。第一碳基材料的粒度分布(Dv90-Dv10)/Dv50在上述范围内时，其颗粒堆积性能较好，有利于提升负极膜层的压实密度，从而能够进一步提升二次电池的能量密度；另外，还有利于调节负极膜层的孔隙分布，提升活性离子和电子传输性能，提升负极膜层对电解液的浸润和保持特性，从而提升二次电池的动力学性能和循环性能。
在一些实施例中，上述第一碳基材料的振实密度为0.85g/cm3-1.30g/cm3，可选为0.90g/cm3-1.25g/cm3。第一碳基材料的振实密度在上述范围内时，有利于改善加工性能。
在一些实施方式中，所述第一碳基材料的石墨化度大于等于95.5％，可选为95.5％-98.0％。通过 调节第一碳基材料的石墨化度在上述范围内，能够使二次电池具有更高的能量密度。另外，无定形碳材料的颗粒通常较硬，且棱角较多，加工性能较差，与集流体的粘结力较差，在极片加工时需要更大的冷压压力，容易对集流体造成损伤。当与石墨化度较高的第一碳基材料搭配使用时，可以减小极片加工过程的冷压压力，从而降低对集流体的损伤，较少电池循环过程中集流体开裂的风险，进一步改善电池的安全性能。
在一些实施例中，上述第一碳基材料和/或上述第二碳基材料包括一次颗粒。可选地，上述第一碳基材料中的上述一次颗粒的数量占比大于等于80％，例如可以为80％-100％，85％-90％，80％-90％，80％-100％，85％-90％，80％-100％，90％-100％，或95％-100％。上述第二碳基材料中的上述一次颗粒的数量占比大于等于80％，例如可以为80％-100％，85％-90％，80％-90％，80％-100％，85％-90％，80％-100％，90％-100％，或95％-100％。第一碳基材料和/或第二碳基材料包含适当比例的一次颗粒，能使其具有较高的结构稳定性，还能减少副反应的发生，从而提升二次电池的循环性能。
在一些实施例中，上述第二碳基材料的真实密为1.95g/cm3-2.22g/cm3，可选为1.97g/cm3-2.21g/cm3。通过使第二碳基材料的真实密度在上述范围内且小于第一碳基材料，有利于维持二次电池负极极片孔隙率，进而提升二次电池的动力学性能。
在一些实施例中，上述第二碳基材料的比表面积大于等于1.5m2/g，可选为1.9m2/g-7.5m2/g。通过使第二碳基材料的比表面积在上述范围内，有利于活性离子的快速脱嵌，从而能够进一步提升二次电池的动力学性能。
在一些实施例中，上述第二碳基材料的Dv50为4.0μm-15.0μm，可选为5.0μm-15.0μm。通过使第二碳基材料的体积分布粒径Dv50在上述范围内，有利于提升活性离子的传输性能，从而能够进一步提升二次电池的动力学性能。
在一些实施例中，上述第二碳基材料的粒度分布(Dv90-Dv10)/Dv50小于等于1.75，可选为1.1-1.75。第二碳基材料的粒度分布(Dv90-Dv10)/Dv50在上述范围内时，其颗粒堆积性能较好，有利于提升负极膜层的压实密度，提升二次电池的能量密度；另外，还有利于负极膜层的颗粒之间形成合理的孔道结构，提高负极膜层中活性离子和电子传输性能，进而提升二次电池的动力学性能。
在一些实施例中，所述第二碳基材料在20000N压力下的粉体压实密度为0.85g/cm3-1.35g/cm3，可选为0.90g/cm3-1.30g/cm3。第二碳基材料的粉体压实密度低于第一碳基材料的粉体压实密度，通过使第二碳基材料的粉体压实密度在上述范围内，有利于提升负极极片的孔隙率，提升负极膜层中活性离子传输性能，进而提升二次电池的动力学性能。
在一些实施例中，上述第二碳基材料的振实密度为0.80g/cm3-1.20g/cm3，可选为0.83g/cm3-1.15g/cm3。可以使二次电池更好的兼顾加工性能和动力学性能能。
在一些实施例中，所述第二碳基材料的克容量为330mAh/g-480mAh/g，可选为340mAh/g-470mAh/g。通过使第二碳基材料的克容量在上述范围内，能够进一步提升二次电池的能量密度。
在一些实施例中，上述第一碳基材料和/或第二碳基材料的至少部分表面具有碳包覆层。可选地，上述包覆层包括碳包覆层。可选地，上述第一碳基材料和/或第二碳基材的80％以上的表面覆盖有碳包覆层，进一步地，90％-100％的表面覆盖有碳包覆层。由此，有利于提升活性离子嵌入负极膜层的速度，提升负极膜层的活性离子传输性能，进而提升二次电池的动力学性能。
在一些实施例中，上述第一碳基材料的包覆层可以如下制备：将第一碳基材料与有机碳源混合后进行碳化处理，以在颗粒的至少部分表面形成碳包覆层。可选地，上述有机碳源可采用本领域已知的适合进行包覆的含碳材料，例如，可包括煤沥青、石油沥青、环氧树脂、酚醛树脂、高分子聚合物等中的一种或多种。可选地，上述碳化温度为900℃-1300℃。另外，上述第二碳基材料的包覆层可以通过如下方法制备：方法1:采用化学气相沉积法在1200-1600℃的温度下在第二碳基材料表面沉积碳材料，气体为甲烷、乙烯、乙炔中的一种；方法2：将第二碳基材料与包覆剂混合在1600-2600℃的温度下进行热处理，所述包覆剂为沥青或聚合物的一种或多种。由此，有利于调整第二碳基材料的ID/IG，进而进一步提升二次电池的循环性能。
在一些实施例中，上述第一碳基材料在上述负极活性材料中的含量为大于等于40wt％，可选地为50wt％-80wt％，例如为55wt％-75wt％、60wt％-70wt％。第一碳基材料的含量在上述范围内时，使得二次电池能够兼顾高能量密度、良好的动力学性能和循环性能。另外，上述第二碳基材料在上述负极活性材料中的含量可以为20wt％-50wt％、可选地为25wt％-45wt％、30wt％-40wt％。
在一些实施例中，上述负极活性材料还可以进一步包括除了上述第一碳基材料和第二硅基材料 以外的其他本领域已知的负极活性材料，例如，上述负极活性材料还可以包括硅基材料，硅基材料具有较高的嵌锂电位。有利于提升二次电池的动力学性能；同时还能提升负极容量，从而还能进一步提升二次电池的能量密度。可选地，上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。
在一些实施例中，在上述负极膜层中上述负极活性材料还包括硅基材料时，上述硅基材料的含量为3wt％-30wt％，例如，可以为4wt％-25wt％、5wt％-20wt％。由此能在提升二次电池的动力学性能和能量密度的同时，使二次电池兼顾良好的循环性能和循环性能。
在一些实施例中，上述负极膜层还可选地包括负极导电剂。本公开对负极导电剂的种类没有特别的限制，作为示例，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，上述负极膜层还可选地包括负极粘结剂。本公开对负极粘结剂的种类没有特别的限制，作为示例，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，上述负极膜层还可选地包括其他助剂。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，上述负极膜层的压实密度为1.40g/cm3-1.70g/cm3，可选为1.45g/cm3-1.67g/cm3。由此有利于负极膜层兼顾高容量、高活性离子和电子传输性能，进而有利于二次电池兼顾高能量密度以及良好的循环性能和动力学性能。
在一些实施例中，上述负极膜层的面密度为5.0mg/cm2-25.0mg/cm2，可选为5.5mg/cm2-22.5mg/cm2。由此有利于负极膜层兼顾高容量、高活性离子和电子传输性能，进而有利于二次电池兼顾高能量密度以及良好的循环性能和动力学性能。
在一些实施例中，上述负极膜层的厚度为40μm-120μm，可选45μm-100μm。
在一些实施例中，上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。上述复合集流体可包括高分子材料基层以及形成于上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，上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，上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。
负极集流体具有在自身厚度方向相对的两个表面，负极膜层设置在负极集流体的两个相对表面中的任意一者或两者上。需要说明的是，本公开所给的各负极膜层参数(例如压实密度、面密度、厚度等)均指负极集流体单侧的负极膜层的参数。当负极膜层设置在负极集流体的两侧时，其中任意一侧的负极膜层参数满足本公开，即认为落入本公开的保护范围内。
在本公开中，上述负极极片中除了上述负极膜层之外还可以包括其他附加功能层。例如，在一些实施例中，负极极片还包括夹在上述负极集流体和上述负极膜层之间、设置在上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，负极极片还包括覆盖在上述负极膜层表面的保护层。
在本公开中，材料(例如第一碳基材料、第二碳基材料等)的ID/IG可使用拉曼光谱仪进行测试，ID表示材料的拉曼光谱在1350±50cm-1处的D峰强度，IG表示材料的拉曼光谱在1580±50cm-1处的G峰强度。测试条件为：激发波长为532nm，光栅为600刻线，物镜为50倍，积分时间为10s，累计次数为3次，面扫，得到100个点的D峰、G峰强度，计算100个点的ID/IG，去除最大与最小的各30个ID/IG，剩余40个点的平均值即为材料的ID/IG。测试仪器可以采用Horiba LabRAM HR800拉曼光谱仪。
在本公开中，材料(例如第一碳基材料、第二碳基材料等)的X射线衍射分析测试，可采用铜靶作为阳极靶，以CuKα射线为辐射源，射线波长扫描2θ角范围为20°-80°，扫描速率4°/min。
在本公开中，材料(例如第一碳基材料、第二碳基材料等)的HR-TEM，可以采用本领域已知的方法测试。例如，参考标准JBT9352-1999，使用聚焦离子束FIB对粉末进行切片，切片厚度～100nm，在透射电镜下测试。
在本公开中，材料(例如第一碳基材料、第二碳基材料等)的真实密度为本领域公知的含义，可以采用本领域已知的方法测试。参考标准GB/T 24586-2009，示例性测试方法如下：取洁净干燥的样品杯放置在天平，清零，将粉末样品加入到样品杯中，约占样品杯体积的1/2，记录样品质量。 将装有样品的样品杯，置于真密度测试仪，密闭测试系统，按程序通入氦气，通过检测样品室和膨胀室中的气体的压力，再根据玻尔定律(PV＝nRT)来计算真实体积，从而计算真密度。测试样品杯体积：3.5cm3，分析气体：氦气。
在本公开中，材料(例如第一碳基材料、第二碳基材料等)表面是否存在包覆层可以通过高分辨透射电子显微镜(HR-TEM)进行判断。
在本公开中，克容量为本领域公知的含义，可以采用本领域已知的方法测试。示例性测试方法如下：将样品粉末与导电剂炭黑(Super P)、粘结剂聚偏氟乙烯(PVDF)按质量比91.6:1.8:6.6与溶剂N-甲基吡咯烷酮(NMP)混合均匀，制成浆料；将制备好的浆料涂布于负极集流体铜箔的表面上，于烘箱中干燥后备用；将碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)按照体积比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1mol/L的电解液；然后以金属锂片为对电极，聚乙烯(PE)薄膜作为隔离膜，与上述电解液在氩气保护的手套箱组装成CR2430型扣式电池；将所得扣式电池静置12h后，在25℃下，以0.05C恒流放电至0.005V，静置10分钟，以50μA的电流再恒流放电至0.005V，静置10分钟，以10μA再恒流放电至0.005V；然后以0.1C恒流充电至2V，记录充电容量。充电容量与样品质量的比值即为对应材料的克容量。
在本公开中，材料(例如第一碳基材料、第二碳基材料等)的比表面积为本领域公知的含义，可以用本领域已知的仪器及方法进行测定。例如可以参照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。
在本公开中，材料(例如第一碳基材料、第二碳基材料等)的体积分布粒径Dv10、Dv50、Dv90为本领域公知的含义，其分别表示材料累计体积分布百分数达到10％、50％、90％时所对应的粒径，可以用本领域已知的仪器及方法进行测定。例如可以参照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。
在本公开中，材料(例如第一碳基材料、第二碳基材料等)的粉体压实密度为本领域公知的含义，可以用本领域已知的仪器及方法进行测定。例如可以参照GB/T 24533-2009，通过电子压力试验机(例如可以为UTM7305型电子压力试验机)进行测定。示例性测试方法如下：称取1g样品粉末，加入底面积为1.327cm2的模具中，加压至2000kg，保压30s，然后卸压，保持10s，然后记录并计算得到材料在20000N压力下的粉体压实密度。
在本公开中，材料(例如第一碳基材料、第二碳基材料等)的振实密度为本领域公知的含义，可以用本领域已知的仪器及方法进行测定。例如可参照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±0.2mm，振动次数5000次，量筒25mL。
在本公开中，材料(例如第一碳基材料、第二碳基材料等)的石墨化度为本领域公知的含义，可以用本领域已知的仪器及方法进行测试。例如可以使用X射线衍射仪(如Bruker D8 Discover)进行测试，测试可参考JIS K 0131-1996、JB/T 4220-2011，得到材料晶体结构中C(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。在上述公式中，d002是以纳米(nm)表示的材料晶体结构中C(002)晶面的平均层间距。
在本公开中，一次颗粒为本领域公知的含义。一次颗粒是指非团聚态的颗粒。由两个或两个以上一次颗粒聚集形成团聚态的颗粒为二次颗粒。一次颗粒可以通过使用扫描电子显微镜(SEM)图进行区分。
在本公开中，第一碳基材料和/或第二碳基材料中一次颗粒的数量占比是指：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第一碳基材料的个数占第一碳基材料颗粒总个数的占比，多个统计结果的平均值即为第一碳基材料中一次颗粒的数量占比。
在本公开中，负极膜层的面密度为本领域公知的含义，可以用本领域已知的方法进行测试。例如，可取单面涂布且经冷压后的负极极片(若是双面涂布的负极极片，可先擦拭掉其中一面的负极膜层)，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。负极极片的面密度＝(M1-M0)/S1。
在本公开中，负极膜层的压实密度为本领域公知的含义，可以用本领域已知的方法进行测试。负极膜层的压实密度＝负极膜层的面密度/负极膜层的厚度。负极膜层的厚度为本领域公知的含义，可采用本领域已知的方法进行测试，例如采用万分尺(例如Mitutoyo293-100型，精度为0.1μm)。
需要说明的是，上述针对负极活性材料或负极膜层的各种参数测试，可以按照如下步骤从制备 好的二次电池中取样测试。
将二次电池做放电处理(为了安全起见，一般使二次电池处于满放状态)；将二次电池拆卸后取出负极极片，使用碳酸二甲酯将负极极片浸泡一定时间(例如2h-10h)；然后将负极极片取出并在一定温度和时间下干燥处理(例如60℃，4h以上)，干燥后取出负极极片。此时即可以在干燥后的负极极片中取样测试上述的负极膜层相关的各参数，例如负极膜层的面密度、压实密度、厚度等。
将上述干燥后的负极极片在一定温度及时间下烘烤(例如400℃，2h以上)，在烘烤后的负极极片中任选一区域，对负极活性材料取样(可以选用刀片刮粉取样)；将收集到的负极活性材料过筛处理(例如用200目的筛网过筛)，最终得到可以用于测试上述各负极活性材料参数的样品。
可以通过SEM来区分第一碳基材料和第二碳基材料。图2是本公开的负极极片的一实施方式的SEM图，从图中可以看出，颗粒截面具有明显的孔结构为第一碳基材料，颗粒截面无孔结构为第二碳基材料。
在本公开中，上文提到的第二碳基材料可以通过商购获得，也可以按照本领域公知的方法进行制备，另外，上文提到的第一碳基材料可以通过如下的方法制备获得。
在一些实施例中，上述第一碳基材料的制备方法包括：步骤1，提供具有多个孔结构的原料；步骤2，将上述原料与填充材料按照预定比例混合均匀，之后在第一温度T1下保温第一时间t1，结束后冷却至室温得到中间体；步骤3，将所获得的中间体在第二温度T2下保温第二时间t2，结束后得到第一碳基材料。
在一些实施例中，在步骤1中，用于制备上述第一碳基材料的上述原料包括天然石墨。天然石墨一般是指自然界天然形成的石墨，不需要经过石墨化，且天然石墨颗粒的内部通常存在较多的闭孔结构。可选地，上述天然石墨包括鳞片石墨、天然球形石墨和微晶石墨中的一种或多种，更可选为包括天然球形石墨。
“天然球形石墨”是指具有球状或类球状的天然石墨，并且并非将所有的天然石墨颗粒都控制为理想的球。在一些实施例中，可以通过对鳞片石墨进行预处理以获得所需的颗粒尺寸和形貌的天然球形石墨，可选地，上述预处理包括破碎、分级、球化、纯化等工序。
在一些实施例中，在步骤1中，上述原料的体积分布粒径Dv50可为6.0μm-25.0μm。
在一些实施例中，在步骤1中，上述原料的比表面积可为大于等于2.5m2/g，可选为2.5m2/g-10.0m2/g。当原料的比表面积在上述范围内时，有利于进行后续的填充处理和获得所需比表面积的第一碳基材料，还有利于第一碳基材料同时具有高容量和高首次库伦效率，此外，还有利于第一碳基材料具有更好的动力学性能。
在一些实施例中，在步骤2中，上述填充材料的软化点温度为90℃-150℃。可选地，上述填充材料的软化点温度为94℃-146℃，94℃-142℃，94℃-138℃，94℃-134℃，94℃-130℃，104℃-146℃，104℃-142℃，104℃-138℃，104℃-134℃，104℃-130℃。
在一些实施例中，在步骤2中，上述填充材料的体积分布粒径Dv50为小于等于6μm，可选为1μm-6μm，1μm-5μm，2μm-5μm，3μm-5μm。由此有利于填充材料受热熔融后填充进入原料的孔结构中，还有利于提高填充材料与原料的分散均匀性。
在一些实施例中，在步骤2中，上述填充材料的结焦值为15％-40％，可选为18％-34％。在本公开中，填充材料的结焦值为本领域公知的含义，可以用本领域已知的仪器及方法进行测定。例如可以参照GB/T 8727-2008进行测定。
在一些实施例中，在步骤2中，上述填充材料包括煤沥青、石油沥青、高分子化合物和树脂中的一种或多种，可选为包括煤沥青和石油沥青中的一种或多种。
在一些实施例中，在步骤2中，上述填充材料与上述原料的质量比为(10-40):100，可选为(10-30):100，(10-25):100，(10-20):100，(12-30):100，(14-28):100，(15-25):100。通常情况，在其他工艺条件不变时，填充材料的加入量越多，第一碳基材料的ID/IG越大。本领域技术人员可以根据需求，在上述所给的质量比范围内进行调整，得到所需的ID/IG数值。
在步骤2中，通过调节填充材料的种类、软化点、结焦值、添加量等中的一个或多个参数在上述范围内，有利于调节第一碳基材料的外部区域和内部区域中的孔数量和/或孔尺寸在合适的范围内，有利于调节第一碳基材料的S2/S1在合适范围内。
通过调节填充材料的种类、软化点、结焦值、添加量等参数在上述范围内，填充材料受热熔融后，黏度不高，保持良好的流动性，同时不易粘接原料颗粒，能够减少原料颗粒在后续制备过程中团聚，由此还能够减少由于需要增加解聚工序而导致第一碳基材料颗粒表面缺陷增加、表面活性位点增多等问题。
在一些实施例中，在步骤2中，将上述原料与上述填充材料按照预定比例混合均匀后升温至第一温度T1的升温工艺可为分阶段升温工艺。
在一些实施例中，上述分阶段升温工艺包括第一升温工艺、第二升温工艺和第三升温工艺。
在一些实施例中，上述第一升温工艺为升温至200℃-250℃并在该温度下保温0.5h-3h。
在一些实施例中，上述第二升温工艺为升温至450℃-550℃并在该温度下保温0h-2h。当保温时间为0h时，表示升温至450℃-550℃范围内时，未进行保温处理，而是继续升温至第一温度T1。
在一些实施例中，上述第三升温工艺为升温至上述第一温度T1并在该温度下保温第一时间t1。
在分阶段升温过程中，首先升温至200℃-250℃，由于加热温度高于填充材料的软化点温度，因此，此时填充材料受热熔融软化，保温0.5h-3h可以使其流动填充至原料的孔结构中；之后升温至450℃-550℃，此时熔融软化的填充材料发生碳化反应，逐渐形成半焦状态，变为粘稠液体或者固体，由此避免填充材料进入原料的全部孔结构中；最后升温至第一温度，此时填充材料发生碳化反应，由此能够使得填充材料占据的孔结构被有效填充。
在一些实施例中，在步骤2中，以1℃/min-10℃/min的速率升温至上述第一温度T1。例如升温速率可以为1℃/min，2℃/min，3℃/min，4℃/min，5℃/min，6℃/min，7℃/min，8℃/min，9℃/min，10℃/min或以上任何数值组成的范围。可选地，升温速率为1.5℃/min-8℃/min，1.5℃/min-6℃/min，2℃/min-6℃/min，2℃/min-5℃/min。
在一些实施例中，上述第一升温工艺的升温速率可为1℃/min-10℃/min，可选为1.5℃/min-8℃/min，1.5℃/min-6℃/min，2℃/min-6℃/min，2℃/min-5℃/min。在一些实施例中，上述第二升温工艺的升温速率可为1℃/min-10℃/min，可选为2℃/min-8℃/min。在一些实施例中，上述第三升温工艺的升温速率可为1℃/min-10℃/min，可选为2℃/min-8℃/min。
在一些实施例中，在步骤2中，上述第一温度T1为700℃-1200℃。例如第一温度T1可以为700℃，750℃，800℃，850℃，900℃，950℃，1000℃，1050℃，1100℃，1200℃或以上任何数值组成的范围。可选地，上述第一温度T1为750℃-1100℃，800℃-1100℃，850℃-1100℃，900℃-1100℃，850℃-1000℃。
在一些实施例中，在步骤2中，上述第一时间t1为1h-5h。例如第一时间t1可以为1h，1.5h，2h，2.5h，3h，3.5h，4h，4.5h，5h或以上任何数值组成的范围。可选地，上述第一时间t1为2h-4h。
在一些实施例中，在步骤2中，热处理可在中频炉、辊道窑、回转窑、推板窑、立式造粒釜、卧式造粒釜、立式反应釜、卧式反应釜或滚筒炉等能够进行程序升温的设备中进行。
在一些实施例中，在步骤2中，热处理气氛可为保护气体气氛。上述保护气体可包括氮气、氩气、氦气中的一种或多种。
在步骤2中，通过调节升温速率、第一温度、第一时间、升温工艺等中的一者或者多者在上述范围内，有利于调节第一碳基材料的外部区域和内部区域中的孔数量和/或孔尺寸在合适的范围内，进而有利于调节第一碳基材料的S2/S1在合适范围内。
在一些实施例中，在步骤3中，上述第二温度T2为2070℃-2700℃。可选地，上述第二温度T2为2070℃-2570℃，2070℃-2510℃，2070℃-2450℃，2070℃-2360℃，2140℃-2570℃，2140℃-2510℃，2140℃-2450℃，2140℃-2360℃。
在一些实施例中，在步骤3中，上述第二时间t2为1.5h-6h。例如第二时间t1可以为2h，2.5h，3h，3.5h，4h，4.5h，5h，5.5h，6h或以上任何数值组成的范围。可选地，上述第二时间t2为2h-5h。
在一些实施例中，在步骤3中，上述热处理可在中频炉、箱式石墨化炉、艾奇逊石墨化炉、连续式石墨化炉或内串石墨化炉中进行。
在一些实施例中，在步骤3中，中频炉、连续石墨化热处理气氛可为保护气体气氛。上述保护气体可包括氩气、氦气中的一种或多种。
在步骤3中，通过调节第二温度、第二时间中的一者或者多者在上述范围内，有利于调节第一碳基材料中无序碳的含量在合适范围内，有利于第一碳基材料具有合适的石墨化度、层间距和ID/IG等。一般情况，在其他工艺条件不变时，第二温度越高，第一碳材料的ID/IG越小。本领域技术人员可以根据需求，在上述所给的温度范围内进行调整，得到所需的ID/IG数值。
在上述第一碳基材料的制备方法中，通过调节天然石墨的参数、填充材料的参数、升温速率、第一温度、第一时间、升温工艺、第二温度、第二时间等中的一者或者多者在上述范围内，有利于调节第一碳基材料的S2/S1、石墨化度、克容量、粒径、粉体压实密度、振实密度、对亚麻仁油的吸附量等参数。
在一些实施例中，将上述得到的第一碳基材料与有机碳源混合后进行碳化处理，以在颗粒的至 少部分表面形成碳包覆层。可选地，上述有机碳源可采用本领域已知的适合进行包覆的含碳材料，例如，可包括煤沥青、石油沥青、酚醛树脂、椰壳等中的一种或多种。可选地，上述碳化温度为900℃-1300℃。
在一些实施例中，上述第二碳基材料通过商业渠道购买。
[正极极片]
在一些实施例中，上述正极极片包括正极集流体以及设置在上述正极集流体至少一个表面的正极膜层。例如，上述正极集流体具有在自身厚度方向相对的两个表面，上述正极膜层设置于上述正极集流体的两个相对表面中的任意一者或两者上。
上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。上述复合集流体可包括高分子材料基层以及形成于上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，上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，上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。
上述正极膜层通常包含正极活性材料、可选的粘结剂和可选的导电剂。上述正极膜层通常是将正极浆料涂布在上述正极集流体上，经干燥、冷压而成的。上述正极浆料通常是将正极活性材料、可选的导电剂、可选的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。
上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，上述正极活性材料上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。上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。上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，为了进一步提升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上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，上述电解质采用电解液，上述电解液包括电解质盐和溶剂。
上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，上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。
上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，上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，上述电解液还可选地包括添加剂。例如，上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]
本公开对上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，上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。上述隔离膜可以是单层薄膜，也可以是多层复合薄膜。上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，上述正极极片、上述隔离膜和上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，上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。上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3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4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用于盖设上述开口，以封闭上述容纳腔。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封装于上述容纳腔。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5是作为一个示例的电池模块4的示意图。如图5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。
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6和图7是作为一个示例的电池包1的示意图。如图6和图7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。
本公开还提供一种用电装置，上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。上述二次电池、电池模块或电池包可以用作上述用电装置的电源，也可以用作上述用电装置的能量存储单元。上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。
上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8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，实施例中使用的仪器均可商购获得。
第一碳基材料的制备
材料1-1
步骤1，将鳞片石墨进行机械粉碎、分级、球化、纯化处理，获得天然球形石墨。步骤2，将所获得的天然球形石墨与填充剂石油沥青按照100：25的比例范围进行混合，石油沥青的软化点为120℃、结焦值为36％，之后将混合后的物料置于可程序升温的设备中，升温至200℃保温1h(第一升温工艺)，再持续升温至700℃，保温2h(第三升温工艺)，结束后冷却至室温，得到中间体。步骤3，将所获得的中间体置于石墨化炉中，进行2580℃热处理，结束后除磁、筛分得到第一碳基材料。所得第一碳基材料的ID/IG数值为0.152，S2/S1为14.7，DV50为18.3μm。
第一碳基材料的S2/S1采用如下方法测试获得。
将制样用粘结剂与第一碳基材料粉末混合均匀后涂到铜箔上，60℃烘干30min备用；在5个不同位置处剪成6mm×6mm大小的5个待测样品，分别粘贴在CP型氩离子截面抛光仪的样品台上；使用等离子束对样品进行切割，获得各样品的截面。测试仪器可以为日本JEOL公司的IB-09010CP型氩离子截面抛光仪。
使用扫描电子显微镜对第一碳基材料的各样品截面进行扫描，在各样品截面中任意选取区域获得扫描图像。测试可参考JY/T010-1996。测试仪器可以为德国ZEISS公司的Sigma 300型扫描电子显微镜。
随机从扫描图像中选取第一碳基材料的20个颗粒的截面。从第一碳基材料的颗粒表面向颗粒内部延伸0.25μm的距离所构成的区域记为外部区域，外部区域内侧的区域记为内部区域。使用图像处理软件获取每个颗粒截面的外部区域的总孔面积S1’，以及第一碳基材料的内部区域的孔面积S2’，计算获得S2’/S1’的值；并计算全部20个颗粒的S2’/S1’的算数平均值作为第一碳基材料的S2/S1的值。图像处理软件可以为AVIZO。
材料1-2～材料1-5
材料1-2～材料1-5的制备方法与上述材料1-1的制备方法类似，不同点在于：调整天然球形石墨与填充剂石油沥青混合比例及热处理温度，使得第一碳基材料的ID/IG数值为表1所示数值。
表1
材料1-6～材料1-10
材料1-6～材料1-10的制备方法与上述材料1-1的制备方法类似，不同点在于：如表2所示调整填充材料的软化点温度、结焦值、天然球形石墨与填充剂石油沥青混合比例，并调整第三升温工艺，使得第一碳基材料的S2/S1为表2所示的数值。
表2
材料1-11
材料1-11的制备方法与上述材料1-3的制备方法类似，不同点在于：将鳞片石墨进行机械粉碎、分级、球化后的粒度分布Dv50调整为10.2μm。
第二碳基材料(无定形碳)的制备：
材料2-1
将椰壳作为原料，经600℃热处理，破碎，碱渍除杂，1000℃热处理，得到无定形碳材料。然后，对无定形碳进行包覆及热处理，将无定形碳与包覆剂按照质量比100：10进行混合，在2450℃的温度下进行热处理，所述包覆剂为沥青。经过除磁、筛分，得到第二碳基材料。所得第二碳基材料的ID/IG数值为0.17，Dv50为10.2μm。
材料2-2～材料2-4
与上述材料2-1的制备方法类似，不同点在于：如表3所示调整包覆剂用量和热处理温度，得到具有表3所示的ID/IG的第二碳基材料。
表3
材料2-5
与上述材料2-1的制备方法类似，不同点在于：破碎、后的粒度分布Dv50调整为14.5μm。
实施例1
二次电池的制备
1、负极极片：将负极活性材料(将上述材料1-1(第一碳基材料)和材料2-1(第二碳基材料)按照质量比70：30进行混合的混合物)、导电剂炭黑(Super P)、增稠剂羧甲基纤维素钠、粘结剂丁苯橡胶按照重量比96.4:1:1.2:1.4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。
2、正极极片：将LiNi0.5Co0.2Mn0.3O2(NCM523)与导电剂炭黑(Super P)、粘结剂聚偏氟乙烯按照重量比96:2:2混合，加入适量溶剂NMP，搅拌均匀，获得正极浆料。将正极浆料涂布在正极集流体铝箔的两个表面上，经干燥、冷压后，获得正极极片。
3、电解液：将碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)按照体积比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1mol/L的电解液。
4、隔膜：采用聚丙烯膜。
5、二次电池的制备：将上述制备的正极极片和负极极片按顺序放好，使隔离膜处于正极极片和负极极片中间起到隔离作用，之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，得到二次电池。
实施例2-8
实施例2-8的电池制备方法与实施例1类似，不同点在于：第一碳基材料或第二碳基材料选择了ID/IG不同的材料，具体详见表4。
对比例1
与实施例1的制备方法相似组装二次电池，不同点在于：负极活性材料中仅包含实施例1中使用的第二碳基材料2-1。
对比例2
与实施例1的制备方法相似组装二次电池，不同点在于：负极活性材料中仅包含第一碳基材料1-3。
性能测试
(1)能量密度
在25℃下，将二次电池以1/3C进行恒流充电到4.3V，然后在4.3V下恒压充电至电流0.05C，静置5min，然后以1/3C电流恒流放电到2.8V，记录此时电池放电能量。电池放电能量除以电池的重量即为电池的重量能量密度，单位为Wh/kg。测量数据详见表4。
(2)二次电池的快速充电性能测试
在25℃下，将二次电池以0.33C恒流充电至4.3V，然后恒压充电至电流为0.05C，静置5min之后，将二次电池以0.33C恒流放电至2.8V，记录其实际容量为C0。
然后将二次电池依次以1.0C0、1.3C0、1.5C0、1.8C0、2.0C0、2.3C0、2.5C0、3.0C0、恒流充电至4.3V或者0V负极截止电位(以先达到者为准)，每次充电完成后需以1C0放电至2.8V，记录不同充电倍率下充电至10％、20％、30％、……、80％SOC(State of Charge，荷电状态)时所对应的负极电位，绘制出不同SOC态下的充电倍率-负极电位曲线，线性拟合后得出不同SOC态下负极电位为0V时所对应的充电倍率，该充电倍率即为该SOC态下的充电窗口，分别记为C10％SOC、C20％SOC、C30％SOC、C40％SOC、C50％SOC、C60％SOC、C70％SOC、C80％SOC，根据公式(60/C20％SOC+60/C30％SOC+60/C40％SOC+60/C50％SOC+60/C60％SOC+60/C70％SOC+60/C80％SOC)×10％计算得到该二次电池从10％SOC充电至80％SOC的充电时间T(在二次电池不析锂的前提下)，单位为min。
该充电时间越短，则二次电池的动力学性能越优秀。
(3)二次电池的循环性能测试
在45℃下，将上述制备的二次电池以1C恒流充电至上限截止电压4.3V(对应100％SOC)，然后恒压充电至电流为0.05C，静置5min之后，将二次电池以1C恒流放电至下限截止电压2.8V(对应0％SOC)，记录此时的放电容量，即为第1圈放电容量。将二次电池按照上述方法进行循环充放电测试，记录每圈循环后的放电容量。
二次电池45℃循环1000圈容量保持率(％)＝1000圈循环后的放电容量/第1圈放电容量×100％。
表4
从表4的结果可知，实施例中通过使负极膜层中的负极活性材料同时包括本公开的第一碳基材料和第二碳基材料，能够在具有高能量密度的同时，兼顾优异的循环性能和动力学性能。另外，通过使第一碳基材料的ID/IG在0.155-0.220的范围内，能够获得能量密度、循环性能和动力学性能的均衡性更好的二次电池。
另外，与实施例相比，对比例1和对比例2中，由于仅包含第一碳基材料或者第二碳基材料，无法获得本公开的技术效果。
实施例9-13
实施例9-13的电池制备方法与实施例1类似，不同点在于：第一碳基材料选择了S2/S1不同的材料，分别选用材料1-6～材料1-10，具体详见表5。
需要说明的是，为了便于比较，将实施例3的数据也一并列入表5中。
表5
由表5可以看出，通过使第一碳基材料的S2/S1在2.5～460的范围内，二次电池的容量保持率进一步提高，获得更好的循环性能。
实施例14
实施例14的电池制备方法与实施例1类似，不同点在于：第一碳基材料和第二碳基材料选择了DV50不同的材料，具体详见表6。
需要说明的是，为了便于比较，将实施例3的数据也一并列入表6中。
表6
由表6可以看出，通过使第一碳基材料的DV50大于第二碳基材料的DV50，二次电池的能量密度进一步提高，充电时间缩短，电池动力学更加优异。
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 (20)

  1. 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位于所述负极集流体至少一个表面上且包括负极活性材料的负极膜层，其中，
    所述负极活性材料包括第一碳基材料和第二碳基材料；
    所述第一碳基材料具有孔结构，且所述第一碳基材料的ID/IG小于等于0.280，其中，ID表示拉曼光谱中在1350±50cm-1处的D峰强度，IG表示拉曼光谱中在1580±50cm-1处的G峰强度；
    所述第二碳基材料为无定形碳材料。
  2. 根据权利要求1所述的二次电池，其中，所述第一碳基材料的ID/IG为0.155-0.220。
  3. 根据权利要求1或2所述的二次电池，其中，所述第二碳基材料的ID/IG小于等于0.250，可选地，所述第二碳基材料的ID/IG小于等于0.230。
  4. 根据权利要求1～3中任一项所述的二次电池，其中，所述第一碳基材料的Dv50大于所述第二碳基材料的Dv50。
  5. 根据权利要求1～4中任一项所述的二次电池，其中，
    所述第一碳基材料的X射线粉末衍射图谱在2θ衍射角为26.5°±0.2°、44.5°±0.2°、54.6°±0.2°处具有衍射峰，
    所述第二碳基材料的X射线粉末衍射图谱中不存在衍射峰。
  6. 根据权利要求1～5中任一项所述的二次电池，其中，
    所述第一碳基材料在HR-TEM中有晶格条纹，
    所述第二碳基材料在HR-TEM中无晶格条纹。
  7. 根据权利要求1～6中任一项所述的二次电池，其中，
    所述第一碳基材料在20000N压力下的粉体压实密度大于所述第二碳基材料在20000N压力下的粉体压实密度。
  8. 根据权利要求1～7中任一项所述的二次电池，其中，
    所述第一碳基材料的真实密度大于所述第二碳基材料的真实密度。
  9. 根据权利要求1～8中任一项所述的二次电池，其中，
    所述第一碳基材料的真实密度为2.22g/cm3-2.27g/cm3，可选为2.23g/cm3-2.26g/cm3。
  10. 根据权利要求1～9中任一项所述的二次电池，其中，
    所述第一碳基材料包括一个以上孔面积大于等于0.15μm2的孔结构，可选地包括一个以上孔面积为0.15μm2-2.0μm2的孔结构。
  11. 根据权利要求1～10中任一项所述的二次电池，其中，
    所述第一碳基材料包括外部区域以及位于所述外部区域内侧的内部区域，所述外部区域是指从所述第一碳基材料的颗粒表面向颗粒内部延伸2.5μm的距离所构成的区域，在所述第一碳基材料的截面图中，所述外部区域的总孔面积记为S1，所述内部区域的总孔面积记为S2，并且S2>S1，可选地，2.6≤S2/S1≤450.7。
  12. 根据权利要求11所述的二次电池，其中，
    所述第一碳基材料的外部区域中的孔结构的面积为小于等于0.15μm2，可选为小于等于0.13μm2；和/或，
    所述第一碳基材料的内部区域中包括一个以上面积大于等于0.15μm2的孔结构，可选地包括一个以上面积为0.15μm2-2.0μm2的孔结构。
  13. 根据权利要求1～12中任一项所述的二次电池，其中，所述第一碳基材料满足如下条件中的至少一者：
    (1)所述第一碳基材料在20000N压力下的粉体压实密度为1.65g/cm3-2.0g/cm3，可选为1.68g/cm3-1.98g/cm3；
    (2)所述第一碳基材料的体积分布粒径Dv50为8.0μm-25.0μm，可选为10.0μm-22.0μm；
    (3)所述第一碳基材料的体积分布粒径Dv90为16.0μm-45.0μm，可选为16.5μm-42.0μm；
    (4)所述第一碳基材料的粒度分布(Dv90-Dv10)/Dv50小于等于1.55，可选为0.90-1.50；
    (5)所述第一碳基材料的振实密度为0.85g/cm3-1.30g/cm3，可选为0.90g/cm3-1.25g/cm3；
    (6)所述第一碳基材料的石墨化度大于等于95.5％，可选为95.5％-98.0％。
  14. 根据权利要求1～13中任一项所述的二次电池，其中，
    所述第一碳基材料和/或所述第二碳基材料包括一次颗粒；
    可选地，所述第一碳基材料中的所述一次颗粒的数量占比大于等于80％；
    可选地，所述第二碳基材料中的所述一次颗粒的数量占比大于等于80％。
  15. 根据权利要求1～14中任一项所述的二次电池，其中，所述第二碳基材料满足如下条件中的至少一者：
    (1)所述第二碳基材料的真实密度为1.95g/cm3-2.22g/cm3，可选为1.97g/cm3-2.21g/cm3
    (2)所述第二碳基材料的比表面积大于等于1.5m2/g，可选为1.9m2/g-7.5m2/g；
    (3)所述第二碳基材料的Dv50为4.0μm-15.0μm，可选为5.0μm-15.0μm；
    (4)所述第二碳基材料的粒度分布(Dv90-Dv10)/Dv50小于等于1.75，可选为1.1-1.75；
    (5)所述第二碳基材料在20000N压力下的粉体压实密度为0.85g/cm3-1.35g/cm3，可选为0.90g/cm3-1.30g/cm3；
    (6)所述第二碳基材料的振实密度为0.80g/cm3-1.20g/cm3，可选为0.83g/cm3-1.15g/cm3；
    (7)所述第二碳基材料的克容量为330mAh/g-480mAh/g，可选为340mAh/g-470mAh/g。
  16. 根据权利要求1～15中任一项所述的二次电池，其中，
    所述第一碳基材料和/或所述第二碳基材料的至少部分表面具有包覆层；可选地，所述包覆层包括碳包覆层。
  17. 根据权利要求1～16中任一项所述的二次电池，其中，
    在所述负极活性材料中，所述第一碳基材料的含量大于等于40wt％，可选为50wt％-80wt％。
  18. 根据权利要求1～17中任一项所述的二次电池，其中，所述负极活性材料还包括硅基材料；可选地，在所述负极活性材料中，所述硅基材料的含量为3wt％-30wt％。
  19. 根据权利要求1～18中任一项所述的二次电池，其中，
    所述负极膜层满足如下(1)-(3)中的至少一者：
    (1)所述负极膜层的压实密度为1.40g/cm3-1.70g/cm3，可选为1.45g/cm3-1.67g/cm3；
    (2)所述负极膜层的面密度为5.0mg/cm2-25.0mg/cm2，可选为5.5mg/cm2-22.5mg/cm2；
    (3)所述负极膜层的厚度为40μm-120μm，可选45μm-100μm。
  20. 一种用电装置，包括权利要求1-19中任一项所述的二次电池。
PCT/CN2024/095322 2023-11-30 2024-05-24 二次电池以及用电装置 Pending WO2025112368A1 (zh)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CN202311641312.6 2023-11-30
CN202311641312.6A CN120073031A (zh) 2023-11-30 2023-11-30 二次电池以及用电装置

Publications (1)

Publication Number Publication Date
WO2025112368A1 true WO2025112368A1 (zh) 2025-06-05

Family

ID=95804740

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/CN2024/095322 Pending WO2025112368A1 (zh) 2023-11-30 2024-05-24 二次电池以及用电装置

Country Status (2)

Country Link
CN (1) CN120073031A (zh)
WO (1) WO2025112368A1 (zh)

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2005243508A (ja) * 2004-02-27 2005-09-08 Jfe Chemical Corp リチウムイオン二次電池負極材料用複合黒鉛粒子、負極およびリチウムイオン二次電池
JP2019091793A (ja) * 2017-11-14 2019-06-13 旭化成株式会社 負極
JP2021116191A (ja) * 2020-01-22 2021-08-10 昭和電工株式会社 複合炭素材料及びリチウムイオン二次電池
CN114665064A (zh) * 2022-05-26 2022-06-24 宁德新能源科技有限公司 电化学装置
CN114725315A (zh) * 2017-01-06 2022-07-08 昭和电工材料株式会社 锂离子二次电池用负极材、锂离子二次电池用负极和锂离子二次电池

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2005243508A (ja) * 2004-02-27 2005-09-08 Jfe Chemical Corp リチウムイオン二次電池負極材料用複合黒鉛粒子、負極およびリチウムイオン二次電池
CN114725315A (zh) * 2017-01-06 2022-07-08 昭和电工材料株式会社 锂离子二次电池用负极材、锂离子二次电池用负极和锂离子二次电池
JP2019091793A (ja) * 2017-11-14 2019-06-13 旭化成株式会社 負極
JP2021116191A (ja) * 2020-01-22 2021-08-10 昭和電工株式会社 複合炭素材料及びリチウムイオン二次電池
CN114665064A (zh) * 2022-05-26 2022-06-24 宁德新能源科技有限公司 电化学装置

Also Published As

Publication number Publication date
CN120073031A (zh) 2025-05-30

Similar Documents

Publication Publication Date Title
WO2024168477A1 (zh) 二次电池及用电装置
WO2024168473A1 (zh) 二次电池及用电装置
WO2024108571A1 (zh) 二次电池及用电装置
US20250140854A1 (en) Secondary battery and electrical device
WO2024108574A1 (zh) 碳材料及其制备方法、以及含有其的二次电池和用电装置
WO2024108589A1 (zh) 二次电池及用电装置
WO2025112363A1 (zh) 一种二次电池及用电装置
WO2025112378A1 (zh) 一种二次电池及用电装置
WO2024108575A1 (zh) 碳材料及其制备方法、以及含有其的二次电池和用电装置
WO2024108578A1 (zh) 碳材料及其制备方法、以及含有其的二次电池和用电装置
WO2024108579A1 (zh) 碳材料及其制备方法、以及含有其的二次电池和用电装置
WO2025112368A1 (zh) 二次电池以及用电装置
WO2025112387A1 (zh) 二次电池以及用电装置
CN119072797B (zh) 碳材料及其制备方法、以及含有其的二次电池和用电装置
EP4517883A1 (en) Secondary battery and electric device
WO2025112364A1 (zh) 二次电池以及用电装置
US20250105293A1 (en) Carbon material, method for preparing the same, and secondary battery and electrical device comprising the same
US20250118753A1 (en) Carbon material, method for preparing the same, and secondary battery and electrical device comprising the same
US20250054957A1 (en) Secondary battery and electric device
WO2025112386A1 (zh) 一种二次电池及用电装置
WO2025112380A1 (zh) 二次电池以及用电装置

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 24895478

Country of ref document: EP

Kind code of ref document: A1