Carbon material, method for producing the same, secondary battery and power consumption device including the same

Abstract

The present application provides a carbon material, a method for producing the same, a secondary battery including the same, and a power consumption device. The carbon material includes a pore structure, and in the carbon material, the 3R phase and the 2H phase coexist, and 0 < I 3R(101) / I 2H(004) ≤ 0.100 is satisfied, where I 3R(101) is the peak intensity of the diffraction peak of the 101 crystal plane of the 3R phase in the X-ray diffraction spectrum of the carbon material, and I 2H(004) is the peak intensity of the diffraction peak of the 004 crystal plane of the 2H phase in the X-ray diffraction spectrum of the carbon material. The carbon material according to the present application can endow a secondary battery with high initial Coulomb efficiency, good cycle performance, and kinetic performance.

Description

Technical Field

[0001] This application belongs to the technical field of batteries, and specifically relates to a carbon material, a method for manufacturing the same, a secondary battery including the same, and a power consumption device.

Background Art

[0002] In recent years, secondary batteries have been widely used in many fields such as energy storage power systems such as hydraulic power, thermal power, wind power, and solar power plants, and electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. As the application range of secondary batteries becomes increasingly wide, the requirements for the performance of secondary batteries are also increasing. For example, secondary batteries are required to have various performances such as energy density, kinetic performance, and service life. The negative electrode active material is an important component of a secondary battery and affects the performance of the secondary battery. Currently, the negative electrode active material mainly contains graphite, but the problems faced in the prior art are that it is difficult for high-capacity graphite to have a high initial Coulomb efficiency, and it is also difficult for a secondary battery to have good cycle performance and kinetic performance at the same time.

Summary of the Invention

[0003] An object of this application is to provide a carbon material, a method for manufacturing the same, a secondary battery including the same, and a power consumption device, which enable a secondary battery to have a high initial Coulomb efficiency, good cycle performance, and kinetic performance.

[0004] A first aspect of this application provides a carbon material including a pore structure, where the carbon material has a coexistence of 3R phase and 2H phase, and 0 < I 3R(101) / I 2H(004) ≤ 0.100 is satisfied, where I 3R(101) is the peak intensity of the diffraction peak of the 101 crystal plane of the 3R phase in the X-ray diffraction spectrum of the carbon material, and I 2H(004) is the peak intensity of the diffraction peak of the 004 crystal plane of the 2H phase in the X-ray diffraction spectrum of the carbon material.

[0005] In the research process, the inventors found that 3R-phase crystalline carbon and 2H-phase crystalline carbon coexist in the carbon material, and the ratio of the peak intensity of the diffraction peak of the 3R-phase 101 crystal plane to the peak intensity of the diffraction peak of the 2H-phase 004 crystal plane satisfies 0 < I 3R(101) / I 2H(004) ≤ 0.100. In this case, there are many active sites on the surface of the carbon material particles, which can accelerate the transport of active ions, and the surface stability of the carbon material particles is also high. As a result, side reactions on the surface can be effectively reduced, and the consumption of active ions can be reduced. The carbon material according to the present application includes a pore structure, and the pore structure can ensure an expansion space required for the volume change of the carbon material particles, thereby reducing the risk of generating new interfaces due to the crushing of the carbon material particles, reducing the occurrence of side reactions, and reducing the consumption of active ions. Therefore, the carbon material according to the present application can have high ion transport performance, high surface stability, and low volume change, and further, the secondary battery using the same can have high initial Coulomb efficiency, good cycle performance, and kinetic performance.

[0006] In any embodiment of the present application, 0.005 ≤ I 3R(101) / I 2H(004) ≤ 0.100, and optionally, 0.008 ≤ I 3R(101) / I 2H(004) ≤ 0.065. When the I 3R(101) / I 2H(004) of the carbon material is further within the above range, the secondary battery can more preferably have high initial Coulomb efficiency, good cycle performance, and kinetic performance.

[0007] In any embodiment of the present application, the X-ray diffraction spectrum of the carbon material does not have a peak position of the 3R-phase 012 crystal plane. In this case, since the carbon material particles have few internal defects, the consumption of active ions can be further reduced, and the initial Coulomb efficiency and cycle performance of the secondary battery can be improved.

[0008] In any embodiment of the present application, the carbon material has a pore area of 0.15 μm 2comprising one or more pore structures as described above, and optionally having a pore area of 0.15 μm 2 ~2.0 μm 2 One or more pore structures are included. In further research, the inventors found that when the carbon material includes a pore structure having the above pore area, the pore structure can ensure the expansion space required for the volume change of the carbon material particles, so that the risk of generating a new interface due to the crushing of the carbon material particles can be further reduced, and further, the occurrence of side reactions can be reduced, the irreversible capacity loss of the secondary battery can be reduced, and the cycle performance of the secondary battery can be improved.

[0009] In any embodiment of the present application, the carbon material includes an external region and an internal region located inside the external region. The external region is a region formed by extending a distance of 0.25L from the particle surface of the carbon material to the particle interior, where L refers to the length of the short axis of the carbon material particle. The total pore area of the external region is denoted as S 1 and the total pore area of the internal region is denoted as S 2 and, S 2 > S 1 is satisfied. When the carbon material further satisfies S 2 > S 1 it can effectively reduce the irreversible capacity loss of the secondary battery, improve the capacity performance of the secondary battery, and preferably equip the secondary battery with high initial Coulomb efficiency, good cycle performance, and kinetic performance.

[0010] In any embodiment of the present application, 1.5 ≤ S 2 / S 1 ≤ 420, and optionally 2 ≤ S 2 / S 1 ≤ 300. When S 2 / S 1 is within the above range, the secondary battery can preferably have high initial Coulomb efficiency, good cycle performance, and kinetic performance.

[0011] In any embodiment of the present application, 0.01 μm 2 ≤ S 1 ≤ 5.0 μm 2 is satisfied, and optionally, 0.02 μm2 ≤ S 1 ≤ 4.5 μm 2 is satisfied. In this case, the carbon material particles have a more stable structure, and the electrolyte can be prevented from entering the pore structure inside the carbon material particles as much as possible, reducing the occurrence of side reactions and the consumption of active ions due to the formation of the SEI film inside the carbon material particles, while not affecting the transport performance of active ions and electrons.

[0012] In any embodiment of the present application, 2.5 μm 2 ≤ S 2 ≤ 25.0 μm 2 is satisfied, and optionally, 3.0 μm 2 ≤ S 2 ≤ 22.5 μm 2 is satisfied. In this case, a sufficient and stable expansion space is ensured against the volume change of the carbon material particles, reducing the risk of the generation of new interfaces due to the crushing of the carbon material particles, decreasing the occurrence of side reactions on the surface of the new interfaces, and reducing the consumption of active ions due to the formation of the SEI film on the surface of the new interfaces, while improving the capacity and initial coulombic efficiency of the carbon material.

[0013] In any embodiment of the present application, L ≥ 4 μm, and optionally, 4 μm ≤ L ≤ 20 μm.

[0014] In any embodiment of the present application, the area of the pore structure in the external region of the carbon material is less than 0.15 μm 2 and optionally, 0.10 μm 2 or less. By controlling the area of the pore structure in the external region of the carbon material to be within the above range, the external region of the carbon material can be made into a dense structure, effectively improving the structural stability of the carbon material, preventing the electrolyte from entering the pore structure inside the carbon material particles as much as possible, and effectively improving the cycle performance of the secondary battery.

[0015] In any embodiment of the present application, the internal region of the carbon material includes one or more pore structures with an area of 0.15 μm 2 or more, and optionally, an area of 0.15 μm2 ~2.0 μm 2 One or more pore structures are included. By including pore structures of the above size in the internal region of the carbon material, a sufficiently stable expansion space for the volume change of the carbon material particles is ensured, while reducing the risk of crushing of the carbon material particles, improving the compression density of the carbon material, and improving the energy density of the secondary battery.

[0016] In any embodiment of the present application, the specific surface area of the carbon material is 0.6 m 2 / g to 2.5 m 2 / g, and optionally 0.8 m 2 / g to 2.4 m 2 / g. Since the carbon material of the present application has a low specific surface area and low surface activity, it can reduce the consumption of active ions due to the formation of the SEI film, and improve the initial Coulomb efficiency of the carbon material and the cycle performance of the secondary battery.

[0017] In any embodiment of the present application, the volume distribution particle size Dv50 of the carbon material is 6 μm to 30 μm, and optionally 8 μm to 25 μm.

[0018] When the volume distribution particle size Dv50 of the carbon material is within the above range, the cycle performance and kinetic performance of the secondary battery can be further improved to improve the transport performance of active ions and electrons.

[0019] In any embodiment of the present application, the particle size distribution (Dv90 - Dv10) / Dv50 of the carbon material is 0.90 to 1.50, and optionally 0.90 to 1.45. Thereby, in order to improve the compression density of the carbon material, the energy density of the secondary battery can be further improved.

[0020] In any embodiment of the present application, the graphitization degree of the carbon material is 93% to 98.5%, and optionally 94% to 98%. When the graphitization degree of the carbon material is within the above range, it is advantageous for the secondary battery to have high energy density, good cycle performance and kinetic performance.

[0021] In any embodiment of the present application, the topography of the carbon material includes one or more of massive, spherical, and substantially spherical shapes.

[0022] In any embodiment of the present application, the tap density of the carbon material is 0.8 g / cm 3 ~1.20 g / cm 3 and optionally 0.85 g / cm 3 ~1.18 g / cm 3 When the tap density of the carbon material is within the above range, the compression density of the negative electrode sheet can be improved, the energy density of the secondary battery can be improved, the active ion and electron transport performance can be improved, and the cycle performance and / or kinetic performance of the secondary battery can be improved.

[0023] In any embodiment of the present application, the compression density of the powder of the carbon material at a pressure of 5000 kg is 1.85 g / cm 3 ~2.10 g / cm 3 and optionally 1.85 g / cm 3 ~2.08 g / cm 3 When the compression density of the powder of the carbon material is within the above range, the compression density of the negative electrode sheet can be improved, the energy density of the secondary battery can be further improved, the active ion and electron transport performance can be improved, and the cycle performance and / or kinetic performance of the secondary battery can be improved.

[0024] In any embodiment of the present application, the gram capacity (capacity per gram) of the carbon material is 350 mAh / g to 370 mAh / g, and optionally 355 mAh / g to 370 mAh / g. When the gram capacity of the carbon material is within the above range, the energy density of the secondary battery can be improved.

[0025] The second aspect of the present application is a step 1 of providing a raw material having a plurality of pore structures, uniformly mixing the raw material and a filling material at a predetermined ratio, and then heating at a first temperature T 1 for a first time t 1Step 2 of obtaining an intermediate by heat preservation, and heat preserving the obtained intermediate at a second temperature T 2 for a second time t 2 to obtain a carbon material in Step 3, and a method for manufacturing a carbon material is provided, wherein the carbon material includes a pore structure, the carbon material has a 3R phase and a 2H phase coexisting, and 0 < I 3R(101) / I 2H(004) ≤ 0.100 is satisfied, where I 3R(101) is the peak intensity of the diffraction peak of the 101 crystal plane of the 3R phase in the X-ray diffraction spectrum of the carbon material, and I 2H(004) is the peak intensity of the diffraction peak of the 004 crystal plane of the 2H phase in the X-ray diffraction spectrum of the carbon material.

[0026] In any embodiment of the present application, the raw material includes natural graphite, and optionally, the natural graphite includes one or more of flake graphite, natural spherical graphite, and microcrystalline graphite.

[0027] In any embodiment of the present application, the volume distribution particle size Dv50 of the raw material is 6 μm to 30 μm, and optionally 8 μm to 25 μm.

[0028] In any embodiment of the present application, the OI value of the raw material is 4 or more, and optionally 4 to 15.

[0029] In any embodiment of the present application, the volume distribution particle size Dv50 of the filling material is 6 μm or less, and optionally 1 μm to 5 μm.

[0030] In any embodiment of the present application, the softening point temperature of the filling material is 105 °C to 190 °C, and optionally 110 °C to 165 °C.

[0031] In any embodiment of the present application, the coking value of the filling material is 20% to 48%, and optionally 25% to 40%.

[0032] In any embodiment of the present application, the filling material includes one or more of coal pitch, petroleum pitch, polymer compounds, and resins, and optionally includes petroleum pitch.

[0033] In any embodiment of the present application, the mass ratio of the filling material to the raw material is (10~40):100, and optionally, (15~30):100.

[0034] By adjusting one or more parameters such as the type, softening point, coking value, addition amount, etc. of the filling material within the above range, it is advantageous to adjust I 3R(101) / I 2H(004) to be within an appropriate range, and it is also advantageous to adjust the size and / or number of pores in the external and internal regions of the carbon material to be within an appropriate range. Further, after the filling material is thermally melted, the viscosity does not increase, good fluidity is maintained, and it is difficult to adhere to the raw material particles, which can reduce the aggregation of the raw material particles in the subsequent manufacturing process. Thereby, problems such as an increase in surface defects of carbon material particles and an increase in side reactions caused by the need to increase the depolymerization process can be reduced.

[0035] In any embodiment of the present application, after uniformly mixing the raw material and the filling material at a predetermined ratio, the temperature-raising process of raising the temperature to the first temperature T 1 is a stepwise temperature-raising process, and optionally includes a first temperature-raising process and a second temperature-raising process.

[0036] In any embodiment of the present application, the first temperature-raising process raises the temperature to 200°C~300°C and holds the temperature for 1h~3h at this temperature.

[0037] In any embodiment of the present application, the second temperature-raising process raises the temperature to the first temperature T 1 and holds the temperature for the first time t 1 at this temperature.

[0038] In any embodiment of the present application, the first temperature T 1 is 700°C to 1100°C, and optionally 850 to 1100°C.

[0039] In any embodiment of the present application, the first time t 1 is 1 h to 5 h, and optionally 2 h to 4 h.

[0040] By adjusting one or more of the heating rate, the first temperature, the first time, the heating process, etc. so that they are within the above ranges, it is advantageous to adjust the size and / or the number of pores in the external region and the internal region of the carbon material to be within an appropriate range.

[0041] In any embodiment of the present application, the second temperature T 2 is 1850°C to 2650°C, and optionally 2100°C to 2480°C.

[0042] In any embodiment of the present application, the second time t 2 is 1.5 h to 6 h, and optionally 2 h to 5 h.

[0043] When the second temperature and / or the second time are within the above ranges, it is advantageous to adjust I 3R(101) / I 2H(004) to be within an appropriate range, which is also advantageous for improving the cycle performance and / or the kinetic performance of the secondary battery.

[0044] A third aspect of the present application provides a secondary battery including a negative electrode sheet containing the carbon material of the first aspect of the present application or the carbon material produced by the method of the second aspect of the present application.

[0045] A fourth aspect of the present application provides a power consumption device including the secondary battery of the third aspect of the present application.

[0046] The surface defects and / or bulk-phase defects of the carbon material produced in this application are all few, and the carbon material can have high ion transport performance, high surface stability and low volume change. Therefore, the secondary battery using it can also have high initial Coulomb efficiency, good cycle performance and kinetic performance. Since the power consumption device of this application includes the secondary battery according to this application, it has at least the same advantages as the secondary battery.

Brief Description of Drawings

[0047] To more clearly explain the technical solutions of the embodiments of this application, the drawings required for the embodiments of this application are briefly described below. It is clear that the drawings described below are only some embodiments of this application. A person skilled in the art can obtain other drawings based on these drawings without creative labor. In the drawings, the drawings are not necessarily drawn to actual size.

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Embodiments for Carrying Out the Invention

[0048] Hereinafter, embodiments of the carbon material, its manufacturing method, secondary battery, and power consumption device specifically disclosed in this application will be described in detail with reference to the drawings as appropriate. However, detailed descriptions that are not necessary may be omitted. For example, detailed descriptions of well-known matters and redundant descriptions of substantially the same configurations may be omitted. This is to avoid making the following description unnecessarily redundant and to facilitate the understanding of those skilled in the art. Note that the accompanying drawings and the following description are provided for those skilled in the art to fully understand this application and are not intended to limit the subject matter described in the claims.

[0049] In this application, the "range" disclosed is defined in the form of a lower limit and an upper limit. A predetermined range is defined by selecting one lower limit and one upper limit, and the selected lower limit and upper limit limit the boundaries of a specific range. The range thus limited may be a range including or not including the end values, and may be arbitrarily combined, that is, any lower limit may be combined with any upper limit to form a range. For example, when ranges of 60 to 120 and 80 to 110 are given for a specific parameter, ranges of 60 to 110 and 80 to 120 are also understood to be expected. Also, when the minimum range values 1 and 2, and the maximum range values 3, 4, and 5 are given, ranges of 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5 may all be expected. In this application, unless otherwise explained, the numerical range "a~b" is an abbreviation indicating any combination of real numbers between a and b, and both a and b are real numbers. For example, the numerical range "0~5" indicates all real numbers between "0~5" in this specification, and "0~5" is an abbreviation for combinations of these numerical values. Also, when a certain parameter is expressed as an integer of 2 or more (≧2), it corresponds to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0050] Unless otherwise specified, all embodiments and selectable embodiments of this application may be combined with each other to form a new technical solution. Also, such a technical solution is considered to be included in the disclosure content of this application.

[0051] Unless otherwise specified, all technical features of this application and selectable technical features may be combined with each other to form a new technical solution. Moreover, such a technical solution is considered to be included in the disclosure content of this application.

[0052] Unless otherwise specified, all steps of this application may be performed in sequence or randomly, but it is preferred to be performed in sequence. For example, the fact that the above method includes steps (a) and (b) means that the above method may include steps (a) and (b) performed in sequence, or steps (b) and (a) performed in sequence. For example, when it is mentioned that the above method may further include step (c), it means that step (c) may be added to the above method in any order. For example, the above method may include steps (a), (b) and (c), may include steps (a), (c) and (b), may include steps (c), (a) and (b), etc.

[0053] Unless otherwise specified, the terms "comprise" and "include" described in this application are meant to be open-ended and may also be closed-ended. For example, the above "comprise" and "include" can represent further "comprising" or "including" other components not listed, or "comprising" or "including" only the components listed.

[0054] Unless otherwise specified, in this application, the term "or" is inclusive. For example, the phrase "A or B" represents "A, B, or both A and B". More specifically, any of the following conditions is satisfied. A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), or both A and B are true (or exist).

[0055] Unless otherwise specified, the terms used in this application have the well-known meanings commonly understood by those skilled in the art.

[0056] Unless otherwise specified, the numerical values of each parameter mentioned in this application can be measured by various test methods commonly used in this field. For example, they can be measured according to the test methods according to this application.

[0057] Unless otherwise specified, in this application, the term "active ion" refers to an ion that can be inserted and desorbed reciprocally between the positive electrode and the negative electrode of a secondary battery, including but not limited to lithium ions.

[0058] In this application, the terms "a plurality" and "a plurality of types" mean two or more.

[0059] Depending on the manufacturing process or source, graphite can be divided into artificial graphite and natural graphite. The manufacture of artificial graphite generally requires a high-temperature graphitization treatment process, which is energy-consuming and costly, thereby increasing the cost of artificial graphite. Since natural graphite is derived from nature, it has the advantage of being inexpensive. In addition, natural graphite also has the advantages of high capacity and high compression density.

[0060] Natural graphite mainly includes flake graphite, natural spherical graphite and microcrystalline graphite. Usually, different from artificial graphite, natural graphite has a very large number of voids and defects inside and outside its particles. In the initial charging process of a secondary battery, many side reactions occur between the electrolyte and the particle surface and the pores inside the particles, resulting in a high irreversible capacity loss in the first cycle of the secondary battery, a low initial Coulomb efficiency, and poor cycle performance. In particular, flake graphite and natural spherical graphite have high crystallinity and high graphitization degree, and their microstructure is often a layered structure. Such a structure is prone to cause crushing of the layered structure of graphite and particle crushing due to the large volume change occurring during the desorption and insertion process of active ions in natural graphite. After the particles are crushed, the exposed fresh surface continues to react with the electrolyte, further increasing the irreversible capacity loss of the secondary battery. In addition, natural graphite has high anisotropy and slow diffusion of active ions, so its kinetic performance is poor.

[0061] Currently, the performance of natural graphite is mainly improved by coating treatment on the particle surface and / or filling treatment inside the particles.

[0062] The coating treatment on the particle surface mainly involves uniformly mixing natural graphite and a coating agent (such as pitch, polymer compound, etc.), and then performing heat treatment to coat a layer of amorphous carbon on the surface of natural graphite particles to slightly repair the defects on the particle surface. However, the inventors of the present application found in the research process that the amorphous carbon layer coated on the surface reduces the gram capacity and / or compression density of natural graphite, affects the energy density of the secondary battery, and the amorphous carbon layer coated on the surface cannot effectively prevent the electrolyte from invading the pore structure inside the particles, thereby having limited improvement effects on the initial Coulomb efficiency and cycle performance of the secondary battery.

[0063] The filling treatment inside the particles mainly involves mixing natural graphite and a filler (such as pitch, polymer compound, etc.), and filling the filler into the voids inside the particles by means such as a predetermined pressure, vacuum pumping, temperature increase, etc., to obtain natural graphite without voids inside the particles. However, the inventors of the present application found in the research process that the carbon filled in a large amount inside the particles reduces both the gram capacity and compression density of natural graphite, affects the energy density of the secondary battery, and since all the voids inside the natural graphite particles are filled with carbon, the volume change of natural graphite occurring during the desorption and insertion process of active ions is large, the particles are more likely to be crushed, the SEI film on the particle surface repeatedly breaks and reconstitutes, further increasing the consumption of active ions, increasing the capacity loss of the secondary battery, and shortening the service life of the secondary battery. In the prior art, continuously coating a layer of amorphous carbon on the surface of natural graphite without voids inside the particles further reduces the gram capacity and / or compression density of natural graphite, and at that time, there are still many defects on the particle surface, so the service life of the secondary battery cannot be effectively improved.

[0064] Therefore, after modifying natural graphite by the coating treatment on the particle surface and / or the filling treatment inside the particle, the irreversible capacity loss of the secondary battery can be reduced to a certain extent, and the initial Coulomb efficiency of the secondary battery can be improved. However, there is a limit to the improvement of the initial Coulomb efficiency of the secondary battery, the energy density of the secondary battery is also lost, and it is difficult to endow the secondary battery with both good cycle performance and kinetic performance.

[0065] Therefore, through a lot of research, the inventors of the present application propose a novel carbon material that can have high initial Coulomb efficiency, good cycle performance and kinetic performance in a secondary battery. Carbon material

[0066] The first aspect of the embodiment of the present application provides a carbon material including a pore structure. The carbon material has the coexistence of 3R phase and 2H phase, and 0 < I 3R(101) / I 2H(004) ≤ 0.100 is satisfied, where I 3R(101) is the peak intensity of the diffraction peak of the 101 crystal plane of the 3R phase in the X-ray diffraction spectrum of the carbon material, and I 2H(004) is the peak intensity of the diffraction peak of the 004 crystal plane of the 2H phase in the X-ray diffraction spectrum of the carbon material.

[0067] In the present application, the peak intensity of the diffraction peak of the 101 crystal plane of the 3R phase and the peak intensity of the diffraction peak of the 004 crystal plane of the 2H phase are represented by the integrated area of the corresponding diffraction peak.

[0068] The crystalline carbon of the 3R (Rhombohedral) phase is rhombohedral crystalline carbon and has a stacking structure of ABCABC..., and the crystalline carbon of the 2H (Hexagonal) phase is hexagonal crystalline carbon and has a stacking structure of ABAB.... In the research process, the inventors found that the 3R-phase crystalline carbon and the 2H-phase crystalline carbon coexist in the carbon material, and the ratio of the peak intensity of the diffraction peak of the 101 crystal plane of the 3R phase to the peak intensity of the diffraction peak of the 004 crystal plane of the 2H phase is 0 < I 3R(101) / I 2H(004)When it satisfies ≦0.100, there are many active sites on the surface of the carbon material particles, which can accelerate the transport of active ions, and the surface stability of the carbon material particles is also high. Thus, it was discovered that the surface side reactions can be effectively reduced and the consumption of active ions can be decreased.

[0069] The carbon material according to the present application includes a pore structure. In the present application, "the carbon material includes a pore structure" means that the carbon material has a pore structure that can be directly observed from a cross-sectional image (for example, a scanning electron microscope image with a particle magnification of 1000 times), that is, the pore structure in the raw material for manufacturing the carbon material is not completely filled. The pore structure in the carbon material can ensure the expansion space required for the volume change of the carbon material particles, so as to reduce the risk of generating a new interface due to the crushing of the carbon material particles, reduce the occurrence of side reactions, and reduce the consumption of active ions.

[0070] Therefore, the carbon material according to the present application can have high ion transport performance, high surface stability and low volume change, and further enable the secondary battery using the same to have high initial Coulomb efficiency, good cycle performance and kinetic performance.

[0071] In some embodiments, 0.005 ≦ I 3R(101) / I 2H(004) ≦0.100, and optionally, 0.006 ≦ I 3R(101) / I 2H(004) ≦0.080, 0.007 ≦ I 3R(101) / I 2H(004) ≦0.072, 0.008 ≦ I 3R(101) / I 2H(004) ≦0.065, 0.010 ≦ I 3R(101) / I 2H(004) ≦0.060. The inventors have intensively studied and found that when I 3R(101) / I 2H(004) of the carbon material is further within the above range, the secondary battery can better have high initial Coulomb efficiency, good cycle performance and kinetic performance.

[0072] In some embodiments, the X-ray diffraction spectrum of the carbon material does not have a peak position of the crystal plane of 3R phase 012. The carbon material of the present application does not have the crystal plane of 3R phase 012, and at this time, since the carbon material particles have few internal defects, the consumption of active ions can be further reduced, and the initial Coulomb efficiency and cycle performance of the secondary battery can be improved.

[0073] In the present application, in the X-ray diffraction spectrum of the carbon material, the 2θ of the diffraction peak of the 3R phase 101 crystal plane is in the range of 43° to 44°, the 2θ of the diffraction peak of the 2H phase 004 crystal plane is in the range of 53° to 55°, and the 2θ of the diffraction peak of the 3R phase 012 crystal plane is in the range of 46° to 47°.

[0074] In some embodiments, the carbon material includes one or more pore structures with a pore area of 0.15 μm 2 or more, and optionally, includes one or more pore structures with a pore area of 0.15 μm 2 to 2.0 μm 2 The inventors further found in further research that when the carbon material includes a pore structure having the above pore area, the pore structure can ensure the expansion space required for the volume change of the carbon material particles, so that the risk of generating a new interface due to the crushing of the carbon material particles can be further reduced, and further the occurrence of side reactions can be reduced, the irreversible capacity loss of the secondary battery can be reduced, and the cycle performance of the secondary battery can be improved.

[0075] In some embodiments, the carbon material includes an external region and an internal region located inside the external region. The external region refers to a region formed by extending 0.25L from the particle surface of the carbon material to the inside of the particle, where L refers to the length of the short axis of the carbon material particle. The total pore area of the external region is denoted as S 1 and the total pore area of the internal region is denoted as S 2 and, S 2 > S 1 is true.

[0076] The inventors further found in further research that when the carbon material has S 2 > S1 When further satisfying the following conditions, it was found that the carbon material particles have the characteristics that the number of pores in the internal region is large and / or the pore size is large, and the number of pores in the external region is small and / or the pore size is small. Since the large number of pores and / or large pore size in the internal region of the carbon material can ensure the expansion space required for the volume change of the carbon material particles, the risk of generating a new interface due to the crushing of the carbon material particles can be reduced, the occurrence of side reactions can be reduced, the irreversible capacity loss of the secondary battery can be reduced, and the cycle performance and kinetic performance of the secondary battery can be improved. Since the small number of pores and / or small pore size in the external region of the carbon material enable the carbon material particles to have a more stable structure and can avoid the electrolyte from penetrating into the pore structure inside the carbon material particles as much as possible, the occurrence of side reactions can be reduced, the consumption of active ions due to the formation of the SEI film inside the particles can be reduced, the initial Coulomb efficiency of the carbon material can be further improved, and the cycle performance of the secondary battery can be further improved.

[0077] Therefore, when the carbon material satisfies S 2 >S 1 further, the irreversible capacity loss of the secondary battery can be effectively reduced, the performance of exerting the capacity of the secondary battery can be improved, and the secondary battery can be more preferably provided with a high initial Coulomb efficiency, good cycle performance and kinetic performance.

[0078] In some embodiments, 1.5 ≦ S 2 / S 1 ≦ 420, 2 ≦ S 2 / S 1 ≦ 300, 2.2 ≦ S 2 / S 1 ≦ 250, 2.5 ≦ S 2 / S 1 ≦ 150, 2.8 ≦ S 2 / S 1 ≦ 100. The inventors further found in further research that when S 2 / S 1 is within the above range, the secondary battery can be more preferably provided with a high initial Coulomb efficiency, good cycle performance and kinetic performance.

[0079] In some embodiments, 0.01 μm 2 ≤ S 1 ≤ 5.0 μm 2 and optionally, 0.02 μm 2 ≤ S 1 ≤ 4.5 μm 2 , 0.04 μm 2 ≤ S 1 ≤ 4.5 μm 2 , 0.08 μm 2 ≤ S 1 ≤ 4.5 μm 2 and 0.1 μm 2 ≤ S 1 ≤ 4.5 μm 2 and 0.1 μm 2 ≤ S 1 ≤ 4.0 μm 2 and 0.1 μm 2 ≤ S 1 ≤ 3.5 μm 2 is satisfied. When the total pore area of the external region of the carbon material is within the above range, the carbon material particles have a more stable structure, and the electrolyte can be prevented from entering the pore structure inside the carbon material particles as much as possible, reducing the occurrence of side reactions and reducing the consumption of active ions due to the formation of the SEI film inside the carbon material particles, while not affecting the transport performance of active ions and electrons.

[0080] In some embodiments, 2.5 μm 2 ≤ S 2 ≤ 25.0 μm 2 and optionally, 3.0 μm 2 ≤ S 2 ≤ 22.5 μm 2 and 3.0 μm 2 ≤ S 2 ≤ 20.0 μm 2 and 3.0 μm 2 ≤ S 2 ≤ 17.5 μm 2 and 3.5 μm 2 ≤ S 2 ≤ 15.0 μm 2When the total pore area of the internal region of the carbon material is within the above range, a sufficient and stable expansion space can be ensured for the volume change of the carbon material particles, reducing the risk of the generation of new interfaces due to the crushing of the carbon material particles, decreasing the occurrence of side reactions on the surface of the new interfaces, reducing the consumption of active ions due to the formation of the SEI film on the surface of the new interfaces, while improving the capacity and initial Coulomb efficiency of the carbon material.

[0081] In the present application, the total pore area S of the external region of the carbon material 1 and the total pore area S of the internal region 2 can be obtained by measuring based on the cross-sectional image of the carbon material.

[0082] In the present application, the cross-sectional image of the carbon material includes the cross-sectional image passing through the center of the carbon material particles. The "center of the particle" means the range within a radius extended by 0.1 μm from the geometric center of the particle towards the particle surface.

[0083] In the present application, the length of the short axis of the particle refers to the minimum value when the line connecting two points on the particle surface passes through the geometric center of the particle.

[0084] Figure 1 is a schematic diagram of the cross-sectional image of the particles of the carbon material 100 of the present application, and the cross-sectional image passes through the center of the particles of the carbon material 100. As shown in Figure 1, L represents the length of the short axis of the particles of the carbon material 100, and the region formed by extending a distance of 0.25L from the particle surface of the carbon material 100 into the particle interior is the external region 101, and the region inside the external region 101 is the internal region 102.

[0085] After manufacturing the cross-section of the carbon material using a cross-section polishing device (for example, the IB-09010 CP type argon ion cross-section polishing device of JEOL Ltd., Japan), referring to JY / T010-1996, scanning the cross-section of the carbon material using a scanning electron microscope (for example, the Sigma 300 type scanning electron microscope of ZEISS, Germany), and finally calculating the total pore area S of the external region of the carbon material 1 and the total pore area S of the internal region 2 using image processing software (for example, AVIZO).

[0086] In some embodiments, L≥4 μm, and optionally, 4 μm≤L≤20 μm, 6 μm≤L≤20 μm, 8 μm≤L≤20 μm, 8 μm≤L≤18 μm, 8 μm≤L≤16 μm.

[0087] In some embodiments, the area of the pore structure in the outer region of the carbon material is 0.15 μm 2 less than, and optionally 0.10 μm 2 or less. The inventors have further discovered in research that by controlling the area of the pore structure in the outer region of the carbon material to be within the above range, the outer region of the carbon material can have a dense structure, effectively improving the structural stability of the carbon material, avoiding the intrusion of the electrolyte into the pore structure inside the carbon material particles as much as possible, and further effectively improving the cycle performance of the secondary battery. Of course, this application does not intend to limit all the areas of the pore structures in the outer region of the carbon material to be 0.15 μm 2 or less. For example, it can be controlled such that 95% or more, and optionally 99% or more, of the pore structure area is 0.15 μm 2 or less, and optionally 0.10 μm 2 or less.

[0088] In some embodiments, the inner region of the carbon material includes one or more pore structures with an area of 0.15 μm 2 or more, and optionally includes one or more pore structures with an area of 0.15 μm 2 to 2.0 μm 2 The inventors have further discovered in research that by including pore structures of the above size in the inner region of the carbon material, a sufficiently stable expansion space can be ensured for the volume change of the carbon material particles, reducing the risk of crushing of the carbon material particles while improving the compression density of the carbon material and the energy density of the secondary battery.

[0089] In some embodiments, the interlayer spacing of the outer region of the carbon material is d 1and the interlayer spacing of the internal region of the carbon material is d 2 and the carbon material has d 1 ≧d 2 satisfies, and optionally, d 1 >d 2 .

[0090] In the carbon material of the present application, the interlayer spacing of the external region of the carbon material is large, which is advantageous for the rapid insertion and desorption of active ions, and thereby, the kinetic performance of the secondary battery can be further improved. The interlayer spacing of the internal region of the carbon material is small, which is advantageous for improving the gram capacity and compression density of the carbon material, and the energy density of the secondary battery can be further improved.

[0091] In some embodiments, d 1 is 0.33565 nm to 0.33600 nm.

[0092] In some embodiments, d 2 is 0.33553 nm to 0.33589 nm.

[0093] The interlayer distances of different regions of the carbon material can be tested by devices and methods well-known in the art. For example, it can be tested using a High Resolution Transmission Electron Microscope (HRTEM). The test device can employ a scanning transmission electron microscope of Thermo Fisher's Spectra S / TEM.

[0094] In some embodiments, the graphitization degree of the carbon material is 93% to 98.5%, and optionally, 94% to 98%. When the graphitization degree of the carbon material is within the above range, it is advantageous for the secondary battery to have high energy density, good cycle performance, and kinetic performance.

[0095] The graphitization degree of the carbon material is a meaning well-known in the art and can be tested by devices and methods well-known in the art. For example, it can be tested using an X-ray diffractometer (Bruker D8 Discover). The test is based on JIS K0131-1996 and JB / T 4220-2011 to obtain the average interlayer spacing d of the (002) crystal plane in the crystal structure of the carbon material. 002 After obtaining it, the graphitization degree can be calculated based on the formula g = (0.344 - d 002 ) / (0.344 - 0.3354) × 100%. In the above formula, d 002 is the average interlayer spacing of the (002) crystal plane in the crystal structure of the carbon material, expressed in nanometers (nm).

[0096] In some embodiments, the topography of the carbon material includes one or more of massive, spherical, and substantially spherical. This is advantageous for improving the compression density of the negative electrode sheet and the energy density of the secondary battery.

[0097] In some embodiments, the carbon material includes primary particles. Optionally, the proportion of the number of the primary particles in the carbon material is 50% or more, for example, 55% - 95%, 60% - 100%, 65% - 90%, 65% - 80%, 70% - 100%, 75% - 90%, 80% - 100%, 90% - 100%, or 95% - 100%. The carbon material contains an appropriate proportion of primary particles, has high structural stability, can reduce the occurrence of side reactions, and can also improve the compression density of the negative electrode sheet and the energy density of the secondary battery.

[0098] In some embodiments, the carbon materials may all be primary particles, that is, the proportion of the number of the primary particles in the carbon material is 100%.

[0099] Both the primary particles and the secondary particles have the meanings well-known in this field. The primary particles refer to non-aggregated particles. The secondary particles refer to aggregated particles in which two or more primary particles are aggregated. The primary particles and the secondary particles can be distinguished using a scanning electron microscope (SEM) drawing.

[0100] In this application, the proportion of the number of primary particles in the carbon material can be tested according to the following method. Arbitrarily take one test sample in the negative electrode film layer, arbitrarily select a plurality of test regions in the test sample, use a scanning electron microscope to obtain images of the plurality of test regions, and count the proportion of the number of carbon material particles in the topography of the primary particles in each image to the total number of carbon material particles. The average value of the plurality of statistical results is the proportion of the number of primary particles in the carbon material.

[0101] In some embodiments, the specific surface area of the carbon material is 0.6 m 2 / g to 2.5 m 2 / g, and optionally, 0.8 m 2 / g to 2.4 m 2 / g. Due to the low specific surface area and low surface activity of the carbon material in this application, the consumption of active ions due to the formation of the SEI film can be reduced, and the initial Coulomb efficiency of the carbon material and the cycle performance of the secondary battery can be improved.

[0102] The specific surface area of the carbon material has the meaning well-known in this field and can be measured by equipment and methods well-known in this field. For example, referring to GB / T 19587-2017, it can be tested by the nitrogen gas adsorption specific surface area analysis test method and calculated by the BET (Brunauer Emmett Teller) method. Here, the nitrogen gas adsorption specific surface area analysis test can be performed by a Tri-Star 3020 type specific surface area pore size analyzer of Micromeritics, USA.

[0103] In some embodiments, the volume distribution particle size Dv50 of the carbon material is 6 μm to 30 μm, and optionally, 8 μm to 25 μm.

[0104] When the volume distribution particle size Dv50 of the carbon material is within the above range, the cycle performance and kinetic performance of the secondary battery can be further improved in order to improve the transport performance of active ions and electrons.

[0105] In some embodiments, the particle size distribution (Dv90 - Dv10) / Dv50 of the carbon material is 0.90 to 1.50, and optionally 0.90 to 1.45. When the particle size distribution (Dv90 - Dv10) / Dv50 of the carbon material is within the above range, the compression density of the carbon material can be improved, and the energy density of the secondary battery can be further improved.

[0106] The volume distribution particle sizes Dv10, Dv50, and Dv90 of the carbon material have the meanings well-known in the art, and respectively indicate the particle sizes corresponding when the cumulative volume distribution percentage of the material reaches 10%, 50%, and 90%, and can be measured by equipment and methods well-known in the art. For example, referring to the laser diffraction method for particle size distribution in GB / T 19077 - 2016, it can be easily measured using a laser particle size analyzer. The test equipment may be a Mastersizer 3000 type laser particle size analyzer from Malvern Instruments, UK.

[0107] In some embodiments, the tap density of the carbon material is 0.8 g / cm 3 ~1.20 g / cm 3 and optionally 0.85 g / cm 3 ~1.18 g / cm 3 When the tap density of the carbon material is within the above range, the compression density of the negative electrode sheet can be improved, the energy density of the secondary battery can be improved, the transport performance of active ions and electrons can be improved, and the cycle performance and / or kinetic performance of the secondary battery can be improved.

[0108] The tap density of the carbon material has the meaning well-known in the art and can be measured by equipment and methods well-known in the art. For example, referring to GB / T 5162 - 2006, it can be measured using a powder tap density tester. The test equipment can adopt BT - 301 from Dandong BET.

[0109] In some embodiments, the compression density of the powder of the carbon material at a pressure of 5000 kg is 1.85 g / cm 3 ~2.10 g / cm 3 and optionally 1.85 g / cm 3 ~2.08 g / cm 3 . When the compression density of the powder of the carbon material is within the above range, the compression density of the negative electrode sheet can be improved, the energy density of the secondary battery can be further improved, the active ion and electron transport performance can be improved, and the cycle performance and / or kinetic performance of the secondary battery can be improved.

[0110] The compression density of the powder of the carbon material is the meaning well-known in the art and can be measured by equipment and methods well-known in the art. For example, referring to GB / T 24533-2009, it can be measured by an electronic pressure tester (for example, an UTM7305 type electronic pressure tester). As an exemplary test method, 1 g of carbon material powder is weighed, put into a mold with a bottom area of 1.327 cm 2 , pressurized to 5000 kg, kept under pressure for 30 seconds, then the pressure is released, held for 10 s, and then recorded to obtain the powder compression density of the carbon material at a pressure of 5000 kg.

[0111] In some embodiments, the gram capacity of the carbon material is 350 mAh / g to 370 mAh / g, and optionally 355 mAh / g to 370 mAh / g. When the gram capacity of the carbon material is within the above range, the energy density of the secondary battery can be improved.

[0112] The gram capacity of the carbon material is a well-known meaning in this field and can be tested by well-known methods in this field. As an exemplary test method, a carbon material sample, styrene-butadiene rubber (SBR) as an adhesive, sodium carboxymethyl cellulose (CMC) as a thickener, and carbon black as a conductive agent are sufficiently stirred and mixed in deionized water, which is an appropriate amount of solvent, at a mass ratio of 96.2:1.8:1.2:0.8 to form a uniform negative electrode slurry. The negative electrode slurry is uniformly coated on the surface of a copper foil, which is a negative electrode current collector, and after drying in an oven, it is prepared. After mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) at a volume ratio of 1:1:1 to obtain an organic solvent, LiPF 6 is dissolved in the organic solvent to produce an electrolyte solution with a concentration of 1 mol / L. Then, a CR2430 coin cell is assembled in a glove box protected by argon gas with a metal lithium piece as the counter electrode and a polyethylene (PE) thin film as the separator. At 25 °C, first, the coin cell manufactured above is discharged to 0.005 V at a constant current of 0.15 mA, allowed to stand for 5 min, and then further discharged to 0.005 V at a constant current of 10 μA. The initial discharge capacity of the coin cell is recorded. Then, it is charged at a constant current of 0.3 mA to 2.0 V, and the charge capacity of the coin cell is recorded. The ratio of the charge capacity of the coin cell to the mass of the carbon material sample is the gram capacity of the carbon material. Manufacturing method

[0113] The second aspect of the embodiment of the present application provides a method for manufacturing a carbon material that can manufacture the carbon material of the first aspect of the embodiment of the present application.

[0114] The method for manufacturing the carbon material includes Step 1 of providing a raw material having a plurality of pore structures, uniformly mixing the raw material and a filling material at a predetermined ratio, and then maintaining the temperature at a first temperature T 1 for a first time t 1 to obtain an intermediate in Step 2, and heating the obtained intermediate at a second temperature T 2 for a second time t 2The process 3 of obtaining a carbon material by heat preservation, and the carbon material includes a pore structure. The carbon material includes a pore structure. In the carbon material, the 3R phase and the 2H phase coexist, and 0 < I 3R(101) / I 2H(004) ≤ 0.100 is satisfied, where I 3R(101) is the peak intensity of the diffraction peak of the 101 crystal plane of the 3R phase in the X-ray diffraction spectrum of the carbon material, and I 2H(004) is the peak intensity of the diffraction peak of the 004 crystal plane of the 2H phase in the X-ray diffraction spectrum of the carbon material.

[0115] In some embodiments, the raw material for manufacturing the carbon material includes natural graphite. Optionally, the natural graphite includes one or more of flake graphite, natural spherical graphite, and microcrystalline graphite, and more preferably includes natural spherical graphite.

[0116] In the present application, "natural spherical graphite" means spherical or substantially spherical natural graphite, and does not mean that all natural graphite particles are controlled to be ideal spheres. In some embodiments, flake graphite can be pretreated to obtain natural spherical graphite with a desired particle size and topography. Optionally, the pretreatment includes processes such as crushing, classification, spheroidization, and purification.

[0117] In some embodiments, the topography of the raw material includes one or more of spherical and substantially spherical.

[0118] In some embodiments, the volume distribution particle size Dv50 of the raw material is 6 μm to 30 μm, and optionally, it is 8 μm to 25 μm. When the volume distribution particle size of the raw material is within the above range, it is advantageous for subsequent filling treatment.

[0119] In some embodiments, the OI value of the raw material is 4 or more, and optionally, it is 4 to 15. Thereby, it is advantageous for the finally manufactured carbon material to have an appropriate OI value, which can accelerate the transport of active ions and improve the kinetic performance of the secondary battery.

[0120] In this application, the OI value of the raw material has the well-known meaning in this field and can be tested by equipment and methods well-known in this field. For example, it can be tested using an X-ray diffractometer (e.g., Bruker D8 Discover). The test refers to JIS K0131-1996 and JB / T 4220-2011 to obtain the X-ray diffraction spectrum of the raw material powder, and the OI value = I 004 / I 110 to calculate the OI value of the raw material. I 004 is the integrated area of the diffraction peak of the 004 crystal plane of the crystalline carbon in the raw material, and I 110 is the integrated area of the diffraction peak of the 110 crystal plane of the crystalline carbon in the raw material.

[0121] In some embodiments, the volume distribution particle size Dv50 of the filling material is 6 μm or less, and optionally 1 μm to 6 μm, 2 μm to 5 μm, 3 μm to 5 μm. Thereby, it is advantageous for the filling material to be filled into the pore structure of the raw material, and it is also advantageous for improving the dispersion uniformity between the filling material and the raw material.

[0122] In some embodiments, the softening point temperature of the filling material is 105°C to 190°C, and optionally, 105°C to 180°C, 105°C to 175°C, 105°C to 170°C, 105°C to 165°C, 105°C to 160°C, 105°C to 155°C, 105°C to 150°C, 110°C to 180°C, 110°C to 175°C, 110°C to 170°C, 110°C to 165°C, 110°C to 160°C, 110°C to 155°C, 110°C to 150°C, 115°C to 180°C, 115°C to 175°C, 115°C to 170°C, 115°C to 165°C, 115°C to 165°C, 115°C to 160°C, 115°C to 155°C, 115°C to 150°C, 115°C to 145°C. The inventors have found that during the research process, when the softening point temperature of the filling material is within the above range, it is advantageous to adjust I 3R(101) / I 2H(004) to be within an appropriate range, and it is also advantageous to adjust the size and / or number of pores in the external and internal regions of the carbon material to be within an appropriate range.

[0123] In some embodiments, the coking value of the filling material is 20% - 48%, and optionally, 25% - 40%. During the research process, the inventors found that when the coking value of the filling material is within the above range, it is advantageous for adjusting I 3R(101) / I 2H(004) to be within an appropriate range, and it is advantageous for adjusting the size and / or number of pores in the external and internal regions of the carbon material to be within an appropriate range.

[0124] In some embodiments, the softening point temperature of the filling material is 110°C - 165°C, and the coking value is 25% - 40%.

[0125] In the present application, the coking value of the filling material has the well-known meaning in this field and can be measured by the equipment and methods well-known in this field. For example, it can be measured with reference to GB / T 8727 - 2008.

[0126] In some embodiments, the filling material includes one or more of coal pitch, petroleum pitch, polymer compounds, and resins, and optionally includes petroleum pitch.

[0127] In some embodiments, the mass ratio of the filling material to the raw material is (10 - 40):100, and optionally (15 - 30):100. Thereby, I 3R(101) / I 2H(004)It is advantageous to adjust so that it is within an appropriate range, and it is advantageous to adjust so that the size and / or the number of pores in the external region and the internal region of the carbon material are within an appropriate range. When the mass ratio of the filling material to the raw material is too small, the dispersion uniformity of the filling material and the raw material may deteriorate. In this case, the filling material cannot effectively modify the internal defects of the particles, and the electrolyte cannot be effectively prevented from penetrating into the pore structure inside the obtained carbon material particles, which affects the initial Coulomb efficiency and cycle performance of the secondary battery. When the mass ratio of the filling material to the raw material is too large, the pore structure inside the raw material is likely to be completely filled. At this time, the volume change of the obtained carbon material becomes large, the particles are more likely to be crushed, the consumption of active ions due to the formation of the SEI film increases, and the irreversible capacity loss of the secondary battery increases. When the mass ratio of the filling material to the raw material is too large, a large amount of the filling material is likely to remain on the particle surface. In this case, the particles are more likely to aggregate, not only increasing the depolymerization process, but also reducing the gram capacity and compression density of the obtained carbon material. These can be effectively avoided.

[0128] By adjusting one or more parameters such as the type, softening point, coking value, addition amount, etc. of the filling material within the above range, I 3R(101) / I 2H(004) It is advantageous to adjust so that it is within an appropriate range, and it is advantageous to adjust so that the size and / or the number of pores in the external region and the internal region of the carbon material are within an appropriate range. Also, after the filling material is thermally melted, the viscosity does not increase, good fluidity is maintained, and it is difficult for the raw material particles to adhere, and the aggregation of the raw material particles in the subsequent manufacturing process can be reduced. Thereby, problems such as an increase in surface defects of the carbon material particles and an increase in side reactions due to the need to increase the depolymerization process can be reduced.

[0129] In some embodiments, in step 2, after uniformly mixing the raw material and the filling material at a predetermined ratio, the first temperature T 1The temperature-rising process of rising the temperature up to is a stepwise temperature-rising process, and optionally includes a first temperature-rising process and a second temperature-rising process.

[0130] In some embodiments, the first temperature-rising process raises the temperature to 200°C to 300°C and holds the temperature for 1 h to 3 h. The inventors have discovered in the research process that when the holding time is within the above range, it is advantageous for adjusting the pore size and / or the number of pores in the external and internal regions of the carbon material to be within an appropriate range.

[0131] In some embodiments, the second temperature-rising process raises the temperature to the first temperature T 1 and holds the temperature for the first time t 1 at this temperature.

[0132] In some embodiments, the first temperature T 1 is 700°C to 1100°C, and optionally 750 to 1100°C, 800 to 1100°C, 850 to 1100°C, 900 to 1100°C, 950 to 1100°C.

[0133] The inventors have discovered in the research process that when the first temperature is within the above range, it is advantageous for adjusting the pore size and / or the number of pores in the external and internal regions of the carbon material to be within an appropriate range. If the first temperature is too low, a part of the filling material may not be converted into the carbon material. When heat treatment is performed in subsequent step 3, by continuously decomposing into small molecule substances, the actual residual carbon in the filling region has many pore structures and cannot effectively modify the internal defects of the particles, and cannot effectively prevent the electrolyte from infiltrating into the internal pore structure of the obtained carbon material particles, further affecting the initial Coulomb efficiency and cycle performance of the secondary battery. If the first temperature is too high, the energy consumption in the manufacturing process of the carbon material increases, which can be effectively avoided.

[0134] In some embodiments, the first time t 1 is 1 h to 5 h. For example, the first time t1 may be a range consisting of any value of 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h or more. Optionally, the first time t 1 is from 2 h to 4 h.

[0135] In the research process, the inventors found that when the first time is within the above range, it is advantageous to adjust the pore size and / or the number of pores in the external and internal regions of the carbon material to be within an appropriate range. If the first time is too short, part of the filling material may not be converted into the carbon material. When heat treatment is carried out in subsequent step 3, by continuously decomposing into small molecule substances, the actual residual carbon in the filling region has many pore structures and cannot effectively modify the internal defects of the particles, and the electrolyte cannot be effectively prevented from infiltrating into the pore structure inside the obtained carbon material particles, further affecting the initial Coulomb efficiency and cycle performance of the secondary battery. If the first time is too long, the energy consumption in the manufacturing process of the carbon material increases, which can be effectively avoided.

[0136] In the stepwise heating process, first, the temperature is raised to 200°C to 300°C. Since the heating temperature is higher than the softening point temperature of the filling material, at this time, the filling material melts and softens by heating and can be kept warm for 1 h to 3 h to be flowed and filled into the pore structure of the raw material. Then, the temperature is raised to the first temperature. At this time, the filling material undergoes a carbonization reaction, and the pore structure occupied by the filling material is effectively filled.

[0137] In some embodiments, the heating rate of the first heating process may be 1°C / min to 10°C / min, and optionally 1.5°C / min to 8°C / min. In the research process, the inventors found that when the heating rate is within the above range, it is advantageous to adjust the pore size and / or the number of pores in the external and internal regions of the carbon material to be within an appropriate range.

[0138] In some embodiments, the heating rate in the second heating process may be 2°C / min to 10°C / min, and optionally 2.5°C / min to 8°C / min.

[0139] In some embodiments, in step 2, the heat treatment can be carried out in a vertical granulation kettle, a horizontal granulation kettle, a vertical reaction kettle, a horizontal reaction kettle or a drum furnace.

[0140] In some embodiments, in step 2, the atmosphere of the heat treatment may be a protective gas atmosphere. The protective gas may include one or more of nitrogen gas, argon gas, and helium gas.

[0141] In step 2, by adjusting one or more of the heating rate, the first temperature, the first time, the heating process, etc. within the above ranges, it is advantageous to adjust the pore size and / or the number of pores in the external and internal regions of the carbon material to be within an appropriate range.

[0142] In some embodiments, the second temperature T 2 is 1850°C to 2650°C, and optionally 1950°C to 2580°C, 1950°C to 2520°C, 1950°C to 2480°C, 1950°C to 2420°C, 1950°C to 2360°C, 2020°C to 2580°C, 2020°C to 2520°C, 2020°C to 2480°C, 2020°C to 2420°C, 2020°C to 2360°C, 2100°C to 2580°C, 2100°C to 2520°C, 2100°C to 2480°C, 2100°C to 2420°C, 2100°C to 2360°C.

[0143] The inventors found that during the research process, when the second temperature is within the above range, it is advantageous to adjust I 3R(101) / I 2H(004) to be within an appropriate range, and it is also advantageous to adjust the pore size and / or the number of pores in the external and internal regions of the carbon material to be within an appropriate range. If the second temperature is too low, the surface defects and / or bulk phase defects of the obtained carbon material will increase, and I 3R(101) / I 2H(004)When it is large, the surface stability of the carbon material particles decreases, the side reactions on the particle surface increase, which affects the initial Coulomb efficiency and cycle performance of the secondary battery. When the second temperature is too high, the obtained carbon material does not contain 3R-phase crystalline carbon, and at this time, the interlayer spacing of the carbon material becomes small, which is disadvantageous for the transport of active ions and affects the kinetic performance of the secondary battery. It can be effectively avoided.

[0144] In some embodiments, the second time t 2 is 1.5 h to 6 h. For example, the second time t 1 may be in the range consisting of any numerical values such as 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h, 6 h or more. Optionally, the second time t 2 is 2 h to 5 h.

[0145] The inventors found that during the research process, when the second time is within the above range, it is advantageous to adjust I 3R(101) / I 2H(004) to be within an appropriate range, and it is advantageous to adjust the pore size and / or the number of pores in the external and internal regions of the carbon material to be within an appropriate range. When the second time is too short, the surface defects and / or bulk-phase defects of the obtained carbon material increase, and due to the large I 3R(101) / I 2H(004) the surface stability of the carbon material particles decreases, the side reactions on the particle surface increase, which affects the initial Coulomb efficiency and cycle performance of the secondary battery. When the second time is too long, the obtained carbon material does not contain 3R-phase crystalline carbon, and at this time, the interlayer spacing of the carbon material becomes small, which is disadvantageous for the transport of active ions and affects the kinetic performance of the secondary battery. It can be effectively avoided.

[0146] In some embodiments, in step 3, the heat treatment can be carried out in an intermediate frequency furnace, a box-type graphitization furnace, an Acheson-type graphitization furnace, a continuous graphitization furnace or an internal series graphitization furnace.

[0147] In some embodiments, in step 3, for the intermediate frequency furnace, the continuous graphitization heat treatment atmosphere may be a protective gas atmosphere. The protective gas may include one or more of nitrogen gas, argon gas, and helium gas.

[0148] In step 3, by adjusting the second temperature and / or the second time to be within the above ranges, it is advantageous to adjust I 3R(101) / I 2H(004) to be within an appropriate range, advantageous to adjust the size and / or the number of pores in the external region and the internal region of the carbon material to be within an appropriate range, and also advantageous to improve the cycle performance and / or the kinetic performance of the secondary battery.

[0149] The method for manufacturing the carbon material of the present application has a simple process, high safety, does not require a predetermined pressure or vacuum suction treatment, and does not require an additional depolymerization step in the heat treatment process. Both the surface defects and / or the bulk phase defects of the carbon material manufactured in the present application are few, the carbon material can have high ion transport performance, high surface stability, and low volume change, and further, the secondary battery using it can have high initial Coulomb efficiency, good cycle performance, and kinetic performance.

[0150] The manufacturing method of the present application has low cost, high practicality, and is suitable for large-scale industrialization. Secondary battery

[0151] The third aspect of the embodiment of the present application provides a secondary battery.

[0152] This application is not particularly limited to the type of secondary battery. For example, the secondary battery may be a lithium-ion battery or the like. Generally, the secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and the like. In the charge and discharge process of the secondary battery, active ions reciprocally insert and desorb between the positive electrode sheet and the negative electrode sheet, and the electrolyte functions to conduct active ions between the positive electrode sheet and the negative electrode sheet. The type of the electrolyte in this application is not particularly limited and can be selected according to actual needs. For example, the electrolyte may be at least one selected from a solid electrolyte and a liquid electrolyte (electrolyte solution). In a secondary battery using an electrolyte solution and some secondary batteries using a solid electrolyte, a separator may be further provided between the positive electrode sheet and the negative electrode sheet to play a role of isolation. [Negative electrode sheet]

[0153] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector. For example, the negative electrode current collector has two surfaces facing each other in the thickness direction, and the negative electrode film layer is provided on either one or both of the two surfaces of the negative electrode current collector.

[0154] In some embodiments, the negative electrode film layer includes the carbon material of the first aspect of the embodiment of this application or the carbon material manufactured by the method described in the second aspect of the embodiment of this application. Thereby, the secondary battery can be provided with high initial Coulomb efficiency, good cycle performance, and kinetic performance.

[0155] In some embodiments, the negative electrode film layer may further include other negative electrode active materials other than the carbon material. In some embodiments, the other negative electrode active materials include, but are not limited to, one or more of conventional natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based materials may include one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material. The tin-based materials may include one or more of elemental tin, tin oxide, and tin alloy material.

[0156] In some embodiments, the negative electrode film layer may optionally further include a negative electrode conductive agent. In the present application, the type of the negative electrode conductive agent is not particularly limited. As an example, the negative electrode conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dot, carbon nanotube, graphene, and carbon nanofiber.

[0157] In some embodiments, the negative electrode film layer may optionally further include a negative electrode adhesive. In the present application, the type of the negative electrode adhesive is not particularly limited. As an example, the negative electrode adhesive may include one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0158] In some embodiments, the negative electrode film layer may optionally further include other auxiliaries. Examples of the other auxiliaries include thickeners such as sodium carboxymethyl cellulose (CMC) and PTC thermistor materials.

[0159] In some embodiments, the negative electrode current collector can employ a metal foil piece or a composite current collector. As an example of the metal foil piece, a copper foil can be used. The composite current collector can include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0160] The negative electrode film layer is usually formed by applying a negative electrode slurry to a negative electrode current collector, drying, and cold pressing. The negative electrode slurry is usually formed by dispersing a negative electrode active material, an optional conductive agent, an optional adhesive, and an optional other auxiliary agent in a solvent and uniformly stirring. The solvent may be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.

[0161] The negative electrode sheet does not exclude other additional functional layers other than the negative electrode film layer. For example, in some embodiments, the negative electrode sheet according to the present application further includes a conductive primer layer (for example, composed of a conductive agent and an adhesive) sandwiched between the negative electrode current collector and the negative electrode film layer and provided on the surface of the negative electrode current collector. In some embodiments, the negative electrode sheet according to the present application further includes a protective layer coated on the surface of the negative electrode film layer. [Positive Electrode Sheet]

[0162] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector. For example, the positive electrode current collector has two surfaces facing each other in the thickness direction, and the positive electrode film layer is provided on either one or both of the two surfaces of the positive electrode current collector.

[0163] The positive electrode current collector can use a metal foil piece or a composite current collector. As an example of the metal foil piece, an aluminum foil can be used. The composite current collector can include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0164] The positive electrode film layer usually includes a positive electrode active material, an optional adhesive, and an optional conductive agent. The positive electrode film layer is usually formed by applying a positive electrode slurry to the positive electrode current collector, drying, and cold pressing. The positive electrode slurry is usually formed by dispersing a positive electrode active material, an optional conductive agent, an optional adhesive, and any other components in a solvent and stirring uniformly. The solvent may be N-methylpyrrolidone (NMP), but is not limited thereto. As an example, the adhesive used in the positive electrode film layer may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a terpolymer of vinylidene fluoride-tetrafluoroethylene-propylene, a terpolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, a copolymer of tetrafluoroethylene-hexafluoropropylene, and a fluorine-containing acrylate resin. As an example, the conductive agent used in the positive electrode film layer may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dot, carbon nanotube, graphene, and carbon nanofiber.

[0165] As the positive electrode active material, a well-known positive electrode active material for secondary batteries in this field can be used.

[0166] When the secondary battery of the present application is a lithium-ion battery, the positive electrode active material may include, but is not limited to, one or more of lithium-containing transition metal oxides, lithium-containing phosphates, and their respective modified compounds. Examples of the lithium transition metal oxide 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. Examples of the lithium-containing phosphate 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 manganese iron phosphate, a composite material of lithium manganese iron phosphate and carbon, and their respective modified compounds.

[0167] In some embodiments, in order to further increase the energy density of the secondary battery, the positive electrode active material used in the lithium-ion battery may include one or more of lithium transition metal oxides represented by the general formula Li a Ni b Co c M d O e A f and their modified compounds. 0.8 ≦ a ≦ 1.2, 0.5 ≦ b < 1, 0 < c < 1, 0 < d < 1, 1 ≦ e ≦ 2, 0 ≦ f ≦ 1, M is one or more selected from Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, and B, and A is one or more selected from N, F, S, and Cl.

[0168] In some embodiments, for example, the positive electrode active material used in the lithium-ion battery is LiCoO 2 、LiNiO 2 、LiMnO 2 、LiMn 2 O 4 、LiNi 1 / 3 Co1 / 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 may contain one or more of them.

[0169] In the present application, the modified compound of each of the above positive electrode active materials is obtained by performing doping modification and / or surface coating modification on the positive electrode active material. [Electrolyte]

[0170] In some embodiments, the electrolyte employs an electrolytic solution, and the electrolytic solution contains an electrolyte salt and a solvent.

[0171] The type of the electrolyte salt is not particularly limited and can be selected according to actual needs.

[0172] When the secondary battery of the present application is a lithium ion battery, for example, the electrolyte salt is lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6) Lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium bis(oxalate) borate (LiBOB), lithium difluorophosphate (LiPO 2 F 2 ) may include one or more of lithium difluorobis(oxalate) phosphate (LiDFOP) and lithium tetrafluorooxalate phosphate (LiTFOP).

[0173] The type of the solvent is not particularly limited and can be selected according to actual needs. In some embodiments, by way of example, the solvent may include one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0174] In some embodiments, the electrolyte may optionally further include an additive. For example, the additive may include a negative electrode film-forming additive, may include a positive electrode film-forming additive, and may include additives that can improve some performance 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, additives that improve the low-temperature power performance of the secondary battery, and the like. [Separator]

[0175] In this application, the type of the separator is not particularly limited, and any well-known porous structure separator having good chemical stability and mechanical stability can be selected.

[0176] In some embodiments, the material of the separator may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer may be the same or different.

[0177] In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet can be used to manufacture an electrode assembly by a winding process or a lamination process.

[0178] In some embodiments, the secondary battery may include an exterior. The exterior is used for sealing the above-described electrode assembly and electrolyte.

[0179] In some embodiments, the exterior may be a hard case such as a hard plastic case, an aluminum case, or a steel case. The exterior may also be, for example, a soft bag of a bag package. The material of the soft package may be one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0180] The shape of the secondary battery of this application is not particularly limited, and it may be cylindrical, rectangular, or any other arbitrary shape. FIG. 2 shows a rectangular-structured secondary battery 5 as an example.

[0181] In some embodiments, as shown in FIG. 3, the exterior can include a housing 51 and a cover plate 53. The housing 51 includes a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose to form a housing chamber. The housing 51 has an opening communicating with the housing chamber, and the cover plate 53 closes the opening so as to close the housing chamber. The positive electrode sheet, the negative electrode sheet, and the separator can form an electrode assembly 52 by a winding process or a lamination process. The electrode assembly 52 is packaged in the housing chamber. The electrolyte infiltrates the electrode assembly 52. The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and may be adjusted according to needs.

[0182] The manufacturing method of the secondary battery of the present application is well-known. In some embodiments, a secondary battery can be formed by assembling a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte. As an example, a positive electrode sheet, a separator, and a negative electrode sheet are formed into an electrode assembly by a winding process or a lamination process, the electrode assembly is placed in an exterior, and after drying, an electrolyte is injected, and through processes such as vacuum encapsulation, standing, formation, and shaping, a secondary battery can be obtained.

[0183] In some embodiments of the present application, the secondary battery of the present application may be assembled into a battery module, and the number of secondary batteries included in the battery module may be plural, and the specific number may be adjusted according to the application and capacity of the battery module.

[0184] FIG. 4 is a schematic diagram of a battery module 4 as an example. As shown in FIG. 4, in the battery module 4, a plurality of secondary batteries 5 may be arranged in sequence along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Further, the plurality of secondary batteries 5 may be fixed by fasteners.

[0185] Optionally, the battery module 4 further includes an external case having an accommodation space, and the plurality of secondary batteries 5 are accommodated in the accommodation space.

[0186] In some embodiments, the battery module may be assembled as a battery pack, and the number of battery modules included in the battery pack may be adjusted according to the use and capacity of the battery pack.

[0187] FIGS. 5 and 6 are schematic diagrams of a battery pack 1 as an example. As shown in FIGS. 5 and 6, the battery pack 1 may include a battery case and a plurality of battery modules 4 provided in the battery case. The battery case includes an upper case 2 and a lower case 3, and the upper case 2 covers the lower case 3 to form a sealed space for accommodating the battery module 4. The plurality of battery modules 4 may be arranged in the battery case in any manner. Power consumption device

[0188] Embodiments of the present application provide a power consumption device including at least one of a secondary battery, a battery module, or a battery pack of the present application. The secondary battery, battery module, or battery pack may be used as a power source of the power consumption device or as an energy storage means of the power consumption device. The power consumption device may be a mobile device (e.g., a mobile phone, a tablet computer, a notebook computer, etc.), an electric vehicle (e.g., 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.), a train, a ship, and a satellite, an energy storage system, etc., but is not limited thereto.

[0189] The power consumption device can select a secondary battery, a battery module, or a battery pack according to needs.

[0190] FIG. 7 is a schematic diagram of a power consumption device as an example. This power consumption device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. In order to meet the requirements of high output and high energy density of this power consumption device, a battery pack or a battery module can be adopted.

[0191] As another example, the power consumption device may be a mobile phone, a tablet computer, a notebook computer, or the like. This power consumption device is generally required to be thinner and can adopt a secondary battery as a power source. Example

[0192] The following examples illustrate the content of this application in more detail. However, these examples are merely illustrative and it is obvious to those skilled in the art that various modifications and changes can be made within the scope of the disclosure of this application. Unless otherwise specified, all values of parts, percentages, and ratios described in the following examples are calculated based on mass standards. Also, all reagents used in the examples may be commercially available or synthesized according to conventional methods, and can be used as they are without further treatment. In addition, all devices used in the examples are commercially available. Example 1 (1) Manufacture of carbon material

[0193] Step 1: Mechanically pulverize, classify, spheroidize, and purify 100-mesh flaky graphite to obtain natural spherical graphite. Its volume distribution particle size Dv50 is 12 μm and the OI value is 5.5.

[0194] Step 2: Mix the obtained natural spherical graphite and petroleum pitch (softening point temperature is 142 °C, volume distribution particle size Dv50 is 5 μm, coking value is 35%) in a mass ratio of 100:20 in a VC mixer for 30 minutes. Then place the mixed material in a drum furnace, heat it to 220 °C at a rate of 4 °C / min and hold for 2 hours (the first heating process). Then, heat it to 1100 °C at a rate of 5 °C / min and hold for 1.5 hours (the second heating process). After completion, cool it to room temperature to obtain an intermediate.

[0195] Step 3: Put the obtained intermediate into an Acheson graphitization furnace, heat it to 2320 °C and hold for 3 hours. After completion, demagnetize and screen it to obtain a carbon material. (2) Manufacture of coin cell (half cell)

[0196] The carbon material sample manufactured above, styrene-butadiene rubber (SBR) as an adhesive, sodium carboxymethyl cellulose (CMC) as a thickener, and carbon black as a conductive agent are sufficiently stirred and mixed in deionized water, which is an appropriate solvent, at a mass ratio of 96.2:1.8:1.2:0.8 to form a uniform negative electrode slurry. The negative electrode slurry is uniformly coated on the surface of a copper foil, which is a negative electrode current collector, and after drying in an oven, it is prepared. After mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) at a volume ratio of 1:1:1 to obtain an organic solvent, LiPF 6 is dissolved in the organic solvent to produce an electrolyte solution with a concentration of 1 mol / L. Then, a CR2430 coin cell is assembled in a glove box protected by argon gas, using a lithium metal piece as the counter electrode and a polyethylene (PE) thin film as the separator. (3) Manufacture of a secondary battery (full cell)

[0197] The carbon material manufactured above, carbon black (Super P) as a conductive agent, styrene-butadiene rubber as an adhesive, and sodium carboxymethyl cellulose as a thickener are sufficiently stirred and mixed in deionized water, which is an appropriate solvent, at a weight ratio of 96:1:1:2 to form a negative electrode slurry. The negative electrode slurry is coated on both surfaces of a copper foil, which is a negative electrode current collector, dried, and cold-pressed to obtain a negative electrode sheet.

[0198] LiFePO 4 and conductive carbon black and polyvinylidene fluoride are mixed at a weight ratio of 96:2.5:1.5, an appropriate amount of solvent NMP is added, and they are uniformly stirred to obtain a positive electrode slurry. The positive electrode slurry is coated on both surfaces of an aluminum foil, which is a positive electrode current collector, dried, and cold-pressed to obtain a positive electrode sheet.

[0199] A polypropylene film with a thickness of 12 μm is used as a separator, which is placed in order with the positive electrode sheet and the negative electrode sheet manufactured above. The separator is positioned in the middle of the positive electrode sheet and the negative electrode sheet to play a role in isolation, and then it is wound to obtain an electrode assembly. The electrode assembly is placed in an outer package, dried, and then the same electrolyte as the above coin cell is injected. After passing through processes such as vacuum encapsulation, standing, formation, and capacity, a secondary battery is obtained. Comparative Example 1

[0200] The manufacturing methods of the half cell and the full cell are similar to those of Example 1, but the manufacturing process of the carbon material is different.

[0201] The 100-mesh flaky graphite is subjected to mechanical grinding, classification, spheroidization, and purification treatment to obtain natural spherical graphite. Its volume distribution particle size Dv50 is 12 μm, and the OI value is 5.5. Comparative Example 2

[0202] The manufacturing methods of the half cell and the full cell are similar to those of Example 1, but the manufacturing process of the carbon material is different.

[0203] The 100-mesh flaky graphite is subjected to mechanical grinding, classification, spheroidization, and purification treatment to obtain natural spherical graphite. Its volume distribution particle size Dv50 is 12 μm, and the OI value is 5.5.

[0204] The obtained natural spherical graphite and petroleum pitch (softening point temperature 142 °C, volume distribution particle size Dv50 is 5 μm, coking value 35%) are mixed in a VC mixer at a mass ratio of 100:20 for 30 min, and then the mixed material is graphitized at 3200 °C for 6 h. After completion, it is cooled to room temperature to obtain a carbon material. Comparative Example 3

[0205] The manufacturing methods of the half cell and the full cell are similar to those of Example 1, but the manufacturing process of the carbon material is different.

[0206] The 100-mesh flaky graphite is subjected to mechanical grinding, classification, spheroidization, and purification treatment to obtain natural spherical graphite. Its volume distribution particle size Dv50 is 12 μm, and the OI value is 5.5.

[0207] The obtained natural spherical graphite and petroleum pitch (softening point temperature 142°C, volume distribution particle size Dv50 is 5 μm, coking value 35%) were mixed in a VC mixer at a mass ratio of 100:20 for 30 min, and then the mixed material was carbonized at 1300°C for 3 h. After completion, it was cooled to room temperature to obtain a carbon material. Comparative Example 4

[0208] The manufacturing methods of the half-cell and full-cell are similar to those of Example 1, but the manufacturing process of the carbon material is different.

[0209] The 100-mesh flaky graphite was subjected to mechanical pulverization, classification, spheroidization, and purification treatments to obtain natural spherical graphite, with its volume distribution particle size Dv50 being 12 μm and the OI value being 5.5.

[0210] The obtained natural spherical graphite and petroleum pitch (softening point temperature is 142°C, volume distribution particle size Dv50 is 5 μm, and coking value is 35%) are mixed in a VC mixer for 30 min. Then, the mixed material is put into a reaction kettle, and the reaction kettle adopts a method of gradually increasing the temperature at a heating rate of 2°C / min. While heating, the reaction kettle is maintained in a constant-speed stirring state until the temperature rises to 190°C. The reaction kettle is evacuated until the pressure reaches -0.1 Mpa, and then it is kept warm for 2 h. After the heat preservation is completed, the reaction kettle is heated to 650°C and kept warm for 2 h. Then, the reaction kettle is cooled to about 160°C. Subsequently, petroleum pitch is gradually added into the reaction kettle, and the mass ratio of the added amount of petroleum pitch this time to the previous petroleum pitch is 1:1. Then, the reaction kettle is heated to 190°C again, and the reaction kettle is evacuated until the pressure reaches -0.1 Mpa. Then, it is kept warm for 2 h. After the heat preservation is completed, the reaction kettle is heated to 650°C and kept warm for 2 h. Then, it is cooled by condensation and temperature reduction. Finally, the material processed in the above process is heat-treated at 1300°C for 3 h, and the heat-treated sample is pulverized and sieved to obtain a carbon material without internal voids. Examples 2 to 17

[0211] The manufacturing methods of the half-cell and full-cell are similar to those of Example 1, but are different in that the parameters of the manufacturing process of the carbon material are adjusted. Specifically, refer to Table 1.

[0212] [Table 1] Performance test (1) Test of X-ray diffraction analysis

[0213] Referring to JIS K0131-1996, a test is conducted using an X-ray diffractometer to obtain the X-ray diffraction spectrum of the carbon material. The test conditions are as follows: the carbon material is manufactured into a sample by the flat sample manufacturing method, CuKα ray is used as the radiation source, a copper target is used as the anode target, the voltage is 40 KV, the current is 40 mA, the anti-scattering slit is 1 mm, the scanning 2θ angle range is 20° - 80°, the step size is 0.01671°, the step time is 0.24 s, and the scanning speed is 4° / min. The test equipment can use a Bruker D8 Discover X-ray diffractometer.

[0214] The 2θ of the diffraction peak of the 101 crystal plane of the 3R phase is in the range of 43° - 44°, the 2θ of the diffraction peak of the 004 crystal plane of the 2H phase is in the range of 53° - 55°, and the 2θ of the diffraction peak of the 012 crystal plane of the 3R phase is in the range of 46° - 47°. The peak intensity of the diffraction peak of the 101 crystal plane of the 3R phase and the peak intensity of the diffraction peak of the 004 crystal plane of the 2H phase are represented by the integral area of the corresponding diffraction peak. (2) Test of the total pore area in the external and internal regions of the carbon material

[0215] After uniformly mixing the adhesive for sample manufacturing and the carbon material powder, it is applied on a copper foil and dried at 60°C for 30 min for preparation. The sample is cut into a size of 6 mm × 6 mm and attached to the sample stage of a CP type argon ion cross-section polishing device, and the sample is cut using a plasma beam to obtain the cross-section of the carbon material, and the cross-section of the carbon material passes through the center of the carbon material particles. The test equipment is an IB-09010 CP type argon ion cross-section polishing machine manufactured by JEOL, Japan.

[0216] The cross-section of the carbon material is scanned using a scanning electron microscope. The test can refer to JY / T010-1996. The test equipment may be a Sigma 300 type scanning electron microscope manufactured by ZEISS of Germany.

[0217] A region formed by extending a distance of 0.25L from the particle surface to the particle interior of the carbon material is defined as the external region, and the region inside the external region is defined as the internal region, where L represents the length of the minor axis of the carbon material particles. The total pore area S of the external region of the carbon material 1 and the total pore area S of the internal region of the carbon material 2 are calculated. The image processing software may be AVIZO. (3) Test of the initial Coulomb efficiency of the carbon material

[0218] At 25°C, first, the above-prepared coin cell is discharged to 0.005V at a constant current of 0.15mA, left standing for 5 minutes, and then discharged to 0.005V at a constant current of 10μA. The initial discharge capacity of the coin cell is recorded. Then, it is charged to 2.0V at a constant current of 0.3mA, and the initial charge capacity of the coin cell is recorded. The initial Coulomb efficiency (%) of the carbon material = initial charge capacity of the coin cell / initial discharge capacity of the coin cell × 100%. (4) Test of the cycle performance of the secondary battery

[0219] At 25°C, after charging the above-prepared secondary battery to the upper limit cut-off voltage (corresponding to 100% SOC) at a constant current of 1C, it is charged at a constant voltage until the current reaches 0.05C, left standing for 5 minutes, and then the secondary battery is discharged to the lower limit cut-off voltage (corresponding to 0% SOC) at a constant current of 1C. The discharge capacity at this time is recorded and used as the first discharge capacity. The secondary battery is subjected to a cycle charge and discharge test according to the above method, and the discharge capacity after each cycle is recorded. The capacity retention rate (%) after 2000 cycles at 25°C of the secondary battery = discharge capacity after 2000 cycles / first discharge capacity × 100%. (5) Test of the maximum charge rate of the secondary battery

[0220] At 25°C, the secondary battery is discharged at a constant current to the lower cut-off voltage (corresponding to 0% SOC) at a rate of 1C. Then, it is charged at a constant current to the upper cut-off voltage (corresponding to 100% SOC) at a rate of 1C, and the constant voltage charging is continued until the current reaches 0.05C. At this time, the secondary battery is in a fully charged state. After the fully charged secondary battery is left standing for 5 minutes, it is discharged at a constant current to the lower cut-off voltage (corresponding to 0% SOC) at a rate of 1C. The discharge capacity at this time is the actual capacity of the secondary battery at a rate of 1C, denoted as C0. The secondary battery is charged at a constant current to the upper cut-off voltage (corresponding to 100% SOC) at a rate of xC0 (representing the gradient charging rate, for example, 1C0, 1.05C0, 1.1C0, 1.15C0, 1.2C0, 1.25C0, 1.3C0, 1.35C0, 1.4C0···), and the constant voltage charging is continued until the current reaches 0.05C0. After leaving it standing for 5 minutes, the secondary battery is disassembled to observe the lithium precipitation on the surface of the negative electrode sheet. If there is no lithium precipitation on the surface of the negative electrode sheet, the charging rate is increased and the test is carried out again until lithium precipitates on the surface of the negative electrode sheet. Record the maximum charging rate at which no lithium precipitates on the surface of the negative electrode sheet.

[0221]

Table 2

[0222] Parameters such as the specific surface area, volume distribution particle size, particle size distribution, graphitization degree, tap density, and compression density of the powder of the carbon materials produced in Examples 1 to 17 are within the ranges described in the specification of this application.

[0223] Figure 8 is the X-ray diffraction spectrum of the carbon material produced in Example 1. As can be seen from summarizing the test results in Table 2, when the X-ray diffraction spectrum of the carbon material satisfies 0 < I 3R(101) / I 2H(004) ≤ 0.100, the battery can have high initial Coulomb efficiency and good cycle performance and kinetic performance. Also, when the X-ray diffraction spectrum of the carbon material further satisfies 0.005 ≤ I 3R(101) / I 2H(004) ≤ 0.100, and optionally 0.008 ≤ I 3R(101) / I 2H(004)When it satisfies ≦0.065, it can better possess high initial Coulomb efficiency, good cycle performance, and kinetic performance for the battery.

[0224] As can be seen from summarizing the test results in Table 2, when there is no peak of the crystal plane of 3R phase 012 in the X-ray diffraction spectrum of the carbon material, it can better possess high initial Coulomb efficiency, good cycle performance, and kinetic performance for the battery.

[0225] As can be seen from summarizing the test results in Table 2, when the carbon material further satisfies S 2 >S 1 and optionally satisfies 1.5 ≦ S 2 / S 1 ≦ 420, the overall performance of the battery is further improved. At this time, the carbon material particles further have the characteristics that the number of pores in the internal region is large and / or the pore size is large, and the number of pores in the external region is small and / or the pore size is small. Since the pore structure in the internal region of the carbon material can ensure the expansion space required for the volume change of the carbon material particles, it reduces the risk of generating new interfaces due to the crushing of the carbon material particles, reduces the occurrence of side reactions, and reduces the irreversible capacity loss of the battery. Since the number of pores in the external region of the carbon material is small and / or the pore size is small, the carbon material particles have a more stable structure, and the electrolyte can be avoided from infiltrating into the pore structure inside the carbon material particles as much as possible, so the occurrence of side reactions is reduced, and the consumption of active ions due to the formation of the SEI film inside the particles is reduced. Thereby, the carbon material further satisfying the above structural characteristics can further improve the overall performance of the battery.

[0226] The X-ray diffraction spectra of the carbon materials manufactured in Comparative Examples 1 to 4 all do not satisfy 0 < I 3R(101) / I 2H(004) ≦ 0.100, and none of them can possess high initial Coulomb efficiency, good cycle performance, and kinetic performance for the battery.

[0227] Comparative Example 1 uses untreated natural spherical graphite as the carbon material. It has many voids and defects inside the carbon material particles. As can be seen from the test results in Table 2, the initial Coulomb efficiency, cycle performance, and kinetic performance of the battery manufactured thereby are all inferior.

[0228] The carbon material manufactured in Comparative Example 2 forms a coating layer of a carbon layer on the surface of natural spherical graphite. Due to the high heat treatment temperature and long heat treatment time, the interlayer spacing of the carbon material is small, which is disadvantageous for the transport of active ions. As can be seen from the combination with the test results in Table 2, the kinetic performance of the battery manufactured thereby deteriorates. Also, the coating layer only exists on the surface of natural spherical graphite, and an effective filling effect cannot be realized. The electrolyte cannot be effectively prevented from infiltrating into the pore structure inside the particles, and the improvement effect on the cycle performance of the battery is also limited.

[0229] The carbon material manufactured in Comparative Example 3 forms a coating layer of a carbon layer on the surface of natural spherical graphite. Due to the low heat treatment temperature, the main component of the coating layer is amorphous carbon, and the surface defects and / or bulk phase defects of the carbon material increase. Also, the coating layer only exists on the surface of natural spherical graphite, and an effective filling effect cannot be realized. The electrolyte cannot be effectively prevented from infiltrating into the pore structure inside the particles, and the improvement effects on the cycle performance and kinetic performance of the battery are also limited.

[0230] When manufacturing the carbon material in Comparative Example 4, the filling material is filled into all the pore structures inside the natural spherical graphite particles by vacuum suction. Due to the low heat treatment temperature, a large amount of amorphous carbon exists inside and on the surface of the carbon material particles. Also, since there is no pore structure inside the carbon material particles obtained at this time, the volume change occurring in the process of desorption and insertion of active ions of the carbon material becomes large, and the particles are more likely to break, and the improvement effects on the cycle performance and kinetic performance of the battery are also limited.

[0231] Note that this application is not limited to the above embodiments. The above embodiments are examples, and any configurations that have substantially the same technical idea and exhibit the same operational effects within the technical scope of this application are included in the technical scope of this application. Also, within the scope not departing from the gist of this application, other forms that can be conceived by those skilled in the art, various modifications to the embodiments, and configurations constructed by combining some of the components in the embodiments are also included in the scope of this application.

Description of Reference Numerals

[0232] 1 Battery pack, 2 Upper case, 3 Lower case, 4 Battery module, 5 Secondary battery, 51 Housing, 52 Electrode assembly, 53 Cover plate, 100 Carbon material, 101 External region, 102 Internal region.

Claims

1. A carbon material including a pore structure, The carbon material has a coexistence of 3R phase and 2H phase, and satisfies 0 < I ３Ｒ（１０１） / I ２Ｈ（００４） ≤ 0.100 I ３Ｒ（１０１） is the peak intensity of the diffraction peak of the 101 crystal plane of the 3R phase in the X-ray diffraction spectrum of the carbon material, and I ２Ｈ（００４） is the peak intensity of the diffraction peak of the 004 crystal plane of the 2H phase in the X-ray diffraction spectrum of the carbon material. the carbon material.

2. 0.005 ≤ I ３Ｒ（１０１） / I ２Ｈ（００４） ≤ 0.100, and optionally, 0.008 ≤ I ３Ｒ（１０１） / I ２Ｈ（００４） ≤ 0.065 The carbon material according to Claim 1.

3. In the X-ray diffraction pattern of the carbon material, there is no peak of the 012 crystal plane of the 3R phase, The carbon material according to Claim 1 or 2.

4. The carbon material includes one or more pore structures with a pore area of 0.15 μm ２ or more, and optionally includes one or more pore structures with a pore area of 0.15 μm ２ to 2.0 μm ２ or more. The carbon material according to any one of Claims 1 to 3.

5. The carbon material includes an outer region and an inner region located inside the outer region, the outer region is a region formed by extending a distance of 0.25 L from the particle surface of the carbon material to the particle interior, L refers to the length of the short axis of the carbon material particles, and the total pore area of the external region is S １ is denoted as, and the total pore area of the internal region is S ２ is denoted as, and moreover, S ２ > S １ is true The carbon material according to any one of Claims 1 to 4.

6. 1.5 ≤ S ２ / S １ ≤ 420, and optionally 2 ≤ S ２ / S １ ≤ 300 The carbon material according to Claim 5.

7. 0.01 μm ２ ≤ S １ ≤ 5.0 μm ２ and optionally, 0.02 μm ２ ≤ S １ ≤ 4.5 μm ２ and / or 2.5 μm ２ ≤ S ２ ≤ 25.0 μm ２ wherein, optionally, 3.0 μm ２ ≤ S ２ ≤ 22.5 μm ２ and / or L≥4 μm, and optionally, 4 μm≤L≤20 μm, The carbon material according to Claim 5 or 6.

8. The area of the pore structure in the outer region of the carbon material is 0.15 μm ２ or less, and optionally 0.10 μm ２ or less, and / or The internal region of the carbon material includes one or more pore structures with an area of 0.15 μm ２ or more, and optionally includes one or more pore structures with an area of 0.15 μm ２ to 2.0 μm ２ or more. The carbon material according to any one of Claims 5 to 7.

9. The carbon material satisfies at least one of the following, (1) The specific surface area of the carbon material is 0.6 m ２ / g to 2.5 m ２ / g, and optionally 0.8 m ２ / g to 2.4 m ２ / g, and (2) The volume distribution particle size Dv50 of the carbon material is 6 μm to 30 μm, and optionally 8 μm to 25 μm, (3) The particle size distribution (Dv90 - Dv10) / Dv50 of the carbon material is 0.90 to 1.50, and optionally 0.90 to 1.45, (4) The graphitization degree of the carbon material is 93% to 98.5%, and optionally 94% to 98%, (5) The topography of the carbon material includes one or more of massive, spherical and substantially spherical. The carbon material according to any one of Claims 1 to 8.

10. The carbon material satisfies at least one of the following, (1) The tap density of the carbon material is 0.8 g / cm ３ to 1.20 g / cm ３ and optionally 0.85 g / cm ３ to 1.18 g / cm ３ and (2) The compression density of the powder of the carbon material at a pressure of 5000 kg is 1.85 g / cm ３ ~ 2.10 g / cm ３ and optionally 1.85 g / cm ３ ~ 2.08 g / cm ３ and (3) The gram capacity of the carbon material is 350 mAh / g to 370 mAh / g, and optionally, 355 mAh / g to 370 mAh / g, The carbon material according to any one of Claims 1 to 9.

11. A method for manufacturing a carbon material, Step 1 of providing a raw material having a plurality of pore structures, Mix the raw materials and the filling material uniformly at a predetermined ratio, and then heat-insulate at the first temperature T １ for the first time t １ to obtain an intermediate in Step 2 The obtained intermediate is maintained at a second temperature T ２ for a second time t ２ to obtain a carbon material in Step 3, and includes The carbon material includes a pore structure, and in the carbon material, the 3R phase and the 2H phase coexist, and 0 < I ３Ｒ（１０１） / I ２Ｈ（００４） ≤ 0.100 is satisfied, where I ３Ｒ（１０１） is the peak intensity of the diffraction peak of the 101 crystal plane of the 3R phase in the X-ray diffraction spectrum of the carbon material, and I ２Ｈ（００４） is the peak intensity of the diffraction peak of the 004 crystal plane of the 2H phase in the X-ray diffraction spectrum of the carbon material. A method for manufacturing a carbon material.

12. The raw material satisfies at least one of the following, (1) The raw material includes natural graphite, and optionally, the natural graphite includes one or more of flake graphite, natural spherical graphite and microcrystalline graphite, (2) The volume distribution particle size Dv50 of the raw material is 6 μm to 30 μm, and optionally 8 μm to 25 μm. (3) The OI value of the raw material is 4 or more, and optionally 4 to 15. The method according to Claim 11.

13. The filling material satisfies at least one of the following: (1) The softening point temperature of the filling material is 105°C to 190°C, and optionally 110°C to 165°C. (2) The coking value of the filling material is 20% to 48%, and optionally 25% to 40%. (3) The volume distribution particle size Dv50 of the filling material is 6 μm or less, and optionally 1 μm to 5 μm. (4) The filling material contains one or more of coal pitch, petroleum pitch, polymer compounds, and resins, and optionally contains petroleum pitch. The method according to claim 11 or 12.

14. The mass ratio of the filling material to the raw material is (10 to 40):100, and optionally (15 to 30):

100. The method according to any one of claims 11 to 13.

15. After uniformly mixing the raw material and the filling material at a predetermined ratio, the temperature increasing process of increasing the temperature to the first temperature T １ is a stepwise temperature increasing process, and optionally includes a first temperature increasing process and a second temperature increasing process The method according to any one of claims 11 to 14.

16. The first heating process is to heat up to 200°C to 300°C, hold the temperature at this temperature for 1 h to 3 h, and / or The second temperature rising process is to raise the temperature to the first temperature T １ and keep the temperature constant for the first time period t at this temperature １ and keep warm The method according to claim 15.

17. The first temperature T １ is 700°C to 1100°C, optionally 850 to 1100°C, and / or The first time t １ is 1 h to 5 h, and optionally 2 h to 4 h The method according to any one of claims 11 to 16.

18. the second temperature T ２ is from 1850 °C to 2650 °C, optionally from 2100 °C to 2480 °C, and / or The second time t ２ is 1.5 h to 6 h, and optionally 2 h to 5 h, The method according to any one of claims 11 to 17.

19. A secondary battery including a negative electrode sheet, wherein the negative electrode sheet includes the carbon material according to any one of claims 1 to 10, or the carbon material manufactured by the method according to any one of claims 11 to 18. Secondary battery.

20. A power consumption device including the secondary battery according to claim 19.

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