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

Abstract

The present application provides a carbon material, a method for manufacturing the same, a secondary battery containing the same, and a power consumption device. The carbon material includes a pore structure, and in the peak pattern of the X-ray diffraction pattern of the carbon material, there are two diffraction peaks within the range where 2θ is 25.5° to 27.5°. The secondary battery according to the present application can have both good cycle performance and kinetic performance.

Description

Technical Field

[0001] This application belongs to the field of battery technology, and specifically relates to a carbon material and its manufacturing method, and a secondary battery and a power consumption device containing the same.

Background Art

[0002] In recent years, secondary batteries have been widely applied in many fields such as energy storage power systems like hydraulic, thermal, wind, 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, severe challenges have been posed to the performance of secondary batteries. 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 it affects the performance of the secondary battery. Currently, the negative electrode active material mainly contains graphite. However, the problem faced in the prior art is that it is difficult for high-capacity graphite to endow a secondary battery with good cycle performance and kinetic performance.

Summary of the Invention

[0003] The objective of this application is to provide a carbon material and its manufacturing method that can endow a secondary battery with good cycle performance and kinetic performance, and a secondary battery and a power consumption device containing the same.

[0004] The first aspect of this application provides a carbon material, the carbon material includes a pore structure, and in the peak pattern of the X-ray diffraction pattern of the carbon material, there are two diffraction peaks within the range where 2θ is 25.5° to 27.5°.

[0005] The inventor of this application discovered in the research process that when the carbon material includes a pore structure and there are two diffraction peaks within the range where 2θ is 25.5° to 27.5° in the peak pattern of the X-ray diffraction pattern of the carbon material, a secondary battery can be endowed with good cycle performance and kinetic performance.

[0006] In any embodiment of the present application, among the two diffraction peaks, the one with a smaller 2θ is taken as the first peak, the one with a larger 2θ is taken as the second peak, and the ratio of the peak intensity of the first peak to the peak intensity of the second peak is 10:90 to 40:60, and optionally 15:85 to 35:65. When the ratio of the peak intensity of the first peak to the peak intensity of the second peak is within the above range, the secondary battery employing the carbon material can have both better cycle performance and kinetic performance, and at the same time can also have a higher energy density.

[0007] In any embodiment of the present application, the carbon material includes a pore structure in which the pore area of one or more pores is 0.1 μm 2 or more, and optionally includes a pore structure in which the pore area of one or more pores is 0.15 μm 2 to 3.0 μm 2 When the carbon material includes a pore structure having the above pore area, the pore structure can reserve an expansion space required for the volume change of the carbon material particles, thereby further reducing the risk of generating a new interface due to the crushing of the carbon material particles, further reducing the occurrence of side reactions, reducing the irreversible capacity loss of the secondary battery, and improving the cycle performance of the secondary battery.

[0008] 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 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. Let the total pore area of the external region be S1 and the total pore area of the internal region be S2, and S2 > S1. When the carbon material further satisfies S2 > S1, the irreversible capacity loss of the secondary battery can be effectively reduced, the capacity exhibition characteristics of the secondary battery can be improved, and the secondary battery can be better equipped with high initial Coulomb efficiency, high energy density, and good cycle performance and kinetic performance.

[0009] In any embodiment of the present application, 1.5 ≤ S2 / S1 ≤ 450, and optionally, 2 ≤ S2 / S1 ≤ 400. When S2 / S1 further satisfies being within the above range, the secondary battery can better combine high initial Coulomb efficiency, high energy density, good cycle performance, and good kinetic performance.

[0010] In any embodiment of the present application, 0.01 μm 2 ≤ S1 ≤ 8.0 μm 2 and optionally, 0.02 μm 2 ≤ S1 ≤ 4.5 μm 2 When the total pore area of the external region of the carbon material is within the above range, on the one hand, the carbon material particles can be given a more stable structure, and the penetration of the electrolyte into the pore structure inside the carbon material particles can be avoided as much as possible, thereby 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. On the other hand, it does not affect the transport performance of active ions and electrons.

[0011] In any embodiment of the present application, 2.5 μm 2 ≤ S2 ≤ 25.0 μm 2 and optionally, 3.0 μm 2 ≤ S2 ≤ 22.5 μm 2 When the total pore area of the internal region of the carbon material is within the above range, on the one hand, a sufficiently stable expansion space is reserved for the volume change of the carbon material particles, reducing the risk of new interfaces being generated due to the crushing of the carbon material particles, reducing 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. On the other hand, the capacity and initial Coulomb efficiency of the carbon material can also be improved.

[0012] In any embodiment of the present application, L ≥ 4 μm, and optionally, 4 μm ≤ L ≤ 20 μm.

[0013] In any embodiment of the present application, the area of the pore structure in the external region of the carbon material is 0.2 μm 2 or less, and optionally 0.1 μm2 The following is achieved. By controlling the area of the pore structure in the outer region of the carbon material to be within the above range, a dense structure can be provided in the outer region of the carbon material, thereby effectively enhancing the structural stability of the carbon material, avoiding as much as possible the penetration of the electrolyte into the pore structure inside the carbon material particles, and further effectively enhancing the cycle performance of the secondary battery.

[0014] In any embodiment of the present application, in the inner region of the carbon material, one or more pore structures with an area of 0.1 μm 2 or more are included, and optionally one or more pore structures with an area of 0.15 μm 2 to 3.0 μm 2 are included. By including pore structures of the above size in the inner region of the carbon material, on the one hand, a sufficiently stable expansion space can be reserved for the volume change of the carbon material particles, reducing the risk of the carbon material particles being crushed, and on the other hand, the tap density of the carbon material can be improved, and the energy density of the secondary battery can also be improved.

[0015] In any embodiment of the present application, the specific surface area of the carbon material is 0.5 m 2 / g to 3.1 m 2 / g, and optionally 0.7 m 2 / g to 2.8 m 2 / g. The carbon material of the present application has a low specific surface area, thereby reducing the consumption of active ions due to the formation of the SEI film and enhancing the initial Coulomb efficiency of the carbon material.

[0016] In any embodiment of the present application, the volume distribution particle size Dv50 of the carbon material is 8.0 μm to 23.0 μm, and optionally 9.0 μm to 22.0 μm. When the volume distribution particle size Dv50 of the carbon material is within the above range, it is advantageous for enhancing the transmission performance of active ions and electrons, thereby further enhancing the cycle performance and kinetic performance of the secondary battery.

[0017] In any embodiment of the present application, (Dv90 - Dv10) / Dv50 of the carbon material is ≤ 1.55, and optionally 0.5 - 1.50. This is advantageous for increasing the consolidation density of the carbon material, thereby further increasing the energy density of the secondary battery, and also advantageous for forming a reasonable pore structure between the particles of the negative electrode film layer, improving the cycle performance and / or kinetic performance of the secondary battery.

[0018] In any embodiment of the present application, the form of the carbon material includes one or more of block shape, spherical shape, and substantially spherical shape. This is advantageous for increasing the consolidation density of the negative electrode plate, and further improving the energy density of the secondary battery.

[0019] In any embodiment of the present application, the powder resistivity of the carbon material at a pressure of 8 Mpa is 0.006 Ω·cm - 0.051 Ω·cm, and optionally 0.010 Ω·cm - 0.040 Ω·cm. When the powder resistivity of the carbon material is within the above range, it is advantageous for enhancing the electron transmission performance, thereby further enhancing the cycle performance and kinetic performance of the secondary battery.

[0020] In any embodiment of the present application, the powder consolidation density of the carbon material at a pressure of 20000 N is 1.70 g / cm 3 ~1.95 g / cm 3 and optionally 1.72 g / cm 3 ~1.92 g / cm 3 When the powder consolidation density of the carbon material is within the above range, it is possible to increase the consolidation density of the negative electrode plate, further improve the energy density of the secondary battery, enhance the active ion and electron transmission performance, and also enhance the cycle performance and kinetic performance of the secondary battery.

[0021] In any embodiment of the present application, the tap density of the carbon material is 0.90 g / cm 3 ~1.35 g / cm 3 and optionally 0.95 g / cm 3 ~1.32 g / cm 3When the tap density of the carbon material is within the above range, the consolidation density of the negative electrode plate can be increased, and furthermore, the energy density of the secondary battery can be improved, which is also advantageous for enhancing the active ion and electron transmission performance and improving the cycle performance and kinetic performance of the secondary battery.

[0022] In any embodiment of the present application, the gram capacity of the carbon material is 350 mAh / g to 372 mAh / g, and optionally 353 mAh / g to 371 mAh / g. When the gram capacity of the carbon material is within the above range, the energy density of the secondary battery can be increased.

[0023] In any embodiment of the present application, the graphitization degree of the carbon material is 91.5% to 98.5%, and optionally 92.5% to 98.0%. When the graphitization degree of the carbon material is within the above range, it is advantageous for enhancing the cycle performance, storage performance and kinetic performance of the secondary battery.

[0024] In any embodiment of the present application, there is no diffraction peak of the 3R phase C(012) crystal plane in the X-ray diffraction pattern of the carbon material. As a result, the carbon material particles further have fewer internal defects, thereby further reducing the irreversible consumption of active ions.

[0025] The second aspect of the present application provides a method for manufacturing a carbon material, the method including: step 1 of providing a raw material having a plurality of pore structures; step 2 of uniformly mixing the raw material and a filling material according to a predetermined ratio, and then holding the mixture at a first temperature T1 for a first time t1 to obtain an intermediate; and step 3 of holding the obtained intermediate at a second temperature T2 for a second time t2 to obtain a carbon material, wherein the carbon material includes a pore structure, and in the peak pattern of the X-ray diffraction pattern of the carbon material, there are two diffraction peaks within the range where 2θ is 25.5° to 27.5°.

[0026] The manufacturing method of the carbon material of the present application has a simple process, high safety, does not require presetting pressure or performing vacuum pumping treatment, and does not necessarily require separately adding a depolymerization step during heat treatment. The carbon material manufactured in the present application has a small volume expansion, high structural stability, a fast diffusion rate of active ions, and can further have a high gram capacity, a high initial Coulombic efficiency, and a small volume change, and can also endow the secondary battery with good cycle performance and kinetic performance. In addition, the secondary battery can also have a high initial Coulombic efficiency and a high energy density.

[0027] 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.

[0028] In any embodiment of the present application, the volume distribution particle size Dv50 of the raw material is 7.5 μm to 23.0 μm, and optionally 9.0 μm to 22.0 μm.

[0029] In any embodiment of the present application, the graphitization degree of the raw material is ≧ 93.0%.

[0030] In any embodiment of the present application, the carbon element content in the raw material is ≧ 98 wt%.

[0031] In any embodiment of the present application, the softening point temperature of the filling material is 120 °C to 300 °C, and optionally 125 °C to 250 °C.

[0032] In any embodiment of the present application, the coking value of the filling material is 25% to 70%, and optionally 30% to 60%.

[0033] 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.

[0034] In any embodiment of the present application, the filling material includes one or more of coal-based asphalt, oil-based asphalt, resin, and polymer material, and optionally includes one or more of coal-based asphalt and oil-based asphalt.

[0035] In any embodiment of the present application, the mass ratio of the filling material to the raw material is 10:90 to 25:75, and optionally 12:88 to 25:75.

[0036] By adjusting one or more parameters such as the type, softening point, coking value, and addition amount of the filling material within the above ranges, on the one hand, it is advantageous to adjust the ratio of the peak intensity of the first peak to the peak intensity of the second peak within an appropriate range, and on the other hand, it is advantageous to adjust the pore size and / or pore content in the external region and internal region of the carbon material within an appropriate range. After the filling material is melted by heat, the viscosity is not high, 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. As a result, problems such as an increase in surface defects of the carbon material particles and an increase in active sites of surface side reactions due to the need to add a depolymerization step can be reduced.

[0037] In any embodiment of the present application, the first temperature T1 is 1000°C to 1400°C, and optionally 1050°C to 1250°C.

[0038] In any embodiment of the present application, the first time t1 is 1 h to 5 h, and optionally 2 h to 4 h.

[0039] In any embodiment of the present application, the temperature is raised to the first temperature T1 at a rate of 1°C / min to 10°C / min, and optionally 1.5°C / min to 5°C / min.

[0040] By adjusting one or more of the heating rate, the first temperature, the first time, etc. to be within the above ranges, it is advantageous for obtaining a carbon material having a required structure, for example, for adjusting the pore size and / or pore content 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 T2 is 2000°C to 2720°C, and optionally 2150°C to 2550°C.

[0042] In any embodiment of the present application, the second time t2 is 1.5 h to 6 h, and optionally 2 h to 5 h.

[0043] By adjusting one or more of the second temperature and the second time to be within the above ranges, in the peak pattern of the X-ray diffraction pattern of the carbon material, two diffraction peaks can be made to be within the range where 2θ is 25.5° to 27.5°, and it is also advantageous to adjust the ratio of the peak intensity of the first peak to the peak intensity of the second peak to be within an appropriate range.

[0044] The third aspect of the present application provides a secondary battery, which includes a negative electrode plate, and the negative electrode plate includes the carbon material of the first aspect of the present application or the carbon material manufactured by the method of the second aspect of the present application.

[0045] The 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 carbon material according to the present application can endow the secondary battery with good cycle performance and kinetic performance, and can also endow the secondary battery with high initial Coulomb efficiency and high energy density. Since the power consumption device of the present application includes the secondary battery according to the present application, it has at least the same advantages as the secondary battery.

Brief Description of the Drawings

[0047] To more clearly explain the technical solutions of the embodiments of this application, the following briefly introduces the drawings that need to be used in the embodiments of this application. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can also be obtained based on these drawings on the premise of not paying creative efforts.

[0048]

Figure 1

Figure 2

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Figure 4

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Embodiments for Carrying Out the Invention

[0049] Hereinafter, with appropriate reference to the drawings, the carbon material of this application, its manufacturing method, and the secondary battery and power consumption device containing it will be specifically described in detail with respect to the disclosed embodiments. However, detailed descriptions that are not necessary may be omitted. For example, detailed descriptions of well-known matters and duplicate descriptions of actually identical structures may be omitted. This is to avoid making the following description unnecessarily long and to make it easily understandable to those skilled in the art. It should be noted that the drawings and the following description are provided to enable those skilled in the art to fully understand this application and do not limit the theme described in the claims.

[0050] The "ranges" disclosed in this application are limited in the form of a lower limit and an upper limit. A given range is limited by selecting one lower limit and one upper limit, and the selected lower limit and upper limit define the boundaries of a specific range. The ranges thus defined may or may not include the end values, and any combination is possible, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, it is understood that ranges of 60 - 110 and 80 - 120 are also conceivable. In addition, if 1 and 2 are listed as the minimum range values and 3, 4, and 5 are listed as the maximum range values, ranges of 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5 are all conceivable. In this application, unless otherwise specified, the numerical range of "a - b" represents a shortened expression of any combination of real numbers from a to b, where both a and b are real numbers. For example, the numerical range "0 - 5" represents that all real numbers between "0 - 5" have already been listed in this specification, and "0 - 5" is only a shortened expression of the combination of these numerical values. Also, when a certain parameter is expressed as an integer ≧ 2, it is equivalent to disclosing that this parameter is, for example, the integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0051] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined with each other to form a new technical solution, and such a technical solution should be considered to be included in the disclosure content of this application.

[0052] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution, and such a technical solution should be considered to be included in the disclosure content of this application.

[0053] Unless otherwise specified, all steps of this application may be performed in order or randomly, and preferably, they are performed in order. For example, the fact that the method includes steps (a) and (b) means that the method may include steps (a) and (b) performed in order, or steps (b) and (a) performed in order. For example, the fact that the method mentioned above may further include step (c) means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0054] Unless otherwise specified, the terms "comprising" and "including" mentioned in this application represent an open type and may also be a closed type. For example, the "comprising" and "including" may further comprise or include other components not listed, or may comprise or include only the components listed.

[0055] Unless otherwise specified, the term "or" in this application is inclusive. For example, the phrase "A or B" represents "A, B, or both A and B". More specifically, any of the conditions where A is true (or exists) and B is false (or does not exist), where A is false (or does not exist) but B is true (or exists), and where both A and B are true (or exist) satisfy "A or B".

[0056] Unless otherwise specified, the terms used in this application have the meanings known to those skilled in the art and are commonly understood.

[0057] Unless otherwise specified, the numerical values of each parameter mentioned in this application can be measured by various test methods commonly used in the art. For example, they can be measured by the test methods described in this application.

[0058] Unless otherwise specified, in this application, the term "active ion" refers to an ion that can be occluded and released reciprocally between the positive electrode and the negative electrode of a secondary battery, including but not limited to lithium ions.

[0059] In this application, the terms "a plurality" and "a plurality of types" mean two or more than two.

[0060] According to the manufacturing process or origin, graphite can be divided into artificial graphite and natural graphite. When manufacturing artificial graphite, generally, it is necessary to go through a high-temperature graphitization process, which has high energy consumption and high cost, so the cost of artificial graphite is high. Natural graphite is derived from nature, so it has the advantage of relatively low cost. In addition, natural graphite further has the advantages of high capacity and / or high bulk density.

[0061] Natural graphite mainly includes flake graphite, natural spherical graphite and microcrystalline graphite. Generally, different from artificial graphite, there are a large number of pores and defects inside and outside the particles of natural graphite. During the first charge of the 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, a low first Coulombic efficiency and poor cycle performance of the secondary battery for the first time. In particular, flake graphite and natural spherical graphite have high crystallinity and high graphitization degree, and their microstructures are often layered structures. Due to such structures, the volume change of natural graphite becomes large during the release and occlusion of active ions, which easily causes the fragmentation of the layered structure of graphite and the fragmentation of particles. After the particles are fragmented, 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, resulting in poor kinetic performance.

[0062] Currently, the performance of natural graphite is mainly improved by particle surface coating treatment and / or particle internal filling treatment.

[0063] The particle surface coating treatment mainly involves uniformly mixing natural graphite and a coating agent (such as asphalt, polymer compounds, etc.), followed by heat treatment to coat the surface of natural graphite with an amorphous carbon layer, and slightly repair the defects on the particle surface. However, during the research process, the inventor of this application found that the amorphous carbon layer coating the surface causes a reduction in the gram capacity and / or tap density of natural graphite, affecting the energy density of the secondary battery. At the same time, the amorphous carbon layer coating the surface cannot effectively prevent the penetration of the electrolyte into the pore structure inside the particles, thereby limiting the improvement effect on the initial Coulomb efficiency and cycle performance of the secondary battery.

[0064] The particle internal filling treatment mainly involves mixing natural graphite and a filler (such as asphalt, polymer compounds, etc.), setting a preset pressure, and filling the filler into the pores inside the particles by means such as vacuum pumping and temperature increase to obtain natural graphite without pores inside the particles. However, during the research process, the inventor of this application found that the carbon filled in large quantities inside the particles reduces both the gram capacity and tap density of natural graphite, affecting the energy density of the secondary battery. At the same time, since all the pores inside the natural graphite particles are filled with carbon, the volume change of natural graphite becomes large during the release and absorption of active ions, making the particles prone to crushing, further causing repeated destruction and reconstruction of the SEI film on the particle surface, increasing the irreversible consumption of active ions, increasing the irreversible capacity loss of the secondary battery, and shortening the service life of the secondary battery. In the prior art, continuously coating the surface of natural graphite without pores inside the above particles with an amorphous carbon layer further reduces the gram capacity and / or tap density of natural graphite, and at this time, the side reaction activity on the particle surface is high, and thus the service life of the secondary battery cannot be effectively improved either.

[0065] Therefore, after modifying natural graphite by the above particle surface coating treatment and / or particle internal filling treatment, 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 increased. However, its improvement effect on the initial Coulomb efficiency of the secondary battery is limited, and it causes a loss of the energy density of the secondary battery. Moreover, it is also difficult for the secondary battery to have good cycle performance and kinetic performance at the same time.

[0066] In view of this, through a large number of studies, the inventor of the present application provides a new type of carbon material that can endow the secondary battery with good cycle performance and kinetic performance at the same time.

[0067] Carbon material The first aspect of the embodiment of the present application provides a carbon material, the carbon material includes a pore structure, and in the peak pattern of the X-ray diffraction pattern of the carbon material, there are two diffraction peaks in the range where 2θ is 25.5° to 27.5°.

[0068] FIG. 1 is the peak pattern of the X-ray diffraction pattern of an embodiment of the carbon material of the present application. As can be seen from FIG. 1, in the range where 2θ is 25.5° to 27.5°, it can be divided into two diffraction peaks (corresponding to the diffraction peaks of the carbon 002 crystal plane). The inventor of the present application discovered in the research process that when the carbon material includes a pore structure and there are two diffraction peaks in the range where 2θ is 25.5° to 27.5° in the peak pattern of the X-ray diffraction pattern of the carbon material, the secondary battery can be endowed with good cycle performance and kinetic performance at the same time. The possible reasons include at least the following points.

[0069] When there are two diffraction peaks within the range where 2θ is between 25.5° and 27.5° in the peak pattern of the X-ray diffraction pattern of the carbon material, the carbon material contains both a highly graphitized crystalline carbon component (for example, crystalline carbon with a graphitization degree ≧ 95%) and a low graphitization degree crystalline carbon component (for example, crystalline carbon with a graphitization degree of 70% - 90%). The low graphitization degree crystalline carbon component may have a large interlayer spacing, which is advantageous for the diffusion of active ions. Therefore, the secondary battery can have good kinetic performance. On the one hand, the highly graphitized crystalline carbon component can endow the carbon material with a high gram capacity and / or a high tap density, thereby increasing the energy density of the secondary battery. On the other hand, it can also endow the carbon material with a stable structure, resulting in low irreversible consumption of active ions during the cycling of the secondary battery, and thus enabling the secondary battery to have good cycle performance.

[0070] The carbon material according to the present application contains a pore structure. In the present application, "the carbon material contains 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 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 reserve the expansion space required for the volume change of the carbon material particles, thereby reducing the risk of generating a new interface due to the crushing of the carbon material particles, further reducing the occurrence of side reactions, and improving the cycle performance of the secondary battery.

[0071] Thereby, the carbon material according to the present application can endow the secondary battery employing it with both good cycle performance and kinetic performance.

[0072] When the carbon material does not contain a pore structure, during the charge and discharge of the secondary battery, the volume change of the carbon material particles is large, resulting in a high risk of generating a new interface due to the crushing of the carbon material particles, many side reactions inside the secondary battery, and poor cycle performance and kinetic performance of the secondary battery.

[0073] When there is only one diffraction peak within the range where 2θ is 25.5° to 27.5° in the peak pattern of the X-ray diffraction pattern of the carbon material, the carbon material mainly has a microstructure of the same crystal phase, that is, the carbon material has only highly graphitized crystalline carbon or lowly graphitized crystalline carbon. When the carbon material has only lowly graphitized crystalline carbon, the gram capacity and / or the tap density of the carbon material are low, and the energy density of the secondary battery is low. When the carbon material has only highly graphitized crystalline carbon, the interlayer spacing of the carbon material is small, which is disadvantageous for the diffusion of active ions, and furthermore, the kinetic performance of the secondary battery is poor, and it is also impossible to endow the secondary battery with good cycle performance and kinetic performance at the same time.

[0074] In some embodiments, among the two diffraction peaks, the one with a smaller 2θ is taken as the first peak, the one with a larger 2θ is taken as the second peak, and the ratio of the peak intensity of the first peak to the peak intensity of the second peak is 10:90 to 40:60, optionally 12:88 to 35:65, 15:85 to 35:65, 15:85 to 30:70.

[0075] The inventor further found in further research that when the ratio of the peak intensity of the first peak to the peak intensity of the second peak is within the above range, the secondary battery employing the carbon material can have both better cycle performance and kinetic performance, and at the same time can also have a higher energy density.

[0076] When the ratio of the peak intensity of the first peak to the peak intensity of the second peak is within the above range, the content of the highly graphitized crystalline carbon component in the carbon material is high, but the content of the lowly graphitized crystalline carbon component is low. This can further stabilize the structure of the carbon material and reduce the irreversible consumption of active ions during the cycling of the secondary battery, thereby endowing the secondary battery with further improved cycle performance and at the same time enabling the secondary battery to have a high energy density.

[0077] And the following situations can be effectively avoided. When the ratio of the peak intensity of the first peak to the peak intensity of the second peak is small, there is little crystalline carbon component with a low degree of graphitization in the carbon material, which may affect the diffusion of active ions and further affect the effect of enhancing the kinetic performance of the secondary battery. When the ratio of the peak intensity of the first peak to the peak intensity of the second peak is large, there is too much crystalline carbon component with a low degree of graphitization in the carbon material, which may result in a high side reaction activity on the surface of the carbon material particles, many side reactions between the electrolyte and the carbon material particles, which may affect the cycle performance of the secondary battery. At the same time, when there is a lot of crystalline carbon component with a low degree of graphitization in the carbon material, the gram capacity and / or tap density of the carbon material will further decrease, which may further reduce the energy density of the secondary battery.

[0078] In the peak pattern of the X-ray diffraction pattern of the carbon material of the present application, the 2θ of the first peak is located between 26.256° and 26.456°, and the 2θ of the second peak is located between 26.509° and 26.569°.

[0079] The peak pattern of the X-ray diffraction pattern of the carbon material is obtained by refining the X-ray diffraction pattern of the carbon material by the Rietveld whole pattern fitting refinement method using Topas software. The 2θ is between 25.5° and 27.5°, corresponding to the peak position of the carbon 002 crystal plane.

[0080] The ratio of the peak intensity of the first peak to the peak intensity of the second peak is the ratio of the integrated area of the first peak to the integrated area of the second peak.

[0081] In some embodiments, the carbon material includes a pore structure with a pore area of 0.1μm 2 or more, and optionally one or more pore areas of 0.15μm 2 ~3.0μm 2It includes a pore structure. The inventor further found in subsequent research that when the carbon material includes a pore structure having the above pore area, the pore structure can reserve the expansion space required for the volume change of the carbon material particles, thereby further reducing the risk of generating new interfaces due to the crushing of the carbon material particles, further reducing the occurrence of side reactions, reducing the irreversible capacity loss of the secondary battery, and improving the cycle performance of the secondary battery.

[0082] 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 in distance 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. Let the total pore area of the external region be S1 and the total pore area of the internal region be S2, and S2 > S1.

[0083] In this application, the total pore area S1 of the external region and the total pore area S2 of the internal region of the carbon material can be obtained by testing with a cross-sectional image of the carbon material.

[0084] In this application, the cross-sectional image of the carbon material includes a cross-sectional image passing through the particle center of the carbon material. "Particle center" refers to the range within a radius of 0.1 μm from the geometric center of the particle towards the particle surface.

[0085] In this 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.

[0086] Figure 2 is a schematic diagram of a cross-sectional image of one particle of the carbon material 100 of this application, and the cross-sectional image passes through the particle center of the carbon material 100. As shown in Figure 2, L represents the length of the short axis of the particle of the carbon material 100, and the region formed by extending 0.25L in distance from the particle surface of the carbon material 100 to the particle interior is the external region 101, and the region inside the external region 101 is the internal region 102.

[0087] A cross-section grinder (for example, the IB-09010 CP type argon ion cross-section grinder of JEOL, Japan) may be employed to produce the cross-section of the carbon material. Then, referring to JY / T010-1996, the cross-section of the carbon material is scanned using a scanning electron microscope (for example, the Sigma 300 type scanning electron microscope of ZEISS, Germany). Finally, the total pore area S1 of the external region and the total pore area S2 of the internal region of the carbon material are calculated using image processing software (for example, AVIZO).

[0088] In further research, the inventors discovered that when the carbon material further satisfies S2 > S1, the carbon material may have the characteristics that the pore content in the internal region is high and / or the pore size is large, and the pore content in the external region is low and / or the pore size is small. The high pore content and / or large pore size in the internal region of the carbon material particles can reserve the 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, further reducing the occurrence of side reactions, reducing the irreversible capacity loss of the secondary battery, and improving the cycle performance and kinetic performance of the secondary battery. The low pore content and / or small pore size in the external region of the carbon material particles can endow the carbon material particles with a more stable structure and avoid the penetration of the electrolyte into the pore structure inside the carbon material particles as much as possible, thereby reducing the occurrence of side reactions and reducing the consumption of active ions due to the formation of the SEI film inside the particles. Furthermore, the first Coulomb efficiency of the carbon material can be increased, and the cycle performance of the secondary battery can be further improved.

[0089] Therefore, when the carbon material further satisfies S2 > S1, the irreversible capacity loss of the secondary battery can be effectively reduced, the capacity performance of the secondary battery can be improved, and the secondary battery can be better equipped with high first Coulomb efficiency, high energy density, and good cycle performance and kinetic performance.

[0090] In some embodiments, 1.5 ≤ S2 / S1 ≤ 450, 2 ≤ S2 / S1 ≤ 400, 2.1 ≤ S2 / S1 ≤ 300, 2.2 ≤ S2 / S1 ≤ 200, 2.3 ≤ S2 / S1 ≤ 100, and 2.4 ≤ S2 / S1 ≤ 80. The inventors have further discovered in additional research that when S2 / S1 further satisfies being within the above ranges, the secondary battery can better have high initial Coulomb efficiency, high energy density, good cycle performance, and kinetic performance.

[0091] In some embodiments, 0.01 μm 2 ≤ S1 ≤ 8.0 μm 2 and optionally, 0.02 μm 2 ≤ S1 ≤ 6.5 μm 2 and 0.02 μm 2 ≤ S1 ≤ 5.0 μm 2 and 0.02 μm 2 ≤ S1 ≤ 4.5 μm 2 and 0.05 μm 2 ≤ S1 ≤ 4.0 μm 2 When the total pore area of the external region of the carbon material is within the above ranges, on the one hand, the carbon material particles can be given a more stable structure, and the penetration of the electrolyte into the pore structure inside the carbon material particles can be avoided as much as possible, thereby 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. On the other hand, it also does not affect the transport performance of active ions and electrons.

[0092] In some embodiments, 2.5 μm 2 ≤ S2 ≤ 25.0 μm 2 and optionally, 3.0 μm 2 ≤ S2 ≤ 22.5 μm 2 and 4.0 μm 2 ≤ S2 ≤ 20 μm 2 and 5.0 μm 2 ≤ S2 ≤ 17.5 μm 2 and 6.0 μm 2 ≤ S2 ≤ 15 μm 2When the total pore area of the internal region of the carbon material is within the above range, on the one hand, a sufficiently stable expansion space is reserved due to the volume change of the carbon material particles, the risk of generating a new interface due to the crushing of the carbon material particles is reduced, the occurrence of side reactions on the surface of the new interface is decreased, and the consumption of active ions due to the formation of the SEI film on the surface of the new interface can be reduced. On the other hand, the capacity and the initial Coulomb efficiency of the carbon material can also be improved.

[0093] 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.

[0094] In some embodiments, the area of the pore structure in the external region of the carbon material is 0.2 μm 2 or less, and optionally 0.1 μm 2 or less. The inventor further discovered in further research that by controlling the size of the area of the pore structure in the external region of the carbon material to be within the above range, a dense structure can be formed in the external region of the carbon material, thereby effectively enhancing the structural stability of the carbon material, avoiding as much as possible the electrolyte from penetrating into the pore structure inside the carbon material particles, and further effectively enhancing the cycle performance of the secondary battery. Of course, this application is not intended to limit that the area of all pore structures in the external region of the carbon material is all 0.2 μm 2 or less. For example, it may be controlled such that the area of 95% or more, optionally 99% or more of the pore structures is 0.2 μm 2 or less, and optionally 0.1 μm 2 or less.

[0095] In some embodiments, the internal region of the carbon material contains one or more pore structures with an area of 0.1 μm 2 or more, and optionally, one or more pore structures with an area of 0.15 μm 2 to 3.0 μm 2It includes a pore structure. The inventor further discovered in additional research that by including a pore structure of the above size in the internal region of the carbon material, on the one hand, sufficient stable expansion space can be reserved for the volume change of the carbon material particles, reducing the risk of the carbon material particles being crushed, and on the other hand, the consolidation density of the carbon material can be improved, and the energy density of the secondary battery can also be improved.

[0096] In some embodiments, there is no diffraction peak of the 3R-phase C(012) crystal plane in the X-ray diffraction pattern of the carbon material. The 3R (Rhombohedral) phase refers to rhombohedral phase crystalline carbon having an ABCABC… stacking structure. There is no diffraction peak of the 3R-phase C(012) crystal plane in the carbon material of this application, whereby the carbon material particles further have fewer internal defects, thereby further reducing the irreversible consumption of active ions. In this application, the 2θ of the diffraction peak of the 3R-phase C(012) crystal plane is in the range of 46° to 47°.

[0097] In some embodiments, the form of the carbon material includes one or more of block-shaped, spherical, and substantially spherical. This is advantageous for increasing the consolidation density of the negative electrode plate and further improving the energy density of the secondary battery.

[0098] In some embodiments, the carbon material includes primary particles. Optionally, the occupancy of the number of the primary particles in the carbon material is ≧50%, for example, it may be 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, thereby giving it high structural stability, reducing the occurrence of side reactions, and also increasing the consolidation density of the negative electrode plate, thereby improving the energy density of the secondary battery.

[0099] In some embodiments, the carbon material may all be primary particles, that is, the occupancy of the number of the primary particles in the carbon material is 100%.

[0100] Both the primary particles and the secondary particles have meanings known in the art. The primary particles refer to non-aggregated particles. The secondary particles refer to aggregated particles in which two or more primary particles are assembled. The primary particles and the secondary particles can be distinguished by a scanning electron microscope (SEM) image.

[0101] In this application, the occupancy rate of the number of primary particles in the carbon material may be tested by the following method. Take any one test sample from the negative electrode film layer, take any plurality of test regions from the test sample, use a scanning electron microscope to obtain images of the plurality of test regions, and count the ratio of the number of carbon material particles in the primary particle form to the total number of carbon material particles in each image, and take the average value of the plurality of statistical results as the occupancy rate of the number of primary particles in the carbon material.

[0102] In some embodiments, the graphitization degree of the carbon material is 91.5% - 98.5%, optionally 92.5% - 98.0%, 93.5% - 98.0%, 94.5% - 98.0%. When the graphitization degree of the carbon material is within the above range, it is advantageous to improve the cycle performance, storage performance and kinetic performance of the secondary battery.

[0103] The graphitization degree of the carbon material has a meaning known in the art and can be tested by adopting equipment and methods known in the art. For example, it may be tested using an X-ray diffractometer (for example, Bruker D8 Discover). In the test, while referring to JIS K 0131-1996 and JB / T 4220-2011, the average interlayer spacing d 002 of the (002) crystal plane in the crystal structure of the carbon material is obtained, and then, according to the formula g = (0.344 - d 002 ) / (0.344 - 0.3354) × 100%, the graphitization degree can be calculated. 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).

[0104] In some embodiments, the specific surface area of the carbon material is 0.5 m 2 / g to 3.1 m 2 / g, and optionally 0.7 m 2 / g to 2.8 m 2 / g. The carbon material of the present application has a low specific surface area, which can reduce the consumption of active ions due to the formation of the SEI film and increase the initial Coulomb efficiency of the carbon material.

[0105] The specific surface area of the carbon material is a meaning known in the art and can be measured by adopting equipment and methods known in the art. For example, referring to GB / T 19587-2017, the nitrogen gas adsorption specific surface area analysis test method can be adopted for testing and calculated by using the BET (Brunauer Emmett Teller) method. Here, the nitrogen gas adsorption specific surface area analysis test can be performed by a Tri-Star 3020 specific surface area pore size analyzer of Micromeritics, USA.

[0106] In some embodiments, the volume distribution particle size Dv50 of the carbon material is 8.0 μm to 23.0 μm, and optionally 9.0 μm to 22.0 μm.

[0107] When the volume distribution particle size Dv50 of the carbon material is within the above range, it is advantageous to enhance the transmission performance of active ions and electrons, thereby further enhancing the cycle performance and kinetic performance of the secondary battery.

[0108] In some embodiments, (Dv90 - Dv10) / Dv50 of the carbon material is ≤ 1.55, and optionally 0.5 to 1.50. When (Dv90 - Dv10) / Dv50 of the carbon material is within the above range, it is advantageous to increase the compaction density of the carbon material, thereby further increasing the energy density of the secondary battery. It is also advantageous to form a reasonable pore structure between the particles of the negative electrode film layer, improving the cycle performance and / or kinetic performance of the secondary battery.

[0109] The volume distribution particle sizes Dv10, Dv50, and Dv90 of the carbon material have meanings known in this field. They respectively represent the particle sizes corresponding when the cumulative volume distribution percentage of the material reaches 10%, 50%, and 90%, and can be measured by adopting equipment and methods known in this field. For example, referring to GB / T 19077-2016 laser diffraction particle size distribution method, it can be easily measured using a laser particle size analyzer. The test equipment may be the Mastersizer 3000 type laser particle size analyzer of Malvern Instruments Limited, UK.

[0110] In some embodiments, the powder resistivity of the carbon material at a pressure of 8 Mpa is 0.006 Ω·cm to 0.051 Ω·cm, and optionally 0.010 Ω·cm to 0.040 Ω·cm. When the powder resistivity of the carbon material is within the above range, it is advantageous for enhancing the electron transmission performance, thereby further enhancing the cycle performance and kinetic performance of the secondary battery.

[0111] The powder resistivity of the carbon material has a meaning known in this field and can be measured by adopting equipment and methods known in this field. For example, referring to GB / T 30835-2014, it can be measured by the four-probe method using a powder resistivity tester (such as Suzhou Lattice ST2722 or Sansi Zongheng UTM7305). An exemplary test method is as follows. Weigh a certain amount of the test sample powder to be tested and place it in a special mold, and by setting the test pressure, the powder resistivity at different pressures can be obtained. In this application, the test pressure may be set to 8 Mpa.

[0112] In some embodiments, the powder compaction density of the carbon material at a pressure of 20000 N is 3 ~1.95 g / cm 3 and optionally 1.72 g / cm 3 ~1.92 g / cm 3 is.

[0113] When the powder compaction density of the carbon material is within the above range, the compaction density of the negative electrode plate can be increased, and further the energy density of the secondary battery can be improved, which is also beneficial to enhancing the active ion and electron transmission performance and improving the cycle performance and kinetic performance of the secondary battery.

[0114] In the present application, the powder compaction density of the carbon material has the meaning known in the art and can be measured by adopting the equipment and methods known in the art. For example, referring to GB / T 24533-2009, it may be measured with an electronic pressure tester (for example, it may be a UTM7305 type electronic pressure tester). An exemplary test method is as follows. Weigh 1 g of carbon material powder, add it to a mold with a bottom area of 1.327 cm 2 and apply a pressure of 2000 kg (corresponding to 20000 N), hold the pressure for 30 s, then release the pressure and maintain it for 10 s, and record and calculate the powder compaction density of the carbon material under a pressure of 20000 N.

[0115] In some embodiments, the tap density of the carbon material is 0.90 g / cm 3 to 1.35 g / cm 3 and optionally 0.95 g / cm 3 to 1.32 g / cm 3 When the tap density of the carbon material is within the above range, the compaction density of the negative electrode plate can be increased, and further the energy density of the secondary battery can be improved, which is also beneficial to enhancing the active ion and electron transmission performance and improving the cycle performance and kinetic performance of the secondary battery.

[0116] The tap density of the carbon material has the meaning known in the art and can be measured by adopting the equipment and methods known in the art. For example, referring to GB / T 5162-2006, it can be measured using a powder tap density tester. As the test equipment, Dandong BET BT-301 may be adopted.

[0117] In some embodiments, the gram capacity of the carbon material is 350 mAh / g to 372 mAh / g, and optionally 353 mAh / g to 371 mAh / g. When the gram capacity of the carbon material is within the above range, the energy density of the secondary battery can be increased.

[0118] The gram capacity of the carbon material has the meaning known in the art and can be tested by adopting methods known in the art. An exemplary test method is as follows. A carbon material sample, a styrene-butadiene rubber (SBR) as an adhesive, a sodium carboxymethyl cellulose (CMC) as a thickener, and a carbon black as a conductive agent are sufficiently stirred and mixed in an appropriate amount of deionized water as a 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 of a negative electrode current collector and dried in an oven for use. Ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) are mixed at a volume ratio of 1:1:1 to obtain an organic solvent, and LiPF6 is dissolved in the above organic solvent to produce an electrolyte solution with a concentration of 1 mol / L. Then, a metal lithium sheet is used as a counter electrode, a polyethylene (PE) film is used as a separator, and it is assembled into a CR2430 type button cell in a glove box protected by argon gas. At 25 °C, first, the above-produced button cell is discharged at a constant current of 0.15 mA to 0.005 V, left standing for 5 min, and then discharged at a constant current of 10 μA to 0.005 V, and the discharge capacity of the first cycle of the button 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 button cell is recorded. The ratio of the charge capacity of the button cell to the mass of the carbon material sample is the gram capacity of the carbon material.

[0119] Manufacturing method The second aspect of the embodiments of the present application provides a manufacturing method of a carbon material capable of manufacturing the carbon material of the first aspect of the embodiments of the present application.

[0120] The method for manufacturing the carbon material includes: Step 1 of providing a raw material having a plurality of pore structures; Step 2 of uniformly mixing the raw material and a filling material according to a predetermined ratio, and then keeping the temperature at a first temperature T1 for a first time t1 to obtain an intermediate; and Step 3 of keeping the obtained intermediate at a second temperature T2 for a second time t2 to obtain a carbon material. Here, the carbon material includes a pore structure, and in the peak pattern of the X-ray diffraction pattern of the carbon material, there are two diffraction peaks within the range where 2θ is 25.5° to 27.5°.

[0121] 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 further optionally includes natural spherical graphite.

[0122] In the present application, "natural spherical graphite" refers to natural graphite having a spherical or substantially spherical shape, and it is not necessary to control all natural graphite particles into an ideal spherical shape. In some embodiments, natural spherical graphite with required particle size and morphology can be obtained by performing pretreatment on flake graphite. Optionally, the pretreatment includes processes such as crushing, classification, spheroidization, and purification.

[0123] In some embodiments, the form of the raw material includes one or more of spherical and substantially spherical.

[0124] In some embodiments, the volume distribution particle size Dv50 of the raw material is 7.5 μm to 23.0 μm, and optionally 9.0 μm to 22.0 μm. When the volume distribution particle size of the raw material is within the above range, it is advantageous for subsequent filling treatment.

[0125] In some embodiments, the graphitization degree of the raw material is ≧93.0%, and optionally ≧93.5%, ≧94.0%, ≧94.5%, ≧95.0%. This is advantageous for the carbon material to have a high gram capacity.

[0126] In some embodiments, the carbon element content in the raw material is ≧98 wt%.

[0127] In some embodiments, the softening point temperature of the filler is 120°C to 300°C, optionally 120°C to 250°C, 120°C to 225°C, 120°C to 200°C, 120°C to 180°C, 120°C to 170°C, 120°C to 160°C, 125°C to 250°C, 125°C to 225°C, 125°C to 200°C, 125°C to 180°C, 125°C to 170°C, 125°C to 160°C.

[0128] During the research process, the inventors found that when the softening point temperature of the filler is within the above range, it is advantageous to adjust the pore size and / or pore content in the external and internal regions of the carbon material to be within an appropriate range, and it is also advantageous to adjust the ratio of the peak intensity of the first peak to the peak intensity of the second peak to be within an appropriate range. And the following situations can be effectively avoided. When the softening point temperature of the filler is too high, it is difficult for the filler to flow into and fill the pore structure of the raw material, thereby being unable to effectively modify the defects inside the particles, and being unable to effectively prevent the electrolyte from seeping into the pore structure inside the obtained carbon material particles, further affecting the initial Coulomb efficiency and cycle performance of the secondary battery. When the softening point temperature of the filler is too low, the filler contains many small molecule substances, and these small molecule substances are easy to volatilize by heat. Therefore, it is easy for the filler to flow into and fill the pore structure of the raw material. However, when heat treatment is performed in step 2 and / or step 3, the volatilization of the small molecule substances in the filler causes the actual residual carbon in the filling area to be unable to effectively fill the pore structure of the raw material, unable to achieve an effective filling effect, or the actual residual carbon in the filling area has many pore structures, and at the same time, it is impossible to reduce the consumption of active ions due to the formation of the SEI film and the irreversible capacity loss of the secondary battery, and it also affects the cycle performance, kinetic performance and / or storage performance of the secondary battery.

[0129] In some embodiments, the coking value of the filling material is 25% to 70%, optionally 30% to 60%. The inventor has found that during the research process, when the coking value of the filling material is within the above range, it is advantageous to adjust the pore size and / or pore content in the external and internal regions of the carbon material to be within an appropriate range, and it is also advantageous to adjust the ratio of the peak intensity of the first peak to the peak intensity of the second peak to be within an appropriate range.

[0130] The coking value of the filling material has the meaning known in the art and can be measured by adopting the equipment and methods known in the art. For example, it can be measured with reference to GB / T 8727-2008.

[0131] In some embodiments, the volume distribution particle size Dv50 of the filling material is 6 μm or less, optionally 1 μm to 6 μm, 2 μm to 5 μm, 3 μm to 5 μm. This is advantageous for the filling material to fill the pore structure of the raw material, and is also advantageous for improving the dispersion uniformity between the filling material and the raw material.

[0132] In some embodiments, the filling material includes one or more of coal-based asphalt, oil-based asphalt, resin, and polymer material, optionally including one or more of coal-based asphalt and oil-based asphalt.

[0133] In some embodiments, the mass ratio of the filling material to the raw material is 10:90 to 25:75, optionally 12:88 to 25:75. This is advantageous for adjusting the pore size and / or pore content in the external and internal regions of the carbon material to be within an appropriate range, and is also advantageous for adjusting the ratio of the peak intensity of the first peak to the peak intensity of the second peak to be within an appropriate range. And the following situations can be effectively avoided. 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. At this time, the filling material cannot effectively modify the defects inside the particles, and the electrolyte cannot be effectively prevented from penetrating into the pore structure inside the obtained carbon material particles. Furthermore, it affects the initial Coulombic efficiency and cycle performance of the secondary battery. When the mass ratio of the filling material to the raw material is too small, the ratio of the peak intensity of the first peak to the peak intensity of the second peak tends to be small, which also affects the kinetic performance of the secondary battery. When the mass ratio of the filling material to the raw material is too large, it is likely to cause the pore structure inside the raw material to be completely filled. At this time, the volume change of the obtained carbon material is large, and 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 remains on the surface of the particles. At this time, the particles are more likely to aggregate, not only adding a depolymerization process, but also reducing the gram capacity and / or tap density of the obtained carbon material. When the mass ratio of the filling material to the raw material is too large, the ratio of the peak intensity of the first peak to the peak intensity of the second peak tends to be large, which results in a high content of the crystalline carbon component with a low degree of graphitization in the obtained carbon material, thereby affecting the energy density and cycle performance of the secondary battery.

[0134] By adjusting one or more parameters such as the type of filling material, softening point, coking value, and addition amount within the above ranges, on the one hand, it is advantageous to adjust the ratio of the peak intensity of the first peak to the peak intensity of the second peak within an appropriate range. On the other hand, it is advantageous to adjust the pore size and / or pore content in the external region and internal region of the carbon material within an appropriate range. After the filling material melts due to heat, its viscosity is not high, it maintains good fluidity, it is difficult for raw material particles to adhere, and agglomeration of raw material particles in the subsequent manufacturing process can be reduced. As a result, problems such as an increase in surface defects of carbon material particles and an increase in active sites for surface side reactions due to the need to add a depolymerization step can be reduced.

[0135] In some embodiments, in step 2, the first temperature T1 is 1000°C to 1400°C, optionally 1000°C to 1350°C, 1000°C to 1300°C, 1050°C to 1350°C, 1050°C to 1300°C, 1050°C to 1250°C. The inventor has discovered in the process of research that when the first temperature is within the above range, it is advantageous to adjust the pore size and / or pore content in the external region and internal region of the carbon material within an appropriate range.

[0136] In some embodiments, the first time t1 is 1 h to 5 h. For example, the first time t1 may be within a range composed of any numerical value such as 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 t1 is 2 h to 4 h. The inventor has discovered in the process of research that when the first time is within the above range, it is advantageous to adjust the pore size and / or pore content in the external region and internal region of the carbon material within an appropriate range.

[0137] In some embodiments, in step 2, the temperature is raised to the first temperature T1 at a rate of 1 °C / min to 10 °C / min. For example, the heating rate may be any value within the range composed of 1.5 °C / min, 2 °C / min, 3 °C / min, 4 °C / min, 5 °C / min, 6 °C / min, 7 °C / min, 8 °C / min, 9 °C / min, 10 °C / min or any number above. Optionally, the heating rate is 1 °C / min to 8 °C / min, 1.5 °C / min to 6 °C / min, 1.5 °C / min to 5 °C / min, 1.5 °C / min to 4 °C / min.

[0138] In the process of research, the inventor found that when the heating rate is within the above range, it is advantageous to adjust the pore size and / or pore content in the external region and the internal region of the carbon material to be within an appropriate range. And the following situations can be effectively avoided. When the heating rate is too high, the filling material may carbonize on the surface of the raw material particles, making it difficult for the filling material to fill the pore structure of the raw material. As a result, the defects inside the particles cannot be effectively modified, and the electrolyte cannot be effectively prevented from soaking into the pore structure inside the obtained carbon material particles. Furthermore, it affects the initial Coulomb efficiency and cycle performance of the secondary battery. When the heating rate is too low, the filling material easily flows and fills all the pore structures of the raw material. During the release and absorption of active ions, the volume change of the carbon material becomes large, and the particles are easily crushed. This increases the consumption of active ions due to the formation of the SEI film, increases the irreversible capacity loss of the secondary battery, and at the same time affects the cycle performance and kinetic performance of the secondary battery.

[0139] In some embodiments, in step 2, the heat treatment can be carried out in a box furnace, an intermediate frequency furnace, a roller hearth kiln, a rotary kiln or a pusher kiln.

[0140] In some embodiments, in step 2, the heat treatment atmosphere may be a shield gas atmosphere. The shield 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, etc. to be within the above ranges, it is advantageous to obtain a carbon material with the required structure. For example, it is advantageous to adjust the pore size and / or pore content in the external region and the internal region of the carbon material to be within an appropriate range.

[0142] In some embodiments, the second temperature T2 is 2000°C to 2720°C. For example, it may be a range composed of any one of the numerical values such as 2050°C, 2100°C, 2150°C, 2200°C, 2250°C, 2300°C, 2350°C, 2400°C, 2450°C, 2500°C, 2550°C, 2600°C, 2650°C, 2700°C or above. Optionally, the second temperature T2 is 2050°C to 2550°C, 2100°C to 2550°C, 2150°C to 2550°C, 2150°C to 2500°C, 2150°C to 2400°C.

[0143] The inventors have found that during the research process, when the second temperature is within the above range, in the peak pattern of the X-ray diffraction pattern of the carbon material, two diffraction peaks can be obtained within the range where 2θ is 25.5° to 27.5°, and it is also advantageous to adjust the ratio of the peak intensity of the first peak to the peak intensity of the second peak to be within an appropriate range. And the following situations can be effectively avoided. When the second temperature is too low, the ratio of the peak intensity of the first peak to the peak intensity of the second peak is large, and the content of components with low graphitization degree and / or amorphous carbon (such as soft carbon, etc.) in the obtained carbon material is high, which increases the defect content of the carbon material and affects the initial Coulomb efficiency, gram capacity and cycle performance of the carbon material. When the second temperature is too high, in the peak pattern of the X-ray diffraction pattern of the carbon material, there are no two diffraction peaks within the range where 2θ is 25.5° to 27.5°, or the ratio of the peak intensity of the first peak to the peak intensity of the second peak is small. At this time, it is disadvantageous for the rapid release and absorption of active ions, which affects the kinetic performance of the secondary battery.

[0144] In some embodiments, the second time t2 is 1.5 h to 6 h. For example, the second time t2 may be a range composed of any value 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 t2 is 2 h to 5 h.

[0145] In the process of research, the inventor found that when the second temperature is within the above range, in the peak pattern of the X-ray diffraction pattern of the carbon material, two diffraction peaks can be obtained within the range where 2θ is 25.5° to 27.5°, and it is also advantageous to adjust the ratio of the peak intensity of the first peak to the peak intensity of the second peak within an appropriate range. And the following situations can be effectively avoided. When the second time is too short, the ratio of the peak intensity of the first peak to the peak intensity of the second peak is large, which increases the defect content of the carbon material and affects the initial Coulomb efficiency, gram capacity and cycle performance of the carbon material. When the second time is too long, in the peak pattern of the X-ray diffraction pattern of the carbon material, there are no two diffraction peaks within the range where 2θ is 25.5° to 27.5°, or the ratio of the peak intensity of the first peak to the peak intensity of the second peak is small. At this time, it is disadvantageous for the rapid release and absorption of active ions, which affects the kinetic performance of the secondary battery.

[0146] In some embodiments, in step 3, the heat treatment can be performed in a medium-frequency furnace, a box-type graphitization furnace, an Acheson graphitization furnace, a continuous graphitization furnace or an intrasilial graphitization furnace.

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

[0148] By adjusting one or more of the second temperature and the second time so that they are within the above range, two diffraction peaks can be obtained within the range where 2θ is between 25.5° and 27.5° in the peak pattern of the X-ray diffraction pattern of the carbon material, and it is also advantageous to adjust the ratio of the peak intensity of the first peak to the peak intensity of the second peak so that it is within an appropriate range.

[0149] The method for manufacturing the carbon material of the present application has a simple process, high safety, does not require presetting of pressure or performing a vacuum pumping process, and does not require separately adding a depolymerization step during the heat treatment. The carbon material manufactured in the present application has a small volume expansion, high structural stability, a high diffusion rate of active ions, and can also have a high gram capacity, a high initial Coulombic efficiency and a small volume change, and can endow the secondary battery with good cycle performance and kinetic performance. In addition, the secondary battery can also have a high initial Coulombic efficiency and a high energy density.

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

[0151] Secondary battery A 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, a secondary battery includes a positive electrode plate, a negative electrode plate, an electrolyte, and the like. In the charge and discharge process of the secondary battery, active ions are reciprocally occluded and released between the positive electrode plate and the negative electrode plate, and the electrolyte plays a role of conducting active ions between the positive electrode plate and the negative electrode plate. This application is not particularly limited to the type of the electrolyte and can be selected according to the demand. For example, the electrolyte may be selected from at least one of a solid electrolyte and a liquid electrolyte (i.e., an electrolytic solution). In a secondary battery employing an electrolytic solution and some secondary batteries employing a solid electrolyte, a separator may be further included, and the separator is installed between the positive electrode plate and the negative electrode plate and serves as an isolation.

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

[0154] In some embodiments, the negative electrode film layer includes a carbon material of the first aspect of the embodiment of the present application or a carbon material manufactured by the method described in the second aspect of the embodiment of the present application. Thereby, the secondary battery can have both good cycle performance and kinetic performance.

[0155] In some embodiments, the negative electrode film layer may further include other negative electrode active materials in addition to the above carbon materials. In some embodiments, the other negative electrode active materials include, but are not limited to, one or more of common 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 silicon alone, silicon oxide, silicon carbon composite, silicon nitride composite, and silicon alloy materials. The tin-based materials may include one or more of tin alone, tin oxide, and tin alloy materials.

[0156] In some embodiments, the negative electrode film layer optionally further includes a negative electrode conductive agent. The present application does not particularly limit the type of the negative electrode conductive agent. For example, the negative electrode conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0157] In some embodiments, the negative electrode film layer optionally further includes a negative electrode adhesive. The present application does not particularly limit the type of the negative electrode adhesive. For example, the negative electrode adhesive may include one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic resin (for example, 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 optionally further includes other auxiliary agents. For example, the other auxiliary agents may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, and the like.

[0159] In some embodiments, the negative electrode current collector may employ a metal foil sheet or a composite current collector. As an example of the metal foil sheet, a copper foil may be employed. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. 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] Generally, the negative electrode film layer is formed by applying a negative electrode slurry onto a negative electrode current collector and then undergoing drying and cold pressing. Generally, the negative electrode slurry is formed by dispersing a negative electrode active material, an optional conductive agent, an optional adhesive, and other optional auxiliaries in a solvent and uniformly stirring them. The solvent may be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.

[0161] The negative electrode plate does not exclude other additional functional layers other than the negative electrode film layer. For example, in some embodiments, the negative electrode plate described in the present application further includes a conductive undercoating (e.g., composed of a conductive agent and an adhesive) sandwiched between the negative electrode current collector and the negative electrode film layer and installed on the surface of the negative electrode current collector. In some embodiments, the negative electrode plate described in the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0162] [Positive electrode plate] In some embodiments, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer installed 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 its own thickness direction, and the positive electrode film layer is installed on either one or both of the two facing surfaces of the positive electrode current collector.

[0163] The positive electrode current collector may employ a metal foil sheet or a composite current collector. As an example of the metal foil sheet, an aluminum foil may be employed. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. 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 generally includes a positive electrode active material, an optional adhesive, and an optional conductive agent. The positive electrode film layer is generally formed by applying a positive electrode slurry onto the positive electrode current collector and then undergoing drying and cold pressing. The positive electrode slurry is generally formed by dispersing a positive electrode active material, an optional conductive agent, an optional adhesive, and any other components in a solvent and uniformly stirring them. 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), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and 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] The positive electrode active material may employ a positive electrode active material for secondary batteries well known in the art.

[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 oxides include, but are not limited to, 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 one or more of their respective modified compounds. Examples of the lithium-containing phosphates include, but are not limited to, 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 one or more of their respective modified compounds.

[0167] In some embodiments, in order to further improve 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 and their modified compounds having the formula Li a Ni b Co c M d O e A f where 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 LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NCM333), LiNi 0.5 Co 0.2 Mn 0.3O2 (NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), LiNi 0.85 Co 0.15 Al 0.05 O2 may contain one or more of LiFePO4 and LiMnPO4.

[0169] In this application, the modified compound of the above positive electrode active material may be obtained by doping and / or surface coating modification of the positive electrode active material.

[0170] [Electrolyte] 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 specifically limited and can be selected according to actual needs.

[0172] When the secondary battery of this application is a lithium-ion battery, for example, the electrolyte salt may contain one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluoro(oxalato)phosphate (LiDFOP), and lithium tetrafluoro(oxalato)phosphate (LiTFOP).

[0173] The type of the solvent is not specifically 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), ethyl methyl sulfone (EMS), and diethyl sulfone (ESE).

[0174] In some embodiments, the electrolyte may further optionally contain 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 an additive that can improve any performance of the secondary battery, such as an additive that improves the overcharge performance of the secondary battery, an additive that improves the high-temperature performance of the secondary battery, an additive that improves the low-temperature power performance of the secondary battery, and the like.

[0175] [Separator] This application is not particularly limited to the type of the separator, and any known separator having a porous structure with good chemical stability and mechanical stability may 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 plate, the separator, and the negative electrode plate can be used to manufacture an electrode assembly by a winding process or a stacking process.

[0178] In some embodiments, the secondary battery may include an exterior body. This exterior body may be used for packaging the above electrode assembly and electrolyte.

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

[0180] This application is not particularly limited to the shape of the secondary battery, which may be cylindrical, square, or any other arbitrary shape. FIG. 3 shows a secondary battery 5 having a square structure as an example.

[0181] In some embodiments, as shown in FIG. 4, the exterior body may include a case 51 and a cover plate 53. The case 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates surround to form an accommodation cavity. The case 51 has an opening communicating with the accommodation cavity, and the cover plate 53 is provided to cover the opening to close the accommodation cavity. The positive electrode plate, the negative electrode plate, and the separator can form an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is packaged in the accommodation cavity. 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 can be adjusted according to demand.

[0182] The manufacturing method of the secondary battery of the present application is a known one. In some embodiments, a secondary battery can be formed by assembling a positive electrode plate, a separator, a negative electrode plate, and an electrolytic solution. As an example, the positive electrode plate, the separator, and the negative electrode plate can form an electrode assembly by a winding process or a lamination process, place the electrode assembly in an outer package, inject the electrolytic solution after drying, and through processes such as vacuum packaging, standing, formation, and shaping, a secondary battery can be obtained.

[0183] In some embodiments of the present application, the secondary battery according to 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 can be adjusted based on the application and capacity of the battery module.

[0184] FIG. 5 is a schematic diagram of a battery module 4 as an example. As shown in FIG. 5, in the battery module 4, a plurality of secondary batteries 5 may be sequentially arranged along the length direction of the battery module 4. Of course, they may be arranged according to any other method. Further, the plurality of secondary batteries 5 may be fixed with a fastener.

[0185] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of secondary batteries 5 are accommodated in the accommodation space.

[0186] In some embodiments, the above battery module may further be assembled into a battery pack, and the number of battery modules included in the battery pack can be adjusted based on the application and capacity of the battery pack.

[0187] FIG. 6 and FIG. 7 are schematic views of a battery pack 1 as an example. As shown in FIGS. 6 and 7, the battery pack 1 may include a battery box and a plurality of battery modules 4 installed in the battery box. The battery box includes an upper housing 2 and a lower housing 3. The upper housing 2 is provided to cover the lower housing 3 and forms a sealed space for accommodating the battery module 4. The plurality of battery modules 4 may be arranged in the battery box according to an arbitrary method.

[0188] Power consumption device The present application further provides a power consumption device, and the power consumption device includes at least one of the secondary battery, battery module or 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, and may also be used as an energy storage unit of the power consumption device. The power consumption device may be a mobile device (such as a mobile phone, tablet computer, notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, hybrid electric vehicle, plug-in hybrid electric vehicle, electric bicycle, electric scooter, electric golf cart, electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto.

[0189] As the power consumption device, a secondary battery, a battery module or a battery pack can be selected according to the requirements in use.

[0190] FIG. 8 is a schematic view of a power consumption device as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirements for high power and high energy density of the power consumption device, a battery pack or a battery module can be adopted.

[0191] Another example of the power consumption device may be a mobile phone, a tablet computer, a notebook computer, etc. The power consumption device is generally required to be lightweight, and a secondary battery can be adopted as a power source.

[0192] Example The following examples describe the content disclosed in this application in more detail. These examples are only used for illustrative purposes, and it is obvious to those skilled in the art that various modifications and changes can be made within the scope of the content disclosed in this application. Unless otherwise specified, all parts, percentages, and ratio values reported in the following examples are based on mass. All reagents used in the examples can be purchased commercially or obtained by synthesis using common methods, and further treatment is not required and they can be used directly. And all the instruments used in the examples can be purchased commercially.

[0193] Example 1 (1) Production of carbon material Step 1: Mechanical grinding, classification, spheroidization, and purification treatment were performed on 100-mesh flaky graphite to obtain natural spherical graphite. Its volume distribution particle size Dv50 was 15 μm, the carbon element content was 99.9%, and the graphitization degree was 95%.

[0194] Step 2: The obtained natural spherical graphite and petroleum asphalt (softening point temperature is 150 °C, volume distribution particle size Dv50 is 5 μm, and coking value is 35%) were mixed in a VC mixer at a mass ratio of 80:20 for 30 min. The mixed material was put into a crucible and heated to 1100 °C at a rate of 2 °C / min in a box furnace and held for 2 h. After completion, it was naturally cooled to room temperature to obtain an intermediate.

[0195] Step 3: The obtained intermediate was put into an Acheson graphitization furnace, heated to 2400 °C and held for 3 h. After completion, demagnetization and screening were performed to obtain a carbon material.

[0196] (2) Production of button-type battery (half-cell) The above-prepared carbon material, styrene-butadiene rubber (SBR) as an adhesive, sodium carboxymethyl cellulose (CMC) as a thickener, and carbon black as a conductive agent were sufficiently stirred and mixed in an appropriate amount of solvent deionized water at a mass ratio of 96.2:1.8:1.2:0.8 to form a uniform negative electrode slurry. The negative electrode slurry was uniformly coated on the surface of the copper foil of the negative electrode current collector and dried in an oven for use. Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed at a volume ratio of 1:1:1 to obtain an organic solvent, and LiPF6 was dissolved in the above organic solvent to produce an electrolytic solution with a concentration of 1 mol / L. Then, a metal lithium sheet was used as the counter electrode, a polyethylene (PE) film was used as the separator, and it was assembled into a CR2430 type button cell in a glove box protected by argon gas.

[0197] (3) Fabrication of secondary battery (full battery) The above-prepared carbon material, carbon black (Super P) as a conductive agent, styrene-butadiene rubber as an adhesive, and sodium carboxymethyl cellulose as a thickener were sufficiently stirred and mixed in an appropriate amount of solvent deionized water at a weight ratio of 96:1:1:2 to form a negative electrode slurry. The negative electrode slurry was applied to both surfaces of the copper foil of the negative electrode current collector, and after drying and cold pressing, a negative electrode plate was obtained.

[0198] LiNi 0.5 Co 0.2 Mn 0.3 O2 (NCM523), conductive carbon black, and polyvinylidene fluoride were mixed at a weight ratio of 96:2.5:1.5, an appropriate amount of solvent NMP was added, and it was uniformly stirred to obtain a positive electrode slurry. The positive electrode slurry was applied to both surfaces of the aluminum foil of the positive electrode current collector, and after drying and cold pressing, a positive electrode plate was obtained.

[0199] A polypropylene film with a thickness of 12 μm was adopted as a separator and arranged in sequence together with the above-produced positive electrode plate and negative electrode plate. The separator was positioned between the positive electrode plate and the negative electrode plate to perform an isolation function. Then, it was wound to obtain an electrode assembly. The electrode assembly was placed in an outer package, dried, and then the same electrolyte as that for the manufacture of the above button battery was injected. After passing through processes such as vacuum packaging, standing, forming, and capacity measurement, a secondary battery was obtained.

[0200] Comparative Example 1 The manufacturing methods of half-cells and full-cells are similar to those of Example 1, but the difference lies in the manufacturing process of the carbon material.

[0201] Mechanical grinding, classification, spheroidization, and purification treatments were performed on 100-mesh flaky graphite to obtain natural spherical graphite. Its volume distribution particle size Dv50 was 15 μm, the carbon element content was 99.9%, and the graphitization degree was 95%.

[0202] Comparative Example 2 The manufacturing methods of half-cells and full-cells are similar to those of Example 1, but the difference lies in the manufacturing process of the carbon material.

[0203] Mechanical grinding, classification, spheroidization, and purification treatments were performed on 100-mesh flaky graphite to obtain natural spherical graphite. Its volume distribution particle size Dv50 was 15 μm, the carbon element content was 99.9%, and the graphitization degree was 95%. The obtained natural spherical graphite and petroleum asphalt (softening point temperature of 150 °C, volume distribution particle size Dv50 of 5 μm, and coking value of 35%) were mixed in a VC mixer at a mass ratio of 80:20 for 30 min. Then, the mixed material was graphitized at 3200 °C for 10 h and cooled to room temperature after completion to obtain a carbon material.

[0204] Comparative Example 3 The manufacturing methods of half-cells and full-cells are similar to those of Example 1, but the difference lies in the manufacturing process of the carbon material.

[0205] The 100-mesh flaky graphite was mechanically crushed, classified, spheroidized, and purified to obtain natural spherical graphite. Its volume distribution particle size Dv50 was 15 μm, the carbon element content was 99.9%, and the graphitization degree was 95%. The obtained natural spherical graphite and petroleum asphalt (softening point temperature of 150 °C, volume distribution particle size Dv50 of 5 μm, and coking value of 35%) were mixed in a VC mixer at a mass ratio of 80:20 for 30 min. Then, the mixed material was carbonized at 1200 °C for 3 h and cooled to room temperature after completion to obtain a carbon material.

[0206] Comparative Example 4 The manufacturing methods of the half-cell and the full-cell are similar to those of Example 1, but the difference lies in the manufacturing process of the carbon material.

[0207] The 100-mesh flaky graphite was mechanically crushed, classified, spheroidized, and purified to obtain natural spherical graphite. Its volume distribution particle size Dv50 was 15 μm, the carbon element content was 99.9%, and the graphitization degree was 95%.

[0208] The obtained natural spherical graphite and petroleum asphalt (with a softening point temperature of 150 °C, a volume distribution particle size Dv50 of 5 μm, and a coking value of 35%) were mixed in a VC mixer for 30 min. Then, the mixed material was put into a reaction kettle, and a method of gradually increasing the temperature of the reaction kettle was adopted, with a heating rate of 2 °C / min. While heating, the reaction kettle was maintained in an isokinetic stirring state and heated to 190 °C. The pressure of the reaction kettle was set to -0.1 Mpa and kept warm for 2 h. After the heat preservation was completed, the reaction kettle was heated to 650 °C and kept warm for 2 h. Then, the reaction kettle was cooled to about 160 °C, and petroleum asphalt was gradually added into the reaction kettle. The mass ratio of the added amount of petroleum asphalt this time to the previous petroleum asphalt was set to 1:1. Then, the reaction kettle was heated to 190 °C again, the pressure of the reaction kettle was set to -0.1 Mpa, and it was kept warm for 2 h. After the heat preservation was completed, the reaction kettle was heated to 650 °C and kept warm for 2 h. Then, cooling was carried out by the method of condensation and cooling. Finally, the material processed in the above process was heat-treated at 1200 °C for 3 h, and the heat-treated sample was pulverized and sieved to obtain a carbon material without pores inside.

[0209] Example 2 - 21 The manufacturing methods of half cells and full cells are similar to those in Example 1, but as a difference, the manufacturing process parameters of the carbon material have been adjusted, specifically as shown in Table 1.

[0210]

Table 1

[0211] Performance Test (1) X-ray Diffraction Test of Carbon Material The carbon material was tested using an X-ray diffractometer. In the test, the phase structure of the carbon material may be obtained with reference to JIS K 0131 - 1996 and JB / T 4220 - 2011. The X-ray diffraction pattern of the carbon material was refined by Topas software and the Rietveld whole pattern fitting refinement method.

[0212] In Table 2, 2θ of the first peak is located between 26.256° and 26.456°, and 2θ of the second peak is located between 26.509° and 26.569°. The ratio of the peak intensity of the first peak to the peak intensity of the second peak is the ratio of the integrated area of the first peak to the integrated area of the second peak. As the test equipment, a Bruker D8 Discover X-ray diffractometer may be adopted. In the X-ray diffraction analysis test, the test conditions may be as follows. For the carbon material, a sample is prepared by the flat sample preparation method, a copper target is used as the anode target, CuKα ray is used as the radiation source, the voltage is 40 KV, the current is 40 mA, the anti-scattering slit is 1 mm, the scanning 2θ angle range is 20° to 80°, the step size is 0.01671°, the time length of each step is 0.24 s, and the scanning speed is 4° / min.

[0213] (2) Test of the total pore area in the external region and the internal region of the carbon material After uniformly mixing the sample and the carbon material powder using an adhesive and applying it to a copper foil, it is dried at 60 °C for 30 min in preparation for use. The sample is cut into a size of 6 mm × 6 mm, adhered to the sample stage of a CP type argon ion cross-section polishing machine, and the sample is cut using a plasma beam to obtain a cross-section of the carbon material, and the cross-section of the carbon material particles passes through the center of the carbon material particles. The test equipment may be an IB-09010 CP type argon ion cross-section polishing machine manufactured by JEOL, Japan.

[0214] The cross-section of the carbon material is scanned using a scanning electron microscope. It can be tested with reference to JY / T010-1996. The test equipment may be a Sigma 300 type scanning electron microscope manufactured by ZEISS, Germany.

[0215] The region formed by extending 0.25L from the particle surface of the carbon material to the particle interior 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 short axis of the carbon material particles. The total pore area S1 of the external region of the carbon material and the total pore area S2 of the internal region of the carbon material were calculated using image processing software. The image processing software may be AVIZO.

[0216] (3) Maximum charge rate test of the secondary battery At 25 °C, the secondary battery was discharged at a constant current to the lower cut-off voltage (corresponding to 0% SOC) at a rate of 1C. Then, it was charged at a constant current to the upper cut-off voltage (corresponding to 100% SOC) at a rate of 1C, and subsequently charged at a constant voltage until the current reached 0.05C. At this time, the secondary battery was in a fully charged state. After allowing the fully charged secondary battery to stand for 5 minutes, it was 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 was the actual capacity of the secondary battery at a rate of 1C, denoted as C0. The secondary battery was charged at a constant current to the upper cut-off voltage (corresponding to 100% SOC) at a rate of xC0 (representing the gradient charge rate, which may be, for example, 1C0, 1.05C0, 1.1C0, 1.15C0, 1.2C0...), and then charged at a constant voltage until the current reached 0.05C0. After standing for 5 minutes, the secondary battery was disassembled, and the lithium deposition situation on the surface of the negative electrode plate was observed. If no lithium was deposited on the surface of the negative electrode plate, the charge rate was increased and the test was performed again until lithium was deposited on the surface of the negative electrode plate. The maximum charge rate at which no lithium was deposited on the surface of the negative electrode plate was recorded.

[0217] (4) Cycle performance test of the secondary battery At 25°C, the above-prepared secondary battery was charged at a constant current to the upper cut-off voltage (corresponding to 100% SOC) at 1C, and then charged at a constant voltage until the current reached 0.05C. After standing for 5 minutes, the secondary battery was discharged at a constant current to the lower cut-off voltage (corresponding to 0% SOC) at 1C, and the discharge capacity at this time was recorded, which was taken as the discharge capacity of the first cycle. The secondary battery was subjected to a cycle charge-discharge test by the above method, and the discharge capacity after each cycle was recorded. The capacity retention rate (%) of the secondary battery at 25°C after 2500 cycles = discharge capacity after 2500 cycles / discharge capacity of the first cycle × 100%.

[0218]

Table 2

[0219] Parameters such as the specific surface area, volume distribution particle size, powder resistivity, and powder compaction density of the carbon materials produced in Examples 1 to 21 are all within the ranges described in the specification of this application, and there is no diffraction peak of the 3R phase C(012) crystal plane in the X-ray diffraction pattern of the carbon materials.

[0220] As can be seen from the test results in Table 2, when the peak pattern of the X-ray diffraction pattern of the carbon material satisfies that there are two diffraction peaks within the range where 2θ is 25.5° to 27.5°, the battery can have good cycle performance and kinetic performance. In addition, when the ratio of the peak intensity of the first peak to the peak intensity of the second peak is further 10:90 to 40:60, and optionally 15:85 to 35:65, the battery can better combine good cycle performance and kinetic performance, and can also have a high energy density.

[0221] As can be further seen from the test results in Table 2, when the carbon material particles further satisfy S2 > S1, optionally satisfy 1.5 ≤ S2 / S1 ≤ 450, and further optionally satisfy 2 ≤ S2 / S1 ≤ 400, the overall performance of the battery is further improved. At this time, the carbon material particles further have the characteristics that the pore content in the internal region is large and / or the pore size is large, and the pore content in the external region is small and / or the pore size is small. The pore structure in the internal region of the carbon material can reserve the expansion space required for the volume change of the carbon material particles, thereby reducing the risk of generating a new interface due to the crushing of the carbon material particles, further reducing the occurrence of side reactions, and reducing the irreversible capacity loss of the battery. The pore content in the external region of the carbon material is small and / or the pore size is small, thereby making the carbon material particles have a more stable structure and avoiding as much as possible the penetration of the electrolyte into the pore structure inside the carbon material particles, thereby reducing the occurrence of side reactions and reducing the consumption of active ions due to the formation of the SEI film inside the particles. Thereby, the carbon material further satisfying the above structural characteristics can further enhance the overall performance of the battery.

[0222] In the peak pattern of the X-ray diffraction pattern of the carbon materials manufactured in Comparative Examples 1 to 4, there is only one diffraction peak within the range where 2θ is 25.5° to 27.5°, and none of them can have both good cycle performance and kinetic performance in the battery.

[0223] In Comparative Example 1, untreated natural spherical graphite was used as the carbon material. There are many pores inside the carbon material particles, and in the peak pattern of the X-ray diffraction pattern of the carbon material, there is only one diffraction peak within the range where 2θ is 25.5° to 27.5°. As can be seen from the test results in Table 2, the cycle performance and kinetic performance of the battery manufactured thereby are both poor.

[0224] The carbon material produced in Comparative Example 2 has a carbon layer coating formed on the surface of natural spherical graphite. Since the heat treatment temperature is high and the heat treatment time is long, the graphitization degree of the carbon layer is close to that of the natural spherical graphite substrate. As a result, in the peak pattern of the X-ray diffraction pattern of the carbon material, there is only one diffraction peak within the range where 2θ is 25.5° to 27.5°, and at this time, the interlayer spacing of the carbon material is small. As can be seen from the test results in Table 2, the kinetic performance of the battery produced thereby is poor. Moreover, the coating layer only exists on the surface of natural spherical graphite, and an effective filling effect has not been achieved, and it cannot effectively prevent the penetration of the electrolyte into the pore structure inside the particles, which further causes a limited improvement effect on the cycle performance of the battery.

[0225] The carbon material produced in Comparative Example 3 has a carbon layer coating formed on the surface of natural spherical graphite. Since the heat treatment temperature is low, at this time, the main component of the coating layer is amorphous carbon, and different crystalline carbon phases with different graphitization degrees do not appear in the carbon material. And in the peak pattern of the X-ray diffraction pattern of the carbon material, there is only one diffraction peak within the range where 2θ is 25.5° to 27.5°. Moreover, the coating layer only exists on the surface of natural spherical graphite, and an effective filling effect has not been achieved, and it cannot effectively prevent the penetration of the electrolyte into the pore structure inside the particles, which further causes a limited improvement effect on the cycle performance and kinetic performance of the battery.

[0226] When producing the carbon material in Comparative Example 4, the filling material was filled into all the pore structures inside the natural spherical graphite particles by a vacuuming method. Since the heat treatment temperature was low, at this time, there was a large amount of amorphous carbon inside and / or on the surface of the carbon material particles, and different crystalline carbon phases with different graphitization degrees did not appear in the carbon material. There was only one diffraction peak in the peak pattern of the X-ray diffraction pattern of the carbon material within the range where 2θ was 25.5° to 27.5°. At this time, there was no pore structure inside the obtained carbon material particles. As a result, during the release and occlusion of active ions, the volume change of the carbon material became large, the particles were easily crushed, and furthermore, the improvement effect on the cycle performance and kinetic performance of the battery was limited.

[0227] It should be noted that this application is not limited to the above embodiments. The above embodiments are illustrative. Embodiments that have substantially the same configuration as the technical idea within the scope of the technical solution of this application and exhibit the same effects are all included within the technical scope of this application. In addition, within the scope not departing from the spirit of this application, various modifications that can be conceived by those skilled in the art to the embodiments, and other forms constructed by combining some components in the embodiments are also included within the scope of this application.

[0228] In the drawings, the drawings are not necessarily drawn to scale. The description of the reference numerals is as follows. 1 Battery pack, 2 Upper housing, 3 Lower housing, 4 Battery module, 5 Secondary battery, 51 Case, 52 Electrode assembly, 53 Cover plate, 100 Carbon material, 101 External region, 102 Internal region.

Claims

1. A carbon material, wherein the carbon material includes a pore structure, and in the peak pattern of the X-ray diffraction pattern of the carbon material, there are two diffraction peaks within the range where 2θ is 25.5° to 27.5°.

2. Among the two diffraction peaks, the one with a smaller 2θ is defined as the first peak, and the one with a larger 2θ is defined as the second peak. And the ratio of the peak intensity of the first peak to the peak intensity of the second peak is 10:90 to 40:60, and optionally 15:85 to 35:

65. The carbon material according to Claim 1.

3. The carbon material includes a pore structure in which one or more pore areas are 0.1 μm ２ or more, and optionally includes a pore structure in which one or more pore areas are 0.15 μm ２ to 3.0 μm ２ The carbon material according to Claim 1 or 2.

4. 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 into 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 , and optionally, 1.5 ≤ S ２ / S １ ≤ 450, and 2 ≤ S ２ / S １ ≤ 400. The carbon material according to any one of Claims 1 to 3.

5. 0.01 μm ２ ≤ S １ ≤ 8.0 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 and optionally, 3.0 μm ２ ≤S ２ ≤22.5 μm ２ and / or The carbon material according to claim 4, wherein L ≥ 4 μm, and optionally, 4 μm ≤ L ≤ 20 μm.

6. The area of the pore structure in the outer region of the carbon material is 0.2 μm ２ or less, and optionally 0.1 μm ２ or less, and / or In the inner region of the carbon material, there is included a pore structure having an area of 0.1 μm ２ or more, and optionally, there is included a pore structure having an area of 0.15 μm ２ to 3.0 μm ２ The carbon material according to claim 4 or 5.

7. The carbon material is (1) the specific surface area of the carbon material is 0.5 m ２ / g to 3.1 m ２ / g, and optionally 0.7 m ２ / g to 2.8 m ２ / g, (2) the volume distribution particle size Dv50 of the carbon material is 8.0 μm to 23.0 μm, and optionally 9.0 μm to 22.0 μm, (3) (Dv90 - Dv10) / Dv50 of the carbon material is ≤ 1.55, and optionally 0.5 to 1.50, (4) the carbon material satisfies at least one of the following: the form of the carbon material includes one or more of block shape, spherical shape, and substantially spherical shape. The carbon material according to any one of claims 1 to 6.

8. The carbon material is (1) the powder resistivity of the carbon material at 8 MPa pressure is 0.006 Ω·cm to 0.051 Ω·cm, and optionally 0.010 Ω·cm to 0.040 Ω·cm, (2) The powder consolidation density of the carbon material under a pressure of 20,000 N is 1.70 g / cm ３ to 1.95 g / cm ３ and optionally 1.72 g / cm ３ to 1.92 g / cm ３ and (3) The tap density of the carbon material is 0.90 g / cm ３ to 1.35 g / cm ３ and optionally 0.95 g / cm ３ to 1.32 g / cm ３ and (4) The gram capacity of the carbon material is 350 mAh / g to 372 mAh / g and optionally 353 mAh / g to 371 mAh / g, and (5) The graphitization degree of the carbon material is 91.5% to 98.5% and optionally 92.5% to 98.0%, and (6) The carbon material according to any one of claims 1 to 7, satisfying at least one of the following: there is no diffraction peak of the 3R phase C(012) crystal plane in the X-ray diffraction pattern of the carbon material.

9. A method for manufacturing a carbon material, comprising: step 1 of providing a raw material having a plurality of pore structures; step 2 of uniformly mixing the raw material and a filling material according to a predetermined ratio and then holding the mixture at a first temperature T １ for a first time t １ to obtain an intermediate; and step 3 of holding the obtained intermediate at a second temperature T ２ for a second time t ２ to obtain a carbon material, wherein the carbon material includes a pore structure, and in the peak pattern of the X-ray diffraction pattern of the carbon material, there are two diffraction peaks within a range where 2θ is 25.5° to 27.5°.

10. The raw material is (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, and (2) The volume distribution particle size Dv50 of the raw material is 7.5 μm to 23.0 μm, optionally 9.0 μm to 22.0 μm, and (3) The graphitization degree of the raw material is ≧ 93.0%, and (4) The method according to claim 9, satisfying at least one of the carbon element content in the raw material being ≧ 98 wt%.

11. The filling material is (1) The softening point temperature of the filling material is 120°C to 300°C, optionally 125°C to 250°C, and (2) The coking value of the filling material is 25% to 70%, optionally 30% to 60%, and (3) The volume distribution particle size Dv50 of the filling material is 6 μm or less, optionally 1 μm to 5 μm, and (4) The method according to claim 9 or 10, satisfying at least one of the filling material containing one or more of coal-based asphalt, oil-based asphalt, resin, and polymer material, optionally containing one or more of coal-based asphalt and oil-based asphalt.

12. The mass ratio of the filling material to the raw material is 10:90 to 25:75, optionally 12:88 to 25:75, according to any one of claims 9 to 11.

13. The first temperature T １ is 1000°C to 1400°C, optionally 1050°C to 1250°C, and / or The first time t １ is 1 h to 5 h, optionally 2 h to 4 h, and / or The second temperature T ２ is 2000°C to 2720°C, optionally 2150°C to 2550°C, and / or The second time t ２ is 1.5 h to 6 h, optionally 2 h to 5 h, according to any one of claims 9 to 12.

14. The method according to any one of claims 9 to 13, wherein the temperature is raised to the first temperature T at a rate of 1 °C / min to 10 °C / min, optionally 1.5 °C / min to 5 °C / min. １

15. A secondary battery comprising a negative electrode plate, wherein the negative electrode plate contains the carbon material according to any one of claims 1 to 8 or the carbon material produced by the method according to any one of claims 9 to 14.

16. An electric power consuming device comprising the secondary battery according to claim 15.

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