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

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 more specifically relates to carbon materials, methods for producing the same, and secondary batteries and power consumption devices containing the same. [Background technology]

[0002] In recent years, secondary batteries have been widely applied in numerous fields, including energy storage and power systems such as hydroelectric, thermal, wind, and solar power plants, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. As the range of applications for secondary batteries expands, so do the challenges to their performance. For example, secondary batteries are required to possess a combination of various properties such as energy density, kinetic performance, and service life. The negative electrode active material is a crucial component of secondary batteries and affects their performance. Currently, negative electrode active materials mainly consist of graphite; however, a problem faced in conventional technology is that it is difficult to achieve good cycle performance and kinetic performance in secondary batteries using high-capacity graphite. [Overview of the Initiative]

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

[0004] A first aspect of this application provides a carbon material comprising a pore structure, wherein the peak pattern of the X-ray diffraction pattern of the carbon material has two diffraction peaks in the range where 2θ is between 25.5° and 27.5°.

[0005] In the course of research, the inventors of this application discovered that if a carbon material contains a porous structure and the X-ray diffraction pattern of the carbon material has two diffraction peaks within the range of 2θ to 27.5°, then a secondary battery can be made to have both good cycle performance and dynamic performance.

[0006] In any embodiment of this application, of the two diffraction peaks, the one with a smaller 2θ is designated as the first peak, and the one with a larger 2θ is designated as the second peak. 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 combine better cycle performance and dynamic performance while also having a higher energy density.

[0007] In any embodiment of this application, the carbon material has one or more pore areas of 0.1 μm². 2 The pore structure includes the above-mentioned features, and optionally one or more pores have a pore area of ​​0.15 μm². 2 ~3.0μm 2 The carbon material includes a pore structure having the above-mentioned pore area. When the carbon material includes a pore structure having the above-mentioned pore area, the pore structure can reserve expansion space necessary for volume changes of carbon material particles, thereby further reducing the risk of new interfaces being formed due to the fragmentation of carbon material particles, further reducing the occurrence of side reactions, reducing irreversible capacity loss of secondary batteries, and improving the cycle performance of secondary batteries.

[0008] In any embodiment of this application, the carbon material includes an outer region and an inner region located inside the outer region, wherein the outer region refers to a region extending 0.25 L from the particle surface of the carbon material into the particle interior, where L is the length of the short axis of the carbon material particle, S1 is the total pore area of ​​the outer region, S2 is the total pore area of ​​the inner region, and S2 > S1. If the carbon material further satisfies S2 > S1, it can effectively reduce irreversible capacity loss of the secondary battery, improve the capacity performance characteristics of the secondary battery, and enable the secondary battery to better combine high initial Coulomb efficiency, high energy density, and good cycle performance and dynamic 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 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 electrolyte can be avoided from infiltrating 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 carbon material particles. On the other hand, it will 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 generated by 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 size of the area of ​​the pore structure in the external region of the carbon material to fall within the above range, a dense structure can be created in the external region of the carbon material. This effectively enhances the structural stability of the carbon material, prevents the electrolyte from seeping into the pore structure inside the carbon material particles as much as possible, and further effectively improves the cycle performance of the secondary battery.

[0014] In any embodiment of this application, one or more areas of 0.1 μm are present in the internal region of the carbon material. 2 The pore structure includes the above-mentioned features, and one or more areas are optionally 0.15 μm². 2 ~3.0μm 2 The material includes a pore structure of the above size. By incorporating a pore structure of the above size into the internal region of the carbon material, it is possible to reserve a sufficiently stable expansion space for volume changes of the carbon material particles and reduce the risk of the carbon material particles breaking down, and on the other hand, it is possible to improve the compaction density of the carbon material and improve the energy density of the secondary battery.

[0015] In any embodiment of this application, the specific surface area of ​​the carbon material is 0.5 m². 2 / g~3.1m 2 / g, and optionally 0.7m 2 / g~2.8m 2 The value is / g. The carbon material of this application has a low specific surface area, which reduces the consumption of active ions during SEI film formation and improves the initial Coulomb efficiency of the carbon material.

[0016] In any embodiment of this 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 improving the transmission performance of active ions and electrons, thereby further improving the cycle performance and dynamic performance of the secondary battery.

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

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

[0019] In any embodiment of this application, 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 improving electron transmission performance, thereby further enhancing the cycle performance and dynamic performance of the secondary battery.

[0020] In any embodiment of this application, the powder compaction density of the carbon material at a pressure of 20,000 N is 1.70 g / cm³. 3 ~1.95g / cm 3 Therefore, it is optionally 1.72 g / cm³. 3 ~1.92g / cm 3 Therefore, if the compaction density of the carbon material powder is within the above range, the compaction density of the negative electrode plate can be increased, further improving the energy density of the secondary battery, which is advantageous in enhancing the active ion and electron transmission performance, and improving the cycle performance and dynamic performance of the secondary battery.

[0021] In any embodiment of this application, the tap density of the carbon material is 0.90 g / cm³. 3 ~1.35g / cm 3 Therefore, optionally 0.95 g / cm³ 3 ~1.32 g / cm³ 3Therefore, if the tap density of the carbon material is within the above range, the compaction density of the negative electrode plate can be increased, further improving the energy density of the secondary battery, which is advantageous in enhancing the active ion and electron transmission performance, and improving the cycle performance and dynamic performance of the secondary battery.

[0022] In any embodiment of this 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 this application, the degree of graphitization of the carbon material is 91.5% to 98.5%, and optionally 92.5% to 98.0%. When the degree of graphitization of the carbon material is within the above range, it is advantageous for improving the cycle performance, storage performance, and kinetic performance of the secondary battery.

[0024] In any embodiment of this application, the X-ray diffraction pattern of the carbon material lacks diffraction peaks of the 3R phase C(012) crystal plane. This allows the carbon material particles to have fewer internal defects, thereby further reducing the irreversible consumption of active ions.

[0025] A second aspect of this application provides a method for producing a carbon material, the method comprising: step 1 providing a raw material having a plurality of pore structures; step 2 uniformly mixing the raw material and a filler material in a predetermined ratio, then maintaining the mixture at a first temperature T1 for a first time t1 to obtain an intermediate; and step 3 maintaining the obtained intermediate at a second temperature T2 for a second time t2 to obtain a carbon material, wherein the carbon material includes pore structures, and the peak pattern of the X-ray diffraction pattern of the carbon material has two diffraction peaks in the range where 2θ is between 25.5° and 27.5°.

[0026] The method for manufacturing carbon materials described in this application is simple, highly safe, does not require pre-setting pressure or vacuum treatment, and does not require an additional depolymerization step during heat treatment. The carbon material manufactured in this application exhibits small volume expansion, high structural stability, and a fast diffusion rate of active ions. Furthermore, it can combine high gram capacity, high initial Coulomb efficiency, and small volume change, and can provide secondary batteries with good cycle performance and kinetic performance. In addition, the secondary batteries can also combine high initial Coulomb efficiency and high energy density.

[0027] In any embodiment of this application, the raw material comprises natural graphite, which optionally comprises one or more of flake graphite, natural spheroidal graphite, and microcrystalline graphite.

[0028] In any embodiment of this 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 this application, the degree of graphitization of the raw material is ≥93.0%.

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

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

[0032] In any embodiment of this application, the caulking value of the filler material is 25% to 70%, and optionally 30% to 60%.

[0033] In any embodiment of this application, the volume distribution particle size Dv50 of the filler material is 6 μm or less, and optionally 1 μm to 5 μm.

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

[0035] In any embodiment of this application, the mass ratio of the filler 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 of filler material, softening point, coking value, and amount added to fall within the above range, it is advantageous, on the one hand, to adjust the ratio of the peak intensity of the first peak to the peak intensity of the second peak to fall within an appropriate range, and on the other hand, to adjust the pore size and / or pore content in the external and internal regions of the carbon material to fall within an appropriate range. Furthermore, after the filler material is melted by heat, it is possible to maintain good fluidity without high viscosity and without causing adhesion of raw material particles, thereby reducing aggregation of raw material particles in subsequent manufacturing processes. This reduces problems such as an increase in surface defects in carbon material particles and an increase in active sites for surface side reactions, which would otherwise necessitate the addition of a depolymerization step.

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

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

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

[0040] By adjusting one or more of the heating rate, first temperature, first time, etc., to fall within the above range, it is advantageous to manufacture and obtain a carbon material of the required structure, for example, by adjusting the pore dimensions and / or pore content in the external and internal regions of the carbon material to fall within an appropriate range.

[0041] In any embodiment of this application, the second temperature T2 is 2000°C to 2720°C, and optionally 2150°C to 2550°C.

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

[0043] By adjusting one or more of the second temperature and second time to fall within the above range, it is possible to ensure that the peak pattern of the X-ray diffraction pattern of the carbon material has two diffraction peaks within the range where 2θ is between 25.5° and 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 fall within an appropriate range.

[0044] A third aspect of this application provides a secondary battery comprising a negative electrode plate, the negative electrode plate comprising a carbon material of the first aspect of this application or a carbon material manufactured by the method of the second aspect of this application.

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

[0046] The carbon material according to this application can provide secondary batteries with good cycle performance and kinetic performance, and can also provide secondary batteries with high initial Coulomb efficiency and high energy density. Since the power consumption device according to this application includes a secondary battery according to this application, it has at least the same advantages as the aforementioned secondary battery. [Brief explanation of the drawing]

[0047] To more clearly explain the technical concept of the embodiments of this application, the following is a brief introduction to the drawings that may be used in the embodiments of this application. Obviously, the drawings described below represent only a few embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without expending any creative effort.

[0048] [Figure 1] This is the peak pattern of the X-ray diffraction pattern of one embodiment of the carbon material of this application. [Figure 2] This is a schematic diagram of a cross-sectional image of one of the particles of the carbon material of this application. [Figure 3] This is a schematic diagram of one embodiment of the secondary battery of this application. [Figure 4] This is an exploded schematic diagram of one embodiment of the secondary battery of the present application. [Figure 5] This is a schematic diagram of one embodiment of the battery module of this application. [Figure 6] This is a schematic diagram of one embodiment of the battery pack in this application. [Figure 7] Figure 6 is a schematic exploded view of an embodiment of the battery pack shown. [Figure 8] This is a schematic diagram of one embodiment of a power consumption device in which the secondary battery of this application is used as a power source. [Modes for carrying out the invention]

[0049] The following describes in detail embodiments specifically disclosing the carbon material and its manufacturing method, as well as secondary batteries and power consumption devices containing the same, with appropriate reference to the drawings. However, unnecessary detailed explanations may be omitted. For example, detailed explanations of well-known matters and redundant explanations of structures that are actually the same may be omitted. This is to avoid making the following explanation unnecessarily long and to make it easily understandable to those skilled in the art. The drawings and the following explanation are provided to enable those skilled in the art to fully understand this application and do not limit the topics described in the claims.

[0050] The “range” disclosed in this application is limited in the form of a lower limit and an upper limit, and a given range is limited by selecting one lower limit and one upper limit, which define the boundary of a particular range. The range thus limited may or may not include the endpoints, and any combination is possible, that is, any lower limit can be combined with any upper limit to form a range. For example, if the ranges 60-120 and 80-110 are listed for a particular parameter, it is understood that the ranges 60-110 and 80-120 can also be assumed. Furthermore, if the minimum range values ​​are listed as 1 and 2, and the maximum range values ​​are listed as 3, 4 and 5, then the ranges 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5 can all be assumed. In this application, unless otherwise specified, the numerical range “a-b” represents an abbreviated expression for any combination of real numbers a-b, where a and b are both real numbers. For example, the numerical range "0 to 5" indicates that all real numbers between "0 to 5" have already been listed in this specification, and "0 to 5" is simply an abbreviated representation of combinations of these numbers. Also, when a parameter is described as an integer ≥ 2, it is equivalent to disclosing that this parameter is, for example, an integer such as 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 to form new technical concepts, and such technical concepts should be considered to be included in the disclosures of this application.

[0052] Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical concepts, and such technical concepts should be considered to be included in the disclosures of this application.

[0053] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, the fact that the method includes steps (a) and (b) means that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, the fact that the method described 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 “includes” and “inclusion” as used in this application may be open or closed. For example, “includes” and “inclusion” may mean that other components not listed may be included or inclusion, or that only the listed components may be included or inclusion.

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

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

[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, 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 intercepted and released by moving back and forth between the positive and negative electrodes of a secondary battery, and includes, but is not limited to, lithium ions.

[0059] In this application, the terms "multiple" and "multiple types" mean two or more types.

[0060] Depending on the manufacturing process or origin, graphite can be divided into artificial graphite and natural graphite. Artificial graphite generally requires a high-temperature graphitization process, which is energy-intensive and costly, resulting in a higher cost for artificial graphite. Natural graphite, being derived from nature, has the advantage of being relatively inexpensive. Furthermore, natural graphite has the advantages of high volume and / or high compaction density.

[0061] Natural graphite mainly consists of flake graphite, natural spheroidal graphite, and microcrystalline graphite. Unlike artificial graphite, natural graphite particles generally have a large number of pores and defects both inside and outside the particles. During the initial charging of a secondary battery, many side reactions occur between the electrolyte and the particle surface and internal pores. This results in high initial irreversible capacity loss, low initial Coulomb efficiency, and poor cycle performance. In particular, flake graphite and natural spheroidal graphite have high crystallinity and high graphitization, and their microstructure is often layered. This structure causes large volume changes in natural graphite during the release and absorption of active ions, which easily leads to the fragmentation of the layered structure and particle fragmentation. After particle fragmentation, the exposed fresh surface continues to react with the electrolyte, further increasing the irreversible capacity loss of the secondary battery. Furthermore, natural graphite has high anisotropy, resulting in slow diffusion of active ions, which also degrades its kinetic performance.

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

[0063] Particle surface coating treatment primarily involves uniformly mixing natural graphite with a coating agent (e.g., asphalt, polymer compounds, etc.) and then heat-treating it to coat the surface of the natural graphite with an amorphous carbon layer, thereby slightly repairing defects on the particle surface. However, in the course of research, the inventors of this application discovered that the amorphous carbon layer coating the surface causes a reduction in the gram capacity and / or compaction density of the natural graphite, affecting the energy density of the secondary battery. At the same time, the amorphous carbon layer coating the surface fails to effectively prevent the electrolyte from seeping into the pore structure inside the particle, thereby limiting the improvement in the initial Coulomb efficiency and cycle performance of the secondary battery.

[0064] The particle internal filling process mainly involves mixing natural graphite with a filler (e.g., asphalt, polymer compounds, etc.), pre-setting the pressure, and using methods such as vacuuming and heating to fill the pores inside the particles with the filler, thereby obtaining natural graphite without internal pores. However, the inventors of this application discovered in the course of their research that the large amount of carbon packed inside the particles reduces both the gram capacity and compaction density of the natural graphite, affecting the energy density of the secondary battery. At the same time, because all the pores inside the natural graphite particles are filled with carbon, the volume change of the natural graphite during the release and storage of active ions becomes large, making the particles more prone to fragmentation. Furthermore, it causes repeated destruction and reconstruction of the SEI film on the particle surface, further increasing the irreversible consumption of active ions, increasing the irreversible capacity loss of the secondary battery, and shortening the lifespan of the secondary battery. In conventional technology, the surface of natural graphite, which has no pores inside the particles, is further coated with an amorphous carbon layer. This further reduces the gram capacity and / or compaction density of the natural graphite, and at the same time, the side reaction activity of the particle surface is high, which prevents an effective improvement in the lifespan of the secondary battery.

[0065] Therefore, after modifying natural graphite by the above-mentioned particle surface coating treatment and / or particle internal filling treatment, it is possible to reduce the irreversible capacity loss of the secondary battery to a certain extent and improve the initial Coulomb efficiency of the secondary battery. However, the improvement effect on the initial Coulomb efficiency of the secondary battery is limited, and it causes a loss of energy density in the secondary battery. Furthermore, it is difficult for the secondary battery to have both good cycle performance and kinetic performance.

[0066] In light of this, the inventors of this application, through extensive research, provide a novel carbon material that enables secondary batteries to possess both good cycle performance and dynamic performance.

[0067] Carbon materials A first embodiment of the present invention provides a carbon material comprising a pore structure, wherein the peak pattern of the X-ray diffraction pattern of the carbon material has two diffraction peaks in the range where 2θ is between 25.5° and 27.5°.

[0068] Figure 1 shows the peak pattern of the X-ray diffraction pattern of one embodiment of the carbon material of this application. As can be seen from Figure 1, the diffraction pattern can be divided into two peaks within the range where 2θ is 25.5° to 27.5° (corresponding to the diffraction peak of the carbon 002 crystal plane). In the course of research, the inventors of this application discovered that when a carbon material contains a pore structure and the peak pattern of the X-ray diffraction pattern of the carbon material has two diffraction peaks within the range where 2θ is 25.5° to 27.5°, a secondary battery can be made to have good cycle performance and dynamic performance. Possible causes include at least the following:

[0069] If the peak pattern of the X-ray diffraction pattern of a carbon material shows two diffraction peaks within the range of 2θ 25.5° to 27.5°, then the carbon material contains both highly graphitized crystalline carbon components (e.g., crystalline carbon with a graphitization degree of ≥95%) and less graphitized crystalline carbon components (e.g., crystalline carbon with a graphitization degree of 70%-90%). The less graphitized crystalline carbon components may have large interlayer spacing, which is advantageous for the diffusion of active ions, allowing the secondary battery to have good dynamic performance. The highly graphitized crystalline carbon components, on the one hand, can give the carbon material a high gram capacity and / or compaction density, thereby increasing the energy density of the secondary battery. On the other hand, they can give the carbon material a stable structure, resulting in low irreversible consumption of active ions during the secondary battery cycle, thus allowing the secondary battery to have good cycle performance.

[0070] The carbon material described in this application includes a pore structure. In this application, "the carbon material includes a pore structure" means that the carbon material has a pore structure that can be directly observed from a cross-sectional image (for example, a scanning electron microscope image at a magnification of 1000x), i.e., 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 expansion space necessary for volume changes of the carbon material particles, thereby reducing the risk of new interfaces being created by the fragmentation of the carbon material particles, further reducing the occurrence of side reactions, and improving the cycle performance of secondary batteries.

[0071] As a result, the carbon material described in this application can be used in secondary batteries that possess both good cycle performance and dynamic performance.

[0072] If the carbon material does not have a porous structure, the volume change of the carbon material particles is large during the charging and discharging of the secondary battery. This increases the risk of new interfaces being created due to the fragmentation of the carbon material particles, leading to many side reactions inside the secondary battery, and furthermore, both the cycle performance and dynamic performance of the secondary battery are poor.

[0073] If the X-ray diffraction pattern of a carbon material shows only one diffraction peak within the range of 2θ to 27.5°, then the carbon material mainly consists of a microstructure of the same crystalline phase, meaning the carbon material contains only highly graphitized or low-graphitized crystalline carbon. If the carbon material contains only low-graphitized crystalline carbon, the gram capacity and / or compaction density of the carbon material is low, resulting in a low energy density of the secondary battery. If the carbon material contains only highly graphitized crystalline carbon, the interlayer spacing of the carbon material is small, which is unfavorable for the diffusion of active ions, and furthermore, the kinetic performance of the secondary battery is poor, making it impossible to achieve both good cycle performance and kinetic performance in the secondary battery.

[0074] In some embodiments, of the two diffraction peaks, the one with a smaller 2θ is designated as the first peak, and the one with a larger 2θ is designated as the second peak. 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 12:88 to 35:65, 15:85 to 35:65, or 15:85 to 30:70.

[0075] In further research, the inventors discovered 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 combine better cycle performance and dynamic performance while also having 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 carbon material contains a large amount of crystalline carbon components with a high degree of graphitization, but a small amount of crystalline carbon components with a low degree of graphitization. This further stabilizes the structure of the carbon material and reduces the irreversible consumption of active ions during the secondary battery cycle, thereby giving the secondary battery even higher cycle performance and simultaneously enabling it to have a high energy density.

[0077] Furthermore, the following situations can be effectively avoided. If the ratio of the peak intensity of the first peak to the peak intensity of the second peak is small, there are few low-graphitization crystalline carbon components in the carbon material, which may affect the diffusion of active ions and further affect the effect of improving the dynamic performance of the secondary battery. If the ratio of the peak intensity of the first peak to the peak intensity of the second peak is large, there are too many low-graphitization crystalline carbon components in the carbon material, which may result in high side reaction activity on the surface of the carbon material particles, leading to 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, if there are many low-graphitization crystalline carbon components in the carbon material, the gram capacity and / or compaction density of the carbon material will decrease further, 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 this 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 patterns of the X-ray diffraction patterns of carbon materials are obtained by refining the X-ray diffraction patterns of carbon materials using the Rietveld full pattern fitting refinement method with Topas software. The 2θ range is 25.5° to 27.5°, corresponding to the peak positions 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 integral area of ​​the first peak to the integral area of ​​the second peak.

[0081] In some embodiments, the carbon material has one or more pore areas of 0.1 μm². 2 The pore structure includes the above-mentioned features, and optionally one or more pores have a pore area of ​​0.15 μm². 2 ~3.0μm 2The invention includes a pore structure. In further research, the inventors discovered that when a carbon material includes a pore structure having the above-mentioned pore area, the pore structure can reserve expansion space necessary for volume changes of carbon material particles, thereby further reducing the risk of new interfaces being formed by the fragmentation of carbon material particles, further reducing the occurrence of side reactions, reducing irreversible capacity loss of secondary batteries, and improving the cycle performance of secondary batteries.

[0082] In some embodiments, the carbon material includes an outer region and an inner region located inside the outer region, wherein the outer region is defined as a region extending 0.25 L from the particle surface of the carbon material into the particle interior, where L is the length of the minor axis of the carbon material particle, S1 is the total pore area of ​​the outer region, S2 is the total pore area of ​​the inner region, 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 using cross-sectional images 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. The "particle center" refers to the area within a radius of 0.1 μm from the geometric center of the particle toward the particle surface.

[0085] In this application, the length of the minor axis of a particle refers to the minimum value at which a 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 center of the particle 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 extending from the surface of the particle of the carbon material 100 to the interior of the particle by a distance of 0.25L is the outer region 101, and the region inside the outer region 101 is the inner region 102.

[0087] A cross-section of the carbon material may be prepared using a cross-sectional polishing machine (for example, the IB-09010 CP type argon ion cross-sectional polishing machine from JEOL Japan), and the cross-section of the carbon material may be scanned using a scanning electron microscope (for example, the Sigma 300 type scanning electron microscope from ZEISS Germany) in reference to JY / T010-1996, and finally the total pore area S1 of the outer region and the total pore area S2 of the inner region of the carbon material may be calculated using image processing software (for example, AVIZO).

[0088] In further research, the inventors discovered that if the carbon material further satisfies S2 > S1, the carbon material may have the characteristics of having a high pore content and / or large pore size in the internal region and a low pore content and / or small pore size in the external region. A high pore content and / or large pore size in the internal region of the carbon material particles allows the pore structure to reserve the expansion space necessary for volume changes of the carbon material particles, thereby reducing the risk of new interfaces being created by the crushing of the carbon material particles, further reducing the occurrence of side reactions, reducing irreversible capacity loss of the secondary battery, and improving the cycle performance and dynamic performance of the secondary battery. A low pore content and / or small pore size in the external region of the carbon material particles gives the carbon material particles a more stable structure, prevents the electrolyte from seeping into the pore structure inside the carbon material particles as much as possible, thereby reducing the occurrence of side reactions, reducing the consumption of active ions due to the formation of SEI films inside the particles, further increasing the initial Coulomb efficiency of the carbon material, and further improving the cycle performance of the secondary battery.

[0089] Therefore, if the carbon material further satisfies S2 > S1, it can effectively reduce irreversible capacity loss in secondary batteries, improve the capacity performance characteristics of secondary batteries, and better combine high initial Coulomb efficiency, high energy density, and good cycle performance and dynamic performance in secondary batteries.

[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. In further research, the inventors discovered that if S2 / S1 is also within the above range, the secondary battery can better combine high initial Coulomb efficiency, high energy density, and good cycle performance and dynamic performance.

[0091] In some examples, 0.01 μm 2 ≤S1 ≤ 8.0 μm 2 Therefore, 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 Therefore, if 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 SEI films inside the carbon material particles, and on the other hand, it does not affect the transport performance of active ions and electrons.

[0092] In some examples, 2.5 μm 2 ≤S2 ≤ 25.0 μm 2 Therefore, 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 It is 6.0 μm 2 ≤S2 ≤ 15 μm 2Therefore, if the total pore area of ​​the internal region of the carbon material is within the above range, on the one hand, it is possible to reserve a sufficiently stable expansion space for volume changes of carbon material particles, reduce the risk of new interfaces being formed due to the fragmentation of carbon material particles, reduce the occurrence of side reactions on the surface of new interfaces, and reduce the consumption of active ions due to the formation of SEI films on the surface of new interfaces, and on the other hand, it is also possible to improve the capacity and initial Coulomb efficiency of the carbon material.

[0093] In some examples, 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, and 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 μm². 2 The following applies, and optionally 0.1 μm 2 The inventors have further discovered 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 given to the external region of the carbon material, thereby effectively increasing the structural stability of the carbon material, preventing the electrolyte from seeping into the pore structure inside the carbon material particles as much as possible, and further effectively improving the cycle performance of the secondary battery. Of course, this application assumes that the area of ​​all pore structures in the external region of the carbon material is all 0.2 μm. 2 It is not intended to restrict the area to the following, for example, a pore structure area of ​​95% or more, or optionally 99% or more, of 0.2 μm². 2 Below, 0.1 μm is used as an optional choice. 2 You may also control it so that it is as follows:

[0095] In some embodiments, one or more areas of 0.1 μm are present in the internal region of the carbon material. 2 The pore structure includes the above-mentioned features, and optionally, one or more areas are 0.15 μm². 2 ~3.0μm 2The invention includes a pore structure. Further research has shown that by incorporating a pore structure of the above size into the internal region of the carbon material, it is possible to reserve a sufficiently stable expansion space for volume changes of the carbon material particles and reduce the risk of the carbon material particles breaking, and on the other hand, it is also possible to improve the compaction density of the carbon material and improve the energy density of the secondary battery.

[0096] In some embodiments, the X-ray diffraction pattern of the carbon material does not show a diffraction peak of the 3R phase C(012) crystal plane. The 3R (Rhombohedral) phase refers to rhombohedral crystalline carbon having an ABCABC… deposition structure. The absence of a diffraction peak of the 3R phase C(012) crystal plane in the carbon material of this application means that the carbon material particles 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 shapes. This is advantageous for increasing the compaction 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, and optionally, the proportion of primary particles in the carbon material is ≥50%, for example, 55%~95%, 60%~100%, 65%~90%, 65%~80%, 70%~100%, 75%~90%, 80%~100%, 90%~100%, or 95%~100%. The carbon material includes an appropriate proportion of primary particles, thereby providing it with high structural stability, reducing the occurrence of side reactions, and increasing the compaction density of the negative electrode plate, thereby improving the energy density of the secondary battery.

[0099] In some embodiments, the carbon material may consist entirely of primary particles, meaning that the proportion of primary particles in the carbon material is 100%.

[0100] The terms primary and secondary particles are both known in this field. Primary particles refer to particles in a non-aggregated state. Secondary particles refer to particles in an aggregated state, formed by the aggregation of two or more primary particles. Primary and secondary particles can be distinguished by scanning electron microscope (SEM) images.

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

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

[0103] The degree of graphitization of carbon materials is known in this art and can be tested using instruments and methods known in this art. For example, it may be tested using an X-ray diffractometer (e.g., Bruker D8 Discover), and in the test, the average interlayer spacing d of the (002) crystal plane in the crystalline structure of the carbon material may be determined with reference to JIS K 0131-1996 and JB / T 4220-2011. 002 We obtain the following equation: g = (0.344 - d 002 The degree of graphitization can be calculated according to ) / (0.344-0.3354)×100%. In the above formula, d 002 This is the average interlayer spacing of the (002) crystal plane in the crystalline structure of a carbon material, expressed in nanometers (nm).

[0104] In some embodiments, the specific surface area of ​​the carbon material is 0.5 m². 2 / g~3.1m 2 / g, and optionally 0.7m 2 / g~2.8m 2 The value is / g. The carbon material of this application has a low specific surface area, which reduces the consumption of active ions during SEI film formation and improves the initial Coulomb efficiency of the carbon material.

[0105] The specific surface area of ​​carbon materials has a meaning known in this art and can be measured using instruments and methods known in this art. For example, it can be tested using the nitrogen gas adsorption specific surface area analysis test method, referring to GB / T 19587-2017, and calculated using the BET (Brunauer Emmett Teller) method, where the nitrogen gas adsorption specific surface area analysis test can be performed using the Tri-Star 3020 specific surface area pore size analyzer from Micromeritics, Inc., USA.

[0106] In some examples, 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 falls within the above range, it is advantageous for improving the transmission performance of active ions and electrons, thereby further enhancing the cycle performance and dynamic performance of secondary batteries.

[0108] In some embodiments, the (Dv90-Dv10) / Dv50 of the carbon material is ≤1.55 and optionally between 0.5 and 1.50. When the (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, and is also advantageous to form a rational pore structure between the particles of the negative electrode film layer, thereby improving the cycle performance and / or dynamic performance of the secondary battery.

[0109] The volume distribution particle sizes Dv10, Dv50, and Dv90 of carbon materials have meanings known in this art, representing the particle sizes corresponding to when the cumulative volume distribution percentage of the material reaches 10%, 50%, and 90%, respectively, and can be measured using instruments and methods known in this art. For example, they can be easily measured using a laser particle size analyzer, referring to the GB / T 19077-2016 laser diffraction particle size distribution method. The test instrument may be a Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., 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 improving electron transmission performance, thereby further enhancing the cycle performance and dynamic performance of the secondary battery.

[0111] The powder resistivity of carbon materials is a known concept in the art and can be measured using instruments and methods known in the art. For example, referring to GB / T 30835-2014, it can be measured using the four-probe method with a powder resistivity tester (e.g., Suzhou Crystal ST2722, Sansi Vertical UTM7305). An exemplary test method is as follows: A certain amount of test-ready sample powder is weighed and placed in a dedicated mold, and the powder resistivity at different pressures can be obtained by setting the test pressure. In this application, the test pressure may be set to 8 MPa.

[0112] In some examples, the compaction density of the carbon material at a pressure of 20,000 N was 1.70 g / cm³. 3 ~1.95g / cm 3 Therefore, it is optionally 1.72 g / cm³. 3 ~1.92g / cm 3 That is the case.

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

[0114] In this application, the compaction density of carbon material powder is defined in the sense known in the art and can be measured using instruments and methods known in the art. For example, it may be measured using an electronic pressure tester (e.g., a UTM7305 electronic pressure tester) with reference to GB / T 24533-2009. An exemplary test method is as follows: Weigh 1 g of carbon material powder and measure the compaction density of a carbon material powder with a base area of ​​1.327 cm². 2 In addition to the mold, the material is pressurized to 2000 kg (equivalent to 20000 N), held for 30 seconds, then released, maintained for 10 seconds, and the powder consolidation density of the carbon material at a pressure of 20000 N is recorded and calculated.

[0115] In some examples, the tap density of the carbon material is 0.90 g / cm³. 3 ~1.35g / cm 3 Therefore, optionally 0.95 g / cm³ 3 ~1.32 g / cm³ 3 Therefore, if the tap density of the carbon material is within the above range, the compaction density of the negative electrode plate can be increased, further improving the energy density of the secondary battery, which is advantageous in enhancing the active ion and electron transmission performance, and improving the cycle performance and dynamic performance of the secondary battery.

[0116] The tap density of carbon materials is a known concept in this art and can be measured using instruments and methods known in this art. For example, it can be measured using a powder tap density tester, referring to GB / T 5162-2006. The Dandong Baite BT-301 may be used as the test instrument.

[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 carbon materials is known in this art and can be tested using methods known in this art. An example test method is as follows: A carbon material sample, styrene-butadiene rubber (SBR) adhesive, sodium carboxymethylcellulose (CMC) thickener, and carbon black conductive agent are thoroughly mixed in an appropriate amount of deionized water in a mass ratio of 96.2:1.8:1.2:0.8 to form a uniform negative electrode slurry. This slurry is then uniformly coated onto the surface of the copper foil of the negative electrode current collector and dried in an oven to prepare it for use. Ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent. LiPF6 is then dissolved in this organic solvent to produce an electrolyte with a concentration of 1 mol / L. Subsequently, a metallic lithium sheet is used as the counter electrode, and a polyethylene (PE) film is used as the separator. The battery is then assembled into a CR2430 type button cell in a glove box protected by argon gas. At 25°C, the button cell battery manufactured as described above is first discharged with a constant current of 0.15 mA to 0.005 V, left to stand for 5 minutes, and then discharged again with a constant current of 10 μA to 0.005 V. The discharge capacity of the button cell battery for the first cycle is recorded. Subsequently, it is charged with a constant current of 0.3 mA to 2.0 V, and the charge capacity of the button cell battery is recorded. The ratio of the charge capacity of the button cell battery to the mass of the carbon material sample is the gram capacity of the carbon material.

[0119] Manufacturing method A second embodiment of the present application provides a method for manufacturing a carbon material that can produce the carbon material of the first embodiment of the present application.

[0120] The method for producing the carbon material includes: step 1 providing a raw material having a plurality of pore structures; step 2 uniformly mixing the raw material and a filler material in a predetermined ratio, then maintaining the mixture at a first temperature T1 for a first time t1 to obtain an intermediate; and step 3 maintaining the obtained intermediate at a second temperature T2 for a second time t2 to obtain a carbon material, wherein the carbon material includes pore structures, and the peak pattern of the X-ray diffraction pattern of the carbon material has two diffraction peaks within the range where 2θ is between 25.5° and 27.5°.

[0121] In some embodiments, the raw materials for producing the carbon material include natural graphite. Optionally, the natural graphite includes one or more of flake graphite, natural spheroidal graphite, and microcrystalline graphite, and further optionally includes natural spheroidal graphite.

[0122] In this application, "natural spheroidal graphite" refers to natural graphite having a spherical or substantially spherical shape, and does not mean that all natural graphite particles are controlled to be ideally spherical. In some embodiments, natural spheroidal graphite of the required particle size and shape can be obtained by pretreatment of flaky graphite, and optionally, the pretreatment includes steps 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 shapes.

[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 processes.

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

[0126] In some examples, the carbon content in the raw material is ≥98 wt%.

[0127] In some embodiments, the softening point temperature of the filler material is 120°C to 300°C, and 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, and 125°C to 160°C.

[0128] In the course of research, the inventors discovered that when the softening point temperature of the filler material is within the above range, it is advantageous to adjust the pore dimensions and / or pore content in the external and internal regions of the carbon material to be within an appropriate range, and 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. This allows for the effective avoidance of the following situations. If the softening point temperature of the filler material is too high, it becomes difficult for the filler material to flow into and fill the pore structure of the raw material. This prevents effective modification of defects inside the particles, and also prevents the electrolyte from seeping into the pore structure inside the resulting carbon material particles. Furthermore, it affects the initial Coulomb efficiency and cycle performance of the secondary battery. If the softening point temperature of the filler material is too low, the filler material contains many small molecules, and these small molecules are easily volatile with heat. Although this makes it easy for the filler material to flow into and fill the pore structure of the raw material, if heat treatment is performed in step 2 and / or step 3, the small molecules in the filler material volatilize, preventing the actual residual carbon in the filled area from effectively filling the pore structure of the raw material. This prevents an effective filling effect, or the actual residual carbon in the filled area has many pores. Furthermore, it prevents the reduction of active ion consumption by forming the SEI film and the reduction of irreversible capacity loss of the secondary battery, while simultaneously affecting the cycle performance, dynamic performance and / or storage performance of the secondary battery.

[0129] In some embodiments, the coking value of the filler material is 25% to 70%, and optionally 30% to 60%. In the course of research, the inventors discovered that when the coking value of the filler material is within the above range, it is advantageous to adjust the pore dimensions and / or pore content in the external and internal regions of the carbon material to be within an appropriate range, and 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 filler material has a meaning known in the art and can be measured using instruments and methods known in the art. For example, it can be measured by referring to GB / T 8727-2008.

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

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

[0133] In some embodiments, the mass ratio of the filler material to the raw material is 10:90 to 25:75, and 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 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. If the mass ratio of the filler material to the raw material is too small, the dispersion uniformity between the filler material and the raw material may be poor. In this case, the filler material cannot effectively modify defects inside the particles, nor can it effectively prevent the electrolyte from seeping into the pore structure inside the resulting carbon material particles, which further affects the initial Coulomb efficiency and cycle performance of the secondary battery. If the mass ratio of the filler 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 dynamic performance of the secondary battery. If the mass ratio of the filler material to the raw material is too large, it tends to cause the pore structure inside the raw material to be completely filled, and in this case, the resulting carbon material When the product change is large, the particles become more easily fragmented, the consumption of active ions due to the formation of the SEI film increases, and the irreversible capacity loss of the secondary battery increases. If the mass ratio of the packing material to the raw material is too large, a large amount of packing material remains on the surface of the particles, at which point the particles become more easily aggregated, not only adding a depolymerization step but also reducing the gram capacity and / or compaction density of the obtained carbon material. If the mass ratio of the packing 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, resulting in a high content of crystalline carbon components with a low degree of graphitization in the obtained carbon material, which affects the energy density and cycle performance of the secondary battery.

[0134] By adjusting one or more parameters such as the type of filler material, softening point, coking value, and amount added to fall within the above range, it is advantageous, on the one hand, to adjust the ratio of the peak intensity of the first peak to the peak intensity of the second peak to fall within an appropriate range, and on the other hand, to adjust the pore size and / or pore content in the external and internal regions of the carbon material to fall within an appropriate range. Furthermore, after the filler material is melted by heat, it is possible to maintain good fluidity without high viscosity and without causing adhesion of raw material particles, thereby reducing aggregation of raw material particles in subsequent manufacturing processes. This reduces problems such as an increase in surface defects in carbon material particles and an increase in active sites for surface side reactions, which would otherwise necessitate the addition of a depolymerization step.

[0135] In some embodiments, in step 2, the first temperature T1 is 1000°C to 1400°C, and optionally 1000°C to 1350°C, 1000°C to 1300°C, 1050°C to 1350°C, 1050°C to 1300°C, or 1050°C to 1250°C. In the course of research, the inventors found that when the first temperature is within the above range, it is advantageous to adjust the pore dimensions and / or pore content in the external and internal regions of the carbon material to be within an appropriate range.

[0136] In some embodiments, the first time t1 is between 1h and 5h. For example, the first time t1 may be a range consisting of 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, or any of the above values. Optionally, the first time t1 is between 2h and 4h. In the course of research, the inventors found that when the first time is within the above range, it is advantageous to adjust the pore dimensions and / or pore content in the external and internal regions of the carbon material to be 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 in the range 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 of the above values. Optionally, the heating rates are 1°C / min to 8°C / min, 1.5°C / min to 6°C / min, 1.5°C / min to 5°C / min, or 1.5°C / min to 4°C / min.

[0138] In the course of research, the inventors discovered 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 and internal regions of the carbon material to be within an appropriate range. This allows for the effective avoidance of the following situations: If the heating rate is too high, the packing material may carbonize on the surface of the raw material particles, making it difficult for the packing material to fill the pore structure of the raw material. This prevents effective modification of defects inside the particles, and also prevents the electrolyte from seeping into the pore structure inside the resulting carbon material particles, further affecting the initial Coulomb efficiency and cycle performance of the secondary battery. If the heating rate is too low, the packing material easily flows and fills all the pore structures of the raw material, leading to large volume changes in the carbon material during the release and storage of active ions, and making the particles more prone to fragmentation. This increases the consumption of active ions due to the formation of the SEI film, increasing irreversible capacity loss in the secondary battery, while also affecting the cycle performance and dynamic performance of the secondary battery.

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

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

[0141] In step 2, adjusting one or more of the heating rate, first temperature, first time, etc., so that they are within the above range is advantageous for manufacturing and obtaining a carbon material of the required structure, for example, so that the pore dimensions and / or pore content in the external and internal regions of the carbon material are within an appropriate range.

[0142] In some embodiments, the second temperature T2 is 2000°C to 2720°C, and may be a range consisting of, for example, 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 any of the above values. 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, or 2150°C to 2400°C.

[0143] In the course of their research, the inventors discovered that when the second temperature is within the above range, it is possible to have two diffraction peaks in the peak pattern of the X-ray diffraction pattern of the carbon material, where 2θ is in the range of 25.5° to 27.5°, and that this is 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. This allows for the effective avoidance of the following situations. If 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 resulting carbon material contains a large amount of low-graphitization components and / or amorphous carbon (e.g., soft carbon), which increases the defect content of the carbon material and affects the initial Coulomb efficiency, gram capacity, and cycle performance of the carbon material. If 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 of 2θ = 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, which is unfavorable for the rapid release and intercalation of active ions, thereby affecting the dynamic performance of the secondary battery.

[0144] In some embodiments, the second time t2 is between 1.5h and 6h. For example, the second time t2 may be a range consisting of 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, or any of the above values. Optionally, the second time t2 is between 2h and 5h.

[0145] In the course of research, the inventors discovered that when the second temperature is within the above range, it is possible to have two diffraction peaks in the peak pattern of the X-ray diffraction pattern of the carbon material within the range where 2θ is between 25.5° and 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. This allows for the effective avoidance of the following situations: If 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. If the second time is too long, there are no two diffraction peaks in the peak pattern of the X-ray diffraction pattern of the carbon material within the range where 2θ is between 25.5° and 27.5°, or the ratio of the peak intensity of the first peak to the peak intensity of the second peak is small, which is unfavorable for the rapid release and storage of active ions, thereby affecting the dynamic performance of the secondary battery.

[0146] In some embodiments, in step 3, the heat treatment can be carried out in a medium-frequency furnace, a box-type graphitizing furnace, an Acheson graphitizing furnace, a continuous graphitizing furnace, or an intra-serial graphitizing furnace.

[0147] In some embodiments, in step 3, the heat treatment atmosphere for the medium-frequency furnace and continuous graphitization may be a shielding gas atmosphere. The shielding 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 second time to fall within the above range, it is possible to ensure that the peak pattern of the X-ray diffraction pattern of the carbon material has two diffraction peaks within the range where 2θ is between 25.5° and 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 fall within an appropriate range.

[0149] The method for manufacturing carbon materials described in this application is simple, highly safe, does not require pre-setting pressure or vacuum treatment, and does not require an additional depolymerization step during heat treatment. The carbon material manufactured in this application exhibits small volume expansion, high structural stability, and a fast diffusion rate of active ions. Furthermore, it can combine high gram capacity, high initial Coulomb efficiency, and small volume change, and can provide secondary batteries with good cycle performance and kinetic performance. In addition, the secondary batteries can also combine high initial Coulomb efficiency and high energy density.

[0150] The manufacturing method described in this application is low-cost, highly practical, and suitable for large-scale production.

[0151] secondary battery A third aspect of the embodiments of this application provides a secondary battery.

[0152] This application does not particularly limit the type of secondary battery; for example, the secondary battery may be a lithium-ion battery. A secondary battery generally includes a positive electrode plate, a negative electrode plate, and an electrolyte. During the charging and discharging process of the secondary battery, active ions are intercepted and released by reciprocating between the positive electrode plate and the negative electrode plate, and the electrolyte plays a role in conducting the active ions between the positive electrode plate and the negative electrode plate. This application does not particularly limit the type of electrolyte, and it 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., electrolyte solution). In secondary batteries employing an electrolyte solution, and in some secondary batteries employing a solid electrolyte, a separator may be further included, which is placed between the positive electrode plate and the negative electrode plate and serves to isolate them.

[0153] [negative electrode plate] In some embodiments, the negative electrode plate includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector. For example, the negative electrode current collector has two opposing surfaces in its thickness direction, and the negative electrode film layer is provided 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 according to the first embodiment of this application or a carbon material manufactured by the method described in the second embodiment of this application. This allows the secondary battery to have both good cycle performance and dynamic performance.

[0155] In some embodiments, the negative electrode film layer may further contain other negative electrode active materials other than the carbon material described above. 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, silicone-based materials, tin-based materials, and lithium titanate. The silicone-based material may include one or more of elemental silicone, silicone oxide, silicone-carbon composite, silicone-nitrogen composite, and silicone alloy materials. The tin-based material may include one or more of elemental tin, tin oxide, and tin alloy materials.

[0156] In some embodiments, the negative electrode film layer optionally further comprises a negative electrode conductive agent. The application does not particularly limit the type of negative electrode conductive agent, and 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 comprises a negative electrode adhesive. The application does not particularly limit the type of negative electrode adhesive, and as an example, the negative electrode adhesive may comprise one or more of the following: styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic resin (e.g., polyacrylate PAA, polymethacrylate 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 comprises other additives. For example, the other additives may include thickeners such as sodium carboxymethylcellulose (CMC), PTC thermistor material, etc.

[0159] In some embodiments, the negative electrode current collector may be a metal foil sheet or a composite current collector. Copper foil may be used as an example of a metal foil sheet. The composite current collector may include a polymer material substrate and a metal material layer formed on at least one surface of the polymer material substrate. For example, the metal material may include one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys. For example, the polymer material substrate may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyester (PS), and polyethylene (PE).

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

[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 this application further includes a conductive undercoating (e.g., consisting 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, and in some embodiments, the negative electrode plate described in this application further includes a protective layer covering the surface of the negative electrode film layer.

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

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

[0164] The positive electrode film layer generally comprises 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, followed by drying and cold pressing. The positive electrode slurry is generally formed by dispersing the positive electrode active material, an optional conductive agent, an optional adhesive, and any other components in a solvent and stirring uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP). As an example, the adhesive used for the positive electrode film layer may include one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin. For example, the conductive agent used in the positive electrode film layer includes one or more of the following: superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0165] The positive electrode active material may be a positive electrode active material for secondary batteries that is well known in this field.

[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 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 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 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 solvent is not specifically limited and can be selected according to actual needs. In some embodiments, the solvent may include, for example, one or more of the following: 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 optionally further comprises additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve some performance of the secondary battery, such as additives that improve the overcharge performance of the secondary battery, additives that improve the high-temperature performance of the secondary battery, and additives that improve the low-temperature power performance of the secondary battery.

[0175] [Separator] This application is not particularly limited to the type of separator, and any known porous separator having good chemical and mechanical stability may be selected.

[0176] In some embodiments, the material of the separator may include one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film. When the separator is a multilayer 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 manufactured into an electrode assembly by a winding process or a lamination process.

[0178] In some embodiments, the secondary battery may include an outer casing. This outer casing may be used to package the electrode assembly and electrolyte.

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

[0180] This application does not particularly limit the shape of the secondary battery, which may be cylindrical, rectangular, or any other shape. Figure 3 shows a rectangular secondary battery 5 as an example.

[0181] In some embodiments, as shown in Figure 4, the casing 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 side plates surround and form a housing cavity. The case 51 has an opening that communicates with the housing cavity, and the cover plate 53 is provided to cover the opening and close the housing cavity. The positive electrode plate, the negative electrode plate and the separator can be formed into an electrode assembly 52 by a winding process or a lamination process. The electrode assembly 52 is packaged in the housing cavity. The electrolyte permeates 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 the demand.

[0182] The method for manufacturing a secondary battery described in this application is known. In some embodiments, a secondary battery can be formed by assembling a positive electrode plate, a separator, a negative electrode plate, and an electrolyte. For example, the positive electrode plate, separator, and negative electrode plate can be formed into an electrode assembly by a winding process or a lamination process, the electrode assembly can be placed in an outer casing, dried, and then the electrolyte can be injected. A secondary battery can then be obtained through processes such as vacuum packaging, settling, chemical formation, and shaping.

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

[0184] Figure 5 is a schematic diagram of an example battery module 4. As shown in Figure 5, in the battery module 4, the multiple secondary batteries 5 may be arranged sequentially along the length of the battery module 4. Of course, they may be arranged according to any other method. Furthermore, the multiple secondary batteries 5 may be fixed with fasteners.

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

[0186] In some embodiments, the battery modules may be further 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] Figures 6 and 7 are schematic diagrams of an example battery pack 1. As shown in Figures 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 covering the lower housing 3 and forming a sealed space for housing the battery modules 4. The plurality of battery modules 4 may be arranged inside the battery box in any manner.

[0188] power consumption equipment This application further provides a power consumption device comprising at least one of the secondary battery, battery module, or battery pack of this application. The secondary battery, battery module, or battery pack may be used as a power source for the power consumption device or as an energy storage unit for the power consumption device. The power consumption device may be, but is not limited to, mobile devices (e.g., mobile phones, tablet computers, laptop computers, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

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

[0190] Figure 8 is a schematic diagram of an example power consumption device. This power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of this power consumption device, a battery pack or battery module can be used.

[0191] Other examples of power-consuming devices may include mobile phones, tablet computers, and laptop computers. These power-consuming devices generally require lightweight designs, and can utilize rechargeable batteries as their power source.

[0192] Examples The following examples provide a more detailed description of the contents disclosed in this application, and these examples are provided solely for illustrative purposes. It will be obvious to those skilled in the art that various modifications and changes can be made within the scope of the contents disclosed in this application. Unless otherwise noted, all parts, percentages, and ratios reported in the following examples are by mass, all reagents used in the examples are commercially available or can be synthesized by common methods and can be used directly without further processing, and all equipment used in the examples is commercially available.

[0193] Example 1 (1) Manufacturing of carbon materials Step 1: 100-mesh flake graphite is subjected to mechanical grinding, classification, spheroidization, and purification to obtain natural spheroidal graphite. Its volume distribution particle size Dv50 is 15 μm, its carbon content is 99.9%, and its degree of graphitization is 95%.

[0194] Step 2: The obtained natural spheroidal 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 in a mass ratio of 80:20 for 30 minutes. The mixed material was then placed in a crucible and heated in a box furnace at a rate of 2°C / min to 1100°C, and maintained at that temperature for 2 hours. After completion, it was allowed to cool naturally to room temperature to obtain the intermediate.

[0195] Step 3: The obtained intermediate was placed in an Acheson graphitization furnace, heated to 2400°C and maintained at that temperature for 3 hours, and after completion, demagnetized and sieved to obtain the carbon material.

[0196] (2) Manufacturing of button-type batteries (half-cell batteries) 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 in preparation 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 electrolyte 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 cell) 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 used as a separator, and it was arranged in order with the manufactured positive electrode plate and negative electrode plate. The separator was positioned between the positive electrode plate and the negative electrode plate to provide isolation. Then, it was wound up to obtain an electrode assembly. The electrode assembly was placed in an outer casing, dried, and then the same electrolyte as that used for manufacturing button batteries was injected. After going through processes such as vacuum packaging, settling, chemical conversion, and capacitation, a secondary battery was obtained.

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

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

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

[0203] 100-mesh flake graphite was mechanically crushed, classified, spheroidized, and purified to obtain natural spheroidal graphite. Its volume distribution particle size Dv50 was 15 μm, its carbon content was 99.9%, and its graphitization degree was 95%. The obtained natural spheroidal 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 mass ratio of 80:20 in a VC mixer for 30 minutes. The mixed material was then graphitized at 3200°C for 10 hours, and after completion, it was cooled to room temperature to obtain carbon material.

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

[0205] 100-mesh flake graphite was mechanically crushed, classified, spheroidized, and purified to obtain natural spheroidal graphite. Its volume distribution particle size Dv50 was 15 μm, its carbon content was 99.9%, and its graphitization degree was 95%. The obtained natural spheroidal 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 mass ratio of 80:20 in a VC mixer for 30 minutes. The mixed material was then carbonized at 1200°C for 3 hours, and after completion, it was cooled to room temperature to obtain carbon material.

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

[0207] Mechanical grinding, classification, spheroidization, and purification treatment were performed on 100-mesh flake graphite to obtain natural spheroidal graphite. Its volume distribution particle size Dv50 was 15 μm, its carbon element content was 99.9%, and its degree of graphitization was 95%.

[0208] The obtained natural spheroidal 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 minutes. Subsequently, the mixed materials were placed in a reaction vessel, and a method was adopted in which the reaction vessel was gradually heated up, with a heating rate of 2°C / min. While heating, the reaction vessel was kept in a constant stirring state, and the temperature was raised to 190°C, the pressure of the reaction vessel was reduced to -0.1 MPa, and it was kept warm for 2 hours. After the warming period, the temperature of the reaction vessel was raised to 650°C and kept warm for 2 hours, and then the temperature of the reaction vessel was reduced to approximately 160°C. Then, petroleum asphalt was gradually added to the reaction vessel, with a mass ratio of the amount of petroleum asphalt added this time to the amount of petroleum asphalt added last time being 1:1. After that, the temperature of the reaction vessel was raised again to 190°C, the pressure of the reaction vessel was reduced to -0.1 MPa, and it was kept warm for 2 hours, and after the warming period, the temperature of the reaction vessel was raised to 650°C and kept warm for 2 hours, and then the temperature was cooled using the condensation cooling method. Finally, the material processed in the above process was heat-treated at 1200°C for 3 hours. After heat treatment, the sample was crushed and sieved to obtain a carbon material without internal pores.

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

[0210] [Table 1]

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

[0212] In Table 2, 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°. 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. A Bruker D8 Discover X-ray diffractometer may be used as the test instrument. In the X-ray diffraction analysis test, the test conditions may be as follows: A sample is prepared using a flat plate sample preparation method for carbon material, a copper target is used as the anode target, CuKα rays are used as the radiation source, the voltage is 40KV, the current is 40mA, the anti-scattering slit is 1mm, the scanning 2θ angle range is 20° to 80°, the step size is 0.01671°, the time length of each step is 0.24s, and the scanning speed is 4° / min.

[0213] (2) Testing of total pore area in the external and internal regions of carbon materials After uniformly mixing the sample and carbon material powder using an adhesive, the mixture is applied to copper foil and dried at 60°C for 30 minutes to prepare it for use. The sample is then cut into 6mm x 6mm pieces and attached to the sample stage of a CP-type argon ion cross-section polishing machine. The sample is then 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 also be the IB-09010 CP-type argon ion cross-section polishing machine from JEOL Japan.

[0214] Cross-sections of carbon materials were scanned using a scanning electron microscope. This can be tested by referring to JY / T010-1996. The test equipment may also be a Sigma 300 scanning electron microscope from ZEISS, Germany.

[0215] The region extending 0.25 L from the particle surface to the interior of the carbon material is defined as the outer region, and the region inside the outer region is defined as the inner region, where L represents the length of the short axis of the carbon material particle. The total pore area S1 of the outer region and the total pore area S2 of the inner region of the carbon material were calculated using image processing software. The image processing software may be AVIZO.

[0216] (3) Test of the maximum charge rate of secondary batteries At 25°C, the secondary battery was discharged at a constant current at a 1C rate until it reached the lower cutoff voltage (corresponding to 0% SOC). Then, it was charged at a constant current at a 1C rate until it reached the upper cutoff voltage (corresponding to 100% SOC), followed by constant voltage charging down to 0.05C, at which point the secondary battery was fully charged. After letting the fully charged secondary battery stand for 5 minutes, it was discharged at a constant current at a 1C rate until it reached the lower cutoff voltage (corresponding to 0% SOC). The discharge capacity at this point was the actual capacity of the secondary battery at a 1C rate and was denoted as C0. The secondary battery was then charged at a constant current at an x ​​C0 rate (representing a gradient charging rate, for example, 1 C0, 1.05 C0, 1.1 C0, 1.15 C0, 1.2 C0, etc.) until it reached the upper cutoff voltage (corresponding to 100% SOC), followed by constant voltage charging down to 0.05 C0, and left to stand for 5 minutes. The secondary battery was then disassembled, and the lithium deposition status on the surface of the negative electrode plate was observed. If lithium was not deposited on the surface of the negative electrode plate, the charging rate was increased and the test was repeated until lithium was deposited on the surface of the negative electrode plate. The maximum charging rate at which lithium was not deposited on the surface of the negative electrode plate was recorded.

[0217] (4) Cycle performance test of secondary batteries At 25°C, the manufactured secondary battery was charged with a constant current of 1C to the upper cutoff voltage (corresponding to 100% SOC), then charged with a constant voltage of 0.05C, left to stand for 5 minutes, and then discharged with a constant current of 1C to the lower cutoff voltage (corresponding to 0% SOC). The discharge capacity at this time was recorded and defined as the discharge capacity of the first cycle. A cycle charge-discharge test was performed on the secondary battery using the above method, and the discharge capacity after each cycle was recorded. The capacity retention rate (%) of the secondary battery after 2500 cycles at 25°C is calculated as: discharge capacity after 2500 cycles / discharge capacity of the first cycle × 100%.

[0218] [Table 2]

[0219] 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 the X-ray diffraction patterns of the carbon materials do not show diffraction peaks of the 3R phase C(012) crystal plane.

[0220] As can be seen from the test results in Table 2, if the peak pattern of the X-ray diffraction pattern of the carbon material satisfies the condition that there are two diffraction peaks within the range of 2θ = 25.5° to 27.5°, then the battery can be made to have good cycle performance and dynamic performance. Furthermore, if 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, then the battery can be made to have even better cycle performance and dynamic performance, and can also be made to have a high energy density.

[0221] As can be seen from the test results in Table 2, the overall performance of the battery is further improved when the carbon material particles further satisfy S2>S1, optionally satisfy 1.5≦S2 / S1≦450, and optionally satisfy 2≦S2 / S1≦400. In this case, the carbon material particles further have the characteristics of having a large pore content and / or large pore size in the internal region and a small pore content and / or small pore size in the external region. The pore structure in the internal region of the carbon material can reserve the expansion space necessary for volume changes of the carbon material particles, thereby reducing the risk of new interfaces being created by the crushing of the carbon material particles, further reducing the occurrence of side reactions, and reducing irreversible capacity loss of the battery. The small pore content and / or small pore size in the external region of the carbon material gives the carbon material particles a more stable structure, and prevents the electrolyte from seeping 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 SEI films inside the particles. This means that carbon materials that further satisfy the above structural characteristics can further enhance the overall performance of batteries.

[0222] In the X-ray diffraction peak patterns of the carbon materials manufactured in Comparative Examples 1 to 4, there was only one diffraction peak within the range of 2θ = 25.5° to 27.5°, and none of them could provide batteries with both good cycle performance and kinetic performance.

[0223] In Comparative Example 1, untreated natural spheroidal graphite was used as the carbon material. The carbon material particles had many pores inside, and the X-ray diffraction pattern of the carbon material showed only one diffraction peak within the range of 2θ = 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 using this material were both poor.

[0224] The carbon material produced in Comparative Example 2 has a carbon layer coating formed on the surface of natural spheroidal graphite. Due to the high heat treatment temperature and long heat treatment time, the degree of graphitization of the carbon layer is close to that of the natural spheroidal 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 in the range where 2θ is between 25.5° and 27.5°, and the interlayer spacing of the carbon material at this time is small. As can be seen from the test results in Table 2, the kinetic performance of the battery produced as a result is poor. Furthermore, the coating layer exists only on the surface of the natural spheroidal graphite, so an effective filling effect is not achieved, and the seepage of the electrolyte into the pore structure inside the particles cannot be effectively prevented, resulting in a limited improvement in the battery's cycle performance.

[0225] The carbon material produced in Comparative Example 3 has a carbon layer coating formed on the surface of natural spheroidal graphite. Due to the low heat treatment temperature, the main component of the coating layer is amorphous carbon, and no crystalline carbon phases with different degrees of graphitization appear in the carbon material. Furthermore, in the peak pattern of the X-ray diffraction pattern of the carbon material, there is only one diffraction peak within the range of 2θ from 25.5° to 27.5°. Moreover, the coating layer exists only on the surface of the natural spheroidal graphite, so an effective filling effect is not achieved, and the seepage of the electrolyte into the pore structure inside the particles cannot be effectively prevented, resulting in a limited improvement in the battery's cycle performance and dynamic performance.

[0226] In Comparative Example 4, when manufacturing the carbon material, the packing material is filled into all the pore structures inside the natural spheroidal graphite particles using a vacuum method. Because the heat treatment temperature is low, a large amount of amorphous carbon is present inside and / or on the surface of the carbon material particles, and no crystalline carbon phases with different degrees of graphitization appear in the carbon material. In the X-ray diffraction pattern of the carbon material, there is only one diffraction peak within the range of 2θ from 25.5° to 27.5°. Furthermore, in this case, there is no pore structure inside the obtained carbon material particles. This leads to a large volume change in the carbon material during the release and storage of active ions, making the particles prone to fragmentation, and also limits the improvement in the battery's cycle performance and dynamic performance.

[0227] It should be noted that this application is not limited to the embodiments described above. The embodiments described above are illustrative, and any embodiment that has substantially the same configuration as the technical idea and produces the same effects within the scope of the technical proposal of this application is included within the scope of the technical proposal of this application. Furthermore, other forms constructed by combining some of the components of the embodiments, with various modifications that a person skilled in the art could conceive of, are also included within the scope of this application, as long as they do not depart from the spirit of this application.

[0228] In drawings, the drawings are not necessarily drawn to scale. The symbols are explained 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 area, 102 Internal area.

Claims

1. A carbon material comprising a pore structure, wherein the peak pattern of the X-ray diffraction pattern of the carbon material with CuKα radiation as the emission source has two diffraction peaks within the range where 2θ is 25.5° to 27.5°. The carbon material comprises an outer region and an inner region located inside the outer region, wherein the outer region refers to a region extending 0.25 L from the particle surface of the carbon material into the particle interior, where L is the length of the minor axis of the carbon material particle, the total pore area of ​​the outer region is S1, the total pore area of ​​the inner region is S2, and 1.5 ≤ S2 / S1 ≤ 450.

2. The carbon material according to claim 1, wherein of the two diffraction peaks, the one with a small 2θ is designated as the first peak, the one with a large 2θ is designated 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.

3. The carbon material has one or more pores with an area of ​​0.1 μm ２ The carbon material according to claim 1, comprising the above-mentioned pore structure.

4. 2≦S ２ / S １ The carbon material according to claim 1, wherein the coefficient of carbon is ≤ 400.

5. 0.01 μm ２ ≤S １ ≤8.0 μm ２ and / or, 2.5 μm ２ ≤ S ２ ≤ 25.0 μm ２ and / or The carbon material according to claim 1, wherein L ≥ 4 μm.

6. The area of ​​the pore structure in the external region of the carbon material is 0.2 μm². ２ The following and / or, Within the internal region of the carbon material, one or more areas are 0.1 μm ２ The carbon material according to claim 1, comprising the above-mentioned pore structure.

7. The carbon material is (1) The specific surface area of ​​the carbon material is 0.5 m² ２ / g to 3.1m ２ The fact that it is / g, (2) The volume distribution particle size Dv50 of the carbon material is 8.0 μm to 23.0 μm, (3) The (Dv90 - Dv10) / Dv50 of the carbon material is ≤ 1.55, (4) The carbon material according to claim 1, wherein the form of the carbon material includes one or more of block-shaped, spherical, and substantially spherical shapes.

8. The aforementioned carbon material is (1) The powder resistivity of the carbon material at a pressure of 8 MPa is 0.006 Ω. cm to 0.051 Ω. cm, (2) The powder compaction density of the carbon material at a pressure of 20,000 N is 1.70 g / cm³. ３ ~1.95 g / cm ３ That is, (3) The tap density of the carbon material is 0.90 g / cm³ ３ ~1.35 g / cm ３ That is, (4) The gram capacity of the carbon material is 350 mAh / g to 372 mAh / g, (5) The degree of graphitization of the carbon material is 91.5% to 98.5%, (6) The carbon material according to claim 1, wherein the X-ray diffraction pattern of the carbon material does not have diffraction peaks of the 3R phase C(012) crystal plane.

9. A method for manufacturing a carbon material, comprising: step 1 manufacturing a raw material having a plurality of pore structures; and uniformly mixing the raw material and a filler material according to a predetermined ratio, and then heating to a first temperature T １ Then the first time t １ Step 2 involves maintaining the temperature only to obtain an intermediate, and then heating the obtained intermediate to a second temperature T ２ Then the second time t ２ The process includes step 3, which involves keeping the material warm and obtaining a carbon material. The mass ratio of the filling material to the raw material is 10:90 to 25:

75. The first temperature T1 is 1000°C to 1400°C. The first time t1 is between 1h and 5h, The second temperature T2 is between 2000°C and 2720°C. The second time t2 is between 1.5h and 6h. Here, the carbon material includes a pore structure, and in the peak pattern of the X-ray diffraction pattern of the carbon material with CuKα radiation as the emission source, there are two diffraction peaks within the range where 2θ is 25.5° to 27.5°. The carbon material comprises an outer region and an inner region located inside the outer region, wherein the outer region refers to a region extending 0.25 L from the particle surface of the carbon material into the particle interior, where L is the length of the minor axis of the carbon material particle, the total pore area of ​​the outer region is S1, the total pore area of ​​the inner region is S2, and 1.5 ≤ S2 / S1 ≤ 450. A method for manufacturing carbon materials.

10. The aforementioned raw materials are (1) The raw material contains natural graphite, (2) The volume distribution particle size Dv50 of the raw material is 7.5 μm to 23.0 μm, (3) The degree of graphitization of the raw material is ≥ 93.0%, The method according to claim 9, wherein at least one of the following is satisfied: (4) the carbon element content in the raw material is ≥ 98 wt%.

11. The aforementioned filling material is (1) The softening point temperature of the filler material is 120°C to 300°C, (2) The caulking value of the filler material is 25% to 70%, (3) The volume distribution particle size Dv50 of the filling material is 6 μm or less, (4) The method according to claim 9, wherein the filler material contains at least one of the following: coal-based asphalt, petroleum-based asphalt, resin, and polymer material.

12. The method according to claim 9, wherein the mass ratio of the filling material to the raw material is 12:88 to 25:

75.

13. The first temperature T １ The temperature range is 1050°C to 1250°C, and / or The first time t １ is 2h to 4h, and / or, The second temperature T ２ The temperature range is 2150°C to 2550°C, and / or The second time t ２ The method according to claim 9, wherein the duration is 2 to 5 hours.

14. The first temperature T is increased at a rate of 1°C / min to 10°C / min. １ The method according to claim 9, wherein the temperature is raised to a certain level.

15. A secondary battery comprising a negative electrode plate, wherein the negative electrode plate comprises a carbon material according to any one of claims 1 to 8.

16. A power consumption device including the secondary battery described in claim 15.

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